Development of PWM mode position control for a pneumatic servo system

Jiing Yih Lai, Rajendra Singh, Chia Hsiang Menq

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


An experimental and theoretical study of the dynamics and control of a single degree of freedom pneumatic manipulator has been conducted. The proposed pneumatic system is controlled by two conventional on-off valves in which one valve is under the pulse-width-modulation mode and the other is held wide open. A mathematical model incorporating nonlinear pneumatic processes and mechanical system characteristics including friction force has been developed to study the actuator dynamics; then it is used in the simplified form to design the controller. In our control scheme, an inner loop with pressure feedback is formed to control the actuator pressure, and an outer loop with displacement and velocity feedback and a two-stage feedforward force compensation are used to control the load displacement. Also, a learning control algorithm is proposed to improve the position accuracy without any manual adjustment of the control gains. Experimental results on a single degree of pneumatic manipulator indicate that the proposed control scheme works very well as it is able to achieve the desired actuator positioning accuracy without using any mechanical stops which are common in current practical systems. The associated convergence criterion and optimal learning gains have also been provided based on a linear system theory.

Original languageEnglish
Pages (from-to)86-95
Number of pages10
JournalJournal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao
Issue number1
StatePublished - Feb 1992


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