Vision-Based Control of Flexible Robot Systems

This thesis covers the controlling of flexible robot systems by using a camera as a measurement device. To accomplish the purpose of the study, the estimation process of dynamic state variables of flexible link robot has been examined based on camera measurements. For the purpose of testing two application examples for flexible link have been applied, an algorithm for the dynamic state variables estimation is proposed. Flexible robots can have very complex dynamic behavior during their operations, which can lead to induced vibrations. Since the vibrations and its derivative are not all measurable, therefore the estimation of state variables plays a significant role in the state feedback control of flexible link robots. A vision sensor (i.e. camera) realizing a contact-less measurement sensor can be used to measure the deflection of flexible robot arm. Using a vision sensor, however, would generate new effects such as limited accuracy and time delay, which are the main inherent problems of the application of vision sensors within the context. These effects and related compensation approaches are studied in this thesis. An indirect method for link deflection (i.e. system states) sensing is presented. It uses a vision system consisting of a CCD camera and an image processing unit. The main purpose of this thesis is to develop an estimation approach combining suitable measurement devices which are easy to realize with improved reliability. It includes designing two state estimators; the first one for the traditional sensor type (negligible noise and time delay) and the second one is for the camera measurement which account for the dynamic error due to the time delay. The estimation approach is applied first using a single link flexible robot; the dynamic model of the flexible link is derived using a finite element method. Based on the suggested estimation approach, the first observer estimates the vibrations using strain gauge (fast and complete dynamics), and the second observer estimates the vibrations using vision data (slow dynamical parts). In order to achieve an optimal estimation, a proper combination process of the two estimated dynamical parts of the system dynamics is described. The simulation results for the estimations based on vision measurements show that the slow dynamical states can be estimated and the observer can compensate the time delay dynamic errors. It is also observed that an optimal estimation can be attained by combining slow dynamical estimated states with those of fast observer-based on strain gauge measurement. Based on suggested estimation approach a vision-based control for elastic shipmounted crane is designed to regulate the motion of the payload. For the observers and the controller design, a linear dynamic model of elastic-ship mounted crane incorporating a finite element technique for modeling flexible link is employed. In order to estimate the dynamic states variables and the unknown disturbance two state observers are designed. The first one estimates the state variables using camera measurement (augmented Kalman filter). The second one used potentiometers measurement (PI-Observer). To realize a multi-model approach of elastic-ship mounted crane, a variable gain controller and variable gain observers are designed. The variable gain controller is used to generate the required damping to control the system based on the estimated states and the roll angle. Simulation results show that the variable gain observers can adequately estimate the states and the unknown disturbance acting on the payload. It is further observed that the variable gain controller can effectively reduce the payload pendulations. Experiments are conducted using the camera to measure the link deflection of scaled elastic ship-mounted crane system. The results shown that the variable gain controller based on the combined states observers mitigated the vibrations of the system and the swinging of the payload. The presented material above is embedded into an interrelated thesis. A concise introduction to the vision-based control and state estimation problems is attached in the first chapter. An extensive survey of available visual servoing algorithms that include the rigid robot system and the flexible robot system is also presented. The conclusions of the work and suggestions for the future research are provided at the last chapter of this thesis

Proceedings of the 4th Baltic Mechatronics Symposium - Tallinn April 25, 2019

The Baltic Mechatronics Symposium is annual symposium with the objective to provide a forum for young scientists from Baltic countries to exchange knowledge, experience, results and information in large variety of fields in mechatronics. The symposium was organized in co-operation with Taltech and Aalto University. The venue of the symposium was Nordic Hotel Forum Tallinn.The symposium was organized parallel to the 12th International DAAAM Baltic Conference and 27th International Baltic Conference BALTMATTRIB 2019. The selected papers are published in Proceedings of Estonian Academy of Sciences indexed in ISI Web of Science. The content of the proceedings: 1. Continuous wet spinning of cellulose nanofibrils 2. Development of motor efficiency test setup for direct driven hydraulic actuator 3. Development of pressure former for continuous nanopaper manufacturing 4. Device for tree volume measurements 5. Effect of external load on rotor vibration 6. Granular jamming based gripper for heavy objects 7. Integrated car camera system for monitoring inner cabin and outer traffic 8. Inverted pendulum controlled with CNC control system 9. Multi-material mixer and extruder for 3D printing 10. Object detection and trajectory planning using a LIDAR for an automated overhead cran

An intelligent, free-flying robot

The ground based demonstration of the extensive extravehicular activity (EVA) Retriever, a voice-supervised, intelligent, free flying robot, is designed to evaluate the capability to retrieve objects (astronauts, equipment, and tools) which have accidentally separated from the Space Station. The major objective of the EVA Retriever Project is to design, develop, and evaluate an integrated robotic hardware and on-board software system which autonomously: (1) performs system activation and check-out; (2) searches for and acquires the target; (3) plans and executes a rendezvous while continuously tracking the target; (4) avoids stationary and moving obstacles; (5) reaches for and grapples the target; (6) returns to transfer the object; and (7) returns to base

Engineering Dynamics and Life Sciences

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”

Acoustic Emission Monitoring of Prefabricated and Prestressed Reinforced Concrete Bridge Elements and Structures

Prefabricated and pre-stressed reinforced concrete beams and girders are integral components of many highway structures, including those build by rapid construction techniques. Concerns exist regarding the development of cracks during curing, form removal, detensioning, transport, installation, and operation. Non-destructive, Acoustic Emission (AE) sensing techniques have the potential for detecting and locating cracking in prefabricated, prestressed concrete girders used as Prefabricated Bridge Elements and Systems (PBES) in rapid construction practices as part of a Quality Assurance/Quality Control (QA/QC) program. AE sensing records transient elastic waves produced by the release of stored elastic energy resulting in plastic deformations (i.e., crack nucleation and growth) with an array of point sensors. The AE instrument system is relatively portable which can allow for it to be an option for both off-site fabrication QA/QC as well as on-site field QA/QC. This report presents a multi-stage research initiative on acoustic emission measurements of prefabricated and pre-stressed concrete beams used in highway bridge construction during detensioning, craned removal from formwork and transport to bridge sites, along with supporting laboratory tests and numerical analysis. The project objectives are: 1. Identify suitable instruments to monitor pre-stressed and/or post-tensioned concrete girders for cracking activity; 2. Design and develop a reusable instrumentation package; 3. Measure performance and condition of concrete girders during fabrication and transport; 4. Identify test protocols and possible accept/fix/reject criteria for structural elements based on information from monitoring system; and 5. Develop plans for reusing monitoring instruments on multiple bridge projects. Presented are results from laboratory, full-scale girder fabrication, and transport monitoring, along with recommendations for future testing procedures and quality assurance protocol development

Acoustic Emission Sensing for Crack Monitoring in Prefabricated and Prestressed Reinforced Concrete Bridge Girders

Prefabricated and pre-stressed reinforced concrete beams and girders are integral components of many highway structures, including those built by rapid construction techniques. Concerns exist regarding the development of cracks during curing, form removal, detensioning, transport, installation, and operation. Non-destructive, Acoustic Emission (AE) sensing techniques have the potential for detecting and locating cracking in prefabricated, pre-stressed concrete girders used as Prefabricated Bridge Elements and Systems (PBES) used in rapid construction practices as part of a Quality Assurance/Quality Control (QA/QC) program. AE sensing records transient elastic waves produced by the release of stored elastic energy resulting in plastic deformations (i.e., crack nucleation and growth) with an array of point sensors. The AE instrument system is relatively portable which can allow for it to be an option for both off-site fabrication QA/QC as well as on-site field QA/QC. This thesis presents a multi-stage research initiative on acoustic emission monitoring of prefabricated and pre-stressed reinforced concrete beams used in highway bridge construction during detensioning, craned removal from formwork and transport to bridge sites, along with supporting laboratory tests and numerical analysis. The specific objectives of this research were to: 1. Identify suitable instruments to monitor pre-stressed and/or post-tensioned concrete girders for cracking activity; 2. Design and develop a reusable instrumentation package; 3. Measure performance and condition of concrete girders during fabrication and transport; and 4. Identify test protocols and possible accept/fix/reject criteria for structural elements based on information from monitoring system. Presented are results from laboratory, full-scale girder fabrication, and transport monitoring, along with overall conclusions and recommendations for future research

From plain visualisation to vibration sensing: using a camera to control the flexibilities in the ITER remote handling equipment

Thermonuclear fusion is expected to play a key role in the energy market during the second half of this century, reaching 20% of the electricity generation by 2100. For many years, fusion scientists and engineers have been developing the various technologies required to build nuclear power stations allowing a sustained fusion reaction. To the maximum possible extent, maintenance operations in fusion reactors are performed manually by qualified workers in full accordance with the "as low as reasonably achievable" (ALARA) principle. However, the option of hands-on maintenance becomes impractical, difficult or simply impossible in many circumstances, such as high biological dose rates. In this case, maintenance tasks will be performed with remote handling (RH) techniques. The International Thermonuclear Experimental Reactor ITER, to be commissioned in southern France around 2025, will be the first fusion experiment producing more power from fusion than energy necessary to heat the plasma. Its main objective is “to demonstrate the scientific and technological feasibility of fusion power for peaceful purposes”. However ITER represents an unequalled challenge in terms of RH system design, since it will be much more demanding and complex than any other remote maintenance system previously designed. The introduction of man-in-the-loop capabilities in the robotic systems designed for ITER maintenance would provide useful assistance during inspection, i.e. by providing the operator the ability and flexibility to locate and examine unplanned targets, or during handling operations, i.e. by making peg-in-hole tasks easier. Unfortunately, most transmission technologies able to withstand the very specific and extreme environmental conditions existing inside a fusion reactor are based on gears, screws, cables and chains, which make the whole system very flexible and subject to vibrations. This effect is further increased as structural parts of the maintenance equipment are generally lightweight and slender structures due to the size and the arduous accessibility to the reactor. Several methodologies aiming at avoiding or limiting the effects of vibrations on RH system performance have been investigated over the past decade. These methods often rely on the use of vibration sensors such as accelerometers. However, reviewing market shows that there is no commercial off-the-shelf (COTS) accelerometer that meets the very specific requirements for vibration sensing in the ITER in-vessel RH equipment (resilience to high total integrated dose, high sensitivity). The customisation and qualification of existing products or investigation of new concepts might be considered. However, these options would inevitably involve high development costs. While an extensive amount of work has been published on the modelling and control of flexible manipulators in the 1980s and 1990s, the possibility to use vision devices to stabilise an oscillating robotic arm has only been considered very recently and this promising solution has not been discussed at length. In parallel, recent developments on machine vision systems in nuclear environment have been very encouraging. Although they do not deal directly with vibration sensing, they open up new prospects in the use of radiation tolerant cameras. This thesis aims to demonstrate that vibration control of remote maintenance equipment operating in harsh environments such as ITER can be achieved without considering any extra sensor besides the embarked rad-hardened cameras that will inevitably be used to provide real-time visual feedback to the operators. In other words it is proposed to consider the radiation-tolerant vision devices as full sensors providing quantitative data that can be processed by the control scheme and not only as plain video feedback providing qualitative information. The work conducted within the present thesis has confirmed that methods based on the tracking of visual features from an unknown environment are effective candidates for the real-time control of vibrations. Oscillations induced at the end effector are estimated by exploiting a simple physical model of the manipulator. Using a camera mounted in an eye-in-hand configuration, this model is adjusted using direct measurement of the tip oscillations with respect to the static environment. The primary contribution of this thesis consists of implementing a markerless tracker to determine the velocity of a tip-mounted camera in an untrimmed environment in order to stabilise an oscillating long-reach robotic arm. In particular, this method implies modifying an existing online interaction matrix estimator to make it self-adjustable and deriving a multimode dynamic model of a flexible rotating beam. An innovative vision-based method using sinusoidal regression to sense low-frequency oscillations is also proposed and tested. Finally, the problem of online estimation of the image capture delay for visual servoing applications with high dynamics is addressed and an original approach based on the concept of cross-correlation is presented and experimentally validated

Modeling and Control of the Automated Radiator Inspection Device

Many of the operations performed at the Kennedy Space Center (KSC) are dangerous and repetitive tasks which make them ideal candidates for robotic applications. For one specific application, KSC is currently in the process of designing and constructing a robot called the Automated Radiator Inspection Device (ARID), to inspect the radiator panels on the orbiter. The following aspects of the ARID project are discussed: modeling of the ARID; design of control algorithms; and nonlinear based simulation of the ARID. Recommendations to assist KSC personnel in the successful completion of the ARID project are given

Protocols for calibrating multibeam sonar

Development of protocols for calibrating multibeam sonar by means of the standard-target method is documented. Particular systems used in the development work included three that provide the water-column signals, namely the SIMRAD SM2000/90- and 200-kHz sonars and RESON SeaBat 8101 sonar, with operating frequency of 240 kHz. Two facilities were instrumented specifically for the work: a sea well at the Woods Hole Oceanographic Institution and a large, indoor freshwater tank at the University of New Hampshire. Methods for measuring the transfer characteristics of each sonar, with transducers attached, are described and illustrated with measurement results. The principal results, however, are the protocols themselves. These are elaborated for positioning the target, choosing the receiver gain function, quantifying the system stability, mapping the directionality in the plane of the receiving array and in the plane normal to the central axis, measuring the directionality of individual beams, and measuring the nearfield response. General preparations for calibrating multibeam sonars and a method for measuring the receiver response electronically are outlined. Advantages of multibeam sonar calibration and outstanding problems, such as that of validation of the performance of multibeam sonars as configured for use, are mentioned