Micro tracking and positioning using off-the-shelf servopneumatics

• Published in: Robotics and computer-integrated manufacturing 2014-06, Vol.30 (3), p.244-255
• Main Authors: Falcão Carneiro, J., Gomes de Almeida, F.
• Format: Article
• Language: English
• Subjects: Automation; Boundary layer thickness; Coders; Encoders; Law; Manufacturing engineering; Micrometer motion; Micrometers; Nonlinear control systems; Servopneumatic systems; Tracking
• ISSN: 0736-5845; 1879-2537
• DOI: 10.1016/j.rcim.2013.10.003

Conventional pneumatic systems do not exhibit significant heat or magnetic fields and present high force to volume ratios. They are, however, typically confined to simple motion tasks owing to their control complexity. Leveraging on a sliding mode based control strategy, the authors have shown in previous works that good tracking and positioning results can be achieved using off-the-shelf servopneumatics. This paper extends the previously mentioned works by applying a modified version of the control law to a new experimental setup comprising different valves and actuators and a better resolution encoder. The modification of the control law involves the use of a new boundary layer thickness variation law, different from the one previously used. Experimental results show that the modified control law leads to very accurate motion control. The positioning error from a control perspective is only limited by the encoder resolution, 1μm, in any position of the piston stroke and when carrying loads of 3kg and 8kg, without any controller retuning. Good results in the micrometer range are also obtained when tracking sinusoidal and triangular references. •This work presents a nonlinear control law applied to a new experimental setup comprising a 1µm position resolution encoder.•Experimental results show that accurate motion control is achieved, with a positioning error only limited by the encoder resolution.•These results are obtained without any controller retuning, throughout the piston stroke, when carrying loads of 3 and 8kg.•Experimental results also show that good results in the micrometer range are obtained when tracking sinusoidal and ramp references.•This work shows that accurate motion control in micrometer range is feasible with conventional servopneumatics.