Abstract: For the humanoid robots, the robot joint flexible actuators can absorb external shocks in order to guarantee the stable biped walking. For this, the flexible driving unit FDU-II has been designed and developed, which has the advantages of lighter weight, joint position limit protection, convenient locking mechanism, higher stiffness and higher output accuracy compared to the flexible driving unit FDU-I. The FDU-II is tested by the max speed test, the driving capability test, the big-range reciprocating motion test, the cut-off frequency test, the walking sample contouring test and the biped walking experiments. For the problem that the cut-off frequency of the mechanical system may not be measured because of the motor rated power limitation during the equal amplitude test, an amplitude-adjusting frequency response test method is proposed for the flexible driving unit test, which decreases the motion amplitude when the motion frequency is increased. This method can effectively solve the cut-off frequency testing problem under the given motor rated power condition. The performance test results show that FDU-II can reach the speed of 77.5º/s and the cut-off frequency of 6.1 Hz under the load torque of 12.6 N∙m, and has a higher bandwidth and driving power than the FDU-I. The stable biped walking experiment shows that the FDU-II has enough driving capability for the pitch motion of the biped robot’s hip.

Key words: biped walking robot, driving capability test, flexible driving unit, frequency response experiment, rope drive