Active damping of cable-driven parallel robots for 3D printing

The deployment of cable-driven parallel robots (CDPR) in the industry is studied in very various application fields for their low cost and large workspace. However, the lack of rigidity of a CDPR raises issues such as the lack of accuracy and the rise of vibrations. During the last decades, several control strategies have been developed in order to isolate a flexible structure from a disturbance source. The integral force feedback (IFF) has been put forward, as active damping, obtained by driving actuators with signals proportional to the integral of the forces applied to the structure. Additionally, the use of collocated force sensor and actuator ensures unconditional stability. In this contribution, we will present the dynamic behaviours of a simplified CDPR, the performance of IFF controller for CDPR and the effects of an external force on the degrees of freedom. Then the damping and the stability of the system will be determined thanks to open-loop root locus and frequency response plots. Modifications of IFF will be proposed to improve the performance of the system. Finally, we will present an optimization method to set the parameters.