Manabu Kosaka

Anti-Windup Using Switch for SISO System

In this paper, we propose a new anti-windup method with a clear procedure of initialization to avoid vibrations and overshoots in spite of saturation of the control input. This method is based on a single-input single-output 2 degree of freedom model matching control system and by using a switch, a saturated control input and an output are respectively used for updating a reference output and a feedforward input instead of a control input and a reference output; these are not affected by input saturation. By this means, even if the control input is saturated, the state of the reference model corresponds with that of the control object and at the moment the updated control input is not saturated, the output immediately corresponds with the reference output. Furthermore, a procedure to initialize the reference model by which vibrations and overshoots do not occur even if the control input is saturated, is given. This method is suitable for systems in which vibrations and overshoots are taboo, such as tool machines. The effectiveness of the proposed method is verified by numerical simulation.

Sensorless IPMSM Drive with EKF Estimation of Speed and Rotor Position

In this paper, a new sensorless Interior Permanent Magnet Synchronous Motor (IPMSM) drive method with Extended Kalman Filtering (EKF) estimation of speed and rotor position is proposed. This method is on the basis of the sensorless Surface Permanent Magnet Synchronous Motor (SPMSM) drive [1] that can be applied to motors with no salient pole and is developed so as to be able to be applied to motors with salient pole such as IPMSM. Noise and vibration in mechanical plant becomes larger if rotor position estimation error occurs. Furthermore, the rotor position estimation error causes noise and vibration. The feature of the method is that rotor position estimation error does not occur even if motor current or motor voltage change. Therefore, the method can be applied with arbitrary motor voltage waveform and, consequently, the method is suitable for sensorless IPMSM drive. Numerical simulations are illustrated to verify the effect of the method.

Parameters Identification for Interior Permanent Magnet Synchronous Motor Driven by Sensorless Control

In this paper, a new parameter identification method for Interior Permanent Magnet Synchronous Motor (IPMSM) sensorless control is proposed. Noise and vibration in mechanical plant is increased if rotor position estimation error occurs. Furthermore, the rotor position estimation error causes noise and vibration. When load torque and reference motor speed are constant, and phase voltages and phase currents in multiple stationary states are measured, motor parameters can be identified even if an estimated rotor position does not correspond with the actual rotor position. Furthermore, this paper proposes a new sensorless control method that derives the position by solving the motor voltage equation. It is shown that the method is able to estimate the true position even if the motor is in acceleration. Numerical simulations with the implementation of a Pulse Width Modulation (PWM) inverter are illustrated to verify the effect of the methods.

Dynamic System Identification using a Step Input

In this paper, we propose a deterministic off-line identification method performed by using input and output data with a constant steady state output response such as a step response that causes noise or vibration from a mechanical system at the moment when it is applied but they are attenuated asymptotically. The method can directly acquire any order of reduced model without knowing the real order of a plant, in such a way that the intermediate parameters are uniquely determined so as to be orthogonal with respect to 0 ∼ N-tuple integral values of output error and irrelevant to the unmodelled dynamics. From the intermediate parameters, the coefficients of a rational transfer function are calculated. In consequence, the method can be executed for any plant without knowing or estimating its order at the beginning. The effectiveness of the method is illustrated by numerical simulations and also by applying it to a 2-mass system.

Anti-Windup Feedforward Controller Design for Reference Input Expressed as a Time Polynomial

In this paper, we propose an anti-windup method for feedforward controller of 2 degree of freedom (2DOF) control by which model matching is done. The proposed method replaces memorized variable of output of reference model in the feedforward controller with controlled variable when input is saturated. It is verified by numerical simulations that satisfactory reference input response is derived by the proposed method even if input is saturated or controlled object has uncertainty.

An identification method with direct acquisition of reduced order model from a steplike response

In this paper, we propose a deterministic off-line identification method performed by using input and output data with a constant steady-state output response. The method can directly acquire any order of reduced model without knowing the real order of a plant, in such a way that the intermediate parameters are uniquely determined so as to be orthogonal with respect to O-N-tuple integral values of output error and irrelevant to the unmodeled dynamics. From the intermediate parameters, the co-efficients of a rational transfer function are calculated. In consequence, the method can be executed for any linear single-input single-output plant without knowing or estimating its order at the beginning. The effectiveness of the method is illustrated by numerical simulations and also by applying it to a two-mass system.

A Study on a Controller to Suppress Periodic Speed Variation

This paper is concerned with a practical controller to suppress the periodic speed variation of a motor. Speed variation in a pump, a compressor or a wheel of an electric vehicle causes vibration and noise, which shorten the life of the machine. Although repetitive control can suppress the speed variation, there are the following problems: If a reference velocity changes, the period of the speed variation changes and the effect of the suppression is reduced. The tuning parameters are difficult to tune. In the case where a low-resolution angle sensor is used, the output of the controller to suppress the speed variation becomes pulse-shaped and causes harmonic ripples that increase energy consumption. In order to eliminate the harmonic ripples, we propose a controller of which the output is interpolated with a sine wave.

Generalised Disturbance Observer for Systems with Harmonic Disturbances and Input Saturation Using the Internal Model Principle

It is known that some rotational machines such as compressors, pumps and so on often generate noises and vibrations due to periodic disturbances synchronised with the rotational speed. Vibration suppressing systems such as repetitive control are known to be effective to suppress the periodic disturbances. However, the control input of the repetitive controller may become larger and larger when the control input is saturated. This paper designs a generalised disturbance observer using the internal model principle that is effective to suppress periodic disturbances, and proposes a method that can make control performance deterioration minimal even if the control inputs are saturated. First, the proposed system estimates disturbances using the disturbance observer. Next, the estimated disturbances are passed into a filter of which the gain is one and phase lag is zero at the disturbances frequencies, and are added into the control input in order to cancel the periodic disturbance. This filter is designed using the internal model principle, and the reason is explained why the filter should not be set to one. Some motor system simulations show that the phase lag of the estimated disturbances correspond to that of the periodic disturbances so that the method can make control performance deterioration minimal. The method is appropriate to rotational machine systems such as compressors and pumps in which the vibrations and noises should be avoided.

Vibration Suppression Control against Periodic Disturbances for Systems with Input Saturation

Compressors, pumps etc often generate noise and vibration due to periodic disturbances. It is known that vibration suppressing systems such as repetitive control are effective in suppressing periodic disturbances. However, there is no report about methods that can make control performance deterioration as small as possible when the control inputs of the vibration suppression system are saturated. This paper develops a disturbance observer that is effectively suppressing periodic disturbances, and proposes a method that can make control performance deterioration minimal even if the control inputs are saturated. First, the proposed system estimates disturbances using the disturbance observer. Next the estimated disturbances are passed into a filter of unity gain and zero phase change at the disturbances frequencies, and are added into the control input in order to cancel the periodic disturbance. Some motor system simulations show that the phase of the estimated disturbances corresponds to that of the periodic disturbances so that the method can make control performance deterioration minimal. The method is appropriate to rotational machine systems such as compressors and pumps in which vibration and noise should be avoided.

ANTI-WINDUP FOR A TWO-DEGREE-OF-FREEDOM MODEL MATCHING CONTROL SYSTEM

In this paper, we propose a new anti-windup method with an initialization procedure that avoids overshoot in spite of saturation of control input. This method is based on a two-degree-of-freedom model matching (MM) control system. Instead of the control input and reference output, which are not affected by input saturation, the saturated control input and an output are used respectively for updating the reference output and feedforward input. Thereby, when the input becomes unsaturated, MM works well because the memorized values of the reference output that are used for updating the reference output correspond with the past output values. Furthermore, a procedure to initialize the reference model making the overshoots small is presented, even if the given control input is saturated. This method is adequate for systems in which overshoots are prohibited, such as temperature controls and machine tools. The effectiveness of the proposed method was verified using numerical simulations and experiments.