Showing papers on "PID controller published in 1989"

Process Dynamics and Control

Abstract: PART ONE: INTRODUCTORY CONCEPTS.1. Introduction to Process Control.2. Theoretical Models of Chemical Processes.PART TWO: DYNAMIC BEHAVIOR OF PROCESSES.3. Laplace Transforms.4. Transfer Function and State-Space Models.5. Dynamic Behavior of First-Order and Second-Order Processes.6. Dynamic Response Characteristics of More Complicated Processes.7. Development of Empirical Models from Process Data.PART THREE: FEEDBACK AND FEEDFORWARD CONTROL.8. Feedback Controllers.9. Control System Instrumentation.10. Overview of Control System Design.11. Dynamic Behavior and Stability of Closed-Loop Control Systems.12. PID Controller Design, Tuning, and Troubleshooting.13. Frequency Response Analysis.14. Control System Design Based on Frequency Response Analysis.15. Feedforward and Radio Control.PART FOUR: ADVANCED PROCESS CONTROL.16. Enhanced Single-Loop Control Strategies.17. Digital Sampling, Filtering, and Control.18. Multiloop and Multivariable Control.19. Real-Time Optimization.20. Model Predictive Control.21. Process Monitoring.22. Batch Process Control.23. Introduction to Plantwide Control.24. Plantwide Control System Design .Appendix A: Digital Process Control Systems: Hardware and Software.Appendix B: Review of Thermodynamics Concepts for Conservation Equations.Appendix C: Use of MATLAB in Process Control.Appendix D: Contour Mapping and the Principle of the Argument.Appendix E: Dynamic Models and Parameters Used for Plantwide Control Chapters.

Decentralized adaptive control of manipulators: theory, simulation, and experimentation

Abstract: The author presents a simple decentralized adaptive control scheme for multijoint robot manipulators based on the independent joint control concept. The control objective is to achieve accurate tracking of desired joint trajectories. The proposed control scheme does not use the complex manipulator dynamic model, and each joint is controlled simply by a PID (proportional-integral-derivative) feedback controller and a position-velocity-acceleration feedforward controller, both with adjustable gains. Simulation results are given for a two-link direct-drive manipulator under adaptive independent joint control. The results illustrate trajectory tracking under coupled dynamics and varying payload. The proposed scheme is implemented on a MicroVAX II computer for motion control of the three major joints of a PUMA 560 arm. Experimental results are presented to demonstrate that trajectory tracking is achieved despite coupled nonlinear joint dynamics. >

Controllers of Ziegler-Nichols type for unstable process with time delay

Abstract: Proportional (P), proportional plus integral (PI) and proportional plus integral plus derivative (PID) controllers are designed for a time-delayed process having latency L and a single right half-plane pole at s=λ, with λL < 1 Explicit designs are derived from the concept of phase margin, and an optimum stability approach for PI controllers is based on a parameter plane study An optimum gain margin design is also given for P control

Method and apparatus of automatically setting PID constants

Abstract: PID control method and PID controller for determining, from a control response from a process, characteristic values representative of controllability and automatically deriving and setting PID constants from the determined characteristic values. The error between a set point and a controlled value is decided as to whether to be due to a change in set point or due to a disturbance, and PID constants are set on the basis of results of decision.

Toward intelligent control

Abstract: The problem of automatic tuning of simple regulators is examined. The key idea is to design an aid for the process operator, which should use minimal prior information about the system. This is a typical example of a case where it is essential to develop techniques that will give crude but robust estimates. The development has resulted in a novel generation of the classical PID (proportional, integral, and derivative) controller. An application of relay autotuning to temperature control of a distillation column is considered as an example. Adaptive control is then treated. The adaptive algorithms can be viewed as local gradient methods. They require prior information but, given the information, can give very good control performance. The use of an expert system to integrate the two approaches is then discussed. >

Modelling and Self-Tuning Control of a Multivariable pH Neutralization Process Part I: Modelling and Multiloop Control

Abstract: This paper describes the design, modelling and control of a multivariable pH neutralization process. The experimental facility consists of two stirred tank reactors with an acid-base neutralization taking place in each tank. The process has been designed as a demonstration unit for the evaluation of advanced Control strategies such as adaptive and multivariable control. The neutralization process has four controlled variables, pH and liquid level in each of the two tanks. This strong acid, strong base neutralization poses a difficult multivariable problem because each manipulated variable has a significant effect on each controlled output. This process is also highly nonlinear and time varying due to the inherent nonlinearity associated with pH control and the shifts in the titration curve that occur when the amount of buffering agent changes in an unpredictable fashion. A physical model of the neutralization process has been developed which is in good agreement with experimental step response data over a wide range of experimental conditions. A multiloop control system consisting of four PID controllers was tedious to tune and had difficult coping with changes in the amount of buffering. In a companion paper (Hall and Seborg, 1989), self-tuning control resulted in improved control especially when only the process gain was estimated on-line, assuming that the dynamics were not changing significantly.

A Predictive PI Controller for Processes with Long Dead Time

Abstract: This paper describes a predictive PI controller with dead-time compensation. The advantage of the new controller compared with other dead time compensating controllers is that it contains only three adjustable parameters; the gain, the integral time and the dead time. The controller is also suited for processes with varying dead times.

Optimal PID Gain Schedule for Hydrogenerators-Design and Application

Abstract: The development and testing of a digital gain switching governor for hydrogenerators are described Optimal gains are found at different load points by minimizing a quadratic performance criterion prior to controller operation During operation, the gain sets are switched in depending on gate position and speed error magnitude It is shown that, with gain switching operating, the digital governor has a substantial reduction of noise on the command signal and up to 42% faster responses to power requests Nonlinear control strategies enable the digital governor to have a 25% to 2% reduction in speed overshoot on start-ups and an 8% to 1% reduction in undershoot on load rejections as compared to the analog >

On‐line PID controller tuning from a single, closed‐loop test

Abstract: Calcul modifie des parametres d'un procede modele a grand temps retard afin d'ameliorer les performances du regulateur

Complementary rules to Ziegler and Nichols' rules for a regulating and tracking controller

Abstract: Traditionally, PID controllers are designed either as regulating or as tracking controllers because, usually, it is not possible to fulfil both functions simultaneously. Designing rules complementary to Ziegler and Nichols ones are introduced. They allow, using a special connection of the classical PID, the tracking behaviour to be improved without modifying the regulating characteristics.

Optimal PID gain schedule for hydrogenerators

Abstract: This paper describes the development and testing of a digital gain switching governor for hydrogenerators. Optimal gains were found at different load points by minimizing a quadratic performance criterion prior to controller operating. During operation, the gain sets are switched in depending on the gate position and speed error magnitude. With gain switching operating, the digital governor was shown to have a substantial reduction of noise on the command signal and up to 42% faster responses to power requests. Non-linear control strategies enabled the digital governor to have a 2.5% to 2% reduction in speed overshoot on startups, and an 8% to 1% reduction in undershoot on load rejections as compared to the analog.

Replacing a PID controller by a lat-lead compensator for a robot-a frequency-response approach

Abstract: Because of their simplicity, PD (Proportional-derivative) or PID (proportional-integral-derivative) controllers are widely used with various robot control strategies. For dynamic control of robots, this algorithm can be shown to lead to unsatisfactory tradeoffs between static accuracy, system stability, and insensitivity to disturbances. These tradeoffs become more serious as the sampling rate decreases. By deriving a more realistic discrete-time system model and using frequency-response analysis, a lag-lead compensator is designed and implemented. Both theoretical analysis and real tests are given for the comparisons of the PD or PID controller and the lag-lead compensator. Replacing PD or PID controllers by lag-lead compensators results in a small increase of offline design and tuning effort and online computational load, but the improvements in robot performance are significant. >

Knowledge-based control approach for robotic manipulators

Abstract: The integration of hard algorithmic control and soft knowledge-based control is addressed, in the specific context of robotic manipulator control. In particular, a hierarchical control structure having a high-speed hard controller at the lowest level and an intelligent observer and an intelligent tuner at the upper levels, is discussed. The rationale for a specific control structure is explored, and the necessary qualitative and analytical foundation for the control structure is presented. To demonstrate the development and feasibility of this control structure, an example application has been programmed on a SUN workstation. A two degree-of-freedom robot was simulated (a C program) as a separate UNIX process. The intelligent observer was developed using an available AI toolkit. The top-level intelligent tuner was developed from a valid set of linguistic tuning rules for proportional-integral-derivative (PID) servos, using fuzzy system concepts, and implemented as a set of decision tables. The control str...

A robust self-tuning predictive controller for HVAC applications

Abstract: A robust form of self-tuning controller than has been designed to replace conventional PID controllers in a number of HVAC applications is described. The controller is based on a version of the generalized predictive control algorithm that uses default values for most of its parameters and requires selection of only one commissioning parameter: the control sampling interval. Special jacketing software has been developed to implement a set of expert rules, which are not application dependent, but which supervise the operation of the on-line parameter estimator and the calculation of control action. This ensures satisfactory operation of the controller in most situations. The performance of the controller is evaluated under demanding conditions using a detailed computer simulation of the central air handler in a building.

On controller tuning for a flexible‐link manipulator with varying payload

Abstract: In this article experimental results are presented for system identification and control of a single-link flexible manipulator carrying an unknown, varying payload. The control objective is to maintain endpoint position accuracy in the presence of flexure effects after rapid movement due to a rigid body slew-angle commanded position. Various time-domain parameter estimation techniques are used to identify ARMA model representations to be employed in controller tuning schemes for vibration compensation. Only endpoint acceleration measurements and motor shaft angle measurements are utilized in relatively simple PID control schemes, which are tuned as dictated by a varying, unknown payload.

Design, implementation, and testing of an adaptable optimal controller for an electric wheelchair

Abstract: The design, implementation, and testing of an adaptable optimal controller for an electric wheelchair are presented. Optimal control theory and pattern recognition techniques are combined to produce the design of a controller using a modified proportional, integral, and derivative (PID) control method. The controller is adaptable in the sense that multiple sets of control coefficients are used with each set being optimized for a specific range of wheelchair load parameters. The appropriate set of control coefficients may be automatically selected based on load parameter estimates to provide a self-adaptive controller, or manually selected prior to installation to tailor the chair to a particular user. The manually adaptable controller is implemented in a microprocessor-based system. The experimental results obtained from installing and testing the system on an electric wheelchair are presented and discussed. >

Real time adaptive control for resistance spot welding process

Abstract: This real time adaptive control and method of controlling a spot welding process compensates for electrode wear, oxidized surfaces, fit up variations and machine variations. Workpiece thermal growth is the measurement discriminant and the welding machine heat command is the control input. The control utilizes a least squares estimator to monitor the process and workpiece displacement, a precompensator to shape a desired displacement trajectory command, and a model reference control with a Smith-predictor to compensate for time delays and a proportional-integral-derivative compensator. The model reference control has a mathematical model of the spot welding process and calculates an estimated displacement using a predicated process gain and bias calculated by the estimator. The estimated displacement is compared to the precompensator displacement trajectory and an error is generated which regulates the heat command through the PID compensator.

Robotic force control for deburring using an active end effector

Abstract: An active force control system for robotic deburring based on an active end effector is developed. The system utilizes a PUMA-560 six axis robot. The robot's structural dynamics, positioning errors, and the deburring cutting process are examined in detail. Based on ARMAX plant models identified using the least squares method, a discrete PID controller is designed and tested in real-time. The control system is shown to maintain the force within l N of the reference, and reduce chamfer depth errors to 0.12 mm from the 1 mm possible without closed-loop control.

Design of robot control systems

Abstract: An expository discussion on practical aspects of the design problems of robot control systems is presented. The first section discusses the present status of robot control methodology based on the so-called 'teaching and playback' control scheme. It is pointed out that PTP (point to point) control is still central in practice because only a sort of pulse-incremental servo controller is implemented for each joint actuator in actual industrial robots. The second section points out that servo controllers of this kind perform approximately as a PD or PID controller, and demonstrates that such PD and PID control schemes can work well even if the robot dynamics are non-linear and have strong couplings between the joint variables. The third section deals with path-tracking and trajectory-tracking control problems when teaching by human operators is not possible. This is then followed by a final but substantial section on recent results on learning control and adaptive control. An example of learning control for ...

Variable Structure and Time-Varying Parameter Control for Hydroelectric Generating Unit

Abstract: Conventional governor control for hydro-turbines is linear PI or PID with constant parameters. Thus, one set of constant PID parameters is used for different cases. In fact, the hydro-turbine governing system has variable structure and parameters. Therefore, fixed control structure and parameters are not the most suitable for various plant structures and a control with variable structure and parameters is more appropriate. An intelligent self-improving control strategy with both variable structure and parameters is developed. The controller is multistructural and parameter variable. The selection of control structure and the optimization and adjustment of control parameters are directed by a processing unit. This unit bases its action on the information received from another block that tracks the system operating conditions in real-time, and detects and identifies the plant structure and parameters.

Dynamics and control of quasirational systems

Abstract: Systems having transfer functions of the form where P1(s), P2(s) and Q(s) are polynomials, are called quasirational distributed systems (QRDS). They are encountered in processes modeled by hyperbolic partial differential equations. QRDS can have an infinity of right half-plane zeros which causes large phase lags and can result in poor performance of the closed-loop system with PID controllers. Theory on the asymptotic location of zeros of quasipolynomials is used to predict the nonminimum phase characteristics of QRDS and formulas are presented for factoring QRDS models into minimum and non-minimum phase elements. A generalized Smith predictor controller design procedure for QRDS, based on this factorization, is derived. It uses pole placement to obtain a controller parameterization that introduces free poles which are selected to satisfy robustness specifications. The use of pole placement allows for the design of robust control systems in a transparent manner. Controller selection is generally better, simpler and more direct with this procedure than searching for optimal PID controller settings.

Adaptive on‐line optimizing control of bioreactor systems

Abstract: Several on-line optimizing control strategies were proposed and tested by computer simulation for the efficient operation of bioreactors. The control task was divided into two, one of which was to search for the optimal operating point and passed the set point to the lower layer of which task was to make the process output follow the set point as soon as possible. It was shown to be effective for the upper layer to express the objective function as a polynomial with respect to the measurement variable and to make use of it for finding the optimum point. Noting that the major dynamic characteristics of bioreactor system is the time-varying and nonlinear nature, the adaptive type control system is in evitable. It was shown to be quite effective to use discrete type self-tuning PID controller and the optimal controller compensated for the interaction between the control loops. Application was made to the cell recycle system for the production of lactic acid and baker's yeast cultivation. I was found from the former application that the control quality can be significantly improved by incorporating the decoupling strategy into the lower layer closed-loop system. It was also found from the latter application that the initial startup period can be significantly reduced by making use of the rough mathematical model.