Electric Vehicle Disruption
Electric vehicles are already here and are ready to disrupt the century old legacy of IC engine automobiles. These developments in the field of electric vehicles have forced automobile industry to explore new areas in complete development cycle. This shift is impacting all aspects of vehicle development - materials, manufacturing process, suppliers, development methods, etc. To compete in this run for Electric Vehicle, all vehicle manufacturers(OEM) require a new arm of engineering to handle the biggest change in a vehicle due to electrification i.e. Electric Power-train. This development plan is explored by all OEMs today and have created a necessary need of evaluating these electric vehicles for real life scenarios and worst-case scenarios. Electric Vehicle development in itself is picking up, and it requires an all-around approach for development of testing and validation methodologies to bring these vehicles faster to market.
Note- Internal combustion engines are mentioned as ICE and Electric Vehicles as EV.
To understand new validation challenges in Electric Vehicle, we need to understand the difference it brings to Internal Combustion engine vehicles
*Above table highlights only critical electric vehicle components comparison.
Even though the physics of powertrain is same from torque requirement to load requirement but chemistry of the power generation is changed from gasoline/diesel to lithium.
Electric Vehicle Development Requirements
Electric Vehicle OEMs, likes of Tesla, GM and Nissan are far ahead of others in development and have already set a benchmark for other OEMs. Though this seems disadvantageous for non-Electric Vehicle OEMs to not have any product till date but this also gives them an advantage of lesser development time and cost by benchmarking the present electric vehicles.
- Electric Powertrain Testing- This is an area which requires fast development of validation methodologies.
- Mechanical testing- This is almost similar to the requirement for IC engine validation, with similar test procedures more or less. To read more about this Click here. But there are areas like NVH which require new approach, as reference and the boundary conditions have changed. We have highlighted some NVH related impacts in this blog.
Electric Powertrain Testing
This blog mainly focuses on the tests that can be conducted to get various levels of understanding of EVs for development or benchmarking purpose. When we look at parts in an electric powertrain we can see that each part has contribution in the efficiency, drive experience and overall mileage of a vehicle. We have divided most of these tests into following categories as shown in below diagram: -
- Mapping consumption of energy in various user cases
- Hardware and Software response testing
Mapping Consumption of Energy – Electric Flow and Efficiency Mapping
Change in power source has brought requirement of new methods of testing EVs. We have developed our lists of tests keeping in mind following areas-
- Consumption of electric power,
- New components for efficiency mapping.
- And above all, a new behaviour of depletion of fuel (battery charge) in electric vehicles.
Hardware and Software response testing – HIL Testing
Hardware in loop (HIL) testing eliminates the requirement for real world testing by making the product believe that it is in real world and test it for predefined real-world conditions to evaluate it. The best part is that it can be tested for almost all possible conditions within the lab.
The test cases can also be prepared or customized based on inputs from client’s teams. We also provide inputs for design changes for improvement of the product. We support validation testing of battery management system (BMS), electric vehicle batteries, motor controllers, power inverters and motors.
Signal Level HIL Testing
This is the basic level which incorporates a development ECU that is flashed with a motor control algorithm. The I/O’s of the ECU are mapped to the HIL system. Here power inverter and the motor are in form of MATLAB models. Inputs and outputs of these models are mapped to the ECU through HIL system.
- Algorithm testing for development ECU.
- Inverter and Motor models are simulated and design changes are made for efficiency.
Power Stage Level HIL Testing
At this stage the production ECU is tested with power inverter hardware. Motor controller output and power inverter feedback is analysed along with motor shaft position and feedback coming from the motor model. The I/O’s of the ECU are mapped to the HIL system. Inverter current signals will be mapped to the ECU through HIL system. Motor feedback generated by the motor model will be provided to the ECU through HIL System.
- Production ECU can be tested for algorithm.
- Power inverter is tested for efficiency and output.
- Motor model is simulated and required design changes are made in motor model to increase efficiency.
Vehicle Level HIL Testing
In this, complete powertrain is run according to various test cases incorporating simple to tough scenarios. ECU outputs are analysed with feedback signals generated by power inverter and motor in form of current signals and motor shaft position signal.
Most of the testing requirements from mechanical aspects are similar in Electric Vehicle’s as compared to ICE engine. But areas like NVH and changes in drivability and dynamics, due to motor and battery, has changed the base references of validation. This requires to look at these parameters from new angle and approach. Here we have highlighted on such example for NVH challenges in Electric Vehicle.
Challenges in Noise for Electric Vehicle
Electric Vehicles are very silent compared to IC engine vehicles but they create problem of sound quality due to high frequency and variable sounds.
*Averaged Difference observed is shown here for Example
Following are base references which needs to be understood from new viewpoint for EVs
- Reduced low frequency noise
- Increased high frequency noise
- Reduced load dependency
- Increased road and wind noise sensitivity
However, advantages can be found like reduced overall noise levels for improved passenger comfort
Critical noises observed in Electric Vehicles
- Switching frequencies present a new challenge in the development due to their high frequency.
- Auxiliary Devices sound,becomes more dominant sound once IC engine is removed and thus causes sound quality problems.
- Vacuum pumps for brake assist.
- Battery contactor noise at key on/off.
- Artificial sounds for the vehicle to help minimise the disturbance from these noises and for Pedestrian Awareness.
Challenges in Electric Vehicle Development
Infrastructure is backbone of development and below are major facilities required for Electric Vehicle specific development which are in high Demand in India.
- EMC chamber dependent – Emission and Compatibility Test
- To understand these tests, we need to understand EMC chamber and electronic components which is beyond scope of this paper. But to describe in brief – every electric/electronic component radiates electromagnetic waves which impacts humans as well as nearby components if they cross certain threshold (as governed by Standards). This property is tested in an EMC chamber which absorbs all electromagnetic radiation by definition. To understand by analogy, EMC chamber is for electromagnetic radiation what anechoic chamber is for sound waves.
- Battery Testing Machines
- These machines are used to test battery for various parameters like- Discharge cycles, Temperature, SOC, Health, etc.
- Hardware in Loop testing equipment
- These equipment are used to measure the response of various electrical controllers and devices for different computer defined inputs to understand worst case scenarios and behaviour.
Less Maturity in Electric Vehicle Technology
Electric Vehicle technology for battery is maturing with high pace but today it is not consistent and changes OEM to OEM. This shift takes its toll on mass production and effective market growth for EVs.
Even though awareness for electric vehicles has increased multiple times but the skill level and base knowledge required to develop electric vehicles and to understand them is still limited. This creates a gap in demand and supply which is currently filled by buying off the shelf products from limited players in electric component industry.
Most of the standards are in initial stages of maturity as technology in itself is developing. Thus, dynamic change in technology creates difficulty in setting standards.
Understanding Human aspect of Electric Vehicle is critical as we are accustomed to IC engine vehicle behaviour. Thus, to develop Electric Vehicles for humans, it requires detailed understanding of human response to noise, range anxiety and human confidence on Electric Vehicle Technology. This is being answered by various government research, marketing and technological development but it still needs more maturity to develop standardized figures for these kinds of factors impacting human confidence on EVs.
Advanced Structures India Pvt Ltd is an independent automotive product development company based out of Bangalore, India with operations in India, China and US. Above is a blog entry from our engineers about Electric Vehicle Development. We can be contacted on firstname.lastname@example.org for business enquiries and email@example.com for open positions.