Scaling bilateral controls with impedance transmission using transfer admittance

Scaling bilateral control is a method to extend human ability by using master and slave robots. Position scaling extends working space of human; force scaling extends sensitivity of human. This technology is useful when the slave robot is larger in size compared with the master robot. In general, correct environmental impedance, such as softness or hardness of the object, cannot be transmitted in scaling bilateral control due to a mismatch of force scaling and position scaling in the bilateral control. However, correct environmental impedance is necessary for the safe operation, especially in the scaling bilateral control where the mass of robot tends to become large. This paper proposes a method of transmitting environmental impedance in position scaling bilateral control. Position scaling is focused for the sake of extending working space of operator when the slave robot has larger working space compared with the master robot. There exist two methods to scale position in bilateral control; scaling with constant coefficient and scaling with dimension variation. Conventionally, neither of these achieves correct impedance transmission. Proposed method can be applied to both position scaling methods with the same procedure and achieves impedance transmission by using property of gyrator type bilateral control. The transfer admittance has an ability to bring back the scaled bilateral control to non scaled bilateral control during contact motion. The effect of the proposal is verified through simulation and experiment.