In this issue, we would like to describe our chief tester Okabe’s thoughts on our company’s concept of vehicle evaluation.
What is Vehicle Evaluation?
We evaluate vehicles by focusing on two key questions: “What is the value of this vehicle’s performance to the customer, and is the performance commensurate with the price?
Vehicle evaluation can be broadly divided into two categories: sensory evaluation and quantitative evaluation, and relative and absolute evaluation.
| sensory evaluation | quantitative evaluation | |
| a relative evaluation | It is a subjective evaluation by the evaluator, expressed in terms of grades and comments. Several vehicles are prepared and evaluated in comparison to a reference vehicle. | Numerical data is expressed by using measuring instruments, etc. The difference from the reference vehicle is shown in the data and evaluated. |
| evaluation on an absolute scale | Evaluated subjectively by the evaluator and expressed in terms of grades and comments. Evaluated based on the evaluator’s absolute criteria. | Data acquired using measuring instruments, etc., are applied to evaluation indices that serve as absolute standards. |
Sensory evaluation is a subjective evaluation by the evaluation driver, and it is very important that the evaluator’s axis of evaluation is not blurred. For this reason, the experience of the evaluator is extremely important, and it is no exaggeration to say that it is determined by the experience of the evaluation driver to date.
Quantitative evaluation is an objective evaluation and is mainly expressed as data (numerical values) using measuring instruments. However, it is very difficult to obtain quantitative data in actual driving, and requires delicate driving skills, such as driving on a specified road surface within ±2 [km/h]in terms of vehicle speed and entering steering wheel input angle in 5° steps. Reproducibility is especially important, and the driver must be able to drive the same course every time at the same vehicle speed and steering angle.
Preparation for Vehicle Evaluation
The most important item required of the evaluation driver is “not to break the car. Breaking an expensive prototype or a car borrowed from someone else will lead to a big loss, such as postponement of the development period or reimbursement of costs. Therefore, we try to determine how the car will behave by moving it at low speeds and low G-forces. To determine the behavior of a vehicle requires experience and knowledge cultivated over many years.
We pay close attention to “noise” and “vibration” while the vehicle is in motion. If any strange phenomenon is detected, we immediately slow down to a safe speed and return to the maintenance area or pit. This is because if the car becomes immobile or breaks down during the process, it is likely to be difficult to identify the cause.
And you need to have the “courage to stop” when evaluating near the vehicle limits. It is important to always control the vehicle within the limits of one’s driving skill and evaluate with a normal mind. If you do not have a normal mind, you will not be able to make a correct evaluation, and the accuracy of the evaluation results will be low. I always have the “courage to quit” somewhere in my mind, and to date, I have had zero accidents for which I am responsible.
For this reason, it is important to know what level of operating skill you are capable of handling. For example, “the level at which I can control up to 00kw output. If your driving skill is greater than the experimental conditions of the vehicle, you will be able to keep your composure and make calm decisions under any circumstances.
Of course, if you are an evaluation driver, your driving skills must be high. It is necessary to work on improving driving skills by overcoming challenges through driving training and raising the level of driving skills that can be handled. The great evaluation drivers I know are actively engaged in self-improvement.
Vehicle Performance and Vehicle Evaluation
Vehicle performance can be divided into two major categories: dynamic performance and static performance.
The main part of dynamic performance is vehicle dynamic performance, which includes “running, turning, and stopping,” the fundamentals of automobiles, and is divided into five major performance categories: dynamic performance, driving performance, noise vibration performance (NVH), ride comfort performance, handling stability performance, and braking performance. In addition, ADAS performance and HMI performance have recently been emphasized, and the evaluation items are becoming more diverse.
Static performance includes visibility, comfort, operability, interior and exterior high quality, etc., and is a very demanding element because customers can judge whether it is good or bad in showrooms, etc.
We clarify what kind of customers we are targeting with the vehicle we are developing, and what unique points will motivate those customers to purchase the vehicle. We then clarify the important performance features and formulate a winning scenario by comparing it with competing vehicles.
This is where the budget comes in. Budget management is the most important issue in the development of a new vehicle. No matter how good the performance is, if it is over budget, it cannot be made into a product. The evaluation driver is also required to balance performance within a certain number of parts.
For example, suppose you have a developed car that you want to achieve top level fuel economy. You try to improve fuel economy by reducing the rolling resistance of tires, but this will result in a decrease in ride comfort and handling performance. In some cases, the vehicle may even fall short of the target. The evaluation of the vehicle as a whole, including such conflicting performance, is also required.
Simply evaluating whether a vehicle is good or bad does not make you a full-fledged evaluation driver.
We communicate the improved and deteriorated items to the engineers appropriately by making full use of sensory comments and quantitative data. Sensory comments should be spoken in a common language with the engineer. Quantitative data shows the customer’s perception of the phenomenon in terms of result data and factor data that the engineer can incorporate into the design.
My definition of an evaluation driver is to be able to do the above, which requires knowledge of vehicle mechanisms, measurement, and data analysis skills. It is important to have a relationship of trust with the engineer and to be able to evaluate from the customer’s point of view.
Role of the driver in creating and evaluating vehicle characteristics
Although the characteristics of a vehicle are determined to some extent by its packaging, many factors are actually related. Recently, manufacturers have explained that EVs have a low center of gravity and high vehicle stability, but from the standpoint of stability, it is important to have not only a low center of gravity but also properly designed factors such as vehicle body rigidity, suspension mounting rigidity, and suspension alignment changes.
Generally, when developing a new model vehicle (new unit or platform), a prototype vehicle, called an advanced model, is built and many parameter studies are conducted.
The role of the evaluation driver for a prototype is not only to evaluate the vehicle, but also to be involved in the preliminary stages of evaluation. We check many items, such as whether the prototype vehicle performs as designed, whether it is stable to its limits, etc. In the course of these checks, we can determine the general potential and areas for improvement, but it is important to share this information with the engineers through sensory comments and quantitative data that they can understand.
Recently, the accuracy of simulation has been improved and more detailed phenomena can be reproduced.
The performance of the vehicle is created by the teamwork of many evaluation drivers. Finally, the chief driver makes a “go/no go” decision and the vehicle is qualified for production.
As an example, the following phases are used for development and evaluation, so it is crucial to determine how to make a good car in the initial phase.
Initial phase: Determination of very large and large parts for which later design changes are nearly impossible.
Mid-term phase: Determination of parts with significant performance that will be contradicted by changes in parts.
Final phase: Balancing of performance to achieve target performance and confirmation of product quality.
Points to keep in mind during evaluation
As we have mentioned, there are three main points to keep in mind when conducting an evaluation.
- Evaluations or axes must not be blurred.
- Evaluate from the customer’s point of view.
- Always operate in a reproducible manner.
In order to achieve the first, it is important to be able to establish an evaluation axis in your mind. Establishing this axis is the most important task for an evaluation driver.
2, it is important not to evaluate a car based on one’s own likes and dislikes. Customers who purchase sports cars and customers who purchase mini cars have different performance requirements for cars. It is necessary to evaluate the car by understanding the unique points of the developed car while putting yourself in the mindset of the customer in the buying group.
The third is to operate with reproducibility (the same operation) at all times. Different inputs to a vehicle will cause it to behave differently. For example, when evaluating vehicles A and B, if the inputs to the two vehicles are different, the evaluation results will be different.
We will evaluate the car while paying attention to the above three points. After all, a good car will produce good results no matter who drives it. However, those who are inexperienced in evaluation will use expressions such as “It’s kind of nice,” or “It’s firm and clean. I believe that a good evaluation driver is able to convey this part of the evaluation with concrete phenomena.
postscript
As I have written at length, the automotive industry is said to be undergoing a once-in-a-century transformation.
Despite the use of words such as “environmental issues,” “CASE,” “Maas,” etc., we believe that the role and value of the evaluation driver will remain the same in any era: “At the end of the day, people will decide.
This article was written by.
OKABE Masato
Chief Tester
Worked for 34 years as a kinematic performance test engineer (mainly in charge of chassis development) for a major OEM.
Current position since 2019. His specialty is evaluation of kinematic performance using logical explanations and quantitative data.
Not only has experience in tuning chassis, 4WD and other chassis controls and evaluating all parts (tires, dampers, etc.), but also has experience in ADAS evaluation including automatic driving.
He drove around the world as a test driver for a major OEM with the highest driving rank.
He was responsible for the workmanship of development vehicles as an evaluator of the achievement of development vehicle targets, and introduced many models to the market.
As a driving instructor, he has trained over 100 test drivers in total for major OEMs and in his current position.
Blue Sky Technology is a unique consulting and engineering services firm specializing in automotive electrification and related technologies, with a majority of its staff having worked in the automotive industry for 20 to 30 years.
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