ACC

ACC (Adaptive Cruise Control) is an Advanced Driver Assistance System (ADAS) that integrates conventional cruise control with automated longitudinal distance regulation. Whether cruising at highway speeds or crawling in heavy traffic, the ACC system actively monitors traffic conditions ahead via on-board sensors and automatically adjusts the vehicle's speed to maintain a driver-preset safe distance from the lead vehicle, effectively reducing driver fatigue during long-distance journeys and stop-and-go commutes.

Core Technical Architecture and Operating Principles

An ACC system primarily comprises environmental perception sensors (such as millimetre-wave radar, LiDAR, or forward-facing monocular/binocular cameras), an Electronic Control Unit (ECU), and powertrain and braking actuators (engine management system, transmission control unit, and Electronic Stability Programme / ESP).

Multi-Source Environmental Perception & Target Tracking: 

The front-mounted millimetre-wave radar or windscreen-mounted camera continuously detects the relative distance, relative speed, and azimuth angle to the vehicle ahead in real time at high frequencies. The ECU processes this dynamic telemetry via built-in algorithms to lock onto the target vehicle ahead and establish a safe following profile. 

Automated Longitudinal Powertrain & Braking Intervention: 

When the system detects the vehicle ahead slowing down or another vehicle cutting into the lane, it commands the engine management system to ease off the throttle or actively engages the hydraulic brakes to decelerate smoothly. Once the road ahead clears or the lead vehicle accelerates, the system modulates powertrain output to smoothly bring the vehicle back up to the preset cruising speed. Modern Full-Speed ACC systems also feature Stop & Go functionality, allowing the vehicle to come to a complete halt in heavy city traffic and automatically resume moving off when the car in front starts moving.

Safety Guidelines and Physical Limitations 

Prohibiting Misuse as Autonomous Driving (Never Treat ACC as Fully Autonomous):

ACC is strictly a driver assistance feature. Its sensors have inherent physical limitations and potential response delays when encountering stationary obstacles (such as illegally parked vehicles, traffic cones, or crossing pedestrians and animals). Drivers must never rely blindly on ACC or drive distracted in heavy downpours, dense fog, on open roads with cross traffic, or at complex urban junctions. Drivers must keep both hands on the steering wheel at all times, maintaining full vehicle control and ultimate responsibility. 

Sensor Calibration & Extreme Weather Limits: 

Millimetre-wave radar sensors and windscreen cameras are extremely sensitive to surface cleanliness and mounting alignment. Never attempt to engage ACC if the radar sensor or windscreen camera area is obstructed by mud, heavy dirt, grime, or non-compliant solar window tinting film. Following any front-end collision repair, the system must not be used without recalibration using professional alignment equipment, ensuring the precise field of view of the perception hardware to prevent rear-end collisions caused by signal attenuation or detection errors.