scholarly journals Use of Discrete-Time Forecast Modeling to Enhance Feedback Control and Physically Unrealizable Feedforward Control with Applications

2021 ◽  
Author(s):  
Derrick K. Rollins
Keyword(s):  
Feedback Control ◽  
Discrete Time ◽  
Feedforward Control ◽  
Control Strategies ◽  
Control Variable ◽  
Smith Predictor ◽  
Modeling Approach ◽  
Feedback Error ◽  
Feedforward Controller ◽  
Forecast Modeling

When the manipulated variable (MV) has significantly large time delay in changing the control variable (CV), use of the currently measured CV in the feedback error can result in very deficient feedback control (FBC). However, control strategies that use forecast modeling to estimate future CV values and use them in the feedback error have the potential to control as well as a feedback controller with no MV deadtime using the measured value of CV. This work evaluates and compares FBC algorithms using discrete-time forecast modeling when MV has a large deadtime. When a feedforward control (FFC) law results in a physically unrealizable (PU) controller, the common approach is to use approximations to obtain a physically realizable feedforward controller. Using a discrete-time forecast modeling method, this work demonstrates an effective approach for PU FFC. The Smith Predictor is a popular control strategy when CV has measurement deadtime but not MV deadtime. The work demonstrates equivalency of this discrete-time forecast modeling approach to the Smith Predictor FBC approach. Thus, this work demonstrates effectiveness of the discrete-time forecast modeling approach for FBC with MV or DV deadtime and PU FFC.

Use of vent stack temperature as a feedforward variable for dissolver total titratable alkali (TTA) control

TAPPI Journal ◽  
2018 ◽  
Vol 17 (05) ◽  
pp. 261-269
Author(s):  
Wei Ren ◽  
Brennan Dubord ◽  
Jason Johnson ◽  
Bruce Allison
Keyword(s):  
Feedback Control ◽  
Current Practice ◽  
Feedforward Control ◽  
Control Variable ◽  
Indirect Measurement ◽  
Tight Control ◽  
Transfer Lines ◽  
Green Liquor ◽  
Process Dynamics ◽  
Downstream Processes

Tight control of raw green liquor total titratable alkali (TTA) may be considered an important first step towards improving the overall economic performance of the causticizing process. Dissolving tank control is made difficult by the fact that the unknown smelt flow is highly variable and subject to runoff. High TTA variability negatively impacts operational costs through increased scaling in the dissolver and transfer lines, increased deadload in the liquor cycle, under- and over-liming, increased energy consumption, and increased maintenance. Current practice is to use feedback control to regulate the TTA to a target value through manipulation of weak wash flow while simultaneously keeping dissolver density within acceptable limits. Unfortunately, the amount of variability reduction that can be achieved by feedback control alone is fundamentally limited by the process dynamics. One way to improve upon the situation would be to measure the smelt flow and use it as a feedforward control variable. Direct measurement of smelt flow is not yet possible. The use of an indirect measurement, the dissolver vent stack temperature, is investigated in this paper as a surrogate feedforward variable for dissolving tank TTA control. Mill trials indicate that significant variability reduction in the raw green liquor TTA is possible and that the control improvements carry through to the downstream processes.

scholarly journals Research on multidimensional evaluation of tracking control strategies for self-driving vehicles

2020 ◽  
Vol 12 (3) ◽  
pp. 168781402091296 ◽  
Author(s):  
Yuan-yuan Ren ◽  
Jie Wang ◽  
Xue-lian Zheng ◽  
Qi-chao Zhao ◽  
Jia-lei Ma ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Feedback Control ◽  
Control Strategy ◽  
Tracking Control ◽  
Evaluation System ◽  
Feedforward Control ◽  
Control Strategies ◽  
Dynamic Feedback ◽  
Multidimensional Evaluation ◽  
Control Dynamic

Performance evaluation is a necessary stage in development of tracking control strategy of autonomous vehicle system, which determines the scope of application and promotes further improvement. At present, most of the tracking control strategies include performance evaluation. However, performance evaluation criteria differ from work to work, lacking comprehensive evaluation system. This article proposes a multidimensional integrated tracking control evaluation system based on subjective and objective weighting, taking into account the tracking accuracy, driving stability, and ride comfort. Through the co-simulation of CarSim and Simulink, qualitative analysis and quantitative analysis based on multidimensional evaluation system of five coupled longitudinal and lateral control strategies (lateral: pure pursuit feedforward control, dynamic-model-based optimal curvature control (dynamic feedforward control), Stanley feedback control, kinematics feedback control, and dynamic feedback control; longitudinal: the incremental proportion–integration–differentiation control) under typical operating conditions are carried out to analyze the operating range and robustness of each tracking control strategy. The results show that the Stanley tracking control strategy and the dynamic feedback tracking control strategy have a wide range of applications and robustness. The consistency of qualitative analysis results and the quantitative analysis results verify the validity and feasibility of the evaluation system.

Feedforward Control of Solar Thermal Power Plants

1997 ◽  
Vol 119 (1) ◽  
pp. 52-60 ◽  
Author(s):  
A. Meaburn ◽  
F. M. Hughes
Keyword(s):  
Feedback Control ◽  
Solar Collector ◽  
Power Plants ◽  
Feedforward Control ◽  
Thermal Power ◽  
Control Loop ◽  
Parabolic Trough ◽  
Solar Thermal Power ◽  
Control Schemes ◽  
Feedforward Controller

In recent years the problem of controlling the temperature of oil leaving an array of parabolic trough collectors has received much attention. The control schemes developed have in general utilized a feedback control loop combined with feedforward compensation. The majority of the published papers place the emphasis almost entirely on the design of the feedback control loop. Little or no attention has been paid to issues involved in the design of the feedforward controller. This paper seeks to redress this imbalance by concentrating upon the design and development of a feedforward controller for the ACUREX distributed solar collector field at the Plataforma Solar de Almeria. Different methods of combining feedback and feedforward will be assessed and experimental results will be presented in order to support any theoretical observations made.

ON FEEDBACK CONTROL OF CHAOTIC NONLINEAR DYNAMIC SYSTEMS

1992 ◽  
Vol 02 (02) ◽  
pp. 407-411 ◽  
Author(s):  
GUANRONG CHEN ◽  
XIAONING DONG
Keyword(s):  
Feedback Control ◽  
Computer Simulations ◽  
Discrete Time ◽  
Dynamic Systems ◽  
Chaotic Dynamic ◽  
Control Strategies ◽  
Equilibrium Points ◽  
Nonlinear Dynamic Systems ◽  
Feedback Controls ◽  
Feedback Controllers

In this paper, some interesting analysis and simulations on the control of chaotic dynamic systems using conventional feedback control strategies are presented. The typical discrete-time chaotic Lozi system is investigated in some detail. The trajectories of the chaotic Lozi system are controlled to its equilibrium points using conventional feedback controls. Analysis on the design of the feedback controllers and its computer simulations are included.

Multi-Rate Feedforward Tracking Control for Plants With Nonminimum Phase Discrete Time Models

1999 ◽  
Vol 123 (3) ◽  
pp. 556-560 ◽  
Author(s):  
Yuping Gu ◽  
Masayoshi Tomizuka
Keyword(s):  
Discrete Time ◽  
Tracking Control ◽  
Performance Enhancement ◽  
Feedforward Control ◽  
Phase Error ◽  
Sampling Rate ◽  
Time Model ◽  
Rate System ◽  
Control Scheme ◽  
Feedforward Controller

This paper is concerned with performance enhancement of tracking control systems by multi-rate control. The feedback controller is updated at the same rate as the sampling rate of the output measurements. The feedforward controller processes the desired output signal for high accuracy tracking, and its output is updated at a rate N-times faster than the sampling rate of the output measurements. The discrete time model of the controlled plant may possess unstable zeros, and the zero phase error tracking controller (ZPETC) is used as a feedforward controller. Inter-sample behavior of the plant is included in evaluating the tracking performance of the multi-rate system. Illustrative examples are given to show advantages of the proposed multi-rate feedback/feedforward control scheme.

Minimization of Degradation Through Prognosis Based Control for a Damaged Aircraft Actuator

2009 ◽  
Author(s):  
Vishal Mahulkar ◽  
Douglas E. Adams ◽  
Mark Derriso
Keyword(s):  
Degradation Rate ◽  
Feedforward Control ◽  
Control Strategies ◽  
Minimum Loss ◽  
Aircraft Systems ◽  
Systems Model ◽  
Point Tracking ◽  
Feedforward Controller ◽  
Actuator Degradation ◽  
Control Surfaces

In this paper we present a formulation of an aircraft systems model for prognosis-based control. An aircraft systems model with hydraulic actuators for control surfaces is developed in SIMULINK and is connected with a model for predicting degradation of an actuator. An LQR based feedback control is employed to compensate for changes in the plant dynamics and a feedforward controller is used to achieve better performance through set-point tracking, while taking into account the current actuator degradation rate. The advantage of the combination of feedback and feedforward control strategies is then demonstrated through reduction of degradation of the actuator while achieving a minimum loss of performance using constrained optimization.

Nonlinear Feedforward-Feedback Control of an Electric Clutch Actuator

2014 ◽  
Vol 1014 ◽  
pp. 339-343 ◽  
Author(s):  
Xin Li ◽  
Hui Zhou ◽  
Hao Li ◽  
Xue Song Li
Keyword(s):  
Feedback Control ◽  
Feedforward Control ◽  
Experimental Tests ◽  
Linear Feedback ◽  
Original Form ◽  
Model Errors ◽  
Nonlinear Characteristics ◽  
Control Scheme ◽  
Control Requirement ◽  
Feedforward Controller

For a novel electric clutch actuator, a nonlinear feedforward-feedback control scheme is proposed to improve the performance of the position tracking control. The feedforward control is designed based on flatness in consideration of the system nonlinearities, and the linear feedback control is given to accommodate the model errors and the disturbances. Lookup tables, which are used to represent nonlinear characteristics of the actuator systems, such as friction force, appear in their original form in the designed feedforward controller. The designed controller is evaluated through simulations and experimental tests, which show that the proposed controller satisfied the control requirement. Comparison with PID control is given as well.

scholarly journals Fuzzy PID Feedback Control of Piezoelectric Actuator with Feedforward Compensation

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Ziqiang Chi ◽  
Minping Jia ◽  
Qingsong Xu
Keyword(s):  
Feedback Control ◽  
Piezoelectric Actuator ◽  
Pid Control ◽  
Feedforward Control ◽  
Comparative Investigation ◽  
Preisach Model ◽  
Fuzzy Pid ◽  
Fuzzy Pid Control ◽  
Control Scheme ◽  
Feedforward Controller

Piezoelectric actuator is widely used in the field of micro/nanopositioning. However, piezoelectric hysteresis introduces nonlinearity to the system, which is the major obstacle to achieve a precise positioning. In this paper, the Preisach model is employed to describe the hysteresis characteristic of piezoelectric actuator and an inverse Preisach model is developed to construct a feedforward controller. Considering that the analytical expression of inverse Preisach model is difficult to derive and not suitable for practical application, a digital inverse model is established based on the input and output data of a piezoelectric actuator. Moreover, to mitigate the compensation error of the feedforward control, a feedback control scheme is implemented using different types of control algorithms in terms of PID control, fuzzy control, and fuzzy PID control. Extensive simulation studies are carried out using the three kinds of control systems. Comparative investigation reveals that the fuzzy PID control system with feedforward compensation is capable of providing quicker response and better control accuracy than the other two ones. It provides a promising way of precision control for piezoelectric actuator.

Sign in / Sign up

Export Citation Format

Share Document