Stiffness Modeling Method And Experiment Research Of Flexible Six-axis Force Sensing Mechanism With Heavy-load Capacity

The flexible six-axis force sensing mechanism used for measuring heavy load is the research object in this paper,around the force sensing characteristics of which the theoretical,emulational and experimental research are carried out.The systematic research work includes configuration design,stiffness modeling,force mapping,performance evaluation,simulation optimization,prototype development and calibration.The work provides new idea for the stiffness modeling of flexible parallel force sensing mechanism,and makes theoretical foundations for the design and application of six-axis force sensor in heavy load fields.Firstly,configuration design for the flexible parallel six-axis force sensing mechanism with heavy-load capacity is carried out,based on the design concept of mixed branches.Many reasonable configurations of force sensing mechanism are presented.The overall stiffness and force sensitive area of measuring branches are analyzed by finite element simulation,and the force sensing characteristics of mechanisms are summarized.The work provides theoretical basis for configuration optimization of six-axis force sensing mechanism.Secondly,the stiffness model of the flexible force sensing mechanism with mixed branches is researched.Based on the hypothesis theory of linear elastic and small deformation,each sub-element's calculation formula of double-axis right-circular flexure hinge compliance matrix is derived.Based on the deformation superposition principle in single flexible serial branch and the deformation compatibility condition of parallel mechanism,stiffness matrixes of flexible serial branch and parallel mechanism are built.Further,the analytical mapping model between the internal force of any joint and external force of flexible parallel force sensing mechanism is established.Then,the force mapping model of flexible parallel force sensing mechanism is constructed by the influence coefficient method of parallel mechanism.,The solution of the reacting force on measuring branches is solved by introducing the weighted generalized inverse,and the physical meaning of the calculation results are discussed form the perspective of energy.The whole force equilibrium equation of flexible parallel force sensing mechanism is established using the principle of virtual work.By introducing the second-order influence coefficient matrix,the complete stiffness model of the force sensing mechanism is constructed considering the influence of external force and joint deformation.Further,the complete stiffness model of flexible parallel force sensing mechanism with mixed branches is established using the deformation compatibility condition.Finally,performances of six-axis force sensor with heavy-load capacity based on the optimization configuration are analyzed.The performance index of carrying capacity used for measuring heavy load is proposed,and the influence of key parameters on the carrying capacity is obtained.The change rules between key parameters and the sensitivity of measurement are analyzed by finite element simulation.Aiming at achieving higher measurement sensitivity,the structure of proposed sensor is optimized based on the sensitivity index.The three-dimensional model is calibrated virtually by the virtual prototype technology and its measurement accuracy is discussed.The prototype of six-axis force sensor with mixed branches used for measuring heavy load is developed and manufactured,and the calibration platform is established.The sensor prototype is calibrated and the measurement error is analyzed.