Pushing operation by flexible manipulator taking environmental information into account

Flexible arm is very useful for space robots because of its light weight and flexibility. Recently, a lot of studies for flexible manipulator have been reported. However, there is little study of pushing operation. Contact motion to unknown environment is difficult because environmental information should be observed on-line. In this paper, pushing operation by a flexible manipulator with position sensitive device (PSD) is proposed. Environmental information can be estimated more accurately by using PSD. Proposed method is composed of three modes; "Approaching", "Touching" and "Pushing" modes. In the approaching mode, resonance ratio control based on PSD is applied. Position control with suppression of vibration is obtained. Compliance control is installed in order to relax the contact force in the touching mode. Finally, two-step controller is proposed in the pushing mode. First, friction effect is identified by friction torque observer. Then pushing control with compensation of the stick-slip friction can be obtained based on the identification. It is possible to remove an object to a desired position exactly by the proposed method. This method can be expanded to a multi mass resonant system. The numerical and experimental results show viability of the proposed method.