In the modern transportation system, the popularization of automobiles has greatly improved the travel efficiency. However, it has also brought severe challenges to traffic safety. Among them, the frequent occurrence of collisions between vehicles and pedestrians has caused huge losses to people's lives and properties. According to relevant statistical data, the number of casualties caused by vehicles colliding with pedestrians globally each year remains high. This situation highlights the urgency and importance of accurate pedestrian detection during vehicle driving. In this context, radar sensing technology, as an advanced detection method, has gradually emerged in the field of pedestrian detection for automobiles.
Analysis of the Principle of Radar Sensing Technology
The core of radar sensing technology is to use the emission and reception of electromagnetic waves to obtain information about the target object. Its working process is as follows: The radar device emits electromagnetic waves of a specific frequency into the surrounding space. When these electromagnetic waves encounter a target object (such as a pedestrian), they will be reflected. The reflected electromagnetic waves are captured by the radar receiving device. By analyzing parameters such as the time difference and frequency change between the emitted wave and the echo, the radar system can accurately calculate key information such as the distance, speed, and angle of the target object.
Specifically, by measuring the time difference between the emitted wave and the echo, and based on the propagation speed of electromagnetic waves in the air (approximately the speed of light), the distance between the target object and the radar can be calculated using the formula "distance = propagation speed × time difference ÷ 2". The speed information of the target object is obtained based on the Doppler effect. When there is relative motion between the target object and the radar, the frequency of the echo will change. The amount of frequency change is proportional to the speed of the target object. By accurately measuring the frequency change, the speed of the target object can be calculated. For the angle measurement of the target object, the radar system uses the layout of multiple receiving antennas and signal processing algorithms to compare the phase difference or signal intensity difference of the echoes received by different antennas, and then determine the angle of the target object.
Application Mechanism of Radar Sensing in Pedestrian Detection
During the driving process of a vehicle, radar sensing technology plays a key role in pedestrian detection, and its application mechanism covers various complex processes.
Target Recognition and Tracking
The radar system continuously emits electromagnetic waves into the space around the vehicle and receives the reflected echoes. Through complex analysis and processing of the echo signals, advanced algorithms are used to extract and identify the characteristics of the target object, so as to accurately distinguish the pedestrian target from numerous reflection sources. Once the pedestrian is identified, the radar system will activate the tracking program. By real-time monitoring of the changes in parameters such as the distance, speed, and angle of the pedestrian, it can accurately predict and continuously track the movement trajectory of the pedestrian. For example, when a pedestrian is walking in front of the vehicle, the radar can grasp the walking speed and direction of the pedestrian in real-time and predict the possible position of the pedestrian in the next step, providing timely and accurate information for the vehicle's decision-making system.
Real-time Data Transmission and Processing
The pedestrian-related data obtained by radar sensing is transmitted to the central control system of the vehicle at a very high speed. In this process, the stability and timeliness of data transmission are crucial. The central control system of the vehicle is equipped with a high-performance processor that can quickly process and analyze a large amount of radar data. It will integrate and calculate the radar data with the vehicle's own driving status data (such as vehicle speed, driving direction, etc.), comprehensively judge the relative position and movement situation between the vehicle and the pedestrian, and evaluate the collision risk level. For example, when the vehicle is driving at a high speed and the distance from the pedestrian in front is rapidly decreasing, the central control system can quickly analyze the potential collision danger and make corresponding decisions in a timely manner.
Warning and Auxiliary Decision-making Support
Based on the accurate detection of pedestrians and data analysis, when the distance between the vehicle and the pedestrian approaches the danger threshold, the radar sensing system will immediately trigger the warning mechanism. The warning methods usually include visual warnings (such as displaying eye-catching warning icons on the vehicle dashboard) and auditory warnings (emitting sharp alarm sounds) to attract the driver's high attention and remind them to take necessary evasion or braking measures. At the same time, the radar sensing system also provides key data support for the vehicle's assisted driving system to help the assisted driving system make more scientific and reasonable decisions. For example, after receiving the danger information provided by the radar, if the driver fails to respond in time, the automatic emergency braking system (AEB) will automatically activate the braking device to brake the vehicle urgently to avoid the occurrence of a collision accident or reduce the severity of the collision; the adaptive cruise control system (ACC) will also automatically adjust the vehicle's driving speed according to the pedestrian situation detected by the radar to maintain a safe following distance.
Significant Advantages of Radar Sensing for Pedestrian Detection
All-weather and Strong Adaptability Working Ability
Compared with other detection technologies, radar sensing technology demonstrates excellent working performance in various harsh weather conditions (such as heavy rain, dense fog, and snow) and environments with poor lighting conditions (such as at night). The principle is that radar uses electromagnetic waves for detection, and electromagnetic waves are minimally affected by weather and lighting. In heavy rain, although the rain will interfere with the propagation of light, it has little impact on the propagation of electromagnetic waves. The radar can still stably emit and receive electromagnetic waves and accurately detect the position and movement state of pedestrians; in foggy weather, the visibility is extremely low, and visual sensors can hardly work normally. However, due to the characteristic that radar is not affected by fog, it can still clearly sense pedestrian targets in the surrounding environment; at night, the light is dim, and the detection accuracy of the visual system drops significantly, but the radar is not restricted by the lighting conditions and can continuously provide reliable pedestrian detection information for the vehicle. This all-weather and strong adaptability working ability greatly improves the safety of vehicles driving in complex environments.
High-precision Distance and Speed Measurement
Radar sensing technology has extremely high precision in measuring the distance between pedestrians and vehicles and the movement speed of pedestrians. By accurately analyzing the time difference and frequency change between the emitted wave and the echo, the radar can precisely calculate the distance and speed parameters. In practical applications, this high-precision measurement ability plays a decisive role in the safe driving of vehicles. For example, in the complex traffic environment of urban roads, the walking state of pedestrians is changeable. The radar can accurately measure the real-time distance between the vehicle and pedestrians, and the error can be controlled within a very small range. At the same time, it can accurately obtain the walking speed of pedestrians. Based on these high-precision data, the vehicle's control system can more accurately judge the collision risk and formulate reasonable response strategies in advance, such as adjusting the vehicle speed in advance and planning the evasion path, so as to effectively avoid the occurrence of collision accidents.
Excellent Target Detection and Tracking Performance
The radar sensing system can efficiently detect and continuously track multiple targets simultaneously. In a busy traffic scene, there are often many pedestrians, other vehicles, and various obstacles around the vehicle. Relying on its powerful signal processing ability and advanced algorithms, the radar can accurately identify different targets from complex reflected signals and track the movement trajectory of each target in real-time. For example, at a crossroads, pedestrians cross from all directions, and vehicles are also constantly moving. The radar system can clearly distinguish the position and movement state of each pedestrian and track the driving trajectories of multiple vehicles at the same time without the situation of target confusion or loss. This excellent multi-target detection and tracking performance enables the vehicle to comprehensively grasp the dynamic information of the surrounding environment, providing all-round protection for safe driving.
