Optimal Servo Research Articles

An Adaptive Two Degree of Freedom Controller

A two-degree of freedom generic optimal controller structure and regulator design method is shown, which can be easily optimized in H2 - and H∞-norm space. It is shown how the regulator and some additional filters - depending on the reference signal, the output disturbance and the invariant process factors - should be selected by the solutions of Diophantine equations if optimality is important. It is proved that the optimal regulator of the generic scheme optimized in H2-norm space is the theoretical regulator providing minimal controller variance to the process and noise model variations. Based on the above special structure an adaptive dual control strategy is shown, designing the optimal filters for the optimal servo and regulatory paradigms of the controller.

Optimal control system for hot strip finishing mill

This paper describes how to control the strip gauge, looper angle, and strip tension for a hot strip finishing mill, and gives the results of a real application. This is based on optimal servo theory and the model decoupling method. In the finishing mill process, there exists a mutual interaction among the strip gauge, the looper angle, and the strip tension. Conventionally, each of them is controlled independently. To improve the control performance, multivariable control that considers this interaction is applied to the whole productions process. The new control system is also used for the tension control of the automatic width control.

An Inverse-LQ Approach to Design of Optimal Servo System with Frequency Weights

This paper presents a design method of optimal servo systems with frequency weights from the view point of the inverse LQ problem. This design method allows us to assign desirable closed-loop transfer functions directly and in addition, to obtain the desired optimal control law in a closed form in terms of design parameters and the system parameters. A numerical example is also shown to illustrate the design method proposed here as well as to show its usefulness.

Design of Optimal Servo Systems Based on Fuzzy Models for an Omnidirectional Mobile Robot.

In this article we propose a design method of an optimal servo fuzzy system for an omnidir- ectional mobile robot. For the robot, it is considered that the nonlinearity of the dynamic system is mainly dominated by the rotational angle of the robot between the moving and absolute coordinate systems. In order to build the model-based fuzzy servo system, we first choose some representative rotational angles to simplify the nonlinear model to multiple linear models. Then, optimal type-1 and type-2 servo controllers are derived for the rotational control of the mobile robot. The servo gain matrices associated with the controllers are found by using the linear fuzzy models. Finally, we present the results of simulations and show how to use our method to control the omnidirectional mobile robot.

Single-Input Single-Output Optimal Deadbeat Servo Systems Induced from Fixed-Endpoint Optimal Servo System. For Strictly Proper Systems.

This paper deals with the design of a deadbeat servo system for a single-input, single-output linear digital system. The optimal deadbeat servo system with the output feedback in the z-domain is induced from the fixed endpoint optimal servo system in the time-domain. This servo system has a finite-time settling property (deadbeat property) and a ripple-free property, and the transient responses are improved over those of the minimum-time deadbeat control. Furthermore, by using the two-degrees-of-freedom configuration, more robust parameterizations are provided for the optimal deadbeat servo system.

Design of Dynamic Positioning System for Self-propulsive Barge under External Disturbances

When a ship is required to keep the specified position with high accuracy under influence of external disturbances, dynamic positioning system (DPS) is often used in order to keep its position. It will be able to construct a control system which has no interaction among the controlled variables by using the inverse linear quadratic (ILQ) optimal servo theory. It will be also able to express the optimal feedback gain in terms of the system matrices and the design parameters. In ILQ optimal servo theory, time constant Ti as the design parameters have much influence on the performance of the control system, and the suitable values of Ti should be selected as small as possible corresponding to external disturbances. However, it is troublesome to select suitable Ti because we have to carry out numerical simulations repeatedly.In this paper, we applied the ILQ optimal servo theory to design the control system of DPS for a selfpropulsive barge. About time constant Ti, we designed the system with Ti defined automatically in response to the dimensions of controlled variables. Applying this method, it is possible to adjust the suitable values of Ti automatically. From the numerical simulations, it is found that design process taking the system with Ti defined automatically would be more useful and easier than taking usual ILQ optimal servo theory.

Optimal Control System for Hot Strip Finishing Mill

This paper describes how to control strip gauge, looper angle, and strip tension for a hot strip finishing mill and the application result. This is based on the optimal servo theory and the model dccoupling method. In finishing mill process, there exists mutual interaction among strip gauge, Iooper angle, and strip tension. Conventionally, each of them is controlled independently. To improve the control perfonnance, the multivariable control considering this interaction is applied to all productions. The new control system is also used for the tension control of the automatic width control.

A Note on Polynomial ILQ Design Method and Two-Degree-of-Freedom Optimal Servo Systems

This paper studies relationships between the polynomial ILQ design method for robust servo systems and two-degree-of-freedom optimal servo systems. It turns out that the former method uses the same state feedback as the latter one, but attains a specified response by letting another tuning parameter large enough. The paper also shows that, because of model matching specification, the polynomial ILQ method needs some additional consideration for guaranteeing optimality. Numerical simulation is carried out to illustrate the results.

A Study on Unified Automatic Control System for Longitudinal Motion of Jetfoil Based on Optimal Servo Theory

Current Jetfoil control has been made by platform and contour mode selection and by manual input of fore-foil depth according to sea conditions by human operator, which cause overload and may be difficult for operators. This requires the further automation in the control system.In this paper, authors propose unified automatic control system (ACS) which is based on optimal servo theory and eliminates human operation in ACS. The reference input signal in the servo system was modified to the sea conditions to achieve unification of platforming and contouring. First, optimal servo system (OSS) was designed to keep the fore and aft foil depths in waves to find that the sole OSS was still sluggish. Therefore, authors added proportional and differential element in inner feedback loop in addition to the modification of reference input.The MOSS+MRI, which represents modified optimal servo system (MOSS) and modification of reference input (MRI), was confirmed the good control performance in the wide range of waves through simulation.

最適有限整定サーボ系・レギュレータの一設計法

最適有限整定サーボ系・レギュレータの一設計法

Optimal Control System for Hot Strip Finishing Mill

This paper describes how to control strip gauge, looper angle, and strip tension for a hot strip finishing mill and the application result. This is based on the optimal servo theory and the model decoupling method. In finishing mill process, there exists mutual interaction among strip gauge, looper angle, and strip tension. Conventionally, each of them is controlled independently. To improve the control performance, the multivariate control considering this interaction is applied to all productions.

A general frequency dependent digital optimal preview servo system

In this paper, we present a design method for a kind of general frequency dependent digital optimal preview servo system which is effective to improve frequency characteristics of closed loop system. By the method, for any rational expression frequency dependent weight which loads on error vector, we can design an optimal preview servo system. The result is applied to an air slide linear motor in simulation and its effectivity is proved.

参照入力を一般化したILQ最適サーボ系設計法

参照入力を一般化したILQ最適サーボ系設計法

Improved discrete proximate time optimal controller of a disk drive actuator

An important relationship between the acceleration discount factor and the closed loop control poles in a discrete Proximate Time Optimal Servo (PTOS) design has been established. This result enables the PTOS seek and tracking controllers to be designed and optimized independently without being constrained by boundary conditions. During subsequent merging, smooth transition from seek to tracking is obtained by linear, time shrinking of the boundary layer closer to the target track. The proposed controller is applied to R/W head actuation in a hard disk. Significant improvement in head settling is observed compared to conventional PTOS, specifically for longer seeks.

A robust neurocontroller incorporating a priori knowledge of plant dynamics

This paper presents a nonlinear controller design method that integrates linear optimal control techniques and nonlinear neural networks. The multilayered neural networks (MNN's) are incorporated into a model-based linear optimal controller (LOR) to add nonlinear effects on the LOR. The proposed controller can tolerate a wider range of uncertainties than the LOR alone, because the MNN can compensate nonlinear system uncertainties that are not considered in the LOR design. The control performance is improved by using a priori knowledge of the plant dynamics as the system equation and the corresponding LOR. Using the similar technique, a nonlinear servo controller is designed by combining the MNN-based controller and the linear optimal servo controller. Computer simulations are performed to show the applicability and the limitation of the new nonlinear controllers.

Modeling and Control of Transfer of a Cylindrical Liquid Container along a Curved Path.

This paper presents the modeling and control of transfer of a cylindrical liquid container along a curved path. Sloshing of (1, 1)-mode in the container is represented by a mechanical model using a spherical pendulum or a dual pendulum composed of two simple pendulums. An optimal control method for the liquid container transfer is determined through simulations and experiments using an optimal servo control system with a Kalman filter. Using this method, the optimal transfer control of the liquid container is obtained for practical performance specifications. The optimal control gain along a curved path has been obtained and is different from the control gain along a straight path. The usefulness of the present work has been demonstrated through the control simulation and laboratory control experiments.

Robust locally optimal servo control systems

Robust locally optimal servo control systems

Motion Control of Unconstrained Underwater Robot Considering Gravity and Buoyancy.

Ocean development has been advanced for a long time in order to obtain ocean resources and energy, but its working environment is very severe for human beings, so underwater working robots which can be used instead of human beings have came into demand. This paper deals with attitude control of the main body of an unconstrained underwater robot using a movable counterweight controlled by the optimal servo system and trajectory control of a manipulator using disturbance compensation control(DCC). From the result obtained by computer simulations, it was made clear that the attitude of the main body can be controlled without steady-state error by means of controlling the position of the counterweight using the optimal servo system. In addition trajectory control of the manipulator can be carried out by using DCC which regards the reaction force due to the movement of the counterweight as a disturbance.

A Design Method of Weighting for Optimal Servo System

In a previous paper, we proposed a design method, based on the optimal regulator theory for type-1 digital servo systems. The method can cope, with parameter uncertainties and time-continued disturbance to guarantee steady-state robustness of servo systems. However, when this method is applied to actual systems, elements of the weighting matrix have to be repeatedly adjusted in a trial and error fashion, until the given performance-index of the transient process is satisfied. In this paper, we propose, a design algorithm for the weighting matrix, which consists of the following two steps.(1) Express quantitatively the qualitative adjusting-knowledge of the designer by using fuzzy sets and estimate roughly the initial value of the weighting matrix with the fuzzy reasoning method.(2) Compute precisely the optimal elements in the weighting matrix by using the simplex method.By means of these steps, the automation of servo system design is accomplished. Finally, velocity control of a DC motor is taken as an example to show the effectiveness of the method proposed in this paper.

LQ Design of Feedforward Elements in Two-Degree-of-Freedom Optimal Servo Controllers

LQ Design of Feedforward Elements in Two-Degree-of-Freedom Optimal Servo Controllers