Human-machine cooperative robots are required to drive their arms with low impedance and high torque. As a compact mechanism that generates a large torque and has low impedance characteristics, the series elastic drive system, in which an elastic element is inserted between the motor and driving unit, has been proposed. In this paper, we propose a method of applying impedance control to a series elasticity system with a torque-compensating motor that uses a torsion bar as an elastic body that enables its use under high loads. The stability of the system was verified via simulation and experiment by considering the allowable speed and maximum torque of the motor. The experimental results from the conventional system and the proposed system were compared. The proposed system was confirmed to be superior to the conventional system in terms of both stability and tracking performance. Consequently, the effectiveness of our proposed system was confirmed.

As a driving source of a robot arm in order to achieve a smooth movement at high power and with a minimal size, a series elastic drive system added with another actuator is used in this research. A series elastic mechanism using a torsion bar and a high reduction actuator drives the arm, and the added low reduction actuator reduces the vibration characteristics of the arm according to the response delay of the high-reduction actuator and the elastic system. In order to drive the proposed mechanism described above in low impedance, an impedance control method was adapted to the system. From the results of the simulations and experiments, compared to the response of traditional series elastic driving system and the proposed system, we showed the effectiveness of our proposed system.

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