JP2005241503A - Acceleration history recording device at time of falling and acceleration sensor device used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration history recording device at the time of falling for certificating a fact of the falling thereafter by detecting the falling of a device itself and providing a function for recording the history of an acceleration until it falls and collides. <P>SOLUTION: The acceleration history recording device comprises a three-axes acceleration sensor for outputting high sensitivity detection output and low sensitivity detection output, a falling determining means for determining the falling on the basis of the high sensitivity detection output of the acceleration sensor, and a non-volatile semiconductor memory. When the falling determining means determines that it is during falling, data concerning the low sensitivity detection output of the acceleration sensor are recorded to the non-volatile semiconductor memory for a short time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an apparatus for detecting when it falls and recording a history of acceleration.

Due to the nature of portable devices, there is a high risk of being dropped accidentally. And what has a built-in magnetic disk like a notebook type personal computer is particularly sensitive to impact, and when dropped, it often leads to damage that requires repair. Most products usually have a free repair warranty that the manufacturer will repair free of charge within a certain period of time after purchase. " It is reasonable to consider that damage due to falling as described above falls under the category of “failure caused by excessive use”, but if there is no noticeable damage to the external shape of the equipment casing, etc., whether the failure is due to dropping or not. It is difficult to judge. Further, in general, there is a high risk of receiving a drop impact or an impact close thereto during the transportation of the cargo, and the cargo may be damaged. Again,
If there is no noticeable damage to the outer shape of the package, it is difficult to determine whether the cargo damage is due to falling, and it is difficult to ask the responsibility of the carrier.

Therefore, the same applicants and inventors as in the present application devised a method for enabling the fact of the fall to be proved afterwards, and filed the invention described in Patent Document 1 first. According to this, a three-axis acceleration sensor,
Small acceleration determining means for determining whether or not the magnitude of acceleration detected by the acceleration sensor is smaller than a predetermined value smaller than gravitational acceleration (1 g), and the small acceleration determining means has a small acceleration for all three axes. In a portable device provided with a fall determination unit that determines that it is in a free fall when it is determined that it is, and a non-volatile semiconductor memory, when the fall determination unit determines that it is falling, the acceleration sensor Data regarding the detected acceleration is recorded in the nonvolatile semiconductor memory for a short time. In the acceleration history recorded in the semiconductor memory, a small value close to zero is first recorded for a while, and a large value is recorded at the moment of collision. If it is analyzed and the acceleration history as described above is confirmed, it can be determined that this portable device has a fact of a drop collision.

Japanese Patent Application No. 2003-276204

The triaxial acceleration sensor used in the above technique is a gravitational acceleration (1
g) It is desirable to have both high sensitivity performance for accurately detecting a smaller low acceleration region and high dynamic range performance capable of dealing with the high acceleration region for recording the acceleration history at the time of a drop collision. However, it is difficult to meet this requirement, and in practice it is usually necessary to compromise high dynamic range performance. For example, when the dynamic range is several times to 10 times the gravitational acceleration, since the impact value limited by the dynamic range is recorded in the acceleration history, it is possible to determine the degree of impact when falling. There is no problem.

Therefore, an object of the present invention is to record an acceleration history at the time of the fall of the device itself, in a device that records the history of acceleration up to the falling collision, which can be detected with high sensitivity and accuracy when detecting the fall of the device. An object of the present invention is to provide a fall acceleration history recording apparatus that can record in correspondence with a wide range of impact values at the time of a drop collision and can prove the fact of the drop collision and the magnitude of the impact after the fact.

The fall acceleration history recording apparatus of the present invention outputs a high sensitivity detection output and a low sensitivity detection output 3
An acceleration sensor, a fall determination means for judging fall based on a high-sensitivity detection output of the acceleration sensor, and a non-volatile semiconductor memory, and when the fall judgment means judges that the fall is in progress, Data on the low sensitivity detection output is recorded in the nonvolatile semiconductor memory for a short time. Since the high-sensitivity detection output of the acceleration sensor is accurate even for accelerations smaller than gravitational acceleration (1 g), the drop determination means is accurate based on when the acceleration detection value becomes small due to the fall of the device. It can be judged as falling well. Further, since the low-sensitivity detection output of the acceleration sensor does not easily saturate even with a large acceleration, a large acceleration data at the time of a drop collision can be recorded in the nonvolatile semiconductor memory.

If the recorded contents of the non-volatile semiconductor memory are analyzed after the fact and there is an acceleration history in which a large acceleration indicating a collision is recognized after a small acceleration value indicating that it is falling for a short time, this device has a falling collision. It is possible to determine that the above-mentioned fact has occurred, and it is possible to estimate the magnitude of the impact at the time of collision. In addition, if the recorded acceleration history is accompanied by date and time data,
The date and time of the drop collision can be clearly identified.

By incorporating the fall acceleration history recording apparatus of the present invention in a portable device, the fact of the fall can be proved after the portable device is dropped. Further, by attaching the fall acceleration history recording device of the present invention to the cargo to be transported or its packing container, the fact of the fall during the cargo transportation can be proved after the fact.

  A more detailed embodiment according to the present invention will be described below.

FIG. 1 shows a first embodiment of the present invention. In this figure, a triaxial acceleration sensor 1 detects accelerations in the X, Y, and Z axes orthogonal to each other, and includes, for example, a piezoresistive bridge type detector and an amplifier circuit. In particular, the present embodiment includes a high sensitivity detection unit 11 that detects acceleration in the low acceleration region and a low sensitivity detection unit 13 that detects acceleration in the high acceleration region, and amplifies the detection voltage of each detection unit. Output. In this figure, the signal detected by the high sensitivity detector is X
H, YH, and ZH are displayed, and signals detected by the low sensitivity detector are displayed as XL, YL, and ZL. The fall determination unit 2 is configured, for example, as shown in the circuit example of FIG. (Value) is compared with a threshold value corresponding to about 1/3 of the gravitational acceleration (1 g), and when all three axes are smaller than the threshold value, a drop flag indicating that the vehicle is falling is generated at the output. When the drop flag is input to the microcomputer 3, the microcomputer 3 controls to write the acceleration signals (XL, YL, ZL) of each axis obtained from the low sensitivity detection unit of the three-axis acceleration sensor 1 to the flash memory 4. To do. When the acceleration signal of each axis obtained from the triaxial acceleration sensor 1 is an analog value, a digital value obtained by an A / D converter (not shown) is written in the flash memory.
The length of the writing time may be determined in consideration of the assumed maximum height of the drop, but if the maximum height of the drop is assumed to be about 1 meter, a short time of about 1 second is sufficient. .

Since the high-sensitivity detection unit 11 accurately detects an acceleration smaller than the gravitational acceleration (1 g),
When the acceleration detection value becomes small due to the fall of the device, the fall determination unit can accurately determine that the fall has occurred. Further, since the low sensitivity detector 13 outputs a signal without saturating even with a large acceleration, a large acceleration data at the time of a drop collision can be recorded in the nonvolatile semiconductor memory.

The circuit example of the drop determination unit shown in FIG. 2 operates as follows. In FIG. 2, the acceleration signal X
H, YH, and ZH are sequentially selected by the switch 21 and compared with the threshold value by the comparators 22a and 22b. Here, the reference potential of the acceleration signal is Vref = 1.5 V, and the threshold potential is also set based on this. Tx, Ty that synchronizes the logical product of the outputs of the two comparators with the switch
, Tz, and latched by the D latch circuits 23X, 23Y, 23Z, respectively, and the logical product of the three latch results is output as a fall flag. This circuit example has the advantage that the number of comparators is small and the power consumption is small because it is a type that compares with the threshold sequentially for each axis. Is possible. Further, as illustrated in FIG. 3, it is also possible to use a digital processor 25 that performs a fall determination calculation after A / D converting acceleration signals XH, YH, and ZH. In this case, the calculation algorithm for the fall determination may be a fall determination by comparing the magnitude of the vector sum of the three-axis acceleration values with a predetermined threshold in addition to the algorithm corresponding to FIG.

A second embodiment of the present invention is shown in FIG. In this embodiment, one amplifier circuit is used, and the input is switched between the detection signal of the high sensitivity detection unit and the detection signal of the low sensitivity detection unit. Initially, it connects so that the detection signal of a high sensitivity detection part may be amplified. Drop detection unit 2
Is determined to fall and a drop flag is generated, the connection is switched so as to amplify the detection signal of the low sensitivity detection unit, and the signals (XL, YL,
ZL) is output. At the same time, a drop flag is input to the microcomputer 3, and the microcomputer 3 controls to write the acceleration signals (XL, YL, ZL) of each axis obtained from the low sensitivity detection unit of the triaxial acceleration sensor 1 into the flash memory 4. . Thereby, the fall determination is performed based on the high-sensitivity detection acceleration value of the acceleration sensor 1, and recording in the flash memory 4 is performed by the low-sensitivity detection acceleration signal of the acceleration sensor 1.

A third embodiment of the present invention is shown in FIG. The present embodiment is characterized in that it includes a drive voltage switching means 15 for the acceleration detection bridge. A piezoresistive acceleration sensor has the principle property that the detection sensitivity changes in proportion to the DC voltage that drives the detection bridge. Using this, control is performed as follows. Initially, the drive voltage is used in a high state and the detection bridge is placed in a high sensitivity state. When the fall determination unit 2 determines that the fall has occurred and generates a fall flag, the drive voltage is switched low, and the acceleration sensor 1 moves to a low sensitivity state. At the same time, a drop flag is input to the microcomputer 3, and the microcomputer 3 detects the low sensitivity detection acceleration signal (in the low sensitivity state of the triaxial acceleration sensor 1 (
(XL, YL, ZL) is controlled to be written into the flash memory 4. As an example of setting the drive voltage, if the sensitivity is 3 V in the high sensitivity state and 0.3 V in the low sensitivity state, the acceleration history can be recorded with a dynamic range of 10 times based on the high sensitivity state.

In the illustrated circuit example, the drive voltage is switched only on the high side of the bridge, but the low side (ground side) may be switched as necessary. In order to reduce the drive voltage, it is sufficient to insert a resistor in series with the drive voltage application wiring, without applying a low voltage directly. In this case, a substantially high drive voltage is applied when the inserted resistor is short-circuited, and a substantially low drive voltage is applied when the short-circuit is opened.

A fourth embodiment of the present invention is shown in FIG. The present embodiment is characterized in that the amplifier circuit 12 has a gain switching function. The acceleration detection characteristic of the piezoresistive bridge type acceleration sensor itself does not show saturation characteristics suddenly when the magnitude of applied acceleration is increased.
In general, it exhibits moderate saturation characteristics. This is in contrast to amplifier circuits that generally exhibit abrupt saturation characteristics. By utilizing this property, the dynamic range in the high acceleration region can be expanded by reducing the gain of the amplifier circuit while keeping the sensitivity of the detection unit constant.

In this embodiment, control is performed as follows. First, the gain of the amplifier circuit is used in a high state, and the sensitivity of the acceleration sensor 1 is put in a high sensitivity state. When the fall determination unit 2 determines that the fall has occurred and generates a fall flag, the gain of the amplifier circuit is switched to a low level, and the sensitivity of the acceleration sensor 1 as a whole shifts to a low sensitivity state. At the same time, a drop flag is input to the microcomputer 3, and the microcomputer 3
Control is performed so that the acceleration signals (XL, YL, ZL) of each axis obtained in the low sensitivity state of the axis acceleration sensor 1 are written in the flash memory 4. If the ratio of high sensitivity to low sensitivity of the amplification gain is 10: 1 as an example, acceleration history can be recorded with a dynamic range of 10 times based on the high sensitivity state.

A fifth embodiment of the present invention is shown in FIG. This embodiment is different from the first embodiment in that acceleration data written to the flash memory 4 is converted into low-sensitivity detection output (X
L, YL, ZL) and high sensitivity detection output (XH, YH, ZH). As a result, when the recorded contents of the flash memory are analyzed after the fact, it is possible to analyze the small acceleration value indicating that it is falling more precisely, and it is also possible to analyze the large acceleration indicating the collision, so that the falling collision can be performed more accurately. Can be determined. In addition, by analyzing the acceleration values of the three axes at the time of collision as a vector, the direction of the applied impact can also be estimated, and by examining the relationship with the damaged part of the equipment or cargo, dropping and damage It becomes possible to further clarify the causal relationship. However, when the direction of impact is not questioned, the acceleration-related data recorded in the flash memory does not necessarily need to be the individual acceleration values of the three axes, for example, the magnitude of the vector sum of the three-axis acceleration values. It may be data. This is applicable to any of the above embodiments.

As described above, according to the present invention, when a fall of the fall acceleration history recording device itself is detected, the history of acceleration up to the fall collision corresponds to a wide range of impact values at the fall collision. By analyzing the recorded contents of the non-volatile semiconductor memory after the fact, if there is a fact of a fall collision in the equipment incorporating the fall acceleration history recording device or the attached cargo, You can prove the fact and the magnitude of the impact.

It is a figure which shows the 1st Example of this invention. It is a figure which shows the circuit example of a fall determination part. It is a figure which shows the other example of a fall determination part. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 3rd Example of this invention. It is a figure which shows the 4th Example of this invention. It is a figure which shows the 5th Example of this invention.

Explanation of symbols

1 3-axis acceleration sensor, 2 drop detector, 3 microcomputer, 4 flash memory,
11 high sensitivity detector, 12, 14 amplifier circuit, 13 low sensitivity detector,
15 driving voltage switching means, 21 switch, 22a, 22b comparator,
23X, 23Y, 23Z D latch circuit, 24 A / D converter,
25 Digital processor.

Claims (7)

A three-axis acceleration sensor that outputs a high-sensitivity detection output and a low-sensitivity detection output; a drop determination unit that determines a drop based on the high-sensitivity detection output of the acceleration sensor; and a nonvolatile semiconductor memory, the drop determination unit A fall acceleration history recording apparatus that records data relating to the low sensitivity detection output of the acceleration sensor in the nonvolatile semiconductor memory for a short time when it is determined that the sensor is falling. A 3-axis acceleration sensor that outputs a high-sensitivity detection output and a low-sensitivity detection output, and a drop determination unit that determines a drop based on the high-sensitivity detection output of the acceleration sensor, the drop determination result and the low-sensitivity detection of the acceleration sensor An acceleration sensor device that outputs an output. The three-axis acceleration sensor that outputs the high-sensitivity detection output and the low-sensitivity detection output includes a high-sensitivity detection unit, a low-sensitivity detection unit, and two amplification circuits, and each detection signal of the high-sensitivity detection unit and the low-sensitivity detection unit The acceleration sensor device according to claim 2, wherein the signal is amplified by each amplifier circuit and output. The three-axis acceleration sensor that outputs the high-sensitivity detection output and the low-sensitivity detection output includes a high-sensitivity detection unit, a low-sensitivity detection unit, and one amplifier circuit, and each detection signal of the high-sensitivity detection unit and the low-sensitivity detection unit The acceleration sensor device according to claim 2, wherein the acceleration sensor device is switched and amplified by the amplifier circuit for output. The 3-axis acceleration sensor that outputs the high-sensitivity detection output and the low-sensitivity detection output has a function of switching the driving voltage of the acceleration detection bridge, and the high-sensitivity detection output and the low-sensitivity detection output are switched by switching the driving voltage. The acceleration sensor device according to claim 2, wherein: The three-axis acceleration sensor that outputs the high-sensitivity detection output and the low-sensitivity detection output has a function of switching the amplification gain of the amplification circuit, and switches between the high-sensitivity detection output and the low-sensitivity detection output by switching the amplification gain. The acceleration sensor device according to claim 2, wherein A three-axis acceleration sensor that outputs a high-sensitivity detection output and a low-sensitivity detection output; a drop determination unit that determines a drop based on the high-sensitivity detection output of the acceleration sensor; and a nonvolatile semiconductor memory, the drop determination unit A fall acceleration history recording apparatus that records data relating to a low sensitivity detection output and a high sensitivity detection output of the acceleration sensor in the nonvolatile semiconductor memory for a short time when it is determined that the sensor is falling.

Images