Control of an Underactuated 4 Cable-Driven Parallel Robot using Modified Input-Output Feedback Linearization

This paper presents the control of an underactuated four Cable-Driven Parallel Robot (CDPR) using a modified input-output feedback linearization technique. The effect of internal dynamics (due to the underactuated degrees of freedom of the CDPR) on the behavior of the moving platform is presented to highlight the need of an improved controller to stabilize the system outputs. A modified control scheme is then proposed as a solution to obtain stable system outputs. A structure with two separate branches is modeled to simultaneously act on the control inputs and the mathematical calculations are done using the well-established equations of nonlinear control theory. Following this, the response of the system to the modified control law is then verified by simulation. A comparison between the classical and modified feedback linearization is shown to illustrate the significant improvement in the stabilization of the various parameters such as the cable tensions and platform orientations.