Tae-Suk Kwon

Novel Antiwindup of a Current Regulator of a Surface-Mounted Permanent-Magnet Motor for Flux-Weakening Control

This paper proposes a novel antiwindup method of current regulator for the drive system of a surface-mounted permanent-magnet synchronous motor at flux-weakening region. It is designed in conjunction with the synchronous-frame proportional and integral current regulator and the space vector pulse width modulation. The difference between the regulator output voltage and the saturated voltage on the q-axis of the regulator is used for flux-weakening control, which modifies the d-axis current reference. With this method, the antiwindup and the flux-weakening control can be achieved simultaneously. Since the proposed method utilizes the dc-link voltage more efficiently, it makes the motor generate higher output torque than the conventional antiwindup and/or flux-weakening control methods under the same voltage and current limitation. The effectiveness of this method is confirmed by computer simulations and experiments

Power Control Algorithm for Hybrid Excavator With Supercapacitor

This paper shows several structures of the hybrid excavator with the supercapacitor and compares them with each other from the aspect of fuel efficiency, the additional cost due to the hybridization, and the expected payback time. According to the comparison result, it can be concluded that a compound-type hybrid structure is a better solution than others because of its short expected payback time and higher reliability. In addition, the power control algorithm of the engine and the supercapacitor is proposed. To verify the proposed algorithm, the computer simulation and the engine dynamo test were performed, and the results are presented. The results show that the proposed control algorithm can achieve balance of the power and the energy between the energy sources and the load, and by hybridization, the fuel consumption can be reduced by about 24% compared with the conventional hydraulic excavator. The hardware implementation is now in progress for a 22-ton class excavator.

Power Control Algorithm for Hybrid Excavator with Super Capacitor

This paper shows several structures of the hybrid excavator with the super capacitor and compares with each other at the view point of the fuel economy, the additional cost due to the hybridization, and the expected payback time. According to the comparison result, it can be concluded that a compound type hybrid structure is better solution than others because of its short expected payback time and higher reliability. And also, the power control algorithm of the engine and the super capacitor is proposed. To verify the proposed algorithm, the computer simulation is performed and the results are presented. The simulation results show that by hybridization, the fuel consumption can be reduced by about 24% compared to the conventional hydraulic excavator. The hardware implementation is now in progress for a 22 ton class excavator.

Design and Control of an Axial Flux Machine for a Wide Flux-Weakening Operation Region

This paper describes the strategy to design and control an axial-flux (AxF) surface-mounted permanent-magnet machine for achieving a wide flux-weakening (FW) operating region. By using a slotted stator with fractional-slot windings and additional cores enclosing end windings, the AxF machine satisfies the specification of a wide constant-power speed range. The design procedure is presented for increasing FW capability while obtaining low-harmonic back electromotive force and low cogging torque. This technique is applied to design an 8-Nldrm AxF prototype machine that exhibits about 3 : 1 FW range. To the aim of exploiting full capability of the machine, an FW controller is designed and implemented. This controller utilizes the voltage difference between the current regulator and the output voltage, limited by a voltage source inverter. With this method, the output torque in the FW region is higher than that achieved using the conventional FW method based on the voltage-magnitude feedback. The goodness of both design and control algorithm is proved by experimental tests on a prototype.

Novel anti-windup of a current regulator of a surface-mounted permanent-magnet motor for flux-weakening control

This paper proposes a novel antiwindup method of current regulator for the drive system of a surface-mounted permanent-magnet synchronous motor at flux-weakening region. It is designed in conjunction with the synchronous-frame proportional and integral current regulator and the space vector pulse width modulation. The difference between the regulator output voltage and the saturated voltage on the q-axis of the regulator is used for flux-weakening control, which modifies the d-axis current reference. With this method, the antiwindup and the flux-weakening control can be achieved simultaneously. Since the proposed method utilizes the dc-link voltage more efficiently, it makes the motor generate higher output torque than the conventional antiwindup and/or flux-weakening control methods under the same voltage and current limitation. The effectiveness of this method is confirmed by computer simulations and experiments

Identification of the Mechanical Parameters for Servo Drive

This paper describes a novel identification technique of the moment of inertia and the viscous friction coefficient for a servo drive system. It is developed based on the basic dynamic equation of a mechanical system, and it uses the torque reference of a speed controller and the actual rotating speed of machine for the identification. Regardless of the simplicity of the techniques it is robust to external disturbances such as measurement noise, Coulomb friction, mechanical resonance of the drive system. The identified inertia and friction can be used for auto-tuning of the gains in the speed controller and the disturbance observer. The effectiveness of the proposed method is proved by the computer simulation and experimental results

A simple method to minimize effects of temperature variation on IPMSM control in real-time manner

This paper proposes a simplified method to minimize the effects of the temperature variation on IPMSM (Interior Permanent Magnet Synchronous Machine) control in a real-time manner especially in vehicle traction applications. Nowadays, normally an IPMSM with a rare-earth magnet is used for HEV traction applications. But because the flux density of the magnet varies with temperature, the optimal operating points, such as MTPA (Maximum Torque Per Ampere) and MTPV (Maximum Torque Per Voltage) of the motor drift according to temperature change. Conventionally, to minimize the effects of the temperature dependence in control, usually flux tables are generated at high, medium and low temperatures. And all the three tables are constructed by experiment, which takes a great deal of time. In this paper, suggested is a simplified way with which the effects of the temperature variations are minimized real-time in control using a flux table at the only one temperature and the back EMF constants according to temperature change. The proposed method is simpler in computation and easier to implement than the conventional.

Fail-Safe Control Strategy of Traction Motor in Electric Mobility with Sensorless Control Scheme

A motor in electric mobility is utilized Eco-friendly vehicles for traction usually. The rotor position is critical factor in motor drive area. If the sensing of rotor position is fail due to potential faults, eco-friendly vehicles are uncontrollable by a driver. This paper proposes a novel sensorless algorithm to estimate the rotor position of interior permanent magnet synchronous motor (IPMSM). The algorithm is used to control vehicle by a fail-safe logic and it can be applied the continuous operation of vehicle, when the sensing of position is fail. This algorithm is comprised of two methods that can be applied in entire speed region. The first is the extended EMF method that uses the extended EMF model with the information of position error. The method is applied to the mid-high speed region of rotor. The second is the high-frequency injection method that estimates the rotor position using the injected high-frequency voltage signal. This method is applied to low-speed region which include zero speed, because there is no EMF or the magnitude of EMF is very small. Finally, the algorithm in this paper is utilized the two explained kinds of method and is verified by experimental results.

Improved speed control of Permanent Magnet Synchronous Machine at overmodulation region

In Permanent Magnet Synchronous Machine (PMSM) drives, linear region, which is inside the inscribed circle of the voltage hexagon in the voltage plane, is mainly used for the stable operation. To enhance torque capability under the limited input DC link voltage, the region outside the inscribed circle of the voltage hexagon, known as overmodulation region, can be exploited in the flux-weakening operation. However, the operation of drive system in the overmodulation region cannot be free from the degradation of speed control performance. This paper presents investigations on control issues in the overmodulation region and proposes an algorithm for improving the speed control performance in the overmodulation region. The effectiveness of the proposed method is verified by computer simulations and experiments.

Analysis of the effect of the parameter variation on the flux weakening controller for improving torque capability

This paper analyzes the effect of the parameter variation on the flux weakening controller which utilizes the difference between the outputs of the current regulator and the PWM block. To perform this analysis, the parameter variation is modeled as a disturbance, and a Bode plot and a time domain response is presented. From the result, it can be known that the flux weakening algorithm itself is robust, but the current controller is subject to the parameter variation. A method to overcome this problem is presented, and the results are verified by computer simulation and experimental results.