ACC adaptive cruise additional function
ACC additional function
ACC also has many additional functions, such as lane change assistance, overtaking assistance, curve assistance, stop-and-go and so on. Here is only a very useful function, that is, Stop & Go. Of course, not all cars with ACC function are equipped with stop-and-go function, and there are still many brand cars that do not have this function.
If ACC's car-following function is mainly used for highway driving, then stop-and-go under ACC is mainly used for urban roads. Simply put, the stop-and-go function is still to follow the vehicle in front, but when the vehicle in front stops, the ACC vehicle will also stop, the vehicle in front will move forward again, and the ACC vehicle will automatically accelerate. Stop-and-go can solve the problem of traffic jam or waiting for traffic lights, and alleviate the problem of driving fatigue in complex urban environment, which is the gospel of female drivers:)
Stop-and-go function also has disadvantages. On the one hand, vehicles crawl for 2-3 meters at a speed of 2Km/h before stopping; on the other hand, the distance between parked vehicles is 3.5-4 meters. These shortcomings may be due to safety considerations, and the driving environment abroad may be relatively civilized. In the domestic environment with serious traffic jams, I'm afraid I don't know how many times I was robbed of overtaking. In this case, the feeling of stopping and going should be very bad. In addition to the distance factor, there is also the time factor. Auto-start takes effect in 3 seconds. In the case of traffic jam, it stops for 3 seconds, which increases the probability of traffic jam next to it and intensifies the risk of collision.
What is ACC adaptive cruise?
ACC system is developed on the basis of cruise control device. The difference is that cruise control can only limit the speed, and the steering wheel and brakes also need the driver's control. ACC can better help the driver coordinate the steering wheel and brakes. Constant speed cruise can be regarded as L 1 autopilot, while ACC can be regarded as L2 autopilot.
ACC has two main parameters, speed and distance. If there is no car ahead, you can drive at the expected speed set by the driver, which is equivalent to the constant speed cruise function. If the lane keeps LKA system, you can continue to drive along the current lane. If the car in front is too slow to drive at the expected speed, ACC can keep the expected distance between the two cars set by the driver. When necessary, the vehicle will automatically brake and/or change the speed to maintain the set speed or distance. Under some driving conditions, the driver will be required to take the initiative to brake, and this warning information will be displayed in a sound and visual way.
How to use ACC
First, turn on the ACC function.
All the operating functions of ACC are integrated on the control lever as shown below. Pull the lever towards the driver to turn on the ACC function, and push the lever backward to turn off the ACC function.
Secondly, set the desired vehicle speed.
Pushing the joystick up or down can increase or decrease the expected vehicle speed. Generally, the speed can be set in the range of 30~200Km/h, and it starts at 30Km/h by default, and it can be increased or decreased by 10Km/h (some steps are 5Km/h). Finally, press the set button to save the vehicle speed and display the set speed value on the instrument. By the way, full ACC, you can start at 0Km/h, there is no minimum speed requirement, and it is also a stop & Go) function.
Third, set the desired distance.
The distance between this vehicle and the preceding vehicle can be set to level 4. Just flip the slide switch, and the default distance is level 3. It should be noted that the distance here is not a fixed distance, but a constant time interval, and the final distance depends on the previously set speed. The reason is that levels 1 to 4 represent different response times, which are 1.0s, 1.3s, 1.8s and 2.3s respectively. In fact, the risk of collision lies in your reaction time, and the early reaction of many accidents can be avoided. In general, the suggestion of setting the distance between cars is to set the slope at high speed, because the speed is faster and safety comes first. In urban roads, the slope is set lower and the speed is not fast, while maintaining a good stop-and-go experience.
Finally, we can start ACC.
In addition to the above three settings, there are driver program settings, that is, setting your driving mode. There are comfortable, automatic, sporty, efficient and personalized modes to choose from. Of course, you can also set the volume of the prompt tone.
When your speed exceeds 30Km/h, ACC will start automatically (full-speed ACC can start directly), it will automatically accelerate to the speed you set (if there is no obstacle ahead), and then keep the speed and distance.
Adaptive cruise principle
ACC principle
ACC function mainly uses radar technology, emits millimeter-wave electromagnetic waves through millimeter-wave radar, determines the distance of obstacles by using the time difference of reflected waves of obstacles, and determines the relative speed by using the frequency offset of reflected waves. Millimeter wave radar has a strong ability to penetrate fog, smoke and dust, and has the advantage of all-weather (except rainy days). ACC generally adopts 77GHz long-range radar, and the distance can reach100-200m.
The technical realization of ACC mainly follows the following four steps.
Step 1: Distance measurement
Judge the distance from the vehicle in front. If there is no vehicle (which can be detected by millimeter wave radar within 200m), then the vehicle will start to travel at the set speed.
Step 2: Determine the speed of the vehicle ahead.
The purpose of determining the speed of the vehicle ahead is to obtain the relative speed. Through the distance in the first step, the time required to reach the preceding vehicle can be calculated, which can be compared with the expected distance set by ACC. (what? Compare time and distance? Yes, it echoes the expected distance set by ACC above, and the expected distance is actually the response time)
Step 3: Determine the position of the vehicle in front.
Although the MMW radar has a small field of view, if it detects objects beyond130m, the detection width may exceed three lanes. In addition, in the case of a curve, the radar will judge many cars in different positions ahead.
Step 4: Determine which car to adjust.
The previous step is to determine the vehicle and its location. This step needs to determine to follow the car, which is an important judgment decision and the key to ACC safety. It needs to coordinate with other control units in the vehicle to make a judgment, such as lane recognition unit. In addition, the adjustment here is not only as simple as throttle braking, but also involves more sensor units, such as steering angle, wheel speed and other sensors.
Advantages and problems of ACC adaptive cruise
Advantages and problems of ACC
The original intention of ACC development is to relieve fatigue and improve driving comfort, which is an undoubted advantage. ACC is also a primary function before autonomous driving. Combined with lane keeping LKA, forward collision warning FCW, automatic emergency braking AEB, lane change assistance and other systems, a good semi-automatic driving experience can be obtained. ACC is not only used in high-speed environment, but also its stop-and-go function can be used in urban congestion environment, which is more widely used and plays a more prominent role in assisting human driving.
Although ACC is very powerful, it also has shortcomings. We list some common problems.
Can ACC turn with the car?
In most cases, it should be impossible to turn with the car, and it should be impossible to turn 90 degrees and turn sharply. On the one hand, the limitation of radar detection itself, on the other hand, there is no lane line at the intersection, and the lane keeping function can't work. ACC (actually lane keeping system) can make a small turn for slow turns (such as turnouts) and bends (such as high-speed bends), but for slightly larger bends, the vehicle may misjudge the vehicle and suddenly accelerate or decelerate. Therefore, don't expect ACC to follow the car like a team. As long as you can follow the car on the highway and in the traffic jam in the city, it is already great. In the case of turning, it is better to control it yourself.
Can ACC identify motorcycles or pedestrians?
If there is a traffic jam when you stop and go in the city, even if you do, it is also a car accident. What about pedestrians or motorcycles? Good question. Rover still doesn't understand. It is said to have two functions: pedestrian identification and pedestrian protection. Pedestrian recognition only recognizes not slowing down, and pedestrian protection recognizes braking. These two functions are outside the ACC function. Only ACC cannot recognize pedestrians. For the urban environment, pedestrians jaywalk and electric cars ride to the motorway from time to time, so pay more attention to braking when using ACC.
Is ACC safe?
This is a neutral question and the answer is also neutral. It is because of safety that car companies will open this function to customers, but it is also unsafe. There are many unsafe factors, such as bad weather, insensitivity to congestion judgment, untimely or insufficient braking, wrong judgment to the trailer ahead, etc. At the same time, there are also drivers' own factors, such as not being vigilant when using ACC, and even ignoring ACC alarm. Generally speaking, it is recommended to use ACC when the road conditions are good, and be alert while enjoying comfort. You still can't leave the brake with your right foot. When braking, you should take the initiative to brake. This is the correct posture of ACC:) ACC adaptive cruise additional function What is ACC adaptive cruise? How to use ACC principle of ACC adaptive cruise Advantages and problems of ACC adaptive cruise @20 19