Traditional Integral Controller Research Articles

Reinforcement Learning-Based Tracking Control under Stochastic Noise and Unmeasurable State for Tip–Tilt Mirror Systems

The tip–tilt mirror (TTM) is an important component of adaptive optics (AO) to achieve beam stabilization and pointing tracking. In many practical applications, the information of accurate TTM dynamics, complete system state, and noise characteristics is difficult to achieve due to the lack of sufficient sensors, which then restricts the implementation of high precision tracking control for TTM. To this end, this paper proposes a new method based on noisy-output feedback Q-learning. Without relying on neural networks or additional sensors, it infers the dynamics of the controlled system and reference jitter using only noisy measurements, thereby achieving optimal tracking control for the TTM system. We have established a modified Bellman equation based on estimation theory, directly linking noisy measurements to system performance. On this basis, a fast iterative learning of the control law is implemented through the adaptive transversal predictor and experience replay technique, making the algorithm more efficient. The proposed algorithm has been validated with an application to a TTM tracking control system, which is capable of quickly learning near-optimal control law under the interference of random noise. In terms of tracking performance, the method reduces the tracking error by up to 98.7% compared with the traditional integral control while maintaining a stable control process. Therefore, this approach may provide an intelligent solution for control issues in AO systems.

Load frequency and voltage control of two area interconnected power system using covariance matrix adaptation evolution strategy based Aquila optimization optimized fast fuzzy-fractional order tilt integral derivative controller

In this paper, an optimal tuning method is given for a Fast Fuzzy-Fractional Order Tilt Integral Derivative Controller (HFF-FOTIDC) used in the Load Frequency Control (LFC) and Automatic Voltage Regulator (AVR) systems of a two-area interconnected power system. LFC is in charge of managing the frequency and real power flows in the system. AVR is in charge of maintaining the voltage profile and managing the flow of reactive power. In Area 1, a step disturbance is used to study how the system works in a dynamic way. By looking at the system's voltage, power flow through the tie lines, and frequency, the experts can figure out how the system will react. The proposed control techniques combine two well established control logic, which are fast fuzzy control logic and fractional order tilt integral derivative control logic. The main goal is to decrease voltage and frequency changes caused by step disturbances and return them to their normal values. The simulation results show how good the suggested system is by comparing it to systems that use traditional proportional integral controllers and traditional Integral controllers. By using the finest tuning method for the fast fuzzy-fractional order tilt integral derivative controller, the designed system has better performance than standard controllers at reducing fluctuations and getting the desired frequency and voltage responses. The parameters of the proposed controller are optimized by using Covariance Matrix Adaptation Evolution Strategy based Aquila Optimization (CMAESAO) optimization technique.

Automatic Transmission Grid Control of Active Distribution Networks

Active distribution networks (ADNs) intend to manage the escalating computational complexity of renewable power grids by providing controlled subdivisions which support the operation of the transmission grid in some way. They display complex dynamical behavior greatly influenced by the chosen controllers and themselves pose a variety of challenges for the transmission grid. This work describes all elements of a continuous-time controller architecture for ADNs connected to each other through the transmission grid in a low-carbon environment including the controllers of the ADNs and the controllers of the transmission grid. Time-domain simulations are carried out for validation to illustrate the response, with a more traditional integral controller used for comparison.

An anti-slip control strategy with modifying target and torque reallocation for heavy in-wheel motor vehicle

In-wheel motors are used in heavy vehicles such as buses and trucks to improve efficiency and compactness, the safety of which is particularly important. Anti-slip control is applied to road vehicles to improve the active safety performance, and it is necessary for heavy in-wheel motor vehicles. However, the experiment results in this study show that the response delay of motors on the heavy vehicle is larger than that of the passenger car, and the vehicle mass often changes, which brings drawbacks to the rapidity and stability of its dynamics control. For these problems, an improved Proportional-Derivative Control with a modifying desired wheel rotational speed is proposed for the slip regulation. The modifying control target is intended to mitigate steady tracking error, the role of which is similar to the traditional Integral Control. The desired wheel rotational speed is modified through the response in the current period, and then is set as the new target in the next period. Because the anti-slip control of driving wheels on each side is independent, the torque reallocation strategy is introduced to coordinate with the yaw control and take the yaw dynamics into account, which therefore improves the lateral stability. To avoid the excessive driving torque increment causing the slipping phenomenon again, after the anti-slip control finishing, a transition process is applied. Finally, simulations and real vehicle experiments are conducted to verify the effectiveness and flexibility of the control algorithm, and the results indicate that the control strategy has an expected performance.

Bounded Integral Controller With Limited Control Power for Nonlinear Multiple-Input Multiple-Output Systems

In this brief, a bounded integral controller (BIC) with limited control power is proposed for a class of nonlinear multiple-input multiple-output (MIMO) systems. The sum-of-squares constraint on the control inputs with time-varying weights is studied and handled through the BIC design, which guarantees that both the control inputs and an auxiliary time-varying variable are dynamically constrained on a designed control circle. The BIC inherits the properties of the traditional integral controller to eliminate tracking errors and achieve disturbance rejections. Even under time-varying input weights, the BIC guarantees limited control power independently of both plant information and system states. The input-to-state (practical) stability of the closed-loop system is established. To demonstrate the effectiveness of the proposed method, experimental validations are conducted for two systems: a system with multiple dc motors subject to a power limit with time-varying input weights and a permanent magnet synchronous motor system subject to a voltage limit with time-invariant input weights.

Synchronization of Power Grid by HVDC Technology

This research work expose the advantages of HVDC technology for synchronization of two interconnected thermal power grid of 12 areas when load disturbance occur in power grid-1. Three types of tie-lines HVAC–1HVDC parallel tie-line, HVAC– 2HVDC parallel tie-line and HVAC–3HVDC parallel tie-line are applied for synchronization of 12 area two interconnected thermal power grid. For synchronization purpose of power grid this research work shows the HVAC–3HVDC parallel tie-line is better as compare to the HVAC–2HVDC parallel tie-line and HVAC–1HVDC parallel tie-lie. This research work also shows the HVAC–2HVDC parallel tie-line is better as compare to the HVAC–1HVDC parallel tie-line. Quality of all three types of tie-line is judged by the frequency deviation of two interconnected power grid of 12 areas when load disturbance occur in power grid-1. The biggest advantage of this research work is that the two interconnected thermal power grid of 12 areas is Synchronize by HVDC technology with traditional integral controller.

Power-Imbalance Allocation Control of Power Systems-Secondary Frequency Control

The traditional secondary frequency control of power systems restores nominal frequency by steering Area Control Errors (ACEs) to zero. Existing methods are a form of integral control with the characteristic that large control gain coefficients introduce an overshoot and small ones result in a slow convergence to a steady state. In order to deal with the large frequency deviation problem, which is the main concern of the power system integrated with a large number of renewable energy, a faster convergence is critical. In this paper, we propose a secondary frequency control method named Power-Imbalance Allocation Control (PIAC) to restore the nominal frequency with a minimized control cost, in which a coordinator estimates the power imbalance and dispatches the control inputs to the controllers after solving an economic power dispatch problem. The power imbalance estimation converges exponentially in PIAC, both overshoots and large frequency deviations are avoided. In addition, when PIAC is implemented in a multi-area controlled network, the controllers of an area are independent of the disturbance of the neighbor areas, which allows an asynchronous control in the multi-area network. A Lyapunov stability analysis shows that PIAC is locally asymptotically stable and simulation results illustrate that it effectively eliminates the drawback of the traditional integral control based methods.

Enhanced Bounded Integral Control of Input-to-State Stable Nonlinear Systems

The bounded integral controller (BIC) was recently proposed to replace the traditional integral controller (IC) for the regulation of any input-to-state stable (ISS) nonlinear system and guarantee closed-loop system stability with a bounded control output. In this paper, an enhanced version of the BIC is presented to provide a better approximation of the traditional IC in the entire bounded range of the control output and relax the assumption on the selection of the initial conditions of the original BIC. Using Lyapunov methods, it is analytically proven that the enhanced BIC maintains the zero-gain property and guarantees closed-loop stability of any nonlinear ISS plant with a given bound at the control output, without suffering from integrator windup issues. The plant dynamics and structure can be unkown as long as the plant is ISS. Hence, the proposed enhanced version of the BIC can replace the traditional IC in many applications where closed-loop stability cannot be proven, without changing the controller operation. A practical example is simulated to verify the performance of the proposed enhanced BIC compared to the original version and the traditional IC.

Bounded Integral Control of Input-to-State Practically Stable Nonlinear Systems to Guarantee Closed-Loop Stability

A fundamental problem in control systems theory is that stability is not always guaranteed for a closed-loop system even if the plant is open-loop stable. With the only knowledge of the input-to-state (practical) stability (ISpS) of the plant, in this note, a bounded integral controller (BIC) is proposed which generates a bounded control output independently from the plant parameters and states and guarantees closed-loop system stability in the sense of boundedness. When a given bound is required for the control output, an analytic selection of the BIC parameters is proposed and its performance is investigated using Lyapunov methods, extending the result for locally ISpS plant systems. Additionally, it is shown that the BIC can replace the traditional integral controller (IC) and guarantee asymptotic stability of the desired equilibrium point under certain conditions, with a guaranteed bound for the solution of the closed-loop system. Simulation results of a dc/dc buck-boost power converter system are provided to compare the BIC with the IC operation.

Distributed composite autopilot design for bank-to-turn missiles with optimized tracking based on disturbance observers

Robust autopilot design for bank-to-turn (BTT) missiles under time-varying aerodynamic parameters, heavy nonlinear crossing couplings and external disturbances is investigated in this article by employing a distributed composite control framework. The dynamics of the BTT missiles are separated into three subsystems from the roll, yaw and pitch channels. For each subsystem, a composite control framework consists of a low-level state feedback stabilizer, a high-level model predictive controller and a feedforward compensator based on a disturbance observer. Simulation results demonstrate that compared with the baseline control and traditional integral control approaches, the proposed control strategy exhibits promising guidance command tracking and robustness against external disturbances, nonlinear crossing couplings and aerodynamic parameter perturbations.

Robust Control of a Two-Terminal Cryogenic Current Comparator

A digital $H\infty$ controller for a two-terminal cryogenic current comparator is designed. To this end, a set of mathematical models covering the actual system is proposed. Simulation results compare the open- and closed-loop systems based on the proposed controller and the traditional integral control. According to these results, the new controller can significantly reduce the noise in the superconducting quantum interference device sensor.

A New Method for Robust Damping and Tracking Control of Scanning Probe Microscope Positioning Stages

This paper demonstrates a simple second-order controller that eliminates scan-induced oscillation and provides integral tracking action. The controller can be retrofitted to any scanning probe microscope with position sensors by implementing a simple digital controller or operational amplifier circuit. The controller is demonstrated to improve the tracking bandwidth of an NT-MDT scanning probe microscope from 15 Hz (with an integral controller) to 490 Hz while simultaneously improving gain-margin from 2 to 7 dB. The penalty on sensor induced positioning noise is minimal. A unique benefit of the proposed control scheme is the performance and stability robustness with respect to variations in resonance frequency. This is demonstrated experimentally by a change in resonance frequency from 934 to 140 Hz. This change does not compromise stability or significantly degrade performance. For the scanning probe microscope considered in this paper, the noise is marginally increased from 0.30 to 0.39 nm rms. Open and closed-loop experimental images of a calibration standard are reported at speeds of 1, 10, and 31 lines per second (with a scanner resonance frequency of 290 Hz). Compared with traditional integral controllers, the proposed controller provides a bandwidth improvement of greater than 10 times. This allows faster imaging and less tracking lag at low speeds.