Analog-to-digital conversion apparatus

Abstract

To provide an analog-to-digital conversion apparatus capable of removing a low-frequency noise.SOLUTION: An analog-to-digital conversion apparatus includes: a plurality of terminals for inputting a plurality of analog values indicating a specific rotation angle of a measurement target in a chronological order; a selection circuit for selecting one of the plurality of terminals; a conversion circuit for converting the plurality of analog values selected by the selection circuit into a plurality of digital values; an average value calculation circuit for calculating an average value of the plurality of digital values converted in the chronological order in a specific range; and a control circuit that, when the conversion circuit converts the plurality of analog values into the plurality of digital values, performs a control to alternately change a direction of a voltage to be applied to the measurement target to a first direction and a second direction opposite to the first direction for each sampling timing of the conversion circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an analog-to-digital conversion device. [Background technology]

[0002] The analog-to-digital conversion device disclosed in Patent Document 1 performs analog-to-digital conversion of multiple sampling points using a single analog-to-digital conversion circuit. Hereinafter, analog-to-digital may be simply referred to as AD. Considering that AD conversion devices are likely to be installed in noisy locations, it is desirable for them to have high noise resistance. To increase noise resistance, a known method is to average multiple AD conversion values ​​when calculating data for sampling points. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-259752 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is difficult to remove low-frequency noise simply by averaging the AD conversion values. As such, there is room for improvement in the conventional technology in terms of achieving AD conversion of multiple sampling points using a single AD conversion circuit.

[0005] In view of the above circumstances, an object of the present disclosure is to provide an analog-to-digital conversion device capable of removing low-frequency noise. [Means for solving the problem]

[0006] In order to solve the above problem, the analog-to-digital conversion device according to the present disclosure includes a plurality of terminals for inputting a plurality of analog values ​​indicating a specific rotation angle of an object to be measured in chronological order, a selection circuit for selecting one of the plurality of terminals, a conversion circuit for converting the plurality of analog values ​​selected by the selection circuit into a plurality of digital values, an average calculation circuit for calculating an average value of the plurality of digital values ​​converted in chronological order within a specific range, and a control circuit for performing control to alternately change the direction of a voltage applied to the object to be measured between a first direction and a second direction opposite to the first direction at each sampling timing of the conversion circuit when the conversion circuit converts the plurality of analog values ​​into a plurality of digital values. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of an analog-to-digital conversion device 100 according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the potentiometer 200. [Figure 3] FIG. 3 is a flowchart for explaining the operation of the analog-to-digital conversion device 100. [Figure 4] FIG. 4 is a diagram for explaining the operation of the analog-to-digital conversion device 100. In FIG. [Figure 5] FIG. 5 is a diagram for explaining the operation of the analog-to-digital conversion device 100. In FIG. [Figure 6] FIG. 6 is a diagram for explaining the operation of the analog-to-digital conversion device 100. In FIG. [Figure 7] FIG. 7 is a diagram showing the configuration of an analog-to-digital conversion device 100A according to a comparative example. [Figure 8] FIG. 8 is a flowchart for explaining the operation of the analog-to-digital conversion device 100A. [Figure 9] FIG. 9 is a diagram for explaining the operation of the analog-to-digital conversion device 100A. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and descriptions thereof will be omitted as appropriate.

[0009] (Embodiment) 1 is a diagram illustrating an example configuration of an analog-to-digital conversion device 100 according to an embodiment of the present disclosure. The analog-to-digital conversion device 100 may include a plurality of input terminals 1, an input terminal selection circuit 2, an AD conversion circuit 3, a control circuit 4, and an average value calculation circuit 5.

[0010] The multiple input terminals 1 may be interpreted as terminals for inputting multiple analog values ​​indicating specific rotation angles of the object to be measured in chronological order. Each of the multiple input terminals 1 is connected to a measurement end of the object to be measured, potentiometer 200. The configuration of potentiometer 200 will be described in detail later.

[0011] Any one of the plurality of input terminals 1 may be selected by an input terminal selection circuit 2. An analog value (voltage value) measured by a potentiometer 200 is input to each of the plurality of input terminals 1. The analog value (voltage value) is input to an AD conversion circuit 3 via the input terminal selection circuit 2.

[0012] The input terminal selection circuit 2 may be interpreted as a circuit that selects one of the multiple input terminals 1.

[0013] The AD conversion circuit 3 may receive an analog value (voltage value) from the input terminal 1 selected by the input terminal selection circuit 2, convert the input analog value (voltage value) into a digital value, and input the converted digital value to the addition circuit 6. The converted digital value is stored in a result register 10, which is a register with a number corresponding to the terminal number. The terminal number may be interpreted as a number that identifies each of the multiple input terminals 1.

[0014] The control circuit 4 may be interpreted as a circuit that executes control to alternately change the direction of the voltage applied to the object to be measured between a first direction and a second direction opposite to the first direction at each sampling timing of the AD conversion circuit 3 when the AD conversion circuit 3 converts multiple analog values ​​into multiple digital values. The control circuit 4 may generate a control signal CS that controls the register output selection circuit 11, the input terminal selection circuit 2, and the potentiometer 200. The control signal CS may be interpreted as a signal for selecting the result register 10, a signal for selecting the input terminal 1, or a signal for controlling the direction of the voltage applied to the potentiometer 200.

[0015] The average value calculation circuit 5 may be interpreted as a circuit that calculates the average value of a plurality of digital values ​​converted in chronological order within a specific range (for example, the averaging angle measurement range shown in FIG. 4).

[0016] The average value calculation circuit 5 may add to the result register 10 a plurality of digital values ​​sampled when the direction of the voltage applied to the object to be measured is the first direction and the second direction, respectively, and calculate the average value of each of the values ​​in the first direction and the second direction by dividing each of the values ​​in the first direction and the second direction added to the result register 10 by a specific number of times.

[0017] The average value calculation circuit 5 may calculate the rotation angle of the object to be measured based on the average values ​​of the voltages applied to the object to be measured in the first direction and the second direction.

[0018] The average value calculation circuit 5 may include an adder circuit 6, a divider circuit 7, a comparator circuit 8, a number counter 9, a plurality of result registers 10, and a register output selection circuit 11.

[0019] The adder circuit 6 adds the value of the result register 10 corresponding to the input terminal 1 to the digital value converted by the AD converter circuit 3 .

[0020] The division circuit 7 obtains an average value by dividing the output from the addition circuit 6 by a predetermined number of times (number of samples).

[0021] The comparator circuit 8 may compare the count value from the count counter 9 with the number of samples, and input the comparison result to the control circuit 4. The register output selector circuit 11 selects one of the plurality of result registers 10 based on a control signal CS from the control circuit 4, and outputs the value stored in the selected result register 10 to the adder circuit 6.

[0022] 2 is a diagram showing an example configuration of potentiometer 200. Potentiometer 200 may be interpreted as a device that measures or detects the rotation angle of a rotating body, conductor D. Potentiometer 200 may include a film resistor R, a contact S extending from film resistor R to conductor D, and signal terminals T1, T2.

[0023] The film resistor R may be considered a C-shaped resistor with a portion of the annular member removed. A signal terminal T1 may be connected to one end of the film resistor R, and a signal terminal T2 may be connected to the other end of the film resistor R. In FIG. 2, a contact point S is in contact with the film resistor R near its center. The film resistor R, the contact point S, and the conductor D form a path for a current to flow when a voltage VDD is applied to the potentiometer 200.

[0024] A measuring terminal DT may be connected to one end of the rod-shaped conductor D. The measuring terminal DT may also be connected to the first switching unit SW1. When the voltage VDD in the first direction A is selected, the first "input terminal (1)" of the multiple input terminals 1 shown in FIG. 1 may be selected, and when the voltage VDD in the second direction B is selected, the second "input terminal (2)" of the multiple input terminals 1 may be selected.

[0025] A first switching unit SW1 may be connected to the signal terminal T1. A second switching unit SW2 may be connected to the signal terminal T2. The first switching unit SW1 and the second switching unit SW2 may switch their contacts in response to a control signal CS shown in FIG. 1. Specifically, the contacts may be switched in response to information DI included in the control signal CS. The information DI may be interpreted as a signal indicating the direction of the voltage VDD.

[0026] The information DI may include voltage information that sets the first switch SW1 side to +X [V] and the second switch SW2 side to 0 [V]. When a control signal CS including this information is input to the potentiometer 200, it may be interpreted that the voltage VDD in the first direction A is applied to the potentiometer 200.

[0027] The information DI may include voltage information that sets the first switch SW1 side to 0 [V] and the second switch SW2 side to +X [V]. When a control signal CS including this information is input to the potentiometer 200, it may be interpreted that the voltage VDD in the second direction B is applied to the potentiometer 200.

[0028] In the present disclosure, in order to reduce the error in the rotation angle detected by the potentiometer 200, the direction of the voltage VDD may be alternately changed at each sampling timing of the AD conversion circuit 3, and the analog value may be measured at least twice.

[0029] In the following, a case will be described in which the direction of the voltage VDD is alternately reversed, for example, at each sampling timing of the AD conversion circuit 3, thereby measuring an analog value corresponding to the rotation angle of the conductor D multiple times.

[0030] When the voltage VDD in the first direction A is selected by the information DI, the relationship between the analog quantity ADCv and the voltage VDD can be expressed by equations (1) and (2) when the point where the voltage VSS applied to the film resistor R is set to 0°. α can be interpreted as the rotation angle from the signal terminal T1 to the voltage VSS, and β as the rotation angle from the signal terminal T2 to the voltage VSS. ADCv = α / (α + β) × VDD (1) ADCv / VDD=α / (α+β) (2)

[0031] The relationship between the analog quantity ADCv and the voltage VDD when a positive noise voltage (+ε) is applied to the voltage VDD can be expressed by equations (3) to (6). ε can be interpreted as the noise voltage added to the voltage VDD. κ can be interpreted as the degree of influence of the noise voltage on the voltage VDD. ADCv / VDD=(ADCv+κ) / (VDD+ε)···(3) ADCv×(VDD+ε) / VDD=ADCv+κ···(4) ADCv+ε / VDD=ADCv+κ (5) κ=ε / VDD (6)

[0032] When the voltage VDD in the second direction B is selected by the information DI, when the point of the voltage VSS applied to the film resistor R is set to 0°, the relationship between the analog quantity ADCv and the voltage VDD can be expressed by equation (7). ADCv = β / (α + β) × VDD (7)

[0033] The relationship between the analog amount ADCv and the voltage VDD when a positive noise voltage (+ε) is applied to the voltage VDD can be expressed by equations (8) to (11). ADCv / VDD=(ADCv+κ) / (VDD+ε)···(8) ADCv×(VDD+ε) / VDD=ADCv+κ···(9) ADCv+ε / VDD=ADCv+κ (10) κ=ε / VDD (11)

[0034] According to the above equations (6) and (11), when a positive noise voltage is added to the voltage VDD, if the voltage VDD in the first direction A is selected by the information DI, the voltage is affected in a direction that increases the rotation angle α (decreases the rotation angle β). Also, if the voltage VDD in the second direction B is selected by the information DI, the voltage is affected in a direction that increases the rotation angle β (decreases the rotation angle α).

[0035] Therefore, the influence of voltage noise when measuring the rotation angle can be canceled by changing the direction of the voltage applied to the film resistor R when measuring the rotation angle between two directions, positive and negative, i.e., the first direction A and the second direction B. Furthermore, since the rotation angle to be measured also oscillates, it is practically desirable to measure the rotation angle multiple times and calculate the rotation angle from the average value.

[0036] Next, the operation of the analog-to-digital conversion device 100 will be described with reference to Fig. 3 to Fig. 6. Fig. 3 is a flowchart for explaining the operation of the analog-to-digital conversion device 100. Fig. 4 to Fig. 6 are diagrams for explaining the operation of the analog-to-digital conversion device 100.

[0037] In step S1, the analog-to-digital converting apparatus 100 may clear the registers, flags, and counters, that is, clear all the result registers 10, completion flags, and number counter values ​​corresponding to the input terminals 1 in the same group.

[0038] In step S2, the analog-to-digital converting apparatus 100 may select an incomplete terminal in the group, that is, an input terminal 1 whose completion flag is cleared.

[0039] In step S3, the ADC value (digital value) of the selected input terminal 1 may be obtained.

[0040] In step S4, the analog-to-digital conversion device 100 may add the ADC value to the result register 10 corresponding to the input terminal 1. Specifically, the analog-to-digital conversion device 100 (1) performs sampling at the voltage VDD in the first direction A and adds the ADC value to the result register 10 corresponding to the input terminal 1, and (2) performs sampling in the second direction B and adds the ADC value to the result register 10 corresponding to the input terminal 1. The analog-to-digital conversion device 100 may repeat the sampling of (1) and (2) and the addition of the ADC value to the result register 10 an average number of times while alternately changing the direction of the voltage VDD for each sampling timing of the AD conversion circuit 3.

[0041] In step S5, the analog-to-digital converting apparatus 100 may enable the completion flag of the corresponding input terminal 1.

[0042] In step S6, the analog-to-digital converting device 100 may determine whether the number of times counter value is equal to the average sample number. If the number of times counter value is not equal to the average sample number, the analog-to-digital converting device 100 may perform the process of step S8. If the number of times counter value is equal to the average sample number, the analog-to-digital converting device 100 may perform the process of step S7.

[0043] In step S7, the analog-to-digital conversion device 100 may divide the value of the corresponding result register 10 by the average sample number. Specifically, the analog-to-digital conversion device 100 calculates the average value by dividing the value of the result register 10 selected according to the value of the control signal CS by the number of samples. In Fig. 4, the sampling points when the voltage VDD in the first direction A and the second direction B is alternately changed for each sampling timing of the AD conversion circuit 3 are indicated by circles.

[0044] In step S8, the analog-digital converting apparatus 100 may determine whether the completion flags of all terminals (input terminals 1) in the group are valid. If the completion flags are not valid, the analog-digital converting apparatus 100 may execute the processes of step S2 and thereafter. If the completion flags are valid, the analog-digital converting apparatus 100 may execute the process of step S9.

[0045] In step S9, the analog-to-digital converting device 100 may clear the completion flags corresponding to all terminals (input terminal 1) in the group and increment the number counter value.

[0046] In step S10, the analog-to-digital conversion device 100 may determine whether the number of times counter value is equal to the average sample number. If the number of times counter value is not equal to the average sample number, the analog-to-digital conversion device 100 may perform the processes of step S2 and thereafter. If the number of times counter value is equal to the average sample number, the analog-to-digital conversion device 100 may perform the process of step S11.

[0047] In step S11, the analog-to-digital converting device 100 may obtain the rotation angle of the potentiometer 200 from the average value in the first direction A and the average value in the second direction B. This completes the series of processes.

[0048] Figure 5 shows the results of noise calculations using these averaging processes, i.e., the evaluation results of the effects of low-frequency noise and high-frequency noise. The vertical axis of Figure 5 represents noise level, and the horizontal axis of Figure 5 represents time. The dashed waveform represents high-frequency noise, the dashed-dotted waveform represents low-frequency noise, and the solid waveform represents observed noise (low-frequency noise superimposed with high-frequency noise). Average noise a represents the average noise of 50 samples in a comparative example described below, and average noise b represents the average noise of 50 samples in analog-to-digital conversion device 100.

[0049] 6 shows the amount of noise according to an embodiment of the present disclosure (analog-to-digital conversion device 100) and the amount of noise according to a comparative example. The amount of noise according to the embodiment of the present disclosure is improved to about 1 / 53 of the amount of noise according to the comparative example. In this way, the embodiment of the present disclosure can significantly improve the effect of reducing low-frequency noise.

[0050] (Comparative Example) Fig. 7 is a diagram showing the configuration of an analog-digital conversion device 100A according to a comparative example. The analog-digital conversion device 100A according to the comparative example differs from the analog-digital conversion device 100 shown in Fig. 1 in that, in the analog-digital conversion device 100A, information DIa is input to the potentiometer 200 instead of information DI. Information DIa may be interpreted as information instructing that N samplings be performed in the first direction A, and then N samplings be performed in the second direction B, and these operations be repeated.

[0051] Next, the operation of the analog-to-digital conversion device 100A will be described with reference to Figures 8 and 9. Figure 8 is a flowchart for explaining the operation of the analog-to-digital conversion device 100A. Figure 9 is a diagram for explaining the operation of the analog-to-digital conversion device 100A.

[0052] In step S1, the analog-to-digital converting device 100A may clear registers, flags, and counters, that is, clear all result registers 10, completion flags, and number counter values ​​corresponding to input terminals 1 in the same group.

[0053] In step S2, the analog-to-digital converting device 100A may select an incomplete terminal in the group, that is, an input terminal 1 whose completion flag is cleared.

[0054] In step S3, the analog-to-digital converting device 100A may obtain an ADC value (digital value) of the selected input terminal 1.

[0055] In step S4A, the analog-to-digital conversion device 100A may add the ADC value to the result register 10 corresponding to the input terminal 1. Specifically, the analog-to-digital conversion device 100A (1) performs multiple consecutive samples using the voltage VDD in the first direction A and adds the ADC value to the result register 10 corresponding to the input terminal 1, and (2) then performs multiple consecutive samples using the voltage VDD in the second direction B and adds the ADC value to the result register 10 corresponding to the input terminal 1.

[0056] In step S50, the analog-to-digital converting device 100A may increment the number counter value.

[0057] In step S60, the analog-to-digital conversion device 100A may determine whether the number of times counter value is equal to the average sample number. If the number of times counter value is not equal to the average sample number, the analog-to-digital conversion device 100A may perform the processes of step S2 and thereafter. If the number of times counter value is equal to the average sample number, the analog-to-digital conversion device 100A may perform the process of step S70.

[0058] In step S70, the analog-to-digital converting device 100A may divide the value of the corresponding result register 10 by the average sample number. Specifically, the analog-to-digital converting device 100A may perform N samplings in the first direction A to obtain an average value, and perform N samplings in the second direction B to obtain an average value.

[0059] 9, the circles indicate sampling points where sampling is performed N times in each of the first direction A and the second direction B. If the average value in the first direction A is 1 / 3×VDD and the average value in the second direction B is 1 / 3×VDD, the rotation angle α can be calculated as α=2 / 3×π=120°.

[0060] In step S80, the number counter value may be cleared, and the completion flags corresponding to all terminals (input terminal 1) in the group may be set to valid.

[0061] In step S90, the analog-to-digital converting device 100A may determine whether the completion flags of all terminals (input terminal 1) are valid. If the completion flags of all terminals (input terminal 1) are not valid, the processing of step S2 and subsequent steps may be executed. If the completion flags of all terminals (input terminal 1) are valid, the processing of step S100 may be executed.

[0062] In step S100, the analog-to-digital converting device 100A may obtain the rotation angle of the potentiometer 200 from the average value in the first direction A and the average value in the second direction B. This completes the series of processes.

[0063] (Actions and Effects) As shown in FIG. 5, when used in a low-frequency noise environment, the analog-to-digital conversion device 100A according to the comparative example cannot remove low-frequency noise. A conventional solution to this problem would be to set multiple parameters of the measurement target to be quantified and assign a separate AD conversion circuit 3 to each parameter. However, this would increase the number of AD conversion circuits 3, which could increase the manufacturing cost of the analog-to-digital conversion device 100A. Furthermore, the configuration of the analog-to-digital conversion device 100A could become complex. Furthermore, if one of the multiple AD conversion circuits 3 fails, it could take a significant amount of time to identify the failed AD conversion circuit 3.

[0064] In contrast, the analog-digital conversion device 100 according to the embodiment of the present disclosure can cancel the influence of voltage noise (especially low-frequency noise) when measuring the rotation angle by measuring the analog value at least twice while alternately changing the voltage VDD in the first direction A and the second direction B for each sampling timing of the AD conversion circuit 3. This makes it possible to reduce the influence of noise even when using a single AD conversion circuit 3, thereby significantly reducing the manufacturing cost of the analog-digital conversion device 100. Furthermore, the structure of the analog-digital conversion device 100 is simplified, significantly improving the reliability of the analog-digital conversion device 100 and enabling the analog-digital conversion device 100 to be made more compact.

[0065] In addition, the following supplementary notes are provided in relation to the above description.

[0066] (Appendix 1) a plurality of terminals for inputting a plurality of analog values ​​indicating specific rotation angles of the object to be measured in chronological order; a selection circuit that selects one of the plurality of terminals; a conversion circuit that converts the plurality of analog values ​​selected by the selection circuit into a plurality of digital values; an average value calculation circuit that calculates an average value of the plurality of digital values ​​converted in time series within a specific range; a control circuit that executes control to alternately change the direction of a voltage applied to the object to be measured between a first direction and a second direction opposite to the first direction at each sampling timing of the conversion circuit when the conversion circuit converts the plurality of analog values ​​into the plurality of digital values; An analog-to-digital conversion device comprising:

[0067] (Appendix 2) The analog-to-digital conversion device described in Appendix 1, wherein the average value calculation circuit adds the plurality of digital values ​​sampled when the direction of the voltage is the first direction and the second direction to a register, and calculates the average value of each of the values ​​in the first direction and the second direction by dividing each of the values ​​in the first direction and the second direction added to the register by a specific number of times.

[0068] (Appendix 3) 3. The analog-to-digital conversion device according to claim 2, wherein the average value calculation circuit calculates the rotation angle of the object to be measured based on the average values ​​of the values ​​in the first direction and the second direction. [Explanation of symbols]

[0069] 1 input terminal 2 Input terminal selection circuit 3 AD conversion circuit 4 Control Circuit 5 Average value calculation circuit 6 Adding Circuit 7 Division circuit 8 Comparison circuit 9 Number of times counter 10 Result Registers 11 Register output selection circuit 100, 100A analog-to-digital conversion device 200 potentiometer α, β rotation angles a, b Average noise A 1st direction ADCv Analog Value B Second direction CS control signal D conductor DI, DIa information DT measurement end R film resistance SW1 First switching unit SW2 Second switching section T1, T2 signal terminals VDD, VSS voltage

Claims

1. a plurality of terminals for inputting a plurality of analog values ​​indicating specific rotation angles of the object to be measured in chronological order; a selection circuit that selects one of the plurality of terminals; a conversion circuit that converts the plurality of analog values ​​selected by the selection circuit into a plurality of digital values; an average value calculation circuit that calculates an average value of the plurality of digital values ​​converted in time series within a specific range; a control circuit that executes control to alternately change the direction of a voltage applied to the object to be measured between a first direction and a second direction opposite to the first direction at each sampling timing of the conversion circuit when the conversion circuit converts the plurality of analog values ​​into the plurality of digital values; An analog-to-digital conversion device comprising:

2. 2. The analog-to-digital conversion device according to claim 1, wherein the average value calculation circuit adds the plurality of digital values ​​sampled when the direction of the voltage is the first direction and the second direction to a register, and calculates the average value of each of the values ​​in the first direction and the second direction by dividing the values ​​in the first direction and the second direction added to the register by a specific number of times.

3. 3. The analog-to-digital conversion device according to claim 2, wherein the average value calculation circuit calculates the rotation angle of the object to be measured based on the average values ​​of the values ​​in the first direction and the second direction.

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