Phase-lead Compensator Research Articles

A new phase-lead design method using the root locus diagrams

A new phase-lead design method using the root locus diagrams is proposed. In the traditional phase-lead root locus design procedure, the designer has no direct control to the steady-state error constant of the resulting closed-loop system. In order to obtain a satisfactory steady-state error constant, the designer has to try different locations of the compensator's zero and the desired dominant roots. However, the procedure does not indicate to the designer how to alter the locations to obtain the desired steady-state error constant. With the new method presented in this note, the applicability of the phase lead compensation network is determined once the desired dominant roots are given, and the maximum steady-state error constant can be directly determined. If the desired steady-state error constant rely within the limit, the desired steady-state error constant together with the desired dominant roots are directly used to obtain the compensator. If the desired stead-state error constant exceeds the reachable limit, the note proposes a way to find out the proper locations of the desired dominant roots.

QUASIPASSIVITY-BASED ROBUST NONLINEAR FLAP POSITIONING CONTROL USING SHAPE MEMORY ALLOY MICRO-ACTUATORS

This paper proposes a quasipassivity-based robust nonlinear control law ensuring position control of a rotary flap by means of an antagonist-type shape memory alloy microactuator. The control system employs variable-structure control to obtain robust performance, phase-lead compensation to quasipassivate the shape memory alloy dynamics and quasipassivity-based analysis to warrant robust ultimate boundedness of system trajectories. The feedback connection of the two paths leads to ultimate boundedness of tracking error trajectories of the plant despite uncertainties in the dynamic loads affecting the leading edge flap and in the friction found in the actuator. Since accurate numerical simulations and development of new concepts of microactuators based on shape memory alloys require a tractable, constitutive law accurately describing the relationship between force, displacement and temperature in the material, the paper also presents a hybrid micro-macro-mechanical shape memory alloy constitutive model. This model is based on a combination of structural modeling on a microscopic scale and transformation kinetics modeling on a macroscopic scale. The proposed control law and hybrid micro-macro-mechanical model are placed in closed-loop by means of numerical simulations that demonstrate the validity of the nonlinear control scheme.

Self-tuning regulators for combustion oscillations

Self–excited combustion oscillations arise from a coupling between unsteady combustion and acoustic waves, and can cause structural damage to many combustion systems. Active control provides a way of extending the system's stable operating range by interrupting the damaging thermoacoustic interaction. The active controller considered injects some fuel unsteadily into the burning region, thereby altering the heat–release rate, in response to an input signal detecting the oscillation. Although the feasibility of such a control configuration was demonstrated on laboratory–scale experiments over 15 years ago, the triple requirement for full–scale applications is to adapt the controller response to varying operating conditions and to guarantee that the controller will cause no harm, while relying as little as possible on a particular combustion model. As a first step towards meeting these requirements, a self–tuning regulator (STR) is proposed in this paper for a class of combustion systems that satisfy some fairly non–restrictive assumptions. An open–loop transfer function from the controller output voltage driving the actuator to the pressure signal detecting the oscillation is derived, and is shown to be the product of a time delay τ tot and a transfer function that satisfies certain structural properties. Using the open–loop transfer function, it is shown that the stabilizing STR structure is that of a simple phase–lead compensator if τ tot=0, and the same compensator combined with a Smith controller if τ tot=0. The adaptive rule for the adjustment of the STR parameters is derived from a Lyapunov stability analysis. Promising results are obtained on a simulation based on a nonlinear premixed flame model and on an experimental set–up which consists of a laminar flame burning in a Rijke tube.

Active-Passive Hybrid Vibration Control of Beam by Self-Sensing Piezoelectric Actuator. The Optimal Resistance and Velocity Feedback.

The active-passive hybrid electrical circuit with piezoelectric elements was investigated to suppress the vibration of beam. In order to apply passive vibration control and actie vibration control on the beam simultaneously, the concurrent sensing and actuating piezoelectric elements were used. For the passive control, the optimal resistance was used which have the advantage of stable, fail-safe, without power requirement. For active control, the velocity feedback control was used. Based on the hybrid control method, the passive control circuit and the active control circuit can be combined on the same control circuit. Due to the optimal resistance in the hybrid control circuit, the system must have the phase lag. To improve the system performance, a phase-lead compensator was employed. This paper demonstrated theoretically and experimentally that the hybrid control has the advantages of both passive and active control systems.

Precision positioning using a microfabricated electrostatic actuator

This paper presents a microfabricated actuator designed for high precision servo-positioning in a magnetic hard disk drive. The device is actuated using electrostatic force generated with parallel-plate capacitive electrodes. The displacement of these electrodes is measured using a dedicated capacitive sensing interface, allowing closed-loop control to be used to extend the servo bandwidth. Using the sensing electronics and a simple phase-lead compensator, a prototype device was used to actuate a 1.6 mg ceramic slider over a 1.2 kHz bandwidth. Using optical position measurements, the same actuator was used to achieve a 2.5 kHz bandwidth.

Absolute stability conditions in a fuzzy phase-lead compensation and their extension to MIMO systems

This paper presents absolute stability conditions in a fuzzy phase-lead compensation and their extension to multi-input-multi-output (MIMO) systems. A theorem which realizes an effective phase-lead compensation is recalled. A so-called matrix is derived in the theorem. A fuzzy phase-lead compensator (FPLC) is constructed by using the transformation matrix. The circle condition is employed to derive absolute stability conditions of feedback systems in a fuzzy phase-lead compensation. Next, a generalized class of FPLCs is defined, and its stability conditions are derived from the viewpoints of H/sub /spl infin// norm and quadratic stability. It is found that the stability conditions realize stability analysis not only for single-input-single-output (SISO) systems, but also for MIMO systems.

FEEDBACK STRUCTURE-BORNE SOUND CONTROL OF A FLEXIBLE PLATE WITH AN ELECTROMAGNETIC ACTUATOR: THE PHASE LAG PROBLEM

In this paper an experimental study is presented on active control of a clamped plate at audio frequencies by using feedback controller and electromagnetic actuator. The controller is designed with modern control theory on a lumped parameter model of the plate, and is then implemented in experiments to control the real structure. In practice, the optimal control force cannot be generated exactly as desired due to the non-ideal characteristics of the control system. Several factors such as A/D and D/A convertors, velocity estimation through approximate differentiation, and the electromagnetic actuator are examined in respect to their frequency features. An analytical model is developed to predict the phase lag of the actual control force to the designed control force. It is shown that if the phase lag is over 90 degrees, the control system will become unstable. Two techniques are discussed for improving the system performance that is mainly affected by the electromagnetic actuator when the high speed sampling and processing device is used as the controller. The simple and practical method is to employ a phase-lead compensation network in the control circuit. Another one that is more fundamental is to incorporate the characteristics of the actuator into the system by feeding back the current passing through the actuator into the controller. Various experiments are carried out to verify the analysis and the proposed methods, and the potentials of the electromagnetic actuator in controlling the high frequency vibration and noise are therefore demonstrated.

Software for Comparative Studies of Phase Lead Compensator Design

Abstract The paper describes a new software package developed for designing phase lead/lag controllers for a given system. The package has been developed in the MATLAB environment with a powerful graphical user interface. It incorporates several phase lead/lag controller design methods based on the frequency domain technique some of which require a computational approach for a system of any complexity. Considerable education benefit can be obtained from studying the different design approaches which can be compared using loop frequency and closed loop step response plots. Two examples are given to demonstrate this.

Adaptive control strategies for a precision machine tools axis

This paper evaluates two different kinds of adaptive controllers in the context of robust control of a precision machine tool axis. These include an adaptive proportional-integrative-derivative controller and an adaptive phase-lead compensator. The latter is modified further to account for the effects of input saturation, and the resulting performance is studied. A proportional-integrative-derivative controller is also included for comparison purposes. The experimental results obtained confirm the overall performance superiority of adaptive controllers with respect to both transient and steady-state responses. In addition, the adaptive phase-lead controller is shown to be significantly more robust with respect to various changes in system parameters and trajectory shapes.

Frequency shaping for fuzzy control systems with unknown non-linear plants by a learning method of neural network

This paper deals with a frequency shaping, which means an improvement of frequency response, for fuzzy control systems with unknown non-linear plants by a learning method of neural network. We derive an important theorem, which is related to phase-lead compensation, by introducing concept of frequency characteristics such as gain crossover frequency and phase margin. Using the theorem, a fuzzy phase-lead compensator, which have parameters for effectively compensating phase characteristics of control systems, is constructed. After proposing a design procedure of the fuzzy phase-lead compensator for linear plants, we extend it to a design procedure for unknown non-linear plants. A frequency shaping for unknown non-linear plants is realized by Widrow-Hoff learning rule which is a basic learning algorithm of neural networks. Simulation results show the effect of frequency shaping by Widrow-Hoff learning rule.

A fast-response microthermocouple

A fast-response chromel-alumel (and chromel-constantan) microthermocouple is described and its dynamic characteristics are measured. The microthermocouple features a microdisk junction 0.08 mm in diameter and 2.5 μm thick. Its time constant in turbulent flow of liquid Refrigerant-113 (a poor heat conductor) is measured to be ∼4.6 ms. This time constant was reduced to ∼3.4 ms with a phase-lead compensation circuit. It was possible to distinguish between vapor and liquid phase temperatures in turbulent subcooled boiling flow of Refrigerant-113 with the compensated microthermocouple.

Applications of Routh-Hurwitz criterion to evaluation of phase margin and phase lead compensation

A method, based on a transformation G(s) = ½[aG(s) + G(s)−1], is proposed for applying the Routh-Hurwitz criterion to determine the phase margin of a linear time-invariant feedback control system, and to design phase-lead compensation. A numerical example is also given to illustrate the method.

Phase lead compensator design

A non-iterative, frequency response based method is described for the design of phase lead compensators for feed-back control loops. It is particularly suited to loops having variable gain, variable phase frequency response characteristics in the frequency range of interest and has been found to yield near-optimal values for the compensator parameters in such cases. The method is illustrated by means of an example.

Design of an optical servosystem using a structural optimizing method considering controllability. (2nd report. The structural optimization of an optical pick-up model using the pole-zero cancellation method).

The optical servosystem requires a high degree of controllability. However, it is very difficult to realize a servosystem with higher controllability since the dynamic characteristics of an optical pick-up influence the stability of the servosystem. Therefore, both a control system and a structural system must be considered simultaneously in the design stage of the optical servosystem. The purpose of this paper is to determine the structural system in order to obtain higher controllability. Firstly, the authors investigate the structural characteristics of an optical pick-up model and explain the necessity of structural optimization to improve servo characteristics. Secondly, the structure of the optical pick-up model is optimized by using the Pole-Zero Cancellation Method proposed by the authors. The servosystem is comprised of the optical pick-up model with the phase-lead compensator. Finally, the characteristics of the servosystem are investigated and the improvements are confirmed. The practicability of this design method is verified by the experiments.

Design of an optical servosystem using a structural optimizing method considering controllability. (3rd report. An application of the pole-zero cancellation method to development of optical pick-up).

The design method of an optical servosystem and its practicability were discussed in the first and second reports. In this paper, the authors develop a practical optical pick-up. Firstly, we propose a new type of optical pick-up which is a simple monobloc hinge-type structure and investigate its structural characteristics. As a result, it is confirmed that the structural characteristics of the optical pick-up influence the stability of the servosystem; accordingly, a structural optimization is necessary to obtain a high degree of controllability. Secondly, the optical pick-up is optimized by using the Pole-Zero Cancellation Method and the servosystem is comprised of the optimal pick-up with the phase-lead compensator. The results of both analytical and experimental investigations verify that the servo characteristics are improved and sufficient characteristics are satisfied such that the servo specifications are realized

Design of a Magnetic Levitation Control System???An Undergraduate Project

A magnetic levitation control system is built as a classroom demonstration device for systems and control courses. System linearization and phase-lead compensation techniques are used to control the unstable nonlinear system.

Phase Lead Compensation Using the Smith Chart

This paper presents a new technique for designing series phase lead compensation using the Smith chart. The method avoids the trial and error procedures of design methods based on the root-locus plot or the Bode diagram.

Decoupling Control of Secondary Flux and Secondary Current in Induction Motor Drive with Controlled Voltage Source and Its Comparison with Volts/Hertz Control

A concept of decoupling control in the strategy of the speed regulation of the squirrel cage induction motor with controlled voltage source is represented. The decoupling control intends to cancel out the cross terms between the secondary flux and the secondary current. Three necessary and sufficient conditions for the decoupling control are offered that correspond to taking into account the effect of the primary impedance in the control strategy. Phase lead compensation with the slip frequency control allows the realization of the decoupling control, which is found to be an extension of both the conventional vector control and the constant volts/hertz control. Numerical and experimental results are also shown.

Simulation of adaptive modification of the vestibulo-ocular reflex with an adaptive filter model of the cerebellum.

An adaptive linear filter model of the cerebellum (Fujita, 1982), which functions as a phase lead or lag compensator with learning capability, is applied to a problem of the cerebellar control of the vestibuloocular reflex (VOR). Under the assumption that the cerebellar flocculus accounts for adaptive modification of dynamic characteristics of the VOR, the cerebellar model was incorporated into a linear control model of the oculomotor system. The results of a simulation study are in good agreement with experimental data on eye movement.

The Development of the Pneumatic Transmission Lag Compensator and its Effects

In order to minimize the transmission lags associated with the pneumatic instrumentation, the Transmission Lag Compensator (TLC) was developed. The construction and features of the TLC which is based on the phase lead compensation are described. The effects of applying the TLCs are investigated by experiments and simulations. Experiments with practical plants using the TLCs show the improvement of the control performance over the system without the TLC. The effects of applying the TLCs are also obtained quantitatively from the control performance simulations.