Accuracy Improvement for CDPRs Based on Direct Cable Length Measurement Sensors

In many applications of cable-driven parallel robots (CDPRs), accuracy is an important requirement. The accuracy of CDPRs with a controller based only on the standard kinematic model is limited because of effects like cable elongation. Carrying payload on the platform, i.e. applying an external wrench, increases the influence of this effect. To address this problem, we present a cable length correction method based on direct cable length measurement sensors (DCLM-Sensors). With this method, effects like cable elongation can be compensated. In experiments, the position accuracy of the cable robot IPAnema 3 could be improved by 61.49% without additional payload, and 86.31% with additional payload. We present the integration of the sensor feedback in the cable robot controller and the results of an experimental evaluation on the cable robot IPAnema 3.