Trends in Automobiles

Architecture of a battery electric vehicle (BEV)

 Charger/AC inlet -> [Battery pack + BMS]
                         |  (400 V DC)
          DC-DC -> 12 V auxiliary battery
                         |
                    [Inverter] <- [Motor controller] <- Pedal
                         |
                    [Motor] -> single-speed gear -> wheels

• Battery pack: lithium-ion cells (300 to 800 V), the energy store; BMS manages it.
• On-board charger: converts AC mains to DC for charging; a DC fast charge goes directly to the pack.
• Inverter / motor controller: converts DC to variable-frequency AC for the motor, controlled by the accelerator input; reversing for regenerative braking.
• Traction motor and transmission: a motor drives wheels through a fixed reduction gear (6 to 10:1) and differential; no clutch or multi-speed gearbox is required.
• DC-DC converter steps down the voltage to 12 V for lights and electronics.
• Thermal management and regenerative braking recover energy.

Induction motor vs PMSM

(a) Functions of a BMS

1. Monitoring of cell voltage, pack current and temperature.
2. State of charge (SoC) and state of health (SoH) estimation.
3. Protection against over-charge, deep discharge, over-current, short circuit and over-temperature, with contactor trip.
4. Cell balancing (passive by resistors or active by transferring charge), so all cells have the same SoC.
5. Thermal management control of cooling or heating.
6. Communication to the vehicle ECU and charger through CAN, and limits of charge/discharge power.

(b) Numerical

Range

$$E_{usable} = 0.9 \times 40 = 36\ \text{kWh}, \qquad \text{Range} = \frac{36\,000}{160} = 225\ \text{km}$$

Charging time

Energy to be stored $= (0.80 - 0.20) \times 40 = 24$ kWh.

$$P_{eff} = 7.4 \times 0.92 = 6.81\ \text{kW}, \qquad t = \frac{24}{6.81} = 3.53\ \text{h}$$

The grid energy used would be $24/0.92 = 26.1$ kWh. (Charging rate in practice tapers near 80 % SoC.)

Answer: range $= 225$ km; charging time $\approx 3.53$ h (3 h 32 min).

(a) Hybrid electric vehicles

A hybrid combines an internal combustion engine (ICE) with an electric motor and a battery to save fuel by regenerative braking and running the engine at its efficient point.

 Series:   ICE -> Generator -> Battery/Inverter -> Motor -> wheels
 Parallel: ICE -----------\
                           >-- transmission -> wheels
           Motor/Battery --/

• Series hybrid: the ICE only drives a generator; wheels are driven only by the electric motor. Simple, the engine runs at its best speed; losses from double conversion. Example: Nissan e-Power.
• Parallel hybrid: both ICE and motor can drive the wheels together or separately via a mechanical link. Efficient on highways. Example: Honda IMA. (Series-parallel, like Toyota Prius, uses a power-split device.)
• Plug-in hybrid (PHEV): a parallel or series hybrid with a larger battery (10 to 25 kWh) that is charged from the grid, giving 30 to 80 km of pure electric range.

(b) Levels of autonomy (SAE J3016)

Sensors: camera, radar, lidar, GNSS and HD maps.

(c) AI and IoT

• AI: deep-learning perception (detect cars, pedestrians), path planning, driver monitoring, predictive maintenance, voice assistants.
• IoT (connected car): vehicle connects to the cloud through 4G/5G for over-the-air (OTA) updates, remote diagnostics, fleet tracking, usage-based insurance, and V2X communication with other vehicles and infrastructure.