To address the challenge of balancing control precision and stability in existing trajectory tracking control methods,a robust control method based on Udwadia-Kalaba(U-K)control theory is introduced.Using the Lagrangian method,a dynamic model for robots is established,dividing dynamic parameters into a deterministic nominal part and an uncertain part.The nominal control torque under ideal motion trajectory constraints for the exoskeleton robot system is determined based on the U-K theory and the nominal parameters.A robust controller is introduced to mitigate the effects of uncertainty,with uncertainty boundaries defined to establish the necessary additional control torque.The simulation results indicate that,compared to traditional PID algorithms,the trajectory tracking accuracy of the hip and knee joint angles for the exoskeleton robot is enhanced by 76.4％and 96.8％,respectively,using the proposed U-K-based robust control method.The results from trajectory tracking comparative experiments using a prototype of the lower limb exoskeleton robot designed based on this method show that the trajectory tracking accuracy for the hip and knee joint angles are 0.467 0°and 0.114 1°for the lower limb exoskeleton,indicating an 82.6％and 86.8％enhancement over the PID algorithm used as a control.Furthermore,the overall system control period is decreased by 56.6％.That control method exhibits enhanced synchronization,control precision and stability.
lower limb exoskeleton robotsUdwadia-Kalaba theoryrobust controllertrajectory tracking control
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