Integral Controller Gain Research Articles

Precision-limit positioning of direct drive systems with the existence of friction

This paper discusses the issue of precision-limit positioning of a direct drive system with the existence of friction. By precision-limit positioning it means that, in addition to the common sense of sub-micro, nano, or pico precision, the precision error equals the sensor resolution. This means a zero-count precision error when a digital type position sensor is used in the feedback loop. Precision-limit positioning also enforces 100% repeatability as precision is concerned. Of course, this is the limit of the precision that a real control system can achieve. In the past, this kind of performance was not considered possible mainly for lacking accurate and enough information about friction, especially the static friction. However, as more and more knowledge of the pre-sliding motion has been revealed, it is shown in this research that it is possible to achieve such kind of performance. It also shows that, from the dynamic point of view, to achieve precision limit an integral type control should be included in the final stage of positioning. A simple and explicit criterion is given for the integral control gain to guarantee asymptotic stability. Some practical issues of a digital precision-limit positioning system are also addressed.

Robust discrete adaptive input-output-based sliding mode controller

A robust input-output-based discrete adaptive sliding mode controller is proposed. It combines an integral action, a nonlinear output feedback, an adjustable sliding mode and an adaptive plant parameter estimator. The controller design is carried out via the Lyapunov direct method. A pole assignment procedure is developed for determination of the integral control gain and the coefficients of the sliding mode hyperplane. An on-line update for coefficients of the hyperplane is used to improve control loop behaviour further. Compared with the optimally tuned proportional-integral-derivative (PID) controller, the new controller has increased robustness with regard to the variation in the main process parameters and it has much better set point tracking characteristics. The new controller also exhibits very good disturbance rejection property comparable work or better than to that obtained by the optimally tuned PID controller. Simulation experiments are made to illustrate the quality and robustness of control achieved.

Microprocessor-based modified discrete integral variable-structure control for UPS

This paper presents a digital signal processor microprocessor-based high-performance uninterruptible power system (UPS). It also modifies the integral variable-structure control (IVSC) approach to be more suitable for the UPS, which is tracking a sinusoidal AC voltage with specified frequency and amplitude. Since the implementation of the control laws has tended to the digital microprocessor, the paper extends the modified IVSC to the discrete time domain. Procedures are developed for determining the control function, the switching plane and the integral control gain, so that the system has desired properties. Simulation and experimental results show that the proposed scheme can supply a high-quality voltage power source in the presence of load disturbance and parameter variation.

Automatic Voltage Regulator Design by Modified Discrete Integral Variable Structure Model Following Control

In power systems, the automatic voltage regulator (AVR) is designed to make the terminal voltage to accurately track the deviation of the reference voltage. To achieve the desired requirements, this paper proposes the modified discrete integral variable structure model following control (MDIVSMFC) approach. The MDIVSMFC approach comprises a reference model part for specifying the design requirements and a MDIVSC part for minimizing the errors between the plant and model. The non-ideal sliding motion is introduced to take the place of the ideal sliding motion in discrete-time systems. Its existence conditions are used to adapt the proposed approach to the discrete systems. The application of MDIVSMFC to an AVR design is developed. Procedures for determining the control function, the coefficients of the sliding surface and the integral control gain are also proposed in detail. Simulation results are compared with the IEEE type-I voltage regulator to demonstrate that the proposed scheme can achieve fast and robust responses.

Interconnected operation of small-hydroelectric and diesel power systems

The paper deals with some aspects of the interconnected operation of small-hydroelectric and diesel power systems provided with classical controllers. A comprehensive procedure for optimizing the integral controller gain setting using an integral squared error (ISE) technique is suggested. Analysis reveals that the integral-derivative (ID) controller in the small-hydroelectric area and integral controller in the diesel area improves the system performance significantly as compared to that of integral control in both areas. Analysis also reveals that the continuous frequency and tie-power oscillations can completely be eliminated using an ID controller in the small-hydroelectric area. © 1998 John Wiley & Sons, Ltd.

DSP-based integral variable structure model following control for brushless DC motor drivers

The design and implementation of digital signal processor (DSP) microprocessor-based brushless DC motor servo control drivers are presented. The integral variable structure model following control (IVSMFC) approach is presented to achieve robust accurate servo tracking. A design procedure is developed for determining the control function, the coefficients of the switching plane, and the integral control gain such that the error between the state of the model and the controlled plant is to be minimized. Simulation and experimental results show that the proposed approach can achieve accurate velocity/position servo tracking in the presence of load disturbance and plant parameter variations.

Design of discrete integral variable structure control systems and application to a brushless DC motor control

A discrete integral variable structure control (DIVSC) approach is presented to achieve accurate servo-tracking in the presence of load disturbance and plant parameter variations. Conditions are derived to ensure the existence of non-ideal sliding motion. This scheme also proves that the describing motion in the non-ideal sliding region will be close to the ideal sliding motion. Further, procedures are proposed for determining the control function, the coefficients of the switching plane and the integral control gain. The procedures can cause the resultant system to have the desired properties. A microcomputer-based brushless DC motor servo position control system using the DIVSC approach is illustrated. Simulation results are compared with the PI controller to demonstrate the potential of the controller. Experimental results present the practical capability of the proposed controller.

Discrete integral variable structure model following control for induction motor drivers

A DSP microprocessor based high performance vector-controlled induction motor driver is presented. The discrete-time integral variable structure model following the control (DIVSMFC) approach is proposed for the outer loop of the driven system. A design procedure is developed for determining the control function, the switching plane and the integral control gain such that the error between the state of the model and the controlled plant is minimised. Simulation and experimental results show that the proposed scheme can achieve accurate position/velocity servo-tracking in the presence of load disturbances and plant parameter variations.

Applications of self-tuning control on industrial CNC machines

Most successful applications of parameter adaptive control to obtain constant cutting forces in machining processes have been limited to laboratory environments. This paper presents a methodology for realizing efficient adaptive control algoritms in industrial CNC machines. Experimental results concerning the fixed gain integral control and variable gain MRAC show that the present set-up in a heavy-duty CNC machining center leads to predictable control behavior. Furthermore, two effective algorithms—a deadbeat self-tuning control with increased order and a PID-type self-tuning control based on the pole-placement method—are implemented to obtain more effective cutting control performance. In this study, repeatable and satisfactory experimental results show that the technique developed here for real manufacturing processes is feasible.

Feasible Control for Optimum Power Generation in a Small Power System

A pitch controller is developed for a wind turbine in a small wind-diesel power system. The proposed controller regulates wind converted power to meet the constraints of system frequency and power limit of wind turbine. Static model of wind turbine and diesel governor response are used to determine the desired power command and the respective pitch command is derived by variable gain integral control so that the error between actual and desired power is minimized. Small wind-diesel power system of Koshikijima island in Japan is considered for model studies and the effectiveness of the proposed controller is proved by computer simulation based on actual data of wind speed.

Integral variable structure control approach for robot manipulators

An integral variable structure control (IVSC) approach for robot manipulators is presented to achieve accurate servo-tracking in the presence of load variations, parameter variations and nonlinear dynamic interactions. A procedure is proposed for choosing the control function so that it guarantees the existence of the sliding mode and for determining the coefficients of the switching plane and the integral control gain such that the IVSC approach has the desired properties. Furthermore, a modified proper continuous function is introduced to overcome the chattering problem. The proposed IVSC approach has been simulated for the first three links of a PUMA 560 robot arm as an illustration. The simulation results demonstrate the potential of the proposed scheme.

Design of integral variable structure controller and application to electrohydraulic velocity servosystems

An integral variable structure controller (IVSC) for robust servotracking is proposed. It comprises an integral controller, which is designed for achieving zero steady-state error under step input, and a variable structure controller (VSC) which is designed for enhancing robustness. A procedure is developed for determining the coefficients of the switching plane and the integral control gain such that the overall closed-loop system has the desired eigenvalues. Furthermore, a modifed proper continuous function is introduced to overcome the chattering problem. An electrohydraulic velocity servocontrol system using the proposed IVSC approach is illustrated. Simulation results show that the proposed IVSC approach can achieve accurate servotracking and is fairly robust to plant parameter variations and external load disturbances.

Current controller design for an electromagnetic actuator using an online parameter optimization approach

The design is presented of a digital proportional-plus-integral current controller for a nonlinear electromagnetic actuator using an online parameter optimization approach. The minimization algorithm of J.A. Nelder and R. Mead (1965) is used to calculate the proportional and integral controller gain such that a design objective function is minimized. At each iteration of the minimization procedure, the objective function is calculated by sampling the actual current and voltage signals of the actuator. >

Stability Analysis of Thyristor Current Controllers

The operational stability areas of proportional-integral (PI) controllers implemented in analogue, analogue with discrete sampling, and digital form have been theoretically investigated. Whereas in the continuous-data control system, stability may be-maintained by compensating any increase of proportional gain K <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</L> with integral gain, K <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</L> , the discretized system tends to become unstable if either K <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</L> or K <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</L> is increased. A new stability area is shown to exist for a discrete-sampled system with puire integral control and large gain (which is unstable when implemented in analogue form). This result is confirmed experimentally.