Compressed air saving in symmetrical and asymmetrical pneumatic positioning systems

This article presents simulation and experimental results of an alternative scheme for reducing the consumption of compressed air in pneumatic positioning systems with external loads. The circuit adds a fast-switching on/off valve interconnecting the cylinder chambers on a typical system configuration comprising a symmetrical cylinder and a 5/3 directional proportional valve. The proportional valve is operated using a proportional–integral controller with dead zone compensation, and the auxiliary fast-switching on/off valve is controlled using a pulse-width modulation technique associated with another proportional–integral controller. An algorithm based on the pressure difference and the control signal for decision-making regarding compressed air saving is proposed. The results presented in this article show that the proposed scheme reduced the compressed air consumption by 47%–54%. The simulation results show that the presented approach can also be applied to circuits using asymmetrical cylinders with or without external loads.