Page 177 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Hybrid vehicle design CHAPTER 7.1

Fig. 7.1-4 Justifying the hybrid: (a) EV traffic potential; (b) combined series–parallel mode.

7.1.3 Hybrid technology case available the best answer is to use a hybrid-drive line
consisting of a small battery, a 45 kW electric drive, and
studies
a 22.5 kW engine. This solution would increase the
vehicle weight from 750 kg to 860 kg, but it would now
7.1.3.1 The hybrid electric solution for accelerate from 0 to 60 mph in 8 seconds. In addition,
small cars the vehicle will have automatic transmission with re-
generative braking, could operate in electric-only mode
4
Ron Hodkinson points out that US President Bill Clin- with a 30 mile range for use in zero emission mode in city
ton’s initiative for the American family car sets the target centres, and could be recharged from a wall socket or
that, in 2003, cars will run for 100 miles on one US gallon charging point if desired.
of unleaded gasoline. The objectives are reduced fuel The Polaron subsidiary, Nelco, worked with Wych-
consumption, reduced imported oil dependency, and wood Engineering and Midwest Aero Engines on a paral-
reduced pollution to improve air quality. Can it be done? lel hybrid replacement for a front-wheel drive train in
The answer is yes. Work carried out on GM’s ultra-light- family cars and delivery vans, Fig. 7.1-5.
weight car programme involved composite structure to
achieve a body weight of 450 kg, drag coefficient C d < 0.2
by means of streamliningthe underside of the car, reduced 7.1.3.3 Rotary engine with PM motor,
2
frontal area (<1.5 m ), conventional drive train with the mechanical outlines
a 30 bhp two-stroke orbital engine and low-rolling-re-
sistance tyres. Overall, this leads to a vehicle weight of The drive line is a marriage of two techniques: a
750 kg, a 400 kg payload at a top speed of 80 mph and an permanent-magnet brushless DC motor and a Wankel
acceleration of 0–60 mph in 20 seconds. This illustrates two-stroke engine. The electric motor provides instant
the dilemma. Reduce the engine size to improve the fuel acceleration with 45 kWof power available from 1500 to
consumption, and the acceleration performance is 6000 rpm, on this design. A permanent-magnet design is
sacrificed.
used because it is lightweight, highly efficient, and results
in an economical inverter. The concept is to exploit the
7.1.3.2 Hybrid power pack, a better machine characteristics using vector control. At low
solution speeds, the permanent magnets provide the motor field.
At high speeds, the field is weakened by introducing
In the long term we may use electric vehicles using fly- a reactive Id component at right angles to the torque-
wheel storage or fuel cells. Until these systems are producing component Iq. The control objective is to

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