KR100262597B1 - Calculation method of vehicle speed - Google Patents

Abstract

PURPOSE: A vehicle speed calculating method is provided to be capable of exactly calculating a vehicle at a time when a vehicle runs. CONSTITUTION: A vehicle sensor(10) generates a pulse based on a rotation of an output stage of a transmission. A calculating part(20) receives the pulse outputted from the vehicle speed sensor(10) to count a pulse number during a predetermined interval of time. The calculating part(20) adds a presently counted pulse number with a previously counted pulse number to output a vehicle. The calculating part(20) consists of the first and second registers(21,22) for increasing the pulse number whenever the pulse is applied from the vehicle speed sensor(10) and a central processing unit(25) for performing a calculation operation using data from the first and second registers(21,22) and initializing the first and second registers(21,22).

Description

Vehicle speed calculation method

The present invention relates to an apparatus and method for calculating the speed of an automobile accurately and quickly.

In controlling a vehicle, vehicle speed is an essential element for engine control and shift control.

In addition, in order to perform Intelligent Cruise Control (ICC), it is necessary to accurately and quickly measure the speed of the vehicle.

As shown in FIG. 1, a sensor for detecting a vehicle speed uses a reed switch, and generates an electrical pulse according to the rotation of the transmission output shaft.

That is, whenever the magnets M1, M2, M3, and M4 attached to the circumferential direction of the rotating body 1 pass through the reed switch 2 part as the transmission output shaft rotates, the reed switch is turned on to generate a pulse according to the power source. Outputs

In this case, since there are four magnets, four pulses are output while the rotor rotates once, and the vehicle speed is calculated using the pulses.

Conventionally, the periodic method was used to calculate the vehicle speed using the pulses output as described above.

In the cycle method, the cycle of the pulse outputted as described above was calculated, and the vehicle speed was calculated using the cycle.

However, when measuring the period of one pulse as described above, the measurement time is measured as the time between the first pulse and the next pulse is input, so the time to measure the vehicle speed becomes longer at low speed, which is difficult to use in fast control. There is a problem.

In addition, since only one period is used, the calculated vehicle speed does not have an accurate value.

In order to solve the above problems, there is an average period method, the average period method is a method of calculating the average period of the pulse for a predetermined time, it is possible to obtain a more accurate vehicle speed than the period method.

That is, when the pulse signal is irregularly output as shown in FIG. 2, the average period of the predetermined time T1 is calculated, and the vehicle speed is calculated using the calculated average period.

However, since the average period method needs to calculate an average over several cycles, the vehicle speed cannot be obtained during the calculation. There is a problem that is difficult to use.

In other words, if the calculation is performed every 100 milliseconds, the vehicle speed cannot be obtained in the meantime, but it is difficult to use the intelligent cruise control because the vehicle is not controlled during the driving distance during the high speed driving.

Another method of calculating the vehicle speed is a counting method, which counts the number of pulses input for a predetermined time and calculates the vehicle speed using the value.

However, in the counting method, as shown in FIG. 3, the number of pulses counted is 1 to 2 errors depending on how the pulses inputted for a predetermined time (T2) are counted at the beginning and the end of the counting. Can occur.

In particular, when the number of pulses to be counted is low in the low speed state, the difference in the calculated vehicle speeds differs depending on whether or not to count.

Therefore, the counting method also has a problem that is difficult to use for intelligent cruise control.

That is, the vehicle speed calculation methods such as the periodic method, the average period method, and the counting method of the prior art are difficult to use for automatic control such as intelligent cruise control, as the time for calculating the vehicle speed becomes longer and the accuracy of the vehicle speed calculation decreases. There is this.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle speed calculation method capable of accurately and quickly calculating a vehicle speed while driving a vehicle, which has been created to solve the conventional problems as described above.

1 is a view applying the principle of the vehicle speed sensor.

2 is a waveform diagram showing a vehicle speed calculation method using an average period method of the prior art.

3 is a waveform diagram showing a vehicle speed calculation method using a counting method of the related art.

4 is a block diagram of a vehicle speed calculating apparatus applied to the vehicle speed calculating method according to the present invention.

5 is an operation flowchart applying the vehicle speed calculation method according to the present invention.

6 is a waveform diagram of pulses at one kilometer per hour.

7 is a diagram showing vehicle speed calculation.

A vehicle speed calculating method of the present invention for achieving the above object comprises the steps of: determining whether or not a set time for calculating the vehicle speed has elapsed, and initializing a time coefficient when the vehicle speed has elapsed; Determining whether the value of the vehicle speed selection signal selects one of the first method and the second method; If the value of the vehicle speed selection signal selects the first method, storing the first pulse stored value as a first variable value and initializing the first pulse stored value; When the value of the vehicle speed selection signal selects the second method, storing the second pulse stored value as the second variable value and initializing the second pulse stored value; The vehicle speed is calculated by adding the first variable value and the second variable value, and the vehicle speed selection signal is switched.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram schematically showing the configuration of the vehicle speed calculating apparatus to which the vehicle speed calculating method according to the present invention is applied.

As shown, the vehicle speed calculating device includes a vehicle speed sensor 10 for generating and outputting a pulse according to rotation of a transmission output stage, and a number of pulses input for a predetermined time by receiving a signal from the vehicle speed sensor 10. It includes a calculating part 20 which counts and adds the value counted immediately before, and outputs the value as it is at a vehicle speed.

The calculator 20 registers the first register 21 and the second register 22 to increase the number of pulses each time a pulse output from the vehicle speed sensor 10 is applied, and the first register 21. ) And a central processing unit 25 performing a calculation operation using the data of the second register 22 and initializing the first register 21 and the second register 22.

In the vehicle speed computing device configured as described above, the vehicle speed sensor 10 is a reed switch, and generates and outputs a pulse according to the rotation of the transmission output stage, and 20 pulses are output when the transmission output stage rotates once.

The calculation unit 20 receives the signal output from the vehicle speed sensor 10, counts the number of pulses input for a predetermined time, and adds it with the value counted immediately before to calculate and output the vehicle speed, and adds it without additional calculation. The vehicle speed can be calculated only with the set value.

The operation of the operation unit 20 will be described in detail with reference to FIGS. 5, 6, and 7 as follows.

The first register 21 and the second register 22 of the operation unit 20 store the number of pulses output from the vehicle speed sensor 10, and the central processing unit 25 each time a pulse is applied. The value stored in the first register 21 and the second register 22 is increased, and a calculation operation is performed using the stored values, and the first register 21 and the second register as necessary. Initialize (22).

The central processing unit 25 reads the time coefficient TIME_SPD and determines whether or not the set time for calculating the vehicle speed has elapsed (S10).

Here, the setting time is 35.32 milliseconds, and the background set as described above will be described separately.

In the step S10 of determining whether or not the set time for calculating the vehicle speed has elapsed, the CPU 25 initializes the time coefficient TIME_SPD to measure the time again. Let (S20).

Then, by determining whether the value of the vehicle speed selection signal SPD_SELECT is '1', it is determined whether one of the first and second methods is selected (S30).

When the value of the vehicle speed selection signal is 1 in the step S30, that is, when the first method is selected, the central processing unit 25 stores the first pulse storage value SPD1 stored in the first register 21. Is stored as the first variable value SPD1_TEMP (S40), and the first pulse stored value is initialized (S50).

However, when the value of the vehicle speed selection signal is not 1 in the step S30, that is, when the second method is selected, the central processing unit 25 stores the second pulse stored value stored in the second register 22. Is stored as the second variable value SPD2_TEMP (S60), and the second pulse stored value is initialized (S70).

Then, the central processing unit 25 calculates the vehicle speed by adding the first variable value SPD1_TEMP and the second variable value SPD2_TEMP (S80), and inverts the value of the vehicle speed selection signal SPD_SELECT (S90). .

The above operation is repeated, and the vehicle speed is continuously calculated each time the set time elapses.

Referring to Figure 7 described in detail the operation as follows.

When the number of pulses output from the vehicle speed sensor 10 is 20 per revolution of the wheel, the set time is set to about 35.32 milliseconds, thereby simplifying the calculation of the vehicle speed and explaining the process of setting the value. Is as follows.

If the diameter of a car's wheel is 50 centimeters, one revolution will make it about 157 centimeters forward, and the wheel must turn about 637 laps to travel one kilometer.

However, since 20 pulses are output from the vehicle speed sensor 10 according to the rotation of the speed change output stage of the vehicle, that is, one revolution of the wheel, the number of pulses output for driving 1 kilometer is 12,740.

Here, if the vehicle speed is 1 kilometer per hour, 12,740 pulses are input per hour, and since 1 hour is 3,600 seconds, about 3.54 pulses are input on average per second.

Therefore, as shown in Equation 1 below, the period of one pulse is about 282.57 milliseconds.

However, as shown in FIG. 6, the pulses processed by the CPU 25 are processed for each rising and falling edge, so the period is 1/2 of the original period, so the period is 141.28 milliseconds, and FIG. As shown in

Thus, if one pulse is input for 282.57 milliseconds, then the vehicle speed is 1 kilometer per hour, which means that once a pulse count is achieved for 141.28 milliseconds, then the vehicle speed is 1 kilometer per hour. do.

That is, the number of pulses input for 282.57 milliseconds, that is, the number of count values made for 141.28 milliseconds, becomes the time per hour.

However, it can be seen that the first variable value SPD1_TEMP and the second variable value SPD2_TEMP store the current pulse value and the immediately preceding pulse value complementary to each other.

That is, at the time of FIG. 7 (D), the pulse number of the 'D' block and the 'E' block add the pulse number, and the value becomes the vehicle speed.

Here, the pulse number of the 'D' block is the number of pulses input for 70.64 milliseconds from (A) to (C) and the pulse number of the 'E' block is 70.64 from (B) to (D). Number of pulses input in milliseconds.

Therefore, when the two values are added together, the number of pulses input for 141.28 seconds is obtained, and the value becomes the vehicle speed at that time.

Here, the value counted from (b) to (c) is calculated twice in the 'D' block and the 'E' block.If there is a pulse input over the (c) time point, the count is calculated in the 'D' block. Error may occur, but since the error does not occur in the 'E' block, a counting error that may occur in the conventional counting method may be prevented.

And, if there is a pulse input over (b) time, the error may occur in the count in the 'E' block, but the error does not occur in the 'D' block, so counting error that can occur in the conventional counting method You can prevent it.

Therefore, in the conventional counting method, it is possible to prevent counting errors that may occur up to two.

Similarly, at the point (e), the pulse number of the 'E' block and the 'F' block add the number of pulses, and the value becomes the vehicle speed.

Here, the pulse number of the 'E' block is the number of pulses input for 70.64 milliseconds from (b) to (d) and the pulse number of the 'F' block is from (c) to (e) Number of pulses input in 70.64 milliseconds.

Therefore, by adding the two values, the number of pulses input for 141.28 seconds is obtained, and the value is the vehicle speed at that time, and the vehicle speed is output in 35.32 milliseconds after calculating the vehicle speed at the point (d). .

Therefore, it is possible to calculate an accurate vehicle speed within a much faster time than in the conventional method.

As described above, the vehicle speed calculating method according to the present invention can calculate the vehicle speed accurately and quickly while driving the vehicle, and can accurately and quickly perform engine control, shift control, and intelligent cruise control using the vehicle speed thus obtained. It works.

Claims (2)

(a) determining whether the set time for calculating the vehicle speed has elapsed, and initializing a time coefficient when the vehicle speed has elapsed, and (b) selecting one of the first method and the second method for the value of the vehicle speed selection signal. (C) when the value of the vehicle speed selection signal selects the first method in step (b), storing the first pulse value as a first variable value and storing the first pulse. Initializing the value; and (d) when the value of the vehicle speed selection signal in step (b) selects a second method, storing a second pulse value as a second variable value and storing the second pulse value. And (e) calculating a vehicle speed by adding the first variable value and the second variable value, and converting the vehicle speed selection signal. The vehicle speed calculating method according to claim 1, wherein in the step (a), the setting time for calculating the vehicle speed is set to one quarter of a period in which the pulse signal to be counted can be expressed as the vehicle speed as it is. .