Design And Research On Two New Strain Multi-Axis Force Sensors

Multi-axis force sensor can detect force and torque information in multiple directions of 3d space and can be applied in many fields.The multi-axis force sensor can be divided into strain type,piezoelectric type,capacitive type,photoelectric type,piezoresistive type and so on.The strain type multi-axis force sensor can measure both static force and dynamic force,with the advantages of large measuring range,wide application environment,long service life,low price and so on.In this paper,the deep-sea three-dimensional velocity sensor and six-axis wrist force sensor used on high-precision,high-speed robot were designed and researched,and the elastomer of the two sensors were designed especially.In order to meet the requirements of high sensitivity,good dynamic performance and uncoupled output of wrist force sensor for high-speed and high-precision robot,a new elastomer of wrist force sensor with six dimensions was designed in this paper.It was based on the elastomer structure of the typical cross beam type six-axis wrist force sensor with floating beam.And the design ideas are as follows:the floating beam was changed to H-beam,as thus,the stiffness of the sensor is increased and the dynamic performance of the sensor is improved;Drilling holes in the main beam to improve the sensitivity of sensor;The part of the main beam near the center platform was processed as parallel beam to improve the sensor sensitivity;Strain gauges were pasted on the position with the maximum strain on the beam,and the connection mode of the full-bridge circuits were designed to achieve theoretical decoupling.An example was given,which shows that the new sensor is superior to the original six-axis wrist force sensor in both static and dynamic performance.It was proposed that the elastic deformation of the strain type six-axis wrist force sensor has an influence on the positioning error of the robot.The pose error model of the robot was established based on the differential kinematics of the robot,and the real-time compensation method is proposed.Based on the finite element simulation and spatial geometry knowledge,the error model was verified by an example,and the error source of the robot was analyzed.It is found that the error of pose is mainly caused by torsional deformation of sensor.The new six-axis wrist force sensor was optimized.The evaluation criteria of elastomer performance of six-axis wrist force sensor were proposed,including the sensitivity of six-axis directions,the stiffness of elastomer and the first-order natural frequency that as target parameters of optimization.The influence of elastomer's sizes on the sensitivity,stiffness and first-order natural frequency of the sensor in six directions was studied,and the optimized independent variables were determined.Based on the Design expert software,the method of Box-Behnken in response surface method was adopted to establish the orthogonal table,the stepwise regression method was used to establish the quadratic polynomial regression equations,and the elastomer sizes were optimized according to the regression equations.Finally,the feasibility of the sensor is further demonstrated by experiments.Considering the difference in the dimensions of sea current is large and the vertical velocity is very small,and then it's hard to measure it directly,this paper proposed a new three-dimensional flow velocity sensor,which was composed of a horizontal velocity measurement device and a vertical velocity measurement device.It can measure horizontal velocity and small rising velocity separately.According to the characteristics of the horizontal velocity,the horizontal velocity measuring device was designed.The principle of flow resistance around the ball was used to sense the velocity of flow.And the cylindrical fixed rod was used for amplification,and the cross beam is used for force measurement.According to the characteristics of vertical velocity,with the help of the measured results of horizontal velocity,and based on the kutta-joukowsky lifting force theorem,the vertical velocity was sensed by the thin disc.And then,the lifting force of the disc was amplified by the amplifying mechanism.Finally,the magnitude of the enlarged force was measured by a force sensor.Based on fluid finite element simulation and fluid mechanics theory,the principle of velocity measurement by sphere and thin disk was verified.The overall size of the sensor was defined to guarantee that the flow field interference of the sensor device was not affect the accuracy of velocity measurement based on fluid finite element simulation.The structure of 3d velocity sensor was designed,and the measurement principle was verified by material mechanics theory,finite element simulation and experiment.The horizontal velocity measurement structure was optimized,the strength was verified,the frequency characteristic was studied and the dimension coupling was analyzed.This paper introduced the micro-force amplifying mechanism of the vertical velocity measuring device,studied the force transfer and deformation of the amplifying mechanism based on the three-level lever amplifying principle and the material mechanics theory,and optimizes the amplifying mechanism based on the method of finding energy consumption sources.Finally,the design ideas of sensor elastomer were summarized:According to the application environment,adjust the elastomer's performance;Control the distribution of force through elastomer structure;Amplify the force by using some structures ingeniously;The stress is concentrated at the measuring place,that is,the elastic deformation is concentrated at the measuring place;Pay attention to the mass distribution and improve the natural frequency.Finally,some examples were given to verified the five design ideas.