The pneumatic-electrical dynamic in motion control

22 September, 2016

The benefits of automated motion control are becoming increasingly well-recognised, with both electrical and mechanical developments having made major technological strides over the past few years. Chris Walsh, UK sales manager, Asco Numatics, reflects that in the past, pneumatic equipment was often less compatible with a control system. This often resulted in the mechanical engineers of yesteryear having separate pneumatic systems – sometimes with banks of solenoids – communicating with the electrical system.

“Historically the fluid power components were designed into a machine for its movements on one page and the intelligent control was kept separate,” he explained. “The two technologies were effectively brought together by using an electro-pneumatic interface – for example solenoid valves and PLC in a control cabinet. Today, pneumatics and electrical devices are commonly conceived together as part of a fully generic machine design; control of both is considered as one. Pneumatic actuators are now often controlled by intelligent solenoid valves which are typically part of a fieldbus system; sometimes with proportional control, with feedback diagnostics networking within a multifaceted factory control platform and able to send wireless data through the extranet.”

Achieving the required result

Richard Edwards, technical director, IMI Precision Engineering, considers that the technology behind most engineering solutions has to involve some level of compromise with regard to fluid power and electrical application. “Typically it’s about deciding on the best choice of technologies to achieve the required end result,” he said, adding that there are well-recognised advantages and disadvantages in both electric and pneumatic actuation. “For example, the advantages of electric actuation include the fact that you don’t need a compressed air supply, which, if you don’t already have one will need sourcing and installing. The ongoing operating cost of an electric actuator may prove to be less than a pneumatic alternative, but the acquisition cost is typically more expensive.

An electric actuator will generally provide a greater level of precision and will offer the flexibility to stop it part way along its stroke. The ability to profile the speed and the force applied throughout the stroke of the actuator can be vital for some applications. However, the changes taking place in the world of pneumatic actuation – such as linear transducers and proportional control – are impressive.”

With regard to specific equipment, Giorgio Guzzoni, product manager, Metal Work SpA, believes electric actuators are the right solution for motion control when it is necessary to position accurately at unspecified values, and control speed and/or acceleration ramps. He adds that both technologies – pneumatic actuators and electric actuators – have come together in what are commonly known as electric cylinders. These are electric actuators housed in structures that have the shape of a cylinder.