Research On Shunted Parallel Three-Branch Six-Dimensional Force Sensor And Its Performance

According to the requirements of six-dimensional force sensors used on the robot,this paper designs and manufactures a shunted three-legged orthogonal six-dimensional force sensor for detecting heavy load and a shunted three-legged parallel six-dimensional force sensor which is light and easy assembly to solve the existing problem of six-dimensional force sensor in inconvenience assembly and difficulty in online calibration.Both of them have advantages of load shunting,high-reliability,easy assembly and exchangeable without extra calibration.The main research contents of this paper are as follows:Combining the parallel three-branch structure and the flexible hinge,two kinds of rigid-flexible hybrid brackets capable of realizing load shunting are designed,most of the load is carried by the frame and the force-measuring unit on the bracket only bears part of the load,and the force characteristics of bracket are analyzed.The equivalent mechanism method is proposed to establish the static model of two sensors,revealing the force mapping relationship between the force cell and external load.Based on the deformation of flexible hinge,the stiffness model of the two sensor brackets is established,and the load split ratio of the force cell and bracket is determined.The overall stiffness model of shunted three-legged parallel six-dimensional force sensor is established.The static and stiffness model is verified by finite element simulation.Base on the static model,the relationship between the structure parameters and sensor's performance is revealed by numerical examples and verified by finite element simulation.The optimization target and reasonable range of structural parameters are set and the genetic algorithm is used to optimize the performance of the sensor.Prototypes of sensors are built.The range of prototype is determined by analyzing the strength of bracket.The sensor calibration device is designed,and the data acquisition and processing software of the calibration experiment is developed.The linear static calibration and nonlinear static calibration of prototype is completed.Some new performance indexs are supplemented for the sensor.The sensor's static performance is obtained base on the calibration experiment results.The natural frequency,transient dynamic response and harmonic load response of the shunted three-legged parallel six-dimensional force sensor are analyzed to obtain the working frequency band and the safe range of the impact load.The CAD variable geometry method is used in gravity compensation of the sensor on parallel robot wrist in order to accurately measure the six-dimensional force acting on the robot grabbing operation tool.Gravity compensation experiments which determines the gravity and center of gravity of operation tool and loads are completed.