Kozo Ide

Sensorless drive of surface-mounted permanent-magnet motor by high-frequency signal injection based on magnetic saliency

This paper presents a new sensorless control scheme of a surface-mounted permanent-magnet (SMPM) motor using high-frequency voltage signal injection method based on the high-frequency impedance difference. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This makes the magnetic saliency in the motor. This magnetic saliency has the information about the rotor position. The high-frequency voltage signal is injected into the motor in order to detect the magnetic saliency and estimate the rotor position. In this paper, the relationship between the high-frequency voltages and high-frequency currents is developed using the voltage equations at the high frequency, and the high-frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor in the low-speed region including zero speed, even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.

Analysis of permanent-magnet machine for sensorless control based on high-frequency signal injection

This paper presents the analysis of a surface-mounted permanent-magnet (SMPM) machine for the sensorless control scheme based on the high-frequency fluctuating voltage signal injection method. A simplified high-frequency model of an SMPM machine in the estimated rotor reference frame is developed and a sensorless rotor position and speed estimation algorithm is described. To support this, the high-frequency impedances of an SMPM machine are analyzed by finite-element analysis (FEA) and compared with measurement results using a pulsewidth-modulation (PWM) inverter system under various injection conditions. The results of the FEA and measurements are coincident with each other with some errors due to the nonlinear behavior of the PWM inverter and the SMPM machine. The analysis results give physical insights into selecting the injection conditions for sensorless operation of the SMPM machine even though adjustments considering nonlinear behaviors of PWM inverters are required in the actual operation for the desired performance. The experimental results of speed and position control using a commercial SMPM machine are presented based on the analysis of the SMPM machine for the sensorless control algorithm.

Sensorless rotor position estimation of an interior permanent-magnet motor from initial states

This paper describes a torque, speed, or position control method at standstill and low speed in the interior permanent-magnet motor (IPMM) drive system without any rotational transducer. While IPMMs have originally magnetic saliency, it varies according to the load conditions and the control performance can be easily degraded. In this paper, the saliency or impedance difference is used as the conventional methods and, nevertheless, in order to amplify the difference containing the information of the rotor angle and to maintain a reasonable performance under any load condition a high-frequency injection scheme is proposed. A speed and position estimation scheme based on the characteristics of the high-frequency impedance is proposed. The scheme extracts the high-frequency impedance components related to the rotor position. An initial angle estimation scheme for starting from an arbitrary rotor position is also proposed. It can distinguish the north magnetic pole position from the south one in several decade milliseconds. The proposed scheme enables position control of a transducerless or position-sensorless IPMM. The experimental results clarify the satisfactory operation of the proposed position control algorithm under any load condition.

High-Bandwidth Sensorless Algorithm for AC Machines Based on Square-Wave-Type Voltage Injection

This paper describes a new control algorithm which can enhance the dynamics of a sensorless control system and gives a precise sensorless control performance. When high frequency injection methods with conventional manners (sinusoidal voltage injection) are used, Low Pass Filters (LPFs) should be used to get an error signal. However, these LPFs degrade sensorless control performances due to the time delay of LPFs themselves. To avoid this effect, the proposed method uses square wave type voltage injection instead of the sinusoidal type voltage injection. As the result, the error signal can be calculated without any delay, and the position estimation performance can be enhanced. This paper contains the voltage injection method and corresponding signal processing method. Using the proposed method, the performance of sensorless control can be enhanced remarkably. The bandwidth of current controller was enhanced up to 250 Hz and that of speed controller was up to 50 Hz.

Maximum Torque per Ampere (MTPA) Control of an IPM Machine Based on Signal Injection Considering Inductance Saturation

The aim of this study was to develop a new method to operate an interior permanent magnet synchronous machine (IPMSM) on the maximum torque per ampere (MTPA) condition. The characteristics of the MTPA condition were analyzed and the MTPA condition was derived based on the input electric power. The proposed method injects a small current signal used for tracking the MTPA operating point along with the fundamental current for torque generation. This method does not require any machine parameters or premade lookup table. The frequency of the injected signal is several hundred hertz, and the performance of the MTPA tracking is almost free from load torque disturbance. The feasibility of the proposed method was verified under various operating conditions with computer simulation and testing with an 11 kW IPMSM drive system.

Analysis of permanent magnet machine for sensorless control based on high frequency signal injection

This paper presents the analysis of the surface mounted permanent magnet (SMPM) machine for the sensorless control algorithm using the high frequency fluctuating voltage signal injection method. A simplified high frequency model of a SMPM machine in the estimated rotor reference frame is developed. Then, the impedances of a SMPM machine at high frequency are analyzed by finite element analysis (FEA) and is compared with impedance measurements using a pulse width modulation (PWM) inverter system under various injection conditions. The results of the FEA and high frequency impedance measurements are coincident with each other, and give physical insights in sensorless operation of the SMPM machine. The experimental results of speed control and position control using a commercial SMPM machine are presented based on the analysis of the SMPM machine for the sensorless control algorithm.

High bandwidth sensorless algorithm for AC machines based on square-wave type voltage injection

This paper describes a new control algorithm which can enhance the dynamics of a sensorless control system and gives a precise sensorless control performance. When high frequency injection methods with conventional manners (sinusoidal voltage injection) are used, Low Pass Filters (LPFs) should be used to get an error signal. However, these LPFs degrade sensorless control performances due to the time delay of LPFs themselves. To avoid this effect, the proposed method uses square wave type voltage injection instead of the sinusoidal type voltage injection. As the result, the error signal can be calculated without any delay, and the position estimation performance can be enhanced. This paper contains the voltage injection method and corresponding signal processing method. Using the proposed method, the performance of sensorless control can be enhanced remarkably. The bandwidth of current controller was enhanced up to 250 Hz and that of speed controller was up to 50 Hz.

Sensorless position control and initial position estimation of an interior permanent magnet motor

This paper describes a torque, speed or position control method at the stand still and low speed in the interior permanent magnet (IPM) motor drive system without any rotational transducer. While IPM motors originally have magnetic saliency, it varies according to the load conditions and the control performance can be easily degraded. In this paper the saliency or impedance difference is used as the conventional methods and, nevertheless, in order to amplify the difference containing the information of the rotor angle and to maintain a reasonable performance under any load condition, a high frequency injection scheme is proposed. A speed and position estimation scheme based on the characteristics of the high frequency impedance is proposed. The scheme extracts the high frequency impedance components related to the rotor position. An initial angle estimation scheme for the starting from an arbitrary rotor position is also proposed. It can distinguish the north magnetic pole position from the south one in several tens of milliseconds. The proposed scheme enables position control of a transducerless or position-sensorless IPM motor. The experimental results clarify the satisfactory operation of the proposed position control algorithm under any load condition.

Sensorless drive of SMPM motor by high frequency signal injection

This paper represents a new sensorless control scheme of surface mounted permanent magnet (SMPM) motors. To estimate the rotor position of the SMPM motor, a high frequency voltage signal is injected and the resultant injected frequency current signal is used. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This saturation effect makes some magnetic saliency of the SMPM motor. In this paper, to estimate the rotor position using this magnetic saliency, the high frequency model of the SMPM motor is developed and the high frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor at low and zero speed operation even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.

Encoderless Servo Drive With Adequately Designed IPMSM for Pulse-Voltage-Injection-Based Position Detection

This paper presents a technology fusion of encoderless control technique and encoderless-specialized motor applied for servo drive applications. First, a fast encoderless control technique which employs a high-frequency pulsating signal injection method with square-wave pulse voltage at d -axis is proposed. The estimation principle is almost the same as that of a resolver, and the control technique includes a fast initial position estimation algorithm based on magnetic hysteresis phenomenon. Next, a prototype interior permanent-magnet synchronous motor is designed to act like a resolver. Then, evaluation results of the prototype encoderless drive system are reported. Finally, the prototype system is confirmed to fulfill major servo specifications of about 10-b net resolution of the position detection at standstill and more than 60-Hz speed control bandwidth in operation speed from 0 up to 1000 min-1 . In conclusion, the proposed encoderless drive system is verified to achieve major control performances almost comparable to those of encoder-assisted servo drive systems.