The problem of positioning repeatability of linear pneumatic drives with discrete proximity sensors

Although electric drives are very popular and dominate in the industry, there still are areas where the compressed air is used for driving the machines. Pneumatic drives are often used in potentially explosive areas, however – due to many advantages – they have also wider applications in the industry. They also have disadvantages and the most important of them is the high variability of the speed of movement due to the sudden changes of the load. Accurate positioning of pneumatic cylinders rod or carriage requires the use of special electronic control systems, but in practice, solutions based on electronic proximity sensors are often used. In this paper, we will consider the influence of certain aspects – like the operating conditions of the actuator, type of the valve or the design of the control system – on the piston motion as well as on the repeatability of positioning.