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Objective:To solve the issue regarding a low correlation between visual and haptic feedback provided by the current upper-limb rehabilitation training system, this study was implemented based on the end-effector based upper-limb rehabilitation robot developed in the lab. A novel visual and haptic feedback fusion technology based on force tracking was investigated and its effect on upper-limb training was also studied. Methods:Based on the force model constructed in a virtual environment, two types of haptic feedbacks correlated to the visual feedback were designed, including the repulsive force when two objects getting close and the friction force when the object moving above medium surfaces. The haptic feedback constructed in the virtual environment was delivered to the trainees by using force tracking based on robot controlling algorithm. Eight health subjects were recruited and trained with and without feedback fusion. In the training process, the actual and expected haptic feedbacks as well as the surface electromyography (EMG) signals from anterior deltoid, posterior deltoid, biceps, and triceps were collected. The root means square error (RMSE) between the actual and expected haptic feedback was calculated under the feedback fusion training mode to characterize the force tracking-based multi-sensory feedback fusion technology. The integrated EMG values (iEMG) and EMG amplitudes per unit time (EMG/T) under two training modes were measured to explore the effect of feedback fusion technology on the upper-limb motor training. Results:Under feedback fusion training mode, the RMSE between actual and expected haptic feedback was (0.757±0.171) N. The values of iEMG from four muscles were significantly higher (|t| > 7.965, P < 0.001), and the values of EMG/T from the biceps, triceps and anterior deltoid were significantly larger under feedback fusion training mode than under the training mode without feedback fusion. Conclusion:The proposed upper-limb rehabilitation robot training system could accurately transmit the haptic feedback constructed under the virtual environment to the trainees. This system could increase the stimulation to trainees' peripheral nervous function through visual and haptic feedback fusion as well as increase the trainees' training effort. The advantages of force tracking-based visual and haptic feedback fusion technology are to freely construct the force model under the virtual environment and the haptic feedback mode is not constrained by the spatial position. Moreover, two or more types of force models can be superimposed in the same spatial position by using this technology that could improve the matching effect between haptic feedback and visual feedback under a virtual environment. The trainees' motor rehabilitation interest could be stimulated and the experience feeling of human-robot interaction could also be enhanced.
RESUMO
Objective:To explore the effect of real-time visual trajectory feedback on the motor learning ability of healthy volunteers during upper limb circle-drawing movements by using rehabilitation robots. Methods:From July to September, 2018, 24 right-handed healthy volunteers were divided into two groups according to the baseline level of motor ability, one group received three kinds of feedbacks including visual, result and real-time trajectory feedbacks (V+KP+KR group), and the other group only received two kinds of feedbacks including visual and performance (V+KR group). Both groups were trained in clockwise circle drawing task under different conditions for five sessions, 20 times per session, and then underwent one session of maintenance test after three days. The motor learning processes of two groups were evaluated and analyzed by two parameters including roundness score and completion time. Results:By using two-factor repeated measures variance analysis, it was found that there were intergroup and intragroup interactions (F = 6.029, P < 0.001). The intergroup individual effects showed that except for the fifth training section (F = 8.775, P = 0.658), the values of roundness score in other sessions were higher in V+KP+KR group than in V+KR group (F > 13.126, P < 0.001). The intragroup individual effects showed that there were significant differences among sessions in both groups (F > 12.465, P < 0.001). For completion time, there was no intergroup and intragroup interactions (F = 1.606, P = 0.228), the intergroup main effect was not significant (F = 0.55, P = 0.477), and the intragroup main effect was significant (F = 3.95, P = 0.031). Conclusion:Real-time trajectory feedback can help volunteers quickly understand the essentials of motor tasks at the early stage of motor learning, thus helping them to improve the fast learning ability of new tasks, but the improvement effect on motor learning during middle and late stages is not obvious. The dependence of volunteers on real-time trajectory feedback gradually decreases in the middle and later stages of motor learning, and they might rely on proprioception to complete tasks.
RESUMO
Objective To study the relationship between on-line correction and stiffness of the upper limb during human movements, so as to improve the measurement accuracy of stiffness and to assess the on-line correction capability. Methods Five kinds of upper limb goal-directed movements in a horizontal plane were designed. The stiffness values at 5 different positions, i.e. in the early period, early to mid period, mid period, mid to late period and late period separately during the movements with sudden perturbation were measured to investigate the regular pattern of human hand stiffness influenced by such on-line correction, as well as the relationship between the movement accuracy and hand stiffness. Results The stiffness was always varying during the movements, and the variation of the stiffness would influence the movement error. On-line correction during the movements could induce an increase in the value of stiffness amplitude, especially at the position in late period of the movement. However, no significant linkage was found between the change of stiffness and the occurrence time or content of on-line correction. Conclusions On-line correction plays an important role in goal-directed movements. Considering that on-line correction may cause a change in the amplitude of the stiffness, the on-line correction function of patients can be more accurately assessed by measuring stiffness value in specific experiments, combined with other medical diagnosis methods in clinic.