Prius

Introduction

The Toyota Prius c (Fig.1) is a full hybrid gasoline-electric hatchback designed and manufactured by Toyota Motor Corporation. It was introduced in 2012 after great success of the conventional Toyota Prius. According to the United States Environmental Protection Agency (EPA), Toyota Prius c is ranked by the EPA as the most fuel-efficient vehicle on the road in 2013 excluding plug-in hybrid vehicles and pure electric vehicles [1]. This report provides a brief overview of the most important design features of Toyota Prius c and a brief summary of the riding experience I had during the HEV Powertrain class in November 19, 2013





Toyota Hybrid Synergy Drive (HSD) and Test Drive

Similar to the third-generation conventional Toyota Prius, Toyota Prius c is equipped with HSD system but with a smaller Atkinson-cycle engine and more compact Permanent Magnet Synchronous Motor (PMSM)/generator power split device assembly. With smaller curb weight as well as smaller internal combustion engine, the fuel efficiency is extraordinary even compared to the conventional Toyota Prius.



At the heart of Toyota Prius c is the Toyota Hybrid Synergy Drive computer which oversees operations of the entire mechanical and electronic systems of the vehicle. Toyota Hybrid Synergy Drive computer determines which engine/motor/generator should be running at what conditions. Depending on the driving conditions both the engine and motors can be used to power the vehicle. The following section gives details regarding all the driving modes I have experienced during last Tuesday’s test drive.



1. At start off and low speeds of Prius c, HSD runs the car only on electric motor(s) since the internal combustion is not capable of delivering high fuel efficiency at low speeds.

2. During normal driving, the vehicle is powered mainly by the gasoline engine. Part of the power is distributed to the generator MG1 to recharge the battery.

3. During full acceleration, such as climbing a hill or overtaking a car, both the gasoline engine and the electric motor MG2 power the vehicle.

4. During deceleration, such as when braking, the vehicle regenerates kinetic energy from the front wheels through MG2 (acting as an electric generator) to produce electricity that recharges the battery pack.



5. When the vehicle is stopped, the engine might be turned on to recharge the battery if the battery level is considered to be very low (i.e. stationary charging mode).




ZENN Electric Vehicle (EV)

In addition to the Toyota Prius c, the CHARGE also uses pure EV to conduct research and experiments. ZENN, which stands for zero emission and no noise, is a two-seat pure EV designed and built by ZENN Motor Company to satisfy people’s need for small and neighborhood-only vehicles that do not require full certification as conventional automobiles.



ZENN is equipped with a 30-hp permanent magnet synchronous motor and six 12 Volts sealed lead-acid batteries. Among all six batteries, four of them are placed at the back of the vehicle, and two are placed close to the electric motor under the “engine hood”. In this way, the weight of the entire vehicle can be evenly distributed, which improves a variety of vehicle characteristics including handling, acceleration and traction. ZENN has a maximum speed of 40 Km/h, and its maximum range before requiring a recharge is about 65 Km.



Conclusion



There is no doubt that automotive manufactures are going to pay more attention to the development of HEVs and EVs. Although both HEVs and EVs are feasible solutions to the environmental problems and high oil prices, unless there is a breakthrough in battery technology to allow people to charge their vehicles more conveniently (e.g. similar to refill their gas tank in a gas station) as well as to allow people to drive at least 500 km with a single charge, EVs will not be widely accepted by the public, and HEVs will continue to dominate the market with no compromise in terms of practicality and fuel-efficiency.