A General Assessment Procedure for the Electrical Energy Consumption of Pneumatic Actuators in Automatic Machines

Pneumatic actuators are widely used components for industrial automation, primarily due to their high power-to-volume ratio, high speed, simplicity of use, and the ease with which they can satisfy applications’ motion requirements. The accurate evaluation of the energy consumption in pneumatic systems is a topic of increasing importance due to contemporary attention to sustainability. Actuators of the same size have different pneumatic energy needs depending on the specific function they must accomplish, in terms of displacement, force, operational speed, and motion time. The dedicated literature focuses either on the best practices for the configuration of the circuit or on the pneumatic energy consumption in specific sections of the system; when electrical energy consumption is treated, only steady-state conditions are considered. Starting from this state of the art, this paper proposes a new general procedure for the assessment of the electrical energy required to perform specific functions in industrial machinery that relies on pneumatic actuators. The procedure is based on the evaluation of the air mass consumption of the actuator considering its actual application requirements, either through experimental measurements performed on the machinery or through a numerical simulation of the system. Regarding the numerical approach, an experimentally validated dynamic multi-domain model of the pneumatic system is proposed to also properly analyse the relevant transient behaviour. Starting from the evaluation of the air mass consumption, the procedure outlines how to calculate the corresponding electrical energy requirements, considering the application requirements and the operating point of the compressor. To this end, the procedure also includes a method to tailor the ISO 1217 standard to the actual working conditions of the compressor. The procedure, which enables the accurate mapping of the requirements placed by the application on the pneumatic actuator to the ultimately required electrical energy inputs, is validated through several simulations of real cyclic application cases. The results in terms of electrical energy consumption are compared to those obtained with the traditional method based on the steady-state behaviour of the system; the comparison shows that the proposed procedure evaluates the energy consumption with greater accuracy in applications characterized by highly dynamic work cycles.