This paper describes how microprocessor-based controls can be used to produce low cost pneumatic servo drives which could find wide application in manufacturing industries. The approach incorporates digital compensation for system non-linearities so that, when positioning loads in a ‘point to point’ mode, it is possible to achieve a significant improvement in both the static and dynamic performance of the drive. For the compensation algorithms implemented a theoretical foundation is presented based on a linearized model of pneumatic drives. The paper also describes how microprocessor-based hardware and software have been constructed to evaluate performance criteria. This test facility has allowed the software implementation of the compensation algorithms to be refined so that satisfactory performance can be achieved with both translational and rotational drives utilizing various forms of transmission. The test facility has also allowed various control system elements to be evaluated so that pneumatic drives suitable for industrial application, can be specified.

This paper describes the features of a pneumatically actuated servomechanism which has been designed for the point-to-point positioning of payloads. The servomechanism utilises low cost computer control and interface electronics to facilitate software compensations for system time delays and non-linearities. The compensation algorithms hve been designed and developed with reference to a linearised model of pneumatic servodrives, which allows for variation in transfer function with load position. Application of these algorithms has allowed a substantial improvement in static performance and dynamic characteristics to be realised for drives incorporating various forms of pneumatic servo valves, pneumatic actuators and load systems. This offers a significant opportunity for commercial exploitation of the pneumatic servodrive. The paper describes the method by which compensation is achieved and references experimental data, which have been obtained by using a standardised evaluation procedure.

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