Design and experimental study of flexible wearable rehabilitation gloves

ObjectiveWith the increasing prominence of the aging population, stroke and the hand hemiplegia it causes have become one of the main problems affecting the health of the elderly. Rehabilitation training during the recovery period of stroke is particularly critical, and traditional physical therapy methods have many shortcomings in terms of effectiveness, efficiency, and patient experience. In view of this, this study is committed to exploring and developing a new type of flexible rehabilitation glove, aiming to provide a more effective and comfortable rehabilitation training method for patients with hemiplegia caused by stroke. Methods Firstly, the driving performance of shape memory alloy (SMA) wire was studied, and an electrothermal driving performance test platform was built. The electrothermal performance of SMA wire and the driving characteristics under different conditions were analyzed, and the feasibility of SMA wire as a driving material in flexible rehabilitation gloves was verified. Secondly, based on the human hand skeletal movement mechanism and hand rehabilitation needs analysis, a wearable flexible rehabilitation glove that fits the fingers is designed and reliability analysis is performed. Based on the contraction and driving characteristics of SMA wire similar to biological muscles, an SMA wire actuator is designed and applied to the driving of the flexible rehabilitation glove. Next, the SMA wire drive model was established, including the phase change model, constitutive model and electrothermal drive model. According to the self-sensing characteristics of the SMA wire, the constitutive feedforward control model and the PID control model based on displacement feedback were designed. The control model simulation analysis was carried out, and the following control effect of the strain of the SMA wire actuator under different waveform signals was studied, verifying the rationality of the control model. Finally, a prototype experimental platform and control system software and hardware platform were built, and active and passive rehabilitation training and assisted grasping experiments were carried out. Results and DiscussionsUnder the input of periodic square wave power signal and a certain load, the ratio of the weight that the SMA wire can lift to its own weight is about 200 times. The temperature of the SMA wire rises from room temperature to a phase transition temperature of about 80°C in about 4 seconds. At this point, the SMA wire begins to deform and stress is generated. The changes of the two have similar trends. After about 4 seconds, the SMA wire reaches a maximum contraction force of about 12N and a maximum contraction displacement of about 20mm. On this basis, a cycle life test was carried out, and periodic cycle experiments were carried out on different samples. After 10,000 cycle experiments, the maximum contraction of the SMA wire was still maintained at about 20mm, indicating that the SMA wire has good performance. At the same time, the SMA wire was subjected to constant load variable power and variable load constant power experiments. Under constant load variable power, as the power increases, the maximum displacement of the SMA wire increases from 2mm to a maximum of 20mm, and the maximum contraction force increases from 1N to 15N. After reaching a certain deformation, it will tend to be stable. When the power increases to a certain value, the maximum deformation of the SMA wire also tends to be stable; under constant power variable load, the SMA wire can reach the maximum deformation after a period of time, which is determined by the characteristics of the SMA wire material, but it can be found that the appropriate increase in the initial load can improve the response speed of the SMA wire. Based on the constructed control model, the response simulation of the sine wave control signal and the square wave control signal was carried out. The simulated following error is small, and there is only a large error at the initial point and the signal turning point, and it can quickly follow the expected value, with good control effect; based on the temperature-based control, the PID control following experiment based on displacement (angle) feedback was carried out. The results show that under closed-loop control, it can be controlled according to the expected bending angle value, and it will tend to be stable after reaching the preset bending angle value. Stretching and bending experiments were conducted on prosthetic hands and patients. Under bending control, the thumb of the prosthetic hand can be bent to 30°, the index finger can be bent to 65°, and the middle finger can be bent to 75°; under stretching control, the fingers of the prosthetic hand gradually began to stretch after 4s, and finally approached the initial horizontal state; on this basis, wearing stretching and bending experiments were conducted on three groups of different patients. Under bending control, the bending angles of the thumb, index finger and middle finger of the three groups of patients can reach 45°, 80° and 85° on average. Then, stretching experiments were conducted. The three groups of patients recovered to the initial state after about 4s during the experiment. At the same time, the tension generated by wearing rehabilitation gloves was tested, and it reached stability after 2 seconds. The maximum tension was about 5N, which met the daily rehabilitation exercise. The final angle measured by the mirror experiment was compared with the bending angle of the data glove, and the maximum error angle did not exceed 5°. Finally, a grasping experiment was conducted. The patients were asked to grasp daily necessities while wearing rehabilitation gloves. The patients had good grasping ability for different objects. The fingertip force during grasping was measured to be about 5.5N. When grasping a cup, the flexible rehabilitation gloves provided 4.8N of force for the fingers to grasp. The electromyographic signals of the arms with and without wearing rehabilitation gloves were compared. The electromyographic signals with wearing rehabilitation gloves were more stable. ConclusionsThe results demonstrate the flexible rehabilitation gloves have good rehabilitation movement and assisted gripping effects. Compared with traditional flexible rehabilitation gloves, they have better adaptability and lightness, and can meet the rehabilitation and assistance needs of different patients.