New design relations for 2-DOF PID-like control systems

Self-regulating processes can be controlled by internal model control systems where the usual three-parameter model of the process is transformed into a rational model via a parametrized first-order approximant of the apparent dead time. Using feedback and feedforward compensators leads to 2-DOF PID controllers whose time constants cancel that of the rational model. To obtain the desired sensitivity of the actual control loop, the model adaptation parameter and a gain tuning factor in the control system are determined by functions of the normalized dead time. The response to setpoint changes is selected by means of the feedforward compensator or via a prefilter. Plots of the sensitivity and the simulation of step responses to changes in the controller setpoint or to disturbances, show the validity of these design relations for transfer functions representative of typical industrial processes. (C) 2003 Elsevier Science Ltd. All rights reserved

Internal model control with control-oriented modeling

Internal model control with parametrized first- or second-order models of the process and with some parameter adjustment via simple design relations allows the designer to select the maximum sensitivity desired for the control system, hence its robustness and the damping of the closed-loop responses to disturbances. The response to set-point changes can be selected independently, e.g. it can be almost identical to the normalized response of the process. The robustness and the performance of this control structure are compared to that provided by PID controllers tuned according to classical design relations.Anglai

Globally stable PID-like control of mechanical systems

Decoupled PID control with actuator constraints and velocity measurement or estimation achieves global asymptotic stability of the desired configuration, if there is some friction in the controlled mechanical system and the signals to be integrated are limited accordingly. Stability analysis using the direct Lyapunov method and Gershgorin's "circle theorem" gives these limits and physically meaningful lower bounds on position control gains. A simple procedure is proposed for selecting the design parameters and determining the gains of the controllers. (C) 1999 Elsevier Science B.V. All rights reserved

Robots Positioning Control Revisited

Positioning control systems for robot arms are presented within a general framework in view of unification and classification. Treating coupling torques from other links as an external disturbance reduces the design of the control system to that of SISO servomechanisms driving each of the robot axes individually. A short survey of many control strategies proposed in the literature presents them as different methods aiming at attenuation of this disturbance. The use of disturbance observers is shown to provide a nice and simple way for that purpose. This could be applied to the improvement of actual industrial robots at the cost of slight software modifications

Study of a suboptimal control system

A suboptimal controller based on linear quadratic optimal control theory is proposed for multivariable systems. The control law and the transfer function of the controller are derived. It is shown that the plant can be modelized by various dynamic models (state or recursive equations, pulse response sequences) and that the control law is unaffected by time delays in the plant. The influence of control law factors is investigated and illustrated by examples.Anglai