Individual Gait Planning Method For Lower Extremity Exoskeleton In Multiple Environments

Gait planning is to plan the joint data for lower extremity exoskeleton,which is widely used in the movement recovery of walking disabilities.Currently,the gait planning can be achieved by anthropometry or modeling for lower extremity exoskeleton.The individual and environmental differences aren’t considered while they are obviously so great.The gait planning method used in our study considered the individual and environment differences.By using our method different subject can have the most suitable gait in different environments.The article mainly includes three aspects:(1)Mesuring the joint angles of different individuals in different environments,then analyzing them in frequency domains.The unified Fourier series expression of the angle data was constructed by frequency domain analysis.The mean errors(Root Mean Squared Error)between measurd angles and reconstarcted angles in the hip,knee and ankle joints are 0.4°,0.7° and 0.9° respectively.In order to evaluate the performance of gait planning,we constructed a seven-degree-of-freedom link model for the lower limbs and obtained its kinematics equations.(2)Constructing individual gait generation models in different environments to achieve individual gait planning.A strong correlation between influencing factors of gait and angles was verified by correlation analysis.We Constructed the mapping model of the correlation by artificial neural network and used it as individual gait generation model.The results show that the joint angle trajectory generated by the model is in line with the desired trajectory,the mean angle errors of the hip,knee and ankle are 3.6°,4.5° and 3.1°respectively.In the verification based on forward kinematics,the mean error ratio on heel trajectory is 5.6%;In the verification based on lower extremity exoskeleton,the joint angle generated by the gait planning model is used to control the exoskeleton.The mean error of hip and knee angles is 2.50°.While the mean error of the hip and knee angles based on the definite angle trajectory control exoskeleton is 9.96°.So the gait generated by the model is as expected.(3)Constructing a gait generation model for slope and speed differences to achieve gait planning.A slope experiment platform was built to collected the kinematics data of the lower limbs when walking uphill and downhill on different slopes.We studied the relationship between the gradient and the joint angle in the case of different slopes,and the relationship between the speed and the joint angle in the case of different speeds.On this basis,gait planning for different slopes and different speeds is realized.The mean angle error of gait planning for uphill and downhill different slopes,different speeds is 1.4° and1.4° respectively.In the verification of forward kinematics,the error of heel trajectory is small.Therefore,the gait planning method proposed in this paper can be better applied in the selected scenarios.