The Switchable Cable-Driven Mechanism to Control Multiple Cables Individually Using a Single Motor

Abstract

The cable-driven mechanism is frequently used in many mechanical systems and usually requires one motor for each cable. If the system controls multiple cables, additional components in the motor system can increase the overall mass and volume, making the system less compact. Differential mechanisms had been proposed to pull multiple cables with a small number of motors but are limited because each cable cannot be controlled individually. In this letter, we proposed a switchable cable-driven (SCD) mechanism to control multiple cables individually using a single motor. An experimental testbed for the SCD mechanism was designed to control four output cables through a single input cable by integrating electrostatic clutches to the differential mechanism. The electrostatic clutch is an electrical brake system, and the differential mechanism is a mechanism to pull multiple cables simultaneously using movable pulleys. 3D semicircular electrode design was applied to maximize the friction force of the electrostatic clutch within a limited space, and controllable cables could be switched electrically without any interference between cables. We also verified the feasibility of the SCD mechanism through a simple experiment that demonstrated how the cable tension and stroke required for actual operation differ. When single or multiple brakes were activated in the testbed, the maximum input cable tension slightly increased compared to the no brake condition, but the input cable stroke considerably decreased with each increase in the number of brakes. Although this study had some limitations since it was the first to propose and verify the concept of the SCD mechanism, this novel mechanism can contribute to the miniaturization of the multi-cable-driven systems.