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In this article, continuous and discontinuous integral controllers for multiple‐input multiple‐output (MIMO) systems are designed for a large class of nonlinear systems, which are (partially) feedback linearizable. These controllers of arbitrary positive or negative degree of homogeneity are derived by combining a Lyapunov function obtained from the implicit Lyapunov function (ILF) method with some extra explicit terms. Discontinuous integral controllers are able to stabilize an equilibrium or track a time‐varying signal in finite time, while rejecting vanishing uncertainties and nonvanishing Lipschitz matching perturbations. Continuous integral controllers achieve asymptotic stabilization despite nonvanishing constant perturbations in finite‐time, exponentially or nearly fixed‐time for negative, zero, or positive homogeneity degree, respectively. The design method and the properties of the different classes of integral controllers are illustrated by means of a simulation example. [ABSTRACT FROM AUTHOR]

This paper presents a robust control regarding position control of an electro-hydraulic rotary actuator (EHRA) system under the presence of the lumped uncertainties such as the variant payload, the unknown friction, and the uncertain parameters. The proposed control is developed on a high order sliding mode control (HOSMC) and an extended high gain observer (EHGO). In detail, the HOSMC is derived to not only reduce the chattering effect but also guarantee the stability for the EHRA. In addition, the EHGO is used as a disturbance estimator to compensate the lumped uncertainties. Consequently, it helps to improve control performance. Furthermore, the stability and robustness of the whole system are theoretically proved by a Lyapunov approach. The proposed control is practically implemented through both the co-simulation between AMESIM and MATLAB, and the experiments. The results are compared to other controllers to exhibit the effectiveness of the proposed control with the lumped uncertainties. [ABSTRACT FROM AUTHOR]

Proposed in this paper is a model-free and chattering-free second order sliding mode control (2nd-SMC) in combination with a backpropagation neural network (BP-NN) control scheme for underwater vehicles to deal with external disturbances (i.e., ocean currents) and parameter variations caused, for instance, by the continuous interchange of tools. The compound controller, here called the neuro-sliding control (NSC), takes advantage of the 2nd-SMC robustness and fast response to drive the position tracking error to zero. Simultaneously, the BP-NN contributes with its capability to estimate and to compensate online the hydrodynamic variations of the vehicle. When a change in the vehicle’s hydrodynamics occurs, the 2nd-SMC may no longer be able to compensate for the variations since its feedback gains are tuned for a different condition; thus, in order to preserve the desired performance, it is necessary to re-tune the feedback gains, which a cumbersome and time consuming task. To solve this, a viable choice is to implement a BP-NN control scheme along with the 2nd-SMC that adds or removes energy from the system according to the current condition it is in, in order to keep, or even improve, its performance. The effectiveness of the proposed compound controller was supported by experiments carried out on a mini-ROV.

This paper presents a decentralized coordinated excitation and steam valve adaptive control combined with a high-order sliding mode differentiator. The aim is to obtain high performance for the terminal voltage and the rotor speed simultaneously under a sudden fault and a wide range of operating conditions. The methodology adopted is based on second order sliding mode technique using the supper twisting algorithm. The proposed scheme requires only local information on the physically available measurements of relative angular speed, active electric power and terminal voltage with the assumption that the power angle and mechanical power input are not available for measurement. It can be implemented locally and dispersedly for individual generators and is convenient for industrial applications. Simulation results in the case of the Kundur 4-machines 2-area power system show the effectiveness, robustness and superiority of the proposed scheme over the classical AVR/PSS controller and steam valve PI regulator. [ABSTRACT FROM AUTHOR]

Transparency has been a major objective in bilateral teleoperation systems, even in the absence of time delay induced by the communication channel, since a high degree of transparency would allow humans to drive the remote teleoperator as if he or she were directly interacting with the remote environment, with the remote teleoperator as a physical and sensorial extension of the operator. When fast convergence of position and force tracking errors are ensured by the control system, then complete transparency is obtained, which would ideally guarantee humans to be tightly kinaesthetically coupled. In this paper a model-free Cartesian second order sliding mode (SOSM) PD control scheme for nonlinear master-slave systems is presented. The proposed scheme does not rely on velocity measurements and attains very fast convergence of position trajectories, with bounded tracking of force trajectories, rendering a high degree of transparency with lesser knowledge of the system. The degree of transparency can easily be improved by tuning a feedback gain in the force loop. A unique energy storage function is introduced; such that a similar Cartesian-based controller is implemented in the master and slave sides. The resulting properties of the Cartesian control structure allows the human operator to input directly Cartesian variables, which makes clearer the kinaesthetic coupling, thus the proposed controller becomes a suitable candidate for practical implementation. The performance of the proposed scheme is evaluated in a semi-experimental setup. [ABSTRACT FROM AUTHOR]

Underwater remotely operated vehicles (ROVs) play an important role in a number of shallow and deep-water missions for marine science, oil and gas extraction, exploration and salvage. In these applications, the motions of the ROV are guided either by a human pilot on a surface support vessel through an umbilical cord providing power and telemetry, or by an automatic pilot. In the case of automatic control, ROV state feedback is provided by acoustic and inertial sensors and this state information, along with a controller strategy, is used to perform several tasks such as station-keeping and auto-immersion/heading, among others. In this paper, the modelling, design and control of the Kaxan ROV is presented: i) The complete six degrees of freedom, non linear hydrodynamic model with its parameters, ii) the Kaxan hardware/software architecture, iii) numerical simulations in Matlab/Simulink platform of a model-free second order sliding mode control along with ocean currents as disturbances and thruster dynamics, iv) a virtual environment to visualize the motion of the Kaxan ROV and v) experimental results of a one degree of freedom underwater system. [ABSTRACT FROM AUTHOR]

Abstract: The problem of robust output feedback control and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle (FAHV) is investigated in this paper. A control-oriented uncertainty model is established for the feedback linearization design, and the multi-input and multi-output (MIMO) quasi-continuous high-order sliding mode (HOSM) controller is formulated to track the responses of the vehicle to a step change in velocity and altitude based on full state feedback. In addition, a high order sliding mode observer is designed to estimate the angle of attack and the flight path angle, which are difficult to measure in a hypersonic flight. Furthermore, the combination of the HOSM controller and observer is proposed for vehicle model with partial state measurements. The simulation results are presented to verify the effectiveness of the proposed control strategy. [Copyright &y& Elsevier]

Abstract: In this paper, feedback linearization approach and high order sliding mode control are combined to stabilize and decentralize nonlinear multimachine power systems. The design control permits to decentralize and handle the nonlinearities of power systems model by using the feedback linearization approach and HOSM control to each generating unit in the global system for stabilizing the system. Each machine is modeled as an independent uncertain dynamic subsystem where the uncertainty is a disturbance that represents the effects of the rest of the system on that particular machine. This disturbance is estimated by numerical method. A local high order sliding mode stabilizer is designed to regulate the machine angle of each generating unit under high level external disturbances. This method is illustrated with a three-machines infinite bus power system. Simulations show that the proposed (DHOSMC) provides high-performance in dynamic characteristics and its robustness with regard to external disturbance. [Copyright &y& Elsevier]

In this study, Sliding Mode Control (SMC) and High Order Sliding Mode Control (HOSMC) methods are applied to a single Flexible Link Robot Arm (FLA) with payload. A sliding mode and high order sliding mode controllers are designed to achieve set point precision positioning control and trajectory tracking control for a FLA. Flexible robot arms have structural flexibilities and resulting high number of passive degrees-of-freedom. They cannot be decoupled due to the highly nonlinear structure. Since the flexible systems have highly nonlinear structure and coupled dynamics, the sliding mode based control approach is chosen a powerful method to overcome the unmodeled and parametric uncertainties. One of the proposed controllers is 2nd order HOSMC method is compared with classical SMC method. Comparison of the methods is experimentally fulfilled using HIL simulator, and additionally torque ripple analysis is made to evaluate of the methods aspect from system harmonics. Direct drive motors are used as actuator in controlled systems. Of all system dynamics affect system harmonics via motor shaft due to the direct drive system that is no gear box. Therefore, harmonics analysis is crucial to investigate of designed controllers effects on system harmonics. To precise set-point and trajectory tracking control of 1-DOF DD FLA has been derived SMC and HOSMC. Sliding Mode Controllers (SMCs) have the robustness properties, while also increasing accuracy by reducing chattering effects. The performance of the designed control methods are tested for the precise position and targeting control of a 1- DOF-DD-FLA system under heavy uncertainties. Comparative results of both methods have been evaluated in real-time using a Hardware-in-the- Loop (HIL) simulator designed for robotics. Especially, HIL simulator for this system includes DD motors and obtained results can be evaluated more realistically according to pure computer simulations Additionally, torque ripples of whole system with HIL simulator have been determined and their eliminations using for both methods are introduced. HIL simulator is used to implement designed controller for a flexible-link arm. Direct drive joint motors are important parts of the direct drive underactuated robot manipulators. Therefore two DD motors take part in HIL simulator and couple through their shaft. One of the motors represents joint actuator, while the other motor is used for generation of the dynamics of the controlled system via the torque applied to the shaft. The two motors acting as "actuator" and "load torque simulator" are driven separately by a high performance controller board. HIL Simulator is expressed briefly as software that is modeled control algorithm and system dynamic model via controller board is integrated with hardware. HIL simulation differs from computer simulation as it involves actual hardware and is not limited with a software-based representation of the system.… [ABSTRACT FROM AUTHOR]

In modern data acquisition and communication technologies, the differential coding scheme known as Delta Modulation (Δ -M) is being rediscovered as an efficient 1-bit analog-to-digital conversion and compression technique due to its simplicity in implementation, high resolution and minimal data throughput rate. In this paper it is proposed a second-order Δ -M scheme based on the second-order "suboptimal" sliding mode control technique. As compared to the traditional Δ -M scheme, based on the first-order sliding mode control paradigm, it yields better accuracy and noise-shaping properties as well as higher signal-to-noise ratio. Various dynamical features of the proposed scheme are investigated, both in continuous and discrete time domains, and the appropriate stability conditions are derived. Finally, numerical simulations are extensively discussed to corroborate the theoretical analysis. [ABSTRACT FROM AUTHOR]

Proposed in this paper is a model-free and chattering-free second order sliding mode control (2nd-SMC) in combination with a backpropagation neural network (BP-NN) control scheme for underwater vehicles to deal with external disturbances (i.e., ocean currents) and parameter variations caused, for instance, by the continuous interchange of tools. The compound controller, here called the neuro-sliding control (NSC), takes advantage of the 2nd-SMC robustness and fast response to drive the position tracking error to zero. Simultaneously, the BP-NN contributes with its capability to estimate and to compensate online the hydrodynamic variations of the vehicle. When a change in the vehicle's hydrodynamics occurs, the 2nd-SMC may no longer be able to compensate for the variations since its feedback gains are tuned for a different condition; thus, in order to preserve the desired performance, it is necessary to re-tune the feedback gains, which a cumbersome and time consuming task. To solve this, a viable choice is to implement a BP-NN control scheme along with the 2nd-SMC that adds or removes energy from the system according to the current condition it is in, in order to keep, or even improve, its performance. The effectiveness of the proposed compound controller was supported by experiments carried out on a mini-ROV. [ABSTRACT FROM AUTHOR]