Mechanism Modeling And Strain Analysis Inivestigations Of Compliant Parallel Multi-axis Force Sensor

As the important carrier for obtaining spatial force and moment information,multi-axis force sensor plays an important role in key fields such as aerospace,national defense and military,bioengineering and automobile industry,etc.,and it is one of the core components of intelligent equipment and robots to realize the force-sensing interaction with external environment.Hence,multi-axis force sensor has very broad application prospects.Many scholars at home and abroad have carried out in-depth research on multi-axis force sensors,and there are many available products on the market.However,systematic design and analytical methods of multi-axis force sensor are still lacking,which have become the main obstacles to the development of sensors.Therefore,this paper focuses on the configuration design,mechanism modeling,strain analysis and optimal design of compliant parallel multi-axis force sensor by the combination of compliant mechanism,parallel mechanism and multi-axis force sensing technology.To avoid design blindness of multi-axis force sensors and facing actual force measurement demands,the type and characteristic of basic force-sensing units,flexure hinges and compliant force-sensing chains are systematically combed and summarized,and the design flaw of compliant parallel multi-axis force sensors is illustrated based on the configuration evolution of parallel mechanism.Meanwhile,the design example of sensor configuration is also given.The design flaw makes the sensor design and development process more targeted,efficient and convenient.Inspired by the combined design of multiple flexure segments connected serially,a large number of hybrid flexure hinges are designed,and a generalized analytical compliance model that can quickly formulate the equations of compliance and precision is presented.Using the model,the capacity and precision of rotation of flexure hinges are easily evaluated only through the compliances of base segments and simple matrix operations.A two-axis elliptical-arc-filleted flexure hinge that can realize twodimensional rotational motions is designed and its closed-form compliance equations that hold for twenty kinds of different types of flexure hinges are deduced.The presented piecewise modeling idea and combination design method of flexure hinges can provide strong support for the design and analysis of new flexible hinges.Starting from the stiffness analysis of compliant parallel mechanism,the analytical relationship between terminal applied loads of basic flexible units and the external load to be measured is established.By combining with strain-force mapping relationship of force-sensing units,the analytical model between the output strain at the strain-gage bonding point and multi-axis sensing force/moment can be accurately characterized.The model solves the problem of the strain analysis for complex elastic-body structures and provides a quantitative description tool for rapid design and evaluation of sensors.The elastic-body structure of a novel compliant parallel 4-PSU six-axis force sensor is designed,and the analytical expressions for the elements of the sensor strain compliance matrix are derived.Finally,the optimum performance of the sensor and the optimum combination of parameters are obtained by using the nonlinear genetic algorithm to address the task-oriented requirements of force measurement.Combining with multi-axis force-sensing technology and compliant parallel mechanism,the quasi-static models for compliant parallel mechanisms and compliant parallel mechanisms integrated multi-axis force sensing are built to characterize the mathematical relationship between driving forces,external loads and force measurement units,which provide the theoretical support for improving motion precision and operability of micro-operating systems.A new planar two degrees-of-freedom(DOF)micro-motion platform with two-axis force sensing is designed,and the analytical modeling and performance verification for the displacement amplification ratio of the bridge micro-displacement amplifier and the platform are completed,as well as the strain-gage arrangement,bridge connection and strain analysis are also carried out.Finally,the feasibility and effectiveness of the proposed modeling and analytical method are further confirmed from the theory and design practice.