Advanced control designs for output tracking of hydrostatic transmissions

The work addresses simple but efficient model descriptions in a combination with advanced control and estimation approaches to achieve an accurate tracking of the desired trajectories. The proposed control designs are capable of fully exploiting the wide operation range of HSTs within the system configuration limits. A new trajectory planning scheme for the output tracking that uses both the primary and secondary control inputs was developed. Simple models or even purely data-driven models are envisaged and deployed to develop several advanced control approaches for HST systems

Sensitivity optimization method for 4th order CBQ structure LP filter

This paper describes the design and optimization method for a 4th order low-pass filter designed as a cascade of biquarts and approximated by Butterworth. Schoeffler sensitivity, multiparameter sensitivity measurement, and Monte Carlo analysis were used for sensitivity measurement, filter tuning, and optimization confirmation. The constraints on the filter characteristics due to the Butterworth approximation are also presented, together with the constraints on optimization to obtain a narrow range of values for the filter elements. Three different types of optimization parameters were used to confirm the optimization method. Finally, a 4th order low pass filter with a cascade structure of biquarts was compared to a 4th order filter without feedback and confirmed to have lower sensitivity

Component-based mixed reality environment for the control and design of servo-pneumatic system

Synopsis Considerable research efforts have been spent over the last two decades on improving the design, control, and modelling of pneumatic servo drive systems including the development of dedicated controllers and control valves. However, the commercial updates in employing pneumatic servos are still largely limited to laboratory research usage and the initiatives in developing seem to have lost their momentums. Although this situation has some to do with the rapid development and availability of cost effective electric servo technologies, one reason is considered to be a lack of design and simulation tools for employing pneumatic servo drives. This research has therefore been conducted to address these concerns, and to demonstrate how appropriate tools and environments can be developed and used to aid in the design, control and commissioning of pneumatic servo drives. Because of the inherent high nonlinearities associated with pneumatic systems, it would be highly desirable if the simulation environment could be run in time domain so that it can be mixed with the real system. This would make the simulation more accurate and reliable especially when dealing with such nonlinear systems. Unfortunately, the tools that are available in the market such as Propneu (Festo, 2005) and Hypneu (Bardyne, 2006) are dedicated for pneumatic circuit design only. This research is aimed at developing a mixed reality environment for the control and design of servo-pneumatic systems. Working with a mixed reality environment would include both the capability to model the system entirely as a simulation, the so-called "off-line", as well as being able to use real components running against simulations of others "on-line", or in a Mixed Reality (MR) manner. Component-based paradigm has been adopted, and hence the entire pneumatic system is viewed as a series of component modules with standardised linking variables. The mathematical model of each individual component has been implemented in simulation software which produces time domain responses in order to allow for mixing the simulation with the real system. The main outcome of this research can be seen as a successful development and demonstration of the Component-based Mixed Reality Environment (CMRE), which would facilitate the control and design of servo-pneumatic systems. On the one hand, the CMRE facilitates the identification of some nonlinear parameters such as frictional \I ynopsis parameters. These parameters could cause great difficulties in servo-pneumatic modelling and control. Accurate friction parameters would give the ability to attain an accurate model, and therefore provide more flexibility in applying different control and tuning strategies on the real system. On the other hand, the CMRE facilitates the design process by enabling the designer to evaluate the servo-pneumatic system off-line prior to building the system. This would reduce the design time, increase the reliability of the design, and minimize the design cost. The concept of the CMRE was validated by tests carried out on laboratory-based prototype servo-drive. Close agreement between the experimental and simulated responses was obtained showing that the models have represented the real system adequately. Case studies were then conducted to demonstrate the validity of the proposed methodology and environment. In these case studies, PIDVF controller and cascade control structure were successfully implemented, synthesised, and tuned. The results revealed that the CMRE is an easy, accurate and robust way of implementing different control and tuning strategies on servo-pneumatic systems. Furthermore, the research has shown how the CMRE can lead to significant improvements in certain life cycle phases of the system, e.g. commissioning, maintenance, etc. This research has contributed to knowledge in the following: (1) Adopting the mixed reality concept and the component-based approach in order to create a CMRE in facilitating the control and design of servo-pneumatic systems. (2) A method to identify the friction parameters of a single-axis pneumatic machine, (3) Encapsulate existing control methods within the CMRE to be applied on the real system. (4) A scheme for controller tuning, in which the controller is tuned off-line and then applied on the real system, and hence avoided on-line tuning which can be troublesome and time consuming. It is anticipated that the concept of the CMRE can be extended to include multi-axes servo-pneumatic system, servo-hydraulic, and servo-electric drives. Therefore, conceptual model structures have been introduced in this research which can be considered as the foundation for creating similar environments for those systems

Implementation of Iterative Learning Control on a Pneumatic Actuator.

Masters Degree. University of KwaZulu-Natal, Durban.Pneumatic systems play a pivotal role in many industrial applications, such as in petrochemical industries, steel manufacturing, car manufacturing and food industries. Besides industrial applications, pneumatic systems have also been used in many robotic systems. Nevertheless, a pneumatic system contains different nonlinear and uncertain behaviour due to gas compression, gas leakage, attenuation of the air in pipes and frictional forces in mechanical parts, which increase the system’s dynamic orders. Therefore, modelling a pneumatic system tends to be complicated and challenges the design of the controller for such a system. As a result, employing an effective control mechanism to precisely control a pneumatic system for achieving the required performance is essential. A desirable controller for a pneumatic system should be capable of learning the dynamics of the system and adjusting the control signal accordingly. In this study, a learning control scheme to overcome the highlighted nonlinearity problems is suggested. Many industrial processes are repetitive, and it is reasonable to make use of previously acquired data to improve a controller’s convergence and robustness. An Iterative Learning Control (ILC) algorithm uses information from previous repetitions to learn about the system’s dynamics. The ILC algorithm characteristics are beneficial in real-time control given its short time requirements for responding to input changes. Cylinder-piston actuators are the most common pneumatic systems, which translate the air pressure force into a linear mechanical motion. In industrial automation and robotics, linear pneumatic actuators have a wide range of applications, from load positioning to pneumatic muscles in robots. Therefore, the aim of this research is to study the performance of ILC techniques in position control of the rod in a pneumatic position-cylinder system. Based on theoretical analysis, the design of an ILC is discussed, showing that the controller can satisfactorily overcome nonlinearities and uncertainties in the system without needing any prior knowledge of the system’s model. The controller has been designed in such a way to even work on non-iterative processes. The performance of the ILC-controlled system is compared with a well-tuned PID controller, showing a faster and more accurate response

Commande par mode glissant de paliers magnétiques actifs économes en énergie : une approche sans modèle

Abstract : Over the past three decades, various fields have witnessed a successful application of active magnetic bearing (AMB) systems. Their favorable features include supporting high-speed rotation, low power consumption, and rotor dynamics control. Although their losses are much lower than roller bearings, these losses could limit the operation in some applications such as flywheel energy storage systems and vacuum applications. Many researchers focused their efforts on boosting magnetic bearings energy efficiency via minimizing currents supplied to electromagnetic coils either by a software solution or a hardware solution. According to a previous study, we adopt the hardware solution in this thesis. More specifically, we investigate developing an efficient and yet simple control scheme for regulating a permanent magnet-biased active magnetic bearing system. The control objective here is to suppress the rotor vibrations and reduce the corresponding control currents as possible throughout a wide operating range. Although adopting the hardware approach could achieve an energy-efficient AMB, employing an advanced control scheme could achieve a further reduction in power consumption. Many advanced control techniques have been proposed in the literature to achieve a satisfactory performance. However, the complexity of the majority of control schemes and the potential requirement of powerful platform could discourage their application in practice. The motivation behind this work is to improve the closed-loop performance without the need to do model identification and following the conventional procedure for developing a model-based controller. Here, we propose applying the hybridization concept to exploit the classical PID control and some nonlinear control tools such as first- and second-order sliding mode control, high gain observer, backstepping, and adaptive techniques to develop efficient and practical control schemes. All developed control schemes in this thesis are digitally implemented and validated on the eZdsp F2812 control board. Therefore, the applicability of the proposed model-free techniques for practical application is demonstrated. Furthermore, some of the proposed control schemes successfully achieve a good compromise between the objectives of rotor vibration attenuation and control currents minimization over a wide operating range.Résumé: Au cours des trois dernières décennies, divers domaines ont connu une application réussie des systèmes de paliers magnétiques actifs (PMA). Leurs caractéristiques favorables comprennent une capacité de rotation à grande vitesse, une faible consommation d'énergie, et le contrôle de la dynamique du rotor. Bien que leurs pertes soient beaucoup plus basses que les roulements à rouleaux, ces pertes pourraient limiter l'opération dans certaines applications telles que les systèmes de stockage d'énergie à volant d'inertie et les applications sous vide. De nombreux chercheurs ont concentré leurs efforts sur le renforcement de l'efficacité énergétique des paliers magnétiques par la minimisation des courants fournis aux bobines électromagnétiques soit par une solution logicielle, soit par une solution matérielle. Selon une étude précédente, nous adoptons la solution matérielle dans cette thèse. Plus précisément, nous étudions le développement d'un système de contrôle efficace et simple pour réguler un système de palier magnétique actif à aimant permanent polarisé. L'objectif de contrôle ici est de supprimer les vibrations du rotor et de réduire les courants de commande correspondants autant que possible tout au long d'une large plage de fonctionnement. Bien que l'adoption de l'approche matérielle pourrait atteindre un PMA économe en énergie, un système de contrôle avancé pourrait parvenir à une réduction supplémentaire de la consommation d'énergie. De nombreuses techniques de contrôle avancées ont été proposées dans la littérature pour obtenir une performance satisfaisante. Cependant, la complexité de la majorité des systèmes de contrôle et l'exigence potentielle d’une plate-forme puissante pourrait décourager leur application dans la pratique. La motivation derrière ce travail est d'améliorer les performances en boucle fermée, sans la nécessité de procéder à l'identification du modèle et en suivant la procédure classique pour développer un contrôleur basé sur un modèle. Ici, nous proposons l'application du concept d'hybridation pour exploiter le contrôle PID classique et certains outils de contrôle non linéaires tels que contrôle par mode glissement du premier et du second ordre, observateur à grand gain, backstepping et techniques adaptatives pour développer des systèmes de contrôle efficaces et pratiques. Tous les systèmes de contrôle développés dans cette thèse sont numériquement mis en oeuvre et évaluées sur la carte de contrôle eZdsp F2812. Par conséquent, l'applicabilité des techniques de modèle libre proposé pour l'application pratique est démontrée. En outre, certains des régimes de contrôle proposés ont réalisé avec succès un bon compromis entre les objectifs au rotor d’atténuation des vibrations et la minimisation des courants de commande sur une grande plage de fonctionnement

Visual Servoing in Robotics

Visual servoing is a well-known approach to guide robots using visual information. Image processing, robotics, and control theory are combined in order to control the motion of a robot depending on the visual information extracted from the images captured by one or several cameras. With respect to vision issues, a number of issues are currently being addressed by ongoing research, such as the use of different types of image features (or different types of cameras such as RGBD cameras), image processing at high velocity, and convergence properties. As shown in this book, the use of new control schemes allows the system to behave more robustly, efficiently, or compliantly, with fewer delays. Related issues such as optimal and robust approaches, direct control, path tracking, or sensor fusion are also addressed. Additionally, we can currently find visual servoing systems being applied in a number of different domains. This book considers various aspects of visual servoing systems, such as the design of new strategies for their application to parallel robots, mobile manipulators, teleoperation, and the application of this type of control system in new areas

Advances in PID Control

Since the foundation and up to the current state-of-the-art in control engineering, the problems of PID control steadily attract great attention of numerous researchers and remain inexhaustible source of new ideas for process of control system design and industrial applications. PID control effectiveness is usually caused by the nature of dynamical processes, conditioned that the majority of the industrial dynamical processes are well described by simple dynamic model of the first or second order. The efficacy of PID controllers vastly falls in case of complicated dynamics, nonlinearities, and varying parameters of the plant. This gives a pulse to further researches in the field of PID control. Consequently, the problems of advanced PID control system design methodologies, rules of adaptive PID control, self-tuning procedures, and particularly robustness and transient performance for nonlinear systems, still remain as the areas of the lively interests for many scientists and researchers at the present time. The recent research results presented in this book provide new ideas for improved performance of PID control applications

Advanced Mobile Robotics: Volume 3

Mobile robotics is a challenging field with great potential. It covers disciplines including electrical engineering, mechanical engineering, computer science, cognitive science, and social science. It is essential to the design of automated robots, in combination with artificial intelligence, vision, and sensor technologies. Mobile robots are widely used for surveillance, guidance, transportation and entertainment tasks, as well as medical applications. This Special Issue intends to concentrate on recent developments concerning mobile robots and the research surrounding them to enhance studies on the fundamental problems observed in the robots. Various multidisciplinary approaches and integrative contributions including navigation, learning and adaptation, networked system, biologically inspired robots and cognitive methods are welcome contributions to this Special Issue, both from a research and an application perspective

Controllers, observers, and applications thereof

Controller scaling and parameterization are described. Techniques that can be improved by employing the scaling and parameterization include, but are not limited to, controller design, tuning and optimization. The scaling and parameterization methods described here apply to transfer function based controllers, including PID controllers. The parameterization methods also apply to state feedback and state observer based controllers, as well as linear active disturbance rejection (ADRC) controllers. Parameterization simplifies the use of ADRC. A discrete extended state observer (DESO) and a generalized extended state observer (GESO) are described. They improve the performance of the ESO and therefore ADRC. A tracking control algorithm is also described that improves the performance of the ADRC controller. A general algorithm is described for applying ADRC to multi-input multi-output systems. Several specific applications of the control systems and processes are disclosed