4. EV conversion tuning and diagnostics

Model-based design can be employed to simulate scenarios where problem might occur during EV conversion process or to figure out the root cause of the problem [18]. The problem can then be realized beforehand by scenario test run to prevent the damage of the EV components and saving time to reinstall new part. The examples of model-based design for tuning and diagnostics can be demonstrated below.

#### 4.1. Motor sizing mismatch scenario

This problem can occur during test run of EV conversion prototype where the motor drive converter becomes too hot during initial run of the EV. This problem forces the drive component to shut down to prevent circuit overheat. Therefore, the EV has to stop early to be checked. The torque map simulation can be executed to check whether there is mismatch between driving load and motor sizing as seen in Figure 14 or there is some serge in current during EV driving simulation due to poor EV conversion system design as seen Figure 15.

4.2. EV conversion driving range and energy storage technology

Figure 15. EV simulation show excess current drawn from batteries during some period of EV driving.

4.3. Fault-tolerant simulation

when fault is detected within the EV system.

4.4. Noise and vibration simulation

For the simplicity of modeling, PEM fuel cell with the lower heating value (LHV) plant will be reasonably modeled as a system with approximated value of efficiency [6]. Mass of liquid hydrogen supplied from cryogenic tank is calibrated to provide the same amount of energy supplied when compared to battery source. Because the fuel cell system was employed to entirely replace the batteries, regenerative braking option was not available. Comprehensive review for other types of fuel cell system and hydrogen storage for electric vehicle can be found in Larminie and Lowry's literature [4, 6]. To model the power flow model for fuel cell electric pickup truck, the battery unit is simply replaced by fuel cell system for one way flow of power since there is no regenerative braking option available. The analysis can be seen in Ref. [8].

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Another important aspect for EV reliability is the fault-tolerant function. This is the safety feature when the main components of the EV, such as ECU or sensors, are malfunctioned. It ensures that EV can still provide safe operation, although in an inefficient manner. One scenario is limp home mode where EV can still be driven under limited speed and performance. By employing model-based design, limp home mode scenarios can be simulated and analyzed. As a result, accelerator redundant system can be designed and tested to compensate

Improper installation or configuration of EV components could seriously induce noise and vibration, resulting in damage or shorter lifespan of EV components or undesirable noise level. EV mechanical system model can be simulated at early stage to validate the level of noise, and vibration is acceptable before the actual bench testing. Vibration characteristics such as resonance

Figure 14. EV torque map results show mismatch in driving load vs. motor power.

Figure 15. EV simulation show excess current drawn from batteries during some period of EV driving.

#### 4.2. EV conversion driving range and energy storage technology

For the simplicity of modeling, PEM fuel cell with the lower heating value (LHV) plant will be reasonably modeled as a system with approximated value of efficiency [6]. Mass of liquid hydrogen supplied from cryogenic tank is calibrated to provide the same amount of energy supplied when compared to battery source. Because the fuel cell system was employed to entirely replace the batteries, regenerative braking option was not available. Comprehensive review for other types of fuel cell system and hydrogen storage for electric vehicle can be found in Larminie and Lowry's literature [4, 6]. To model the power flow model for fuel cell electric pickup truck, the battery unit is simply replaced by fuel cell system for one way flow of power since there is no regenerative braking option available. The analysis can be seen in Ref. [8].

#### 4.3. Fault-tolerant simulation

Based on the driving profile, the test results can be analyzed. In-depth test analysis can be consulted in Ref. [9]. In this case, performance parameters such as vehicle speed and accelera-

Model-based design can be employed to simulate scenarios where problem might occur during EV conversion process or to figure out the root cause of the problem [18]. The problem can then be realized beforehand by scenario test run to prevent the damage of the EV components and saving time to reinstall new part. The examples of model-based design for tuning

This problem can occur during test run of EV conversion prototype where the motor drive converter becomes too hot during initial run of the EV. This problem forces the drive component to shut down to prevent circuit overheat. Therefore, the EV has to stop early to be checked. The torque map simulation can be executed to check whether there is mismatch between driving load and motor sizing as seen in Figure 14 or there is some serge in current during EV driving simulation due to poor EV conversion system design as seen Figure 15.

tion are monitored for ECU validation.

16 New Trends in Electrical Vehicle Powertrains

4. EV conversion tuning and diagnostics

and diagnostics can be demonstrated below.

Figure 14. EV torque map results show mismatch in driving load vs. motor power.

4.1. Motor sizing mismatch scenario

Another important aspect for EV reliability is the fault-tolerant function. This is the safety feature when the main components of the EV, such as ECU or sensors, are malfunctioned. It ensures that EV can still provide safe operation, although in an inefficient manner. One scenario is limp home mode where EV can still be driven under limited speed and performance. By employing model-based design, limp home mode scenarios can be simulated and analyzed. As a result, accelerator redundant system can be designed and tested to compensate when fault is detected within the EV system.

#### 4.4. Noise and vibration simulation

Improper installation or configuration of EV components could seriously induce noise and vibration, resulting in damage or shorter lifespan of EV components or undesirable noise level. EV mechanical system model can be simulated at early stage to validate the level of noise, and vibration is acceptable before the actual bench testing. Vibration characteristics such as resonance and force inducted due to rotating unbalance of the motor can be investigated and analyzed by means of model-based system design approach as well. Thus, proper noise and vibration handling method for EV system can be applied to protect and maintain EV components.

[4] Vuli P, Badalament M, Jaikamal V. Maximizing test asset re-use across MiL, SiL, and HiL development platforms. SAE Technical Paper 2010–01-0660. 2010. DOI: 10.4271/2010-01-0660

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[5] Himmler A, Lamberg K, Beine M. Hardware-in-the-loop testing in the context of ISO

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ISBN: 0-470-85163-5

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#### 5. Conclusion

Model-based system analysis can be helpful to improve EV conversion system design, software and ECU development, testing, tuning, and diagnostic processes along with the actual EV prototype fabrication. It can also be used as a decision-making tool for future EV customization process. This methodology would benefit for EV conversion not only in terms of saving cost but also to shorten development period. As a result, reliable and low-cost EV conversion can be established.
