| The rehabilitation mechanism is a device that assists the human body to complete the relative movement of limbs or joints and then achieve the rehabilitation and assistance of joints and muscles.It is the product of the integration of medicine and machinery.Ankle joint injury is common due to aging population,accidents and improper exercise.The untimely or incomplete treatment will affect joint function.This paper presents a dual parallel ankle rehabilitation mechanism,which enables the ankle joint to achieve various movement modes in a small range,as well as a wide range of gait movements with the lower limb.The kinematics analysis and rehabilitation effect evaluation are also carried out.First of all,the physiological structure and motion characteristics of human ankle joint are analyzed,and the normal motion ranges of human ankle joint are given.Based on human motion characteristics,a [R&(2-SPU+PRR)]+(4-RPR)dual parallel ankle rehabilitation mechanism with 2-SPU+PRR and 4-RPR as the main body is designed.It includes an adjustable lifting and fixing device to satisfy the rehabilitation needs of people with different body types.A position limiting device that limits the range of motion is installed to meet the rehabilitation exercise within the required safety range of motion to ensure the safety of the rehabilitation mechanism.According to the law of ankle rehabilitation movements,the rehabilitation process is classified into the early and middle stages and the late stage.In the early and middle stages,the patients mainly focus on the small range of rehabilitation exercises of dorsiflexion /plantar flexion,inversion / eversion and adduction / abduction of the ankle joint,and in the late stage of rehabilitation,a large range of rehabilitation movements with lower limbs can be increased,which is mainly based on gait cycle.Secondly,the R&(2-SPU+PRR)parallel mechanism has the motion characteristics of three rotations and one translation,and the 4-RPR parallel mechanism in series with the outside has the motion characteristics of one rotation and two translations.Using closed-loop vector method,spatial geometry and position change method,the inverse kinematics of the mechanism is obtained.The workspace of R&(2-SPU+PRR)is obtained using limit search method.The results show that the workspace is continuous within the parameter range and the kinematic performance of the mechanism is good.According to the inverse position solution of 2-SPU+PRR parallel mechanism,the first-order motion influence coefficient matrix and the second-order influence coefficient matrix are obtained,and the input and output mathematical relations of the velocity and acceleration of the mechanism are obtained,and the Jacobian matrix J of the mechanism is further obtained,and the transmission ratio of the mechanism from the joint drive to the motion velocity of the moving platform and the transmission relationship between the two forces are obtained.Then,the [R&(2-SPU+PRR)]+(4-RPR)dual parallel ankle rehabilitation mechanism is imported into the Adams software for kinematic analysis,and different Step functions are set for each branch chain according to their respective motion rules,and the curves of physical quantities,such as dorsiflexion /plantar flexion,inversion / eversion and adduction / abduction,traction movement in vertical direction,and the displacement,velocity and other physical quantities with time of the pivot point of rehabilitation movement in a gait cycle are obtained,respectively.The results show that the mechanism conforms to the preset motion rules and range,and can meet the needs of ankle rehabilitation.Finally,a biomechanical model of [R&(2-SPU+PRR)]+(4-RPR)dual parallel ankle rehabilitation mechanism is established in Any Body software environment to analyze the rehabilitation effect.For the ankle joint dorsiflexion /plantar flexion,inversion / eversion,adduction/abduction and rehabilitation movement in a gait cycle,the variation laws of the parameters reflecting the rehabilitation effect with time,such as the maximum muscle activity,muscle length and muscle contraction,are obtained.The results show that [R&(2-SPU+PRR)]+(4-RPR)dual parallel ankle rehabilitation mechanism can better play the role of ankle joint rehabilitation,and the main muscle groups of the ankle joint are effectively exercised,without causing muscle fatigue damage;Various forms of ankle rehabilitation exercise of ankle joint can also be carried out within the preset safety range,which ensures the safety during the rehabilitation process,without causing secondary injury. |
PDF Full Text Request