In this paper, two upper limbs of an exoskeleton robot are operated within a constrained region of the operational space with unidentified intention of the human operator’s motion as well as uncertain dynamics including physical limits. The new human-cooperative strategies are developed to detect the human subject’s movement efforts in order to make the robot behavior flexible and adaptive. The motion intention extracted from the measurement of the subject’s muscular effort in terms of the applied forces/torques can be represented to derive the reference trajectory of his/her limb using a viable impedance model. Then, adaptive online estimation for impedance parameters is employed to deal with the nonlinear and variable stiffness property of the limb model. In order for the robot to follow a specific impedance target, we integrate the motion intention estimation into a barrier Lyapunov function based adaptive impedance control. Experiments have been carried out to verify the effectiveness of the proposed dual-arm coordination control scheme, in terms of desired motion and force tracking
Different from the previous work for quadrotor which mostly discusses application of different controllers to quadrotor control under normal flight conditions, this paper introduces a new design strategy which considers fault tolerant capability of the quadrotor control problems. By utilizing Passive Fault Tolerant Control Systems (PFTCS) concept with backstepping control approach, the trajectory tracking control of the quadrotor UAV has been achieved and simulation results have shown the effectiveness of the proposed backstepping control with higher controller gains when different levels of actuator faults occur in the quadrotor UAV.
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