Heat transfer evaluation of industrial pneumatic cylinders

Automatic positioning devices are used worldwide in tasks such as handling or assembly, making them key components of modern manufacturing systems. Pneumatic solutions are usually less expensive than their electrical counterparts, are more reliable, and require less maintenance. However, the complex non-linear nature and high model order of pneumatic systems lead to a very difficult control task. These problems make model order reductions and simplifications a common practice in servopneumatics. The heat transfer between air inside the cylinder and its environment is usually neglected or only indirectly accounted for, since it varies with the pressure, temperature, and speed of the actuator, which makes its experimental assessment difficult. In this work a simple and yet accurate procedure is presented on the basis of a thermal time constant, enabling its evaluation. The procedure is validated by simulation studies, and furthermore the heat conductance of three industrial actuators is experimentally determined.