Using two servovalves to improve pneumatic force control in industrial cylinders

• Published in: International journal of advanced manufacturing technology Vol. 66; no. 1-4; pp. 283 - 301
• Main Authors: Carneiro, J. Falcão, de Almeida, F. Gomes
• Format: Journal Article
• Language: English
• Published: London Springer-Verlag 01.04.2013; Springer Nature B.V
• Subjects: Actuation; Actuators; CAE) and Design; Computer-Aided Engineering (CAD; Control tasks; Cylinders; Cylindrical chambers; Dependence; Engineering; Industrial and Production Engineering; Mechanical Engineering; Media Management; Original Article; Servocontrol; Servovalves; Stiffness; Task complexity; Force control; Nonlinear control; Servopneumatic systems
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-012-4324-8

Pneumatic actuation systems present several advantages like low cost, high force/volume ratios, and the absence of significant heat or magnetic field generation. However, its use in complex control tasks is hindered by their highly nonlinear behavior. This drawback is caused not only by the nonlinear behavior of phenomena like friction but also by the large variation of some of the system proprieties with the system state. One of such proprieties is the fluidic stiffness of the actuator, which may suffer significant changes with the piston velocity when the pressure dynamics of both actuator chambers are coupled due to the use of only one servovalve. This dependency can be eliminated if the pressure (or pneumatic force) inside each chamber is independently controlled using two servovalves. In this paper, two pneumatic force allocation strategies are proposed and analyzed. In the first one, the stiffness of the actuator becomes independent of the pneumatic force reference. In the second one, the pneumatic forces are devised to avoid early pressure saturation of the cylinder chambers. Based on an experimental test rig, both strategies are compared against each other and against the use of only one servovalve.