JP3923456B2 - Sensor system and sensor signal processing method - Google Patents

Description

  The present invention relates to a sensor system and a sensor signal processing method.

  A sensor system including a sensor unit is used in a wide range of applications. Generally, the sensor system includes a signal processing unit that processes an output signal of the sensor unit.

  Hereinafter, a sensor system used for, for example, an automobile door open / close switch, a seat belt buckle switch, and the like will be described. A signal processing unit to which power is directly supplied from an automobile battery may change the processing operation according to the open / close state of the ignition switch. When the ignition switch is in the OFF state, the battery is not charged. Therefore, the signal processing unit is required to operate with low current consumption for the purpose of preventing the battery from running out. Normally, when the ignition switch is in the OFF state, simpler operation processing is performed than in the ON state to suppress current consumption.

  For example, when the ignition switch is in the OFF state, the sensor system monitors the door open / close switch, and when the switch is in the ON state (the door is in an open state) The buckle switch of the seat belt is monitored, and when the switch is in an ON state (a state where the buckle switch is attached), a detection process of an attachment state of a child restraint system (Child Restraint System: CRS) called a child seat is performed.

  In addition, sensor systems equipped with door open / close switches, buckle switches, etc. as sensors that are part of the sensor unit not only output signal processing during normal operation of the sensor unit, but also output when the sensor unit fails. It is common to perform signal processing together. Here, the failure of the sensor unit means a short circuit with a battery line or a GND line of the sensor wiring, a disconnection of the sensor wiring, or the like.

  The output signal of the sensor unit processed by the signal processing unit of the sensor system described above includes, for example, the state in which the switch harness is short-circuited to the GND line (failure state), switch ON state, switch OFF There are five states: a state where the switch harness is open (failure state), and a state where the switch harness is short-circuited with the battery line (failure state). If the voltage range indicating these states is clear, the signal processing unit By processing the output signal of the sensor unit, it is possible to detect the respective states of the sensor unit during normal operation and at the time of failure.

  By the way, when the signal processing unit detects and processes the output signal at the time of normal operation and failure of the sensor unit as described above, detection using a plurality of comparators increases the number of threshold values. Since it becomes difficult, it is general to detect the output signal voltage of the sensor unit using an A / D converter. In addition, although the A / D converter is independent or incorporated in the microcomputer, the A / D converter has a problem that current consumption is larger than that of the comparator. For example, a switch is used to solve this problem. It is known that the microcomputer's operation mode is switched from the low current operation mode to the normal operation mode by detecting the ON state (see Patent Document 1).

JP 7-56610 A

  However, even if the technique described in Patent Document 1 is used, it is difficult to reduce the current consumption of the signal processing unit when performing output signal processing during normal operation and failure of the sensor unit. In order to reduce the current consumption, a new method is required.

  Accordingly, an object of the present invention is to provide a sensor system and a sensor signal processing method that reduce current consumption of a signal processing unit when performing output signal processing during normal operation and failure of the sensor unit.

The invention of claim 1 is a sensor system comprising a sensor unit and a signal processing unit for processing an output signal of the sensor unit, wherein the signal processing unit performs only output signal processing during normal operation of the sensor unit. performing a first processing operation comprises a normal operation and switches the second processing operation and for outputting the signal processing at the time of fault handling state switching functionality of the sensor unit, the first processing operation, wherein The voltage value of the output signal of the sensor unit is converted into a binary voltage value by a predetermined threshold value, and the second processing operation converts the output voltage of the sensor unit into a digital signal corresponding to the voltage value. It is an operation .

  According to a second aspect of the present invention, in the first aspect of the invention, the processing state switching function switches the processing state so that the time interval of the first processing operation is shorter than the time interval of the second processing operation. It is characterized by being.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the output signal of the sensor unit is an analog voltage signal.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the signal processing unit is connected to a battery and is directly supplied with power from the battery.

According to a fifth aspect of the present invention, in the sensor signal processing method for processing the output signal of the sensor unit, the first processing operation for performing only the output signal processing during the normal operation of the sensor unit, the normal operation of the sensor unit, and Switching to a second processing operation for performing an output signal processing at the time of failure , wherein the first processing operation converts the voltage value of the output signal of the sensor unit into a binary voltage value by a predetermined threshold; The second processing operation is an operation of converting the output voltage of the sensor unit into a digital signal corresponding to the voltage value .

  The invention of claim 7 is characterized in that in the invention of claim 6, the processing operation is switched so that the time interval of the first processing operation is shorter than the time interval of the second processing operation.

According to a seventh aspect of the invention, in the fifth or sixth aspect of the invention, the first processing operation converts the voltage value of the output signal of the sensor unit into a binary voltage value according to a predetermined threshold value. The second processing operation is a result of measuring the voltage value of the output signal of the sensor unit with the signal processing unit. It is the operation | movement processed based on.

  According to the sensor system and the sensor signal processing method of the present invention, the output signal processing at the time of failure of the sensor unit is performed as necessary while mainly performing the processing operation for performing only the output signal processing at the time of normal operation of the sensor unit. Therefore, the current consumption of the signal processing unit can be effectively reduced while the signal processing unit has a function of detecting the failure state of the sensor unit.

  An embodiment of the present invention will be described.

  FIG. 1 is an explanatory diagram schematically showing an example of a sensor system according to an embodiment of the present invention. In FIG. 1, the sensor system 1 includes a sensor unit 2 and a signal processing unit 3.

  The sensor unit 2 includes a sensor 21 and a power source 22. The power source 22 is provided for generating an output signal of the sensor 21. The power supply 22 may be supplied from the power supply signal processing unit 3 via a power supply line or the like, and need not be installed in the sensor unit 2.

  Here, when the output impedance of the sensor 21 is high, by providing a buffer amplifier 23 on the output side of the sensor 21 as shown in FIG. The influence of noise on the input side can be minimized. As a power source for the buffer amplifier 23, the power source 22 connected to the sensor 21 may be shared. For example, another power source may be used such as supplying from the power signal processing unit 3 via a power line or the like. Good.

  The sensor 21 can be configured by using a switch, a variable resistor, a fixed resistor (hereinafter simply referred to as “resistor”) or the like, but any sensor can be used as long as it outputs a voltage. For example, an MR sensor or a Hall sensor which is a non-contact type sensor can be used. Hereinafter, an example in which the sensor 21 is configured using a switch, a variable resistor, a fixed resistor, and the like will be described.

  3 is an explanatory diagram showing an example using a two-pole switch for the sensor 21, FIG. 4 is an explanatory diagram showing an example using a three-pole switch for the sensor 21, and FIG. It is explanatory drawing which shows an example using. In addition, the structure of the sensor 21 in this embodiment is not restricted to the structure illustrated in FIGS.

  In FIG. 3, the sensor 21 is configured by connecting resistors R31, R32, and R33 in series in the order from the power supply side to the ground (hereinafter referred to as GND) side, and connecting a two-pole switch 24 in parallel with the resistor R32. In FIG. 3, the output signal of the sensor 21 is taken from the power supply side (between the resistor R31 and the resistor R32) of the two-pole switch 24, but from the GND side (between the resistor R32 and the resistor R33) of the two-pole switch 24. You may take it out.

  In FIG. 4, the sensor 21 is configured by connecting resistors R41, R42, and R43 in series in order from the power supply side to the ground (hereinafter referred to as GND) side, and connecting the three-pole switch 25 in parallel with the resistor R42.

  In FIG. 5, the sensor 21 is configured by connecting a resistor R51, a variable resistor 26, and a resistor R52 in series from the power supply side to the ground (hereinafter referred to as GND) side. The output signal of the sensor 21 is taken out from the movable part of the variable resistor 26.

  Then, by configuring the sensor 21 as illustrated in FIGS. 3 to 5, it is possible to obtain output signals corresponding to the normal operation and failure of the sensor unit 2.

  The signal processing unit 3 has a function of detecting the output signal of the sensor unit 2. The signal processing unit 3 includes an A / D converter 31, a comparator 32, and an arithmetic unit 33 in order to realize this function. The A / D converter 31 performs an operation of converting the output voltage of the sensor unit 2 into a digital signal corresponding to the voltage value. The comparator 32 converts the output voltage of the sensor unit 2 to the H level (almost power supply) according to a specific threshold value. The voltage level is converted to the L level (substantially the GND level). The computing unit 33 has a function of detecting the output voltage of the A / D converter 31 and the comparator 32 to determine the sensor open / closed state and the failure state.

  The signal processing unit 3 includes input switching means 34 on the input side of the arithmetic unit 33. The input switching means 34 performs a second processing operation for performing an output signal processing at the time of normal operation and failure of the sensor unit 2 while performing mainly output signal processing at the time of normal operation of the sensor unit 2 as necessary. Is provided to do.

  Further, the signal processing unit 3 is provided with a power supply interrupting means 36 for interrupting the power supply 35 connected to the A / D converter 31. The power supply interrupting means 36 is provided to operate the A / D converter 31 only when performing the second processing operation for performing the output signal processing during the normal operation and failure of the sensor unit 2.

  The computing unit 33 has a monitoring state switching function, and the input switching unit 34 and the power supply interrupting unit 36 are controlled by a control signal output from the computing unit 33. The input switching unit 34 and the power supply interrupting unit 36 may be configured using a switch circuit using a semiconductor, a semiconductor switching element, or the like.

  Further, the monitoring state switching function in the computing unit 33 is set to switch the monitoring state so that the time interval of the first processing operation is shorter than the time interval of the second processing operation, so that the A / D converter The operation time 31 can be shortened to the minimum necessary time, and the current consumption of the signal processing unit 3 can be reduced while the signal processing unit 3 has the function of detecting the failure state of the sensor unit 2.

  According to the present embodiment, the current consumption of the signal processing unit 3 can be reduced while the signal processing unit 3 has the function of detecting the failure state of the sensor unit 2. This will be described as a processing method.

  Description will be made mainly with reference to the sensor system of FIG. First, the voltage value of the output signal of the sensor unit 2 is set in a state where the sensor wiring is short-circuited to the GND line in order of increasing voltage (failure state 1), and in a state where the sensor 21 is at a low potential during normal operation (normal state). 1) The sensor 21 has a high potential during normal operation (normal state 2), the sensor wiring is open (failure state 2), and the sensor wiring is short-circuited with the power supply line (failure state 3). The configuration of the sensor 21 is optimized so as to be in a state.

  If the voltage of the power supply 22 is 5V, the voltages of the failure state 1, the normal state 1, the normal state 2, the failure state 2 and the failure state 3 are set to, for example, 0 to 0.75V and 1.25V to 1.75V, respectively. 2.25V-2.75V, 3.25V-3.75V, 4.25V-5V. Of course, the voltage range is not limited to this range.

  Next, the sensor unit 2 and the signal processing unit 3 are connected so that the output signal of the sensor unit 2 is input to the A / D converter 31 and the comparator 32. Hereinafter, the processing operation of the signal processing unit 3 and switching of the processing operation will be described.

  A first processing operation of the signal processing unit 3 will be described. The comparator 32 has a specific threshold value Va (for example, 2V). If the input voltage of the comparator 32 is equal to or higher than the threshold value, a high potential output is output. Output and convert to binary voltage value. The computing unit 33 detects the output of the comparator 32 through the input switching means 34 provided on the input side. In this case, the power supply interrupting means 36 does not supply power from the power supply 35 to the A / D converter 31 to reduce the power consumption of the entire signal processing unit 3.

  The second processing operation of the signal processing unit 3 will be described. When performing output signal processing during normal operation and failure of the sensor unit 2, the power supply interrupting means 36 supplies power from the power supply 35 to the A / D converter 31, and the calculator 33 is provided on the input side thereof. The output of the A / D converter 31 is detected through the input switching means 34.

  For example, the current consumption in the signal processing unit 3 is about several tens of μA in the first processing operation and about 10 to 30 mA in the second processing operation. Since the current consumption is about one hundredth of the processing operation, the power consumption can be reduced.

  Switching between the first processing operation and the second processing operation in the signal processing unit 3 is performed by controlling the input switching means 34 and the power supply interrupting means 36 by a control signal output from the computing unit 33. For example, after the first processing operation is performed nine times continuously, the second processing operation is repeated once. In this case, the failure detection is performed at a timing of once every 10 times, and the failure detection time is longer than when the second processing operation is performed every time. However, the first processing operation or the second processing operation is performed. If the time interval for performing the operation is several ms to several hundred ms, the failure can be detected within a few seconds, so there is no practical problem.

  Here, when it is desired to adjust the detection time of the failure state, it is necessary to change the ratio of the second processing operation, or adjust the time interval for performing the first processing operation or the second processing operation. Can do.

  The sensor system and the sensor signal processing method of this embodiment can be suitably used for, for example, a door open / close switch, a seat belt buckle switch, and the like, and can also be applied to a door open / close detection switch.

It is explanatory drawing which shows roughly an example of the sensor system which is embodiment of this invention. It is explanatory drawing which shows the example which provided the buffer amplifier in the output side of a sensor. It is explanatory drawing which shows an example which used the 2 pole switch for the sensor. It is explanatory drawing which shows an example which used the 3 pole switch for the sensor. It is explanatory drawing which shows an example which used the variable resistor for the sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor system 2 Sensor unit 3 Signal processing unit 21 Sensor 22 Power supply 23 Buffer amplifier 24 2 pole switch 25 3 pole switch 26 Variable resistor 31 A / D converter 32 Comparator 33 Calculator 34 Input switching means 35 Power supply 36 Power supply interruption means

Claims (7)

In a sensor system comprising a sensor unit and a signal processing unit for processing an output signal of the sensor unit,
The signal processing unit includes a first processing operation that performs only output signal processing during normal operation of the sensor unit, and a second processing operation that performs output signal processing during normal operation and failure of the sensor unit. It has a processing state switching function to switch ,
In the first processing operation, the voltage value of the output signal of the sensor unit is converted into a binary voltage value by a predetermined threshold value, and in the second processing operation, the output voltage of the sensor unit is converted into the voltage value. A sensor system characterized in that it is an operation of converting into a digital signal according to a value .   The sensor according to claim 1, wherein the processing state switching function is a function of switching a processing state so that a time interval of the first processing operation is shorter than a time interval of the second processing operation. system.   3. The sensor system according to claim 1, wherein the output signal of the sensor unit is an analog voltage signal. The signal processing unit is characterized that the apparatus is supplied with power directly from the battery is connected to the battery, claims 1 to 3 sensor system according. In a sensor signal processing method for processing an output signal of a sensor unit,
Switching between a first processing operation that performs only output signal processing during normal operation of the sensor unit and a second processing operation that performs output signal processing during normal operation and failure of the sensor unit ;
In the first processing operation, the voltage value of the output signal of the sensor unit is converted into a binary voltage value by a predetermined threshold value, and in the second processing operation, the output voltage of the sensor unit is converted into the voltage value. A sensor signal processing method, characterized in that the operation is a conversion into a digital signal corresponding to the value . 6. The sensor signal processing method according to claim 5 , wherein the processing operation is switched so that the time interval of the first processing operation is shorter than the time interval of the second processing operation. The first processing operation is based on a result of converting a voltage value of an output signal of the sensor unit into a binary voltage value by a predetermined threshold value and measuring the converted voltage by the signal processing unit. an operation of processing, the second processing operation, characterized in that the voltage value of the output signal of the sensor unit is an operation of processing based on the result measured by the signal processing unit, according to claim 5 or The sensor signal processing method according to claim 6 .

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