Abstract: A pneumatic rodless cylinder driven flexible manipulator control system is proposed for positioning and vibration suppression of the manipulator,using pulse code modulation(PCM) method.Firstly,the system model of the pneumatic flexible manipulator is derived.Theoretical analysis of the composite positioning and vibration suppression control algorithm is performed.Secondly,because the hysteretic problem of control effect is caused by the following factors,such as long stroke of the cylinder.compressibility of air,nonlinearity of pneumatic driving and time delay of valves' switch,thus, the limit cycle oscillation of high-frequency modes vibration can be easily excited,and the observation and control spillover will be caused.Also,the stability of the control system will be affected.In order to solve this problem,compensation of time delay and low-pass filter methods are introduced into the control algorithm.Finally,experiments on positioning and vibration suppression of the pneumatic flexible manipulator are conducted.The experimental results demonstrate that the composite control method can suppress the low-frequency mode vibration of the flexible manipulator effectively and achieve the purpose of positioning simultaneously.