Modeling, identification and minimum length integral sliding mode control of a 3-DOF cartesian parallel robot by considering virtual flexible links

Abstract

This article presents a method for modeling the dynamics and minimum vibration controller design of a 3-DOF parallel mechanism, the so-called Tripteron. The proposed comprehensive dynamic model consists of the dynamic model of the prismatic actuators, variable friction in them, and dynamics of flexibility in the limbs which caused vibration of the robot’s end-effector by considering a spring-damper element for each link based on the Tripteron structure. Then the identification procedure is carried out by collecting practical data from the robot. In order to design the oscillation damping controller, the Minimum Length Integral Sliding Mode Controller(MLISMC) is proposed in which the Phase Trajectory Length(PTL) approach is applied to ISMC for proper placement of closed-loop poles of the identified system. The foregoing method is based on numerical calculations to minimize the end-effector vibrations along the point-to-point control. Simulation and experimental results reveal that the PTL of the system have been reduced about 95% in simulation and 30% in the experimental test.