Abstract: This thesis develops an investigation on modelling and control of electrohydraulic actuators. In particular, two original control schemes for the position control of a single actuator and for the coordinated motion control of multi-degree-of-freedom hydraulic system are presented and tested by means of numerical simulations.
The proposed position control scheme is made by some decoupled functions; each function is synthesized on the basis of the dynamic model of the actuator, in order to tackle a specific critical feature of its dynamic behaviour. Both feedback and feedforward actions have been developed. In order to account for the system nonlinearities, the gain of the controller are adaptive with respect to the most significant state variables.
As far as the coordinated motion control scheme is concerned, an original and innovative non-time based control strategy is presented. It is an extension of the Delayed Reference Control (DRC) approach, which has been developed in this thesis for the simultaneous path tracking and active vibration damping of multi-degree-of-freedom linear systems. The proposed approach, named DRSC (Delayed Reference Synchronization Control) allows achieving the coordinated motion by delaying the position reference for the single actuators on basis on an action reference parameter. Such a variable is computed on the fly on basis on an equivalent elastic error, which is in turn a function of the state of the system.
The assessment of the performances of the control schemes has been performed through an accurate numerical simulator, developed in this thesis, capable of reproducing the dynamic behaviour of a hydraulic actuator.
Numerical results from a wide investigation have proved the effectiveness of both the proposed control schemes.