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  • Control Engineering participates in the national research school DISC (Dutch Institute of Systems and Control). At present we are active in the following projects:
    • modelling and simulation
    • intelligent control
    • advanced robotics and design of mechatronic systems
    • embedded control systems
    • tools for mechatronic design
    • measurement science and instrumentation
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  • Research

  • ROBOTICS AND MECHATRONICS

  • Robotics and Mechatronics (formerly Control Engineering) deals with application of modern systems and control methods to practical situations. Focus is on robotics, as a specific class of mechatronic systems. The research is embedded in the CTIT and MIRA institutes. The research of the group is application oriented. Main goal is to investigate the applicability of modern systems and control methods to practical situations in the area of robotics.

    Robot application areas we investigate are: inspection robotics; medical robotics (assistance to surgeons); service robotics (street cleaning, service to people).

    The science and engineering topics we work on are: modeling and simulation of physical systems; intelligent control; robotic actuators; embedded control systems.

    In our lab we have quite a variety of robotic setups: basic 1 or 2 motor systems, precise motion control platforms, a production cell-like block circulator, wheeled mobile robots and humanoid walking robots.
  • Research in Control Engineering

  • The main research goal of the Control Engineering group is to investigate the applicability of modern systems and control methods to practical situations. Emphasis is on design, especially in the multidisciplinary area of mechatronics. We see mechatronics as a synergistic approach to the integrated and optimal design of a mechanical system and its embedded control system, where solutions are sought that cross the borders of the different domains. The research of the group covers the whole design trajectory of a (mechatronic) system, starting with modelling of the physical system followed by the design of an (intelligent) controlled system and realization of the controller in an embedded computer system. The concept of ports for interconnecting (parts of) models and controllers and pieces of software is a common factor in these research activities. The research of Control Engineering is carried out in the IMPACT and CTIT Institutes.
  • Projects

  • Modelling and Simulation

  • Description
    The central theme of this research is an inter-disciplinary, integrated, port-based approach to the modelling of physical system behaviour in various engineering domains. It follows an energy-based approach, making extensive use of the (multi-)bond graph notation, and is subdivided in several classes of projects.
    Where applicable, the modelling activities of the laboratory are used as a basis to generate re-usable, generic (sub-) model structures of various engineering systems:
    • modelling and simulation of bouncing and/or switching objects
    • generalization of the developed approach to arbitrary spatial objects
    • modelling of rotating electric machines
    1. dissemination and generalization of earlier published work (Geoplex book; CRC Modeling Handbook edited by Paul Fishwick; CISM Advanced School Udine)
    2. thermodynamic systems. Papers on this topic, in cooperation with the Geoplex partners in Lyon were published in 2007-2008.

    Port-based approach of complex distributed-parameter system models for analysis and simulation (PACDAS, STW-TWI.6012)
    This project, funded by STW, is in cooperation with the Systems and Control Group at the Department of Mathematics. One PhD student, Norbert Ligterink, started in September 2003 on the project, and Goran Golo was a postdoc from February till December 2003. From January 2006, Damien Eberard, a postdoc from France, joined the project. He works mainly in Groningen, in the new Applied Analysis Group of Arjan van der Schaft started September 2005.

    The research aim of the project is to create a synthesis between two successful approaches to modelling and simulation of physical engineering systems: the finite element approach to distributed-parameter system models, and the multi-physics port-based approach to lumped system models. The purpose is the marriage of the accuracy and power of finite element methods (FEM), with the versatility, dynamics, and control of port-based modelling.
    There are several aspects to this synthesis:

    • the port-based formulation of continuous, or distributed, systems, such that the dynamics can adapt the changing boundary conditions, i.e., port input.
    • a general geometric Hamiltonian formulation, such that flow, effort, and power conservation are exact, for a systematic approach, which can extend to several physics domains, which, e.g., eventually should yield proper models for damping.
    • model reduction methods, which can handle the configuration dependent dynamics, such as pre-strain, or varying load, where the essential dynamics of a distributed element is retained for a simulation, without the numerical effort of FEM.
    • a library of segments (beam, plate, solids, etc.), material properties (conductance, rigidity, etc.), and port-types (welding, screws, airgap) which are the basis for continuous dynamics simulation in 20-sim.

    Some more examples of the PACDAS project
    Dynamics of nonlinear Hamiltonians
    A Hamiltonian of an elastic beam is given as a polynomial with about 220 terms, to fourth order. The system can be used to find a minimal, or static, solution, using dissipation, which is the Control-Engineering version of a Conjugate Gradient approach.

    The same Hamiltonian and the same state can be used for a dynamical simulation, which conserves energy, not explicitly, but to 5 decimal places for 3000 time steps.

    The code is written in C, and uses the libraries of libplot and lapack. It consists of two separate codes:

    1. the generation of the Hamiltonian, written as a data file,
    2. the simulation of the Hamiltonian, with stepsize and damping, and multiple data output.

    The evaluation (functional derivative) costs about three times the total number of factors in the Hamiltonian in floating-point operations. The improved integration step using the last and previous gradients. The simulation tests for stepsize errors, by calculating the energy in the system. The simulations above take only seconds to run, where I/O account for most of the computing time.

    Geoplex
    The goal of the EU-sponsored project GeoPleX was to develop methods and software tools to help in the modelling, analysis, and control of complex physical systems in several physical domains. The project is done by partners all over Europe; one of these partners is the Systems and Control Group at the Department of Mathematics. Since energy often plays an important role in these systems, the starting point for the development is the concept of a Port-Controlled Hamiltonian system, in which the energy structure is shown explicitly.
    The Geoplex project was finished in 2006. A book that gives an overview of the Geoplex research will be published in 2008 by Springer.

      • The black lines represent the resultant forces on the boundary nodes. Eventually, the sum force is zero
      • One end of the beam is suddenly released from the clamped boundary conditions. The bending dynamics is generally much slower than the longitudinal vibration dynamics
  • Advanced Robotics and Mechatronics

  • Description
    This research program focuses towards robotics applications being a quickly rising multidisciplinary market and challenging research field. The structure of the research activities can be pictured using a matrix structure in which the columns represent the robotics application fields and the rows the embedding technologies.

    The chair Advanced Robotics is part of the 3TU Center of Excellence on Intelligent Mechatronic Systems for its activities and expertise in the Robotics field. The research of Control Engineering is carried out in the IMPACT and CTIT Institutes.
    One unique and characterizing feature of the philosophy with which research is performed is the use of the `port based’ way of thinking like bond graphs and port Hamiltonian systems for the modeling and control of multi-domain systems.
    Two Humanoids projects are carried on: one together with the 3TU and Philips and one at the Institute level in collaboration with Demcon.
    Strong collaborations with the Mechatronic Valley Twente and national industries like Philips, TNO, ESA, OCE, Thales are taking place.

     

    Ongoing work...

    Humanoid Robotics

    The groups dream is to build a fully functional humanoid robot in the next decade. With this purpose, the group is putting effort in doing research on different parts of humanoids. In particular, in the last year, the group has been working on the development of a humanoid head-neck system, a dexterous robotic hand, an energy efficient knee locking mechanisms and, finally, by continuing on earlier work of the group, extended knowledge on bipedal walking. The complete humanoid project realizes a really multidisciplinary platform which requires the close collaboration with other Departments and Faculties of the University of Twente, in particular with the Mechanical Engineering and Industrial Design. Moreover, in this context, the group has extended the collaboration network with various companies of the Mechatronic Valley Twente and the research groups of the other technical Universities of The Netherlands.

    Humanoid walking
    The group believes that a thorough understanding of 3D dynamics is the key issue for the design of robust and energy efficient walking algorithms. For this reason, PhD student Gijs van Oort has worked on model simplification using geometrical insights. The aim is finding mathematical ways to convert generalized-coordinate models to models with only a few meaningful 'coordinates'.
    Several MSc. projects on walking theory were successfully finished: combination of dynamic walking and ZMP walking and non-linear energy-conservative oscillators to implement walking structures. Innovative locking mechanism will be implemented in the bipedal walker Dribbel.
    In collaboration with TU Delft, TU Eindhoven and Philips, the initiative "Dutch Robotics", which aims at working closely together in this field has been started. The first big project, building the soccer-robot TULIP, got much momentum this year by participating in the RoboCup World Championship in China. It has been worked on software architecture of the robot.

    As walking requires oscillatory behavior of the legs, and therefore of the actuators attached to the legs, it makes sense to choose actuators that are well-equipped for this job. Unfortunately, electric motors as well as other conventional actuators behave very badly in this type of actuation: they consume a lot of energy and are not able to store negative work done during part of the oscillatory cycle. The solution may lie in the development of variable impedance actuators. In the context of variable impedance actuators, a European project (in FP7), called VIActors has been financed. As a preliminary study on this topic, a novel type of infinitely variable transmission (which is a part of a variable impedance actuator) has been developed.

    Humanoid head
    As a separate track, a humanoid head-neck has been developed. The system realizes a multidisciplinary platform interesting from mechanical, control and human-machine interaction point of view. The project has been done in collaboration with Demcon, a hi-tech company situated in Oldenzaal. The humanoid head has 7 degrees of freedom (four in the neck and three in the eyes) and reacts in a human-like way to its environment (e.g. it looks around, using saccades, dynamically searching for interesting things to look at). The external design and implementation of expression by means of light projection from the interal part have taken place. Together with the UT research group Human Media Interaction, the group is now working on improving the behavior, in order to integrate speech recognition and synthesis, audio interaction and human-like emotions.

    Falcon
    This project in collaboration with ESI and Van der Lande Industries is concerned with in the realization of a robotic system for the manipulation and composition of orders in a distribution center. The research will be twofold. On one hand a variable impedance dexterous hand will be developed which should be able to robustly and dexterously to grasp object both via power grasps and with tips grasps, depending on the geometry. The other part of the project is dedicated to visual servoing of the arm-hand system.

    Medical Robotics

    Tele-manipulation
    As surgical techniques are becoming less invasive (MIS procedures) for the patient, they are becoming more complex for the surgeon. For this reason the medical community looks towards the possibilities of robotics to alleviate this complexity. The “Da Vinci Surgical System” by Intuitive Surgical Inc. has demonstrated that by means of a tele-manipulation system the complexity of interpreting the surgical field and making the desired movements can be greatly simplified.
    A drawback of all MIS procedures is the loss of “touch” of the surgeon. He is either manipulating the operation scene from a remote location, or through long laparoscopic instruments. Studies have shown that the surgeon is capable of performing the operation with less trauma to the surrounding tissue if his sense of force is restored.
    A common aspect which greatly complicates the design of such a bilateral control loop is time delay in the communication channel. Many algorithms for these bilateral control loops exist, which either offer good stability properties with respect to time delay and poor transparency or vice versa.
    In this research project a new approach to the design of bilateral control loops will be studied which aims at good stability properties and a maximum achievable transparency under arbitrary time delays based on energy exchange considerations. A first MSc project in this field was carried out by B. Babakhani, MSc and M.C.J. Franken, MSc is pursuing his PhD in this direction.
    Natural Orifice Transluminal Endoscopic Surgery
    Natural orifice transluminal endoscopic surgery (NOTES) is a new form of minimally invasive surgery (MIS). The main difference between NOTES and traditional MIS is that the operating scene is entered through one of the natural openings of the human body. In April 2007 the first true NOTES operation was presented at the Japanese Congress of Surgery in Osaka. The operation consisted of the removal of the gall bladder (cholecystectomy) in a 30-year-old woman and was carried out transvaginal [1].

    NOTES is expected to have several benefits over traditional MIS. The most important benefit would be that even less damage is inflicted on the patient during the operation. This means that he suffers less from postoperative pain and will return to his daily life at an earlier stage. Also MIS operations can be performed on patients who suffer from severe obesity (which is problematic for traditional MIS), or from inflictions to the abdomen.
    The approach to surgery using NOTES techniques greatly differs from current laparoscopic techniques. For a successful introduction of NOTES in the OR, robotic tele-manipulation will be a key ingredient. The tele-manipulation device will have to empower the surgeon to carry out various kinds of common diagnostic and therapeutic procedures in a time efficient and cost effective manner.
    The TeleFlex project consisting of four PhD positions, of which two at the CE group, has started in the past year in this upcoming research field. The focus of the TeleFlex project is directed at the master device of the tele-manipulation chain. R. Reilink, MSc. will do research on the effects haptic feedback has on a sentient surgeon and under which conditions this feedback will benefit the surgeon. M. Bezemer, MSc will focus on the software structure and how layered software should be designed to guarantee safety.

    LOPES
    This project, has been concerned with the realization of a lower extremities exoskeleton for the rehabilitation of stroke patients. The project, financed by NWO, is coordinated by Herman van der Kooij and has involved 3 Ph.D. students one of which in the Control Engineering group.

    REFLEXLEG
    In this project, financed by STW, a new transfemoral prosthesis will be developed which will have energetic advantages with respect to existing ones. This project involves 2 Ph.D. students and is carried out in collaboration with the group of Prof. Velting and the Roessing R&D center.
     

    Inspection Robotics

    PIRATE
    In 2007 a mobile inspection system for live gas mains has been developed. This project is a joint effort of Continuon Netbeheer, Kiwa Gastec Technology B.V. and the University of Twente. The prototype hardware has been developed at DEMCON. The robot is developed for autonomous internal inspection of the low pressure gas mains, with minimal intervention of human operators. The robot will be used to detect leaks or possible weak points in the gas mains.

    In the first stage of this project, the development of a moving mobile robot base has been emphasized. The low pressure net in the Netherlands uses pipes with an inner diameter as small as 50 mm, thus putting a severe limitation on the robot's size. A mechanical prototype has been developed which is capable of moving through pipes ranging in diameter from 50 to 120 mm. It can move through mitered bends and T-joints and take inclinations of 30 degrees. The robot has the form of a 'snake', consisting of seven wheeled modules which all have a designated function. Two modules are used for propulsion, two for bending the robot's shape (for navigation trough bends), one module in the center for rotation the robot around its axis, one module for power storage and one module for control and sensor electronics. The mechanical setup has been tested in a structured lab environment. The next step will be to test the functionality in a more realistic environment.

    On a different level work has been done on the design of a camera setup with structured light bundle (laser projecting circles) which can be used as sensor to measure pipe deformation, and which also can be used to detect obstacles and bends which is necessary for navigation. In following projects we hope to miniaturize this setup in order to integrate it into the robot's design.

    Exomars
    In this project carried out in collaboration with ESA, the modeling of altitude maps and their use in the prediction of the navigation of the ExoMars rover is considered. Problems which arise in this study relate a combination of sparse altitude data with precise terramechanics simulations. This is tackled using a hybrid use of differential geometric techniques and computational geometric methods.

    • Soccer robot Tulip
    • Humanoid head
    • Humanoid head
  • Intelligent Control

  • Description
    This project investigates the possibilities of adaptive and learning control systems. Special attention is paid to (feed-forward) learning control systems, based on neural networks. Agent-based control systems are studied as a port-base approach to controller design.

    Ongoing work...

    Model-reference-based learning feed-forward control
    Most work on learning feed-forward control has been on done on compensation of non-linear effects, requiring more or less complex function approximators. However, for unkown or time-variable linear systems the inverse of the process transfer function can efficiently be described by means of a simple linear transfer function. A learning feed-forward control scheme has been developed based on the philosophy of stable model-reference adaptive systems. It appears that this system is very robust against a mismatch of the order of the process and the inverse model. In addition, it has a low sensitivity for noise. Future work will be to investigate if this scheme that has superior performance for dealing with unknown or time-varying process dynamics can be combined with e.g. the KSM scheme that is successful in dealing with the non-linearities in a process.
    A comparison has been made between different learning and adaptive control systems to identify the stronger and weaker points of each method. Experiments have been carried out on the "Mechatronic Demonstrator


    Agent-based controller design
    For control algorithms a port-based approach is less well developed. Such an approach would make controllers more modular and would contribute to reusable controller components and quicker developments. From a control-engineering point of view a controller is often considered as containing the control algorithms only. But in practice the control algorithm is only a small part of total software used to safely start up, control and shut down the system. Error detection, error handling and graceful degradation are issues here. These parts of the controller can often be reused from earlier projects. Using agents is a possible port-based approach to connect different controller elements. Agents are control components that receive signals from and interact with neighboring agents and decide themselves to become active or not. When an agent is active it produces output signals, which can be combined with outputs of other agents to produce the final controller output(s). It is a port-based approach, because only the interface is important when making a system of agents. The contents of the agents can be of varying complexity. The concept of agents thus also supports hierarchy and polymorphic realizations. When properly implemented, adding another agent does not require complete redesign of the coordinator, but only requires an extra connection to one of the ports of the coordinator.
    In earlier work an agent-based design method for constructing a controller has been developed in the PhD-project of Van Breemen. This method results in controllers that have an open character, such that parts can be added, modified or removed without re-programming the operation of the remaining parts of the controller. In several MSc projects tools have been developed that help to apply this approach in an industrial setting. More work is to be done to make an integrated tool that fully supports the design of agent-based controllers.
    A PhD project has been started to further investigate the possibilities of agent-based controller design.

  • Measurement Science and Instrumentation

  • Description
    The role of measurement is crucial in almost any field: medical and health care, transport and trade, production and factory management, communication and navigation, space exploration and in much every day activity. Incorrect measurement results can have a tremendous economical and societal impact.
    There is a continuous demand from industry for measurement instruments with higher complexity, wider range, higher speed, smaller uncertainty, that perform better under increasingly severe environmental conditions. Upcoming technological areas like nano- and biotechnology ask for new advanced measurement equipment. In many areas measurement science becomes more and more relevant: (clinical) chemistry, safety and security, food industry.
    The research activities of the Measurement and Instrumentation Group focus on the exploration of new measurement methods for areas where information should be obtained from processes that are described only in fuzzy terms (soft measurements), or running in unstructured, randomly changing or harse environments, and to bring this knowledge into practice by cooperation with industries and other organizations.

    Ongoing work...

    Flow Measurements
    This subproject started in 1998 with a STW project with two PhD's, both graduated in 2002. From that moment, the group started research on Coriolis mass flow meters, in cooperation with a Dutch leading company in flow controllers. The success of this research resulted in further cooperation with the Dutch mechatronic company Demcon (Oldenzaal), by the payment of a new PhD researcher (AIO) in 2004.

    A tube with the flowing fluid is forced to vibrate around a defined axis. Due to Coriolis forces (which are proportional to the mass flow and in a direction perpendicular to both the flow vector and the rotation vector) the vibrations become slightly different. These very small changes (in amplitude or in phase) need be measured using sensitive displacement sensors.
    The research aims at applications for even lower mass flow ranges, as required in the semiconductor industry, and for gases. The MI Group is involved in the development of the sensing part (movements with an amplitude down to 10 nm), the signal processing and the actuation part. An in-depth analysis of the various parameters determining the sensitivity for both flow and interferences was followed by the design and evaluation of an experimental prototype, including some smart sensing and actuating principles (patents pending).

    I-Sense: Multiple sensor based systems for safety and security related applications
    This research project started at the end of 2006, and is a cooperation with the British company EX-Beams, carried out in the framework of the EU Marie Curie program.
    There is a great need today to develop solutions that enable improved levels of security and safety. The challenge of minimising risks from terrorism and detecting unexploded ordnance, explosives and illicit drugs is immense. This project aims at the development of two fully integrated technically advanced detection platforms. Current IMS technology was developed in early 70s and therefore it is a proven but relatively old technology. It has drawbacks, it is cumbersome and it is difficult to analyze large objects like suspicious trucks at ports or checkpoints. EX-Beams has a solution that is an improvement upon existing technology and materially advances IMS detection capabilities.
    Another technology, X-ray imaging, is also widely used for detecting explosives and weapons (e.g. hidden in luggage) and land mines. However the devices are bulky, expensive and dangerous for the operators. Our group has found a solution to the problem of effective X-ray imaging using low energy compact X-ray sources.

    Other projects:

    Various MSc projects were carried out in cooperation with industry. They are listed below, with a short description.

    Defect detection in steel mill rolls
    The goal of this project is to find a better method to distinguish and classify small defects in steel mill rolls. The performance of the existing sensor system should be improved so that a representative signal for the defect can be extracted.

    Measurement system for gaspipeline characterization
    As part of the project PIRATE, in this research we investigate sensing methods to assist the robot in navigating and in inspecting
    the characteristics of a gas pipeline. Basically, there will be three different external measurement systems: a measurement system for the detection of leaks, one for
    the characterization of pipelines and a third one for navigation purposes. In this MSc project emphasis is on pipe characteristics and pipe quality.

    Innovative measurement methods for power systems
    In cooperation with a Dutch company we investigate new
    concepts for the measurement of electrical parameters in power systems. These data are used for control or safety monitoring, so high accuracy and reliability are required.

    Floor scanner
    A joined project with the company RTD (Applus). RTD has developed a special service robot for the inspection of tank floors (the floor scanner). RTD likes to improve the overall performance of this tool. We investigate strategies for increasing the overall performance of the instrument, by looking to MFL (magnetic flux leakage) and Eddy currents detection methods. Objectives are to achieve higher spatial resolution, higher sensitivity (detection of smaller defects) and better characterization of defects.

    Fish flow measurements
    In the Dutch rivers and canals thousands of pumping stations, dams, locks, sluices, and other flood-controlling constructions can be found. These constructions serve our safety, but are at the same time a barrier for migrating fishes. In particular pumps and hydro-electric power stations cause the damage and death of large amount fish. To solve this problem, special constructions are being developed that allow harmless passage of these locations. In order to characterize and evaluate the performance of these migration facilities a measurement system is required enabling monitoring the fish flow at such locations. This project is a joint research with FishFlow Innovations.

      • Floor scanner
      • Innovative pump (picture Fish Flow Innovations / De Ingenieur)
  • Embedded Control Systems

  • Description
    This project deals with the realisation of control schemes on digital computers. The ultimate goal is to support the mechatronic / robotic design engineer such that implementing controllers according to “do it the first time right” becomes business as usual.
    The use of parallel hardware and parallel software is investigated, to exploit the inherent parallel nature of embedded systems and their control. Simulation and formal methods are used as a means for verification at all stages of the design process. This facilitates concurrent engineering.

    Distributed Controller architectures for mechatronic systems
    This project, being one of the six PhD-projects of the SENTER ICT–breakthrough Boderc project, deals with design and validation of distributed controller architectures, whereby an Océ printer acts as a driver. The test set-up constructed at our lab is a Hardware-in-the-Loop simulation and validation system: the controller and I/O run on the real concurrent hardware, whereas the plant (i.e. paper flowing through the copier) is either simulated, or a prototype paperpath. The stepwise refinement methodology was prototyped, and refined.

    ViewConnect: Predictable co-design for distributed embedded control systems
    This STW-PROGRESS funded project, together with the ICS/ES EE group at TU/e, deals with setting up methods and prototype tools for a multiple-view approach in mechatronic system design, using co-simulation as vehicle, with focus on embedded software. Co-simulation was tried out while constructing the Cartesian Plotter setup. The tool Ptolemy II (UC Berkely) tool was tested as integrated embedded control software design tool. The Production Cell experimental setup was controlled by integer-based control algorithms completely running on the FPGA of the I/O board, using Handel-C as intermediate language.

    Embedded Control Software architectures for Robotics
    Within this work, prototypes are tested of software architectures for robotics that are set up according to our port-based approach towards embedded control software design. Hence, we use processes interconnected by channels. This approach also structures robotics software modules according to their timing demands. In the TUlip humanoid robot, this approach is already used.

    See the Video
     

      • Plotter used in View Correct project
  • Design Tools

  • Description
    Results of research by PhD and MSc students find their way into tools for robotics and mechatronic design. Due to the cooperation with our spin-off company Controllab Products these results become globally available after some time, mostly in the form of extensions of the mechatronic design programme 20-sim.

    Ongoing work...

    20-sim
    A new release of 20-sim, version 4.0 was launched by CLP in April 2008. 20-sim has been enhanced with many new features. As proliferation of our research, models now may have multiple implementations, and the 3D mechanics, mechatronics and real-time toolboxes have been enhanced. Furthermore, the 4C tool chain now also covers ARM9 processors on embedded boards of TS-ARM. It is used in our 2nd year Mechatronics integration project. 4C covers connecting controller code to the embedded hardware, supports compilation, command and control. This is related to the research project in the Embedded Control Systems area.

    Design tools for embedded system implementation
    The purpose of this STW-PROGRESS funded Outreach project is to bring results of earlier research work on a higher level of robustness and completeness, such that these prototypes can be tested in industry. gCSP (graphical software process editor) has been extended with animation facilities, such that the flow of processes and the rendezvous exchange of data is visualized graphically. In 2008, a second Outreach project will be conducted, to enhance the tools with the newest features resulting from research.

  • Modelling and Simulation

  • Description
    The central theme of this research is an inter-disciplinary, integrated, port-based approach to the modelling of physical system behaviour in various engineering domains. It follows an energy-based approach, making extensive use of the (multi-)bond graph notation, and is subdivided in several classes of projects.
    Where applicable, the modelling activities of the laboratory are used as a basis to generate re-usable, generic (sub-) model structures of various engineering systems:
    • modelling and simulation of bouncing and/or switching objects
    • generalization of the developed approach to arbitrary spatial objects
    • modelling of rotating electric machines
    1. dissemination and generalization of earlier published work (Geoplex book; CRC Modeling Handbook edited by Paul Fishwick; CISM Advanced School Udine)
    2. thermodynamic systems. Papers on this topic, in cooperation with the Geoplex partners in Lyon were published in 2007-2008.

    Port-based approach of complex distributed-parameter system models for analysis and simulation (PACDAS, STW-TWI.6012)
    This project, funded by STW, is in cooperation with the Systems and Control Group at the Department of Mathematics. One PhD student, Norbert Ligterink, started in September 2003 on the project, and Goran Golo was a postdoc from February till December 2003. From January 2006, Damien Eberard, a postdoc from France, joined the project. He works mainly in Groningen, in the new Applied Analysis Group of Arjan van der Schaft started September 2005.

    The research aim of the project is to create a synthesis between two successful approaches to modelling and simulation of physical engineering systems: the finite element approach to distributed-parameter system models, and the multi-physics port-based approach to lumped system models. The purpose is the marriage of the accuracy and power of finite element methods (FEM), with the versatility, dynamics, and control of port-based modelling.
    There are several aspects to this synthesis:

    • the port-based formulation of continuous, or distributed, systems, such that the dynamics can adapt the changing boundary conditions, i.e., port input.
    • a general geometric Hamiltonian formulation, such that flow, effort, and power conservation are exact, for a systematic approach, which can extend to several physics domains, which, e.g., eventually should yield proper models for damping.
    • model reduction methods, which can handle the configuration dependent dynamics, such as pre-strain, or varying load, where the essential dynamics of a distributed element is retained for a simulation, without the numerical effort of FEM.
    • a library of segments (beam, plate, solids, etc.), material properties (conductance, rigidity, etc.), and port-types (welding, screws, airgap) which are the basis for continuous dynamics simulation in 20-sim.

    Some more examples of the PACDAS project
    Dynamics of nonlinear Hamiltonians
    A Hamiltonian of an elastic beam is given as a polynomial with about 220 terms, to fourth order. The system can be used to find a minimal, or static, solution, using dissipation, which is the Control-Engineering version of a Conjugate Gradient approach.

    The same Hamiltonian and the same state can be used for a dynamical simulation, which conserves energy, not explicitly, but to 5 decimal places for 3000 time steps.

    The code is written in C, and uses the libraries of libplot and lapack. It consists of two separate codes:

    1. the generation of the Hamiltonian, written as a data file,
    2. the simulation of the Hamiltonian, with stepsize and damping, and multiple data output.

    The evaluation (functional derivative) costs about three times the total number of factors in the Hamiltonian in floating-point operations. The improved integration step using the last and previous gradients. The simulation tests for stepsize errors, by calculating the energy in the system. The simulations above take only seconds to run, where I/O account for most of the computing time.

    Geoplex
    The goal of the EU-sponsored project GeoPleX was to develop methods and software tools to help in the modelling, analysis, and control of complex physical systems in several physical domains. The project is done by partners all over Europe; one of these partners is the Systems and Control Group at the Department of Mathematics. Since energy often plays an important role in these systems, the starting point for the development is the concept of a Port-Controlled Hamiltonian system, in which the energy structure is shown explicitly.
    The Geoplex project was finished in 2006. A book that gives an overview of the Geoplex research will be published in 2008 by Springer.

      • The black lines represent the resultant forces on the boundary nodes. Eventually, the sum force is zero
      • One end of the beam is suddenly released from the clamped boundary conditions. The bending dynamics is generally much slower than the longitudinal vibration dynamics
  • Advanced Robotics and Mechatronics

  • Description
    This research program focuses towards robotics applications being a quickly rising multidisciplinary market and challenging research field. The structure of the research activities can be pictured using a matrix structure in which the columns represent the robotics application fields and the rows the embedding technologies.

    The chair Advanced Robotics is part of the 3TU Center of Excellence on Intelligent Mechatronic Systems for its activities and expertise in the Robotics field. The research of Control Engineering is carried out in the IMPACT and CTIT Institutes.
    One unique and characterizing feature of the philosophy with which research is performed is the use of the `port based’ way of thinking like bond graphs and port Hamiltonian systems for the modeling and control of multi-domain systems.
    Two Humanoids projects are carried on: one together with the 3TU and Philips and one at the Institute level in collaboration with Demcon.
    Strong collaborations with the Mechatronic Valley Twente and national industries like Philips, TNO, ESA, OCE, Thales are taking place.

     

    Ongoing work...

    Humanoid Robotics

    The groups dream is to build a fully functional humanoid robot in the next decade. With this purpose, the group is putting effort in doing research on different parts of humanoids. In particular, in the last year, the group has been working on the development of a humanoid head-neck system, a dexterous robotic hand, an energy efficient knee locking mechanisms and, finally, by continuing on earlier work of the group, extended knowledge on bipedal walking. The complete humanoid project realizes a really multidisciplinary platform which requires the close collaboration with other Departments and Faculties of the University of Twente, in particular with the Mechanical Engineering and Industrial Design. Moreover, in this context, the group has extended the collaboration network with various companies of the Mechatronic Valley Twente and the research groups of the other technical Universities of The Netherlands.

    Humanoid walking
    The group believes that a thorough understanding of 3D dynamics is the key issue for the design of robust and energy efficient walking algorithms. For this reason, PhD student Gijs van Oort has worked on model simplification using geometrical insights. The aim is finding mathematical ways to convert generalized-coordinate models to models with only a few meaningful 'coordinates'.
    Several MSc. projects on walking theory were successfully finished: combination of dynamic walking and ZMP walking and non-linear energy-conservative oscillators to implement walking structures. Innovative locking mechanism will be implemented in the bipedal walker Dribbel.
    In collaboration with TU Delft, TU Eindhoven and Philips, the initiative "Dutch Robotics", which aims at working closely together in this field has been started. The first big project, building the soccer-robot TULIP, got much momentum this year by participating in the RoboCup World Championship in China. It has been worked on software architecture of the robot.

    As walking requires oscillatory behavior of the legs, and therefore of the actuators attached to the legs, it makes sense to choose actuators that are well-equipped for this job. Unfortunately, electric motors as well as other conventional actuators behave very badly in this type of actuation: they consume a lot of energy and are not able to store negative work done during part of the oscillatory cycle. The solution may lie in the development of variable impedance actuators. In the context of variable impedance actuators, a European project (in FP7), called VIActors has been financed. As a preliminary study on this topic, a novel type of infinitely variable transmission (which is a part of a variable impedance actuator) has been developed.

    Humanoid head
    As a separate track, a humanoid head-neck has been developed. The system realizes a multidisciplinary platform interesting from mechanical, control and human-machine interaction point of view. The project has been done in collaboration with Demcon, a hi-tech company situated in Oldenzaal. The humanoid head has 7 degrees of freedom (four in the neck and three in the eyes) and reacts in a human-like way to its environment (e.g. it looks around, using saccades, dynamically searching for interesting things to look at). The external design and implementation of expression by means of light projection from the interal part have taken place. Together with the UT research group Human Media Interaction, the group is now working on improving the behavior, in order to integrate speech recognition and synthesis, audio interaction and human-like emotions.

    Falcon
    This project in collaboration with ESI and Van der Lande Industries is concerned with in the realization of a robotic system for the manipulation and composition of orders in a distribution center. The research will be twofold. On one hand a variable impedance dexterous hand will be developed which should be able to robustly and dexterously to grasp object both via power grasps and with tips grasps, depending on the geometry. The other part of the project is dedicated to visual servoing of the arm-hand system.

    Medical Robotics

    Tele-manipulation
    As surgical techniques are becoming less invasive (MIS procedures) for the patient, they are becoming more complex for the surgeon. For this reason the medical community looks towards the possibilities of robotics to alleviate this complexity. The “Da Vinci Surgical System” by Intuitive Surgical Inc. has demonstrated that by means of a tele-manipulation system the complexity of interpreting the surgical field and making the desired movements can be greatly simplified.
    A drawback of all MIS procedures is the loss of “touch” of the surgeon. He is either manipulating the operation scene from a remote location, or through long laparoscopic instruments. Studies have shown that the surgeon is capable of performing the operation with less trauma to the surrounding tissue if his sense of force is restored.
    A common aspect which greatly complicates the design of such a bilateral control loop is time delay in the communication channel. Many algorithms for these bilateral control loops exist, which either offer good stability properties with respect to time delay and poor transparency or vice versa.
    In this research project a new approach to the design of bilateral control loops will be studied which aims at good stability properties and a maximum achievable transparency under arbitrary time delays based on energy exchange considerations. A first MSc project in this field was carried out by B. Babakhani, MSc and M.C.J. Franken, MSc is pursuing his PhD in this direction.
    Natural Orifice Transluminal Endoscopic Surgery
    Natural orifice transluminal endoscopic surgery (NOTES) is a new form of minimally invasive surgery (MIS). The main difference between NOTES and traditional MIS is that the operating scene is entered through one of the natural openings of the human body. In April 2007 the first true NOTES operation was presented at the Japanese Congress of Surgery in Osaka. The operation consisted of the removal of the gall bladder (cholecystectomy) in a 30-year-old woman and was carried out transvaginal [1].

    NOTES is expected to have several benefits over traditional MIS. The most important benefit would be that even less damage is inflicted on the patient during the operation. This means that he suffers less from postoperative pain and will return to his daily life at an earlier stage. Also MIS operations can be performed on patients who suffer from severe obesity (which is problematic for traditional MIS), or from inflictions to the abdomen.
    The approach to surgery using NOTES techniques greatly differs from current laparoscopic techniques. For a successful introduction of NOTES in the OR, robotic tele-manipulation will be a key ingredient. The tele-manipulation device will have to empower the surgeon to carry out various kinds of common diagnostic and therapeutic procedures in a time efficient and cost effective manner.
    The TeleFlex project consisting of four PhD positions, of which two at the CE group, has started in the past year in this upcoming research field. The focus of the TeleFlex project is directed at the master device of the tele-manipulation chain. R. Reilink, MSc. will do research on the effects haptic feedback has on a sentient surgeon and under which conditions this feedback will benefit the surgeon. M. Bezemer, MSc will focus on the software structure and how layered software should be designed to guarantee safety.

    LOPES
    This project, has been concerned with the realization of a lower extremities exoskeleton for the rehabilitation of stroke patients. The project, financed by NWO, is coordinated by Herman van der Kooij and has involved 3 Ph.D. students one of which in the Control Engineering group.

    REFLEXLEG
    In this project, financed by STW, a new transfemoral prosthesis will be developed which will have energetic advantages with respect to existing ones. This project involves 2 Ph.D. students and is carried out in collaboration with the group of Prof. Velting and the Roessing R&D center.
     

    Inspection Robotics

    PIRATE
    In 2007 a mobile inspection system for live gas mains has been developed. This project is a joint effort of Continuon Netbeheer, Kiwa Gastec Technology B.V. and the University of Twente. The prototype hardware has been developed at DEMCON. The robot is developed for autonomous internal inspection of the low pressure gas mains, with minimal intervention of human operators. The robot will be used to detect leaks or possible weak points in the gas mains.

    In the first stage of this project, the development of a moving mobile robot base has been emphasized. The low pressure net in the Netherlands uses pipes with an inner diameter as small as 50 mm, thus putting a severe limitation on the robot's size. A mechanical prototype has been developed which is capable of moving through pipes ranging in diameter from 50 to 120 mm. It can move through mitered bends and T-joints and take inclinations of 30 degrees. The robot has the form of a 'snake', consisting of seven wheeled modules which all have a designated function. Two modules are used for propulsion, two for bending the robot's shape (for navigation trough bends), one module in the center for rotation the robot around its axis, one module for power storage and one module for control and sensor electronics. The mechanical setup has been tested in a structured lab environment. The next step will be to test the functionality in a more realistic environment.

    On a different level work has been done on the design of a camera setup with structured light bundle (laser projecting circles) which can be used as sensor to measure pipe deformation, and which also can be used to detect obstacles and bends which is necessary for navigation. In following projects we hope to miniaturize this setup in order to integrate it into the robot's design.

    Exomars
    In this project carried out in collaboration with ESA, the modeling of altitude maps and their use in the prediction of the navigation of the ExoMars rover is considered. Problems which arise in this study relate a combination of sparse altitude data with precise terramechanics simulations. This is tackled using a hybrid use of differential geometric techniques and computational geometric methods.

    • Soccer robot Tulip
    • Humanoid head
    • Humanoid head
  • Intelligent Control

  • Description
    This project investigates the possibilities of adaptive and learning control systems. Special attention is paid to (feed-forward) learning control systems, based on neural networks. Agent-based control systems are studied as a port-base approach to controller design.

    Ongoing work...

    Model-reference-based learning feed-forward control
    Most work on learning feed-forward control has been on done on compensation of non-linear effects, requiring more or less complex function approximators. However, for unkown or time-variable linear systems the inverse of the process transfer function can efficiently be described by means of a simple linear transfer function. A learning feed-forward control scheme has been developed based on the philosophy of stable model-reference adaptive systems. It appears that this system is very robust against a mismatch of the order of the process and the inverse model. In addition, it has a low sensitivity for noise. Future work will be to investigate if this scheme that has superior performance for dealing with unknown or time-varying process dynamics can be combined with e.g. the KSM scheme that is successful in dealing with the non-linearities in a process.
    A comparison has been made between different learning and adaptive control systems to identify the stronger and weaker points of each method. Experiments have been carried out on the "Mechatronic Demonstrator


    Agent-based controller design
    For control algorithms a port-based approach is less well developed. Such an approach would make controllers more modular and would contribute to reusable controller components and quicker developments. From a control-engineering point of view a controller is often considered as containing the control algorithms only. But in practice the control algorithm is only a small part of total software used to safely start up, control and shut down the system. Error detection, error handling and graceful degradation are issues here. These parts of the controller can often be reused from earlier projects. Using agents is a possible port-based approach to connect different controller elements. Agents are control components that receive signals from and interact with neighboring agents and decide themselves to become active or not. When an agent is active it produces output signals, which can be combined with outputs of other agents to produce the final controller output(s). It is a port-based approach, because only the interface is important when making a system of agents. The contents of the agents can be of varying complexity. The concept of agents thus also supports hierarchy and polymorphic realizations. When properly implemented, adding another agent does not require complete redesign of the coordinator, but only requires an extra connection to one of the ports of the coordinator.
    In earlier work an agent-based design method for constructing a controller has been developed in the PhD-project of Van Breemen. This method results in controllers that have an open character, such that parts can be added, modified or removed without re-programming the operation of the remaining parts of the controller. In several MSc projects tools have been developed that help to apply this approach in an industrial setting. More work is to be done to make an integrated tool that fully supports the design of agent-based controllers.
    A PhD project has been started to further investigate the possibilities of agent-based controller design.

  • Measurement Science and Instrumentation

  • Description
    The role of measurement is crucial in almost any field: medical and health care, transport and trade, production and factory management, communication and navigation, space exploration and in much every day activity. Incorrect measurement results can have a tremendous economical and societal impact.
    There is a continuous demand from industry for measurement instruments with higher complexity, wider range, higher speed, smaller uncertainty, that perform better under increasingly severe environmental conditions. Upcoming technological areas like nano- and biotechnology ask for new advanced measurement equipment. In many areas measurement science becomes more and more relevant: (clinical) chemistry, safety and security, food industry.
    The research activities of the Measurement and Instrumentation Group focus on the exploration of new measurement methods for areas where information should be obtained from processes that are described only in fuzzy terms (soft measurements), or running in unstructured, randomly changing or harse environments, and to bring this knowledge into practice by cooperation with industries and other organizations.

    Ongoing work...

    Flow Measurements
    This subproject started in 1998 with a STW project with two PhD's, both graduated in 2002. From that moment, the group started research on Coriolis mass flow meters, in cooperation with a Dutch leading company in flow controllers. The success of this research resulted in further cooperation with the Dutch mechatronic company Demcon (Oldenzaal), by the payment of a new PhD researcher (AIO) in 2004.

    A tube with the flowing fluid is forced to vibrate around a defined axis. Due to Coriolis forces (which are proportional to the mass flow and in a direction perpendicular to both the flow vector and the rotation vector) the vibrations become slightly different. These very small changes (in amplitude or in phase) need be measured using sensitive displacement sensors.
    The research aims at applications for even lower mass flow ranges, as required in the semiconductor industry, and for gases. The MI Group is involved in the development of the sensing part (movements with an amplitude down to 10 nm), the signal processing and the actuation part. An in-depth analysis of the various parameters determining the sensitivity for both flow and interferences was followed by the design and evaluation of an experimental prototype, including some smart sensing and actuating principles (patents pending).

    I-Sense: Multiple sensor based systems for safety and security related applications
    This research project started at the end of 2006, and is a cooperation with the British company EX-Beams, carried out in the framework of the EU Marie Curie program.
    There is a great need today to develop solutions that enable improved levels of security and safety. The challenge of minimising risks from terrorism and detecting unexploded ordnance, explosives and illicit drugs is immense. This project aims at the development of two fully integrated technically advanced detection platforms. Current IMS technology was developed in early 70s and therefore it is a proven but relatively old technology. It has drawbacks, it is cumbersome and it is difficult to analyze large objects like suspicious trucks at ports or checkpoints. EX-Beams has a solution that is an improvement upon existing technology and materially advances IMS detection capabilities.
    Another technology, X-ray imaging, is also widely used for detecting explosives and weapons (e.g. hidden in luggage) and land mines. However the devices are bulky, expensive and dangerous for the operators. Our group has found a solution to the problem of effective X-ray imaging using low energy compact X-ray sources.

    Other projects:

    Various MSc projects were carried out in cooperation with industry. They are listed below, with a short description.

    Defect detection in steel mill rolls
    The goal of this project is to find a better method to distinguish and classify small defects in steel mill rolls. The performance of the existing sensor system should be improved so that a representative signal for the defect can be extracted.

    Measurement system for gaspipeline characterization
    As part of the project PIRATE, in this research we investigate sensing methods to assist the robot in navigating and in inspecting
    the characteristics of a gas pipeline. Basically, there will be three different external measurement systems: a measurement system for the detection of leaks, one for
    the characterization of pipelines and a third one for navigation purposes. In this MSc project emphasis is on pipe characteristics and pipe quality.

    Innovative measurement methods for power systems
    In cooperation with a Dutch company we investigate new
    concepts for the measurement of electrical parameters in power systems. These data are used for control or safety monitoring, so high accuracy and reliability are required.

    Floor scanner
    A joined project with the company RTD (Applus). RTD has developed a special service robot for the inspection of tank floors (the floor scanner). RTD likes to improve the overall performance of this tool. We investigate strategies for increasing the overall performance of the instrument, by looking to MFL (magnetic flux leakage) and Eddy currents detection methods. Objectives are to achieve higher spatial resolution, higher sensitivity (detection of smaller defects) and better characterization of defects.

    Fish flow measurements
    In the Dutch rivers and canals thousands of pumping stations, dams, locks, sluices, and other flood-controlling constructions can be found. These constructions serve our safety, but are at the same time a barrier for migrating fishes. In particular pumps and hydro-electric power stations cause the damage and death of large amount fish. To solve this problem, special constructions are being developed that allow harmless passage of these locations. In order to characterize and evaluate the performance of these migration facilities a measurement system is required enabling monitoring the fish flow at such locations. This project is a joint research with FishFlow Innovations.

      • Floor scanner
      • Innovative pump (picture Fish Flow Innovations / De Ingenieur)
  • Embedded Control Systems

  • Description
    This project deals with the realisation of control schemes on digital computers. The ultimate goal is to support the mechatronic / robotic design engineer such that implementing controllers according to “do it the first time right” becomes business as usual.
    The use of parallel hardware and parallel software is investigated, to exploit the inherent parallel nature of embedded systems and their control. Simulation and formal methods are used as a means for verification at all stages of the design process. This facilitates concurrent engineering.

    Distributed Controller architectures for mechatronic systems
    This project, being one of the six PhD-projects of the SENTER ICT–breakthrough Boderc project, deals with design and validation of distributed controller architectures, whereby an Océ printer acts as a driver. The test set-up constructed at our lab is a Hardware-in-the-Loop simulation and validation system: the controller and I/O run on the real concurrent hardware, whereas the plant (i.e. paper flowing through the copier) is either simulated, or a prototype paperpath. The stepwise refinement methodology was prototyped, and refined.

    ViewConnect: Predictable co-design for distributed embedded control systems
    This STW-PROGRESS funded project, together with the ICS/ES EE group at TU/e, deals with setting up methods and prototype tools for a multiple-view approach in mechatronic system design, using co-simulation as vehicle, with focus on embedded software. Co-simulation was tried out while constructing the Cartesian Plotter setup. The tool Ptolemy II (UC Berkely) tool was tested as integrated embedded control software design tool. The Production Cell experimental setup was controlled by integer-based control algorithms completely running on the FPGA of the I/O board, using Handel-C as intermediate language.

    Embedded Control Software architectures for Robotics
    Within this work, prototypes are tested of software architectures for robotics that are set up according to our port-based approach towards embedded control software design. Hence, we use processes interconnected by channels. This approach also structures robotics software modules according to their timing demands. In the TUlip humanoid robot, this approach is already used.

    See the Video
     

      • Plotter used in View Correct project
  • Design Tools

  • Description
    Results of research by PhD and MSc students find their way into tools for robotics and mechatronic design. Due to the cooperation with our spin-off company Controllab Products these results become globally available after some time, mostly in the form of extensions of the mechatronic design programme 20-sim.

    Ongoing work...

    20-sim
    A new release of 20-sim, version 4.0 was launched by CLP in April 2008. 20-sim has been enhanced with many new features. As proliferation of our research, models now may have multiple implementations, and the 3D mechanics, mechatronics and real-time toolboxes have been enhanced. Furthermore, the 4C tool chain now also covers ARM9 processors on embedded boards of TS-ARM. It is used in our 2nd year Mechatronics integration project. 4C covers connecting controller code to the embedded hardware, supports compilation, command and control. This is related to the research project in the Embedded Control Systems area.

    Design tools for embedded system implementation
    The purpose of this STW-PROGRESS funded Outreach project is to bring results of earlier research work on a higher level of robustness and completeness, such that these prototypes can be tested in industry. gCSP (graphical software process editor) has been extended with animation facilities, such that the flow of processes and the rendezvous exchange of data is visualized graphically. In 2008, a second Outreach project will be conducted, to enhance the tools with the newest features resulting from research.