LET 'HYBRID' CYLINDERS CONTROL THE ACTION.

The article reports on a portable robotic arm developed by National Aeronautics & Space Administration. The experimental robot arm matches the strength, flexibility, and weight of a human arm. Since conventional electrical and electro hydraulic arms are too heavy, the actuator is powered by compressed air, constrained by hydraulic pressure, and instructed by digital commands. Bill Birchard, president of Andronics and the actuator's inventor, explains that hydraulic fluid totally blocks actuator motion except for controlled flow through a set of pulsed valves. INSETS: AIR OVER HYDRAULIC ACTUATOR WITH DIGITAL RETARD;PNEUMATIC ACTUATOR WITH HYDRAULIC INTENSIFICATION;Not just air;PNEUMATIC ACTUATOR WITH PNEUMO-MECHANICAL BRAKING