24.08.2017
Modeling and control of hydraulic drive systems

Project focus

• Mathematical modeling of hydraulic systems, in particular of axial piston pumps
• Adaptive nonlinear control of axial piston pumps
• Optimal model-predictive control strategies for axial piston pumps
• Application to a hydraulic hybrid drive train

Description

Hydraulic drive systems are widely spread in many industrial applications. This results from their high power density while featuring a small size and weight. The control of hydraulic systems is typically performed by means of valves, which allow to reach very fast dynamics of the closed loop system. However, utilizing valves to control hydraulic systems also incorporates relatively large energy losses.

To increase the energy efficiency, variable displacement pumps and motors are considered in this research project. In particular, axial piston pumps with swash plates are considered, which allow for a continuous and fast change of the volume flow by tilting the swash plate, cf. Fig. 1. Optimal control strategies for the swash plate angle are developed in a research cooperation with Robert Bosch GmbH, which are the basis for a control of the volume flow, the pressure or the torque of the machine.

One challenge for the design of control strategies for axial piston pumps are the pronounced nonlinear behavior of the system and fast changing external loads. A nonlinear adaptive control strategy, including an estimation strategy for the unknown load, was developed for axial piston pumps with fast changing loads. Furthermore, nonlinear model-predictive control strategies are developed to allow for a systematic incorporation of the nonlinearities and constraints of the system. The internal, non-measurable states, which are necessary in the control strategies, are obtained by a nonlinear estimation strategy. It has already been shown that it is possible to implement such a nonlinear model-predictive control strategy in real-time with a sampling time of 1 ms on an industrial real-time hardware.

Based on the optimal control of the swash plate angle, extended control strategies e.g. for the rotational speed of the axial piston machine are developed. A possible application, which was considered in a research cooperation with Robert Bosch GmbH, is a hydraulic hybrid drive train, see Fig. 3. This system comprises an internal combustion engine and a hydraulic drive train with two axial piston machines (APU). To regenerate brake energy, oil can be stored in a hydraulic piston accumulator. In this research project, mathematical models for the system and estimation strategies for the state of charge of the piston accumulator were developed. Moreover, an optimal (model-predictive) control strategy was proposed for certain configurations of the drive train, which allow to accurately follow the driver’s demand while minimizing the energy losses at the same time.

Selected publications

• P. Zeman, W. Kemmetmüller, and A. Kugi, Nonlinear Model Predictive Control of Axial Piston Pumps, Journal of Dynamic Systems, Measurement, and Control, vol. 139, iss. 8, p. 081008-1–081008-11, 2017.
  [BibTex]

  @Article{Zeman17,
  Title = {Nonlinear Model Predictive Control of Axial Piston Pumps},
  Author = {Zeman, P. and Kemmetm\"uller, W. and Kugi, A.},
  Journal = {Journal of Dynamic Systems, Measurement, and Control},
  Pages = {081008-1--081008-11},
  Volume = {139},
  Year = {2017},
  Number = {8},
  Doi = {10.1115/1.4035608},
  ISSN = {0022-0434},
  }

• P. Zeman, W. Kemmetmüller, and A. Kugi, Energy-efficient Constrained Control of a Hydrostatic Power Split Drive, in Proceedings of the 20th IFAC World Congress, Toulouse, France, 2017, p. 4775–4780.
  [BibTex]

  @InProceedings{Zeman17a,
  author = {Zeman, P. and Kemmetm\"uller, W. and Kugi, A.},
  title = {Energy-efficient Constrained Control of a Hydrostatic Power Split Drive},
  booktitle = {Proceedings of the 20th IFAC World Congress},
  year = {2017},
  volume = {50},
  number = {1},
  month = {7},
  pages = {4775--4780},
  doi = {10.1016/j.ifacol.2017.08.959},
  address = {Toulouse, France},
  issn = {2405-8963},
  }

• A. Pfeffer, T. Glück, W. Kemmetmüller, and A. Kugi, Mathematical modelling of a hydraulic accumulator for hydraulic hybrid drives, Mathematical and Computer Modelling of Dynamical Systems, vol. 22, iss. 5, p. 397–411, 2016.
  [BibTex] [Download]

  @Article{Pfeffer16,
  Title = {Mathematical modelling of a hydraulic accumulator for hydraulic hybrid drives},
  Author = {Pfeffer, A. and Gl\"uck, T. and Kemmetm\"uller, Wolfgang and Kugi, Andreas},
  Journal = {Mathematical and Computer Modelling of Dynamical Systems},
  Pages = {397--411},
  Volume = {22},
  Year = {2016},
  Number = {5},
  Doi = {10.1080/13873954.2016.1174716},
  ISSN = {1387-3954},
  }

• P. Zeman, W. Kemmetmüller, and A. Kugi, Model Predictive Speed Control of Axial Piston Motors, in Proceedings of the 10th IFAC Symposium on Nonlinear Control Systems (NOLCOS 2016), Monterey, USA, 2016, p. 772–777.
  [BibTex]

  @InProceedings{Zeman16,
  author = {Zeman, P. and Kemmetm\"uller, W. and Kugi, A.},
  title = {Model Predictive Speed Control of Axial Piston Motors},
  booktitle = {Proceedings of the 10th IFAC Symposium on Nonlinear Control Systems (NOLCOS 2016)},
  year = {2016},
  volume = {49},
  number = {18},
  month = {8},
  pages = {772--777},
  doi = {10.1016/j.ifacol.2016.10.259},
  address = {Monterey, USA},
  issn = {2405-8963},
  }

• A. Pfeffer, T. Glück, W. Kemmetmüller, and A. Kugi, State of Charge Estimator Design for a Hydro-Pneumatic Accumulator, Journal of Dynamic Systems, Measurement, and Control, vol. 137, iss. 6, p. 061014:1–061014:9, 2015.
  [BibTex]

  @Article{Pfeffer15,
  Title = {State of Charge Estimator Design for a Hydro-Pneumatic Accumulator},
  Author = {Pfeffer, A. and Gl\"uck, T. and Kemmetm\"uller, W. and Kugi, A.},
  Journal = {Journal of Dynamic Systems, Measurement, and Control},
  Pages = {061014:1--061014:9},
  Volume = {137},
  Year = {2015},
  Number = {6},
  Doi = {10.1115/1.4029407},
  }

• P. Zeman, W. Kemmetmüller, and A. Kugi, Mathematical Modeling and Analysis of a Hydrostatic Drive Train, in Proceedings of the 8th Vienna International Conference on Mathematical Modelling (MATHMOD), Vienna, Austria, 2015, p. 508–513.
  [BibTex]

  @InProceedings{Zeman15,
  author = {Zeman, P. and Kemmetm\"uller, W. and Kugi, A.},
  title = {Mathematical Modeling and Analysis of a Hydrostatic Drive Train},
  booktitle = {Proceedings of the 8th Vienna International Conference on Mathematical Modelling (MATHMOD)},
  year = {2015},
  month = {2},
  pages = {508--513},
  doi = {10.1016/j.ifacol.2015.05.064},
  address = {Vienna, Austria},
  }

• W. Kemmetmüller, F. Fuchshumer, and A. Kugi, Nonlinear pressure control of self-supplied variable displacement axial piston pumps, Control Engineering Practice, vol. 18, p. 84–93, 2010.
  [BibTex] [Download]

  @Article{Kemmetmuller10,
  Title = {Nonlinear pressure control of self-supplied variable displacement axial piston pumps},
  Author = {W. Kemmetm{\"u}ller and F. Fuchshumer and A. Kugi},
  Journal = {Control Engineering Practice},
  Pages = {84--93},
  Volume = {18},
  Year = {2010},
  Doi = {10.1016/j.conengprac.2009.09.006},
  }

Project partner

• Robert Bosch GmbH

  23.08.2017
Control of pumped storage power plants

Project focus

• Development of efficient models to describe the flow in long pipelines
• Development of scalable, physics-based digital twins of pumped storage power plants
• Design of optimal (model-predictive) control strategies
• Analysis of the possibilities to estimate non-measureable quantities

Description

Due to the increased implementation of renewable energy production (wind energy, solar plant), the amount of power plants with strongly fluctuating power production has significantly increased in the European electric grid. Thus, suitable storage systems are necessary to guarantee the stability of the electric grid. The most common way to store energy is given by pumped storage power plants, which basically comprise two water tanks which are connect by a pipeline and a turbine, cf. Fig. 1. In cases of excessive electric power in the electric distribution grid, water is pumped from the lower tank to the upper tank. Contrary, power can be supplied to the grid by transporting water from the upper tank via the turbine to the lower tank.



Typical setup of a pumped storage power plant

In this research project in cooperation with Andritz Hydro, control strategies for the optimal dynamical operation of pumped storage power plants are developed. Fixed speed (synchronous machine) and variable speed (doubly-fed induction machine or synchronous machine with a full-rated converter) plants are considered. A typical setup of a pumped storage power plant which utilizes doubly-fed induction machines (DFIM) is depicted in Fig. 2.



Components of a variable speed pumped storage power plant

A main difficulty for the dynamic control of pumped storage power plants are the long pipelines (in the range of up to several kilometers), which connect the turbines with the tanks. For fast changes of the turbine operation, this results in pressure waves (water hammer) which distribute along the pipelines and can result in a severe load (up to a damage) of the pipelines. Fig. 3 depicts a typical distribution of the pressure and volume flow at a pipeline for fast changes in the turbine operation point.



Spatial and time distribution of the pressure and volume flow in a pipeline

To take into account these effects, approximations of the infinite-dimensional equations describing this effect are developed. A focus is laid on methods, which allow for a very high numeric efficiency. This is important in particular for the utilization of the models in model based control strategies. Based on these models, optimal control strategies (model-predictive control) are examined. Based on these models and models of the electrical system, a scalable, physics based digital twin (including sensors and actuators) is developed. The physics based digital twin allows for easy adaptation to different topologies of pumped storage power plants (number of pipelines, types of turbines and generators, different elements in the electrical system, …). The digital twin is used for examination of optimal control strategies (model-predictive control). The main goal is to increase the dynamics of the closed-loop system (and thus the potential for the stabilization of grid variations) while keeping or increasing the energy efficiency of the power plant. Optimal open-loop control of high dynamic transients (e.g. load rejection) is also investigated.

Another focus of the project lies in the optimal power plant dispatching. One aspect is the optimal economic power plant utilization with day-ahead optimizations and control of short-time overloads in order to generate additional income during intraday trading in high volatile power grids. Another aspect is the power plant operation under minimal wear in order to extend the power plant lifespan.

Selected publications

• J. -F. Mennemann, L. Marko, J. Schmidt, W. Kemmetmüller, and A. Kugi, The spectral element method as an efficient tool for transient simulations of hydraulic systems, Applied Mathematical Modelling, vol. 54, p. 627–647, 2018.
  [BibTex] [Download]

  @Article{Mennemann2018,
  author = {Mennemann, J.-F. and Marko, L. and Schmidt, J. and Kemmetm{\"u}ller, W. and Kugi, A.},
  title = {{The spectral element method as an efficient tool for transient simulations of hydraulic systems}},
  doi = {10.1016/j.apm.2017.10.010},
  issn = {0307-904X},
  pages = {627--647},
  volume = {54},
  journal = {Applied Mathematical Modelling},
  year = {2018},
  }

• J. Schmidt, W. Kemmetmüller, and A. Kugi, Modeling and static optimization of a variable speed pumped storage power plant, Renewable Energy, vol. 111, p. 38–51, 2017.
  [BibTex] [Download]

  @Article{Schmidt17,
  Title = {Modeling and static optimization of a variable speed pumped storage power plant},
  Author = {Schmidt, J. and Kemmetm\"uller, W. and Kugi, A.},
  Journal = {Renewable Energy},
  Pages = {38--51},
  Volume = {111},
  Year = {2017},
  Doi = {10.1016/j.renene.2017.03.055},
  ISSN = {0960-1481},
  }

• J. -F. Mennemann, J. Schmidt, W. Kemmetmüller, and A. Kugi, Simulation von Welleneffekten in Pumpspeicherkraftwerken mit Hilfe der Spektral-Element-Methode, at – Automatisierungstechnik, vol. 64, iss. 8, p. 681–695, 2016.
  [BibTex]

  @Article{Mennemann16,
  Title = {{Simulation von Welleneffekten in Pumpspeicherkraftwerken mit Hilfe der Spektral-Element-Methode}},
  Author = {Mennemann, J.-F. and Schmidt, J. and Kemmetm{\"u}ller, W. and Kugi, A.},
  Journal = {at -- Automatisierungstechnik},
  Pages = {681--695},
  Volume = {64},
  Year = {2016},
  Number = {8},
  Doi = {10.1515/auto-2016-0061},
  ISSN = {0178-2312},
  }

• J. Mennemann, J. Schmidt, W. Kemmetmüller, and A. Kugi, Anwendung der Spectral-Penalty-Methode zur effizienten Diskretisierung der Massen- und Impulsbilanzgleichungen in Rohrleitungssystemen von Pumpspeicherkraftwerken, in Tagungsband GMA-Fachausschuss 1.30 “Modellbildung, Identifikation und Simulation in der Automatisierungstechnik”, Anif/Salzburg, Austria, 2015, p. 56–95.
  [BibTex]

  @InProceedings{Mennemann15,
  author = {Mennemann, Jan-Frederik and Schmidt, J. and Kemmetm\"uller, W. and Kugi, A.},
  title = {{Anwendung der Spectral-Penalty-Methode zur effizienten Diskretisierung der Massen- und Impulsbilanzgleichungen in Rohrleitungssystemen von Pumpspeicherkraftwerken}},
  booktitle = {Tagungsband GMA-Fachausschuss 1.30 "Modellbildung, Identifikation und Simulation in der Automatisierungstechnik"},
  year = {2015},
  month = {9},
  isbn = {978-3-9815012-9-2},
  pages = {56--95},
  address = {Anif/Salzburg, Austria},
  }

• J. Schmidt, W. Kemmetmüller, and A. Kugi, Modellierung und Analyse eines Pumpspeicherkraftwerks mit drehzahlvariablem Generator, in Tagungsband GMA-Fachausschuss 1.30 “Modellbildung, Identifikation und Simulation in der Automatisierungstechnik”, Anif/Salzburg, Austria, 2014, p. 38–68.
  [BibTex]

  @InProceedings{Schmidt14,
  author = {Schmidt, J. and Kemmetm\"uller, W. and Kugi, A.},
  title = {Modellierung und {A}nalyse eines {P}umpspeicherkraftwerks mit drehzahlvariablem {G}enerator},
  booktitle = {Tagungsband GMA-Fachausschuss 1.30 "Modellbildung, Identifikation und Simulation in der Automatisierungstechnik"},
  year = {2014},
  month = {9},
  pages = {38--68},
  address = {Anif/Salzburg, Austria},
  }

• L. Marko, J. -F. Mennemann, L. Jadachowski, W. Kemmetmüller, and A. Kugi, Early- and late-lumping observer designs for long hydraulic pipelines: Application to pumped-storage power plants, Int. Journal of Robust and Nonlinear Control, vol. 28, iss. 7, p. 2759–2779, 2018.
  [BibTex]

  @Article{Marko2018,
  author = {Marko, L. and Mennemann, J.-F. and Jadachowski, L. and Kemmetm{\"u}ller, W. and Kugi, A.},
  title = {{Early- and late-lumping observer designs for long hydraulic pipelines: Application to pumped-storage power plants}},
  doi = {10.1002/rnc.4049},
  issn = {1099-1239},
  number = {7},
  pages = {2759--2779},
  volume = {28},
  journal = {Int. Journal of Robust and Nonlinear Control},
  year = {2018},
  }

Project partners and funding

• Andritz Hydro

  22.08.2017
Electrorheological fluids

Project focus

• Continuum-mechanical modeling of electrorheological fluids
• Development and control of electrorheological valves
• Design, modeling and control of semi-active electrorheological suspension systems
• Implementation and test on test benches and in test vehicles

Description

Classical hydraulics utilizes valves to change the volume flow in a hydraulic system. The basic operational principle is the adjustment of the flow path by means of the motion of a mechanical part, e.g. the valve spool. In contrast, electrorheological fluids (ERF) allow to directly influence their rheological properties (i.e. the apparent viscosity) by applying a sufficiently large electric field. This, in turn, allows to change the volume flow in a hydraulic circuit without any mechanical motion. Since the electrorheological effect is very fast (in the range of a few milliseconds), ERF can be utilized to build very fast hydraulic actuators. Furthermore, the resulting construction is kept very simple since there are no complicated mechanically moving parts.

In this research project, several applications in the field of valve constructions, linear actuators and automotive suspension systems, and shock absorbers in maritime applications were considered. The basis for all results was a detailed mathematical modeling of the ERF by means of a continuum mechanical model, which describes the stress as a function of the electric field strength and the shear rate. The characteristics of the shear stress as a function of shear rate is depicted in Fig. 1 for a typical ERF.



Shear stress as a function of the shear rate for a typical ERF

The core part of most electrorheological components is an ER valve, which basically features two (parallel) electrodes, where the ERF is flowing in between, see Fig. 2. By applying an electric voltage to the electrodes, the flow resistance of the valve can be increased. If the electric voltage is chosen large enough, the valve can be even closed completely.



Basic setup of an ER valve

The dynamics of this change of the flow of the ERF is, as already mentioned, very fast. Fig. 3 depicts the characteristics of the fluid velocity \(u_1\) of the ERF in the valve (depicted in Fig. 2) for changes in the voltage and the pressure, respectively.



Change of the fluid velocity in an ER valve for changes in voltage and the pressure, respectively

A possible field of application of ERF and ER-valves are automotive suspension systems. Adjustable dampers are utilized in semi-active suspension systems to obtain a good trade-off between driving comfort and driving stability. This can be obtained by adjusting the damping according to the actual road conditions. Fig. 4 depicts a semi-active electrorheological damper for truck applications which was developed in a cooperation with Fludicon. In this research cooperation, mathematical models and control strategies for vehicles equipped with this semi-active suspension systems were derived. It could be shown by means of test drives that a significant improvement of driving comfort and stability can be obtained in comparison to a vehicle, which utilize a classical passive suspension system.



Cross-sectional view of an ER-damper

The possibility to directly influence the characteristics of an ERF by means of an electric field enables to control the flow of ERFs by means of a suitable shaping of the electrodes. A possible application are digital electrorheological valves, which were developed in a further cooperation with Fludicon. The basic idea is to change the flow resistance by means of switching on and off a number of serially connected ER valves. This allows to utilize cheap high voltage power supplies with constant voltage. Utilizing e.g. a binary coding of the length of the electrodes, very small step sizes of the flow resistance can be obtained by a rather small number of serially connected valves, cf. Fig. 5. Possible applications are again semi-active automotive suspension systems.



Serial digital ER valve with the resulting characteristics

For the test of the characteristics of the ERF and the ER valves, a test bench was set up. Utilizing transparent electrodes, this test bench also allows to directly monitor the flow of the ERF in the valve and thus to draw conclusions on the flow patterns, see Fig. 6-



ER test stand and the electrodes of a digital ER valve

The subsequent videos show measurement results obtained on this test bench. The first video shows the digital ER valve depicted in Fig. 6, and the change of the flow through this valve due to the activation of the different parts of the valve. A possibility to actively control the flow of the ERF is studied in the videos 2 and 3. Here, a sinusoidal flow path is generated by suitable electrode shapes, which allow to block parts of the flow path by applying an electric voltage. The results of this experiment could be utilized to build an ER valve in matrix setup, which allows a freely configurable connection of several in- and outputs without any mechanical components.

Selected publications

• W. Kemmetmüller, K. Holzmann, A. Kugi, and M. Stork, Electrorheological Semiactive Shock Isolation Platform for Naval Applications, IEEE/ASME Transactions on Mechatronics, vol. 18, iss. 5, p. 1437–1447, 2013.
  [BibTex] [Download]

  @Article{Kemmetmuller13a,
  Title = {{{E}lectrorheological {S}emiactive {S}hock {I}solation {P}latform for {N}aval {A}pplications}},
  Author = {W. Kemmetm{\"u}ller and K. Holzmann and A. Kugi and M. Stork},
  Journal = {IEEE/ASME Transactions on Mechatronics},
  Pages = {1437--1447},
  Volume = {18},
  Year = {2013},
  Number = {5},
  Doi = {10.1109/TMECH.2012.2203456},
  }

• M. Kamelreiter, W. Kemmetmüller, and A. Kugi, Digitally controlled electrorheological valves and their application in vehicle dampers, Mechatronics, vol. 22, iss. 5, p. 629–638, 2012.
  [BibTex] [Download]

  @Article{Kamelreiter12,
  Title = {{Digitally controlled electrorheological valves and their application in vehicle dampers}},
  Author = {M. Kamelreiter and W. Kemmetm\"uller and A. Kugi},
  Journal = {Mechatronics},
  Pages = {629--638},
  Volume = {22},
  Year = {2012},
  Number = {5},
  Doi = {10.1016/j.mechatronics.2012.02.002},
  }

• M. Kamelreiter, W. Kemmetmüller, and A. Kugi, Digitale Ansteuerung elektrorheologischer Ventile und deren Anwendung in einem Fahrzeugdämpfer, in Tagungsband Mechatronik 2011 Dresden, Dresden, Germany, 2011, p. 37–42.
  [BibTex]

  @InProceedings{Kamelreiter11,
  author = {M. Kamelreiter and W. Kemmetm\"uller and A. Kugi},
  title = {{D}igitale {A}nsteuerung elektrorheologischer {V}entile und deren {A}nwendung in einem {F}ahrzeugd\"ampfer},
  booktitle = {Tagungsband Mechatronik 2011 Dresden},
  year = {2011},
  month = {3},
  pages = {37--42},
  address = {Dresden, Germany},
  }

• M. Kamelreiter, W. Kemmetmüller, and A. Kugi, Digital Control of Electrorheological Valves, in Proceedings of the 5th IFAC Symposium on Mechatronic Systems, Boston, USA, 2010, p. 640–645.
  [BibTex] [Download]

  @InProceedings{Kamelreiter10,
  author = {M. Kamelreiter and W. Kemmetm{\"u}ller and A. Kugi},
  title = {Digital Control of Electrorheological Valves},
  booktitle = {Proceedings of the 5th IFAC Symposium on Mechatronic Systems},
  year = {2010},
  month = {9},
  pages = {640--645},
  doi = {10.3182/20100913-3-US-2015.00075},
  address = {Boston, USA},
  }

• K. Holzmann, W. Kemmetmüller, A. Kugi, M. Stork, H. Rosenfeldt, and S. Schneider, Modeling and control of an off-road truck using electrorheological dampers, Journal of Physics: Conference Series, vol. 149, 012011, 2009.
  [BibTex] [Download]

  @Article{Holzmann09,
  Title = {Modeling and control of an off-road truck using electrorheological dampers},
  Author = {K. Holzmann and W. Kemmetm{\"u}ller and A. Kugi and M. Stork and H. Rosenfeldt and S. Schneider},
  Journal = {Journal of Physics: Conference Series},
  Volume = {149, 012011},
  Year = {2009},
  Doi = {10.1088/1742-6596/149/1/012011},
  }

• M. Kamelreiter, W. Kemmetmüller, A. Kugi, K. Holzmann, and M. Stork, Modellierung und Regelung eines Kleintransporters mit semi-aktiver Radaufhängung basierend auf elektrorheo-logischen Dämpfern, in Mechatronik 2009, Wiesloch, Germany, 2009, p. 413–420.
  [BibTex]

  @InProceedings{Kamelreiter09,
  author = {M. Kamelreiter and W. Kemmetm{\"u}ller and A. Kugi and K. Holzmann and M. Stork},
  title = {Modellierung und {R}egelung eines {K}leintransporters mit semi-aktiver {R}adaufh{\"a}ngung basierend auf elektrorheo-logischen {D}{\"a}mpfern},
  booktitle = {Mechatronik 2009},
  year = {2009},
  month = {5},
  pages = {413--420},
  address = {Wiesloch, Germany},
  }

• K. Holzmann, W. Kemmetmüller, A. Kugi, M. Stork, H. Rosenfeldt, and S. Schneider, Modeling and control of an off-road truck using electrorheological dampers, in Proceedings 11th Conference on Electrorheological Fluids and Magnetorheological Suspensions, Dresden, Germany, 2008.
  [BibTex]

  @InProceedings{Holzmann08,
  author = {K. Holzmann and W. Kemmetm{\"u}ller and A. Kugi and M. Stork and H. Rosenfeldt and S. Schneider},
  title = {Modeling and control of an off-road truck using electrorheological dampers},
  booktitle = {Proceedings 11th Conference on Electrorheological Fluids and Magnetorheological Suspensions},
  year = {2008},
  month = {8},
  doi = {10.1088/1742-6596/149/1/012011},
  address = {Dresden, Germany},
  }

Project partner

• Fludicon GmbH

  16.08.2017
Active camera stabilization platform

Project focus

• Optimization of the setup (actuators, sensors) of a camera stabilization platform
• Attitude estimation strategy utilizing redundant inertial measurement units
• Design of a nonlinear attitude control strategy
• Implementation and test on a camera stabilization platform prototype

Description

In many movie scenes or video clips, the camera is dynamically moved to change the perspective or to make a more engaging film. Typically, camera cranes, steadycams, cable cams, or helicopter cameras are used in the production of such video sequences. To avoid distracting changes of the line of sight induced by movements of the mobile carrier vehicle, the camera is inertially stabilized. For this task, inertially stabilized platforms (ISPs) with gimbaled assemblies are widely used.

In this project, a new active camera stabilization platform developed by qinematiq was considered. It features a gimbal with three degrees of freedom which is actuated by electric motors in each joint. The orientation of the camera and the handle with respect to the inertial frame is measured utilizing inertial measurement units (IMUs), see Fig. 1.



Experimental setup of the camera stabilization platform

The main control task is to control the camera orientation according to a desired orientation which is defined by the camera operator. For this task, a nonlinear flatness-based control strategy was developed, which is based on the estimation of the camera orientation and the orientation of the handle of the platform. In order to obtain these orientations from the measurements of the IMU, a multiplicative extended Kalman filter (MEKF) was developed, which fuses the signals of all sensors of the platform. As an essential step to reach the desired accuracy of the platform, the design and the choice of actuators and sensors of the platform were of immanent importance. The practical feasibility of the overall estimation and control strategy was proven by experiments on a prototype platform.

Selected publications

• F. Königseder, W. Kemmetmüller, and A. Kugi, Attitude Estimation Using Redundant Inertial Measurement Units for the Control of a Camera Stabilization Platform, IEEE Transactions on Control Systems Technology, vol. 24, iss. 5, p. 1837–1844, 2016.
  [BibTex] [Download]

  @Article{Koenigseder16,
  Title = {Attitude Estimation Using Redundant Inertial Measurement Units for the Control of a Camera Stabilization Platform},
  Author = {K{\"o}nigseder, F. and Kemmetm{\"u}ller, W. and Kugi, A.},
  Journal = {IEEE Transactions on Control Systems Technology},
  Pages = {1837--1844},
  Volume = {24},
  Year = {2016},
  Number = {5},
  Doi = {10.1109/TCST.2015.2510324},
  ISSN = {1063-6536},
  }

• F. Königseder, W. Kemmetmüller, and A. Kugi, Modellierung und Regelung einer tragbaren Kamerastabilisierungsplattform, in Tagungsband Mechatronik 2013, Aachen, Germany, 2013, p. 99–104.
  [BibTex]

  @InProceedings{Konigseder13,
  author = {F. K{\"o}nigseder and W. Kemmetm{\"u}ller and A. Kugi},
  title = {{{M}odellierung und {R}egelung einer tragbaren {K}amerastabilisierungsplattform}},
  booktitle = {Tagungsband Mechatronik 2013},
  year = {2013},
  month = {3},
  pages = {99--104},
  address = {Aachen, Germany},
  }

Project partners and funding

• qinematiq
• Austrian Research Promotion Agency

  16.08.2017
Mobile DRT VLF test system

Project focus

• Modeling, model verification and system analysis
• Observer and estimator design for the online and offline estimation of the cable capacity
• Design of a real-time capable control strategy
• Optimization of system parameters
• Implementation and test of the control and estimation strategies at a prototype

Description

In recent years, an increased assembly of regenerative energy source, as, e.g., wind farms (on- and off-shore), photovoltaics and biomass, can be observed. These power plants are typically connected to the distribution network by means of high voltage cables (HV, UHV) with voltages up to 500 kV. To test their functionality and to detect failures, suitable test systems for the on-site test of the cables are required.

Due to the high capacity of the considered high voltage cables, a test with grid frequency (50 Hz) would imply very high reactive power. This directly results in large and bulky test systems. To reduce the amount of reactive power and thus the size of the test systems, cables are frequently tested with very low frequencies (VLF, approx. 0,01 Hz to 10 Hz).



Prototype of the VLF test system designed by mohaupt high voltage

In this project, a prototype of a VLF test system designed by mohaupt high voltage was considered, see Fig. 1. Figure 2 depicts the schematic setup of the test system. It comprises a power module, which drives a series resonance circuit. The resulting amplitude modulated high voltage is demodulated by the demodulator to obtain the desired low frequency high voltage test signal.



Sketch of the DRT VLF test system

In this project, a detailed mathematical model was developed which incorporates the main nonlinear behavior, in particular of the demodulator. Based on an analysis of the model, a reduced envelope model was developed, which was the basis for the subsequent observer and controller design. The control strategy was designed to minimize the losses of the system and to maximize the quality of the test voltage (minimize the THD value). The control strategy was extended by an estimation strategy for the unknown load (i.e. the cable). Finally, it was shown how to optimally choose the parameters of the system in order to increase the control accuracy of the system. The feasibility and robustness of the control and estimation strategy was proven by means of experiments on the prototype.



Setup for the tests of the control and estimation strategy

Selected publications

• S. Eberharter, W. Kemmetmüller, and A. Kugi, Analysis and System Optimization of a Very Low Frequency High-Voltage Test System, in Proceedings of the 7th IFAC Symposium on Mechatronic Systems & 15th Mechatronics Forum International Conference, Loughborough, UK, 2016, p. 294–300.
  [BibTex]

  @InProceedings{Eberharter16a,
  author = {Eberharter, S. and Kemmetm\"uller, W. and Kugi, A.},
  title = {Analysis and System Optimization of a Very Low Frequency High-Voltage Test System},
  booktitle = {Proceedings of the 7th IFAC Symposium on Mechatronic Systems \& 15th Mechatronics Forum International Conference},
  year = {2016},
  volume = {49},
  number = {21},
  month = {9},
  pages = {294--300},
  doi = {10.1016/j.ifacol.2016.10.570},
  address = {Loughborough, UK},
  issn = {2405-8963},
  }

• W. Kemmetmüller, S. Eberharter, and A. Kugi, Controller design and experimental validation of a very low frequency high-voltage test system, Control Engineering Practice, vol. 37, p. 32–42, 2015.
  [BibTex] [Download]

  @Article{Kemmetmueller15,
  Title = {Controller design and experimental validation of a very low frequency high-voltage test system},
  Author = {Kemmetm\"uller, W. and Eberharter, S. and Kugi, A.},
  Journal = {Control Engineering Practice},
  Pages = {32--42},
  Volume = {37},
  Year = {2015},
  Doi = {10.1016/j.conengprac.2014.12.011},
  }

• S. Eberharter, W. Kemmetmüller, and A. Kugi, Mathematical Modeling and Analysis of a Very Low Frequency HV Test System, IEEE Transactions on Power Electronics, vol. 29, iss. 11, p. 5784–5794, 2014.
  [BibTex] [Download]

  @Article{Eberharter14,
  Title = {Mathematical Modeling and Analysis of a Very Low Frequency {HV} Test System},
  Author = {Eberharter, S. and Kemmetm\"uller, W. and Kugi, A.},
  Journal = {IEEE Transactions on Power Electronics},
  Pages = {5784--5794},
  Volume = {29},
  Year = {2014},
  Number = {11},
  Doi = {10.1109/TPEL.2014.2299293},
  }

• W. Kemmetmüller, S. Eberharter, and A. Kugi, Quasi Optimal Feedforward Control of a Very Low Frequency High Voltage Test System, in Proceedings of the 19th IFAC World Congress, Cape Town, South Africa, 2014, p. 11623–11628.
  [BibTex]

  @InProceedings{Kemmetmueller14a,
  author = {Kemmetm\"uller, W. and Eberharter, S. and Kugi, A.},
  title = {Quasi Optimal Feedforward Control of a Very Low Frequency High Voltage Test System},
  booktitle = {Proceedings of the 19th IFAC World Congress},
  year = {2014},
  month = {8},
  pages = {11623--11628},
  doi = {10.3182/20140824-6-ZA-1003.00356},
  address = {Cape Town, South Africa},
  }

• W. Kemmetmüller and A. Kugi, Mathematische Modellierung und Analyse eines DRT-VLF-Hochspannungsprüfgenerators, e & i Elektrotechnik und Informationstechnik, vol. 129, iss. 1, p. 18–27, 2012.
  [BibTex] [Download]

  @Article{Kemmetmuller12,
  Title = {{Mathematische Modellierung und Analyse eines DRT-VLF-Hochspannungspr\"ufgenerators}},
  Author = {W. Kemmetm\"uller and A. Kugi},
  Journal = {e {\&} i Elektrotechnik und Informationstechnik},
  Pages = {18--27},
  Volume = {129},
  Year = {2012},
  Number = {1},
  Doi = {10.1007/s00502-012-0073-5},
  }

Project partners and funding

• mohaupt high voltage
• Austrian Research Promotion Agency FFG

  11.07.2017
SatComScope

Project focus

• Analysis of free-space optical communication properties and requirements.
• Development and integration of an adaptive optical compensation system for free-space optical communication into a small telescope.
• Dual stage actuation of the adaptive optical system and the telescope mount.

Description

This project aims to integrate adaptive optics (AO) technology into small to medium-sized telescope systems of the industrial partner, ASA Astrosysteme, in order to enable free space optical (FSO) communication between satellites and optical ground stations. Compared to radio-frequency communication, this yields a potential increase of the data rate of more than 1 order of magnitude, while simultaneously significantly reducing the emitting power and weight on the satellite. Furthermore, optical frequencies do not require licensing.



Principle of optical satellite communication. Precise pointing is required on both terminals.

Based on an integrated, mechatronic approach, the proposed AO system focuses on high performance and cost efficient realization to enable FSO communication with small to medium-sized telescopes operating as optical ground stations. The resulting telescope system will provide a stable laser-link between corresponding satellites and the developed optical ground station, enabling FSO communication at unprecedented data rates, while simultaneously reducing energy consumption of the emitter at the satellite.

System analysis

Atmospheric turbulences, as well as vibrations of the telescope system, significantly affect the performance of optical communication links. To ensure a reliable satellite link with high data-rates and low BER, these disturbances are compensated by means of an adaptive optical system. A key trade-off is the system complexity vs. compensation performance. Especially for small telescopes a shift towards low-order aberrations is visible. All above tip-tilt aberrations may contribute up to 80% of the total wavefront error, hence requiring a powerful tip-tilt compensation system.

 



Measured wavefront error statistics over time acquired with a 30 cm telescope in Vienna using the star Actrurus. A clear dominance of low-order aberrations is visible

 

“Ultra low earth orbit (U-LEO)” link

To evaluate various AO approaches a reflective FSO communication link is available between two buildings of TU Wien. A two way distance of 600 m in urban environment provides harsh conditions for the developed systems.

Adaptive optical setup for free-space optical communication using the U-LEO link. A 35 cm SC-telescope as well as a, 10 cm Newton are available for communication experiments.

Ultra low earch orbit communication link over a distance of 600 m between two buildings of TU Wien.

Optical system for U-LEO link

A 35 cm SC-telescope is used as receiving antenna for the urban link. A combination of tip-tilt compensation (FSM+QPD) and adaptive optical system (DM + WFS) is used to test various correction approaches.



Schematic setup of the U-LEO optical system including a FSM, a deformable mirror (M2), a quad-photodiode (QPD) and a wavefront sensor (WFS). The 35 cm SC-telescope is used for reception.

Tip-tilt correction for the U-LEO link reveals a significant improvement of the RMS errors, as shown below. The blue curves show the movement of the received spot on the QPD without correction. After 30 s correction is enabled and the deviations are compensated.



Tip-tilt control comparison of the U-LEO link. With out tip-tilt compensation an standard deviation of more than 2 urad is visible. If tip-tilt compensation is enabled, the error is reduced by up to a factor of ten, keeping the center of the received spot on the detector area.

 

Mobile optical bench

To enable evaluation of the developed tip-tilt compensation systems with various telescopes at different sites, a mobile version of the optical system is developed. It is designed, to be easily adapted and attached to telescope systems at TU Wien as well as at ASA Astrosysteme.



Schematic overview of the mobile optical bench for tip-tilt compensation.

 



Mobile optical bench attached to a ASA 12″ Newton telescope (left) and to a ASA AZ800 RC-telescope (right).

Tip-tilt compensation for LEO object tracking

Below two videos recorded during the same pass of the LEO object COSMOS 2315 are shown for comparison. Without tip-tilt compensation and open-loop tracking of the telescope mount an offset as well as fluctuations of the spot position are visible. If tip-tilt control is enable, both offset and fluctuations are compensated, keeping the center of the spot on a communication detector.

 

Video of a LEO object acquired with the AZ800 telescope without and with compensation.
The pointing error as well as the position fluctuations of the spot are significantly reduced.

Applications

• Optical satellite communication
• Astronomy applications
• Satellite laser ranging

Related Publications

• A. Sinn, T. Riel, F. Deisl, S. Schachner, and G. Schitter, High-bandwidth tip-tilt vibration compensation in telescope systems, in Proceedings of the Joint Conference 8th IFAC Symposium on Mechatronic Systems (MECHATRONICS 2019), and 11th IFAC Symposium on Nonlinear Control Systems (NOLCOS 2019), 2019.
  [BibTex] [Download]

  @InProceedings{TUW-282537,
  author = {Sinn, Andreas and Riel, Thomas and Deisl, Florian and Schachner, Stephan and Schitter, Georg},
  title = {High-bandwidth tip-tilt vibration compensation in telescope systems},
  booktitle = {Proceedings of the Joint Conference 8th IFAC Symposium on Mechatronic Systems (MECHATRONICS 2019), and 11th IFAC Symposium on Nonlinear Control Systems (NOLCOS 2019)},
  year = {2019},
  volume = {52/15},
  note = {Vortrag: Joint Conference 8th IFAC Symposium on Mechatronic Systems (MECHATRONICS 2019), and 11th IFAC Symposium on Nonlinear Control Systems (NOLCOS 2019), Wien; 2019-09-04 -- 2019-09-06},
  doi = {10.1016/j.ifacol.2019.11.733},
  url = {https://www.sciencedirect.com/science/article/pii/S2405896319317276?via%3Dihub},
  journal = {IFAC-PapersOnLine/Elsevier},
  keywords = {Vibration compensation, telescopes, optical communication, fast steering mirror, tip-tilt compensation},
  numpages = {6}
  }

• A. Sinn, T. Riel, P. Kremsner, and G. Schitter, Analysis of tip-tilt compensation for reflective free-space optical satellite communication, in Free-Space Laser Communications XXXI, 109101G, 2019.
  [BibTex] [Download]

  @InProceedings{TUW-282538,
  author = {Sinn, Andreas and Riel, Thomas and Kremsner, Peter and Schitter, Georg},
  title = {Analysis of tip-tilt compensation for reflective free-space optical satellite communication},
  booktitle = {Free-Space Laser Communications XXXI},
  year = {2019},
  address = {109101G},
  publisher = {SPIE},
  note = {Vortrag: SPIE Photonics West 2019, San Francisco, California, USA; 2019-02-02 -- 2019-02-07},
  doi = {10.1117/12.2506472},
  keywords = {optical satellite communication, adaptive optics, tip-tilt compensation, dynamic error budgeting},
  numpages = {12}
  }

• F. Deisl, Dual stage actuation of a telescope mount and a tip-tilt mirror for free-space optical communication, 2019.
  [BibTex]

  @MastersThesis{TUW-279640,
  author = {Deisl, Florian},
  title = {Dual stage actuation of a telescope mount and a tip-tilt mirror for free-space optical communication},
  school = {E376},
  year = {2019}
  }

• A. Sinn, T. Riel, F. Deisl, and G. Schitter, Tip-tilt vibration compensation: A system analysis, in Proceedings of 2017 Spring Topical Meeting on Precision Engineering and Optics: What are the Limits of Precision, and How to Characterize Them?, 2017, p. 42–47.
  [BibTex]

  @inproceedings{TUW-261675,
  author = {Sinn, Andreas and Riel, Thomas and Deisl, Florian and Schitter, Georg},
  title = {Tip-tilt vibration compensation: A system analysis},
  booktitle = {Proceedings of 2017 Spring Topical Meeting on Precision Engineering and Optics: What are the Limits of Precision, and How to Characterize Them?},
  year = {2017},
  pages = {42--47},
  note = {Vortrag: ASPE 2017 Spring Topical Meeting, Tucson (USA); 2017-04-24 -- 2017-04-25}
  }

• A. Sinn, T. Riel, F. Deisl, R. Saathof, and G. Schitter, Low-Power Reflective Optical Communication System for Pico- and Nano-Satellites, in AMOS 2016 Proceedings, 2016, p. 1403–1410.
  [BibTex] [Download]

  @InProceedings{TUW-252989,
  Title = {Low-Power Reflective Optical Communication System for Pico- and Nano-Satellites},
  Author = {Sinn, Andreas and Riel, Thomas and Deisl, Florian and Saathof, Rudolf and Schitter, Georg},
  Booktitle = {AMOS 2016 Proceedings},
  Year = {2016},
  Note = {Posterpr{\"a}sentation: Advanced Maui Optical Space Surveillance Technologies Conference (AMOS) 2016, Wailea, Hawaii (USA); 2016-09-20 -- 2016-09-23},
  url = {https://www.semanticscholar.org/paper/Low-Power-Reflective-Optical-Communication-System-Sinn-Riel/bfe4fcba68313914449b8ab2ff0d8526fdee820e#citing-papers},
  Pages = {1403--1410}
  }

Project partners

• ASA Astrosysteme GmbH

Funding

• FFG – Die Österreichische Forschungsförderungsgesellschaft
• ASA Astrosysteme GmbH

  11.07.2017
TracSat

Project focus

• Increasing the performance of existing optical satellite tracking stations to enable future applications such as optical satellite communication or satellite laser ranging
• Mechatronic analysis and improvement of the existing systems
• Iterative trajectory learning for the correction of environmental influences and improvement of the achieveable accuracy

Description

The precise tracking of high velocity satellites with ground based optical telescopes is a prerequisite for a number of future applications such as optical satellite communication, observation of space debris or satellite laser ranging. To achieve this goal, good mechatronic design as well as high performance control are necessary. Together with our industrial partner, ASA Astrosysteme GmbH, this project aims on increasing the achievable precision and tracking velocity of existing ASA ground stations.

Mechatronic Design and System Integration

To achieve the required precision the mechatronic design of the direct-drive telescope mounts a detailed analysis of the existing system is necessary. Dynamic error budgeting (DEB) is used as analysis  tool for this purpose. Based on this analysis various system level improvements have been made, such as the improvement of the current sensor, as shown in Fig. 1, which results in a factor 6.3 improvement in achievable precision. DEB is also used as design tool to guide the development of the improved current sensor system, as shown in Fig. 2.



Measured position error for two different current sensor systems. Using an improved sensor, the achieveable precision is impoved by a factor of 6.3.

 



Simulated relationship between the noise spectral density of the current sensor and the position noise of the rotor for constant velocity of 0.2 °/s and zero velocity.

Using the modified version of the telescope mount the influence of the switched operation mode is analyzed. Using a relative low switching frequency implies maximal efficiency of the amplifier but may also degrade the performance. To verify the simulation, the PWM switching frequency is varied, and the position error at various velocities is recorded. The data, shown in Fig. 3, experimentally confirm the simulation result.



RMS position error as function of the velocity in linear mode in comparison to switched mode. Error bars are shown for the measurements in switched mode, marking the measured range from 3 kHz to 48 kHz.

 

Precision Motion Control

The motion control system of the direct-drive telescope mount was enhanced. Instead of the previously used cascaded PID control, a model based state feedback control with disturbance observer is applied. Using this advanced control concept, external disturbances, such as wind shake or torque disturbances, can be effectively suppressed. This allows to maintain high precision even at the high angular velocities necessary for satellite tracking applications. Experimental verification with visual feedback is performed using various rocket bodies and satellites. An exemplary tracklet of the rocket body Breeze-M is shown in Fig. 4. A comparison between the implemented control concept and conventional PI control of the tracking performance of 43 tracking experiments is shown in Fig. 5 and reveals a factor of 3.8 improvement in precision.



Tracklet with 25 seconds duration of debris of the rocket body Breeze-M (NORAD ID: 36501), recorded on the 18th of September 2018, 21:43:35 UTC, with a mean angular velocity of 0.71 °/s. Also visible is the acceleration sequence at the start of the trajectory and two obstructions due to cloud cover in the first third of the tracklet (at an az-angle of 296° and 298°).

 



RMS servo error using standard PI control (blue, dashed) in comparison to the proposed control system (red, dash-dotted). Shown are the RMS servo errors of the performed tracklets as a function of the mean tracklet velocity.

 

Iterative Trajectory Learning

Iterative learning control is applied to improve the accuracy of the satellite tracking system. The desired satellite trajectory is pre-calculated and trained shortly before the actual satellite pass. The star background together with a plate solving algorithm, which identifies the astrometric coordinates of a given star pattern, is used as absolute position sensor during the training phase. This trajectory learning phase with sensor feedback allows the elimination of static, as well as dynamic errors within the telescope system. Tracking experiments using LEO as well as MEO satellites are conducted to confirm the improved tracking accuracy of the tracking system. The result of an exemplary trackle is shown in Fig. 6. Using the implemented trajectory learning algorithm, the visual tracking result is improved by a factor of six to 11, as shown in Fig. 7, and only limited by the used orbit prediction algorithm. By improving the accuracy of the tracking, residual motion of the tracked object within the image plane is removed.



Tracking error of the satellite LAGEOS-2 (NORAD ID: 22195) on 17th of September 2018. (a) tracking error during the learning process as a function of the number of performed iterations and (b) internal encoder error (black, solid) and optical tracking error (blue cross) during the final pass at 22:22:18 UTC.



Stack of 250 images taken of the satellites (a) CENTAUR R/B (NORAD ID: 26906) without iterative trajectory learning and (b) JASON-3 (NORAD ID: 41240) with trajectory learning. The image center is marked with a red cross. Passing stars can be seen as dashed lines in the stacked image.

A few exemplary videos of the achieved tracking results can be found here: Lageos-2, AJISAI, Jason-3

Utilizing the proposed algorithm together with the optimized system and controller design, the implemented tracking system can be used as a cost effective optical ground station for highly accurate and precise blind tracking of satellites. By also applying continuous orbit refinements based on the observed orbit should also allow a significant reduction of the orbit prediction uncertainty that is currently limiting the accuracy. This should enable an accuracy that is within the achieved sub-arcsecond precision. This will enable a wide range of users to gain access to a range of applications, such as optical satellite communication, satellite laser ranging or space debris observation.

Applications

• Optical satellite communication
• Space debris observation
• Satellite laser ranging

Related Publications

• T. Riel, A. Katalenic, R. Saathof, and G. Schitter, Dynamic Error Budgeting for a Friction-afflicted Permanent Magnet Synchronous Motor, in Proceedings ASPE 2016 Spring Topical Meeting – Precision Mechatronic SystemDesign and Control, 2016, p. 74–79.
  [BibTex]

  @InProceedings{TUW-249764,
  Title = {Dynamic Error Budgeting for a Friction-afflicted Permanent Magnet Synchronous Motor},
  Author = {Riel, Thomas and Katalenic, Andelko and Saathof, Rudolf and Schitter, Georg},
  Booktitle = {Proceedings ASPE 2016 Spring Topical Meeting - Precision Mechatronic SystemDesign and Control},
  Year = {2016},
  Note = {Vortrag: ASPE 2016 Spring Topic Meeting - Precision Mechatronic System Design and Control, Phoenix (USA); 2016-04-20 -- 2016-04-22},
  Pages = {74--79}
  }

• T. Riel, R. Saathof, A. Katalenic, and G. Schitter, Noise Analysis and Improvement of a Permanent Magnet Synchronous Motor by Dynamic Error Budgeting, in Proceedings of the 7th IFAC Symposium on Mechatronic Systems, 2016, p. 339–346.
  [BibTex]

  @InProceedings{TUW-251115,
  Title = {Noise Analysis and Improvement of a Permanent Magnet Synchronous Motor by Dynamic Error Budgeting},
  Author = {Riel, Thomas and Saathof, Rudolf and Katalenic, Andelko and Schitter, Georg},
  Booktitle = {Proceedings of the 7th IFAC Symposium on Mechatronic Systems},
  Year = {2016},
  Note = {Vortrag: 7th IFAC Symposium on Mechatronic Systems {\&} 15th Mechatronics Forum International Conference, Loughborough (Vereinigte K{\"o}nigreich); 2016-09-05 -- 2016-09-08},
  Pages = {339--346},
  Doi = {10.1016/j.ifacol.2016.10.578},
  Keywords = {Dynamic Error Budgeting, Performance analysis, Error estimation, Servo systems, Permanent magnet motors}
  }

• T. Riel, R. Saathof, A. Katalenic, and G. Schitter, Tracking Performance Analysis and Control of a Small Robotic Telescope System, in AMOS 2016 Proceedings, 2016.
  [BibTex]

  @InProceedings{TUW-252685,
  Title = {Tracking Performance Analysis and Control of a Small Robotic Telescope System},
  Author = {Riel, Thomas and Saathof, Rudolf and Katalenic, Andelko and Schitter, Georg},
  Booktitle = {AMOS 2016 Proceedings},
  Year = {2016},
  Note = {Posterpr{\"a}sentation: Advanced Maui Optical Space Surveillance Technologies Conference (AMOS) 2016, Wailea, Hawaii (USA); 2016-09-20 -- 2016-09-23},
  Numpages = {8}
  }

Project partners

• ASA Astrosysteme GmbH

Funding

• FFG – Die Österreichische Forschungsförderungsgesellschaft
• ASA Astrosysteme GmbH

  11.07.2017
Distributed Intelligent Automation with Next-generation Architecture – DIANA

Project focus

• Development of novel methods for next-generation automation systems
• Development and fostering of EtherNet/IP ™ systems and solutions
• Maintaining and enhancing the open-source EtherNet/IP ™ adapter stack OpENer, available at https://github.com/EIPStackGroup/OpENer

Description

The long-running project DIANA, is a solely industry-funded research project, concerned with two main topics: the progression of automation system, to cope with the ever changing requirements of industry, and the development and fostering of EtherNet/IP ™ and the open-source EtherNet/IP ™ adapter stack OpENer.

In DIANA novel approaches to industrial automation are researched and verified via industrial-grade prototypes in cooperation with one of the world-leading suppliers for automation systems, Rockwell Automation Inc.

The development and research of EtherNet/IP ™ has lead to the development of the open-source EtherNet/IP ™ stack OpENer (available at GitHub), which ACIN is continuously enhancing and extending the open-source software. Examples worth mentioning in the development of OpENer are the integration of EtherNet/IP with IEC 61499 compliant runtime-systems and the  development of the Common Industrial Protocol (CIP) ™ Base Energy ™ object, CIP Electrical Energy ™ object, and the CIP Time Sync ™ object. The goal of these implementations are to support the ever-growing base of EtherNet/IP ™ users, as wells as to help improving the EtherNet/IP ™ specification.

Applications

• OpENer
• Raspberry Pi based prototypes for various CIP/EtherNet IP ™ objects
• Integration of custom hardware with Rockwell PLC systems

Related Publications

• M. Melik-Merkumians, M. Baierling, and G. Schitter, A Service-Oriented Domain Specific Language Programming Approach for Batch Processes, in Proceedings of 2016 IEEE 21th Conference on Emerging Technologies & Factory Automation, 2016.
  [BibTex]

  @InProceedings{TUW-251132,
  Title = {A Service-Oriented Domain Specific Language Programming Approach for Batch Processes},
  Author = {Melik-Merkumians, Martin and Baierling, Matthias and Schitter, Georg},
  Booktitle = {Proceedings of 2016 IEEE 21th Conference on Emerging Technologies {\&} Factory Automation},
  Year = {2016},
  Note = {Vortrag: 21st IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2016), Berlin; 2016-09-06 -- 2016-09-09},
  Doi = {10.1109/ETFA.2016.7733729},
  Eid = {68},
  ISBN = {978-1-5090-1314-2},
  Keywords = {SOA, DSL, Batch Process, ISA-88, IEC 61499, component based automation, service based automation},
  Numpages = {9}
  }

• M. Melik-Merkumians, M. Wenger, R. Hametner, and A. Zoitl, Increasing Portability and Reuseability of Distributed Control Programs by I/0 Access Abstraction, in Proceedings IEEE Emerging Technologies and Factory Automation (ETFA 2010), 2010.
  [BibTex]

  @InProceedings{TUW-0310201713,
  author = {Melik-Merkumians, M. and Wenger, M. and Hametner, R. and Zoitl, A.},
  title = {Increasing Portability and Reuseability of Distributed Control Programs by I/0 Access Abstraction},
  booktitle = {Proceedings IEEE Emerging Technologies and Factory Automation (ETFA 2010)},
  year = {2010}
  }

• M. Melik-Merkumians, T. Baier, M. Steinegger, W. Lepuschitz, I. Hegny, and A. Zoitl, Towards OPC UA as portable SOA Middleware between Control Software and External Added Value Applications, in Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies and Factory Automation (ETFA 2012), 2012.
  [BibTex] [Download]

  @InProceedings{TUW-031020174,
  Title = {Towards OPC UA as portable SOA Middleware between Control Software and External Added Value Applications},
  Author = {Melik-Merkumians, M. and Baier, T. and Steinegger, M. and Lepuschitz, W. and Hegny, I. and Zoitl, A.},
  Booktitle = {Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies and Factory Automation (ETFA 2012)},
  Year = {2012},
  Doi = {10.1109/ETFA.2012.6489640}
  }

• W. Leonhardsberger and A. Zoitl, Using EtherNet/IP with IEC 61499 Communication Function Blocks, in 5th International Conference on Industrial Applications of Holonic and Multi-Agent Systems, HoloMAS 2011, Toulouse, France, August 29-31, 2011, Proceedings, Lecture Notes in Computer Science, Vol. 6867, 2011, p. 39–49.
  [BibTex]

  @InProceedings{TUW-200251,
  Title = {Using EtherNet/IP with IEC 61499 Communication Function Blocks},
  Author = {Leonhardsberger, Wilhelm and Zoitl, Alois},
  Booktitle = {5th International Conference on Industrial Applications of Holonic and Multi-Agent Systems, HoloMAS 2011, Toulouse, France, August 29-31, 2011, Proceedings},
  Year = {2011},
  Address = {Lecture Notes in Computer Science, Vol. 6867},
  Note = {Vortrag: 5th International Conference on Industrial Applications of Holonic and Multi-Agent Systems, France, Toulouse; 2011-08-29 -- 2011-08-31},
  Pages = {39--49},
  Publisher = {Springer},
  ISBN = {978-3-642-23180-3},
  Url = {https://link.springer.com/chapter/10.1007/978-3-642-23181-0_4}
  }

Project partners

• Rockwell Automation, Inc.

Funding

Funded by Rockwell Automation, Inc.

  10.07.2017
Ball on Ball

Project focus

• Modelling of a Ball on Ball Setup
• Control of a Ball on Ball Setup
• Camera based control

Description

Vision-based measurement methods are becoming increasingly important in automation technology. Well-known examples are autonomous vehicles that navigate through the environment using a variety of imaging sensors, or robots that detect if someone has entered the working area using a camera. Nowadays the needed computing power for real-time image processing is readily-available which opens up new possibilities to use vision-based measurement methods in industrial automation. In this project a Ball-on-Ball control setup with vision-based position measurement is designed, simulated and built to demonstrate the capabilities of imaging techniques. Before the setup is implemented a nonlinear mathematical model of the whole setup is derived and simulations of the system behaviour are done. The control and the image processing is done on an industrial standard PLC. For comparison a second measurement method using laser distance sensors is also implemented. The residual error and the disturbance reaction of both measurement methods are analyzed and compared using different controllers and sample times. Finally a trajectory following for the upper ball is implemented.

Automation and Industrial Control Systems

To actuate the lower ball three omniwheels are used. Each omniwheel is driven by Beckhoff DC servo motor with a gearbox in between. The Control of the motor current and the motor speed is done directly on the motor controllers. That means, that the PLC calculates the speeds needed for all three drives and hands them over to the controllers. The position mesaurement of the upper ball can ether be done by two triangulation sensores or by a camera on top of the upper ball. For robustness reasons of detecting the upper ball the recorded image is transformed into the hue, saturation, and value color space. Due to this transformation the dependency of the illumination can be suppressed. The image aquisition and calculation of the upper ball position is done entirely on the PLC.



Complete ball on ball setup

Video 1: Trajectory following of the upper ball seen from the cameras perspective.
The desired trajectory is a circle.

Applications

• Camera based control

Related Publications

• C:. Zech, Development, assembly and implementation of a ball on ball control setup, 2017.
  [BibTex]

  @MastersThesis{TUW-311819,
  Title = {Development, assembly and implementation of a ball on ball control setup},
  Author = {C: Zech},
  School = {E376},
  Year = {2017}
  }

Project partners

• Beckhoff Automation GmbH

Funding

• Beckhoff Automation GmbH

  10.07.2017
IQ AFM

Imaging, handling and manipulation of material with high resolution are important techniques for various applications of research. Atomic force microscopes (AFM) are one of the most important tools for imaging applications with spatial resolution beyond the diffraction limit of light. The project aims is to build a complete AFM-system, including advanced imaging modes, in cooperation with Anton Paar GmbH.

Project focus

• High-speed and long stroke Z-actuator
• Design and implementation of High-speed and low-noise laser-deflection readout system
• Development of a scanning-lever AFM-system
• Development of advanced measurement modes

Description

Imaging, handling and manipulation of material with high resolution are important techniques for various applications of research. Atomic force microscopes (AFM) are one of the most important tools for imaging applications with spatial resolution beyond the diffraction limit of light. The project aims is to build a complete AFM-system, including advanced imaging modes, in cooperation with Anton Paar GmbH. The work packages belonging to ACIN includes the development of the AFM-head components, high-speed, vertical Z-actuator, high-speed and low-noise laser-deflection readout system, scanning-lever AFM-system and advanced measurement modes. A follow-up project was focused on the development of functional imaging-modes. Various research fields such as biology, physics or materials science are using such functional imaging-modes like Kelvin-probe force microscopy (KPFM). With KPFM it is possible to map the sample surface potential in a quantitative way with nanometer resolution. At ACIN a novel feedback based Scanning Probe Microscopy method which enables quantitative surface potential measurements without the need of the DC bias of Kelvin Probe Force Microscopy was developed. This method opens the way to image the surface potential of various samples such as semiconductors or biological cells without the need for applying a disturbing or interfering DC-bias and enables new applications of feedback based KPFM technologies.



Comparison of classical KPFM and AC-KPFMy of a positive charge pattern on PMMA. Topography (A) and surface potential V recorded with classical KPFM (B). (C) amplitude b and (D) surface potential V = −b2 acquired with AC-KPFMy of the same pattern as in (B). The images (C) and (D) were recorded immediately after (A) and (B) without disengaging the tip.

Applications

• Nanometrology Systems
• AFM, SPM, KPFM, EFM, MFM, QNM etc.

Related Publications

• D. Kohl, P. Mesquida, and G. Schitter, Multi-frequency Kelvin Probe Force Microscopy Method for Charge Mapping Without DC-Bias, in Nano and Photonics & FemtoMat 2017, 2017.
  [BibTex]

  @Conference{TUW-041020177,
  Title = {Multi-frequency Kelvin Probe Force Microscopy Method for Charge Mapping Without DC-Bias},
  Author = {Kohl, D. and Mesquida, P. and Schitter, G.},
  Booktitle = {Nano and Photonics \& FemtoMat 2017},
  Year = {2017}
  }

• D. Kohl, P. Mesquida, and G. Schitter, Quantitative DC-free Kelvin Probe Force Microscopy, in Final Program 42nd International Conference on Micro and Nano Engineering, 2016.
  [BibTex]

  @InProceedings{TUW-254059,
  Title = {Quantitative DC-free Kelvin Probe Force Microscopy},
  Author = {Kohl, Dominik and Mesquida, Patrick and Schitter, Georg},
  Booktitle = {Final Program 42nd International Conference on Micro and Nano Engineering},
  Year = {2016},
  Note = {Vortrag: Micro and Nano Engineering 2016, VIenna; 2016-09-19 -- 2016-09-23},
  Doi = {10.1016/j.mee.2017.01.005},
  Numpages = {2}
  }

• R. Saathof, T. Riel, M. Bibl, D. Kohl, H. W. Yoo, and G. Schitter, Non-parametric robustness analysis for feedback motion control for a high precision stage with large mass uncertainty, in Proceedings of the 2016 American Control Conference, 2016, p. 2611–2616.
  [BibTex]

  @InProceedings{TUW-254388,
  Title = {Non-parametric robustness analysis for feedback motion control for a high precision stage with large mass uncertainty},
  Author = {Saathof, Rudolf and Riel, Thomas and Bibl, Matthias and Kohl, Dominik and Yoo, Han Woong and Schitter, Georg},
  Booktitle = {Proceedings of the 2016 American Control Conference},
  Year = {2016},
  Note = {Vortrag: 2016 American Control Conference, Boston (USA); 2016-07-06 -- 2016-07-08},
  Pages = {2611--2616},
  Doi = {10.1109/ACC.2016.7525310}
  }

• D. Kohl, T. Riel, R. Saathof, J. Steininger, and G. Schitter, Auto-Tuning PI Controller for Surface Tracking in Atomic Force Microscopy – A Practical Approach, in Proceedings of the 2016 American Control Conference, 2016.
  [BibTex]

  @InProceedings{TUW-254062,
  Title = {Auto-Tuning PI Controller for Surface Tracking in Atomic Force Microscopy - A Practical Approach},
  Author = {Kohl, Dominik and Riel, Thomas and Saathof, Rudolf and Steininger, J{\"u}rgen and Schitter, Georg},
  Booktitle = {Proceedings of the 2016 American Control Conference},
  Year = {2016},
  Note = {Vortrag: 2016 American Control Conference, Boston (USA); 2016-07-06 -- 2016-07-08},
  Doi = {10.1109/ACC.2016.7526840},
  Numpages = {6}
  }

• J. Steininger, M. Bibl, H. W. Yoo, and G. Schitter, High bandwidth deflection readout for atomic force microscopes, Review of Scientific Instruments, vol. 86, 2015.
  [BibTex]

  @Article{TUW-242622,
  Title = {High bandwidth deflection readout for atomic force microscopes},
  Author = {Steininger, J{\"u}rgen and Bibl, Matthias and Yoo, Han Woong and Schitter, Georg},
  Journal = {Review of Scientific Instruments},
  Year = {2015},
  Volume = {86},
  Doi = {10.1063/1.4932188}
  }

• J. Steininger, R. Paris, and G. Schitter, Increasing sensitivity while reducing crosstalk of the force sensor in atomic force microscopes, in Proceedings of the 14th International Conference of the European Society for Precision Engineering and Nanotechnology, 2014, p. 321–324.
  [BibTex]

  @InProceedings{TUW-229780,
  Title = {Increasing sensitivity while reducing crosstalk of the force sensor in atomic force microscopes},
  Author = {Steininger, J{\"u}rgen and Paris, Ren{\'e} and Schitter, Georg},
  Booktitle = {Proceedings of the 14th International Conference of the European Society for Precision Engineering and Nanotechnology},
  Year = {2014},
  Note = {Posterpr{\"a}sentation: 14th International Conference and Exhibition of the European Society for Precision Engineering {\&} Nanotechnology, Dubrovnik, Croatia; 2014-06-02 -- 2014-06-06},
  Pages = {321--324},
  ISBN = {978-0-9566790-3-1},
  Journal = {Euspen}
  }

• J. Steininger, R. Paris, and G. Schitter, Improving the Deflection Readout Mechanism of an Atomic Force Microscope, in MESS14 Microelectronic Systems Symposium, Band 76 der OVE-Schriftenreihe, 76, 2014, p. 22.
  [BibTex]

  @InProceedings{TUW-229786,
  Title = {Improving the Deflection Readout Mechanism of an Atomic Force Microscope},
  Author = {Steininger, J{\"u}rgen and Paris, Ren{\'e} and Schitter, Georg},
  Booktitle = {MESS14 Microelectronic Systems Symposium, Band 76 der OVE-Schriftenreihe},
  Year = {2014},
  Address = {76},
  Note = {Posterpr{\"a}sentation: MESS14 Microelectronic Systems Symposium, Vienna; 2014-05-08 -- 2014-05-09},
  Pages = {22},
  ISBN = {978-3-85133-082-3}
  }

• J. Steininger and G. Schitter, Influence of the Photodetector Geometry on the Deflection Measurement in Atomic Force Microscopes, in Proceedings of the ASPE 2014 Annual Meeting, 2014, p. 674–679.
  [BibTex]

  @InProceedings{TUW-233073,
  Title = {Influence of the Photodetector Geometry on the Deflection Measurement in Atomic Force Microscopes},
  Author = {Steininger, J{\"u}rgen and Schitter, Georg},
  Booktitle = {Proceedings of the ASPE 2014 Annual Meeting},
  Year = {2014},
  Note = {Vortrag: ASPE 2014 Annual Meeting, Boston (USA); 2014-11-09 -- 2014-11-14},
  Pages = {674--679},
  ISBN = {978-1-887706-66-7}
  }

• J. Steininger, S. Kuiper, S. Ito, and G. Schitter, Schnelle Rasterkraftmikroskopie durch moderne Regelungstechnik und mechatronische Systemintegration, E&I Elektrotechnik und Informationstechnik, vol. 129, iss. 1, p. 28–33, 2012.
  [BibTex]

  @Article{TUW-207882,
  Title = {Schnelle Rasterkraftmikroskopie durch moderne Regelungstechnik und mechatronische Systemintegration},
  Author = {Steininger, J{\"u}rgen and Kuiper, Stefan and Ito, Shingo and Schitter, Georg},
  Journal = {E{\&}I Elektrotechnik und Informationstechnik},
  Year = {2012},
  Number = {1},
  Pages = {28--33},
  Volume = {129},
  Doi = {10.1007/s00502-012-0070-8},
  Keywords = {SPM, AFM, scanning probe, control, nanotechnology, nanometrology}
  }

Project partners

• Anton Paar GmbH

Funding

• Austrian Research Promotion Agency (FFG)
• Anton Paar GmbH