Development of fail-safe technologies of ultra high performance EV 'KAZ'

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Development of fail-safe technologies of ultra high performance EV 'KAZ'

Kawakami, K. / Matsugaura, S. / Onishi, M. / Shimizu, H.

Keio University developed a high performance multi-purpose EV (electric vehicle) named KAZ (Keio Advanced Zero emission vehicle). In the past, EVs had problems wich low performance and poor reliability of the new technologies incorporated into the cars. To achieve both high driving perfomance and high safety performance, we developed fail-safe technologies for the basic functions of the car - acceleration, braking and cornering - as well as for the main vehicle controller that controls the primary electric components of the car. For the acceleration, the control algorithm allows KAZ to keep running even if a certain motor or peripheral device breaks down. In the braking system, the regenerative brake and the mechanical brake can be independently controlled by installation of a hydraulic pressure control valve. This not only improves the collection rate of the regenerative energy but also avoids the traffic accident if the motor breaks down. To maximize comering performance, steering gear boxes wich electrical assistance were installed on the first and second axles. As a result, if the electrical assistance of either axle breaks down, the driver can maintain control by electrical assistance of the other axle. Moreover, it is possible to generate the cornering force by the torque difference between the right motor and the left motor, according to the angle of the steering wheel. To improve the reliability of communication between the main vehicle controller and the eight inverters, each component was connected in pairs, rather than a daisy-chain configuration. By using these fail-safe technologies, KAZ achieved a top speed of 311 km/h and a range per charge of 300 km at a constant speed of 100 km/h.