Coordinated control of a new Pneumatic Gripper

Abstract

This paper describes a new pneumatic grasping device, Intelligent Pneumatic Gripper (IPG) that was developed to achieve the primary objective to lift an object to a position without losing contact or slip as fast as possible. Recent developments in pneumatic actuators and valve allow them to be considered for application which previously only electric motors were suitable. Pneumatic system’s inherent low stiffness and direct drive capabilities enable smooth compliant geared electric motor systems. Moreover, pneumatic actuators can cost up to 10 times less than electric motors, while offering a higher power to weight ratio. Each joint of the IPG arms is revolute and actuated by a pneumatic actuators consisting of a low friction pneumatic cylinder and a regulator valve with a position sensor. Each valve supplies regulated pressure to a single chamber of pneumatic cylinder. The pneumatic cylinder extends gradually with the applied force-causing side arm to grasp. The grasping motion of IPG is produced by four pneumatic cylinders. As a result of the IPG physical configuration, the force exerted on the arms depends on the position of stroke of the right and left arms. In IPG, grasping motion is initiated by the pneumatic actuators with two touch sensors for ensured grasping of the object. Lifting motion is engaged after grasping motion. Figures 1 and 2 illustrate the grasping and lifting motion of the IPG gripper system. A nonlinear force feedback controller is designed to control both the position and velocity of the end effector and the constraint force between the gripper and the environment. Simulation studies were performed to illustrate the efficacy of the developed control method.