Air-Hydraulic Servo Booster Toward Submersible Water-Driven Robots

This letter describes a novel pneumatically controlled hydraulic booster: Air-Hydraulic Servo Booster (AHSB) applied to water-hydraulic robots. This pump-less hydraulic circuit can control middle range water pressure easily by pneumatic proportional valves, where one can use tap water as the hydraulic medium. In this letter, we explain the principle of operation and the control system integration applied to a simple submersible robot arm. Then we analyze the full dynamics of the system and derive control algorithms by which a robust pressure controller is used with sliding mode control. The proposed system is evaluated using a joint torque and position control experiment on the 0.35-m-long robot arm with a 10 kg payload, with connections via 20-m-long hydraulic hoses. The experimental results demonstrate the high potential of the proposed system for remotely operated robots that work compliantly and robustly in various fields without contamination.