Structural Design Of Flexible Knee Exoskeleton And Control System Research

At present,exoskeleton robots have become a popular direction for the development of robots because they have a significant positive role in military,civilian,rehabilitation and other fields.The foreign development in the field of exoskeleton robots is faster than the domestic development speed,which also encourages us to innovate continuously.This topic is about the design and control algorithm of flexible knee exoskeleton.Obtain joint information through laboratory measurement equipment,as a design basis,select the SEA driver to provide flexibility for the system,with high force control accuracy,low output impedance and high impact resistance characteristics;based on the idea of reducing human metabolic energy consumption,the exoskeleton The driving mechanism and the actuator are placed separately,and the driving part is placed on the back of the human body closer to the center of mass of the human body.The Bowden rope is used as the transmission method;combined with the body data of the lower limbs of the human body,the basic size of the exoskeleton is determined,taking into account Under the premise of joint misalignment,body compatibility,safety and comfort,a flexible knee exoskeleton robot that meets the requirements is designed.The lag phenomenon between the output force and the input force in Bowden rope transmission system is analyzed,and the physical model between the two is established.For the parameters that need to be identified in the model,the particle swarm optimization algorithm is used for parameter identification.The double rope scheme is used to calculate the bending angle of Bowden rope by measuring the displacement difference between the inner rope and the sheath,and the solution result is imported into the force physics model for parameter identification.In order to make the output force reach a predetermined value,a feedforward compensation algorithm is designed to compensate the friction force.According to the control design of the human-machine interaction force generated between the human body and the exoskeleton system,the impedance compensation algorithm is used to reduce the impedance of the exoskeleton system,thereby generating a better boosting effect on the human body.According to the two gait changes of human body during walking,corresponding control algorithms are designed respectively.For the fixed-step gait,the control algorithm of impedance compensation and PID control is mainly used.The upper layer adopts the calf sagittal plane speed zero-crossing point to determine the timing of power assistance,ensuring the accuracy of exoskeleton power assistance and improving the accuracy of power control.For the variable-step gait of the human body,the method of impedance compensation and admittance control is adopted.Through displacement compensation,the passive controller converts the displacement compensation into force compensation to the motor end,thereby ensuring that the number of human-machine interactions is reduced.Unnecessary human-computer interaction force generated by displacement change improves the safety of human-computer interaction.The user can flexibly switch between the two control methods according to their own sports conditions to obtain the best assistance effect.