Low pressure pneumatic servomechanisms

Tests on a continuous action low pressure electro-pneumatic linear motion servomechanism are described. Data from individual tests on the components of this system, including the servo valve and the actuator, is used for analogue computer simulations. The simulations are shown to model the experimental system over a wide range of conditions. A simple linear equation is shown to model many aspects of the behaviour of the system. This equation is presented in a form which enables the importance of many system parameters to be easily assessed. An all pneumatic linear-motion servo using discrete fluidic components is described. This system uses pulse-width modulated signals to control on/off valves. Tests on components of the system, including beam deflection proportional amplifiers, Schmitt triggers, valves and a fluidic displacement sensor and also on the complete servo are described. Shortcomings in currently available components are shown to limit the performance of both systems, and modifications necessary to improve their closed loop behaviour are proposed