High Performance Robust Control Research Articles

Research on High-Stability Composite Control Methods for Telescope Pointing Systems under Multiple Disturbances.

During the operation of space gravitational wave detectors, the constellation configuration formed by three satellites gradually deviates from the ideal 60° angle due to the periodic variations in orbits. To ensure the stability of inter-satellite laser links, active compensation of the breathing angle variation within the constellation plane is achieved by rotating the optical subassembly through the telescope pointing mechanism. This paper proposes a high-performance robust composite control method designed to enhance the robust stability, disturbance rejection, and tracking performance of the telescope pointing system. Specifically, based on the dynamic model of the telescope pointing mechanism and the disturbance noise model, an H∞ controller has been designed to ensure system stability and disturbance rejection capabilities. Meanwhile, employing the method of an H∞ norm optimized disturbance observer (HODOB) enhances the nonlinear friction rejection ability of the telescope pointing system. The simulation results indicate that, compared to the traditional disturbance observer (DOB) design, utilizing the HODOB method can enhance the tracking accuracy and pointing stability of the telescope pointing system by an order of magnitude. Furthermore, the proposed composite control method improves the overall system performance, ensuring that the stability of the telescope pointing system meets the 10 nrad/Hz1/2 @0.1 mHz~1 Hz requirement specified for the TianQin mission.

A Barrier Function-Based Variable Structure Control for Maglev System

Magnetic levitation (Maglev) systems are widely employed in the industry especially in mechatronics systems for precise positioning and suspension. They are inherently unstable having nonlinear models with uncertain parameters and exposed to external disturbances. Therefore, high-performance robust control designs are recommended for these systems. An Adaptive Variable Structure Controller based on barrier function (AVSCbf) is designed for the first time in this work to control the displacement of the ball position of a disturbed Maglev system. This approach does not require prior knowledge of the disturbance upper bounds in the design procedure. The state space region defined by the barrier function is designed to be attractive and invariant. This feature is essential to reject disturbances and handle parametric uncertainties. The adaptive law is activated when the state trajectory is initiated outside the invariant set defined by the barrier function. The gain of the VSC is adapted according to an adaptation law, which considers the system input constraints. The control input is constrained to be a bounded positive quantity. The adaptive VSC is only applied during the reaching phase. Once the state reaches the invariant set, the barrier-function-based VSC is applied to confine the state inside it. The resulting overall controller is a chattering-free VSC since the barrier-function based VSC is continuous. The steady-state error is limited to a minimal value by only specifying the barrier function parameter. Numerical simulations are conducted to show the efficiency of the new approach. Three types of VSC controllers for the Maglev system are compared. AVSCbf is compared to the performance of adaptive only VSC without the barrier function (AVSC) and both are designed in this work. AVSCbf is also compared to the classical VSC performance from previous work in the literature. The results of the comparison showed the efficiency of the proposed controller.

Discrete-Time Analysis and Synthesis of Disturbance Observer-Based Robust Force Control Systems

This paper analyses Disturbance Observer-(DOb-) based robust force control systems in the discrete-time domain. The robust force controller is implemented using velocity and acceleration measurements. A DOb is employed in an inner-loop to achieve robustness, and another DOb, viz. Reaction Force Observer (RFOb), is employed in an outer-loop to estimate interaction forces and improve the performance of force control. First, the inner-loop is analysed. It is shown that the DOb works as a phase-lead/lag compensator tuned by the nominal design parameters in the inner-loop. The phase margin of the inner-loop controller and the bandwidth of the velocity-based (i.e., conventional) DOb are constrained not only by noise-sensitivity but also by the waterbed effect. This explains why we observe unstable responses as the bandwidth of the conventional DOb increases in practice. To eliminate the design constraint due to the waterbed effect, this paper proposes an acceleration-based DOb. Then, the robust force controller is analysed. It is shown that the design parameters of the RFOb have a notable effect on the stability of the robust force control system. For example, the robust force controller has a non-minimum phase zero (zeros) when the RFOb is not properly tuned. This may cause severe stability and performance problems when conducting force control applications. By using the stability and robustness analyses, this paper proposes new design tools which enable one to synthesize a high-performance robust force control system. Simulations and experiments are presented to validate the proposed analysis and synthesis methods.

Iterative Feedback Tuning of Cascade Control of Two-Inertia System

The cascade control of the servo system has an inner control loop and an outer control loop to achieve high-performance robust control. However, additional efforts are required because the inner and outer controllers need to be sequentially tuned. To address this problem, this letter proposes a novel iterative feedback tuning method for cascade control. The proposed method adopts a cost function that is designed taking into consideration the cascade control structure and utilizes it for the IFT algorithm to simultaneously tune the inner and outer control loops. The effectiveness of the proposed method is verified by experiments using a two-inertia system which is subject to vibration. The experimental results verify that the proposed IFT can optimize the cascade controller under various plant conditions.

A Robust Hybrid of a Feedback Linearization Technique and an Interval Type-2 Fuzzy Control System for the Flapping Angle Dynamics of a Biomimetic Aircraft

We introduce a new configuration of a robust and adaptive autopilot system for a model-scale flapping-wing aircraft. The system is specifically designed to achieve high performance flapping angle tracking in the face of large uncertainties. To describe the dynamics of the system, we leverage the benefits of both first principle modeling and data-driven approach (system identification technique). We introduce a high-performance robust and adaptive nonlinear control system by means of a feedback linearization (FL) technique, supported with an interval Type-2 fuzzy system due to its ability to accommodate the footprint-of-uncertainties (FoUs). While the first stage of our nonlinear control system is to cancel some predictable nonlinearities using an FL technique, the second phase of control is to accommodate the existing uncertainties in the system by way of an interval Type-2 fuzzy control technique, e.g., due to imperfect cancelation and modeling errors. This way, the stability and the robustness of the closed-loop control system can be guaranteed. We quantify the relative merit of our hybrid control system with respect to an FL technique, supported with a fixed gain state feedback controller and a Type-1 fuzzy system. Lastly, we also conduct stability analysis of the overall closed-loop control system.

Performance Analysis of Disturbance Estimation Techniques for Robust Position Control of DC Motor

In this paper, the problem of high-performance robust position control of a DC motor based on the uncertainty and disturbance estimator (UDE) is presented. The UDE based sliding mode controller (SMC) is proposed which makes the system insensitive to the effect of Coulomb’s friction, parameter variations, and variable external load in DC motor. Fair comparison between UDE based SMC and existing classical technique is carried out by making PID as a robust controller by using Q-filter design. The different filter designs provide different estimates of nonlinearity, uncertainties, and external disturbances at a different resolution of position encoders. The proposed method guarantees robustness and ultimately eliminates the chattering phenomenon which is generally occurred in SMC.

High-Performance Robust Controller Design of Plug-In Hybrid Electric Vehicle for Frequency Regulation of Smart Grid Using Linear Matrix Inequality Approach

This paper proposes a high-performance and robust linear quadratic regulator-proportional integral derivative (LQR-PID) controller for frequency regulation in a two-area interconnected smart grid with a population of plug-in hybrid electric vehicles. Controller robustness is achieved using a linear matrix inequality approach. The proposed control framework is tested in a simulated two-area interconnected smart grid integrated with plug-in hybrid electric vehicles under load disturbances and wind power fluctuations. The performance of the proposed controller is simulated using Matlab and compared with that of a conventional linear quadratic regulator controller. Simulation results show that the proposed controller provides reliable smart grid frequency control.

Negative Imaginary Approached High Performance Robust Resonant Controller Design for Single-Phase Islanded Microgrid and Its Voltage Observation on Different Load Condition

This paper presents the design of a high performance robust resonant controller for the islanded single-phase microgrid operation on different loads conditions. The design of the controller is done using the results of Negative Imaginary approach. The performance of the proposed controller has been found much effective to track the instantaneous reference grid voltage. The simulation work has been done with the help of MATLAB/SimPower System toolbox. This shows that the proposed controller provides effective control of voltage against the uncertain load conditions.

A comparative study of high performance robust PID controller for grid voltage control of islanded microgrid

This paper presents the design of a robust proportional–integral–derivative controller for grid voltage control of an islanded microgrid. The microgrid consists of several distributed generation units and local loads. The loads are parametrically unknown and uncertain which ensure the variation of microgrid performance. The controller is designed to achieve fast transient response, zero steady-state error and robust performance in the presence of un-modeled loads, dynamic loads, nonlinear loads and harmonic loads. The performance of the controller is tested using MATLAB/Simulink SimPowerSystems. The simulation results show that the proposed controller is robust and provides high performance for voltage control of the islanded microgrid system by achieving the rise time, peak time, percentage of OS, and settling time of 0.00492, 0.018, 2.19, and 0.0271 ms.

High-Performance Robust Three-Axis Finite-Time Attitude Control Approach Incorporating Quaternion Based Estimation Scheme to Overactuated Spacecraft

With a focus on investigations in the area of overactuated spacecraft, a new high-performance robust three-axis finite-time attitude control approach, which is organized in connection with the quaternion based estimation scheme is proposed in the present research with respect to state-of-the-art. The approach proposed here is realized based upon double closed loops to deal with the angular rates of the system, in the inner loop, and also the rotational angles of the system in line with the corresponding quaternion, in the outer loop, synchronously. With this goal, a combination of the linear and its non-linear terms through the sliding mode control approach and also the proportional derivative based linear quadratic regulator control approach is organized. There is the white measurement noise to be realized the outcomes in such real situations, where it is coped with through the optimal estimation scheme to be designed, correspondingly. The investigated results are organized with regard to the pulse modulation synthesis through the technique of the pulse width pulse frequency to manage a set of on-off reaction thrusters, as long as the control allocation is employed to handle the aforementioned overactuated system under control. The effectiveness of the approach investigated is finally considered in line with a series of the experiments to be tangibly verified.

Adaptive Control of Active Dental Joint

In this paper, a PID model-based adaptive robust control method is proposed in order to design a high performance robust controller in the presence of structured (parametric) uncertainties and unstructured uncertainties. The approach improves performance by using the advantages of sliding mode control, adaptive control, and PID controller, while the disadvantages attributed to these methods are remedied by each other. This is achieved without increasing the complexities of the overall design and analysis of the control system (controller). The proposed controller attenuates the effect of model uncertainties from both structured uncertainties and unstructured uncertainties. Thus, transient performance and final tracking accuracy is guaranteed by proper design of the controller. Therefore, asymptotic tracking (or zero final tracking error) can be achieved without using high-gain feedback. The design is conceptually simple and is reliable in applications because of its high performance and strong robustness.

Nonlinear adaptive robust backstepping force control of hydraulic load simulator: Theory and experiments

High performance robust force control of hydraulic load simulator with constant but unknown hydraulic parameters is considered. In contrast to the linear control based on hydraulic linearization equations, hydraulic inherent nonlinear properties and uncertainties make the conventional feedback proportional-integral-derivative (PID) control not yield to high performance requirements. Furthermore, the hydraulic system may be subjected to non-smooth and discontinuous nonlinearities due to the directional change of valve opening. In this paper, based on a nonlinear system model of hydraulic load simulator, a discontinuous projection-based nonlinear adaptive robust back-stepping controller is developed with servo valve dynamics. The proposed controller constructs a novel stable adaptive controller and adaptation laws with additional pressure dynamic related unknown parameters, which can compensate for the system nonlinearities and uncertain parameters, meanwhile a well-designed robust controller is also synthesized to dominate the model uncertainties coming from both parametric uncertainties and uncertain nonlinearities including unmodeled and ignored system dynamics. The controller theoretically guarantee a prescribed transient performance and final tracking accuracy in presence of both parametric uncertainties and uncertain nonlinearities; while achieving asymptotic output tracking in the absence of unstructured uncertainties. The implementation issues are also discussed for controller simplification. Some comparative results are obtained to verify the high-performance nature of the proposed controller.

Enhancing ℋ ∞ Norm Estimation using Local LPM/LRM Modeling: Applied to an AVIS

Abstract Accurate uncertainty modeling is of key importance in high performance robust control design. The aim of this paper is to develop a new uncertainty modeling procedure that enhances the accuracy of the ℋ∞ norm. A frequency response based approach is adopted. The key novelty of this paper is a new method to address the intergrid error using local parametric modeling methods. These local polynomial and rational models enhance the estimates at the discrete frequency grid. Moreover, the presented methods are shown to enhance the intergrid error estimate. This is illustrated using simulations and experiments on an industrial active vibration isolation system. Compared to the local polynomial models, local rational models are able to handle lightly-damped resonances using far fewer data points.

Mathematical model for robust control of an irrigation main canal pool

This paper describes the formulation and development of a mathematical model for high-performance robust controller design techniques, based on a complete identification for control procedure, of an irrigation main canal pool (true plant), which is characterized by the exhibition of large variations in its dynamic parameters when the discharge regime changes in the operating range [Qmin, Qmax]. Real-time field data has been used. Four basic steps of the proposed procedure have been defined in which all the stages, from the design of the experiments to the model validation, are considered. This procedure not only delivers a nominal model of the true plant, but also a reliable estimate of its model uncertainty region bounded by the true plant models under minimum and maximum operating discharge regimes (limit operating models). The model uncertainty set, defined by the nominal model and its uncertainty region, is characterized by its being as tight as possible to the true irrigation main canal pool. The obtained results are very promising since this kind of models facilitates the design of robust controllers, which allow improving the operability of irrigation main canal pools and also substantially reduce water losses.

Robust control for a direct-driven permanent magnetic synchronous generator without mechanical sensors based on model reference adaptive backstepping control method

This article is concerned with the robust control issues of direct-driven permanent magnetic synchronous generator without mechanical sensors. In this study, a novel nonlinear model reference adaptive backstepping control method is proposed. Extended electromotive force estimation-based rotor position and rotational velocity estimation methods are adopted, in which the stator parameters are identified online. Since the identified parameters are merely used in extended electromotive force estimator, the mathematically controlled plant cannot reflect the actual model, which decreases the robustness of the control. To provide a high-performance robust controller against uncertainties in stator parameters and mechanical torque fluctuation, a torque observer is adopted, and an adaptation law is derived with the identified parameters and estimated mechanical torque, in the sense of the Lyapunov theory. Meanwhile, the feasibility of the substitution of the actual stator parameters and state vector with estimated values is mathematically demonstrated based on the Lyapunov theory. Simulation experiments have been carried out both in surface permanent magnetic synchronous generator and interior permanent magnetic synchronous generator, and the results show that compared to the conventional process-interaction decoupling controller, the proposed controller has better disturbance rejection performance against wind speed perpetuation and parameter uncertainties.

Non-linear sliding surface: towards high performance robust control

The study proposes a method to design a non-linear sliding surface to achieve better transient response for a class of single-input and single-output (SISO) non-linear uncertain system represented in a Brunowsky canonical form. The proposed surface can also be used for linear uncertain systems with matched perturbations. The proposed surface increases the damping ratio of the closed-loop system from its initial low value; as the output approaches the setpoint from its initial value. Initially, the system is lightly damped resulting in a quick response and as the output approaches the setpoint, the system is overdamped to avoid overshoot. The existence of sliding mode is proved and a new control law is proposed to enforce sliding motion. The scheme is able to achieve low overshoot and short settling time simultaneously which is not possible with a linear sliding surface. To ease the synthesis of the non-linear surface, linear matrix inequalities-based algorithm is proposed. Effectiveness of the proposed scheme is illustrated by the simulation results.

High Performance Control of Stewart Platform Manipulator Using Sliding Mode Control with Synchronization Error

This paper presents the design and analysis of a high performance robust controller for the Stewart platform manipulator. The controller is a variable structure controller that uses a linear sliding surface which is designed to drive both tracking and synchronization errors to zero. In the controller the model based equivalent control part of the sliding mode controller is computed in task space and the discontinuous switching controller part is computed in joint space and hence it is a hybrid of the two approaches. The hybrid implementation helps to reduce computation time and to achieve high performance in task space without the need to measure or estimate 6DOF task space positions. Effect of actuator friction, backlash and parameter variation due to loading have been studied and simulation results confirmed that the controller is robust and achieves better tracking accuracy than other types of sliding mode controllers and simple PID controller.

Performance improvement of robust controllers for polynomially uncertain systems

This paper is concerned with the high-performance robust control of discrete-time linear time-invariant (LTI) systems with semi-algebraic uncertainty regions. It is assumed that a robustly stabilizing static controller is given whose gain depends polynomially on the uncertain variables. The problem of tuning this parameter-dependent gain with respect to a prescribed quadratic cost function is formulated as a sum-of-squares (SOS) optimization. This method leads to a near-optimal controller whose performance is better than that of the initial controller. It is shown that the results derived in the present work encompass the ones obtained in a recent paper. The efficacy of the results is elucidated by an example.

高速光ディスク装置のための高性能エラー予測型ロバストトラッキング制御系

高速光ディスク装置のための高性能エラー予測型ロバストトラッキング制御系

Robust Quasi-time-optimal Discrete-time Sliding Mode Control of a Servomechanism

In this study, a new high-performance robust position control method is proposed. Robustness against system uncertainties is provided by discrete-time sliding mode control (DSMC) method. Quasi-optimal time-varying sliding surfaces are designed to ensure a high performance control. A new numerical method solving the time-optimal trajectory of the control system including friction is developed and implemented experimentally. Optimization of the system performance is aimed while the ranges of uncertainties and reference signals are kept as large as possible in a reasonable and practical manner. A new discount factor function especially determined for the investigated discrete-time control system is also proposed. Overshoots and oscillations that may occur in the case of high gain of switching function and large parameter variations are prevented. The proposed control method is applied to a vector controlled induction motor drive system. Experimental and simulation results showing the effects of the parameter variations and the wide range of the position reference on the system performance are presented.