Dual-space adaptive synchronization control of redundantly-actuated cable-driven parallel robots

Abstract

For cable-driven parallel robots, a mobile platform is linked to a fixed frame by multiple flexible cables that are winded by winches, and the main application for such robots is to achieve high-precision motion in a large workspace. However, during the motion process, especially when handling the pick-and-place operations, the parameter uncertainty of the mobile platform in the task space and the uncertain dynamics of the winches in the cable-length space are the two main reasons that may affect the motion accuracy. To make up for these deficiencies, a novel dual-space adaptive synchronization control scheme of redundantly-actuated cable-driven parallel robots is proposed to combine the adaptive synchronization of winches in the cable-length space with the adaptive compensation of the mobile platform in the task space, and the two main reasons are considered separately in their respective spaces. In the proposed control scheme, a new synchronization error is defined to depict the difference of the control accuracy of cables which can be regarded as the coordination motion relation among cables, and a dual-space adaptive method is developed to adaptively compensate for the unknown payload and uncertain model parameters in different spaces. Experiments indicate that the proposed control scheme can greatly improve the control accuracy of each cable and regulate the coordination relation among cables simultaneously, and eventually increase the control accuracy of the mobile platform. Moreover, the experimental results of the pick-and-place operations show that the dual-space parameter adaptation is an effective way to provide the dynamic compensation in the motion control which can ensure high accuracy.