This paper describes a motor control method that is designed to reduce vibration in hybrid vehicles (HV).

Vibration that can degrade ride comfort occurs in the following situations.

1) At engine start/stop
In an HV, engine start/stop occurs frequently in the interests of reducing fuel consumption and emissions. This vibration occurs independently of the driver's actions.

2) During rapid acceleration/deceleration
The vibration increases considerably because the electric motor torque can be increased/decreased more rapidly than that of the internal combustion engine.

To address these problems, we have designed two types of controllers. The first controller addresses the problem of engine torque ripple that is caused by the compression reaction force and the pumping pressure in the cylinders. The second controller has been designed to suppress torsional vibration in the drivetrain, which is caused by traction torque ripples or rapid increases/decreases in the traction torque.

Both controllers are realized in software. Practical experiments have shown that the proposed motor controllers reduce vibration and improve ride comfort.

Hideo Nakai, Hiroki Ohtani, Yukio Inaguma

The motors of hybrid electric vehicles must be able to offer high efficiency, a high power/weight ratio, and excellent reliability across the entire rotor speed range. Interior permanent magnet synchronous (IPM) motors are used to satisfy these requirements. The goal of this study was to develop an IPM motor control method that would increase the torque and the efficiency at high and medium rotor speeds. A method for increasing the torque and efficiency at high speeds was described in a previous paper, and is known as voltage phase compensation (VPC).

The method described in the previous paper involved combining VPC with normal current compensation to control the torque across the entire range of speeds, and to increase the torque at high speeds. This method failed, however, to achieve sufficient torque at mid-range speeds.

This paper introduces a new type of compensation (Overmodulation Current Compensation: OCC) that increases the torque at mid-range speeds while achieving current control in the overmodulation range of the inverter. Combining the conventional current compensation, VPC, with OCC achieves an increase in the torque and the efficiency at both high- and mid-range rotor speeds. The type of compensation applied is switched automatically by using the proposed transitional algorithm. This paper shows the validity of the proposed method by using the experimental evaluations.