High stiffness pneumatic actuating scheme and improved position control strategy realization of a pneumatic climbing robot

The improved full pneumatic climbing robot Sky Cleaner IV has recently been developed as an intelligent demonstrator and test bed for the implementation of nonlinear locomotion control. Pneumatic actuators control the robot's movement, reducing its weight and increasing its dexterity. The pneumatic system of the robot includes X, Y and Z cylinders, a waist cylinder, brush cylinders and vacuum suckers. The major challenge of the pneumatic system is to achieve precise position control of the two rodless linear X and Y cylinders since the system is nonlinear. Two novel ideas are introduced to the pneumatic actuating system. Firstly, the X and Y cylinders feature an improved pneumatic scheme that drives two groups of four 2-position-2-port high speed on-off valves to adjust the pressure in the two chambers of each cylinder. This improves the pneumatic stiffness of the cylinders remarkably. Secondly, considering the effects of friction and movement acceleration of the cylinder, a compensating variable bang-bang controller is presented to control the cylinders' movement and keep the merits while eliminating the oscillation. The experimental results prove that the two approaches can effectively improve the system's stiffness and control its quality.