Marcin Stefan Cwiklinski Impedance Control of a Hydraulic Servomechanism

A position-based impedance controller is proposed and demonstrated on an existing hydraulic press with a two-way vertically mounted hydraulic cylinder driven by a servo-solenoid valve. A proportional-integral-derivative (PID) controller and a Fuzzy Logic Controller (FLC) are primarily developed to meet the accurate positioning requirements of the impedance control formulation. The impedance filter was placed in force-feedback loop to modify a desired trajectory of the hydraulic actuator according to a specified behavior. Simultaneously with the experiment conducted on the real hydraulic press, impedance control was performed in computer simulation with the use of a nonlinear model of the whole hydraulic system (cylinder + servo solenoid valve). Experiments were carried out in free space and with environmental contact. Satisfactory results were achieved in both situations, as well as in noncontact/contact transition.