JPS63215968A - Speed measuring instrument - Google Patents

Abstract

PURPOSE:To measure the speed of an object to be measured with a high accuracy and detect and estimate the speed with a constant response covering a wide range of speed change by comparing reference content set in a comparator in advance and the counting content of an incremental counter with each other. CONSTITUTION:The output of a vehicle speed sensor 10 is inputted to the LAT terminal of a latch circuit 12 for providing a latch timing and an electronic controller 14. The circuit 12 latches count up data wherein an upcounter 18 counts the clock signals of a reference signal generator 16 from the moment when a reset signal from the controller 14 is inputted with the latch timing. The counting content of the incremental counter 18 are also inputted to comparators 20a-20c other than the circuit 12. The comparators 20a-20c compare reference content set inside in advance and the inputted counting content of the incremental counter 18 with each other and, when the inputted counting content takes a larger value than that of the reference content, emits an output to the controller 14 and the controller 14 tells the present vehicle speed by a vehicle speed display 22 via a display driving circuit 24.

Description

Detailed Description of the Invention Object of the Invention (Industrial Application Field) The present invention relates to a speed measurement method that measures the speed of an object to be measured by measuring the period of a pulse train output according to the speed of the object to be measured. Regarding equipment.

(Prior Art) Conventionally, along with advances in digital signal processing technology, speed sensors that output a pulse train according to the speed have been frequently used to detect the speed of an object to be measured. For example, it includes a protrusion provided on a rotation axis that is involved in the speed of the object to be measured, and a proximity sensor placed on a fixed coordinate with respect to this rotation axis,
There are known devices that generate a pulse output every time a proximity sensor detects a protrusion that approaches due to rotation of a rotating shaft.

Therefore, a speed measuring device for detecting the speed of the object to be measured by inputting such a pulse train processes the pulse train as follows.

That is, when the pulse interval from the speed sensor is T, the speed ■ is calculated from equation (1).

V = ni/T...(1) However,
This type of speed measuring device, in which K is a proportionality constant, is capable of measuring speed with high accuracy despite its simple configuration, and is used in various industrial fields.

(Problems to be Solved by the Invention) However, even with the speed measuring device as described above, it is still not sufficient and has the following problems.

Since the speed of the object to be measured is calculated by substituting the period T of the detected pulse into equation (1), the responsiveness of speed detection changes greatly depending on the speed of the object to be measured.

That is, inputting pulses for at least one period is an essential condition for knowing the period T and detecting the speed V. Therefore, when the object to be measured is in a high speed state, the pulse period T is extremely short, and one pulse period is inputted in a short time, making it possible to detect the speed with good responsiveness.

However, when the object to be measured is at a low speed, the pulse period becomes long in proportion to the speed, and it takes a lot of time to input one period of pulses, which is essential for the operation of the speed measuring device. However, the responsiveness of speed detection is significantly reduced. Furthermore, as the speed of the object to be measured decreases, the display of the measurement result of the speed measuring device deviates from the actual speed, giving the user a sense of discomfort.

The present invention has been made to solve the above problems,
By measuring the period of the pulse train that is output according to the speed of the object to be measured, the speed of the object to be measured can be measured with high precision, and even if the speed of the object to be measured varies widely, the response remains constant. The purpose is to provide an excellent speed measurement device that can detect and estimate speed.

Structure of the Invention (Means for Solving the Problems) The means constructed in the present invention to solve the above problems, as shown in the basic configuration diagram in FIG. A speed measuring device that measures the period of a pulse train and measures the speed of the object based on the period, includes a pulse input means C1 that inputs the pulse train, and a pulse input means C1 that receives the latest pulse signal inputted by the pulse input means C1. A clocking means C2 that performs timekeeping from a starting point, and the clocking means C2
a comparison means C3 that compares the time measurement result of the time measurement result with a period determined based on the resolution of the speed measurement; and the comparison result of the comparison means C3 indicates that the time measurement result of the time measurement means C2 exceeds the period to be compared. The gist of the speed measuring device is a speed measuring device comprising: speed estimating means C4 for estimating the speed of the object to be measured based on the compared period when the speed is determined.

(Function) In the speed measuring device of the present invention, the pulse input means C1 is for inputting a pulse train output in accordance with the speed of the object to be measured. As an input part of this speed measuring device, it serves as an input port for pulse signals, and functions as a so-called interface, allowing connection with various external speed sensors while maintaining consistency.

The clocking means C2 executes timekeeping starting from the latest pulse signal input by the pulse inputting means C1.

This is to measure the pulse period T based on the latest pulse signal, and the time measuring means C2 is reset every time a pulse is input, and measures the time until the next pulse signal is input, that is, the period. be.

The comparison means C3 compares the time measurement result of the time measurement means C2 with a period determined based on the resolution of speed measurement. here,
The period determined based on the resolution of speed measurement is the period that appears when the speed is the detection target of speed measurement.

For example, if the resolution of speed measurement is 0.5 km/h, the speed to be detected is 0.5 km/h,
1, Okm/h, 1, 5km/h, 2
, Okm/h,... At this time, the period T representing these speeds is determined by the detection accuracy of the speed sensor, and is T1, T2, T3, T4,... (T1
>T2>T3>T4>...).

This period Ti representing the speed to be detected
(i=1.2.3.4, . . . ) is compared with the time measurement result of the time measurement means C2 by the comparison means C3.

The speed estimating means C4 calculates, based on the comparison result of the comparing means C3,
When the time measurement result of the timer C2 exceeds the period Ti to be compared, the speed of the object to be measured is estimated based on the period Ti used for the comparison.

That is, the clocking operation of the clocking means C2 starts from the time when the pulse inputting means C1 inputs the latest pulse signal, but even though the time TC has been clocked by the clocking means C2, the next pulse is still not available. No signal input,
Furthermore, it is assumed that the timekeeping work continues. At this time, the comparison by the comparing means C3 shows that the relationship between the time TC and the period Ti is TC
>T i. This period Ti is input to the pulse input means C1 as the period of the pulse signal at a certain speed 1. Therefore, if the time TC currently measured by the timer C2 is longer than the period Ti, the speed of the object to be measured is at least lower than the speed V1 at the period T1 used for comparison. It is presumed that there is.

In this way, the speed estimating means C4 determines how fast the elapsed time TC has been since the latest pulse signal was input, and how fast it has elapsed since the pulse signal was input for one period. Period T at which time exceeds the speed Vi to be detected
By knowing what value it shows compared to i,
The speed of the object being measured is estimated.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, examples will be given and explained.

(Embodiment) FIG. 2 is a block diagram when the speed measuring device of the embodiment is configured as a vehicle speed measuring device for detecting the speed of a vehicle.

In the figure, a vehicle speed sensor 10 is attached to a rotating shaft that rotates together with the wheels of a vehicle (not shown), and outputs a pulse signal corresponding to the rotation of the rotating shaft, that is, the vehicle speed. In this embodiment, the rotating shaft rotates at 637 rpm when the vehicle speed is 60 km/h, and the vehicle speed sensor
outputs 4 pulses per rotation of the rotating shaft. The pulse signal (pulse frequency Ij
FIG. 3 is a diagram showing the relationship between T ) and the actual vehicle speed V and the relationship between these and the vehicle speed Vl displayed by the vehicle speed measuring device of the embodiment in a state where the actual vehicle speed V is relatively low.

Due to the configuration of the vehicle speed sensor 10 as described above, as shown in the figure, the pulse period T outputted by the vehicle speed sensor 10 is 1.414 Sec or more when the actual vehicle speed (2) is 1° Okm/h or less. Similarly, the actual vehicle speed ■ is 1.5 to 2.5 km.
/h, pulse frequency KJIJT is 0.943 to 0.5
659ec, and the actual vehicle speed is 2.5km/h12
The μ pulse period XJIT on J is 0.565 Sec or more.

The output of the vehicle speed sensor 10 with such specifications is the latch circuit 1.
It is input to the LAT terminal that provides the latch timing of 2, and to the electronic control unit 14.

The data that the latch circuit 12 latches at the above latch timing is the count content of the up counter 18 that counts up the clock signal of the reference clock generator 16, and this up counter 18 receives the input of the reset command from the CLR terminal. The clock signal of the reference clock generator 16 is counted starting from the time when the reset signal from the electronic control unit 14 is inputted.

Further, the count contents of the up counter 18 are inputted to the input terminals of three types of comparators 20a, 20b, and 20c in addition to the latch circuit 12. These comparators 20a-20
c compares the reference content set in advance and the daily count content of the input up counter, and when the input count content becomes a large value exceeding the reference content, electronic control is performed. It generates an output to device 14. The reference contents set in the comparators 20a, 20b, and 20c are respectively when the vehicle speed is 2°5 km/
h, 1, 5km/h, 1, 0km/h
Palless at the time 0,565Sec, 0.943
Sec.

This is the reference clock number equivalent to 1.4149ec.

The measurement results of the vehicle speed measuring device of this embodiment are displayed on a vehicle speed indicator 22 constituted by a 7-segment VFD indicator provided in an indicator panel of the vehicle. The display drive circuit 24 drives the vehicle speed indicator 22, which receives a command for display speed VI from the electronic control unit 14, drives the vehicle speed display 22 in accordance with the command, and informs the vehicle occupants of the current vehicle speed. inform.

Next, the detailed configuration of the electronic control device 14 will be explained. The electronic control unit 14 is a digital logic circuit mainly composed of a microcomputer, and includes a CPU 14a that performs logical operations as usual, a ROM 14b that non-volatilely stores programs to be described later, and a temporary storage of information. and a RAM 14c that assists the logical operations of the CPU 14a. In addition, in order to connect these logic circuits and each of the above-mentioned electronic circuits with good consistency and to enable the exchange of information,
14e is provided.

The vehicle speed measuring device of this embodiment configured as described above has R
It operates as follows according to the following two types of programs stored in the OM 14b.

FIG. 4 is a flowchart I. of a speed measurement program, which is one of the programs. This program controls the main operation of the vehicle speed measuring device, and the vehicle speed sensor 10
The displayed speed VI displayed on the vehicle speed indicator 22 is controlled based on the detected output from the vehicle speed indicator 22.

This program executes when the CPU 14a receives a pulse input from the vehicle speed sensor 10 via the input/output port 14d.
The process is started by first outputting a clear signal to the up counter 1 day via the human output boat 14d, and processing is performed to start counting from 0 again (step 100).

Through this process, the up counter 1 day always indicates the count content representing the time interval from the latest pulse signal output from the vehicle speed sensor 10 until the next new pulse signal is input.

Further, the pulse signal of the vehicle speed sensor 10 is transmitted to the latch circuit 1.
Since this signal is simultaneously input to the LAT terminal for obtaining the latch timing of No. 2, the latch circuit 12 latches the count contents of the up counter 18 immediately before clearing, prior to the above-mentioned clearing process.

As is clear from the above explanation, the count content of the up counter 18 latched by the latch circuit 12 is the same as that of the vehicle speed sensor 1.
This is the reference clock number corresponding to the time interval between successive pulse signals and the next pulse signal in the pulse train outputted by 0, that is, the pulse period T.

Therefore, in step 110, which is performed following the processing in step 100, the content latched by the latch circuit 12 is read, and the pulse period T is calculated from this content. The indicated vehicle speed VI to be displayed on the vehicle speed indicator 22 is determined. As described above, the detection accuracy of the vehicle speed sensor 10 is determined by the rotating shaft to which it is attached, and the actual vehicle speed V can be determined from the circumference KJJT of the pulse signal from the vehicle speed sensor 10. Further, in this embodiment, since the detection accuracy (resolution) of the vehicle speed is set to lkm/h, the speed to be displayed from the calculated period T, that is, the display speed VI is determined by rounding calculations. The above-mentioned FIG. 3 schematically shows the relationship between the period T and the display speed VI.

As shown in the diagram, the displayed speed VI is 1.0k when the actual vehicle speed V is
Pulse period T output by the vehicle speed sensor 10 below tn/h
When is 1.4145ec or more, Okm/h
When the actual vehicle speed V is 1, 5 to 2, 5 km/h and the pulseless cycle time T is 0, 943 to 0, 565 SeC, it is 1 km/h, and when the actual vehicle speed V is 2.
It is preset to display a value of 3 km/h or more when the pulse period T is 0.565 SeC2 or more at 5 km/h or more. Such a relationship between the circumference WJJT and the displayed vehicle speed VI is stored in the ROM 14b in advance as a table or as a calculation formula, and when the displayed vehicle speed VI is determined based on the stored contents, it is determined in step 130 that follows. An output corresponding to the displayed vehicle speed VI is output to the display drive circuit 24, and the displayed vehicle speed VI corresponding to the actual vehicle speed 2 is displayed on the vehicle speed display 22. After this series of processing, the CPU 14a enters a wait state in which it waits for a pulse signal from the vehicle speed sensor 1O again.

In this way, by executing the speed measurement program shown in FIG. 4, the actual vehicle speed V can be faithfully displayed on the vehicle speed display 22 in units of up to 1 kTn/h. Furthermore, when the vehicle is operating at medium or high speeds in which the pulse signal from the vehicle speed sensor 10 is input in an extremely short period of time, sufficient responsiveness can be obtained even if only the processing according to the speed measurement program shown in Fig. 4 is performed. It is possible to display the vehicle speed.

However, when the vehicle is operating at low speed, especially when the vehicle is operating from just before stopping to stopping, the period T of the pulse signal output by the vehicle speed sensor 10 becomes large, and the processing according to the program shown in FIG. 4 alone is insufficient. Responsiveness decreases. For example, assume that the vehicle stops instantaneously from a driving state where the displayed vehicle speed VI is 3 km/h. At this time, only by processing according to the program shown in Fig. 4, the display speed VI gradually increases from 3km/h to OK.
m/h, but when it is detected that the period T of the pulse signal of the vehicle speed sensor 10 becomes 1.4143 ec or more, the ratio changes suddenly from 3 km/h to 0 km/h, and the speed of the vehicle This gives the occupants a sense of discomfort, and it takes 1.4145 ec to change the displayed vehicle speed VI.

In such a case, the vehicle speed measuring device of this embodiment processes the program shown in the flowchart shown in FIG. 5, and can avoid the above-mentioned situation.

FIG. 5 shows that when the output from any of the comparators 20a, 20b, and 20c is made to the turnout capo 14d,
4 is a flowchart of a comparator interrupt program that is processed by interrupting the processing of the program shown in FIG. 4 by the CPU 14a. The CPU 14 is used to process this interrupt program.
When a is entered, step 200 is first processed, and it is determined which comparator outputs the interrupt. When the interrupt is from the comparator 20a, the expected vehicle speed VE is 2.0 km/h; when the interrupt is from the comparator 20b, the expected vehicle speed VE is 1.01<m/h; When it is an interrupt, the expected vehicle speed V
0 to E. Okm/h is set (step 210.
220.230). Step 240 is then processed for the value of either of the two predicted vehicle speeds VE that has been set, and the displayed vehicle speed VI currently displayed on the vehicle speed display 22 is set.
A comparison is made between the predicted vehicle speed VE and the predicted vehicle speed VE. Through this processing, step 250 is executed only when it is determined that the displayed vehicle speed V1 is a larger value than the expected vehicle speed VE, and processing is performed to change the contents of the displayed vehicle speed VI to the preliminary vehicle speed VE. After processing step 250 or step 2
By the process of 40, the displayed vehicle speed VI becomes the expected vehicle speed VEI, -
, is determined to be below, the process moves to step 260, where an output for displaying the contents of the displayed vehicle speed VI on the vehicle speed display 22 is made to the display drive circuit 24, and the entire processing of this interrupt program is completed. and exit.

By processing the program shown in FIG. 5, the vehicle speed VI displayed on the vehicle speed indicator 22 faithfully represents the actual vehicle speed. That is, as mentioned above, the daily count contents of the up counter are determined not only by the latch circuit 12 but also by the three types of comparators 20.
Similar inputs are also made to a to 20c. Therefore, assume that the actual vehicle speed V suddenly changes from a low speed state of 3 km/h to a stopped state of 0 km/h, as in the example described above. At this time, the program shown in FIG. 4 remains open until a new pulse signal is input, and since the pulse period T cannot be calculated, the displayed vehicle speed VI cannot be updated.

On the other hand, the up counter 18 receives a new pulse signal and continues counting the reference clock until it is cleared again, and its contents gradually increase in value. Then, when the value exceeds the reference clock number corresponding to 0.5655ec, which is the reference content of the comparator 20a, the output from the comparator 20a is given to the output capo 14d, and the interrupt program shown in FIG. processing will be executed. At this time, since the interrupt is from the comparator 20a, the step 210 described above is selectively executed, and the expected vehicle speed VE is set to 2, OkTIl/h, and the displayed vehicle speed VI exceeds this value. In some cases, the slope of the displayed vehicle speed V1 is immediately equal to the slope of the expected vehicle speed VE.
．． The vehicle speed indicator 22 is updated to 0km/h and shows 2. Ok
m/h will be displayed. In other words, when the count content of the up counter 1B becomes a large value exceeding the vehicle speed 2, the cycle To of 565 Sec, which is 565 Sec, the next pulse signal is input and the accurate vehicle speed is calculated. Also, at least vehicle speed 2, OK
There is no doubt that the vehicle speed is less than /h. Therefore, when this state is detected, the interrupt program shown in FIG. 5 is immediately executed to change the displayed vehicle speed Vl.

Similarly, after the displayed vehicle speed VI has been changed, if there is no pulse input from the vehicle speed sensor 10 even after that, the count content of the up counter 18 gradually increases to a larger value and finally reaches the reference value of the comparator 20b. Contents 1,
This exceeds the period of 0.943 Sec at 5 km/h. At this time, step 220 in FIG. 5 is selected and executed, and the displayed vehicle speed VI immediately changes to 10. Updated to Okm/h. Moreover, even after that, if there is no pulse input from the vehicle speed sensor 10, the comparator 20c also outputs an output, and by selecting and executing step 230 of the program in FIG. 5, the displayed vehicle speed VI is 0. Okm/
h is updated again.

According to the vehicle speed measuring device of the embodiment configured as described above, the vehicle speed sensor 10 outputs an output according to the speed of the vehicle, similar to the conventional speed measuring device that calculates the speed from the pulse period T.
By measuring the period of the pulse train from the vehicle, the speed of the vehicle can be measured with high precision (see FIG. 4).

In addition, even in low-speed conditions such as a vehicle where the measured speed varies widely and the value of the pulse period T becomes large, and the responsiveness of vehicle speed measurement decreases, the vehicle speed measurement can be decomposed in advance. By the action of the comparators 20a to 20c, which memorize the period determined according to I don't even hold her.

In the above embodiment, the comparators 20a to 20c are configured by hardware circuits, but they may also be configured to store numerical values serving as comparison standards in the ROM 14b and perform comparisons using software. In addition, as a standard for comparison, in this example, 3
Although only the cycle of the species was targeted, more cycles may be compared to further improve the responsiveness of speed detection.

Effects of the Invention As described in detail with reference to embodiments, the speed measuring device of the present invention can measure the speed of an object to be measured by measuring the period of a pulse train output according to the speed of the object to be measured. In addition to being able to measure with high precision, it always ensures constant responsiveness even in the detection area where the speed of the object to be measured changes over a wide range, the period becomes large, and the responsiveness of speed detection decreases. Speed detection and estimation can be performed.

As a result, when displaying the measurement contents of the speed measuring device, it follows the actual speed of the object to be measured well, and various secondary effects are produced, such as eliminating the sense of discomfort in the display. Makes an excellent speed measuring device.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram showing the basic configuration of the speed measuring device of the present invention, Fig. 2 is a block diagram of the configuration of the vehicle speed measuring device of the embodiment, and Fig. 3 shows the relationship between the displayed vehicle speed and the actual vehicle speed of the same embodiment. Schematic explanatory diagrams showing the relationship with the detection pulse period, FIGS. 4 and 5
The figure shows a flowchart of a program used in the same embodiment.

Claims (1)

[Scope of Claims] A speed measuring device that measures the period of a pulse train output according to the speed of an object to be measured, and measures the speed of the object to be measured based on the period, comprising: a pulse input means for inputting the pulse train. , a timekeeping means that performs timekeeping starting from the latest pulse signal input by the pulse input means, and a comparison means that compares the timing result of the timekeeping means with a period determined based on the resolution of speed measurement; Speed estimating means for estimating the speed of the object to be measured based on the compared period when it is determined based on the comparison result of the comparison means that the time measurement result of the time measuring means exceeds the compared period. A speed measuring device comprising: