JPH04305168A - Method for correcting error and measuring quantity of electricity - Google Patents

Abstract

PURPOSE: To make it possible to measure the quantity of electricity by correcting an error even if a reference amount is unstable in measuring by sequentially measuring the quantity of electricity and an auxiliary quantity of electricity of unknown value and substantially without drift by the same unit. CONSTITUTION: In the electronic controller of an internal combustion engine, the quantity of electricity 3 is measured at the input terminal 1 of the controller 2, supplied as an analog voltage Um, and the voltage is input to the adapter circuit 4 of the controller 2. The output 5 of the circuit 4 is connected to an A-D converter 6. An electric reference amount 7 is input to the converter 6, and the output of the converter 6 is input to a microcomputer 9. Even if the amount 7 is unstable due to a drift capable of being previously not digitized, the quantity 3 can be accurately measured by using an electric auxiliary amount 14 having to drift. To obtain the value of the amount 14, the correction coefficient of a correct value is obtained by using two known voltage, and thereby an analog electric amount is obtained as a digital value.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention is a method for measuring an electrical quantity by correcting an error, and more specifically, a method for measuring an analog quantity of electricity, especially voltage, by correcting an error as a digital value. The present invention relates to a method of measuring an electrical quantity by using a difference obtained by comparing a known electrical basic quantity and a measured value of the electrical basic quantity to correct the measurement result of the electrical quantity.

0002

2. Description of the Related Art In various fields of electronic technology, it is necessary to determine the absolute value of an electrical quantity. This requires the use of calibrated measuring equipment. This calibration is necessary because, for example, the characteristics of a series of devices are not equal due to component tolerances.

Similarly, in automobile electronic technology, there is a problem in that the amount of electricity must be determined accurately. In particular, it is necessary to detect the amount of electricity obtained by the sensor without error. This is because this amount of electricity must be used to operate the internal combustion engine. A control device for driving the internal combustion engine of the motor vehicle is preferably used to process and adjust the operating parameters. At the inputs of this control device, inter alia, electrical quantities that are related to the operating state are input. Therefore, this amount of electricity must be detected without measurement error, taking into consideration later processing. Measurement errors arise, inter alia, from component tolerances, drift phenomena (especially temperature-related) and other offset quantities. In order to eliminate this measurement error, gain and offset have conventionally been adjusted using a hardware configuration within a control device. For example, this adjustment is carried out by setting a regulating resistor. However, such methods are cumbersome and complex for mass production and require corresponding costs.

0004

[Problem to be solved by the invention] DE-OS38443
No. 33 describes a method for correcting tolerances of elements during signal processing. In order to take into account the effects of integrator tolerances, a microcomputer generates a signal that, when error-free signal processing, results in a known (theoretical) integral value. Due to the above-mentioned component tolerances, the integrator will produce different integral values. By comparing the actual integral value with the theoretical integral value, a difference value representing the amount of error is formed, and this difference value is used to correct the integral value. Since an analog/digital converter is connected after this integrator, the integrated value is obtained as a digital value.

The present invention has been made in view of the above points, and provides a measuring method that allows error correction and measurement of electrical quantity even if the reference quantity is unstable at the time of measurement using a simple method. The task is to do so.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present invention is a method for measuring an analog quantity of electricity, especially voltage, as a digital value with error correction. In this method, the electrical quantity is measured by correcting the error by using the difference obtained by comparing the measured value of the electrical quantity and its basic electrical quantity to correct the measurement result of the electrical quantity, and the electrical quantity and value are accurate. Electrical auxiliary quantities, which are unknown but have almost no drift, are sequentially measured using the same device, converted to digital values by an analog/digital converter to which an electrical reference quantity is applied, and the ratio of each digital value is calculated. A configuration is adopted in which the reference amount is removed by forming , and a correction value is obtained to obtain an accurate value of the electrical assistance amount.

[0007]

[Effect] With this configuration, it is possible to measure the amount of electricity without error even if the parameters required for measurement do not exactly correspond to the set values, for example, even if their absolute values are not accurately known. . For example, even when the reference quantity is unstable during operation and is subject to a drift phenomenon that cannot be quantified in advance, the method of the present invention makes it possible to accurately detect the electrical quantity. According to the invention, the electrical quantity and the drift-free electrical auxiliary quantity, whose magnitude is not precisely known, are measured directly one after the other using the same device.

What must be noted here is that although it is easy to obtain a drift-free electrical auxiliary amount, for example, a stabilized voltage, in terms of circuit technology, the absolute value of the electrical auxiliary amount may vary due to element tolerances. This means that it is difficult to reproduce the actual size. In order to ensure that each electric supplement has the same value in a mass-produced device, the difficult adjustment methods described in the prior art are required.

[0009] The method according to the invention requires only the condition that there is no drift in the amount of electrical assistance, and since it is sufficient to make an accurate measurement even when its exact magnitude is not known, such adjustment is not necessary. Since the measurement of the electrical quantity and the electrical auxiliary quantity is carried out directly one after the other, the reference quantity required for the measurement is constant within the measurement time of this quantity, and therefore it is considered that there is no drift. The above-mentioned drift phenomenon usually appears over a long period of time and is caused, for example, by temperature fluctuations.

The above-mentioned reference quantities (reference parameters) are input to an analog/digital converter which in this embodiment normally operates by determining a ratio. According to the invention,
This reference quantity is removed by forming a ratio of the digital value of the electrical quantity to be detected and the electrical auxiliary quantity. This means that if the measurement time is short, the reference amount can be considered constant;
This reference quantity is made possible by being canceled by forming a ratio. However, the amount of electrical assistance is not necessarily the same for each mass-produced device, and as mentioned above, its size is not accurately known, and various values occur due to gain, dispersion, and offset error. Therefore, the accurate value of the electrical assistance amount can be obtained by correcting it with a correction value. The method for determining this correction value is publicly known (DE-OS3844333). The principle of this is to use a basic electrical quantity whose value is known and to compare that basic quantity with its measured value. In that case, the differences occurring through the comparison are determined and a correction value is formed, with which the quantity to be corrected (in this case the measured value of the electrical assistance quantity) is processed.

As described above, according to the method according to the present invention, it is possible to accurately detect an electric quantity as a digital value without using a complicated calibration method using hardware. In that case, long-term drifts of the required reference quantity do not lead to measurement errors. An additional amount of electrical assistance is required for this, but its value does not have to be known exactly. The condition is that there be no drift, and this can be achieved to an almost satisfactory degree with simple circuit techniques. Calibration using such software can be repeated (automatically) at predetermined intervals.

According to an embodiment of the present invention, the accurate digital value N_i of the quantity of electricity is

[0013]

[Math. 9]

It is determined according to the formula: However, v_i is an accurate (ideal) proportionality coefficient, Nm is the digital value of the electrical quantity, NH is the digital value of the electrical auxiliary quantity, and 2 to the nth power indicates the resolution of the analog/digital converter. Digital value N
is 0,1. ．． ．． It only takes a value of 2 to the nth power - 1. The number of possible values, ie the resolution of the analog/digital converter, is related to the number of bits. For example, if 8 bits are used, 256 states are obtained. There can be no intermediate values for each digital value. The above description applies to all similarly constructed equations described below.

Preferably, the digital value of the quantity of electricity is

00
16]

[Math. 10]

[0017] Furthermore, the digital value of the electric assistance amount is

001
8]

[Math. 11]

It is determined by: However, UH_i is the exact value of the electrical assistance amount, and Uref_r is the actual reference amount. In the above, an ideal relationship is established regarding the amplification coefficient, offset, and correction voltage. However, the reference amount is accompanied by an error. In this application, an exact (or ideal) value is a value without error, and an actual value means a value with possible errors.

[0020] In order to find the accurate value of the electric assistance amount, first

[0021]

[Math. 12]

The following formula is used. Next, the value obtained in this way is

[0023]

[Math. 13]

The correction coefficients k1, k2 of the correction value according to the formula
will be corrected. However, v_r is an actual proportionality coefficient, UH is an electrical auxiliary amount (auxiliary voltage), and U_offset_r is an actual offset amount. The ideal offset amount is "0"
The value is . The actual value is corrected multiplicatively and additively by the proportionality factor and the offset amount.

The correction value is based on two known voltages Um1 and Um2.
It can be found using digital values of these known voltages,

[0026]

[Math. 14]

are measured and these known exact values

0
028]

[Math. 15]

Correction value using

[0030]

[Math. 16]

[0031]

[Math. 17]

[0032] is obtained. However, Uref_i is an accurate reference amount.

Preferably, the electrical quantity or electrical auxiliary quantity is supplied to the input of the analog/digital converter via a changeover switch. The electrical quantity, electrical auxiliary quantity and reference quantity are preferably voltages.

Even when the reference quantity is unstable due to a drift phenomenon that cannot be quantified in advance, the quantity of electricity can be accurately measured by using an electrical auxiliary quantity without drift, although the absolute value is not necessarily known accurately. is understood. In order to eliminate amplification errors and offset errors that always occur due to individual variations during mass production, and to obtain the accurate value of the electrical auxiliary amount, which is stable but whose absolute size is not precisely known, two known The correction coefficient of the correction value is obtained by comparing the measurements using the voltage of . This makes it possible to accurately obtain an analog electrical quantity as a digital value without using a hardware adjustment method.

[0035]

EXAMPLES The present invention will be explained in detail below using examples.

In an electronic control device for an internal combustion engine, for example an electronic control device for controlling a diesel injection device, it is necessary to measure an electrical quantity 3 at the input terminal 1 of the control device 2 . This is because the absolute value of this quantity of electricity is used as a control variable for determining the operating parameters (for example, injection time) of the internal combustion engine obtained by the control device 2. Electricity amount 3
is supplied as an analog voltage Um. This analog voltage is input to an adapter circuit 4 of the control device 2 which also performs a protection function.

The output 5 of the adapter circuit 4 is connected to an analog/digital converter 6. This analog-to-digital converter works by determining a ratio. An electrical reference quantity 7 is input to this analog/digital converter 6 . This reference quantity is formed by the reference voltage Uref. The output 8 of the analog/digital converter is input to a microcomputer 9 connected to a programmable memory 10. Memory 10 is preferably configured as an EEPROM. The microcomputer 9 is connected via a data line 11 to a serial interface 11', to which an external test computer 12 is connected. Although not shown, in another embodiment, the functions of the inspection computer 12 can be performed by the microcomputer 9, and in that case, the inspection computer 12 can be omitted.

The operation of the circuit of FIG. 1 is as follows.

In order to obtain the analog voltage Um accurately (that is, without error) as a digital value, the measured value is corrected with a correction value to remove errors caused by individual variations during mass production, for example. In an ideal case, i.e. without any errors, the voltage Um is input to the analog/digital converter 6 via the adapter circuit 4, thereby converting the digital value

[0040]

[Math. 18]

It is converted to However, N_i=0, 1, 2
,...2 to the nth power -1. Analog/digital converter 6
The number of possible digital values is determined according to the resolution, that is, the number of bits. For example, with 8 bits, 256 digital values are possible. In the above formula, v_i is an ideal proportionality coefficient, and Uref_i is the absolute value of the ideal reference amount 7. However, since there are individual variations that lead to the measurement errors mentioned above, the actual values, rather than the ideal values, must be considered. Multiplicative as well as additive errors usually occur. Therefore, the digital value N_i is not accurate, and the actual digital value is

[0042]

[Math. 19]

(U_offset_i=0). Multiplication as well as additive deviations make the measurement accuracy unreliable. Until now, in the prior art, amplification and offset adjustment have been performed by hardware processing within the control device 2, for example, by setting an adjustment resistor.

According to the present invention, such hardware processing becomes unnecessary. For this purpose, in the calibration mode, two known voltages Um1, Um2 are input one after the other to input 1 of the control device 2. These voltages are

[0045]

[Math. 20]

It is converted into a digital value of . The index "r" means the actual value, and the index "i" means the exact ideal value. The known ideal values corresponding to the digital values N_r1 and N_r2 are:

[0047]

[Math. 21]

[0048] In order to obtain the ideal value from the actual value, a correction value consisting of correction coefficients k1 and k2 is calculated using the microcomputer 9 or the inspection computer 12. These correction coefficients are as follows.

[0049]

[Math. 22]

Once these correction coefficients have been determined, the adjustment mode is exited and normal operation is resumed. continue,

[0051]

[Math. 23]

All measured values N_r are corrected according to the relationship: In this way it becomes possible to eliminate the influence of individual variations.

Analog / formed by reference voltage Uref
The reference quantity 7 required for the digital converter 6 is usually not stable due to drift phenomena that cannot be quantified in advance. However, the method shown in FIG. 2 allows the analog quantity of electricity to be measured to be accurately determined as a digital value. To this end, in FIG. 2, in addition to the configuration shown in FIG. 1, a changeover switch 13 is provided between the adapter circuit 4 and the analog/digital converter 6. Thereby, the voltage to be measured U
m or an electrical supplementary quantity 14 is applied to the input of the analog/digital converter 6. Electrical auxiliary quantity 14 is preferably formed by an auxiliary voltage UH.

The method described above is based on the premise that the magnitude of the reference voltage Uref is accurate, but the auxiliary voltage Uref
H is not like that. The auxiliary voltage UH must be free of drift, but its absolute value does not necessarily have to be known exactly. Normally, such voltages can be easily achieved with voltage stabilization circuits. Although such a voltage can have an absolute value with substantially no drift, the absolute value is not necessarily the same due to, for example, variations in elements during mass production.

The method is carried out in two stages. First, as described above, the voltage Um is measured, and immediately after that, the voltage Um
H is measured. In that case, it is assumed that the reference voltage Uref does not change between the two measurements directly performed one after the other. If the relationship for amplification factor, offset and auxiliary voltage is ideal, the absolute measured value is:

[0056]

[Math. 24]

[0057]

[0058]

[Math. 25]

From the measured value (digital value) of

[0060]

[Math. 26]

The following is obtained.

In the case of mass production, as mentioned above, amplification and offset errors occur due to individual variations, and although the auxiliary voltage UH is stable, its absolute value is not necessarily known accurately. The values, like those for the measured values Um mentioned above, usually also have to be corrected by corresponding correction values. This means that first the corresponding correction coefficients k1, k2 are determined in the adjustment mode, and then correction is performed to obtain the ideal value.

The method of the present invention will now be described with reference to the flowchart of FIG. After starting step 15, in step 16 it is determined whether to operate in adjustment mode (algorithm mode) A or normal mode No. In the case of regulation mode A, in step 17 the voltage U whose value is known is
m1 is input. In step 18 the corresponding digital value N_r1 is measured. Subsequently, in step 19, a second known voltage Um2 is input to input 1 of control device 2. The corresponding digital value N_r2 is measured in step 20;
Subsequently, in step 21, correction coefficients k1 and k2 are determined. The correction coefficients k1, k2 are stored in the memory 10 of the control device 2 in step 22. Next, a normal operation No. is entered, whereupon the actual value N_r is measured in step 23 and corrected in the next step 24 by using correction coefficients k1, k2.

When operating with the electrical auxiliary quantity 14 (auxiliary voltage UH) as in the case of FIG. 2, the voltage Um is input in step 26 following the start step 25 as shown in FIG. , the corresponding digital value Nm is determined in step 2
Measured at 7. Voltage UH is then input to analog/digital converter 6 (step 28). Subsequently, in step 29, the corresponding digital value NH is measured. The above-mentioned correction of the auxiliary voltage UH is performed in steps 17 to 2 described above.
2.

[0065] The method described above thus provides for software adjustments that do not require any internal manipulation of the device. This method can be used not only during the manufacture of the device, but also during maintenance, for example for later calibration, or during operation of the device, if an operating point with the measured voltage being investigated is obtained, e.g. controlled by the measured voltage. If a position measurement signal of the circuit is available and a mechanical stop allows setting a precisely known operating point, it can also be used during normal operation.

As described above, according to the present invention, it is possible to accurately detect the voltage value that should be absolutely measured in the control device having the analog/digital converter 6 and the microcomputer 9 that operate by determining the ratio. Become,
Offset as well as amplification errors can be removed by software-implemented adjustments. For this purpose, as already explained, two known voltages Um are applied to the inputs of the control device 2.
1 and Um2 are input and then the actual measured value is determined. Multiplicative and additive correction values are determined by comparison with the corresponding ideal values, and the actual measured values are converted into ideal measured values. The correction coefficient of the correction value is stored in the memory 10 of the programmable control device 2 and used for correction of subsequent measured values. If a drift appears in the reference voltage Uref of the analog/digital converter 6, an auxiliary voltage source UH free from drift is used, although the absolute voltage value is not accurately known. This voltage source can be realized by simple means. The method described above is used to determine the exact value of the auxiliary voltage, and the removal of measurement errors is performed as described above.

[0067]

[Effects of the Invention] As explained above, according to the present invention,
, the electrical quantities and values are precisely unknown and electrical auxiliary quantities with almost no drift are sequentially measured using the same device, and converted into digital values by an analog/digital converter to which an electrical reference quantity is applied; By forming a ratio of each digital value, the reference quantity is removed and a correction value is obtained to obtain the accurate value of the electric auxiliary quantity, so that the reference quantity is unstable due to a drift phenomenon that cannot be quantified in advance. Even at certain times, the electrical quantity can be measured accurately by using a drift-free electrical auxiliary quantity, although the absolute value is not necessarily known exactly.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus in which the method of the invention is used.

FIG. 2 is a block diagram of a device operating with an electrically auxiliary quantity in which the method of the invention is used.

FIG. 3 is a flowchart illustrating the method of the present invention.

[Explanation of symbols]

2 Control device 3 Amount of electricity 4 Adapter circuit 7 Standard amount 9. Microcomputer 10 Memory 12 Inspection computer 14 Electricity subsidy amount

Claims (7)

[Claims] [Claim 1] A method for measuring an analog electrical quantity, especially voltage, as a digital value with error correction, by comparing a basic electrical quantity whose value is known and a measured value of the basic electrical quantity. In a method of error-correcting and measuring electrical quantities by using the obtained difference to correct the electrical quantity measurement results, the electrical quantities and values are unknown exactly, but electrical supplementary quantities with almost no drift are sequentially measured using the same device. , convert it into a digital value by an analog/digital converter to which an electrical reference quantity is applied, remove the reference quantity by forming a ratio of each digital value, and obtain a correction value to calculate the electrical reference quantity. A method of measuring an electrical quantity with error correction, characterized by obtaining an accurate value of an auxiliary quantity. [Claim 2] An accurate digital value of the electrical quantity, where v_i is an accurate proportionality coefficient, Nm is the digital value of the electrical quantity, NH is the digital value of the electrical auxiliary quantity, and 2 to the nth power is the resolution of the analog/digital converter. The method according to claim 1, characterized in that (N_i) is determined according to the following equation. [Claim 3] Let UH_i be the exact value of the electrical assistance amount, U
The method according to claim 1 or 2, characterized in that, with ref_r as an actual reference quantity, the digital value of the electrical quantity is determined as Equation 2; and the digital value of the electrical auxiliary quantity is obtained as Equation 3. 4. In order to obtain an accurate value of the electrical assistance amount, where v_r is the actual proportionality coefficient, UH is the electrical assistance amount, and U_offset_r is the actual offset amount, NH_r is first determined according to the following equation: 5. The method according to claim 1, wherein NH_r is corrected using correction coefficients k1 and k2 according to the formula: [Claim 5] Find the digital values [Equation 6] of the two known voltages Um1 and Um2, use Uref_i as an accurate reference quantity, compare these digital values with their exact values [Equation 7], and use the comparison value as 5. The method according to claim 1, further comprising determining correction coefficients k1, k2 from the following equations. 6. The method as claimed in claim 1, wherein the electrical quantity or the auxiliary quantity is input to the analog/digital converter via a changeover switch. [Claim 7] Any one of claims 1 to 6, wherein the amount of electricity, the amount of auxiliary electricity, and the reference amount are voltages.
The method described in section.