KR100892539B1 - Vehicle distance control method - Google Patents

Abstract

The present invention sets the target distance and target acceleration by using the distance between the preceding vehicle and the current vehicle, the vehicle speed, the time gap, the distance coefficient and the speed coefficient, and adjusts the driving force or braking force of the current vehicle accordingly. As the distance control method, distance coefficient and speed coefficient are selected so that the main pole of the distance or vehicle speed transfer function exists on the negative real axis, and the selected distance coefficient and speed coefficient are substituted into the transfer function, and time gap Since the output of the transfer function is selected as the minimum value to prevent the overshoot from occurring, the deviation of control is prevented even in the cluster vehicle matrix, and a separate controller is not necessary to alleviate the collision, and it is easy to select an unknown control coefficient. To be accurate.

Description

{Adaptive Cruise Control Method For A Vehicle}

The present invention relates to a vehicle inter-vehicle distance control method for capturing a preceding vehicle with a radar to measure a relative distance and a relative speed, and accordingly to control the driving unit and the braking unit of the vehicle so that the vehicle can travel at an appropriate distance and an appropriate speed. will be.

Depending on the driving environment of the vehicle or the driver's inclination, it may not be possible to alternate between the acceleration paddles and the brake paddles. This is especially the case when driving at a certain distance from the preceding vehicle, such as a congestion section or a high-speed section. Therefore, in recent years, the vehicle is equipped with an inter-vehicle distance control system so that the driver can drive while maintaining a safe distance with the preceding vehicle without stepping on the paddle.

Conventional inter-vehicle distance control method is a cruise control (Cruise Control), it was possible to simply maintain a constant speed without considering the relationship with the preceding vehicle, but in recent years, the relationship with the preceding vehicle is improved by repeating the driving or braking properly. In consideration of this, an adaptive cruise control (ACC) method is used that enables more active control.

The adaptive cruise control inter-vehicle distance control method measures the speed and the inter-vehicle distance of the preceding vehicle from the radar provided in front of the vehicle, and selectively operates the driving unit or the braking unit to obtain an appropriate speed by comparing it with the speed of the current vehicle. to be. In this case, the driver needs only steering operation, and the acceleration / deceleration is automatically controlled in the relationship with the preceding vehicle by the controller. In this case, the measurement distance is generally set by using the distance between the preceding vehicle and the current vehicle, the vehicle speed, and the undefined coefficient by using the time gap, the distance coefficient, and the speed coefficient. Adjust the driving force or braking force.

Referring to FIG. 1, a general inter-vehicle distance control method is performed. After measuring the speed and the inter-vehicle distance of the preceding vehicle from the radar in front of the vehicle, the controller generates a driving or braking signal. The throttle valve of the drive engine or the brake of the brake is selectively operated to adjust the distance or speed with the preceding vehicle.

However, in the conventional method of controlling a distance between vehicles, when a group of vehicles are moved in line, a change in the distance between the vehicle and the vehicle speed is propagated to the rear vehicle when the preceding vehicle suddenly stops. In this case, the entire cluster vehicle loses control and the rear vehicle may crash. Referring to FIG. 2, the case of Steady-State Following is shown, and the steady state following means that there is almost no difference in speed between vehicles. In this case, when the prediction experiment is conducted by using the conventional inter-vehicle distance control method, the difference between the inter-vehicle distance and the speed of the vehicle propagates to the rear vehicle gradually and eventually collides with the front vehicle because it is impossible to control one day among the rear vehicles. You can see that is generated. This is because the conventional inter-vehicle distance control method only considers the relationship between the current vehicle and the preceding vehicle and does not consider the entire cluster driving in consideration of control.

The conventional inter-vehicle distance control method has a safety problem because it does not consider the entire group driving, and a separate controller is required to alleviate such collisions, and relying on simple tuning when tuning the unknown coefficients such as distance or speed coefficient There is a problem that takes a long time for proper control.

The present invention has been proposed in order to solve such a problem, and has the purpose of ensuring the safety when driving the vehicle cluster, and to obtain the unknown coefficient of the correct controller in a short time.

In order to achieve the above object, a method for controlling a distance between vehicles according to the present invention may be achieved by using a distance between a preceding vehicle and a current vehicle, a vehicle speed, a time gap, a distance coefficient, and a speed coefficient. Setting and adjust the driving or braking force of the current vehicle accordingly,

The distance coefficient and the speed coefficient are selected under the condition that the main pole of the inter-vehicle distance or the vehicle speed transfer function exists on the real axis, and the time gap is set so that the output of the transfer function in which the selected distance coefficient and the speed coefficient are substituted does not cause an overshoot. Is selected as the minimum value.

The selected distance coefficient, speed coefficient, and time gap are composed of a data map, and a time gap controller is provided in a vehicle interior, and the corresponding distance and speed coefficients are derived from the data map when adjusting the time gap of the occupant. It is desirable to set the target acceleration.

Each of the transfer functions represents a propagation tendency of the inter-vehicle distance or vehicle speed by inputting the preceding vehicle and the output of the current vehicle, and the denominator and the respective coefficients are preferably composed of a time gap, a distance coefficient, and a speed coefficient.

According to the method for controlling the inter-vehicle distance of the vehicle having the above-described configuration, the rear-vehicle does not have large propagation of the change in the inter-vehicle distance and the speed of the vehicle, and the collision of the rear-vehicle is prevented even when the vehicle is clustered. In addition, a separate controller is not required to alleviate the collision, and selection of control unknowns becomes easy and accurate.

Hereinafter, a method for controlling a distance between vehicles according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 3 shows each vehicle in order to express the driving element as a transfer function when the vehicle is clustered. The current vehicle is vehicle (i). vehicle (i-1) is a preceding vehicle and vehicle (i + 1) is a rear vehicle. C is the vehicle distance, x is the vehicle position, v is the vehicle speed, and a is the vehicle acceleration.

In general, the distance and relative speed of the current vehicle are defined by Equation 1, and the target distance and acceleration are defined by Equation 2. The vehicle model is defined by Equation 3 as an acceleration characteristic of the vehicle with respect to the target acceleration. In addition, q of Formula 3 is experimentally obtained as a response characteristic (time constant) to the acceleration change of the vehicle.

[Equation 1]

[Formula 2]

[Equation 3]

,

,

In general, the transfer function of the inter-vehicle distance in Laplace transform is summarized as in Equation 4 above. Where k1 is the distance coefficient, k2 is the velocity coefficient, and τ is the time gap. The inter-vehicle distance transfer function inputs the distance of the preceding vehicle (ie, the vehicle preceding the preceding vehicle) as an input, and outputs the distance of the current vehicle (ie, the preceding vehicle) as an output. Represents a trend. Looking at Equation 2, the target acceleration a is tuned by k1 and k2, and the target distance is determined by τ. Since the target inter-vehicle distance affects the target acceleration, k1, k2, and τ can be considered as determinants of the target acceleration.

[Equation 4]

For safer control of the vehicle, not only the distance between vehicles but also the transfer function of the vehicle speed is required. Therefore, it is necessary to derive the transfer function from Equations 1 to 3. Equations 5 for x are derived from Equations 1 to 3, and Equations 6 for v are obtained from Equations 5. To sum up Equation 6, Equation 7, which is the transfer function of the vehicle speed, is obtained. The vehicle speed transfer function of Equation 7 represents the propagation trend of the vehicle speed by inputting the vehicle speed of the preceding vehicle and outputting the vehicle speed of the current vehicle.

[Equation 5]

[Equation 6]

[Formula 7]

Comparing Equation 4 and Equation 7, each transfer function represents a propagation tendency of the distance or vehicle speed by inputting the preceding vehicle and outputting the current vehicle, and the time gap and distance are represented by the coefficients of the denominator and the numerator. It is composed of the coefficient and the speed coefficient, and it can be seen that the transfer function of the vehicle distance and the transfer function of the vehicle speed are the same. As a result, both distance and speed can be controlled by using one representative transfer function.

In controlling the inter-vehicle distance and vehicle speed of the current vehicle, it is very important to ensure that the vehicle is inside the controllable area in such a case, in consideration of the sudden stopping of the group vehicle matrix or the preceding vehicle. This means that there is a need to prevent overshooting, so if the dominant pole of the transfer function is located on the negative real axis, the system will be stabilized and no overshooting will occur. If left underneath, the inter-vehicle distance and vehicle speed can reliably reach the desired target without overshooting. The transfer function is divided into G1 and G2 as shown in Equation 8, and each denominator includes q, which is a time constant, and k1 and k2, which are unknown coefficients, as variables. Since q is a known value, if k1 and k2 are obtained on the condition that the overshooting does not occur, a range of k1 and k2 in a predetermined range is derived.

The condition that the main pole of the transfer function of Equation 8 is on the negative real axis can be obtained as shown in Equation 9 by Cartano's third-order equation solution using the denominator.

Equation 8

[Equation 9]

Fig. 4 is a graph showing the ranges of k1 and k2 satisfying the above conditions, where Area (1) is an area having a positive pole when the Routh determination method is used, and Area (2) is an area where two main poles are empty. Area (3) is a negative real root of all major poles, and Area (4) is a negative real root of one major pole. Overshooting when k1 and k2 in the ranges (3) and (4) are selected. This is avoided. For example, when k1 is 0.1, if k2 is -0.5, overshooting occurs, but if -1, overshooting does not occur and the current vehicle does not collide with the preceding vehicle. Of course, the value of τ also needs to be considered.

When k1 and k2 satisfy the above conditions, overshooting may also be determined based on the value of τ. The determination of τ can be found by looking at the step response of G (s) for each k1 and k2 combination. After substituting a combination of k1 and k2 within the ranges of Areas (3) and (4) into G (s), a minimum τ in which no overshooting occurs in each unit step response can be obtained through continuous simulation. have.

FIG. 5 is a three-dimensional graph showing correlations with x-axis as k1, y-axis as k2 and z-axis as τ. Looking at this, the x-y plane exists only in the areas of the areas (3) and (4) as k1 and k2, and τ also exists on the z-axis only in the areas where k1 and k2 exist.

Briefly looking at the above process, the distance control method of the vehicle finally needs a target distance and acceleration, and to obtain this, k1 (distance coefficient), k2 (speed coefficient) and τ (time gap) values are required. . Since the current vehicle does not collide with the preceding vehicle unless the output of the inter-vehicle transfer function or vehicle speed transfer function is overshooted, the critical pole must be on the negative real axis, and k1 and k2 satisfying the condition are obtained. Substitute the transfer function to find the minimum value of τ that will not overshoot the actual step function response. The obtained k1, k2, and τ values are substituted into Equation 2 as the measured values to derive the target inter-vehicle distance and the target acceleration, and send a signal to the driving unit or the braking unit of the vehicle.

6 is a data map showing the correlation of k1, k2 and τ derived by the above scheme. For example, when τ is 1.12, k1 is 0.20 and k2 is -1.10. In this case, when the occupant of the vehicle adjusts the τ value, the k1 and k2 values are derived, and the inter-vehicle distance can be controlled in this manner.

While the invention has been shown and described with respect to particular embodiments, it will be appreciated that the invention can be variously modified and modified without departing from the spirit or scope of the invention as provided by the following claims. It will be apparent to those of ordinary skill in Esau.

1 is a conceptual diagram of a distance control method according to a conventional embodiment.

2 is a view showing a problem of the inter-vehicle distance control method according to an embodiment of the prior art.

3 is a conceptual diagram for configuring a transfer function of the inter-vehicle distance control method according to an embodiment of the present invention.

4 is a graph showing a range of selection of the distance coefficient k1 and the speed coefficient k2 of the inter-vehicle distance control method according to an embodiment of the present invention.

5 is a graph showing the relationship between the distance coefficient k1, the speed coefficient k2 and the time gap τ of the inter-vehicle distance control method according to an embodiment of the present invention.

6 is a data map of the inter-vehicle distance control method according to an embodiment of the present invention.

Claims (3)

Control the inter-vehicle distance of the vehicle that sets the target vehicle distance and the target acceleration by using the vehicle distance, vehicle speed, time gap, distance coefficient and speed coefficient of the preceding vehicle and the current vehicle, and adjusts the driving force or braking force of the current vehicle accordingly. As a method, The distance coefficient and the speed coefficient are selected such that the main pole of the inter-vehicle distance or the vehicle speed transfer function exists on the negative real axis, the selected distance coefficient and the speed coefficient are substituted into the transfer function, and the time gap is output of the transfer function. A method for controlling the distance between vehicles of a vehicle, characterized in that it is selected as the minimum value among the values to prevent the overshoot. The method of claim 1, wherein a data map indicating a correlation between the selected distance coefficient, speed coefficient, and time gap is configured, and when a time gap is selected, a distance coefficient and a speed coefficient corresponding to the target distance are derived from the data map. Distance control method of vehicle to set distance and target acceleration. The method of claim 1 or 2, wherein the inter-vehicle distance transfer function represents the propagation trend of the inter-vehicle distance by inputting the distance with the front car of the preceding vehicle and outputting the distance with the front car of the current vehicle, wherein the vehicle speed transfer function is preceding The vehicle speed of the vehicle is input and the vehicle speed of the current vehicle is output to indicate the propagation trend of the vehicle speed. The denominator and the coefficient of each molecule of each transfer function are composed of time gap, distance coefficient and speed coefficient. Vehicle distance control method.

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