Research On Design And Control Mechanism Of Wearable Soft Hand Exoskeleton System

The hand serves as one of the most important systems in human interaction with the environment,providing tactile feedback and the ability to manipulate objects.Studies have shown that an average of 1,500 grips per person is required per day.Unfortunately,when people suffer from some diseases or injuries,such as stroke,spinal cord injury and so on,which cause paralysis of hands and fingers,they cannot even perform simple daily activities,and the quality of life is getting worse.Currently,the soft hand exoskeleton robots are considered to be the most promising application to daily life of patients and improve their quality of life,which also have many problems,such as single motion mode,poor human-machine coupling,unreasonable design of the back side of the hand,and lack of research on grasping force control and so on.In order to solve some problems existing in the research results of soft hand exoskeleton robots at present,this paper proposes a soft hand exoskeleton robot that can be applied to the patient's daily life to help patients achieve the two main hand movement modes:precision grip mode and power grip mode.In the design of the soft hand exoskeleton robot,mainly based on human anatomy,the flexor digitalis superficialis achieving the movement pattern of precision grip,the flexor digitorum profundus achieving the movement pattern of power grip and the extensor digitorum achieving movement of finger extension are replaced by the tension line,then a set of artificial exoskeleton muscles outside the hand is reconstructed.Since the tension line is consistent with the muscles of hand in the fixed position and the direction of tension on the finger,the soft hand exoskeleton robot has a strong human-machine coupling.Therefore,it can assist the hand of the patients to achieve the same traj ectory as a normal person.For the grasping force control of the wearable soft hand exoskeleton robot,this paper developed a control method based on wire tension feedback,which can realize the stable control of the fingertip force.Firstly,the control strategy of the wearable soft hand exoskeleton robot is introduced.Then a static mechanical model of the finger is established,and the contact force between the fingertip and the object is calculated by the wire tension at the outlet side of the Bowden-cable.For the friction loss problem in the Bowden-cable transmission,the variation range of the sum of the cumulative angles of the Bowden-cable paths is limited to the range of 0°?90° by the physical method.And the friction compensation is performed by the method of median compensation.Finally,the effectiveness of the finger static mechanical model and the friction compensation method is verified by the grasping force control experiment of the soft hand exoskeleton robot,and the maximum range of the fingertip force error is within±1N.In order to test the performance of the soft hand exoskeleton robot,kinematic tests and patient wear experiment were performed on it.The range of motion of each joint can reach the level of normal people with the help of the soft hand exoskeleton robot,and the motion trajectory of the finger during bending and extension is basically the same as the natural movement.The Pearson correlation coefficient between natural motion and device-assisted motion of hand reached 0.97.At the same time,an assisted grasping experiment of the soft hand exoskeleton robot was performed on the patient who lost his hand movement function.The experimental results also confirmed that the soft hand exoskeleton robot has the ability to assist patients in grasping daily necessities,which is of great significance for improving patients' quality of life.