2.1.3　System Level Diagram of an EV

Text（课文）

The complete EV consists of not only the electric drive and power electronics for propulsion，but also other subsystems to make the whole system work.In Figure 2.5，one needs a battery（or a fuel cell）to provide the electrical energy.This is shown by the block on the left which provides power to drive the electric motor.The motor is part of the EV power-train，labeled as EVPT on the right.For each of these items，battery or EVPT，there is a controller.The battery controller can control the charging or discharging，and similarly the EVPT controller will control the speed or torque of the motor by controlling the power electronics.It should be realized that even though the blocks in the diagram are shown to be at quite different positions，in reality they could be physically very close.The reason is due to packaging and also，by positioning them nearby，it is possible to reduce the high-current and high-voltage cable lengths.Similarly，although the controllers named the FC controller（for Fuel Cell controller or battery controller）and the EVPT controller are shown separately to indicate separate functionality，in reality they could be part of the same physical box and could even share the same microprocessors to achieve their functions.These aspects are subtle design issues involving cost and packaging.In addition，there is a box shown as the“Interface.”This is the controller box that receives signals and also power，both high voltage for propulsion and low voltage for certain specific devices which operate at low voltage，and then through the“Interface”function channelizes them to the EVPT motor or the high-voltage battery.Again，these function separation blocks may be merged when physically integrating the system.

Figure 2.5　System-level diagram of an EV

In addition to the above blocks，there are various other blocks，for example，the vehicle controller，which can receive signals on the velocity of the vehicle，driver pedal position，and so on，and make a decision whether additional torque is needed from the motor or not，based on that information it can send the signal to the EVPT controller with the appropriate torque request.Similarly the brake controller can receive signals corresponding to brake pedal position，vehicle velocity，and so on，and decide how much brake force is needed.It can also receive signals like the battery's state of charge and can figure out whether the opportunity of regenerative braking is present.If it is possible，it can then send signals to the EVPT controller to carry this out.All this illustrates the importance of continuous flow of information and signals between various control blocks and corresponding decision-making in each subsystem.

Information transmission between various blocks is normally done through a controller area network（CAN）bus.This is basically a type of computer network where a single wire can contain multiple information or communication signals multiplexed together.Some sort of protocol has to be used when multiple signals are to be shared.In other words，there is some sort of priority-based signal flow when trying to share the same physical medium.For relatively slow signals，for example，to turn the door lock switch，one can afford to wait，whereas for very important functions like braking and steering，which are safety functions，the signals need to be transmitted immediately.There are some newer protocols which can allow such activities.In addition，for safety-critical functions，it may be necessary to have additional hardware-based backup communication mechanisms，so as to avoid failures.

New words and expressions（单词和短语）

1.New words（单词）

2.Expressions（短语）

Notes to the text（难点解析）

★1.In addition，there is a box shown as the“Interface.”This is the controller box that receives signals and also power，both high voltage for propulsion and low voltage for certain specific devices which operate at low voltage，and then through the“Interface”function channelizes them to the EVPT motor or the high-voltage battery.另外，还有一个盒子叫“接口”。这是一个接收信号和功率的控制器盒，既包括驱动需要的高压，也包括某些在低压下工作的特定设备所需要的低压。通过这个接口的功能，将这些信号传递到EVPT电动机或高压电池。

★2.It can also receive signals like the battery's state of charge and can figure out whether the opportunity of regenerative braking is present.整车控制器也能接收蓄电池荷电状态信号，判断是否能够进行再生制动。

★3.All this illustrates the importance of continuous flow of information and signals between various control blocks and corresponding decision-making in each subsystem.

所有这些表明，各种控制器模块和进行相应动作的子系统之间连续信息流和信号非常重要。

Exercises（练习）

◆1.Translate the following passages（expressions）into Chinese（英译汉）

（1）It should be realized that even though the blocks in the diagram are shown to be at quite different positions，in reality they could be physically very close.

（2）And similarly the EVPT controller will control the speed or torque of the motor by controlling the power electronics.

（3）The motor is part of the EV power-train，labeled as EVPT on the right.

◆2.Translate the following passages（expressions）into English（汉译英）

（1）汽车车速

（2）电力电子器件

（3）一辆完整的纯电动汽车不仅包括驱动需要的电驱动零部件和电力电子器件，也包括其他一些使整个系统有效工作的子系统。

◆3.Directions:Answer the following questions briefly according to the text

How does EV work？

Reading material（阅读材料）

From a technical viewpoint，the EV has another benefit.In the ICE，which is a reciprocating engine，the torque produced is pulsating in nature.The flywheel helps smooth the torque which would otherwise cause vibration.In the EV，the motor can create a very smooth torque and，in fact，it is possible to do away with the flywheel，thus saving material and manufacturing cost，in addition to reducing weight.And finally，the efficiency of an ICE（gasoline to shaft torque）is very low.The engine itself has about 30%-37% efficiency for a gasoline and about 40% for a diesel engine，but by the time the power arrives at the wheel the efficiency is just 5%-10%.On the other hand，the efficiency of the electric motor is very high，on the order of 90%.The battery and power electronics to drive the motor also have high efficiency.If each of these components has an efficiency on the order of 90%，by the time the battery energy leaves the motor shaft，the overall efficiency will be something like 70%.This is still substantially higher than that in the ICE.