DESIGN OF A HYDRAULIC FORCE CONTROL-SYSTEM USING A GENERALIZED PREDICTIVE CONTROL ALGORITHM

The paper reports the development of a hydraulic force control system utilising a generalised predictive control (GPC) technique. Varying dy namics of the moving actuator due to variable payload or environmental stiffness, as well as changes in the characteristics of hydraulic com ponents, make the dynamics of hydraulic servosystems conceptually time varying. This allows the application of adaptive controls as an attra ctive solution. A suitable model of actuator-environment is establishe d and the recursive U-D factorisation technique is adopted for online estimation of time varying model parameters. Various step and tracking experiments are performed on a laboratory electrohydraulic actuator t est stand to demonstrate good performance and the promise of the devel oped force control system. In spite of poor dynamics and high nonlinea rities (control voltage saturation, fluid flow deadband and dry fricti on in the hydraulic actuator) successful control tests are performed r epetitively.