This paper presents a novel robust fractional PIλ controller design for flexible joint electrically driven robots. Because of using voltage control strategy, the proposed approach is free of problems arising from torque control strategy in the design and implementation. In fact, the motor's current includes the effects of nonlinearities and coupling in the robot manipulator. Therefore, cancellation of motor current by feedback linearization in voltage control strategy can cancel the highly nonlinear dynamics of manipulators. Thus, it can guarantee robustness of control system to both structured and unstructured uncertainties associated with robot dynamics. As a result, the proposed control is simple, fast response and superior to torque control approaches. The control method is verified by stability analysis. Simulations on a two-link actuated flexible-joint robot show the effectiveness of the proposed control approach. Compared with ordinary controller, the fractional type shows a better tracking performance. Manuscript profile

This paper addresses an approximation-based anti-windup (AW) control strategy for suppressingthe windup effect caused by actuator saturation nonlinearity in proportional–integral–derivative(PID) controlled systems. The effect of actuator constraint is firstly regarded as a disturbanceimported to the PID controller. The external disturbance can then be modeled by a linear differentialequation with unknown coefficients. Using Stone-Weierstrass theorem, it is verified that thesedifferential equations are universal approximators. An auxiliary control signal is finally designed tomodify the error signal injected to the PID controller. The proposed AW control scheme is simple,system independent and applicable by digital or analog circuits. Analytical studies as well asexperimental results using MATLAB/SIMULINK external mode, demonstrate high performance ofthe proposed approach. It is shown that the proposed AW scheme renders the performance of thecontrolled system more robust toward the effects of windup than conventional PID AW schemes.The stability analysis is provided by Lyapunov's second method. Manuscript profile

In this paper, a task-space controller for electrically driven robot manipulators is developed using a robust control algorithm. The controller is designed using voltage control strategy. Based on the nominal model of the robotic arm, the desired signals for motor currents are calculated and then the voltage control law is proposed based on the current errors and motor nominal electrical model. Uncertainties such as parametric uncertainties, external disturbances and also imperfect transformation are compensated in the control law. The case study is a two-link robot manipulator equipped by permanent magnet DC motors. Simulation results verify the satisfactory performance of the proposed controller in reducing the tracking error and overcoming uncertainties. Manuscript profile

This short note points out an improvement on the robust stability analysis for electrically drivenrobots given in the paper. In the paper, the author presents a FAT-based direct adaptive controlscheme for electrically driven robots in presence of nonlinearities associated with actuator inputconstraints. However, he offers not suitable stability analysis for the closed-loop system. In otherwords, it does not consider the role of saturation function in both control design and stabilityanalysis. Manuscript profile