Feedforward Compensator Design Research Articles

Adaptive Output Feedback Control Design with Adaptive Parallel Feedforward Compensator and Feedforward Input via Kernel Method for Nonlinear System

It is well recognized that an adaptive output feedback control based on almost strictly positive real‐ness (ASPR) or output feedback strictly passivity (OFSP) property of the system has strong robustness with respect to disturbances and uncertainty. However, most practical systems do not have such properties. In order to realize an augmented ASPR system for designing adaptive output feedback controller, a kind of adaptive parallel feedforward compensator (PFC) design schemes have been proposed for linear systems. In this paper, we propose an adaptive PFC design scheme by Kernel method for nonlinear systems and provide output feedback passivity based adaptive output feedback control for nonlinear systems. The effectiveness of the proposed method will be confirmed through numerical simulations. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Nonlinear identification and optimal feedforward friction compensation for a motion platform

In this study, we present a method of nonlinear identification and optimal feedforward friction compensation for an industrial single degree of freedom motion platform. The platform has precise reference tracking requirements while suffering from nonlinear dynamic effects, such as friction and backlash in the driveline. To eliminate nonlinear dynamic effects and achieve precise reference tracking, we first identified the nonlinear dynamics of the platform using Higher Order Sinusoidal Input Describing Function (HOSIDF) based system identification. Next, we present optimal feedforward compensation design to improve reference tracking performance. We modeled the friction using the Stribeck model and identified its parameters through a procedure including a special reference signal and the Nelder–Mead algorithm. Our results show that the RMS trajectory tracking error decreased from 0.0431 deg/s to 0.0117 deg/s when the proposed nonlinear identification and friction compensation method is utilized.

Online Compensation of Mechanical Load Defects With Composite Control in PMSM Drives

Online monitoring of various faults that are associated with the permanent magnet synchronous motor (PMSM) is receiving much attention with the increasing demand in PMSM applications. Mechanical load imbalance is one of the mechanical defects that causes increase in the torque ripple, motor vibration, and can lead to accelerated wear and unstable drive operation, if the fault is undetected. Unlike existing methods that are limited to detection of rotor defects, in this article, a novel composite-control scheme is designed to estimate and compensate for the load torque disturbance (produced due to load imbalance) in the feedforward compensation design. It is shown that the proposed design with the feedback control law provides accurate compensation of load torque disturbance and achieves high-precision speed control (improved tracking performance up to 90% and smaller convergence time of up to 70%). Simulations as well as experimental testing validate the effectiveness and reliability of the proposed scheme.

Adaptive Feedforward Compensation for Voltage Source Disturbance Rejection in DC–DC Converters

Jumping disturbances and large noises in input voltage sources to a power converter can cause substantial excursion of its output voltage even under a well-designed feedback controller. Predictive compensation can achieve improved disturbance rejection and tracking performance in such scenarios, resulting in a two-degree-of-freedom design. While the feedback controller has embedded robustness, designing feedforward controllers, which are open-loop compensators, is challenging due to the fact that converter internal parameters change from aging and variations in operating conditions, and loads themselves are part of the converter dynamics. When converter dynamics change, system performance deteriorates significantly, making adaptation mandatory. By integrating system identification with the feedforward compensator, an adaptive feedforward compensation design is proposed in this brief. Working on a boost dc–dc converter as a typical platform, combined feedback and adaptive feedforward design is explored. The results show that the two-degree-of-freedom adaptive design results in much improved performance in rejecting disturbances from input power sources.

Adaptive composite control method of permanent magnet synchronous motor systems

With the development of digital signal processes, the relative differences of PMSM single loop in control periods between the speed loop and current loops are becoming smaller or even vanishing. Therefore, cascade control schemes seem to be unnecessary. In addition, considering the effects of disturbances and the variety of moments of inertia, this paper proposes a scheme using an adaptive non-cascade control method to design the controller, which merges speed loop and q-axis current loop into one single loop. First, an extended state observer (ESO) is employed to estimate the disturbances of the system. The estimated value is used in the feedforward compensation design to improve the capability of system anti-disturbance. Then, considering the performance degradation caused by inertia change, an adaptive control scheme is developed. By using inertia identification technology, the feedforward compensation gain can be tuned automatically according to the identification value. Several groups of simulations and experiments are carried out and the results demonstrate the effectiveness of the proposed scheme.

A composite current-constrained control for permanent magnet synchronous motor with time-varying disturbance

The problem of overlarge current protection of permanent magnet synchronous motor based on a single-loop control structure is discussed in this article. Under this structure, the previous limiting method of amplitude of q-axis current used in field-oriented control is unsuitable, which limits q-axis current by restricting the output of reference current. Conventional controllers (e.g. proportional–integral–derivative controller) usually cannot have a nice balance between satisfaction of current constraint and requirement of fast dynamic performance. Overlarge current may cause the damage of hardware. Aiming at this issue, a composite controller is proposed. Different from previous methods of state constraints, the effects of disturbance is taken into account of controller design. First, a finite-time current-constrained feedback control technique based on homogeneous approach is applied in the feedback design. Compared with conventional finite-time control, a punishment mechanism of over-current is added into the gain of controller. Second, a generalized proportional integral observer is adopted to estimate the uncertainties and disturbances. The estimated value is used in the feed-forward compensation design. Compared with the conventional proportional–integral–derivative controller and proportional–derivative + extended state observer controller, the proposed method not only limits q-axis current to a safe range but also shows a nice dynamic performance and a strong anti-disturbance ability. Both simulations and experiments are carried out, and the results demonstrate the effectiveness of the proposed control scheme.

Adaptive Combustion Control System Design of Diesel Engine via ASPR Based Adaptive Output Feedback with a PFC

[abstFig src='/00280005/07.jpg' width='300' text='Adaptive engine combustion control system' ] This paper deals with a combustion control system design problem of diesel engine. For a combustion model of diesel engine, which has been provided for on-board control, an adaptive control system based on an adaptive output feedback control with a simple adaptive feedforward input will be proposed based on the “almost strictly positive real-ness” (ASPR-ness) of the controlled system. A simple parallel feedforward compensator (PFC) design scheme, which renders the resulting augmented controlled system ASPR, will also be proposed based on basic combustion model properties to design stable adaptive control system for the diesel engine combustion control. The effectiveness of our proposal is confirmed through numerical simulation.

Combustion Control System Design of Diesel Engine via ASPR based Output Feedback Control Strategy with a PFC

In this paper, a design method of an output feedback control system with a simple feedforward input for a combustion model of diesel engine will be proposed based on the almost strictly positive real-ness (ASPR-ness) of the controlled system for a combustion control of diesel engines. A parallel feedforward compensator (PFC) design scheme which renders the resulting augmented controlled system ASPR will also be proposed in order to design a stable output feedback control system for the considered combustion model. The effectiveness of our proposed method will be confirmed through numerical simulations.

DOB-based piezoelectric vibration control for stiffened plate considering accelerometer measurement noise

This paper presents a composite control strategy for the active suppression of vibration due to the unknown disturbances, such as external excitation, harmonic effects and control spillover, as well as high-frequency accelerometer measurement noise in the all-clamped stiffened plate. The proposed composite control action based on the modal approach, consists of two contributions including feedback part and feedforward part. The feedback part is the well-known PID controller, which is widely used to increase the structure damping and improve its dynamic performance close to the resonance frequencies. In order to get better performance for vibration suppression, the weight matrixes is optimized by chaos sequence. Then an improved disturbance observer (IDOB) as the feedforward compensation part is developed to enhance the vibration suppression performance of PID under various disturbances and uncertainties. The proposed IDOB can simultaneously estimate the various disturbances dynamically as well as measurement noise acting on the system and suppress them by feedforward compensation design. A rigorous analysis is also given to show why the IDOB can effectively suppress the unknown disturbances and measurement noise. In order to verify the proposed composite control algorithm (IDOB-PID), the dSPACE real-time simulation platform is used and an experimental platform for the all-clamped stiffened plate active vibration control system is set up. The experimental results demonstrate the effectiveness, practicality and strong anti-disturbances ability of the proposed control strategy.

Optimal feedforward compensators for integrating plants

This paper addresses the design of feedforward compensators for integrating processes. Initially, the disturbance rejection problem for a classic two degrees-of-freedom control scheme with feedfoward is analyzed to highlight the problem caused by integrating dynamics. Afterwards, two simple tuning rules are derived to obtain undershoot-free responses based only a desired settling time or by satisfying a tradeoff between maximum peak and settling time specifications. Finally, some simulations are shown to prove the advantages of the proposed controller.

Nonlinear Compensators of Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems using Air Path Models for a CRDI Diesel Engine

This paper investigates the design of model-based feedforward compensators for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems using air path models for a common-rail direct injection (CRDI) diesel engine to cope with the nonlinear control problem. The model-based feedforward compensators generate set-positions of the EGR valve and the VGT vane to track the desired mass air flow (MAF) and manifold absolute pressure (MAP) with consideration of the current engine operating conditions. In the best case, the rising time to reach 90% of the MAF set-point was reduced by 69.8% compared with the look-up table based feedforward compensators.

DOB Design for Nonminimum-Phase Delay Systems and Its Application in Multivariable MPC Control

This brief first presents an improved disturbance observer (IDOB) design method to deal with disturbance observation for the nonminimum-phase delay systems. Then, an IDOB-based compound control scheme is developed to enhance the disturbance rejection performance of multivariable model predictive control (MPC) under various disturbances and uncertainties. In such an IDOB–MPC scheme, the MPC controller acts as a prefilter and generates appropriate control actions such that a desired setpoint tracking response is achieved. The IDOB is used to estimate the various disturbances dynamically and suppress them by feedforward compensation design. Both theory analysis and simulation comparisons have shown good disturbance estimation and rejection performances of the proposed method.

A feedforward compensation design in critical conduction mode boost power factor correction for low-power low totalharmonic distortion

For low-power low total harmonic distortion (THD), based on the CSMC 0.5 μm BCD process, a novel boost power factor correction (PFC) converter in critical conduction mode is discussed and analyzed. Feedforward compensation design is introduced in order to increase the PWM duty cycle and supply more conversion energy near the input voltage zero-crossing points, thus regulating the inductor current of the PFC converter and compensating the system loop gain change with ac line voltage. Both theoretical and practical results reveal that the proposed PFC converter with feedforward compensation cell has better power factor and THD performance, and is suitable for low-power low THD design applications. The experimental THD of the boost PFC converter is 4.5%, the start-up current is 54 μA, the stable operating current is 3.85 mA, the power factor is 0.998 and the efficiency is 95.2%.

Adaptive speed control of a PMSM servo system using an RBFN disturbance observer

In order to improve the disturbance rejection property of Permanent-Magnet Synchronous Motor servo systems, a novel adaptive composite control method for the speed regulation problem is proposed in this paper. The composite controller is composed of a proportional feedback controller and a feedforward compensation based on a Radial Basis Function Network Disturbance Observer (P+RBFNDOB). The RBFNDOB is designed to estimate the lumped disturbances, including external disturbances and internal disturbances caused by parameter variations, and the estimation value is used for feedforward compensation design. Different from traditional Linear DOB (LDOB), an RBFN is used to approximate the inverse model of the system instead of selecting the inverse of the nominal model as in LDOB. By using an on-line learning algorithm, the identified inverse model can track the variations of the real plant. Thus, the RBFNDOB can still observe the disturbances when the parameters of the system vary in a wide range, while conventional DOB may not be suitable in such situations. So the composite controller obtained is inherently robust against parameter variations and external disturbances. A nearest neighbour clustering algorithm combining crude regulation and fine regulation is introduced as the on-line learning method to simplify the network structure and accelerate the learning speed. Rigorous analysis is also given to show why the RBFNDOB can effectively suppress the lumped disturbances of a closed-loop system. Simulation comparisons with two other methods, the composite control method with proportional feedback plus feedforward compensation based on LDOB (P+LDOB) and the conventional PI control method, verify the effectiveness of the proposed method.

Piezoelectric vibration control for all-clamped panel using DOB-based optimal control

Considering the spillover and harmonic effect in real active vibration control, a novel composite controller based on disturbance observer (DOB) for the all-clamped panel is presented. The single-mode of the piezoelectric panel can be regarded as a second-order system. The unmodeled error of the current controlled mode, harmonic effects, uncontrolled mode effects, etc., are regarded as the lumped disturbances which can be estimated by the DOB, and the estimated value is used for the feed-forward compensation design. Then, an optimal linear quadratic regulator (LQR) strategy is employed for the feedback design. In order to solve the difficulty of determining the weight matrices of LQR, a chaos optimization method based on logistic map is proposed. So the weight matrices can be tuned automatically. Combining with a new transient performance function, the optimal weight matrices can be obtained. The composite controller can effectively suppress the lumped disturbances of the all-clamped panel. Experiment comparisons with conventional LQR are given to verify the effectiveness of the proposed method.

Simple tuning rules for feedforward compensators

This paper describes new simple tuning rules for design of feedforward compensators. The problem of feedforward from load disturbances is analyzed, and it is shown that the feedback controller should be taken into account in the feedforward design process. Simple rules based on IAE minimization with restrictions on the process output overshoot and the high-frequency gain of the compensator are then derived. Several simulations are presented along the paper to show the advantages of the proposed design rules.

A pre- + post- + feedforward compensator design for zero placement

We demonstrate the design of a pre- + post- + feedforward compensator that places the transmission zeros of a stabilisable and detectable multi-input multi-output linear-time-invariant plant at arbitrary locations.

Disturbance rejection of dead-time processes using disturbance observer and model predictive control

This article mainly focuses on disturbance rejection of dead-time processes by integrating a modified disturbance observer (MDOB) with a model predictive controller (MPC). The effect caused by model mismatches is regarded as a part of the lumped disturbances. This means that the disturbances considered here include not only external disturbances, but also internal disturbances caused by model mismatches. Control structure of the proposed method includes two parts which can be designed separately. The MPC which acts as a prefilter, is employed to generate appropriate control actions such that a desired setpoint tracking response is achieved. The MDOB is employed to estimate the disturbances of the closed-loop system, and the estimation is used for feedforward compensation design to reject disturbances. Rigorous analysis of setpoint tracking and disturbance rejection properties of the closed-loop system are given in the presence of both model mismatches and external disturbances. The proposed scheme is applied to control the temperature of a simplified jacketed stirred tank heater (JSTH). Simulation results demonstrate that the proposed method possesses a better disturbance rejection performance than those of the MDOB-PI, MPC and PI methods in controlling such dead-time processes.

A speed control for a PMSM using finite-time feedback control and disturbance compensation

The speed-regulation problem for a permanent-magnet synchronous motor (PMSM) servo system is studied in this paper. In order to improve the disturbance rejection property of the PMSM, a novel composite controller for the speed-loop is presented. First, an extended state observer (ESO) is introduced to estimate the disturbances of the system. The estimated value is used in the feed-forward compensation design. Second, a continuous feedback-based finite-time control technique is employed for the feedback design. The composite speed controller can be considered as a composition of finite-time proportional feedback plus feed-forward compensation based on ESO (FTP + ESO). Two standard proportional—integral (PI) controllers are employed for two current loops. The closed-loop system of the speed error can be regarded as a first-order finite-time control system with bounded disturbances. Rigorous analysis shows that the proposed scheme can enhance the disturbance rejection property of the closed-loop system. Simulation and experimental comparisons with two other control methods, ie the composite control method with proportional feedback plus feed-forward compensation based on ESO (P + ESO), and the PI control method, are given to verify the effectiveness of the proposed method.

Practical Controller Design of Hybrid Experimental System for Seismic Tests

A hybrid experimental system is one of the powerful tools to perform various seismic tests for unknown and/or huge structures, where an actuator-excited experimental vibratory system and a computational response analysis are simultaneously combined and implemented. This paper presents a control methodology for high-performance hybrid experimental systems. A 2-DOF control framework is applied from the viewpoint of control techniques, where a feedback compensator is designed according to the system stabilization analysis, and a feedforward (FF) compensator is designed to achieve the desired servo characteristics. In the FF compensator design, an iterative learning control approach is particularly adopted to eliminate the response delays in the hydraulic actuator. The proposed compensation algorithm has been verified using a laboratory hybrid experimental set up with two-mass structure as a load mechanism.