Research On Design Method Of Compliant Mechanism For Low-Damage And Constant-Force Clamping Of Fruit

The harvest of fresh fruits and vegetables is the key link in facility agriculture that occupies the most labor and is the most difficult to achieve mechanized operation.Therefore,it is urgent to develop efficient,accurate and low-damage picking machinery to replace manual labor.How to effectively avoid or reduce the clamp-induced fruit damage is the research focus of the end-effector.Aiming at the problem of reducing fruit damage under mechanical clamping,this paper proposes a passive compliant grasping method based on compliant elements.Firstly,combining the advantages of Burgers model and Hertz contact theory in expressing the biomechanical properties of fruits,a generalized spring damping model is proposed,which has the ability to simultaneously describe rheological properties and contact conditions.On this basis,the advantages of the passive compliant clamping method are theoretically demonstrated based on mathematical deduction.Aiming at the large deflection nonlinear calculation problem of passive compliant components,this paper studies the construction of link dominance equations based on Bernoulli-Euler beams,the description method of link shape based on rotation angle function,and the construction of numerical equations of link set based on shooting method.As a result,a complete analysis problem of link set numerical analysis under continuous static load is formed.Then,the RKF45-LM-PSO algorithm is proposed to efficiently solve the analysis problem.Based on the above-mentioned solution algorithm of the compliant link set,the SQP configuration optimization algorithm is proposed,and the design of the compliant clamping mechanism is studied according to the three configurations(constant force configuration combined by positive and negative stiffness,parallel buffer mechanism based on force closure theory,single joint compliant gripper based on form closure theory).Force-displacement test,static clamping and dynamic clamping test are designed to verify the effectiveness of the obtained mechanism.Results of the research provide a basis for the design and development of end-effectors based on compliant components,makes up for and perfects the theory of low-damage fruit picking based on passive control,and has practical significance and application value for the popularization of fruit mechanization.