Dynamic Control of Cable Driven Parallel Robots with Unknown Cable Stiffness: a Joint Space Approach

Abstract

In the present paper we discuss a novel dynamic controller for Cable Driven Parallel Robots, based on the Backstepping technique. The main challenge in controlling these robots, is expressing the dynamic equilibrium with respect to the joint variables. This drawback makes the definition of closed-loop controllers more challenging, in comparison with their serial counterparts. The problem is tackled by considering redundant dynamics, expressed in both task and joints space and solved through the method of quasi-velocity. We propose the usage of the observer linearization to estimate the end effector pose and stiffness, by just measuring the motor position, velocity and torque. These variables are used in the feedback loop to control the pose of the end effector. A 3-tendon planar platform is used for the experimental analysis.