POSITION AND FORCE CONTROL OF MANIPULATORS WITH PNEUMATIC DRIVEN RUBBER ACTUATORS

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Bibliographic Information

Other Title
  • 空気圧駆動型ゴムアクチュエータを用いたマニピュレータの位置と力の制御

Abstract

It is coming to be more important than ever before, in the welfare, medical, agricultural, food production and other application sectors, that skill-based work, such as grasping of human and other soft objects, should be automated and done by robots, if possible. In order for robots to carry out these handling tasks, they must be capable of sensing soft objects and adjusting their position and the applied force to objects. Conventional robots generally lack these control abilities and are not able to hadle soft objects. In this paper, a robot is proposed which can handle such soft objects, so that the robot can control the position and force independently and simultaneously by two-arm configuration with four degrees of freedom at each. The manipulator can move horizontally and employ rubber actuators with air-driven mechanisms. By feeding air into the actuator, the rubber becomes contractive in the direction of length to produce the displacement. The displacement as the actuator output can be controlled by air supply amount at the joint in the PWM manner after sensing the joint angle. This type of actuator has advantages, such as light weight and microprocessor-based control compatibility. In particular, the manipulator proposed here has actuators around the surface and at the tip, so that it can adjust the required force for grasping compliant objects by controlling the surface and tip actuator pressures. Thus the robot can adjust the surface contact ratio and can grasp objects without moving its joint actuators. Since the surface is made of rubber, the robot can handle objects without applying excessive force and damaging objects. By using both joint and surface/tip actuators, the manipulator can perform position and force control independently and simultaneously. Grasping motion control is also possible using the Jacobian matrix of the manipulators. Experiments have been carried out to verify the proposed manipulator's capabilities for handling rigid and soft objects in a wide range of applications. The robot, with a grasping motion, can pinch objects and also hold them. It is shown through experiments that the robotic manipulator can sense object hardness and handle compliant objects.

Journal

  • Biomechanisms

    Biomechanisms 10 (0), 271-280, 1990

    Society of Biomechanisms

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