function, structure, operation of radar sensor system (Radar Sensor)

1. Radar sensor system overview

1. Blind spot monitor (BSM) overview

The blind spot monitor (BSM) determines the distance between a vehicle behind and the own vehicle using a radar sensor when changing the lane. Based on this information and the own vehicle information (vehicle speed, yaw rate, turn signal, etc.), it alerts the driver of a vehicle behind getting close or a vehicle running in a blind spot. The alert to the driver is performed by the illumination or flashing of the blind spot indicators in the right and left outside rearview mirrors.

2. Rear cross traffic alert (RCTA) overview

The rear cross traffic alert (RCTA) is a function to alert the driver if a radar sensor detects a vehicle getting close from behind when starting to move backward from a parked state. The driver is alerted by flashing the blind spot indicator in the right or left outside rearview mirror and sounding the instrument panel cluster alarm.

3. System structure

The following 2 functions are integrated in the radar sensor system.

1) Blind spot monitor (BSM)

A function that informs the driver of the presence of vehicles approaching from behind and vehicles behind running in a blind spot when running on a multi-lane road, and it warns the driver of a risk of minor collision when changing the lane

2) Rear cross traffic alert (RCTA)

A function that informs the driver of the presence of vehicles approaching from behind and warns that there is a risk of minor collision when starting to move backward from the parking lot.

Warning

The purpose of the blind spot monitor (BSM) is to assist driving operation when the lave change is performed. This device does not aid driving without looking behind carefully. It is necessary not to overly trust the system but to keep in mind safe driving.
The purpose of the rear cross traffic alert (RCTA) is to aid the driving operation when starting to move backward. This device does not aid driving without looking behind carefully. It is necessary not to overly trust the system but to keep in mind safe driving.

System schematic

Radar sensor input/output diagram

2. Blind spot monitor (BSM)

1. System activation

When the power mode (models with passive entry and start system) or the ignition switch (except models with passive entry and start system) is turned ON, the blind spot monitor (BSM) function is turned ON.

2. System OFF setting

Using the MID mode switch of the steering wheel, the blind spot monitor (BSM) function can be OFF by selecting Disable from the multi-information display settings in the instrument panel.

Note

The blind spot monitor (BSM) function is always reset to Enabled (ON) every time the ignition switch is turned ON.
when towing another vehicle, turn OFF the blind spot monitor (BSM) function. when towing another vehicle, the blind spot monitor (BSM) may not function normally because the radar wave irradiation cannot be performed.

MID mode switch

Legend

MID mode L switch
MID mode confirm switch
MID mode R switch

Multi-Information Display

The BSM OFF indicator light in the instrument panel cluster illuminates while the blind spot monitor (BSM) function is set to Disable (OFF).

BSM OFF indicator light

3. System operation

If a vehicle behind runs within the detection range of the radar sensor while the own vehicle is running at the predetermined speed or higher, or if the radar sensor determines that the own vehicle may collide with a vehicle behind, the blind spot indicator, which is on the outside rear view mirror on the lane side where a vehicle behind is detected, illuminates or flashes. The warning by the blind spot monitor (BSM) is divided into two steps, the first warning performed when detecting a vehicle behind and the second warning performed when the driver is trying to change lanes.

Legend

Blind spot indicator

1) Blind spot monitor (BSM) operating conditions

It operates if all the following conditions are met.

The Power mode (models with passive entry and start system) or the ignition switch (except models with passive entry and start system) is turned ON.
The blind spot monitor (BSM) function is ON.
The vehicle speed is 15 km/h {9 mph} or more.
The shift lever or selector lever is in a position other than the R position.

2) 1st warning

When a vehicle running on the right or left adjacent lane is detected in the range of maximum 55 m from the rear step bumper while running at a vehicle speed of 15 km/h {9 mph} or more, the outside rearview mirror blind spot indicator on the lane side where the vehicle is detected illuminates.

Note

When 2 vehicles are getting close to the own vehicle from rear right and left lanes at the same time, both blind spot indicators of the right and left outside rearview mirrors illuminate.
When the lane is narrow and the vehicle behind is running in the outer lane, a vehicle two lanes away may be detected.

3) 2nd warning

If the driver operates the turn signal switch to the lane side in order to change the lane where the rear vehicle is detected while the first warning is in operation, the blind spot indicator of the outside rearview mirror on the lane side where the turn signal switch is operated flashes.

4) Detection range

The detection range of vehicles behind for the blind spot monitor (BSM) function can be divided into the following two.

Area A

A range where vehicles running in the driver's blind spot can be detected, 1 m {3 ft} from the rear bumper in the forward direction and 7 m {22 ft} from it in the rearward direction

Area B

A range where a rapidly approaching vehicle can be detected from 7 m {22 ft} to maximum 55 m {180 ft} from the rear step bumper.

Legend

Area A
Area B

Detection range

a: 1.0 m { 3.3 ft }

b: 7.0 m { 23.0 ft }

c: 55.0 m { 180.4 ft }

Note

As the speed difference between the vehicle speed of a vehicle running behind and the own vehicle speed is larger, the distance at which the blind spot indicator alarm is started is longer.

5) Auto alignment function

The auto alignment is a function that automatically corrects the deviation of the vehicle detection range of the radar sensor within a range of ±7.4° while running. Deviations in the vehicle detection range of the radar sensor occur due to improper installation, damage, etc., of the radar sensor and peripheral parts of the radar sensor (such as the radar sensor bracket and rear step bumper). Therefore, the radar sensor corrects the vehicle detection range whenever the vehicle meets the operation conditions of the auto alignment function.

The auto alignment function is activated under the following conditions.

The vehicle speed is 25 km/h {16 mph} or more.
The yaw rate is 0.5 °/sec or less. (The vehicle is going straight.)
There is a guard rail or wall on the side of a road.

Legend

Rear step bumper
Radar sensor (Right)
Reference position (sensor installation position)

Correction range

a: 7.4 °

b: 7.4 °

Note

If it is necessary to correct the vehicle detection range in a range exceeding ± 7.4°, DTC C1106 [99] is set.
If the correction by the auto alignment function is not completed, or if the correction is required in the range where the vehicle detection range of the radar sensor exceeds ±7.4°, the blind spot monitor (BSM) function may not operate normally, such as when the radar sensor detects a vehicle two lanes away instead of a vehicle on the next lane.

6) The blind spot monitor (BSM) does not function normally.

The position or direction of the radar sensor deviates due to the strong impact on the radar sensor or around the radar sensor
The rear step bumper near the radar sensor is deformed or damaged.
Mud, snow, ice, etc., adheres to the radar sensor or around the radar sensor.
Difficulty in detecting a rear obstacle because of bad weather (heavy rain, blizzard, snow, etc.)
The temperature around the radar sensor is high or low.
A vehicle in the adjacent lane is too far from the own vehicle, such as when running on a wide lane or at the end of a lane.
The vehicle is running at a sharp corner or on a continuously curving road or bumpy road.
There is a large speed difference between the own vehicle and a vehicle in the adjacent lane.
There is a vehicle height difference between the own vehicle and a vehicle in the detection area.
A vehicle is continuously running up and down a steep slope
A vehicle is running on a snowy road, or place where there is nothing around.
The battery voltage decreases.
Accessories such as a bicycle carrier are installed to the rear of the vehicle.

7) The radar sensor cannot detect an object.

Small motorcycles, bicycles, or non-vehicle objects such as pedestrians
Vehicles with shapes that do not easily reflect radar waves (sports cars, etc.)
Stationary objects such as guard rails, walls, road signs, and parked vehicles
Oncoming vehicle
A vehicle behind running in the same lane as the own vehicle
A vehicle running in a lane two lanes away from the lane where the own vehicle is running
A vehicle in the adjacent lane that the own vehicle is trying to overtake
The inter-vehicular distance between a vehicle and the own vehicle is small.
A vehicle that is within the detection range of the radar sensor (within the range of Area B) but does not get close to the own vehicle. (The system determines the approaching vehicle based on the detection data of the radar sensor.)
A vehicle behind running for a long time at almost the same speed as the own vehicle.
A vehicle that is still in the detection area when the own vehicle starts moving from a stopped state

8) The blind spot monitor (BSM) operates even when there is no possibility of collision.

A guard rail, road sign, parked vehicle, or other stationary objects are detected.

A tunnel entrance, exit, or a turnout is detected.

The tires are skidding.
A vehicle is turning an intersection in an urban area or a crossing on multiple lanes.