Estimation mechanism of contact information for a soft robot

For a soft robot with compliant joints, the contact information including the reaction force and the equilibrium posture while touching an object is important information. In this paper, McKibben pneumatic actuators acting as artificial muscles are adopted to drive the robot joint. We propose a sensing mechanism that estimates the contact information instead of attaching sensors on the contact point and joint. We focus on the passivity of the pneumatic actuator, which is deformed according to the external force. The pressure is passively changed following Boyle-Charles' law. This paper deals with one degree of freedom test bed model driven by two antagonistic pneumatic actuators. Using the pressures before and after the force is applied, the model derives the contact information. The experimental results show that the force and the angle can be estimated. We also measure the range of force that the system can sustain. These results indicate that the sensorless estimation of contact information can be realized by employing the passivity of the pneumatic actuator.