Kinematic Synergy Of Multi-dofs Movement In Upper Limb And Rehabilitation Motion Simulation

Hemiplegia is currently reported to be the most common post-stroke symptom.The upper limb physical disability caused by cardiovascular and cerebrovascular diseases or other accidents not only brings great physical and mental harm to the patient,but also heavily burden the whole society.Rehabilitation training with the upper limb rehabilitation device is an effective way to restore and reconstruct motor function of the patients.Currently,many of those equipments are performing rehabilitation training in a fixed motion mode,which cannot fully take the naturally movement patterns of the human joints into consideration.Thus,how to make the multiply degree of freedom(DoF)upper limb rehabilitation equipment match the real movement of human joints as much as possible in time and space is an open challenge in rehabilitation.Supported by the intelligent interactive control technology and system based on the multi-source biological information decoding,the National High Technology Research and Development Program of China(2015AA042303),this paper designed a new motion control strategy based on the kinematic synergy of multi-joint movement in upper limbs,aiming at improving the fixed training mode of traditional upper limb rehabilitation equipment ann to adapt to the real movement pattern and trajectory of human joints,which satisfying needs of stroke patient for the upper limb rehabilitation and assitive equipment.Reaching target is a basic movement in our daily life.Firstly,this paper analyzed the abnormal patterns of motion patterns and myoelectric activities in hemiplegia patients during reaching task.We designed an experimental cardboard which contained three different target positions(ipsilateral,central and contralateral),and the kinematic data and electromyography signals of 3 healthy subjects and 2 patients(FMA,42/66 and 36/66)were collected.The results indicated that the patient showed pathological features of movement patterns compared to the healthy,what's more,the severe patient showed a confused muscular synergies and cannot complete the corresponding task.The futher studies about kinematic synergy of multi-DoFs in upper limbs was conducted.An experimental cardboard within 10 target positions was designed and the multi-joints kinematic data of 10 healthy subjects during raching task were collected.Four joint angles were defined as SFE(shoulder flexion/extension),SAA(shoulder abduction/adduction),SIR(shoulder internal/external rotation)and EFE(elbow flexion/extension).The angular velocity matrix for each subject was constructed after the data pre-processing,and then principal component analysis(PCA)was applied in this matrix to extract the spatiotemporal kinematic synergy.Further,the correlation coeeficient analysis and the reconstruction process was conducted.Our results indicated that the first four principal components(PCs)can be used as surrogates to describe synergistic characteristics since 4 PCs was able to explain major proportion of variance.Moreover,we found that the level of variance explained by PCs was significantly reliant of the target position and the joint coordination patterns were dynamically regulated over time as the number of kinematic synergy increases.Furthermore,the low-order synergies appear to show the overall change trend of motion,while the high-order synergies play the role that supplement the details at the special timing.Finally,this work designed a virtual right arm for motion control simulation and visualization of the kinematic synergy of upper limb.Different numbers of PCs were selected to reconstruction process and the angle profiles of each joint were calculated,which simulating the posture of upper limbs based on the first four PCs.Besides,the end-point accuracy was evaluated at the movement completion.The simulation results further demonstrated that the synergy can be implemented for motion control,and the precision of reaching movements improved as the number of synergy augmented.The motion control strategy based on the kinematic synergy of upper limb was presented and preliminarily verified in this work.Thus,the time-varying synergies was potential to facilitate existing fixed pattern in many rehabilitation equipment to match natural upper limb movements and improve the rehabilitation training effect of the stroke patients,which providing novelty ideas for the control strategy of the rehabilitation and assistive robotic systems.