JP2005037300A - Portable equipment having acceleration history recording function, and acceleration sensor device used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide portable equipment for proving the fact of fall after the event while the portable equipment has a function for detecting the fall of the equipment and recording the history of acceleration until fall collision. <P>SOLUTION: The portable equipment comprises a three-axis acceleration sensor; a fall determining means for judging whether the level of acceleration detected by the acceleration sensor is smaller than a specified value that is smaller than gravity acceleration (1G) or not for all three axes; and a non-volatile semiconductor memory. When the fall determining means determines falling, data related to acceleration detected by the acceleration sensor are recorded in the non-volatile semiconductor memory quickly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a portable device having a function of detecting when a portable device 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 requires a protective measure in case of falling. A conventional example of such a protective measure is described in Patent Document 1. According to this, a three-axis acceleration sensor is provided, and when the acceleration signal becomes substantially zero for all three axes, it is determined that the head is free-falling, and the magnetic head is moved to the retreat area, so Was preventing data destruction on the magnetic disk.

JP 2000-241442 A

However, the above-mentioned protection measures are not universal, and data destruction cannot be prevented depending on the degree of impact, and it is also predicted that the magnetic disk device itself or other parts may be damaged. For any product, it is normal for the manufacturer to provide a free warranty provision that the manufacturer repairs it free of charge within a certain period of time after purchase, but as a disclaimer in that case `` failure due to excessive use '' There are many things that are clearly stated. It is reasonable to consider that damage due to dropping as described above falls under `` failure due to excessive use '', but if there is no noticeable damage to the outer shape of the equipment casing, etc., whether the failure is due to dropping or not It is difficult to judge.

Accordingly, an object of the present invention is to provide a portable device that has a function of detecting the fall of the device and recording the history of acceleration until the fall collision, and can prove the fact of the fall after the fact. .

The portable device with an acceleration history recording function according to the present invention is a three-axis acceleration sensor and a small device for determining whether or not the magnitude of acceleration detected by the acceleration sensor is smaller than a predetermined value smaller than gravitational acceleration (1G). The drop determination unit includes an acceleration determination unit, a drop determination unit that determines that the acceleration is small for all three axes, and a non-volatile semiconductor memory. Data relating to the acceleration detected by the acceleration sensor when it is determined that the means is falling is recorded in the nonvolatile semiconductor memory for a short time.

It is a well-known physical principle that the acceleration of an object in free fall is zero for all three orthogonal axes. Accordingly, when the acceleration values detected by the three-axis acceleration sensor indicate substantially zero values for all axes, it can be determined that the portable device equipped with the acceleration sensor is in a falling state. The nonvolatile semiconductor memory starts recording the acceleration value detected by the acceleration sensor using the fall determination as a trigger, and continues recording for a short time around 1 second. 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 the recorded contents of the non-volatile semiconductor memory are analyzed after the fact and the acceleration history as described above is confirmed, it can be determined that the portable device has the fact of a drop collision.

In addition, since the semiconductor memory has high impact resistance, the probability of damage at the time of a drop collision is low. further,
Since it is a non-volatile memory, the contents recorded so far can be retained even if the power is turned off due to the impact of a drop collision. The falling time of the object is determined by the height of falling (h) and the acceleration of gravity (9.8 m / sec · sec). For example, the falling time when dropping from a height of 1 m is
It is approximately 0.45 seconds. Therefore, if the recording time in the memory is about 1 second, it is sufficient for normal use.

According to the present invention, when the fall of the portable device is detected, the history of acceleration up to the falling collision can be recorded in the nonvolatile semiconductor memory, and the recorded contents of the nonvolatile semiconductor memory are analyzed afterwards, If this portable device has a fall collision, you can prove it.

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

FIG. 1 shows a first embodiment of the present invention. This figure shows the part which concerns on this invention especially among the portable apparatuses which employ | adopted this invention. The triaxial acceleration sensor 1 detects X, Y, and Z axis accelerations orthogonal to each other, and is, for example, a piezoresistive bridge type. Since the signal detected from the bridge is weak, it is usually amplified and output. The fall determination circuit 2 sets the magnitude (absolute value) of the acceleration signal of each axis obtained from the triaxial acceleration sensor 1 to 1/3 of the gravitational acceleration (1G).
Compared with a threshold value corresponding to the degree, a drop flag indicating that the three axes are falling when the value is smaller than the threshold value is generated at the output. The drop determination may be performed simultaneously for the three axes, or the comparison may be made for each axis sequentially, and a determination of falling may be made when a comparison result equal to or less than the threshold is obtained for each axis. When the drop flag is input to the microcomputer 3, the microcomputer 3 controls to write the acceleration signal of each axis obtained from the triaxial acceleration sensor 1 in the flash memory 4. 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.

FIG. 2 shows an example of a type of drop determination circuit that sequentially compares each axis with a threshold value. In FIG. 2, acceleration signals X, Y, and Z are sequentially selected by a switch 21 and compared with the threshold values by 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. T which synchronized the logical product of the outputs of the two comparators with the switch
Latched by the D latch circuits 23X, 23Y, and 23Z at the timing of x, Ty, and Tz, respectively,
The logical product of the latch results is output as a fall flag. This circuit example is advantageous in that the number of comparators is small and power consumption is small.

A second embodiment of the present invention is shown in FIG. This embodiment differs from the first embodiment in that the output circuit 5 is inserted in the path connecting the acceleration signals X, Y, and Z to the flash memory, and the operation is turned on when a fall flag is generated. This is what I did. Even if the portable device is stopped, damage due to dropping can occur. Therefore, it is desirable that the acceleration sensor and the drop detection circuit are always in an operating state in which the occurrence of dropping can be monitored, and power consumption for that purpose must be reduced as much as possible. . This embodiment can reduce the power consumption of the output circuit. It should be noted that the microcomputer and the flash memory are also preferably designed to wake up from the standby state by the fall flag.

A third embodiment of the present invention is shown in FIG. This embodiment is different from the second embodiment in that an A / D converter 6 is provided in place of the output circuit 5, and the operation of the A / D converter 6 is similarly performed when a drop flag is generated. Is to turn on. Since the A / D converter is a circuit that consumes a relatively large amount of power, this embodiment can reduce the power consumption in the fall monitoring state when the portable device is stopped.

When detecting the fall of a portable device, the history of acceleration up to the falling collision can be recorded in the nonvolatile semiconductor memory, and the contents recorded in the nonvolatile semiconductor memory are analyzed afterwards, Since the fact of a drop collision can be proved, it can be applied not only to a notebook personal computer but also to a drop collision certification for all portable devices such as PDAs, mobile phones, digital still cameras, digital video cameras and the like.

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 circuit. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 3rd Example of this invention.

Explanation of symbols

13-axis acceleration sensor, 2 drop determination circuit, 3 microcomputer, 4 flash memory,
5 output circuit, 6 A / D converter, 21 switch, 22a, 22b comparator,
23X, 23Y, 23Z D latch circuit.

Claims (4)

The triaxial acceleration sensor and the magnitude of acceleration detected by the acceleration sensor is gravitational acceleration (1G)
A drop determination means for determining whether or not all three axes are smaller than a smaller predetermined value and a non-volatile semiconductor memory are mounted, and the acceleration sensor when the drop determination means determines that the drop is in progress A mobile device with an acceleration history recording function, wherein the data relating to the acceleration detected in step 1 is recorded in the nonvolatile semiconductor memory for a short time. The triaxial acceleration sensor and the magnitude of acceleration detected by the acceleration sensor is gravitational acceleration (1G)
An acceleration sensor device comprising drop determination means for determining whether or not all three axes are smaller than a smaller predetermined value, and outputting an acceleration signal and a drop determination result. The triaxial acceleration sensor and the magnitude of acceleration detected by the acceleration sensor is gravitational acceleration (1G)
A drop determining means for determining whether or not the value is smaller than a predetermined value smaller than all three axes; and a circuit for outputting an acceleration signal, the circuit for outputting the acceleration signal being the drop determining means. The acceleration sensor device is characterized in that the operation / non-operation is controlled according to the determination result and an acceleration signal and a fall determination result are output. The triaxial acceleration sensor and the magnitude of acceleration detected by the acceleration sensor is gravitational acceleration (1G)
A drop judging means for judging whether or not the value is smaller than a predetermined value smaller than a predetermined value and a circuit for converting the acceleration signal into a digital value and outputting the digital value, and converting the acceleration signal into a digital value The circuit for outputting is controlled in operation / non-operation according to the determination result of the drop determination means, and outputs a digitized acceleration signal and a drop determination result.

Images