Chinchul Choi

Analysis and Compensation of Time Delay Effects in Hardware-in-the-Loop Simulation for Automotive PMSM Drive System

This paper analyzes and compensates unavoidable time delay effects in a hardware-in-the-loop (HIL) simulation for automotive permanent magnet synchronous motordrive systems. The amount of time delay between a digital controller and HIL simulator is investigated. The effects of the time delay are analyzed by use of s-domain representation of the entire closed-loop system. In addition, a stability study has been carried out using a root locus. The analysis results show that the time delay strongly affects the accuracy and stability of the HIL simulation according to increment of the motor angular speed. For an accurate HIL simulation, a compensation of the time delays is applied and verified through comparison with offline simulation results.

Observer-Based Phase-Shift Fault Detection Using Adaptive Threshold for Rotor Position Sensor of Permanent-Magnet Synchronous Machine Drives in Electromechanical Brake

This paper designs an observer-based fault detection method with an adaptive threshold for a rotor-position-sensor fault of permanent-magnet synchronous motor drives in an electromechanical brake (EMB). The observer does not fully agree with the real process due to model uncertainties and parameter variations. To avoid missing or false alarms, a key design issue of the proposed detection method is the adaptive threshold, which is determined by analyzing position estimation errors of the observer. Experimental results using a test bench of an EMB show the effectiveness of the designed method.

Experimental Estimation of Inductance for Interior Permanent Magnet Synchronous Machine Considering Temperature Distribution

This paper quantitatively analyzes inductance estimation errors due to temperature variation and proposes accurate experimental estimation methods considering the temperature distribution of an interior permanent magnet synchronous machine (IPMSM). Accurate knowledge of direct and quadrature-axis inductances is essential for high-performance control of an IPMSM. From the quantitative error analysis results, it is shown that the temperature variation is a very sensitive factor for the accuracy of the experimental estimation of the inductances. For accurate temperature consideration, two experimental estimation approaches are proposed. One uses the temperature measured at end windings to represent the internal temperature of the machine. The other uses both the measured temperature and other temperature information obtained from a temperature distribution analysis. This paper carries out a case study in which the proposed estimation methods are applied to a sample IPMSM with ferrite magnets. Experimental results are compared with finite element analysis (FEA) results in order to verify the effectiveness of the proposed methods.

Multi-domain modeling of Electric Power Steering with PMSM Drive System

This paper presents a multi-domain modeling strategy of electric power steering (EPS) fed by PMSM drive systems which are widely being applied in automotive application. Automotive control systems are complex systems involving multidisciplinary knowledge. According to the glowing number of advanced electrical components like ESP, the complexity is rapidly increasing. In order to accomplish complex analysis tasks, the system is modularized into components that are modeled by suitable domain descriptions for reflecting specific characteristics. A PMSM and inverter are represented by the interconnection of circuit elements. On the other hand, system mechanism and loads are described by differential or algebraic equations. Finally, the controller which includes PWM generators is represented in their functional forms that describe the behavioral properties. And then, those are integrated as entire EPS model for analyzing system behaviour with interactions between each component. The MATLAB/Simulink, which is a de facto standard tool in control and system engineering, and SimPowerSystems environment are selected as a solution of the accurate and intuitive multi-domain modeling of the PMSM driven EPS at the system level.

Detection method for open switch fault in automotive PMSM drives using inverter output voltage estimation

This paper presents an inverter open switch fault detection method which is based on voltage measurement and then uses inverter output voltage estimation for the more reliable detection. To detect the open switch fault, general voltage measurement based methods compare a reference voltage with measured voltage. However, although the system is under healthy condition, there exists voltage deviation between the reference and measured voltage due to non-ideal switching behaviors of the inverter. In addition, because the difference between two AC quantities varies in one rotation cycle, it is difficult to determine threshold value. To overcome these problems in practical case, the presented method uses an estimated voltage instead of direct use of the reference voltage. And a sectoral average value of the difference is defined as a residual instead of instantaneous one. Several sets of experimental results validate the detection capability of the proposed method.

A Design of Linear State Observers for Motorized Seat Belt System

Abstract : This paper describes a design and a verification of linear state observers for a motorized seat belt system to estimate state information such as angular velocity and load torque. The motorized seat belt system provides functions to protect passengers and improve passenger’s convenience. To realize these functions, sensors which can measure an angular velocity and load torque are needed. By use of the linear state observer, state information can be estimated without sensors. The motorized seat belt system is analysed and represented as a state space model which contains load torque as an augmented state. By the developed state space model, a full and reduced order observer are designed and verified by experiments. The full and reduced order observer are also compared from points of view of execution time and noise robustness. Key words : MSB(Motorized Seat Belt, 전동식 안전벨트), State observer(상태 관측기), Full-order observer(전차수 관측기), Reduced-order observer(축소차수 관측기), System model(시스템 모델)

Design and Temporal Analysis of Hardware-in-the-loop Simulation for Testing Motor Control Unit

This paper describes a design and temporal analysis of a hardware-in-the-loop (HIL) simulation environment for testing a motor control unit (MCU). The design concepts and main characteristics including unavoidable time delays of each component module are described. From temporal analysis results according to the module integration method, an appropriate solution is proposed to fix and minimize time delays. In order to verify the effectiveness of the proposed solution, the HIL test results are compared with the results of experiments and an offline simulation.

Dead Time Compensation and Polarity Check of Phase Currents Based on Programmable Low-pass Filter for Automotive Electric Drive Systems

Abstract : This paper proposes a dead time compensation method for an AC motor drive using phase current polarity information which is detected based on a digital programmable low-pass filter (PLPF). The polarity detection using the PLPF is an alternative solution of a conventional method which uses a general low-pass filter (LPF) and hysteresis bands in order to avoid jittering due to noises. The PLPF not only adjusts its cutoff frequency according to the synchronous frequency of AC motors but also eliminates a gain attenuation and phase delay which are main problems of the general LPF. Through the PLPF, a fundamental component signal without gain and phase distortions is extracted from the measured raw current signal with noise. By use of the fundamental component, the polarity of current is effectively detected by reducing the hysteresis band. Finally, the proposed method compensates the dead time effects by adding or subtracting average voltage value to voltage references of the controller according to the detected current polarity infor-mation. The proposed compensation method is experimentally verified by compared with the conventional method.

Performance Improvement of PMSM Current Control using Gain Attenuation and Phase Delay Compensated LPF

Abstract : This paper applies a compensated low pass filter (LPF) to current measurements for permanent magnet synchronous motor (PMSM) drives. The noise limits the bandwidth of current controllers and has more adverse influences on control performances under the light load condition because of the low signal-to-noise ratio. In order to eliminate the noise sensitivity, this paper proposes a digital LPF with a compensator of gain attenuation and phase delay which are unacceptable in current information for PMSM drives. Characteristics of the proposed LPF are analyzed in comparison with the general LPFs. The compensated LPF is basically designed by the orthogonal property of the measured currents in the  stationary reference frame. In addition, an implementation issue of the proposed method is discussed. Experimental results using the proposed method show improvements of the current control performance from two perspectives, rapid step responses and reductions of harmonic distortion.