Impact Force Reduction of Manipulators Using a Dynamic Acceleration Polytope and Flexible Collision Detection Sensor

A collision between a physical service manipulator and a human being generally generates massive impact force, which can cause injury and limit the operation speed of the maipulator. This paper develops an effective impact force reduction method that combines an optimal braking method, i.e., dynamic acceleration polytope braking (DAPB), and a flexible collision detection sensor, i.e., air pressure collision detection sensor (APCS). DAPB calculates the maximum braking torque using a dynamic acceleration polytope that represents the acceleration ability of a manipulator, including a redundant one, and decelerates impact velocity quickly whitin the range of torque limits. The APCS consists of a flexible tube and a pressure sensor, and can detect collisions quickly by measuring an air pressure wave. It provides a shock absorber function and sufficient time for the braking. Combining DAPB and APCS can effectively reduce the impact force due to the collision of a manipulator. Several simulations and experiments are performed to confirm the effectiveness of the proposed method, and a 28% impact force reduction was confirmed by a collision experiment, compared with that of conventional braking methods. (C) Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2009