As collaborative robotics become more prevalent, it is desirable to improve the inherent robot safety, on a mechanical level, while maintaining good position tracking. One method is to replace the electric motor+gearing currently used with an alternate actuator which introduces less inertia, friction, and stiffness. A promising approach is the use of hybrid pneumatic-electric actuators (HPEAs). A first generation (GEN1), proof-of-concept, HPEA with low payload capacity and poor mechanical reliability was improved upon to produce the next generation of HPEA. The 2nd generation (GEN2) actuator developed in this work was designed to increase payload capacity and improve mechanical reliability while maintaining low inertia, low friction and low stiffness. The torque capacity was improved by 511% while increasing inertia by only 292%.

The majority of the system was modeled via relevant physical laws. The solenoid valves’ inverse model was provided by a black box artificial neural network (ANN), and the electric motor’s was empirical. The models were used to develop a position controller with an inner loop pressure controller based upon the ANN. An alternate (non-model-based) pressure controller was also developed to compare to the ANN based controllers. The system could operate as a purely pneumatic actuator, or as a HPEA.

Experimentally it was found that the position control based upon the two pressure controllers led to similar performance, but the ANN based were superior more often. The hybrid mode reduced the purely pneumatic mode position error for vertical cycloidal position tracking by approximately 55%. The GEN2 achieved lower position tracking errors as compared to prior works of other HPEAs as well as purely pneumatic actuator control publications. Compared to the GEN1, the GEN2 achieved better position tracking errors in both pneumatic and hybrid operation. The GEN2 will serve as a superior testbed for future HPEA control and collaborative robotics research.