Percorrer por autor "Rudas, Imre J."
A mostrar 1 - 10 de 27
Resultados por página
Opções de ordenação
- Adaptive nonlinear vibration control based on causal time-invariant green functions and on a novel branch of soft computingPublication . Tar, József K.; Rudas, Imre J.; Bitó, János F.; Tenreiro Machado, J. A.In this paper a simple nonlinear, adaptive approach inspired by the fractional derivatives based CRONE control is presented for vibration damping. Its key idea is replacement of the fractional derivatives with the mathematically less restricted concept of time-invariant Green functions. Instead of the traditional PID feedback terms it applies positive definite weighted moving average of the square of the error plus a nonlinear term making the error converge to zero. In this way simple kinematic design of the desired damping becomes possible. The adaptive part of the controller guarantees the realization of this kinematic design without making it necessary to the designer to have an accurate and complete dynamic model of the system to be controlled or to design sophisticated linear controller. The applicability of the approach is illustrated via simulations for a paradigm consisting of a pair of coupled damper linear oscillators under external excitation. One of the oscillators is not modeled by the controller. The adaptive loop successively maps the observed system behavior to the desired one without exerting any effort to identify the reasons of the differences. The approach was found be useful for solving vibration damping problems with unmodeled and uncontrolled internal degrees of freedom.
- Adaptive nonlinear vibration damping inspired by the concept of fractional derivativesPublication . Tar, József K.; Rudas, Imre J.; Bitó, János F.; Tenreiro Machado, J. A.In this paper a simple nonlinear, adaptive approach inspired by the CRONE method is presented for vibration control. It replaces the fractional derivatives with time-invariant Green functions. Being completed by a nonlinear feedback term it makes the positive definite weighted moving average of the square of the error converge to zero in the kinematic design of the desired damping the realization of which is guaranteed by the controller's adaptive nature. The burden of designing a sophisticated linear controller is evaded. The applicability of the approach is illustrated via simulations for a damped linear oscillator under external excitation at its resonance frequency. The adaptive loop simply successively maps the observed system behavior to the desired one without exerting any effort to identify the reasons of the differences. It is expected to be useful for solving even more complicated vibration damping problems with unmodeled and uncontrolled internal degrees of freedom.
- Adaptive reduction of the order of derivation in the control of a hydraulic differential cylinderPublication . Tar, József K.; Bitó, János F.; Rudas, Imre J.; Tenreiro Machado, J. A.Servo valve controlled hydraulic differential cylinders are non-linear, strongly coupled multivariable electromechanical tools applicable for driving e.g. manipulators. When the piston has finite but considerable velocity with respect to the cylinder the system’s behavior can be “linearized” because the viscous friction i.e. the main source of disturbance is smooth function of this velocity and causes linear damping. When this velocity is in the vicinity of zero the effect of adhesion is the dominating disturbance force that abruptly changes direction depending on the sign of this velocity. Furthermore, at zero relative velocity adhesion can compensate arbitrary forces within certain limits keeping the piston fixed. In the paper a concise application of the Stribeck model of friction and adhesion is reported in an adaptive control in which varying fractional order derivatives are used to reduce the hectic behavior of friction in the case of “critical” trajectories that asymptotically converge to a fixed position and zero velocity. Simulation results made by INRIA’s Scilab are presented. It is concluded that the combined application of the two adaptive techniques reported accurate control can be achieved without knowing the accurate model of the piston-cylinder system.
- Adaptive tackling of the swinging problem for a 2 DOF crane – payload systemPublication . Tar, József K.; Rudas, Imre J.; Bitó, János F.; Machado, J. A. Tenreiro; Kozłowski, Krzysztof R.The control of a crane carrying its payload by an elastic string corresponds to a task in which precise, indirect control of a subsystem dynamically coupled to a directly controllable subsystem is needed. This task is interesting since the coupled degree of freedom has little damping and it is apt to keep swinging accordingly. The traditional approaches apply the input shaping technology to assist the human operator responsible for the manipulation task. In the present paper a novel adaptive approach applying fixed point transformations based iterations having local basin of attraction is proposed to simultaneously tackle the problems originating from the imprecise dynamic model available for the system to be controlled and the swinging problem, too. The most important phenomenological properties of this approach are also discussed. The control considers the 4th time-derivative of the trajectory of the payload. The operation of the proposed control is illustrated via simulation results.
- Adaptive vibration damping based on casual time-invariant green-functions and fractional order derivatesPublication . Tar, József K.; Rudas, Imre J.; Pátkai, Béla; Tenreiro Machado, J. A.In this paper a simple nonlinear, adaptive control using causal time-invariant Green-functions and fractional order derivatives is applied for damping the vibration of a car forced during passing along a bumpy road. Its key idea is the replacement of the integer order derivates in a Green-functions-based nonlinear controller with a time-shift invariant, causal approximation of the Riemann-Liouville fractional derivative that also behaves like a Green-function. Since its physical essence is rather frequency filtering than providing inter order derivatives in limit cases, the approximation applied numerically is quite convinent. In this way simple kinematic design of the desired damping becomes possible. The adaptive part of the controller guarantees the realization of this kinematic design without making it necessary for the designer to have accurate and complete dynamic model of the system to be controlled or to design a sophisticated linear "CRONE" controller that has to take the responsability for the unknown dynamics of the system. The applicability of the approach is illustrated via simulations for a paradigm that is a rough model of a car. It was found that both adaptivity and the use of fractional order derivatives in the control are essential parts of the success of the method.
- Advanced control of robot in tecnological operationPublication . Tar, József K.; Rudas, Imre J.; Tenreiro Machado, J. A.; Horváth, LászlóA novel adaptive robot control tackling the problem of the approximately known robot dynamics and the unknown external dynamic interactions is presented in this paper. By applying uniform structures derived from the Euler-Lagrange equations in the most general and formal level it differs from and overcomes the limitations of classical feedfoward neural network-based approaches as far as the a priori unknown number of the necessary nodes and the scaling ranges of free parameters are concerned. Using a relatively simple structure of reduced number of parameters real time tuning can be carried out in the control. From the point of view of the possible local optimums resulting in improper control the structure here used seems to have the possible least complexity and coupling for a given degree of freedom robot. Several task- independent ancillary procedures also support the control. The method is illustrated via simulation in the case of a 3 active and one passive DOF SCARA arm used for polishing the surface of a bell-shaped work-piece.
- An adaptive robot control for thecnological operations based on uniform structures and reduced number of free parametersPublication . Tar, József K.; Tenreiro Machado, J. A.; Rudas, Imre J.; Bitó, János F.Grinding and polishing are typical application paradigms in which efficient control is needed for approximately and partially known multivariable, nonlinear, strongly coupled mechanical systems (robots) under strong dynamic interaction with an unmodeled environment. A novel adaptive approach to this problem using uniform structures and procedures as well as a passive compliant component as an essential part of the control was recently invented. The method seems to overcome the limitations of the classic approaches as limited speed of motion and supposed separability in the operational space supposing free directions for force/torque components and for free components of translation in their orthogonal sub-spaces. Like Soft Computing, instead developing the formally exact analytical model of the robot, its environment and the dynamic interaction between them the proposed method uses uniform structures but these are derived from the Euler-Lagrange equations considered in a general and formal level of abstraction. In contrast to the general approach fit to a quite wide class of problems, these structures are rather fit to a far narrower task of modeling and control of mechanical devices. This results in a drastic reduction in the number of tunable parameters, fast tuning for those parameters for which no a priori linguistic rules are available and uses simple fuzzy rules for tuning other parameters for which at least qualitative a priori known tuning are known. The proposed technique also is free from "scaling problems" so characteristic to the classic ones. The method is proved and illustrated via simulation in the case of a 3 DOF SCARA arm used for polishing a convex surface as an application paradigm.
- Application of robust fixed point transformations for technological operation of robotsPublication . Tar, József K.; Rudas, Imre J.; Kozłowski, Krzysztof R.; Machado, J. A. TenreiroA robot’s drive has to exert appropriate driving forces that can keep its arm and end effector at the proper position, velocity and acceleration, and simultaneously has to compensate for the effects of the contact forces arising between the tool and the workpiece depending on the needs of the actual technological operation. Balancing the effects of a priori unknown external disturbance forces and the inaccuracies of the available dynamic model of the robot is also important. Technological tasks requiring well prescribed end effector trajectories and contact forces simultaneously are challenging control problems that can be tackled in various manners.
- Centralized and Decentralized Applications of a Novel Adaptive ControlPublication . Tar, József K.; Rudas, Imre J.; Bitó, János F.; Tenreiro Machado, J. A.An adaptive control based on the combination of a novel branch of Soft Computing and fractional order derivatives was applied to control two incompletely modeled, nonlinear, coupled dynamic systems. Each of them contained one internal degree of freedom neither directly modeled/observed nor actuated. As alternatives the decentralized and the centralized control approaches were considered. In each case, as a starting point, a simple, incomplete dynamic model predicting the state-propagation of the modeled axes was applied. In the centralized approach this model contained all the observable and controllable joints. In the decentralized approach two similar initial models were applied for the two coupled subsystems separately. The controllers were restricted to the observation of the generalized coordinates modeled by them. It was expected that both approaches had to be efficient and successful. Simulation examples are resented for the control of two double pendulum-cart systems coupled by a spring and two bumpers modeled by a quasi-singular potential. It was found that both approaches were able to “learn” and to manage this control task with a very similar efficiency. In both cases the application of near integer order derivatives means serious factor of stabilization and elimination of undesirable fluctuations. Since in many technical fields the application of simple decentralized controllers is desirable the present approach seems to be promising and deserves further attention and research.
- Comparative Analysis of a Traditional and a Novel Approach to Model Reference Adaptive ControlPublication . Tar, József K.; Bitó, János F.; Rudas, Imre J.; Eredics, Kristóf; Tenreiro Machado, J. A.In this paper the operation of a recently introduced novel version of the popular "Model Reference Adaptative Controller (MRAC)" is compared with that of a simple version of its possible traditional implementations. The "traditional implementations" normally use Lyapunov's 2nd ("direct") method for adaptative tuning of the controllers' parameters. This method yields global asymptotic stability but its application technically is difficult. In the current control papers pages are occupied with simple iterations that yield Cauchy sequences that converge to the solution of the control problem . Its advantages are its simplicity and precision, its weak side is the local basin of attraction of the convergence applied. However, simulations testify that for practical applications satisfactory "width" can be obtained for the region of convergence. In this paper a 3 Degree Of Freedom (DOF) paradigm, the cart+beam+hamper system is used in numerical simulations to demonstrate the advantages of the novel approach in comparison with a traditional MRAC controller. It is worth nothing that the novel method can be completed with additional tuning for guaranteeing its convergence.
- «
- 1 (current)
- 2
- 3
- »