PERFORMANCE OF A MUSCLE-LIKE LEAKY PNEUMATIC ACTUATOR POWERED BY MODULATED AIR PULSES

There is current interest in the development of legged robotic devices inspired by biological walking systems. We have developed an actuator for this type of device that closely emulates the performance of musc le. The actuator is a ''leaky'' single-effect air cylinder controlled through a 3-way valve that either permits charging the cylinder with c ompressed air or opens it to the atmosphere. To emulate muscular activ ation with trains of identical nerve impulses that vary in frequency, we controlled the pressure in the cylinder through pulse frequency mod ulation. To allow a comparison between our cylinder and muscle, we eva luated the open loop performance of the cylinder and valve system in i sometric (no motion) and linear isotonic (constant load) conditions. W e demonstrate that this mode of activation of the cylinder makes its b ehavior quite close to that of muscle. Furthermore, our cylinder/valve system generated twice the tension developed by muscle of the same cr oss-sectional area, with half its power-to-weight ratio. (C) 1996 John Wiley & Sons, Inc.