A micro robot actuated by rapid deformation of piezoelectric elements (piezos) is described in this paper. The robot was originally designed to be driven by the similar principle of an inchworm. The adhesion of the electromagnet and the deformation of the piezos made the step displacement of the robot. In this paper, a new control method is proposed. The micro robot is driven by the rapid deformation of the piezos. The adhesion of the electromagnet is not used. Conventional precision positioners, which were actuated by the rapid deformation of the piezos, needed an extra mass. The proposed method does not need any extra mass. The robot realizes the rotational displacement. The principle and the performance of the robot actuated by the rapid deformation of the piezos are described. The piezos are controlled by rectangular waveforms which cause by the rapid deformations of the piezos. Two piezos are deformed simultaneously, i.e. one peizo is extended and the other is contracted by the control waveform. The inertial force causes a step displacement. The rotational displacement in clockwise and counter clockwise direction is obtained. The step rotational displacement obtained is approximately 0.0014".

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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.

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