Hardware-in-the-loop-simulation of pneumatic actuators

Pneumatically actuated control valves find widespread use in process engineering. Usually the valve shaft position is adjusted by a position controller. In order to examine the static and dynamic behaviour of such controllers they are up to now tested in conjunction with an actuator. Since the friction characteristic of the actuator, which varies due to abrasion etc, has a crucial impact on the control loop performance, the tests are not comparative. In the paper, a simulation concept for "hardware-in-the-loop" testing of position controllers is presented. By simulating the friction in a computer and retaining the rest of the hardware, reproducible results are achieved and at the same time red life process conditions are retained. (C) 1998 IFAC.