A Path-Force Synthesis Method For Planar Mechanism With Extensible Solution Space And Its Application In Rehabilitation Mechanism Design

Mechanism synthesis has been a hot topic of research in mechanism science.Usually,the kinematic synthesis of a linkage deals with the problem of designing the linkage to conform to a specified position or motion,without considering the effects of external forces acting on the machine.However,at the same time,ergonomics shows that the design of the mechanism also needs to consider the interaction between the mechanism and the human,and the mechanism should be suitable for the physiological characteristics of the human.On the other hand,most of the traditional mechanism synthesis can only obtain the optimal solution in the mathematical sense,but in practical applications,this optimal solution may not meet the actual engineering requirements due to the constraints of environment,mechanism size,mechanism rotational speed,etc.To this end,this thesis proposes a theory of simultaneous synthesis of trajectories and forces with an expandable solution space.The method of simultaneous synthesis of path and forces integrates kinematics and dynamics,and one of its typical applications is for the design of mechanisms in rehabilitation robots.Rehabilitation robot is a research hotspot in the intersection of robotics and rehabilitation medical care,and the research of rehabilitation mechanism as the characteristic skeleton and actuator of rehabilitation robot is one of the important directions.The use of the simultaneous synthesis of path and forces in the design of the rehabilitation mechanism allows the rehabilitation mechanism to ensure the accuracy of the rehabilitation trajectory while providing assisted forces that meet the body load,which helps patients achieve active rehabilitation training.With this in mind,this thesis aims at the simultaneous matching of path and force in the design process of rehabilitation mechanism,and realizes a path-force synthesis algorithm for coupled serial mechanism with expandable solution space,and designs a computer-aided design system based on this theory to realize the parametric design and modeling of rehabilitation mechanism.The main work and achievements of this thesis are listed as follows:(1)Based on Fourier theory and the principle of virtual work,a unified mathematical model of the path-force synthesis of the coupled serial mechanism is established through kinematic and kinetostatic studies of the coupled serial mechanism.The research results show that the mechanism solution obtained using this algorithm can provide the required auxiliary force while tracking the task trajectory and achieve good interaction between the mechanism and human.(2)Based on the least-square method and singular value decomposition theory,a solution space expansion method for path-force synthesis of coupled serial mechanism is proposed.By adjusting the error coefficients to construct a high-dimension coefficient space in the solution space,the mechanism path-force synthesis can obtain a variety of mechanism solutions with progressively increasing fitting errors,so that the designer can choose from them a solution that takes into account the fitting accuracy and practical constraints.(3)Based on the above theory,a computer-aided rehabilitation mechanism design system integrating data acquisition,customized constraints and visualization modules is designed,and the system can realize the customized design of rehabilitation mechanism.The feasibility of this computer-aided rehabilitation mechanism design system and the validity of the path-force synthesis theory with expandable solution space are also verified by taking the design process of the upper and lower limb rehabilitation mechanisms as an example.