Independent metering of pneumatic actuator for passive human power amplification

In this paper, a method for passive human force amplification with independent metering of valves in a pneumatic actuator is reported. Unlike single valve metering, two independent valves are used to regulate the operating pressure of the actuator. The advantage of independent valves is that they can be controlled such that the actuator operates at minimum possible pressure, while providing a desired force profile. This results in reduction of the energy loss associated with discharge of high pressure air to the atmosphere thereby improving efficiency of operation. A pressure minimization scheme on the discharging side of the actuator is proposed to achieve minimum operating pressure. Passive human power amplification is achieved by commanding suitable inputs to the valve on the high pressure side. An experimental comparison with single valve metering shows that independent metering improves the operating time by nearly 100%, thus improving the efficiency of operation.