This thesis deals with the study on the position control of a pneumatic cylinder using low cost on-off valves. The valve changing band (VCB) was proposed to get fast response and to prevent solenoid valves from unnecessary switching at the beginning of response. A learning algorithm based on the steepest descent method was used to compensate the nonlinearity and complexity in mathematical modelling of pneumatic on-off controlled positioning systems. In this algorithm, new factors, desired performance index and modified learning rate, were proposed to improve speed and convergence of learning control. It is shown experimentally that the proposed algorithm is robust to changes of system parameters; the settling time less than 1.0 sec and the error bound of ±0.1 mm can be obtained.
The effects of supply pressure, size of switching valves and multiple valves are discussed through experiments. Computer simulation on the dynamic performances of the pneumatic system is also presented.
