Low-resolution Position Sensor Research Articles

Multi-Agent Position Estimation in Modular Motor Drives Using Low-Resolution Sensors

Because a modular motor drive is composed of multiple identical pole drive units and controllers, it can be considered as a multi-agent system. This makes modular motor drives particularly interesting during faults, when the remaining healthy agents assure the continuity of operation. Nevertheless, for some crucial information such as the rotor position, these drives still rely on a single sensor which introduces a single point of failure. In this work, this single high-resolution position sensor is replaced by multiple binary, low-resolution position sensors. A vector tracking observer algorithm, implemented in the different controllers, processes this low-resolution sensor data into a position estimate. Subsequently, these position estimates of the different agents are exchanged with other agents using a distributed averaging algorithm. For this latter approach, it is shown in this work that it improves the position estimation under healthy conditions as well as during agent malfunctions. The concept is demonstrated on a modular axial-flux permanent magnet synchronous machine with fifteen pole drive units, each equipped with a low-resolution position sensor, that are assigned to five agents.

Fault Tolerant and Nano Displacement Drive Control Method of Photoelectric Motor for Battery Electric Vehicle

The low-resolution photoelectric position sensor is used, that is, Hall position sensor replaces the traditional photoelectric encoder and other high-resolution position sensors to monitor the rotor position. However, because the three-phase Hall position sensor can only output six position signals, a hardware circuit design of low-resolution position sensor monitoring rotor position signal is proposed. Meanwhile, nanotechnology has been introduced in the study of micro drive of battery electric vehicle (BEV). BEV driver has some disadvantages such as hysteresis, creep and nonlinearity, which seriously affects its application in nano environment. A nano displacement sensor is designed for the characteristics of BEV driver. The nonlinear problem of micro driver is solved through the closed-loop control of position feedback. In the test, through the verification of rotor position and current waveform, it can be proved that the method based on photoelectric position sensor and rotor position signal monitoring can ensure the low deviation of rotor position calculation and correct output signal of three-phase photoelectric position sensor. The decoupling performance of vector control is verified by 3/2 transformation. In the displacement detection of micro driver, the designed nano displacement sensor has higher resolution and its performance is better than that of the previous three generations of displacement sensors.

A New Position and Speed Estimation Scheme for Position Control of PMSM Drives Using Low-Resolution Position Sensors

A new position control method for permanent magnet synchronous motor (PMSM) drive with a low-resolution encoder is proposed in this paper. Three binary Hall position sensors are utilized to realize a moderate-performance position control system for the consideration of economy and simplicity in servo application. Compared with sensorless control, the usage of binary Hall position sensors is a guarantee of both control performance and low cost. However, the low resolution of the Hall sensor will heavily deteriorate the accuracy of the position and speed calculation. Such drawback can be effectively minimized by using appropriate position and speed estimation schemes. With the help of polynomial fitting and state observer techniques, a solution is provided to realize semi-closed loop control by treating the position and speed estimators as separate systems. The performance can be improved (1) by proposing a polynomial fitting scheme with least squares method, high-resolution rotor-position predictor can be derived by fitting the predefined position data from binary Hall position sensors in a linear or quadratic manner; (2) by adopting the dual-sampling-rate observer, instantaneous speed can be estimated at each control cycle and the estimation error is corrected once a new measurement form the Hall arrives. Furthermore, a nonlinear position control algorithm is introduced to increase standstill stability. Extensive experimental results are given to demonstrate the feasibility of the proposed method and its superiority over conventional methods.

Parabola‐trapezoid and staircase current supply methods for PMBLM with full inverter utility and reduced torque ripple

The permanent magnet brushless motors (PMBLM) are utilised extensively in many high-performance applications where smoothness of output torque is necessary. When driven with conventional square-wave current, the PMBLM is hard to make full use of inverter capacity because of short current supply time. Besides, it is hard to produce smooth output torque because the phase inductances slow down the desired step response of the phase current seriously. Although the sinusoidal-wave current changes continuously, there exists a fixed-frequency torque ripple for trapezoid back-electromotive force motor. To solve the problems, two novel current supply methods, called as staircase waveform and parabola-trapezoid waveform, are proposed in this study. With the same phase current magnitude as square waveform, the staircase waveform can output two times torque with low-resolution position sensors. The parabola-trapezoid supply method can further improve the smoothness of doubled output torque by unique parabolic rising and falling edge waveform design, while a high-resolution position sensor is needed. Simulation and experimental tests of four different current supply methods are given to corroborate the effectiveness of the proposed method in inverter utility and torque ripple reduction.

Speed Control using Kalman Filter in Permanent Magnet Synchronous Motor Drive with a Low Resolution Position Sensor

This paper presents an improved speed control of surface-mounted permanent magnet synchronous motor(SPMSM) using Kalman Filter algorithm. Rotor position is detected by a low resolution position sensor of 3 hall position sensors at every 60 electrical degrees. The detected outputs of 3 hall position sensors are inputted to Kalman Filter algorithm. Then rotor speed and position are estimated using Kalman Filter algorithm. Simulation results show that the speed control of conventional method which speed and position are directly calculated using the outputs of 3 hall position sensors can not be achieved under load torque of 2N.m in low speed region, whereas the speed control in low speed region under load torque of 2N.m can be achieved by the proposed method.

Variable Sampling Effect for BLDC Motors using Fuzzy PI Controller

Background/Objectives: The variable sampling effect the response time taken to attain its speed of the motor is low whereas, response time is high. Methods/Statistical Analysis: The simulation tool includes three parts, the first is continuous time model of BLDC motors, the second is variable sampling trigger, and the next is the discrete time speed and variable sampling time constant estimator. Findings: Variable sampling systems describe a class of systems whose sensor outputs are obtainable only at some situations not specified by the sampling mechanism. In our proposed work, a fuzzy PI controller based on variable sampling for BLDC motor drives with low resolution position sensors (Hall sensors). It is not only easy to understand as the conventional PI controller, but also more robust in variable speed control. We use three PI controller based on different sampling time at the same time, a fuzzy logic controller to calculate command. The only input variable of our fuzzy logic is rotor speed of the BLDC motor, because the sampling time thus becomes a variable according to the motor speed and the response time is high. Application/Improvements: This type method used for air-conditioner, fans etc.

Self-Compensation of the Commutation Angle Based on DC-Link Current for High-Speed Brushless DC Motors With Low Inductance

As low-resolution position sensors, a high placement accuracy of Hall-effect sensors is hard to achieve. Accordingly, a commutation angle error is generated. The commutation angle error will inevitably increase the loss of the low inductance motor and even cause serious consequence, which is the abnormal conduction of a freewheeling diode in the unexcited phase especially at high speed. In this paper, the influence of the commutation angle error on the power loss for the high-speed brushless dc motor with low inductance and nonideal back electromotive force in a magnetically suspended control moment gyro (MSCMG) is analyzed in detail. In order to achieve low steady-state loss of an MSCMG for space application, a straightforward method of self-compensation of commutation angle based on dc-link current is proposed. Both simulation and experimental results confirm the feasibility and effectiveness of the proposed method.

Design and Dynamic Analysis of Magnetically Levitated Electromagnets With Low-Resolution Position Sensor

This paper reports on the design and dynamic analysis of magnetically levitated electromagnets with a low-resolution position sensor. On the basis of the equivalent magnetic circuit method and a 3-D finite element analysis model, an initial and detailed design of an electromagnet was realized. The validity of the design was confirmed analytically and experimentally. Then, by employing a closed-loop proportional-integral-derivative control algorithm, the dynamic behavior of the electromagnets was also investigated experimentally. In particular, by employing low-pass filters for a low-resolution position sensor and an acceleration sensor, the air gap could be precisely controlled at low cost.

Improved velocity estimation using low-performance position and torque sensors with applications in friction compensation control systems

Velocity computation based on simple numerical differentiation from a low-resolution position sensor or numerical integration from an imperfect torque sensor may be highly erroneous, especially in the low-velocity or high-acceleration regions. To resolve this problem, a novel approach to obtaining high-performance velocities in these regions is presented. The proposed estimator is based on the framework of the Kalman filter. A switching architecture is used to address the estimation problem, with the sensors functioning under different situations. Experimental results show that the proposed estimator significantly reduces velocity errors in estimation compared with an encoder or torque sensor. A dual-loop control structure is also developed with estimated velocity feedback for application in the friction compensation control system of an inertially stabilized platform. Experimental findings show that the control characteristic significantly improves because the proposed approach enables the rejection of non-linear friction.

Torque Ripple Reduction of a PM Synchronous Motor for Electric Power Steering using a Low Resolution Position Sensor

MDPS (motor driven power steering) systems have been widely used in vehicles due to their improved fuel efficiency and steering performance when compared to conventional hydraulic steering. However, the reduction of torque ripples and material cost are important issues. A low resolution position sensor for MDPS is one of the candidates for reducing the material costs. However, it may increases the torque ripple due to the current harmonics caused by low resolution encoder signals. In this paper, the torque ripple caused by the quantized rotor position of the low resolution encoder is analyzed. To reduce the torque ripples caused by the quantization of the encoder signals, the rotor position and the speed are estimated by measuring the frequency of the encoder signals. In addition, the compensating q-axis current is added to the current command so that the 6th order torque harmonic is attenuated. The reduction of torque ripples by applying the estimated rotor position and the compensated q-axis current is verified through experimental results.

A Variable-Sampling Controller for Brushless DC Motor Drives With Low-Resolution Position Sensors

This paper proposes a variable-sampling variable structure controller (VSC) for brushless dc (BLDC) motor drives with low-resolution position sensors (Hall sensors). The variable-sampling characteristics arising from the situation where measurements depend on the path-embedded sensors will result in the uncertainty of the discrete-time models. To circumvent this issue, a modification of the conventional discrete-time VSC control law for BLDC motor drives with Hall sensors is derived to achieve the robustness of speed control. Three measurement error-mitigation methods are also presented to reduce the errors due to low-resolution position feedback. Both simulated and experimental results confirm the effectiveness of the proposed controller and error-mitigation techniques.

Simple Current Phase Control for Current Sensor-less Sinusoidal Drive System of Permanent Magnet Synchronous Motor with Low-resolution Position Sensor

Recently, the sinusoidal drive of a permanent magnet synchronous motor has been actively researched because of its low noise and low vibration. Moreover, the sinusoidal drive system which uses only a low-resolution position sensor without utilizing the current sensor is researched. This paper proposes the method for deciding the lead angle of the impressed voltage by an easy expression for current sensor-less sinusoidal drive system of a permanent magnet synchronous motor with a low-resolution position sensor. The method is a technique for indirectly controlling the current phase without the dq axis transformation. First, the control method of adjusting the current of d axis to almost 0 and the control method of the weakening magnetic flux were shown. And, the methods were examined in numerical analyses. Next, the effectiveness of the proposed phase control method was verified using an actual motor. In the control method of adjusting the d-axis current to almost 0, the locus of the current vector was confirmed and an excellent transient response for controlling the current of d axis was obtained. Moreover, it was confirmed that the increase of applied voltage was controlled and the range of the drive had expanded in the method of the flux-weakening control.

Improvement of Performance and Stability of a Drive System with a Low-Resolution Position Sensor by Multirate Sampling Observer

Low-resolution encoders are normally used as speed sensors in many traction drive systems, such as electric trains, electric vehicles, etc. For example, 60-pulse-per-revolution pulse generators are used to detect speed for electric railway vehicles and low-resolution Hall-effect sensors are commonly used in many electric vehicles. Fig. 1 illustrates the sensors. The signals from these kinds of sensors are pulses, which are then used to calculated speed and acceleration. The speed and the acceleration, therefore, are updated only when the next pulse is detected. As a result, the speed and the acceleration cannot be achieved precisely, especially at low speed. Nowadays, high-frequency digital sampling processors (DSP) are commonly used as controllers. This allows us to precisely control the system. However, it is very difficult to realize in the mentioned systems since the low-resolution sensors are installed. Fig. 2 illustrates the condition at low speed. The period between two consecutive pulses, T1, is longer than the control period, T2. It implies that precise control cannot be achieved even though the high-frequency DSPs are used. To solve this problem, an instantaneous speed observer was proposed to estimate the speed between two consecutive encoder’s pulses. The instantaneous speed observer is a specific discrete-time observer, which estimates the speed at every sampling time and corrects the estimated speed when the next pulse is detected. As a result, the precise speed is achieved at every sampling time. The instantaneous speed observer can also be used to improve the performance of linear scales for linear drives. Its concept is also useful for visual servo, where the sampling rate of the CCD camera is much slower than the sampling rate of the controller. However, the model of the instantaneous speed observer is very specific and limited to motor drive, and its application cannot be extended for the higher order plant such as robot manipulators. For traction control, one of the difficulties is that it deals with a wide speed range. The authors also applied the instantaneous speed observer for speed estimation of train speed. To apply the instantaneous speed observer, which is designed in discrete-time domain, it is necessary to change the observer gains according to the speed to prevent the noise problem at high speed and instability problem at low speed. The observer gain was tuned by simply considering only the relation of pole locations on sand zplanes. As a result, the system can operate stably in a Improvement of Performance and Stability of a Drive System with a Low-Resolution Position Sensor by Multirate Sampling Observer

High-performance current-sensorless drive for PMSM and synRM with only low-resolution position sensor

This paper proposes the current-sensorless drive system with only low-resolution position sensor in order to simplify the synchronous motor drive system. The high-performance current vector control can be achieved in the proposed drive system, where the current sensors are eliminated but the simulated currents based on motor model are used for current control. The low-resolution position sensor, which has a resolution of only 60 electrical degrees, is used instead of a conventional high-resolution position sensor, and the position information with higher resolution is estimated. The steady-state performance and dynamic performance are examined by several drive tests with respect to the interior permanent-magnet synchronous motor and the synchronous reluctance motor. The effectiveness of the proposed drive system is clarified from several experimental results.

A current sensorless drive system of a synchronous motor with a low‐resolution position sensor

AbstractHigh‐performance drive of synchronous motors such as a permanent magnet synchronous motor and a synchronous reluctance motor can be achieved by current vector control. In such drive systems, the armature current is controlled as a sinusoidal waveform based on rotor position information from a high‐resolution position sensor, and the current vector (d‐ and q‐axis currents) is suitably controlled by current feedback control.This paper proposes a current sensorless drive system with a low‐resolution position sensor in order to simplify the SM drive system. High‐performance current control is achieved in the proposed drive system, where the current sensors are eliminated and the simulated currents are used for current control. The low‐resolution position sensor is used instead of a conventional high‐resolution position sensor, and the higher position information is estimated. The steady‐state and transient characteristics are examined in several experiments with respect to the synchronous reluctance motor and the interior permanent magnet synchronous motor. It is confirmed that sinusoidal current drive, high‐performance current vector control, and speed control can be achieved by the proposed drive system. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 34–43, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10072

Current Sensorless Drive System of Synchronous Motor with Low-resolution Position Sensor

The high-performance drives of synchronous motors such as a permanent magnet synchronous motor and a synchronous reluctance motor can be achieved by the current vector control. In such drive system, the armature current is controlled as a sinusoidal waveform based on the rotor position information from a high-resolution position sensor and the current vector (d and q-axis currents) is suitably controlled by the current feedback control.This paper proposes the current sensorless drive system with a low-resolution position sensor in order to simplify the SM drive system. The high-performance current control is achieved in the proposed drive system, where the current sensors are eliminated and the simulated currents are used for current control. The low-resolution position sensor is used instead of a conventional high-resolution position sensor, and the higher position information is estimated. The steady-state and transient characteristics are examined by the several experiments with respect to the synchronous reluctance motor and the interior permanent magnet synchronous motor. It is confirmed that the sinusoidal current drive, the high-performance current vector control and the speed control can be achieved by the proposed drive system.

PM Motor Drive System with Low Resolution Position Sensor

The high performance drives of PM motor with a sinusoidal back-EMF can be achieved by the current vector control, where the armature current is controlled as a sinusoidal waveform based on the rotor position information and the current phase is suitably controlled according to the operating condition. In such high performance drive system, a high resolution position information is desired. In this paper, a sinusoidal current drive system with a low resolution position sensor is proposed. The high resolution position information is obtained by the position estimating circuit from the signal of a low resolution positionn sensor. The steady-state and transient characteristics are examined by the several experiments, then it is confirmed that the sinusoidal current drive, the high performance current vector control and the speed control can be achieved by the proposed drive system.

Commutation of SR motors

Commutation schemes for most common types of switched reluctance (SR) motors are presented. Commutation can be achieved using two- or three-positions sensors and a simple commutation logic in a similar fashion to brushless electronically commutated motors. The commutation logic can be easily housed on a programmable logic array (PLA) or similar device. Two-quadrant operation, usually with two position sensors with variable phase shift and dwell angles, can be tuned up to achieve optimum efficiency at low cost. Four-quadrant operation with multimode commutation schemes, such as normal, boost, longdwell, and brake, which cover most of the SR drive applications, can be easily implemented with simple logic control and feedback from low-resolution position sensors. The speed range can be increased beyond the limit reachable with pulse-width modulation (PWM). A 100% increase in the speed range can be easily obtained by switching modes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>