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This paper addresses the leader–follower consensus control problem for a nonlinear multi-agent robot system with control input constraint and external disturbances. Robot system is one of the most important practical systems in the industry. Due to the presence of disturbances in most practical systems, this paper considers the issue of finite-time leader–follower consensus control of the nonlinear multi-agent robot system along with actuator saturation and bounded disturbance. The modified terminal sliding mode control method is suggested for the system which is able to guarantee the stability of the overall system and fast finite-time leader–follower consensus control. For two different scenarios, the simulation of multi-agent robot system has been performed. The results show the effectiveness of the proposed control method.

Dealing with torsional vibrations and stick–slip oscillations of a drill string system is a challenging engineering task in the oil drilling process because of the harmful and costly consequences of such vibrations. In this article, the drill string system is modeled using a lumped-parameter model with four degrees of freedom, and the bit–rock contact is represented by a nonlinear function of a bit velocity. Also, tracking the desired velocity of a drill string system with known constant input delay is addressed in the presence of external disturbance and parameter uncertainties by applying the Smith predictor–based sliding mode control method. The performance of the smith predictor–based sliding mode control with input delay and disturbance in tracking the desired velocity and controlling the stick–slip oscillations is compared with the sliding mode control with/without input delay. The system output’s sensitivity to the delay parameter is also investigated, indicating how the bit velocity changes concerning the delay parameter. The proper choice of adaptation gain is determinative in the performance of the controller, and its impact is investigated. Moreover, the robustness of the smith predictor–based sliding mode control is shown by changing the weight on the bit parameter. Simulation results demonstrate the effectiveness of the proposed method.

Loss of Excitation (LOE) is an important fault in synchronous generators which may cause the generator outage due to out-of-step(OS) conditions. Since the LOE protective relays act based on the impedance or admittance measurement at the generator terminals, they suffer from mal-operations caused by non-LOE phenomenon such as stable power swings. To preserve the security and dependability of the LOE protection, in this paper, some unique characteristics of LOE event are determined using the transient model of synchronous generators. In this paper, using the transient model of synchronous generators, some unique characteristics of LOE event are determined. Frequency decomposition and time domain analysis of active and reactive powers as well as the terminal voltages are used to define a suitable rule for LOE protection. A comprehensive list of full and partial LOE scenarios, power swing and other non-LOE scenarios at different loading conditions and topological configurations are considered. The input-output data of the simulated scenarios are then utilized by a support vector machine(SVM) to construct a relay logic for partial and total LOE protection. The efficiency of the proposed LOE protection algorithm is verified using a dynamic test system. The results are analyzed using performance criteria such as dependability, security and accuracy.

This paper provides necessary and sufficient conditions for the existence of the static output-feedback (OPFB) solution to the $H_{\infty } $ control problem for linear discrete-time systems. It is shown that the solution of the static OPFB $H_{\infty } $ control is a Nash equilibrium point. Furthermore, a Q-learning algorithm is developed to find the $H_{\infty } $ OPFB solution online using data measured along the system trajectories and without knowing the system matrices. This is achieved by solving a game algebraic Riccati equation online and using the measured data. A simulation example shows the effectiveness of the proposed method.

This paper presents a new actuator selection methodology for over-actuated systems based on the actuator effectiveness index. In the proposed method, possible actuator candidates are quantitatively compared. The index is calculated for all candidates and is then used to select the appropriate actuator set based on their effectiveness. The desirable properties for the input selection method are discussed and several examples are presented to show that the results based on the proposed index are compatible with the field knowledge. Furthermore, the proposed actuator selection method is employed to set the actuators groups in the daisy chain type control allocation approaches.This leads to a better initial selection of the actuators and reduces the computational burden of the daisy chain type methods by considering the most effective actuators in the first group.