Research On Assist-as-needed Strategy Of Lower Limb Exoskeleton For Children With Cerebral Palsy

Cerebral palsy is a physical disability that seriously affects the health of children in China.Its lifelong characteristics determine that the focus of treatment is to solve motor disorders and improve the quality of life of individuals.Based on the theory of neuroplasticity,recent studies have shown the effectiveness of lower extremity dynamic exoskeletons in improving gait in patients with chronic cerebral palsy.However,the existing dynamic exoskeleton of children ’s lower limb hip and knee joints is mainly based on single gait training under passive assistance strategy,which lacks consideration of children ’s lower limb motor ability and changes,as well as the degree of active participation in the training process of children,so that children fail to fully participate in sports rehabilitation and reconstruction of neuromotor control mechanism.Therefore,a lower limb exoskeleton assist-as-needed strategy for children with cerebral palsy is proposed in thesis to study the two major problems in the current children’s exoskeleton assist-as-needed strategy : 1)How to achieve a comprehensive evaluation of the whole training process of children ’s lower limb exoskeleton ; 2)How to take the evaluation index and active participation into account in the control strategy.The main work of thesis includes :1.In order to solve the problem of comprehensive evaluation of the whole training process of lower limb exoskeleton in children with cerebral palsy,by analyzing the existing evaluation methods of lower limb motor function ability,the static evaluation indexes based on clinical scale before training and training performance after training,and the dynamic evaluation indexes based on human-machine interaction force during training are proposed respectively.Three assist modes of exoskeleton(passive assist,active assist and safety assist)are divided by fuzzy logic reasoning method.2.In order to solve the problem of integrating evaluation indicators and active participation into exoskeleton control strategy,an assist-as-needed strategy based on force field is proposed.The cubic spline interpolation method is used to select the reference trajectory,and the strategy parameters are adjusted according to the evaluation index proposed above,so that the exoskeleton can adaptively generate joint assist force and walking speed based on the lower limb motor ability and its changes,as well as the active participation in the training process.The simulation results of the robot simulation platform Coppelia Sim show that compared with traditional passive assistance strategies,the assistance effect of assist-as-needed strategy ranges from 31.52 % to 49.54 %.3.The ’ continuous walking ’ rehabilitation mode was developed on the AIDER children ’s exoskeleton system platform,including Bluetooth program development,continuous walking function realization and interactive force module construction.On this basis,a comparative experiment was designed,and the results show that compared with traditional passive assistance strategies,the assist-as-needed strategy achieved assistance effects of 34.47% and 31.54% for the two participants,respectively.The experiment of the assist-as-needed strategy of lower limb exoskeleton for children with cerebral palsy proposed in thesis was carried out on the AIDER children ’s exoskeleton.It was preliminarily verified that the assist-as-needed strategy can reduce the human-machine interaction force during the rehabilitation process,thereby promoting the patient ’s active participation in the rehabilitation exercise.