Design And Research Of 2DOF Sit-to-Stand Assistive Device Based On Newton-Eulerian Method

For the elderly and patients with lower extremity disabilities,sit-to-stand movement is a great challenge.This process requires sufficient muscle strength to provide the lower extremity joints with the moment required to complete the sit-to-stand movement.In the process of sit-to-stand,the center of mass of the human body will move from a stable position to an unstable position,and the movement of the center of mass requires sufficient coordination of the limbs.Difficulty in sit-to-stand also leads to prolonged sitting and bed rest for the elderly and patients with lower extremity disabilities,which can lead to complications such as muscle atrophy and joint stiffness,further reducing their physical fitness.Therefore,independently completing the sit-to-stand movement can not only improve the quality of life of the elderly and patients with lower extremity disabilities,and help them better integrate into society,but also an important means for them to maintain the health of lower extremity muscles and joints and reduce complications.In this thesis,15 male and 15 female healthy subjects were selected as the subjects.Their sit-to-stand movements were studied under different handrail heights,handrail graspping positions,and knee joint support conditions.During the process,the kinematic data and kinetic data of each joint of the human body were measured.The combination of the handrail on front side of the body and the knee joint support was finally selected for the design of the sit-to-stand assistive devices,and a 2 degree-of-freedom model was proposed.The device determined the size of the mechanism through kinematic analysis,and completes the selection of the linear drive through kinetic analysis.Then the overall structure and components of the device were designed respectively,and the stress and strain of the device were verified by the finite element method.Finally,the processing and manufacturing of the prototype and the construction of the control system were carried out,and the humanmachine coupling motion experiment was carried out on the prototype.The cubic spline fitting method was used to fit the human-machine coupling motion compensation law of the three subjects,and the error compensation was performed to achieve secondary control.The experimental results showed that under the condition of knee support,the height of the handrail on front side of the body was an important factor affecting the joint moment of the lower limbs in the sit-to-stand movement.The higher the handrail height,the smaller the peak moment of the knee and hip joints.For the handrails on both sides of body,the grasping position of the handrail mainly affected the peak joint moment of the knee and hip joints.The peak moment of the knee joint was smaller when the grasping position was backward,and the peak moment of the hip joint was smaller when the grasping position was forward.While the height of the handrail mainly affected the difficulty of the sit-to-stand movement as a whole.The higher the handrail height,the less the difficulty of sit-to-stand movement.After comprehensively comparing the peak moment of lower limb joints and difficulty under the conditions of the handrail on front side of the body and both sides of the body,According to the experimental results,it could be seen that the 2 degree-of-freedom sit-to-stand assistive devices could achieve the expected trajectory.