The fault-tolerant control issue of aircraft engines with actuator dynamics and faults is investigated in this paper. By proposing a novel intelligent sliding mode fault-tolerant control (ISMFTC) method, which combines an adaptive dynamic programming (ADP) sliding surface with Grey Wolf Optimizer (GWO) for controller parameter optimisation, the goal is to achieve quality steady-state and dynamic performance in aircraft engines while maintaining strong fault-tolerance properties. Firstly, by considering not only actuator dynamics but also actuator faults, an uncertain nonlinear cascaded model of aircraft engines is developed according to characteristic of aircraft engines and their actuators. Secondly, an ADP-based sliding surface is proposed for considered aircraft engine uncertain nonlinear cascaded system. It can obtain a certain sense of optimised performance, and could be solved by ADP strategy off-line as well. Thirdly, fault-tolerant controller is obtained on the basis of sliding mode theory and adaptive fault estimation law, namely, ADP-based ISMFTC controller. Meanwhile, GWO is integrated into the investigation of ADP-based ISMFTC controller, optimised designable control parameters are obtained subsequently. Besides, robustness analysis is elaborated according to Lyapunov theory, fault estimation error is bounded and states of closed-loop system are uniformly ultimately bounded. Simulation on a twin-shaft turbofan aircraft engine, indicates the effect of proposed ADP-based ISMFTC method.

In this paper, a non-linear tracking control algorithm is extended. The control objective of this research is to track a desired time-varying attitude of a satellite in the presence of inertia uncertainties and external disturbances, in order to be more suitable for implementation in a real-world application. In this investigation, the actuators are reaction wheels and the actuator dynamics are modelled in addition to the spacecraft dynamics. Thus, the control signal is DC motor voltage which is the most fundamental control variable and can be generated easily by a motor driver in practical cases. To achieve robust tracking of the desired time-varying attitude, a sliding mode controller is designed, and adaptive techniques are developed based on sliding mode control to overcome the inertia uncertainties and to estimate and compensate external disturbances. The kinematic equations of the satellite are expressed using quaternion parameters, and a novel control law will be derived by using a new facilitating approach in controller design, which is based on quaternion algebra, because of quaternion advantages, such as singularity rejection. Using this approach it will be more comfortable to deal with tedious mathematical operations, and on contrary with most of the previous studies, the terms corresponding to derivatives of the desired attitude are not neglected, and tracking capability is retained. The global stability of both methods (Sliding Mode Control (SMC) and adaptive sliding) is investigated using Lyapunov’s stability theorem. In order to validate the control methods, first, Simulink-ADAMS co-simulation of a 3-DOF attitude control is used to verify the algorithm performance and integrity, and finally, the control strategy is implemented on the Amirkabir University of Technology (AUT) 3-DOF attitude simulator for different types of non-linear attitudes. Both co-simulation and implementation results clearly illustrate the designed attitude control algorithm’s excellent performance in the various manoeuvres.

This paper investigates the vision-based pose stabilization of an electrically driven nonholonomic mobile robot with parametric uncertainties in robot kinematics, robot dynamics, and actuator dynamics. A robust adaptive visual stabilizing controller is proposed with the utilization of adaptive control, backstepping, and dynamic surface control techniques. For the controller design, the idea of backstepping is used and the adaptive control approach is adopted to deal with all uncertainties. We also apply the dynamic surface control method to avoid the repeated differentiations of virtual controllers existing in the backstepping design procedure such that the control development is easier to be implemented. Moreover, to attenuate the effect of disturbances on control performance, smooth robust compensators are exploited. It is proved that all signals in the closed-loop system can be guaranteed to be uniformly ultimately bounded. Finally, simulation results are presented to illustrate the performance of the proposed controller.

This work is concerned with trajectory tracking of robots when the electrical dynamics of the brushless DC motor actuators is considered. It is shown that proportional-derivative (PD) control with feedforward compensation, plus some additional terms to cope with the electrical dynamics, ensures state boundedness. Furthermore, tracking error converges to zero from arbitrarily large initial conditions if controller gains are correctly chosen. Under mild assumptions, this controller reduces to the well-known PD control with feedforward compensation when implemented according to torque control, a successful industrial practice. Thus, it is explained, for the first time, why this strategy works well in applications.

In this paper sliding mode motion design is considered for nonlinear plants which are linear with respect to control input. The dynamics of the robotic manipulators is treated with and without those of the actuators. When the dynamics of the actuators is included a design of the sliding modes for the systems with discontinuous control is performed. If actuators' dynamics is negelected the control is assumed to be continuous quantity. By combining the variable structure systems and Lyapunov designs a new algorithm is developed which has all the good properties of the sliding mode systems while avoiding unnecessary discontinuity of the control thus eliminating chattering. Neither the explicit calculation of the equivalent control, nor high gain inside the boundary layer are used. The parameters of the control depend on the plant's gain matrix, and the gradients of the sliding mode manifold. This control method is then applied to develop a unified control strategy for the motion control systems including the path tracking control, the impedance control and the force control of a robotic manipulator. It is shown that all these tasks can be formulated in the same mathematical form in which selected so-called sliding mode functions must track their references. In this way the systems state is forced to remain on the selected manifold in the state space after reaching it. The solution is interpreted in both the Joint space and the Work space for n -degrees of freedom robotic manipulators.

Nonlinear couplings between the various joints of a robotic arm cause trouble in robot control. One possibility to overcome these difficulties is offered by the concept of nonlinear decoupling. The latter leads to independent linear SISO systems, each of them describing the movement of one joint. Thus, an application of control concepts for linear SISO systems is possible. However, at present such decoupling controls are computed from the mathematical model of the arm, the so-called drive equations, whereas actuator dynamics are considered only in a secondary way. In this paper the decoupling problem for robots is investigated by accounting also for the actuator dynamics from the very beginning. This results in decoupling laws requiring a complete state feedback, i.e. not only joint positions and velocities but also the states of the various actuators have to be used. Further, formulas are given which make the computation of those states unsuitable for direct measurements.

The global trajectory control of walking machines is addressed here with particular attention paid to the consequences of actuator redundancy for control and to the inclusion of actuator dynamics in trajectory controller design. Redundancy of actuation, typical of walking machines, results in the trajectory control problem being formulated perforce in a global coordinate frame, instead of the joint space, as in nonredundant manipulators. This lack of one-to-one correspondence between the degrees of freedom of motion in the global coordinate frame and the actuators results in coupling between the different trajectory control loops. A mechanism for reducing this coupling effect is proposed here, along with a procedure to take into account approximately the effect of actuator dynamics in designing the trajectory controllers. The proposed methods are evaluated by simulation for an example problem in legged locomotion and are shown to be effective.

In this paper, a mathematical representation of constrained robot systems in the form of a differential-algebraic equation model is first considered. This model in modified further to include the joint flexibility between the linkages of the robot, and the actuator dynamics. The objective is to design a feedback control law for the system so that the position output variables (typically the end-effector position) and the force output variables (typically the contact force between the robot's end-effector and the contact surface) of the robot follows the desired position and the desired force trajectories, respectively, despite the presence of joint flexibility and actuator dynamics. A systematic procedure is developed for designing a feedback control law which ensures that the position variables track the desired position trajectories exponentially, and the force variables track the desired force trajectories exponentially. Since the development of the control law is based on the model of a constrained robot system which includes the effects of actuator dynamics and joint flexibility, it is possible to achieve better tracking performance using the force/position control law developed in this paper in cases where such effects are significant.