Autonomous Driving and ADAS

Types and roles of sensors in ADAS (advanced driving support system)

For ADAS (Advanced Driver Assistance System), the system must recognize the surrounding environment such as the moving objects around the vehicle and the road shape. A sensor for recognizing the external environment is called an "external sensor". The development of sensing technology leads to the development of AD ( Autonomous Driving ) as well as ADAS.
In addition, in order to accurately recognize the environment around the vehicle, we are developing not only one sensor but also a so-called sensor fusion technology that combines various types of external sensors.

1. Types of sensors used in ADAS

The sensors used for ADAS are roughly classified as follows for each information that can be measured.

· Image data: Camera
. Distance data: riders and millimeter wave radar
· Position data: GPS and odometer
· Speed, acceleration, attitude data: IMU (Inertial Measurement Unit)
​ ​and so on.

In this page, we will explain the cameras and radars that detect the circumstances of those sensors. And also about sensor fusion technology combining multiple sensors.

2. Role played by radar in ADAS

For the function of ADAS (advanced driving support system) using radar,

· Inter-vehicle distance control (ACC: Adaptive Cruise Control)
· Front Collision Warning (FCW)
· Collision damage mitigation brake control device (AEBS: Autonomous Emergency Braking System)
. Blind Spot Monitoring (BSM: Blind Spot Monitoring)
. Parking assist (PA)

Details about each function are explained in introduction of ADAS function.
Radars installed in automobiles include short range radar, long range radar, laser radar, ultrasonic radar, etc. Each has its own characteristics.

3. Types of radars for ADAS

3-1. Laser radar (rider)

Laser radar is a remote sensing technology that uses light to measure the scattered light with respect to laser irradiation that emits pulsed light, and analyzes the distance to objects at long distances and the nature of the object. In Japanese it is called "(LIDAR)". In the LiDAR, the pulsed laser beam changes its direction with an internal rotating mirror and scans the peripheral area in a fan shape. The emitted laser light is reflected when it strikes the object, and the reflected light is recognized by the light receiving part of the scanner. Major uses are the measurement of the distance to the obstacle ahead, the recognition of the shape of the road by the curb and the white line recognition using the reflectance.

3-2. Millimeter wave radar

Besides laser radar, millimeter wave radar is available as a sensor for measuring the relative distance to stationary and moving objects around the vehicle. Sensors using millimeter waves have longer detection distance compared with sensors using lasers, can directly perform rain weather performance / performance with fog / snow (all weather) and relative speed, and predict motion performance of preceding vehicles It is characterized by being excellent. Moreover, the antenna diameter is small with respect to the required angular resolution (antenna beam width), and it is excellent in mountability to vehicles. Millimeter wave radar is mainly developed as a long range radar (detection performance of 150 m or more), and products are being developed by each company as a sensor to realize functions such as ACC.

Basically, legal technical requirements for in-vehicle millimeter wave radar are as follows.
(1) Radio frequency band: 76 GHz band
(2) Antenna power: 10 mW or less
(3) Aerial combat gain: 40 dB or less
(4) Specified frequency bandwidth: Within 1 GHz

4. In-vehicle camera in ADAS

In-vehicle cameras have been spreading as drive recorders, back monitors, and other view cameras that save records during driving and assist the driver's blind spot. In recent years, Image Recognition technology has developed, and it has become a role as a sensing camera to detect road signs and pedestrians, etc. from acquired images, issue a warning to the driver, and control the operation of cars. With this, cameras play an important role in ADAS.

The in-vehicle camera used in ADAS has the following uses.
· Function as surrounding visibility assistance system: Around view · monitor, the driver can check the blind spot of the car with images,
. Lateral side obstacle alarm at lane change etc.
· Parking assistance by rear image
· Detect lane markers on road with monocular camera
· Stereo camera detects forward obstacles and predecessors
· Recognition of road signs such as speed indication
· Pedestrian detection · Collision warning
· Driver like drive recorder · Automobile monitoring
· Driver monitoring technology

For details of the camera, please check "On-vehicle camera in ADAS (Advanced Driving Support System)".

5. Types of in-vehicle cameras for ADAS

In-vehicle cameras are classified by image sensor (image sensor) and classified by camera type.

5-1. Classification by image sensor

Image sensors are classified into CCD (Charge-Coupled Device) format and CMOS (Complementary Metal-Oxide Semiconductor) format.
CCD is a type of image sensor widely used for video cameras, digital cameras, etc. When converting a photographed image into an electric signal, data is transferred by using a circuit element called a charge coupled device in order to read the charge generated from light by the light receiving element. CCD has relatively higher sensitivity compared to other image pickup devices, and has less noise. In the past, car-mounted cameras for automobiles often used lower cost CMOS than CCDs, but cases using CCD formats with high Image Recognition precision also increased. Depending on cost and performance, the appropriate format is chosen.

5-2. Classification by installation method

5-2-1. Monocular Camera (Mono Camera)
A monocular camera is the one that literally functions with one camera lens.
Distance measurement is calculated from the pixel position in the vertical direction of the recognized image coordinates, but the error tends to be large. The main advantage is that it can be installed at low cost and the degree of freedom of the installation place is high. It also makes calibration easy. The downside is that the objects to be recognized are limited. For concrete purposes, it is used for warning function, crosswalk recognition, etc. for drivers by recognizing traffic signs such as white line recognition and limit speed for lane keeping purpose.
5-2-2. Stereo camera
A stereo camera is an object that measures objects with two cameras like a human eye, and its parallax makes it possible to measure distances with high institution. Three-dimensional objects can be detected, so you can measure distance and lateral position to various objects such as pedestrians, bicycles, vehicles with high accuracy. Although the information detected in this way can be used variously, it is a disadvantage that calibration is difficult and the amount of calculation increases. It is used as a specific application when recognizing vehicles and pedestrians.

6. Sensor Fusion

Sensor Fusion is a technology that combines information from multiple sensors such as the camera, radar, and LiDAR introduced above so that the surrounding environment can be more clearly grasped. This is a technology required for realizing a more reliable safety function and a more effective autonomous operation system.
Sensor fusion can be associated with any type of sensor. A typical example is the integration of information provided by front camera and front radar. Cameras that function by optical detection can cause problems in situations such as rain, thick fog, strong sunlight, lightless conditions, but they provide high reliability in color recognition, such as road signs. Even with low resolution radar is useful for distance detection and is not affected by environmental conditions. By compensating for the advantages of the sensors in this way, it becomes possible for the system to grasp the surrounding situation more accurately.

6-1-1 ACC (Adaptive Cruise Control)

ACC will speed up to the set speed if the field of sight while driving is good and the distance between the car and the preceding car is sufficient. Likewise, if the distance to the previous car is too close, it will decelerate. The cruise control system of the vehicle reads the surrounding situation with sensors and cameras and maintains the proper vehicle speed.

6-1-2. AEBS (Advanced Emergency Braking System: Collision Damage Reduction Braking Control Device)

It is a system that controls the brake at the moment when a collision with a forward vehicle is detected using a sensor and a camera.

7. ZMP sensor field products

Various sensors available for ADAS development are available for ZMP. We also introduce handling sensors.

7-1. Acceleration sensor

Body Motion: Motion capture system capable of measuring motion of whole body using IMU-Z2

9 axis motion sensor IMU - Z2: 9-axis motion sensor that can be measured wirelessly and wired

6 Axis waterproof motion sensor IMU - Z Cube : 最大400Gの加速度計測可能な小型6軸モーションセンサー

7-2. GPS sensor

Position-Z: GPS capable of outputting CAN · Integrated position sensor with atmospheric pressure

Position & Motion: Sensor package capable of simultaneous measurement of vehicle position, behavior and environment

RTK Position-Z: Position sensor capable of position measurement with centi-order using RTK

7-3. Biosensor

Wearable heart rate sensor: 13 grams continuous 7-day data measurable heart rate sensor

ECG 2: Approximately 15 g, an electrocardiograph that is compact and lightweight and enables wireless measurement

BR 8: 8-channel wireless brain wave sensor BR 8

BR32S: 32-channel wireless brain wave sensor BR32S

7-4. LiDAR

Konica Minolta 3D-LiDAR: LiDAR capable of wide scans of up to 24 layers, horizontal angle of view up to 120 °

8. ADAS Camera Link

ZMP provides a stereo camera unit that can be used for ADAS development.

Stereo camera unit RoboVision 2s: Stereo camera unit capable of long-time image measurement, parallax image acquisition, object detection, etc.

Front-following compliant unit RoboVision 2s CarTrack package: Package with Front Tracking Vehicle Following Function Utilizing Road Surface Detection Algorithm

ADAS / Stereo camera unit for Autonomous Driving RoboVision 3: Up to 150 m, Quad camera unit of 2 eye × 2 corresponding to viewing angle 110 °

9. Inquiries, document request

For inquiries on products and information request, please contact us below.