Adaptive Cruise Control (ACC) System Description - Overview (2014 2015)
The adaptive cruise control (ACC) system improves upon the regular cruise control system by using the ACC system to maintain a safe distance behind the vehicle in front by automatically slowing down or speeding up (to the set speed).
ACC Unit
The ACC unit obtains information from external sensors and switches that are connected to their respective control units.
ACC Operation Range:
- The vehicle must be travelling between 25-90 mph (40-145 km/h)
- The vehicle must be 1.0-2.0 seconds behind the vehicle in front
- Maximum deceleration is 0.30 G
Millimeter Wave Radar
The millimeter wave radar is installed on the main bracket attached to the front bulkhead. The main bracket allows the radar angle to be adjusted ±3 degrees vertically by moving the main bracket adjusters.
The millimeter wave radar has these functions:
Basic distance function
The millimeter wave radar radiates 76-77 GHz radar waves up to a range of 393 ft (120 m) ahead and 16 degrees horizontally and 3.9 degrees vertically, while simultaneously receiving the reflected waves. In doing so, the system calculates the distance to the vehicle ahead, the relative speed (the difference in speed between the two vehicles), and its position. This data is then sent to the ACC unit.
Aiming function
The millimeter wave radar has a horizontal auto-aiming function range of ±3 degrees and is directed by the ACC unit.
Self-Diagnosis function
The millimeter wave radar has a self-diagnostic function, and it sends this information to the ACC unit
Sensitivity-Lowering detection function
The millimeter wave radar has a self-diagnostic function, and it sends this information to the ACC unit.
Adjuster-Misalignment detection function
When the millimeter wave radar adjuster is misalignment by more than ±5 degrees, the detection function signals the misalignment to the ACC unit.
Operation Criteria
- When there is no vehicle ahead, the ACC maintains the set speed.
- When there is a vehicle ahead, the ACC maintains a set distance but will not exceed the set speed.
- If the vehicle ahead pulls over out of the way, the ACC accelerates the vehicle to the set speed and maintains that speed.
- The ACC measures the distance from the vehicle ahead using the millimeter wave radar, and it determines if the target vehicle driving ahead is in the same lane by using inputs from the PCM and the VSA modulator-control unit.
- If the ACC detects a slow vehicle and the distance to the vehicle ahead is closing, the vehicle speed is reduced primarily by closing the throttle, and additional slowing is accomplished by using the brakes. If the vehicle ahead is too close, an alarm sounds.
- If a slower vehicle ahead accelerates, the throttle is opened to accelerate the vehicle (up to the set speed.) to maintain the following distance.
Basic ACC Pattern
- Radar detection: Max. 393 ft (120 m) ahead in a 16 degree field of view
- Vehicle operating speed: 25-90 mph (40-145 km/h)