Feedback Control Of Prosthetic Hand Stable Force Output With Evoked EMG

The hand is one of the most flexible locomotive organs. For upper limb amputation patients, losing the hand function not only severely affects the normal life of the patients, but also makes a great psychological trauma. In order to help them having a better life, it is necessary and an effective way for amputation patients to wear prosthetic hand. Among prosthetic devices, myoelectric prostheses with its flexible feature, easy to use and intuitive, become one of the most widely used and studied. Grabbing movement is one of the important ability of hand, and producing stable force is a common task in daily life. However, due to lack of feedback for almost commercial prosthetic hand, patients unable to get the hand movement hand environment information in real time. When distraction, fatigue and other factor which could cause the grasp force changing occurred, the object will loose and even fall. And patients unable to hold object stable in real time which restricts the use of prosthetic hand. So, we proposed a new method to produce stable force based on evoked EMG.In order to explore the mechanism of the phenomenon that distraction could degrade the stability of force production, the impact of distraction on activity of flexor during stable grip was measured. Firstly, a distraction simulator was designed based on VC++6.0/MFC platform, and then designed a distraction task while grasping which was used to simulate myoelectric prosthetic user of gripping instability phenomena due to distraction. Here, the EMG intensity and grip force of flexor during stable grip was measured and analyzed from 7 subjects. Results showed that distraction can decline the intensity of sEMG during stable grasp, which is harmful for stable grasping. To assess the feasibility of this control method, a stimulation experiment was designed, and the relationship between the electrical stimulation intensity and the amplitude of M wave was studied from 7 subjects. After established the relationship model, an experiment was assigned and the sEMG, eEMG and their characteristic value were measured in four different initial grip strength before and after stimulation, which was used to test if the electrical stimulation on ulnar nerve can evoke expected EMG from flexor of forearm. The preliminary results showed that the sEMG intensity was declined with distraction, and electrical stimulation on ulnar nerve can evoked expected EMG signals in forearm muscle. The present work revealed that it is possible to provide appropriate control signals for stable force output by changing the stimulus parameters.In order to verify the stability of feedback control method for stability of force production, the virtual human hand stimulation system was implemented with the help of virtual reality toolbox for MATLAB. And proposed an evoked EMG feedback control systems based on virtual human hand to validate and demonstrate the effectiveness. Then the offline EMG was collected to control the force intensity for virtual human hand, results show that, it is able to generate stable force by the feedback control method, and could ensure the output force consistently before and after distraction.The topic studied the feedback control method for electromyography prosthetic hand, proposed and verified a new method to produce stable force based on evoked EMG. This method can achieve grasp stability and have better proprioception, and is contributing to further research for biomimetic control of electromyography prosthetic hand.