An Algorithm for Synthesis of Decentralized PID Controller for Large-Scale Mechanical Systems

Abstract

The synthesis of decentralized dynamic controller for large-scale nonlinear mechanical systems with variable parameters is considered in the paper. The large-scale mechanical system is considered as a set of subsystems each associated to one degree of freedom of the system. The model of the subsystem includes the model of the actuator which drives the corresponding joint. For each subsystem local dynamic controller is synthesized. The dynamic controller is synthesized to be robust to variations of parameters of the subsystem and to external perturbations acting upon the decoupled (free) subsystem. The local feedforward is also introduced in each controller to compensate for changes of accelerations along the desired (imposed) trajectory. The practical stability of the local (decoupled) subsystem is considered and then the coupling among the subsystems is estimated. Using the aggregation-decomposition method the practical stability of the complete mechanical system with variable parameters (when interconnections between the subsystems are taken into account) is analyzed. On the basis of this stability analysis we have been able to establish an algorithm for iterative synthesis of the decentralized dynamic controller which can guarantee practical stability of the global system and which is capable to withstand assummed parameter variations. The algorithm is used for computer-aided synthesis of decentralized dynamic control for large-scale mechanical system. The algorithm is described in the paper. The control synthesis is presented for one manipulation robot. For this robot decentralized PID controller is synthesized which is roubst to variation of the payload parameters.