JPH02141671A - Meter driving apparatus - Google Patents

Abstract

PURPOSE:To make it possible to approach a set point sequentially and to converge into a true value by multiplying a difference value by 1/n, adding the product and the value of the lowest 1 bit to the frequency digital value at the previous time, and determining the digital value at this time. CONSTITUTION:The frequency at this time is computed in a frequency operating part 27 and inputted into a subtracting part 28. In the subtracting part 28, the frequency at the previous time stored in a memory 34 is subtracted from the frequency at this time, and the difference value is outputted. In a multiplying part, the difference value is multiplied by 1/n. In adding part 32, the value of the lowest 1 bit is added to the product value. In adding part 33, the frequency at the previous time is added to the value. The result is made to be the output frequency at this time. In this way, the value approaches a set point by every 1/n + 1 bit of the difference value at the present time when the difference value is large. Even if the difference value is small and the value obtained by the multiplication with 1/n becomes '0' in binary number, a true value can be obtained after several output cycles.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application This invention relates to a meter drive device used in tachometers, speedometers, etc. for automobiles.

(B) Conventional technology Generally, as shown in Fig. 3, a speedometer for an automobile is equipped with a magnet M for swinging the needle in a magnetic field formed by two orthogonal coils L, , Lc. Place the coil L
, , Lc, a current corresponding to an input amount such as speed is passed, and the magnet M is rotated to cause the needle to swing. The meter drive device in this type of speedometer inputs a pulse signal whose period changes depending on the input amount, that is, the speed, and also inputs a clock signal generated by a basic clock generator, The clock signal of the counter is counted over the period, first the period T of the pulse signal is determined, and from this period T, the calculation of f=1/T is performed to calculate the frequency f. Since this digital data f is proportional to the input amount, a current corresponding to this digital value f is passed through the coil, Lc, and the magnetic needle, which is a magnet, is moved by the magnetic field generated by the coils L, Lc. It was made to swing to an angular direction determined by the digital value.

This conventional meter drive device performs sine and cosine calculations according to the frequency, that is, digital data, and causes the needle to swing by passing current in orthogonal coils according to the input amount. Speed 145k illustrated in the figure
If you change the instruction drastically from m/h to 25 km/h, the needle will follow path A and will not go to 20 km/h, but will take path B and change to a slow speed. Despite this, there was the inconvenience that the instructions were heading in a direction that could be ignored.

Therefore, in order to eliminate the above-mentioned inconvenience, the inventor of the present application,
When changing the needle indication significantly, calculate the difference value between the previous value and the current target value, and add the difference value xi/n (n: 2.
4.8,...), used this as an output value to cause the needle to swing, and then repeated this process to create a system with natural pointing movements, and has already filed a separate application.

(C) Problems to be Solved by the Invention In the meter drive device according to the above application, if n is now 8, the current output value is the previous value obtained by multiplying the difference value between the previous value and the target value by 1/8. It will be added to. By the way, in the case of binary numbers, multiplying by 1/8, that is, 0.125, means lowering three digits. For example, 1.
5 Xo, 125 is 1.1000XO,001=0.0
It becomes 011. Therefore, if all values represented by the lower 3 bits are multiplied by 0.125, the answer will be "0", and this "
No matter how many times you add "0" to the previous value, it will never get close to the true value.

Therefore, in the above method, once the difference value becomes small enough to be represented by 3 bits, the problem remains that it does not approach the true value and an error remains.

This invention was made by focusing on the above problem, and the difference value becomes small, and the value multiplied by l/n becomes "0".
The object of the present invention is to provide a meter drive device that can reach the true value in several output cycles even when the output voltage is ”.

(d) Means and Effects for Solving the Problems The meter driving device of the present invention includes first and second coils that are perpendicular to each other, means for inputting a pulse signal of a frequency corresponding to the input amount, and a clock signal generator. a calculation unit that counts the clock signal from the clock signal generation unit and calculates a digital value proportional to the input amount based on the count value; and a current corresponding to the digital value output from the calculation unit. a drive circuit that causes a current to flow through the first and second coils, and a needle whose angular orientation is determined by a magnetic field generated by the current flowing through the first and second coils, In the device that indicates a value proportional to storage means for capturing and storing the contents of the counting means in response to detection or count-up of the time counter; and calculating a digital value proportional to the input amount based on the contents of the storage means every time the time counter counts up. a calculation means for calculating a difference value between a current digital value and a previous output digital value by the calculation means; and a difference value calculation means for calculating a difference value between a current digital value and a previous output digital value, and the digital value is calculated based on stored data in switching detection. a means for determining whether or not the difference value is positive; and a difference value positive/negative determining means that responds when the determination by the determining means is NO, determines whether the difference value is positive or negative, and terminates the process if the difference value is positive.
means for multiplying the difference value by 1/n when the determination means makes a YES determination or the difference value of the difference value positive/negative determination means is negative; and a product obtained by the multiplication means and the least significant 1-bit value. and output value determining means for determining the current output digital value by adding it to the previous digital value.

In this meter drive device, the cycle of the input pulse signal switches, and the count value of the counter changes when the time counter counts up from the second time onward, or when this switching is detected, or before the switching is detected. It is stored in the storage means. Then, each time the time counter counts up, a digital value proportional to the input amount is calculated by the calculation means based on the count data stored in the storage means. Then, a difference value between the digital value calculated this time and the digital value calculated last time is calculated by the difference value calculation means, and it is determined whether the digital calculation described above was calculated based on the stored data in switching detection. .

If the input amount is relatively large, that is, if it is high speed, one cycle of the input pulse signal will arrive before the predetermined time elapses, so the determination result in this case is No. On the other hand, if the input amount is smaller than the predetermined value, that is, if the input speed is low, the predetermined time will elapse before one cycle of the input pulse signal arrives. Determine whether is positive or negative. Since the current digital value is calculated based on the count value of the counting means that has not yet counted one cycle, it is a digital value higher than the true frequency. Therefore, if the difference value is positive, it is ignored and the process is terminated. However, if the difference value is negative, the output is smaller than the above, or if the above determination result is NO, the difference value is multiplied by 1/n and
This multiplied value and the least significant 1 bit are added to the previous value and output. As a result, while the difference value is large, it approaches the target value by 1/n of the current difference value + 1 bit (LSB "1"), and even if 1/n of the difference value becomes "0", , L.S.
Since the 1 focus value of B is added each time, the needle deflection gradually approaches the target value.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a block diagram of a meter driving device showing one embodiment of the present invention. In the figure, the input signal circuit 1 is
A pulse signal generated in synchronization with the rotation of the wheels is input to the data calculation section 2. On the other hand, the reference clock signal generator 3
A clock signal from the data processing unit 2 is also input to the data calculation unit 2.

As shown in FIG. 1, the data calculation unit 2 includes a counter 20 that counts clock signals, and a rising detection circuit 21 that detects the rising edge (cycle switching) of an input pulse signal and generates a transfer signal and a reset signal. .2011Isec
A counter 22 that counts up each time a count-up signal elapses, and a flip-flop 23 that is set by the count-up signal of this counter 22 and reset by the reset signal, receives a count amplifier signal from the counter 22 in a set state, and then outputs a transfer signal. An AND circuit 24 that outputs the output of the AND circuit 24, or an OR that gives the transfer signal from the rising edge detection circuit 21 to the counter 20.
A circuit 25, a memory 26 that captures and stores the count value of the counter 20 every time it receives a transfer signal, and performs a 1/T calculation, that is, a frequency calculation, based on the count value T stored in the memory 26 each time the counter 22 counts up. The frequency calculation unit 27 calculates the currently calculated frequency f. A subtraction unit 28 that subtracts the previously calculated frequency f8-1 from and calculates the difference value f6.
, a determination unit 29 that determines the set/reset state of the flip-flop 23 at the time when the difference value f4 is calculated; when the determination unit 29 determines the set state of the flip-flop 23, it determines whether the difference value f6 is 0 or more. A determining unit 30 that determines whether
It is equipped with When the determination unit 29 determines the reset state of the flip-flop 23, the determination processing by the determination unit 30 is skipped.

Furthermore, when the discriminator 30 determines that f, is not >0, the data calculation section 2 determines that r,<r,-, and the discriminator 29 determines that Q=0 (reset state). If it is determined that there is, a difference value updating unit (multiplication unit) 31 updates the difference value f4 to 1/8 f d,
An adder 32 that adds one bit of SB, and an adder 33 that adds the added f4 and the previous frequency rt-t.
, this added value f, is stored and outputted as the current frequency f.

Frequency data f! output from the memory 34 of the data calculation section 2! is 10-bit digital data, of which the upper 2 bits determine which quadrant of the four divisions of one revolution it belongs to, and the quadrant determination unit 10 uses these 2 bits to determine which quadrant the hand to swing belongs to. A quadrant is determined, and the quadrant determination unit 10 outputs a direction signal determined by the determined quadrant.

The lower 8 bits are data corresponding to O@~90'' in each quadrant, and these are input to the sine operation unit 4 and the cosine operation unit 5, where sine and cos operation are performed, respectively, and the pulse width modulation circuit It is input to the driver (drive circuit) 8.9 via 6.7.Driver 8
The value corresponding to the signal from the sine calculation unit 4 and the electrode with the polarity corresponding to the direction signal are passed through the coil L1, and the driver 9
A current having a value corresponding to the signal from the os calculation unit 5 and a polarity corresponding to the direction signal is passed through the coil. Coil it.

When a current flows through the handle, a composite magnetic field is generated,
This composite magnetic field causes the needle to swing, indicating the angular direction according to the amount of input.

Next, the operation of the meter driving device of the above embodiment will be explained.

When a pulse signal corresponding to the rotation of the wheel is input from the input signal circuit 1, the rise detection section 21 detects the rise of the pulse signal, and first supplies a transfer signal to the counter 20, and then sends a reset signal. It is input to the counter 20 and flip-flop 23. The counter 20 transfers the count value that has been counted until then to the memory 2 by the transfer signal.
6, the clock signal from the reference clock generator 3 is reset by the reset signal, and thereafter the clock signal from the reference clock generator 3 is counted until the next reset signal is received.

Further, the counter 22 performs time counting asynchronously with the input pulse and outputs a count-up output every 2Qmsec, setting the flip-flop 23. When the flip-flop 23 is set and the count-up output is output, this The count contents of the counter 20 are transferred to the memory 26. In addition, in response to the count up of the counter 22, the frequency calculation section 27 calculates the current frequency f,
Calculate.

When the frequency of the input pulse signal is very high, that is, when one cycle is small, the rising edge detection unit 21 detects the rising edge, transfers the contents of the counter 20, and calculates the period from the reset state until the next reset signal is input. Better, 2Qmse
c Since the time to count up the counter 23 is shorter, the output from the counter 20 is always based on the transfer command before the counter 20 is reset, and therefore the count value of the clock signal corresponding to one period of the pulse signal That is, data T for one cycle is stored in the memory 26.

The frequency calculation unit 27 performs a calculation of 1/T to calculate the current frequency ri, and inputs it to the subtraction unit 28. Subtraction section 28
is the previous frequency r, -6 stored in the memory 34
is received as the other input, the previous frequency f,=1 is subtracted from the current frequency f, and the difference value f6 is calculated.

Next, the determination unit 29 determines that the Q output of the flip-flop 23 is 0.
Determine whether or not. Normally, when the frequency of the input pulse is high, the flip-flop 23 is in a reset state. Therefore, in this case, the output of Q=0 causes the discriminator 30 to be skipped and the multiplier 31 to set the difference value r4 to 1. /
Multiply by 8 and make the product a new f6. Then, the adding section 32
The LSB "1°" is added to this fd, and the adder 33 adds 1 of the difference between the previous frequency and the target value to the previous frequency f, -1.
/8 plus LSB "lo" is added to obtain the current output frequency f. In other words, the memory 34 stores a frequency r that is slightly closer to the target frequency than the previous frequency.
and outputs this frequency fz to the sine calculation section 4, the cosine calculation section 5, and the quadrant determination section 10, respectively. Then, a sin calculation section 4, a cos calculation section 5, and a quadrant determination section 10
In response to the output of The swing will reach a value that is 1/8+LSB "1" closer to the target swing.

Next, when the 20m5ec counter 22 counts up again, the frequency f! The calculation and the difference value calculation in the subtraction unit 28 are performed, and the difference value f
6 is derived, the determining unit 29 similarly determines whether Q=O, and the multiplying unit 31 multiplies the current difference value fd by 1/8. Then, in the adders 32 and 33, the previous frequency f! −＋
1/8 ra and the LSB "°l°" are added to create a new rl, which is stored in the memory 34 and then processed by the sin calculation unit 4, cos calculation unit 5, and quadrant determination unit lO as before.
Output each.

Repeat the above process every 201 Isec, and 1/8 of the difference value
Move the needle closer to the indicated target by +LSB"I II, and smoothly bring the needle closer to the target change value.

Eventually, the difference value f4 becomes small and l/8 fd becomes [0''
Even if it becomes, LSB "1"" is added, so it gradually approaches the target value by the amount corresponding to LSB "1゛°,
Finally, the deviation of the target value is obtained.

Next, when the cycle of the pulse signal manually input this time becomes very large, that is, the frequency becomes low, the count up of the 20m5ec counter 22 after reset is more likely than the rise detection by the rise detection section 21, that is, the detection of one cycle. becomes faster and when the 20m5ec counter 22 counts up, the flip-flop 23 is set and Q=1. In this state, the counter 22 counts up again and the transfer signal is outputted via the AND circuit 24 and the OR circuit 25. , even if the counter 20 has not yet counted one cycle of clock signals, it temporarily assumes that the count value up to that point is the count value for one cycle, stores it in the memory 26, and then calculates the frequency in the frequency calculation unit 27. The calculation is performed to calculate the virtual current frequency r1, and the subtraction unit 28 calculates the difference value f between the previous frequency and the current frequency. Then, the determining unit 29 determines whether the Q output of the flip-flop 23 is O or not, but since the flip-flop 23 is set this time, an output of Q=1 is output, and the determining unit 30 determines that r,
It is determined whether or not is greater than or equal to 0. If the difference value fa is 0 or more, this means that the current frequency is greater than the previous frequency, and in this case, the needle is moving from O in the direction of large deflection. When frequency calculation is performed using a count value of 20, which has not yet counted one cycle, the frequency will appear higher than the target frequency.
Since f5, which has a large frequency, is desired, the processing for frequency r4 is ignored and the processing is terminated.

However, for example, because the previous frequency was high and the input signal frequency became low, the flip-flop 23
is set, the difference value f6 between the current frequency ft and the previous frequency rt-t becomes -. Therefore, the judgment in the discrimination section 30 is NO, and then the multiplication section 31 multiplies the difference value f6 by 1/8. Then, 1/8 of the difference value f6
is set as a new f4, and the adder 32 further adds LS to this fd.
Bo "1°" is added, and then the addition section 33 adds this fd
The previous frequency f! -1 and new current frequency f
, and stored in the memory 34. In this case, r
4 is -, so the new frequency rt is the previous frequency r
, -1, the frequency having a value between the target frequency and the previous frequency is stored in the memory 34, and is also output to the sine calculation section 4, the cosine calculation section 5, and the quadrant determination section IO. Ru.

Then, current corresponding to the value between them flows through the coils L, , L by the drivers 8 and 9, and the needle detects the value between the deflection corresponding to the previous high frequency and the target low frequency indication. A magnetic field is generated as directed. Since it is 1/8 at a time, it will move smoothly one by one.

At the same time as this memory 34 outputs, the difference value f4 is derived at intervals of 20 m5ec or every cycle, and the determining unit 29, the determining unit 30, the multiplying unit 31, and the adding unit 3
2.33 is performed, the difference value f4 is multiplied by 1/8, and the LSB "1" is added, sequentially 1/8+L
SB "1" at a time, approach the target deflection angle, 1/
When the 8× difference value becomes “0”, the LSB is brought closer to the target value by “1°”.

(f) Effects of the Invention According to this invention, the difference value between the previous value and this time is multiplied by 1/n, and LSB '"1゛° is added to the previous value to obtain the current output value, and Since it is intended to move closer to the target value, even if the difference value becomes small and 1/n × difference value becomes "0", it can be converged to the true value by adding LSB ""1゛°. , no runout error occurs. Also, 1/n×
Since the difference value and the LSB "1" are basically added to the previous value, there is an advantage that the program configuration is simple.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the functional configuration of a data calculation section of a meter driving device according to an embodiment of the present invention, FIG. 2 is a schematic block diagram of a meter driving device according to an embodiment of the present invention, and FIG. , a diagram showing the relationship between the two coils and the needle of this meter device, and FIG. 4 are explanatory diagrams for explaining the problems of the conventional meter drive device. l: input signal circuit, 2: data calculation section, 3: reference clock generator, 8/9: driver, 20: counter,
21: Rising detection section, 22: Time counter,
28: Subtraction unit, 30: Difference value positive/negative determination unit, 31: Multiplication unit 32 and 33: Addition unit, Li and Lc: Coil. Patent Applicant ROHM Co., Ltd. Agent Patent Attorney Shigeru Nakamura

Claims (1)

[Claims] (1) First and second coils orthogonal to each other, means for inputting a pulse signal of a frequency corresponding to the input amount, a clock signal generating means, and counting the clock signal from the clock signal generating means. an arithmetic unit that calculates a digital value proportional to the input amount based on a count value; a drive circuit that causes a current to flow through the first and second coils in accordance with the digital value output from the arithmetic unit; 1 and a needle whose angular direction is determined by a magnetic field generated by a current flowing through a second coil, the meter driving device for indicating a value proportional to the magnitude of the input amount, The section includes a time counter that counts up every predetermined period of time, a switching detection means that detects switching of each period of the pulse signal, and a switching detection means that detects switching of each period of the pulse signal, and detects the switching in response to the detection of the switching or the counting up of the time counter. storage means for capturing and storing the contents of the counting means; calculation means for calculating a digital value proportional to the input amount based on the contents of the storage means each time the time counter counts up; difference value calculation means for calculating the difference value between the value and the digital value of the previous output; means for determining whether the digital value is calculated based on stored data in switching detection; difference value positive/negative determining means that responds when the determination is NO, determines whether the difference value is positive or negative, and ends the process if the difference value is positive; and YES determination by the determining means or difference between the difference value positive/negative determining means; means for multiplying the difference value by 1/n when the value is negative; and determining the current output digital value by adding the product obtained by the multiplication means and the least significant 1-bit value to the previous digital value. What is claimed is: 1. A meter drive device comprising: output value determining means.