The potential of using polymer volume changes as a source of actuating power was explored. Volume changes may be induced by allowing the polymer to undergo physical transitions such as glass transition, melting or crystallization, and solid-state phase transformation, or by simply heating or cooling the polymer. When constrained from changing the volume, a polymer can exert a great counteracting stress or pressure on the constraining body. When free to expand or contract, the polymer may be prescribed to undergo a large change in volume or shape. The magnitudes of the counteracting stresses and the percentages of achievable volume changes were calculated for several commonly used polymers. Methods and procedures for making these calculations were established. The actuating power of polymers was compared with that of metals.

The paper describes a technique that compensates a friction in pneumatic cylinder to perform the position control. The friction is one of the most common nonlinearities present in pneumatic actuating systems. For accurate position control and low velocity control, control strategies usually rely on accurate estimation of friction. This paper presents a observer to estimate the friction force in the pneumatic cylinder from the pressures in cylinder chambers. Also, the stiction compensation of a pneumatic cylinder is obtained by adding pulses to the control signal using impulsive control. The characteristics of the pulses in impulsive control are determined from the control action. The simulation results are proved that the method proposed here is effective.