Control and Tension Estimation of a Cable Driven Mechanism Under Different Tensions

This paper proposes a method to estimate and compensate for the changes of cable tension in the control of cable driven mechanisms. Cable tension may depend on various factors, including mechanism design, fabrication and operation. In many systems it is also an adjustable parameter that affects the performance of the control system. An implementation of the unscented Kalman filter is used for the simultaneous estimation of the states and parameters of a cable driven mechanism. Changes in cable tension are captured in the estimated parameters which, along with system states, are used by a model predictive controller to generate appropriate control actions. The method is described and its effectiveness is shown for a single degree of freedom cable driven robot. In addition, the correlation between the cable tension and the estimated robot parameters provides a way of estimating the tension. It is shown that cable tension can be inferred from one of the estimated robot parameters, namely cable stiffness.