Abstract: Compared to the rigid actuator, flexible actuator can absorb some external shock leading to effective protection of mechanisms, and reduce the systems inertia as well as store energy. In order to ensure quality light, vibration absorption, the steel rope is used as a flexible transmission part, a flexible drive unit is developed, whose features are guided by steel rope, increasing force by the movable pulley group, modular, convenient and flexible. A algorithm for tension of steel rope based on viscoelastic dynamic is proposed, which is suitable for mechanical system installed on movable pulley blocks. According to the walking simulation results, the tension sensors and steel rope are chosen. Flexible drive unit and its load device are developed and the control system is built. Full closed loop for position is achieved through the joint encoder feedback. Loading experiments and speed experiment results show that in the no-load case, flexible drive unit can reach the speed of 6 r/min and the frequency response of 2 Hz, while in the case of loading 11.2 N.m flexible drive unit can reach the speed of 5 r/min and the frequency response of 1.3 Hz.

Key words: robot;flexible drive unit;dynamics;steel rope drive;prototype development