ISEP – DEE – Comunicações em eventos científicos
Permanent URI for this collection
Browse
Browsing ISEP – DEE – Comunicações em eventos científicos by Subject "Adaptive Control"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- 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.
- A Higher Order Adaptive Approach to Tackle the Swinging ProblemPublication . Tar, József K.; Rudas, Imre J.; Bitó, János F.; Tenreiro Machado, J. A.; Kozłowski, Krzysztof R.In numerous practical applications precise control of a subsystem passively connected to a precisely controllable subsystem by elastic connection is needed. As typical example is a crane carrying its payload swinging on an elastic string can be mentioned. From the point of view of control technology this task is interesting since the connected 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 for simultaneously tackle the problems originating from the imprecisions of the available dynamic model of the system to be controlled and the swinging phenomenon. In the simulation investigations presented a simple model consisting of two connected masspoints is considered: one of them can directly by controlled by control forces, the other one (in the role of the payload) is dragged by the controlled point via an elastic spring. The control considers the 4th time-derivative of the trajectory of the dragged system.