Co-simulation of Impedance and Hybrid Motion-Force Control Strategies on a 4-DOF 5R Parallel Manipulator

Impedance and hybrid motion-force control systems allow robots to perform complex manipulation tasks in which both force and position should be simultaneously regulated. In contrast to solutions based on passive compliant elements, active control allows adaptation to varied working conditions, through variations of the control system parameters. The evaluation of force control strategies is typically performed experimentally, due to the difficulty of accurately modelling at once different phenomena like contact dynamics, mechanical compliances, measurement noise and delays that affect the actual performance of controller, whose synthesis is necessarily based on simplifying assumptions. The use of co-simulation techniques constitutes however an alternative to experimental tests, and allow the safe and effective analysis of the effects of non-idealities not foreseen at the design stage. This work, therefore, investigates the feasibility of contour tracking of unknown planar profiles with a 4-DOF parallel manipulator using Simulink and MSC Adams co-simulations. The results allow a first selection of the most effective control strategies, and suggest that, prior to implementation on the physical prototype of the robot, friction contact compensation should be introduced in order to accurately track velocities and forces also in the presence of significant tangential disturbances.