Self-tuning control of a low-friction pneumatic actuator under the influence of gravity

Traditionally the positioning of pneumatic actuators has been limited to movement between preset stops or switches. The restricting factors preventing the use of pneumatic cylinders for accurate servo-control arise from highly nonlinear dynamic properties such as air compressibility and friction effects, which combine to severely degrade time response and positional accuracy. Many real systems are influenced by external gravity forces, which compound the problem of position control. A self-tuning system incorporating an external force balancing term is proposed using a low-friction cylinder. The low-friction cylinder is compared to conventional, sealed cylinders to demonstrate the increased performance.