JP2012177614A - Acceleration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration detector whose detection accuracy is improved by reducing or eliminating an error even when voltages to be applied to an acceleration sensor and an AD converter do not match to each other.SOLUTION: An acceleration detector has: an acceleration sensor 1 which outputs detection voltage Vdat corresponding to acceleration; an AD conversion part 32 which performs analog/digital conversion to the detection voltage Vdat to be output by the acceleration sensor 1 to output a converted value; sensor voltage estimation means 5 for detecting voltage Vof a sensor power supply 30 which applies voltage to the acceleration sensor 1, and estimates sensor voltage Vto be applied to the acceleration sensor 1 based on the detected power supply voltage V; and a correction part 6 which holds correlation information 6a between voltage and gain in the preset acceleration sensor or an AD converter, and corrects the value to be output from the AD conversion part 32 by using the correlation information 6a so that the value becomes a value converted by a gain according to the sensor voltage Vestimated by the sensor voltage estimation means 5.

Description

  The present invention relates to an acceleration detection device with optimized detection accuracy.

  As illustrated in Patent Document 1, an acceleration detection device for detecting acceleration is obtained by converting an acceleration sensor that outputs a detection voltage corresponding to acceleration, and analog / digital conversion of the detection voltage output from the acceleration sensor, It is usual to have an AD converter that outputs a value, and high detection accuracy is required.

JP 2000-137039 A

  Although an approach to improve the resolution to improve the detection accuracy is generally taken, there are various factors other than the resolution, such as individual variation, temperature variation, and power supply variation, as factors that affect the detection accuracy. If compensation for these is not taken into account, it cannot be said that the improvement of detection accuracy is truly pursued. Among these, the power source variation factor is dominant except for the resolution. That is, the acceleration sensor outputs an output voltage with a gain corresponding to the sensor voltage applied by the power supply, and the AD conversion unit AD converts the detection voltage with a gain corresponding to the AD voltage applied by the power supply. If there is a power supply variation that the sensor voltage applied to the sensor does not match the AD voltage applied to the AD converter, the gains do not match and an error occurs, resulting in a decrease in detection accuracy. .

  The present invention has been made paying attention to such a problem, and its purpose is to detect without reducing or eliminating errors even when the voltages applied to the acceleration sensor and the AD converter do not match. It is an object of the present invention to provide an acceleration detection device with improved accuracy.

  In order to achieve this object, the present invention takes the following measures.

  That is, the acceleration detection device of the present invention includes an acceleration sensor that outputs a detection voltage corresponding to acceleration with a gain corresponding to a sensor voltage applied by a power supply, and an output of the acceleration sensor with a gain corresponding to an applied AD voltage. An analog-to-digital converter that outputs a value obtained by performing analog / digital conversion on the detected voltage; and a sensor that detects a voltage of a power source to be applied to the acceleration sensor and is applied to the acceleration sensor based on the detected power source voltage. The sensor voltage estimation means for estimating the voltage and the correlation information between the voltage and the gain in the preset acceleration sensor or AD converter are held, and converted by the gain corresponding to the sensor voltage estimated by the sensor voltage estimation means. A correction unit that corrects the value output from the AD conversion unit using the correlation information so as to be a value. To.

  In this way, the sensor voltage estimation means detects the voltage of the power supply applied to the acceleration sensor, estimates the sensor voltage applied to the acceleration sensor based on the detected power supply voltage, and the correction unit sets the preset acceleration sensor. Alternatively, the correlation information between the voltage and the gain in the AD converter is held, and the value output from the AD conversion unit is corrected using the correlation information so that the value is converted with the gain according to the estimated sensor voltage. Therefore, even if the sensor voltage and AD voltage do not match, the corrected value becomes a value converted with a gain corresponding to the sensor voltage applied to the acceleration sensor, and the detection accuracy is improved by reducing or eliminating the error. It becomes possible to make it.

  In order to further improve the detection accuracy, the sensor voltage estimation means has voltage drop information related to voltage drop due to resistance or impedance on the path from the power source to the acceleration sensor, and is obtained based on the voltage drop information. It is preferable that a value obtained by subtracting a voltage drop value from the detected power supply voltage is estimated as the sensor voltage.

  Even if a short circuit occurs in the path between the power supply and the acceleration sensor, in order to avoid the power interruption of the entire apparatus, a voltage is applied to the AD converter separately from the power supply to which the voltage is applied to the acceleration sensor. It is desirable to provide an AD power supply.

  In order to be able to determine whether a short circuit has occurred in a path such as a harness portion between the power source and the acceleration sensor by distinguishing it from other faults, the acceleration sensor and the power source are connected based on the detected power source voltage. It is effective to provide a short-circuit determination unit that determines whether or not a short-circuit has occurred in the path between them.

  As described above, according to the present invention, the sensor voltage applied to the acceleration sensor is estimated based on the voltage of the power supply applied to the acceleration sensor, and is converted to a value corresponding to the estimated sensor voltage. Since the value output from the AD converter is corrected using the correlation information between the voltage and gain in the acceleration sensor or AD converter, the sensor voltage and the AD voltage applied to the AD converter do not match. However, the corrected detection value becomes a value converted by a gain corresponding to the sensor voltage applied to the acceleration sensor, and the detection accuracy can be improved by reducing or eliminating the error.

The block diagram which shows typically the acceleration detection apparatus which concerns on one Embodiment of this invention. The more detailed block diagram of the acceleration detection apparatus which concerns on this embodiment. The block diagram which shows typically the acceleration detection apparatus of this embodiment from a viewpoint different from FIG. The figure which shows the power supply part of this embodiment typically. The block diagram which shows typically the acceleration detection apparatus which concerns on other embodiment of this invention. The figure which shows the conventional acceleration detection apparatus typically.

  Hereinafter, an acceleration detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the acceleration detection apparatus includes an acceleration sensor 1 and a controller 3 that supplies power to the acceleration sensor 1 and inputs a detection voltage Vdat output from the acceleration sensor 1.

The acceleration sensor 1 is electrically connected to the controller 3 via the connector portion 2a and the harness portion 2b, and is based on the sensor voltage _VSE applied from the controller 3, and supports acceleration with a gain corresponding to the sensor voltage _VSE. And an acceleration detection device 10 that outputs a detection voltage Vdat.

The controller 3 includes a sensor power source 30 for supplying power to the acceleration sensor 1, and an AD conversion unit that converts the detected voltage Vdat input from the acceleration sensor 1 via the analog interface unit 31 from analog to digital and outputs the converted value. 32 and an AD power source 33 that supplies power to the analog interface unit 31 and the AD conversion unit 32. The AD conversion unit 32 performs conversion with a gain corresponding to the AD voltage V _AS based on the AD voltage V _AS applied by the AD power supply 33. In the figure, a ground V _SG on the sensor power source 30 side and a ground V _AG on the AD power source 33 side are connected. The AD power source 33 is also a main power source that supplies power to a main device including a CPU (not shown).

In addition to the above configuration, as shown in FIG. 2, the power supply voltage detecting means 4 for detecting the voltage (sensor power supply voltage V _SO ) of the sensor power supply 30 that applies a voltage to the acceleration sensor 1, and the power supply detected by the power supply voltage detecting means 4 The sensor voltage estimation means 5 for estimating the sensor voltage _VSE applied to the acceleration sensor 1 based on the voltage (sensor power supply voltage V _SO ), and the correlation between the preset voltage and gain in the acceleration sensor 1 or AD converter 32. The value output from the AD conversion unit 32 that converts the detected voltage Vdat so as to have a value converted by a gain corresponding to the sensor voltage _VSE estimated by the sensor voltage estimation means 5 is stored in the correlation information. A correction unit 6 that performs correction using 6a is provided.

Specifically, the following means are taken in order to convert the detected voltage Vdat from the acceleration sensor 1 from analog to digital. That is, as shown in FIG. 2, the detection voltage Vdat from the acceleration sensor 1 is input to the interface circuit unit 31a (gain: Gs), and the level conversion acceleration signal (Vdat · Gs) is output from the interface circuit unit 31a. The level conversion acceleration signal (Vdat · Gs) is converted by the AD converter 32 with a gain (Admax / V _AS ) corresponding to the AD voltage V _AS applied from the AD power supply 33 and converted (Vdat · Gs · Admax / V _AS ) is output.

The power supply voltage detection means 4 detects the voltage (sensor power supply voltage _VSO ) of the sensor power supply 30 that applies a voltage to the acceleration sensor 1, and is specifically configured as follows. That is, as shown in FIG. 2, sensor power supply voltage _{V SO} voltage conversion unit 40: input to (gain Gv), and outputs a divided sensor supply voltage _(V SO · Gv) from the voltage conversion unit 40, this amount converted by pressure sensor supply voltage _(V SO · Gv) was according to AD voltage _{V aS} applied from AD power source 33 in the AD converter 41 for the sensor supply voltage gain (Admax _{/ V aS),} sensor power supply voltage detection value to output _{(V SO · Gv · Admax /} V AS). Also, a predetermined reference voltage Vref is output from the reference voltage generator 42, and the reference voltage Vref is gained according to the AD voltage V _AS applied from the AD power supply 33 in the reference voltage AD converter 43 (Admax / V _AS ), and a reference voltage detection value (Vref · Admax / V _AS ) is output. The calculated sensor power supply voltage detection value ratio _{(V SO · Gv · Admax /} V AS) the gain (1 / Gv) AD voltage and sensor supply voltage multiplied by _{(V SO · Admax / V AS} ), the division is divided by the ratio of the AD voltage and sensor supply voltage _{(V SO · Admax / V aS} ) the reference voltage detection value (Vref · Admax _{/ V aS)} in vessel 44, the ratio of the sensor power supply voltage and a reference voltage _{(V SO} / calculates Vref), determining the sensor power supply voltage V _SO by multiplying a predetermined reference voltage value Vref by the multiplier 45 to the ratio of the sensor power supply voltage and a reference voltage (V _{SO /} Vref). This is because, when the AD voltage V _AS varies, the value after analog / digital conversion is not always a correct value, so that a known reference with the same gain as that used when converting the sensor power supply voltage _VSO is used. The true sensor power supply voltage _VSO is obtained by performing analog / digital conversion on the voltage value Vref and dividing the respective conversion results to cancel an error caused by a variable gain (power supply variation).

The sensor voltage estimation means 5 estimates the sensor voltage V _SE applied to the acceleration sensor 1 based on the power supply voltage (sensor power supply voltage V _SO ) detected by the power supply voltage detection means 4. Voltage drop information 50 relating to voltage drop due to resistance or impedance on the path leading to, and a value (V _SO −) obtained by subtracting the voltage drop value Dr obtained based on the voltage drop information 50 from the power supply voltage (sensor power supply voltage V _SO ). Dr) is estimated as the sensor voltage _VSE . Of course, the detected power supply voltage (sensor power supply voltage _VSO ) may be estimated as the sensor voltage _VSE as it is. Specifically, the voltage drop information 50 is obtained when the one-way (one-way) wiring / connector combined resistance from the sensor power supply 30 to the acceleration sensor 1 is Rh, and the current supplied to the acceleration sensor 1 is Is. This is information related to the expression expressed by the voltage drop value Dr = Rh × Is. The drop correction unit 51 holds the voltage drop information 50 described above, calculates the voltage drop value Dr using the above formula, and drops the voltage from the power supply voltage (sensor power supply voltage _VSO ) detected by the power supply voltage detection means 4. value obtained by subtracting the _(V SO -Dr) is the sensor voltage _{V SE} in the subtracter 52 the value Dr. In this embodiment, the current Is supplied to the acceleration sensor 1 is stored as an average value measured in advance, but the voltage drop value Dr is calculated using a current value that is detected as needed by providing a current detector. It may be configured. If comprised in this way, it will become possible to improve detection accuracy more. In the present embodiment, the voltage drop information 50 is an expression for calculating the voltage drop value Dr. However, the voltage drop value Dr may be stored in a table in advance.

The correction unit 6 stores (holds) correlation information 6 a such as a relationship graph between a supplied voltage and a gain, which is a specification of the acceleration sensor 1, and corresponds to the sensor voltage V _SE estimated by the sensor voltage estimation unit 5. The value (Vdat · Gs · Admax / V _AS ) output from the AD conversion unit 32 is corrected using the correlation information 6a so that the value converted by the gain is obtained. In the present embodiment, assuming that the AD voltage V _AS is constant, correlation information 6a in which a correction value is associated with each sensor voltage V _SE is defined, and a correction value corresponding to the sensor voltage V _SE in the correlation information 6a is defined. This is obtained by multiplying the value (Vdat · Gs · Admax / V _AS ) output from the AD converter 32 by the correction value in the multiplier 6b. In the present embodiment stores the correction values in the table in association with each sensor voltage V _SE, but by using a correction value corresponding to the estimated sensor voltage V _SE, calculating a correction value based on the sensor voltage V _SE You may comprise so that it may calculate by. Note that a means for detecting the AD voltage V _AS may be provided separately, and correction may be performed using the detected AD voltage V _AS , the estimated sensor voltage V _SE, and the correlation information 6a. Further, in this embodiment, the relationship between the power source and the gain in the acceleration sensor is held as the correlation information, but the relationship between the voltage and the gain in at least one of the acceleration sensor 1 or the AD conversion unit 32 is held. Also good.

  With this configuration, the sensor voltage is 5.0 [V], the voltage varies from ± 75% from 4.75 [V] to 5.25 [V], and the typical detection gain is 1.000 [V / G]. , Even if it varies in the range of 0.906 [V / G] at 4.75 [V] and 1.094 [V / G] at 5.25 [V], this can be corrected appropriately to improve detection accuracy It becomes possible.

  In the prior art, as shown in FIG. 6, a voltage is applied from the main power supply 1033 provided on the controller 1003 side to the acceleration sensor 1001 via the harness section 1002b, and the analog circuit section 1034 and the digital circuit section from the same main power supply 1033 The acceleration detection device was configured to supply power to 1035. In this case, since the analog circuit unit 1034, the digital circuit unit 1035, and the external acceleration sensor 1001 are all powered by a single circuit, the output power is large and a switching power source is used to reduce loss. However, in an application example in which switching noise occurs and there is an advanced EMC requirement (for example, the case where the acceleration detection device of the present embodiment is applied as a vibration detection unit that detects vibration in an automobile vibration control device). In some cases, noise countermeasure parts may be required separately. In this configuration, since EMC noise is mixed into the internal power supply from the external harness portion 1002b, a filter branch (LC) using a coil is provided to reduce the influence of the EMC noise, but this filter branch (LC) This device is expensive, which increases the manufacturing cost. Furthermore, in order to prevent circuit damage from an external surge, it is necessary to arrange an overvoltage clamp circuit (CL) using a Zener diode or the like at the power supply output terminal separately from the power supply.

Therefore, in the present embodiment, as shown in FIG. 3, in addition to the sensor power supply 30 that applies a voltage to the acceleration sensor 1, a voltage is applied to a power supply that supplies power to the analog circuit section 34 and the digital circuit section 35, that is, an AD conversion section. An AD power supply 33 which is also a main power supply is provided. As shown in FIG. 4, these power sources use a dropper type power source composed of a three-terminal regulator instead of a switching type. Further, as shown in FIG. 3, a short circuit determination for determining whether or not a short circuit has occurred in the path between the acceleration sensor 1 and the power supply (sensor power supply 30) based on the detected power supply voltage (sensor power supply voltage V _SO ). A portion 36 is provided. Specifically, the short circuit determination unit 36 determines that a short circuit has occurred when the detected power supply voltage (sensor power supply voltage _VSO ) is equal to or lower than a predetermined value, and the detected power supply voltage (sensor power supply voltage _VSO ) is predetermined. When the value is exceeded, it is determined that a short circuit has not occurred.

  With this configuration, even if a power supply short-circuit abnormality occurs due to a short circuit of the external harness unit 2b or the like, only the sensor power supply 30 hangs down, so that the digital circuit unit 35 and the analog circuit unit 34 The power supply does not hang down, and it is possible to detect whether or not a short circuit has occurred by distinguishing from other faults by the short circuit determination unit 36. In addition, since the sensor power supply 30 and the AD power supply 33 are separated, there is no need to provide a filter branch (LC) with a coil between the power supplies 30 and 33, so that the cost can be reduced and the external power supply can be reduced. It becomes strong against noise, and furthermore, since the power source is separated, it is easy to dissipate heat. Providing multiple power supply circuits seems to increase costs, but providing multiple power supply circuits is less expensive than providing a filter branching coil, so the total cost can be reduced. Become. Furthermore, since the power supply is changed from the conventional switching method to the dropper method, the switching noise can be reduced and the EMC noise level generated inside the controller can be significantly reduced. Accordingly, it is possible to reduce the manufacturing cost by omitting switching noise countermeasure components. In particular, when the power source is a dropper type as in this embodiment, as shown in FIG. 4, it is common to provide a clamp diode for preventing reverse voltage between the input and output of the dropper circuit. Even if the voltage on the output load side rises for some reason, a path for charging on the input power source side is generated, and the circuit is protected from overvoltage. Therefore, when the power source is of a dropper type, it is not necessary to newly provide an overvoltage clamp circuit LC shown in FIG. 6 separately from the power source, and the cost can be reduced.

As described above, the acceleration detecting device of the present embodiment, the acceleration sensor 1 for outputting a detection voltage Vdat corresponding to acceleration gain corresponding to the sensor voltage V _SE applied by a power supply (sensor power supply 30), is applied A value (Vdat · Gs · Admax / V _AS ) obtained by converting the detected voltage Vdat output from the acceleration sensor 1 by analog / digital conversion with a gain (Admax / V _AS ) corresponding to the AD voltage V _AS to be output. The voltage (sensor power supply voltage V _SO ) of the converter 32 and the power supply (AD power supply 33) for applying a voltage to the acceleration sensor 1 is detected and applied to the acceleration sensor 1 based on the detected power supply voltage (sensor power supply voltage V _SO ). a sensor voltage estimation unit 5 for estimating the that sensor voltage V _SE, holds correlation information 6a between voltage and gain in a preset acceleration sensor or AD converter, Capacitors so that the voltage estimated transformed values with a gain corresponding to the sensor voltage V _SE of the estimator 5, the value output from the AD converter 32 and correlation information 6a to (Vdat · Gs · Admax / V AS) And a correction unit 6 that corrects using the correction unit 6.

Thus, the sensor voltage estimation means 5 detects the voltage of the sensor power supply 30 to which the voltage is applied to the acceleration sensor 1, estimates the sensor voltage _VSE applied to the acceleration sensor 1 based on the detected sensor power supply voltage _VSO , The correction unit 6 holds correlation information 6a between a voltage and a gain in a preset acceleration sensor or AD converter, and performs AD conversion so that a value converted with a gain corresponding to the estimated sensor voltage _VSE is obtained. since the value output from the section 32 _{(Vdat · Gs · Admax / V} aS) corrected using the correlation information 6a, even when the sensor power supply voltage _{V sO} and AD voltage _{V aS} does not match, the corrected The value becomes a value converted by a gain corresponding to the sensor voltage _VSE applied to the acceleration sensor 1, and the detection accuracy can be improved by reducing or eliminating the detection error.

Furthermore, in this embodiment, the sensor voltage estimation means 5 has voltage drop information 50 regarding voltage drop due to resistance or impedance on the path from the power source (sensor power source 30) to the acceleration sensor 1, and based on the voltage drop information 50. since the resulting voltage drop value Dr of the detected power supply voltage value obtained by subtracting from the (sensor power supply voltage V _sO) to (V _{sO -Dr)} estimated as the sensor voltage V _SE, voltage according to the resistance or impedance of the path such harnesses drop In consideration of the drop, it becomes possible to further improve the detection accuracy.

  Furthermore, in the present embodiment, since the AD power supply 33 for applying a voltage to the AD conversion unit 32 is provided separately from the power supply (sensor power supply 30) for applying a voltage to the acceleration sensor 1, the acceleration sensor 1, the sensor power supply 30, and the like. Even when a short circuit occurs in the harness portion 2b between them, it is possible to avoid the power shutdown of the AD power supply 33 on the controller 3 side and the power shutdown of the entire system. Further, since the sensor power supply 30 and the AD power supply 33 are separated, there is no need to provide a filter branch (LC) by a coil between the power supplies 30 and 33, and the cost can be reduced and external noise can be reduced. Will also be solid.

In addition, in the present embodiment, the short-circuit determining unit 36 that determines whether or not a short circuit has occurred in the path between the acceleration sensor 1 and the power source (sensor power source 30) based on the detected power source voltage (sensor power source voltage V _SO ). Therefore, it is possible to determine whether or not a short circuit has occurred in an external path such as a harness part by distinguishing it from other faults.

  As mentioned above, although one Embodiment of this invention was described, the specific structure of each part is not limited only to embodiment mentioned above.

  For example, in the present embodiment, as shown in FIG. 3, the power supply of the analog circuit unit 34 and the digital circuit unit 35 is shared, but as shown in FIG. In addition to 137, a digital power source 138 that supplies power to the digital circuit unit 35 may be provided to separate the power sources.

  In addition, various modifications can be made without departing from the spirit of the present invention.

1 ... acceleration sensor 30 ... sensor power supply (power supply)
32 ... AD converter unit 33 ... AD power supply 36 ... short-circuit determination unit 5 ... sensor voltage estimation unit 50 ... voltage drop information 6 ... correcting section 6a ... correlation information V _{SE ...} sensor voltage Vdat ... detection voltage _{V AS} ... AD voltage _{V SO} ... Power supply voltage (sensor power supply voltage)
Dr: Voltage drop value

Claims (4)

An acceleration sensor that outputs a detection voltage corresponding to acceleration with a gain corresponding to the sensor voltage applied by the power supply;
An AD converter that outputs a value obtained by converting the detection voltage output from the acceleration sensor by analog / digital conversion with a gain corresponding to the applied AD voltage;
Sensor voltage estimation means for detecting a voltage of a power supply to be applied to the acceleration sensor and estimating the sensor voltage applied to the acceleration sensor based on the detected power supply voltage;
Correlation information between voltage and gain in a preset acceleration sensor or AD converter is held, and the AD conversion unit so as to have a value converted with a gain corresponding to the sensor voltage estimated by the sensor voltage estimation means An acceleration detection apparatus comprising: a correction unit that corrects a value output from the image using the correlation information.   The sensor voltage estimation means has voltage drop information related to voltage drop due to resistance or impedance on a path from the power source to the acceleration sensor, and a voltage drop value obtained based on the voltage drop information is determined from the detected power source voltage. The acceleration detection apparatus according to claim 1, wherein a subtracted value is estimated as the sensor voltage.   The acceleration detection apparatus according to claim 1, wherein an AD power supply for applying a voltage to the AD converter is provided separately from a power supply for applying a voltage to the acceleration sensor.   The acceleration detection device according to claim 3, further comprising a short-circuit determination unit that determines whether a short circuit has occurred in a path between the acceleration sensor and the power source based on the detected power supply voltage.

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