Yasushi Amano

A Novel Seamless Direct Torque Control for Electric Drive Vehicles

Electric drive vehicles (EDV) have received much attention recently because of their environmental and energy benefits. In an EDV, the motor drive system directly influences the performance of the propulsion system. However, the available DC voltage is limited, which limits the maximum speed of the motors. At high speeds, the inverter voltage increases if the square wave (SW) voltage (six-step operation) is used. Although conventional direct torque control (DTC) has several advantages, it cannot work in the six-step mode required in high-speed applications. In this paper, a single-mode seamless DTC for AC motors is proposed. In this scheme, the trajectory of the reference flux changes continuously between circular and hexagonal paths. Therefore, the armature voltage changes smoothly from a high-frequency switching pattern to a square wave pattern without torque discontinuity. In addition, because multi-mode controllers are not used, implementation is more straightforward. Simulation results show the voltage pattern changes smoothly when the motor speed changes, and consequently, torque control without torque discontinuity is possible in the field weakening area even with a six-step voltage pattern.

A new direct torque control for AC motors with over modulation ability

Comparison of various motor drives has revealed that direct torque control (DTC) drive has several advantages and a much faster torque response compared to other AC or DC drives. However, the conventional DTC cannot operate in the six-step mode, which is required in high-speed applications. Therefore, an accurate method is essential in order to achieve a seamless transformation between conventional DTC and six-step operation. In the present paper, a single-mode seamless control of AC motors is achieved by proposing a new direct torque control. Since seamless control is not possible using the conventional DTC, we develop a new DTC in which the flux trajectory is modified. In the proposed method, the motor flux trajectory changes continuously between a circular shape and a hexagonal shape, and thus the inverter voltage changes from high-frequency switching to a six-step square wave with only one control mode. Therefore, in the proposed method, which uses only one mode, torque discontinuity does not occur because this discontinuity usually occurs during switching between modes. In addition, since the proposed method is a single-mode control, this method is much simpler than existing technologies, which are based on multi-mode controllers.

Active Safety Performance Analysis of Man-Vehicle System due to Driver's Maneuver in Emergency Avoidance.

Taking driver-vehicle closed loop system into account, active safety performances in emergency situation were analysed and the evaluation methods were proposed. Under such critical conditions, ordinary drivers avoiding maneuvers were examined using a motion-type driving simulator. According to the drivers maneuvers, a database of driving operational characteristics was constructed and a mathematical model of drivers operation was also derived. The performance of the driver-vehicle system was predicted by computational simulations. The agreements with the predicted performance by the simulation were verified from experimental results in emergency avoidance. Assuming the sudden change of road surface to slippery situation, the effect of an assistant control of steering was also estimated from both model simulations and experiments by the driving simulator.

Driver Behavior Model in Emergency Situations. On Basic Structure of A Driver Model.

The purpose of this paper is to show basic structure of a driver model that simulate drivers behaviors in emergency situations. The features of this model are that the parameters are systematically set up without trial and error by using predictive control method and a drivers internal model is introduced and a minimum lateral jerk line is applied as target course. The results of experiments to decide the structure, the internal model and predictive time, are shown. The model was applied to simulate drivers behaviors in lane change maneuver. It follows from the results that the driver model adequately simulate general and expert drivers behavior in experiment.

A Driver Behavior Model in Emergency Situations. An Application of the Driver Model to Cases of Obstacle Avoidance and Sudden Change of Vehicle's Characteristics.

The purpose of this paper is to propose a driver model in emergency situations. The emergency situations are cases that an obstacle ran out of the lane and friction between tire and road surface changed suddenly. So far it has not been clarified yet the influences of slip angle of on the drivers behavior and modeling of the combined use of steering and braking in the situations. Results of computer simulations using the driver model are correspond to driver behaviors obtained by experiments with driving simulators. It is verified from the results that the driver model is useful tool that predict behaviors of man-vehicle system in emergency situations.