Overview

The design of quite a number of pneumatic drives is still based on only steady-state specifications, e.g. the required force at end of stroke. Given a system pressure that is often determined by the existing compressor hardware, the required piston area can then be calculated and a cylinder chosen. The valve and accessories like fittings and tubes are often selected to have the same port size as the cylinder.

If the specifications are more detailed and include a required stroke time and a description of the load which has to be moved, a dedicated computer program for the sizing of cylinder drives can be used. All major manufacturers provide this kind of software where the customer can select all components from a catalogue, simulate the system and plot pressures, velocity and position of the load. Within a short while and with some trial and error a suitable circuit can be designed which will work satisfactorily in hardware. With some experience error margins to allow for modelling errors can be established, e.g. to design for a stroke time that is 30 % shorter than required by the specification and to use the one-way flow control valves for a fine tuning on the machine.

A third category of design approaches deals with complex systems with interacting electronic control systems. Lorries, for instance, have always been aggregations of several subsystems like engine, gearbox, brakes and so forth, and thus showed a certain complexity. But in former times those systems worked rather independently...