In the current era of continuous innovation in automotive technology, the electronic cruise control system has gradually become an important configuration of modern vehicles. One of the core technologies of this system is radar sensing, which is like the "eyes" of the vehicle, providing the key environmental perception ability for the cruise control function and greatly improving driving safety and comfort.
Principle of Radar Sensing Technology
Radar sensing works based on the principle of electromagnetic wave transmission and reception. The radar sensor on the vehicle emits electromagnetic waves of a specific frequency into the surrounding space. When these electromagnetic waves encounter vehicles, pedestrians, or other obstacles in front, they will be reflected. The radar sensor receives the reflected electromagnetic waves and obtains key information about the target object by analyzing the characteristics of the echo, such as time delay and frequency change. Among them, by measuring the time difference between the transmission and reception of electromagnetic waves, the distance between the target object and the vehicle can be accurately calculated; and by using the Doppler effect, that is, according to the difference between the frequency of the reflected wave and the frequency of the transmitted wave, the relative speed of the target object can be accurately obtained. In addition, by analyzing information such as the received signal strength and phase, the approximate orientation and angle of the target object can also be determined.
Key Roles of Radar Sensing in Cruise Control
Maintaining a Safe Following Distance
In the cruise control system, the primary task of radar sensing is to ensure that the vehicle maintains a safe driving distance from the vehicle in front. After the vehicle activates the cruise control function, the radar sensor continuously monitors the position and speed of the vehicle ahead. Once it detects that the vehicle in front slows down, the radar will quickly transmit this information to the vehicle's control system. The control system accurately calculates the required speed reduction based on the data fed back by the radar and adjusts the engine output power or activates the braking system to make the vehicle decelerate smoothly and maintain the set safe distance from the vehicle in front. For example, when a vehicle is driving on the highway at a speed of 80 kilometers per hour, the cruise control system can maintain a distance of about 50 meters from the vehicle in front with the help of radar sensing, and this distance will be dynamically adjusted according to changes in road conditions and vehicle speed.
Speed Adjustment
Radar sensing can not only control the following distance but also achieve automatic speed adjustment. When there are no vehicles on the road ahead, the vehicle will travel at the preset cruise speed set by the driver. Once the radar detects a vehicle ahead whose speed is lower than the set speed of this vehicle, the cruise control system will gradually reduce the vehicle speed according to the radar data to follow the vehicle safely. When the road is clear, and the vehicle ahead moves away or accelerates to widen the distance, the radar sensing plays a role again, and the system controls the vehicle to gradually accelerate and return to the set cruise speed. This intelligent speed adjustment process eliminates the need for the driver to frequently operate the accelerator and brake, greatly reducing the fatigue of long-distance driving.
Multi-target Recognition and Response
Under complex road conditions, there may be multiple targets around the vehicle at the same time, such as vehicles in different lanes ahead, suddenly appearing pedestrians, or stationary objects by the roadside. Advanced radar sensing technology has powerful multi-target recognition capabilities, which can accurately distinguish and track these targets. For the cruise control system, accurate identification of relevant targets is crucial. For example, when a vehicle is cruising on a multi-lane road, the radar sensor can identify the vehicle in front in the same lane and vehicles in adjacent lanes that may affect driving. If a vehicle in an adjacent lane has the intention to change lanes, the radar can detect it in advance and transmit the information to the system, enabling the vehicle to make corresponding adjustments in advance, such as appropriately reducing the speed or remaining vigilant to avoid potential collision risks.
Types and Characteristics of Radars Applied in Cruise Control
Millimeter-wave Radar
Millimeter-wave radar operates in the millimeter-wave frequency band, and the commonly used operating frequencies at present are 24GHz and 77GHz. It has many advantages. Firstly, the wavelength of millimeter waves is relatively short, which makes the millimeter-wave radar perform excellently in detection accuracy and can accurately measure the distance, speed, and angle of the target object, providing high-resolution data for the cruise control system. Secondly, the millimeter-wave radar has strong adaptability to adverse weather conditions. In rainy, foggy, snowy, and other weather conditions, it can still work stably, effectively ensuring the reliability of the cruise control function in various weather conditions. Moreover, the detection range of the 77GHz millimeter-wave radar is relatively long, reaching up to 150 meters or even farther, which can detect distant targets ahead in advance and leave sufficient time for the vehicle's decision-making and operation. However, the millimeter-wave radar also has certain limitations. Its cost is relatively high, especially for high-performance millimeter-wave radars, which to a certain extent restricts its widespread application in some economy vehicles.
Lidar
Lidar senses the surrounding environment by emitting laser beams and receiving the reflected light. It has extremely high resolution and can construct a very accurate three-dimensional image of the vehicle's surrounding environment. In cruise control, lidar can clearly identify the details of road boundaries, lane lines, and various target objects, providing accurate environmental information for the vehicle. Compared with millimeter-wave radar, lidar has an edge in detection accuracy and target recognition ability, especially in the recognition of stationary objects. However, lidar also faces some challenges. On the one hand, it has relatively strict requirements for the working environment. In adverse weather conditions such as heavy rain and sandstorms, the propagation of laser will be severely affected, resulting in a significant decline in detection performance. On the other hand, the cost of lidar is high. Both the hardware cost and the subsequent data processing cost hinder its large-scale application to a certain extent.
Ultrasonic Radar
Ultrasonic radar is mainly used for short-range detection and is commonly used in the vehicle's parking assistance system and can also play a role in certain scenarios of cruise control. It measures the distance by emitting ultrasonic waves and according to the time when the ultrasonic waves are reflected back. Ultrasonic radar has a low cost and a relatively simple structure, and it has high measurement accuracy within a short distance (usually within a few meters). During cruise control, when the vehicle needs to deal with sudden short-range situations, such as a sudden short-range obstacle ahead, the ultrasonic radar can react quickly and provide timely warning information for the vehicle. However, due to its limited detection range and insufficient detection ability for distant targets in high-speed driving scenarios, in the cruise control system, it is usually used as an auxiliary sensor for millimeter-wave radar and lidar.
As the core support of the automotive electronic cruise control system, radar sensing technology plays an irreplaceable role in improving driving safety and comfort. Despite facing some challenges, with the progress of technology, radar sensing is constantly being optimized and will continue to play an important role in the field of future intelligent vehicles, laying a solid foundation for higher levels of autonomous driving.
