Morphology and Tension Perception of Cable-Driven Continuum Robots

The operation and control of the cable-driven continuum robot (CDCR) is directly determined by the actuation of cables, and the relationship between the driving length and the tension as well as the morphology of the CDCR has not been deeply researched in previous literature. In this article, a novel methodology for perceiving the morphology, tension, and driving state of the robot is proposed, which can be calculated only by the dynamic driving length/speed of cables without using shape sensors and tension sensors. First, a model of the tension distribution along with the cable path is deduced, which takes into account the influence of the sliding friction. Second, a rigid-flexible coupling dynamic model considering the strain of the cable is established. Then, a nonlinear complementary model between the driving state and the tensions of cables is constructed based on the mechanism of cable actuation, and an efficient solution algorithm is presented. Experiments of a single arm driven by two cables and a three-tandem arm driven by multiple cables were conducted to validate the proposed method. The average errors of the perceiving morphology and tension are 1.85% and 7.26%, respectively, and the transaction between the slack and tensional state of the driving cable is accurately captured. In addition, the hysteresis behavior of the cable actuation is also perceived.