International Journal of Control, Automation and Systems

The attitude control system design for an unmanned helicopter is always a challenging task because the vehicle dynamics are highly nonlinear and fully coupled and subject to parametric uncertainties. This paper presents an adaptive attitude tracking controller with dual model structure, which achieves significant tracking performance and has good capability to overcome the adverse effect of measurement noises on the convergence of adjustable parameters. Moreover, a modified controller with variable gain elements is designed to further reduce the adverse effect of measurement noises on the adjustable system output in the later stage of the adaptive learning process. A series of hardware-in-loop simulations have verified the proposed adaptive control schemes. The suggested design methodologies featured in this paper are effective control tools that can help bridge the gaps between adaptive control theory and the need of realistic applications such as high-performance unmanned helicopters.

For a planar underactuated manipulator (PUM), if one of its joints is passive except for the first joint, it has the second-order nonholonomic constraint. This paper develops a novel control approach for such PUMs. Combining with the geometry relationship of the PUM and using differential evolution algorithm (DEA), the desired angles of all joints are solved, which transforms the position-posture control into the angle control. The coupling relationship between the passive joint and all active joints is developed, which indicates that the passive joint angle can be adjusted jointly to its desired value when all active joints rotate to their desired angles along specific trajectories. Then, the trajectories for all active joints are constructed, and their design parameters are solved by using the DEA. The continuous state feedback controllers are designed for all active joints to make them track their trajectories. Taking four-link PUMs with one passive joint located at different positions as examples, we perform four simulations and the results verify the universality and superiority of the above approach.

Fuzzy control is a practical alternative for a variety of challenging control applications since it provides a convenient method for constructing nonlinear controllers via the use of heuristic information. This approach provides a formal methodology for representing, manipulating, and implementing a human’s heuristic knowledge about how to modeled and to control a system. This paper focuses on the application of fuzzy control approach to the surge phenomena in centrifugal compression system. Fuzzy controller is designed to consist of an active surge control and phase control without any explicit system models, but driven in the human thinking mechanism. This fuzzy control methodology suggested in this work reproduced well the main characteristics of the turbo compressor dynamic model developed by Moore and Gretzer and give place to a more precise and easy to handle representation. Application and simulation results are performed to demonstrate the effectiveness of this controller. Studies show that, the proposed controller provides good tracking control performance for the compression system at different operating conditions and moreover improves the dynamic performances of the system.

Detection-based pedestrian counting methods produce results of considerable accuracy in non-crowded scenes. However, the detection-based approach is dependent on the camera viewpoint. On the other hand, map-based pedestrian counting methods are performed by measuring features that do not require separate detection of each pedestrian in the scene. Thus, these methods are more effective especially in high crowd density. In this paper, we propose a hybrid map-based model that is a new directional pedestrian counting model. Our proposed model is composed of direction estimation module with classified foreground motion vectors, and pedestrian counting module with principal component analysis. Our contributions in this paper have two aspects. First, we present a directional moving pedestrian counting system that does not depend on object detection or tracking. Second, the number and major directions of pedestrian movements can be detected, by classifying foreground motion vectors. This representation is more powerful than simple features in terms of handling noise, and can count the moving pedestrians in images more accurately.

This research work focuses on the design of a robust-adaptive control algorithm for a 4DOF Unmanned Underwater Vehicle (UUV). The proposed strategy is based in a Non-Singular Terminal Sliding Mode Control (NTSMC) with adaptive gains, where the proposed adaptation mechanism ensures that the gains remain bounded. In this control strategy a non-singular terminal sliding surface is proposed to obtain a faster convergence of the tracking errors. The NTSMC ensures Practical Finite-Time Stability for the closed-loop system as well as exhibits a chattering reduction. In order to demonstrate the satisfactory performance of the proposed controller, a set of experiments was performed with a Non-Singular Terminal Sliding Mode Controller and an Adaptive Non-Singular Terminal Sliding Mode Control (ANTSMC) in real time for trajectory tracking in the X-Y plane, the graphs showed that the ANTSMC converges faster to a smaller region and reduces oscillations.

This paper focuses on controlling and optimizing a hybrid renewable energy system. The complex interactions and intermittent nature of renewable sources pose challenges to grid stability, necessitating sophisticated control strategies. The system includes a photovoltaic generator and a wind energy conversion system with a permanent magnet synchronous generator. Two key innovations are presented: i) connecting the photovoltaic generator to the grid in hybridization with the wind turbine without using a DC/DC converter, simplifying the structure, reducing losses, and ensuring grid stability and reliability; and ii) designing multi-objective controllers using the maximum power point tracking method based solely on electrical parameters, leading to fewer sensors and higher reliability compared to previous methods that required additional measurements like wind speed and irradiance. To address these challenges, a multiloop nonlinear controller is proposed, employing integral sliding mode and backstepping design techniques based on an accurate nonlinear system model. The stability of the multiloop control system is ensured using a suitable Lyapunov function.

The exponential stability for neutral delay Markovian jump systems with nonlinear perturbations and partially unknown transition rates is investigated in this paper. With creative Lyapunov functional and novel matrix inequalities analysis, delay-range-dependent and rate-dependent exponential stability conditions are presented by reciprocally convex lemma and free weighting matrices. Numerical examples are given to demonstrate the effectiveness of the proposed methods.

The goal of this paper is global disturbance rejection in nonlinear systems. An output feedback controller with disturbance rejection is developed for a class of nonlinear multi input-multi output (MIMO) systems. The availability of state variables and the bound of disturbances are not required to be known in advance and reference tracking will is guaranteed. By the aid of designing an adaptive observer, a robust adaptive nonlinear state feedback controller using the estimated states is proposed. For tracking problem, an adaptive pre-compensator is used. The control methodology is robust against both constant and time varying bounded disturbances, maintaining effective performance. The adaptive laws are derived based on the Lyapunov synthesis method, therefore closed-loop asymptotic stability is also guaranteed. Moreover, for chattering reduction we use a low-pass filter. Consequently, small gain theorem is adopted to prove the stability of the closed-loop system. Simulation results are employed to illustrate the effectiveness of the proposed controller.