Positioning of HMI (Human Machine Interface) in ADAS development

In ADAS (Advanced DrivervAssistance Systems), human and in-vehicle systems jointly drive cars. Therefore people and cars need to form a smooth communication. Therefore, in designing and developing ADAS, the concept of HMI (Human Machine Interface) is important. HMI is a protocol that human beings and machines communicate intention and information.

1.HMI determines the difference between ADAS and Autonomous Driving

ADAS is a support system for human beings driving a car, and Autonomous Driving is a concept that automobiles run autonomously. It is in the point that whether the subject of driving is a human or a system determines the difference between Autonomous Driving classified into ADAS which is Autonomous Driving level 2 and level 3 or higher. Because the subject of driving is human, ADAS must accurately inform the driver of the state of the car and the necessary operation. On the other hand, in Autonomous Driving above level 3, the subject of the operation becomes the system, and as the level goes up, the number of elements that the car conveys complicated information on driving operation to the driver decreases. HMI design is exactly an important concept unique to ADAS.

2. Human-to-car information transmission in ADAS is based on the definition of Human Factors

In order to study HMI elements in ADAS it is important to define Human factors which are synonymous with ergonomics in a broad sense. For example, it is necessary to define the operation such as steering wheel and brake pedal so that the operation of a car when driving a car can be safely and economically operated. When the machine (car) detects the defined human (driver) 's behavior, the command transmission from human to machine is done.

3. Cars to human communication in HMI

 逆にマシンからヒトに伝達する場合は、視覚、聴覚、触覚などを介して伝達します。
In order to make the information transmitted from the in-vehicle system misunderstand or confuse human driving behavior, accurately recognize it without giving a negative influence and make effective use of ADAS function, it is necessary to use an interface such as audiovisual information. Attention and ingenuity are necessary for its design.

4. Interface design of HMI

When communicating information from the ADAS system to the driver, it is vital to design the most reasonable and easy-to-understand visual and audible indication that attention is paid to sensory modalities such as visual, auditory, etc., according to its contents and characteristics. A clear message is indicated by the physical characteristics such as the size and color of the visual indication, sound pressure and frequency of the auditory indication.
HMI exchanges information between people and machines via equipment and software. In the case of a car, it corresponds to steering, accelerator, brake, various instruments indicating the state of a car, etc. which the driver operates when driving.

Originally automobile instruments were mostly simple mechanical type such as speedometer, tachometer, direction indicator, various warning lights. However, as automotive electronics have progressed, it became necessary to tell drivers more information, such as displaying surrounding conditions on a car navigation monitor.

Especially in the HMI design of ADAS, the driver must understand the information transmitted from the automobile system correctly so as not to negatively affect the driving operation. It is important to consider the characteristics of information and to adopt visual and auditory senses suitable for it.

5. Classification of transmission information

The information transmitted from the ADAS system to the driver can be classified into the following three levels according to its urgency and severity.
 ・情報供給:通常の交通状況や道路環境を伝達する。
 ・注意喚起:衝突の危険性が高まった際に、注意を喚起する。
 ・警報:衝突の危険性が一定以上高まった際に、回避操作の指示をする。

6. Points to be aware of information transmission method

For example, when designing collision prevention functions such as FCW and ABS, the driver must correctly understand the degree of urgency to collision and the meaning of information based on the distance to the preceding vehicle and the speed of the vehicle. Based on the information provided, it is necessary to decide visual and auditory indication methods according to the urgency and importance of the information so that the driver can properly control the brake pedal and steer.

Let's consider the case where the ADAS system notifies the driver of the information where the driver can not directly confirm the blind spots during operation. If the system does not accurately inform the driver of the intention by visual indication etc., it will lead to misunderstanding and confusion of the driver and induce dangerous driving behavior such as unnecessary sudden braking instead of reducing accidents.

If you do not decide the physical characteristics of audiovisual display according to severity or urgency in this way, there is a danger of erroneously reading the urgency up to the occurrence of the accident and the intention of the transmission information, and erroneous operation of the brake pedal etc.

In a situation where there is no time such as a collision of a car, because there is a limited time to view the visual indication, it is possible to instantly notify the information by a signal sound and cause a proper driving behavior instantaneously. In this way, we will endeavor to adopt a display format that severity and urgency of situation are appropriately transmitted to HMI.

7. HMI with proficiency and age-conscious attention

Collision and other traffic accidents are not frequently experienced by drivers in daily driving and the degree of responsiveness to emergency situations is never high. It may be impossible to know how the ADAS system operates and communicates in situations where compliance is not required. Even with drivers without such prior knowledge of emergency, the HMI is required to design that can understand and move to action immediately.

When designing the HMI (Human Machine Interface) of ADAS (Advanced Driver Assistance System), it is necessary to consider the influence of the age of the driver. Especially for elderly people, the amount and speed of processing information during driving tend to be lower than when they were young. Therefore, it is necessary to limit the amount of information to be presented at once, or to adopt a transmission method according to the degree of severity or urgency of information. Analytics and research are proceeding with automobile manufacturers, OEMs, etc. for HMI implementation in this way.

8. ADAS HMI related information

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