Design And Development Of Joint Torque Sensor For Robot Collision Detection

With the development of the robot technology and the increasing demands for robot application,both of industrial robots,medical robots,service robots,and special robots will work in more and more unknown complex environments.In these complex applications,if the robot can not achieve collision detection effectively,the robot manipulator may cause great harm to the surrounding environment and human beings,even to the robot body.In order to do a good robot collision detection,the key point is that the collision must be detected sensitively,accurately and quickly.In the solutions of collision detection,the method based on torque sensor to detect collision has attracted more and more scholars' attention because of its simple principle,reliable results and high sensitivity.Therefore,the purpose of this dissertation is to design and develop a joint torque sensor with simple structure,high sensitivity and good real-time performance.Before the design work,the relevant technical requirements in the collision process and the sizes of integrated joints in the laboratory has been analyzed,to put forward the design index of torque sensor.Using the principle of stress concentration,the structure of sensor elastomer is designed.According to the working process of the sensor,the mechanical model,the parameter model and the mathematical model of the torque sensor are established.Through the topology optimization with multi-objective,the torque sensor obtains higher sensitivity and better stress concentration effect.The structure connect the sensor body to the front cover and bottom cover is further optimized to reduce the thickness of the sensor.Besides the structure design,the output signal of the torque sensor has been conditioned.Using the parallel topology of the wheatstone bridge to improve the stability of the sensor output.Design the PCB circuit board consist of amplifier circuit,AD conversion circuit,power supply circuit.Using the digital output and adjust the positions of 16 input pins of all strain gauges to enhance the ability of torque sensor for resisting the disturbance.Determine the median filtering method for digital filter and use the full bridge circuit to solve the problem of the temperature drift of strain gauge.And the algorithm of programming has been proposed to solve the problems of zero drift of sensor and unbalance of bridge effectively.A calibration platform has been proposed to calibrate the torque sensor.And the calibration results show that the performance of the torque sensor fully meet the design requirements with a very good linearity and sensitivity.Besides,a platform with single manipulator for collision experiment has been established.The sensor is connected in series between the reducer and the manipulator.Then we can find weather the collision happened by the torque deviation between the actual torque measured by sensor and the theoretical torque calculated by dynamics.Finally,the reliability of the torque sensor and the feasibility of the method for collision detection are verified by the collision experiment.