JP4259508B2 - Tilt fluctuation detection device and anti-theft device - Google Patents

Description

  The present invention relates to an inclination variation detection device and an anti-theft device, and more particularly to an apparatus for detecting a variation in an inclination angle of a detection object and an apparatus for preventing the detection object from being stolen using the device. .

When the inclination angle of the vehicle is detected by the inclination angle sensor mounted on the vehicle, the change in inclination during parking is calculated by the processor that processes the output of the sensor, and the inclination change exceeds a predetermined threshold value In the vehicle antitheft device that issues an alarm, a plurality of determination systems for comparing the inclination change with a predetermined threshold value are set, and each determination system updates an initial value for calculating the inclination change every predetermined time, A technique is disclosed in which the initial value update times are different from each other (see Patent Document 1).
Japanese Patent No. 2889993 (pages 1 to 5 and FIGS. 1 to 3)

  Conventionally, a tilt angle sensor for detecting the tilt angle of a detection target is mounted on the detection target, and the tilt angle sensor detects fluctuations (displacements) in the tilt angle of the detection target over a long period of time. An inclination fluctuation detecting device is known.

If this tilt variation detection device is mounted on a vehicle such as an automobile, it can detect that the vehicle has been jacked up to steal the vehicle body, wheels, etc., based on the variation in the tilt angle of the vehicle. become.
In addition, if this tilt variation detection device is installed in various fixed devices (for example, OA devices, vending machines, etc.), it can be transported to steal devices based on variations in tilt angles of the devices. It is possible to detect that it has been performed.

  Then, according to the detection result of the inclination angle of the vehicle or various devices as the detection target, if it is determined that the detection target is stolen, an alarm sound is emitted from the alarm device, or the detection target By notifying the administrator, it is possible to prevent theft. That is, the antitheft device for preventing the detection object from being stolen can be realized by combining the tilt variation detecting device and the alarm / notification device.

  In such an anti-theft device, repeated misjudgment is considered to be misjudgment even if a theft actually occurs and reliability is lowered. Therefore, it is required to avoid misjudgment as much as possible. Therefore, it is required to improve the detection accuracy of the inclination fluctuation detection device used for the anti-theft device.

  Moreover, in such an anti-theft device, it is necessary to monitor the theft of a detection target object for a long time, so that it is required to reduce power consumption. Therefore, it is required to reduce the power consumption of the inclination variation detection device used for the anti-theft device.

  In particular, when applied to a vehicle as an object to be detected, it is necessary to monitor the theft when the engine is stopped and the in-vehicle battery is not charged when the vehicle is parked or stopped. Since power is supplied, if the power consumption of the anti-theft device is large, the battery size must be increased to prevent the battery from running out. However, increasing the battery size is unacceptable because it hinders vehicle size reduction, weight reduction, and price reduction.

The present invention has been made to satisfy the above requirements and has the following objects.
(1) To provide a tilt variation detection device with high detection accuracy and low power consumption.
(2) An anti-theft device with high determination accuracy and low power consumption is provided by using the inclination variation detection device of (1).

The invention described in claim 1
An inclination angle detecting means (21) for detecting the inclination angle of the detection object;
A determination means (24) for determining a change in the inclination angle of the detection object based on the inclination angle detected by the inclination angle detection means;
An inclination fluctuation detection device (20) comprising switching means (24, 25) for switching each of the inclination angle detection means and the determination means to either an operating state or a non-operating state,
The determination means determines a possibility that the inclination angle of the detection target is actually changed based on a past fluctuation state of the inclination angle;
Said switching means when the switch between the tilt angle detecting means and said determining means only intermittently a predetermined time period (Ton) every predetermined period (t) in the operating state, is highly the possibility that the determination means determines As described above, the predetermined cycle for switching the tilt angle detection unit and the determination unit to the operation state is changed to be small, and the change of the predetermined cycle is divided into three or more stages,
The tilt angle detecting means and the determination means when the non-operating state and technical features and that power consumption is smaller than that when the operating state.

The invention described in claim 2
A tilt variation detection device (20) according to claim 1 ;
An anti-theft device (10) provided with an informing means (30) for performing at least one of generating an alarm and notifying an administrator of an object to be detected based on a determination result of the determining means of the inclination variation detecting device. ) As a technical feature.

<Claim 1: Corresponds to [2] and [3] of the second embodiment and another embodiment >
In the invention of claim 1, the switching means (24, 25) is used only when the inclination angle detection means (21) and the determination means (24) are used to obtain information on the inclination angle of the detection object (period Ton). The tilt angle detecting means and the determining means are switched to the operating state. The switching means switches the inclination angle detection means and the determination means to the non-operating state when the inclination angle detection means and the determination means are not used (period Toff).
Here, the tilt angle detection means and the determination means consume less power when in the non-operating state than when in the operating state.

Therefore, according to the first aspect of the present invention, the power consumption can be reduced by intermittently operating the tilt angle detecting means and the determining means at predetermined intervals for a predetermined period as compared with the case where each means is operated continuously.
Note that, for the predetermined period (t) and the predetermined period (Ton), a cut-and-try operation is performed so that a sufficient power consumption reduction effect can be obtained and at the same time the detection ability of the change in the tilt angle of the detection target is not deteriorated. Find and set the optimal value experimentally.
In this way, even when the tilt angle detection means and the determination means are operated intermittently, the detection capability that is practically inferior to that when the tilt angle detection means and the determination means are operated continuously can be obtained.

In the first aspect of the invention, the determination means (24) determines the possibility that the inclination angle has actually changed based on the past fluctuation state of the inclination angle, and the higher the possibility, the switching means ( 24, 25) changes the predetermined period (t) to be small.
Therefore, when it is very unlikely that the inclination angle of the detection object actually fluctuates, and the detection object may be considered to be stationary, the predetermined period (t) is set to a large value. As a result, although the detection capability is lowered, the power consumption can be greatly reduced.

In addition, when there is a possibility that the tilt angle of the detection target object has actually fluctuated, and the detection target object may be considered to have been subjected to vibration or impact, the predetermined cycle is set to a medium level. By changing the setting to, the detection capability is reduced to some extent, but the power consumption can be reduced.
And when there is a high possibility that the tilt angle of the detection target is actually fluctuating, the power consumption increases by changing the setting of the predetermined period (t) to be small, but the detection capability is very high. Can be increased.
In addition, since the change of the predetermined cycle is divided into a plurality of stages of three or more stages, optimization is performed by setting the predetermined period more finely according to the past fluctuation state of the tilt angle of the detection target. Therefore, it is possible to further increase the detection capability of the change in the tilt angle and further reduce the power consumption.

< Claim 2 >
In invention of Claim 2, the anti-theft device (10) which prevents the theft of a detection target object is implement | achieved by combining the inclination fluctuation | variation detection apparatus (20) of Claim 1 , and alerting | reporting means (30). Can do.
And since the inclination fluctuation | variation detection apparatus of Claim 1 has high detection accuracy and low power consumption, it can raise the determination precision of an antitheft device and can also reduce power consumption.
A specific method for generating an alarm by the notification means is, for example, generating an alarm sound from an alarm buzzer.

<Explanation of terms>
The reference numerals in parentheses described in [Means for Solving the Problems] and [Effects of the Invention] are the components and structures described in [Best Mode for Carrying Out the Invention] to be described later. This corresponds to the element code.
The correspondence between the constituent members and constituent elements described in [Means for Solving the Problems] and [Effects of the Invention] and the constituent members and constituent elements described in [Best Mode for Carrying Out the Invention] is as follows: It is as follows.

The “tilt angle detecting means” corresponds to the tilt angle sensor 21.
The “determination means” corresponds to an inclination angle variation detection process (S201 to S214, particularly an inclination angle variation determination / sample cycle setting process (S214: S301 to S305)) executed by the microcomputer 24.
The “switching unit” corresponds to the microcomputer 24 and the sensor power supply device 25.
The “notification unit” corresponds to the alarm / notification device 30.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In each embodiment, the same constituent members and constituent elements are denoted by the same reference numerals, and redundant description of the same content is omitted.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration of the antitheft device 10 according to the first embodiment.
The anti-theft device 10 includes an inclination variation detection device 20 and an alarm / notification device 30.
The inclination variation detection device 20 includes an inclination angle sensor 21, an analog filter 22, an A / D converter 23, a microcomputer 24, and a sensor power supply device 25.

The tilt angle sensor 21 is mounted on a detection target (not shown) and detects the tilt angle of the detection target. The detection object includes an automobile and various devices fixedly installed (for example, an OA device and a vending machine), but may be any article.
There are various detection methods of the tilt angle sensor 21 such as [1] a method using an acceleration sensor and [2] a method of estimating a tilt angle using a height sensor that detects height positions of two or more detection points. However, any type of detection sensor may be used.

FIG. 2 is an explanatory diagram for explaining a method of using an acceleration sensor as the tilt angle sensor 21.
From the output SA of the acceleration sensor, which is the tilt angle sensor 21, the detection axis direction, and the gravitational acceleration G, the tilt angle θ of the detection target can be obtained based on Equation 1.
The tilt angle sensor 21 includes an amplifier for amplifying a minute output SA.
SA = G × sin θ (Equation 1)

The analog filter 22 that is a low-pass filter removes a noise component contained in the output signal of the tilt angle sensor 21 and outputs the result. Note that the analog filter 22 may be built in the tilt angle sensor 21.
The A / D converter 23 A / D (Analog to Digital) converts the output signal of the analog filter 22 into a digital signal that can be processed by a computer, and outputs the digital signal. The A / D converter 23 may be built in the microcomputer 24.

The microcomputer (hereinafter abbreviated as “microcomputer”) includes a central processing unit (CPU) 24a, a read-only storage device (ROM) 24b, a readable / writable storage device (RAM) 24c, and an input / output device (I / I). O) 24d, timer 24e and the like are incorporated.
The I / O 24 d is connected to the A / D converter 23, the sensor power supply device 25, and the alarm / notification device 30. The output signal of the A / D converter 23 is input from the I / O 24d to the microcomputer 24, and the control signals Ca and Cb generated by the microcomputer 24 are transmitted from the I / O 24d to the sensor power supply device 25 and the alarm / notification device 30. Is output.

The microcomputer 24 executes an inclination angle variation detection process for detecting the variation (displacement) of the inclination angle of the detection target based on the output signal of the A / D converter 23, and sets the alarm / notification device 30 based on the detection result. A control signal Ca for control is generated and output.
The alarm / notification device 30 performs at least one of generating an alarm and notifying the manager of the detection target according to the control signal Ca.

The microcomputer 24 generates and outputs a control signal Cb for controlling the operation of the sensor power supply device 25.
The sensor power supply device 25 generates a power source of voltage / current necessary for driving the tilt angle sensor 21 from the DC power source Vcc, and controls the supply / cutoff of the power source to the tilt angle sensor 21 (power on / off). Switch according to Cb.

FIG. 3 is a characteristic diagram showing a timing chart of the control signal Cb and a consumption current fluctuation characteristic of the inclination fluctuation detection device 20 in the first embodiment.
The microcomputer 24 outputs a control signal Cb that becomes a high (H) level for a certain period Ton every certain period t.
The sensor power supply device 25 supplies power to the tilt angle sensor 21 for a certain period Ton at a certain period t according to the control signal Cb. That is, the sensor power supply device 25 supplies power to the tilt angle sensor 21 when the control signal Cb is at a high level, and cuts off power supply to the tilt angle sensor 21 when the control signal Cb is at a low (L) level. To do.

Here, the microcomputer 24 has a sleep / wake-up function, and wakes up for a predetermined period Ton at a predetermined period t according to the time of the timer 24e, and sleeps during the other period Toff (t = Ton + Toff). ).
The period t and the period Ton when power is supplied from the sensor power supply device 25 to the tilt angle sensor 21 and the timing thereof are the same as the period t and the period Ton when the microcomputer 24 wakes up.

At this time, the current consumption of the tilt variation detection device 20 in the period Ton is Ion, and the current consumption of the tilt variation detection device 20 in the period Toff is Ioff.
The current consumption Ion is the total value of the product current required for the wake-up operation of the microcomputer 24 and the current consumption required for the operation of each of the tilt angle sensor 21, the A / D converter 23, and the sensor power supply device 25. is there.
The consumption current Ioff is a consumption current necessary for the sleep operation of the microcomputer 24.

FIG. 4 is a flowchart showing the flow of the tilt angle variation detection process executed by the microcomputer 24 in the first embodiment.
When the microcomputer 24 is activated, the CPU 24a loads the computer program stored (recorded) in the ROM 24b and executes various arithmetic processes according to the computer program, thereby executing the following steps.
In the drawings and the following description, a step is described as “S”.

  By the way, the computer program is recorded not in the ROM 24b built in the microcomputer 24 but in a backup RAM (not shown) built in the microcomputer 24 or an external recording device (external storage device) (not shown) provided with a computer-readable recording medium ( The computer program may be loaded into the CPU 24a from a backup RAM or an external recording device and used as necessary.

  The microcomputer 24 first determines whether or not it is time to sample the output signal of the A / D converter 23 (S101), and when the sample timing is reached (S101: Yes), the output signal of the A / D converter 23 is determined. Is sampled (S102), and the fluctuation of the tilt angle of the detection target is determined based on the output signal (S103), and then the process returns to S101.

Here, in the processing of S101 and S102, the sampling period for sampling the output signal of the A / D converter 23 is the period t when the microcomputer 24 wakes up (power is supplied from the sensor power supply device 25 to the tilt angle sensor 21). It is set to be the same as the period t).
The sample timing for sampling the output signal of the A / D converter 23 is set to be the same as the timing at which the microcomputer 24 wakes up.
Further, sampling the output signal of the A / D converter 23 is nothing other than sampling the output signal of the tilt angle sensor 21.

In the process of S103, there are various methods for determining the variation in the tilt angle of the detection target as follows, but any determination method may be used.
[A] As disclosed in [Prior Art] of Patent Document 1, an initial value of an inclination angle is stored, and an angle difference between the initial value and the current inclination angle is a predetermined threshold value. A method of determining that the tilt angle has changed when the angle exceeds.
[B] As disclosed in [Example] of Patent Document 1, a plurality of determination systems for comparing changes in the tilt angle with a predetermined threshold value are set, and each determination system sets an initial value of the tilt angle. A method of updating the initial value of each determination system at different times while updating it at predetermined time intervals.

[C] A difference (angle difference) between the average value of the tilt angles sampled for the first predetermined number of times from the past to the present time and the average value of the tilt angles sampled for the second predetermined number of times less than the first predetermined number of times is obtained. A method of determining that the tilt angle has changed when there is a predetermined threshold value or more.
The first predetermined number of times, the second predetermined number of times, and the predetermined threshold value may be set by experimentally finding optimum values by cut-and-try. For example, the first predetermined number of times is set to 100 and the second predetermined number of times is set to 10 times. The average value of the inclination angles sampled 100 times from the past to the present and the average value of the inclination angles sampled 10 times from the past to the present What is necessary is just to obtain | require the difference of. Further, the first predetermined number of times is set to 100 times and the second predetermined number of times is set to one time, and the difference between the average value of the inclination angles sampled 100 times from the past to the present and the current inclination angle may be obtained. .

[D] The difference between the samples of the third predetermined number of times from the past to the present (the average value of the inclination angles sampled the first predetermined number of times from the past to the present and the average of the inclination angles sampled the second predetermined number of times less than the first predetermined number of times) A method of determining that the tilt angle has fluctuated when the difference between the values is continuously equal to or greater than the predetermined threshold value.
The third predetermined number of times may be set by experimentally finding an optimum value by cut-and-try. For example, if the third predetermined number of times is set to 10 and it is determined that the tilt angle has fluctuated when the difference is continuously greater than or equal to the predetermined threshold in 10 samples from the past to the present. Good.

[Operations and effects of the first embodiment]
According to the first embodiment, the following actions and effects can be obtained.

  [1-1] In the first embodiment, only when the tilt angle sensor 21 is used to obtain information about the tilt angle of the detection target (period Ton), the microcomputer 24 is woken up and the sensor power supply device 25 is used. Power is supplied to the tilt angle sensor 21. When the tilt angle sensor 21 is not used (period Toff), the microcomputer 24 is set to sleep and the power supply from the sensor power supply device 25 to the tilt angle sensor 21 is interrupted.

That is, the sensor power supply device 25 is brought into an operating state by supplying power to the tilt angle sensor 21 and is brought into a non-operating state by stopping the power supply to the tilt angle sensor 21.
Further, the microcomputer 24 is in an operating state at the time of wakeup, and is in an inactive state at the time of sleep, and power consumption is smaller than at the time of wakeup at the time of sleep.

  In this way, by intermittently operating the inclination variation detection device 20 for each constant period t for a predetermined period Ton, it is possible to reduce power consumption compared to the case where the inclination variation detection device 20 is continuously operated.

That is, the average consumption current Ia when the inclination variation detection device 20 is continuously operated becomes equal to the consumption current Ion in the period Ton (Ia = Ion).
On the other hand, the average current consumption Ia when the tilt variation detection device 20 is operated intermittently can be obtained from Equation 2.
Ia = (Ton × Ion + Toff × Ioff) / t (Equation 2)

  For example, when Ton = 10 msec, Ion = 20 mA, Toff = 990 msec, Ioff = 1 mA, t = 1 sec, the average consumption current Ia = 20 mA when the inclination fluctuation detecting device 20 is continuously operated, and the inclination fluctuation detecting device 20 is intermittent. In the first embodiment, the average current consumption Ia is 1.19 mA. In the first embodiment, the average current consumption is very small, so that the power consumption can be greatly reduced.

[1-2] FIG. 5 is an explanatory diagram for explaining the relationship between the startup characteristic of the inclination variation detection device 20 and the period Ton.
The tilt angle sensor 21 is not instantly usable when power is supplied from the sensor power supply device 25, and requires a certain amount of time for the operation to stabilize.
Further, the analog filter 22 requires a certain amount of time until a normal output signal is obtained based on the rising characteristics determined by the time constant.
Therefore, the activation time Tk required until the tilt variation detection device 20 can operate stably is a time obtained by adding an appropriate margin to the activation times of the tilt angle sensor 21 and the analog filter 22.

As shown in FIG. 5A, when the period Ton is sufficiently large with respect to the activation time Tk, the microcomputer 24 can surely execute the inclination angle variation detection process within the period Ton. The detection ability of the change in the tilt angle of the detection object does not decrease.
However, as shown in FIG. 5B, when the period Ton is smaller than the activation time Tk, it is impossible for the microcomputer 24 to reliably execute the inclination angle variation detection process within the period Ton. Yes, the detection capability decreases.
For this reason, the power consumption (average current consumption) of the inclination variation detection device 20 is reduced as the period Ton is reduced. However, the period Ton needs to be determined in consideration of the activation time Tk, and the period Ton is reduced to darkness. It is not possible.

Further, the power consumption of the inclination variation detection device 20 is reduced as the period t is increased in order to reduce the time ratio (duty ratio) of the period Ton in the period t.
However, the detection capability in a short time decreases as the period t is increased. For example, when t = 10 sec is set, even if the inclination angle of the detection target fluctuates greatly during several seconds, the fluctuation cannot be detected.
That is, regarding the magnitude of the period t, the power consumption and the detection capability are in a trade-off relationship.

Therefore, for the period t and the period Ton, the optimum values of the above [1-1] are obtained experimentally, and at the same time, the optimum values are experimentally found by cut-and-try so that the detection capability does not decrease. Can be set.
In this way, even when the tilt variation detection device 20 is intermittently operated, the detection capability that is practically inferior to that of the continuous operation can be obtained.

[1-3] If the microcomputer 24 determines that the inclination angle of the detection target has changed in the process of S103 shown in FIG. 4, the microcomputer 24 determines that the detection target has been stolen, and the control signal Ca is generated and output.
Then, according to the control signal Ca, the alarm / notification device 30 performs at least one of generation of an alarm and notification to the manager of the detection target. As a specific method for alarming, for example, an alarm sound is generated from an alarm buzzer or a warning lamp is turned on.
As a result, according to the first embodiment, it is possible to prevent theft. That is, the anti-theft device 10 that prevents the detection object from being stolen can be realized by combining the tilt variation detection device 20 and the alarm / notification device 30.

By the way, when the anti-theft device 10 is mounted on a vehicle and applied to the vehicle as a detection object, it is necessary to monitor the theft when the engine is stopped and the vehicle battery is not charged when the vehicle is parked or stopped. In addition, since power is supplied to the anti-theft device 10 from a vehicle-mounted battery, if the power consumption of the anti-theft device 10 is large, the battery size must be increased because it is necessary to prevent the battery from running out. However, increasing the battery size is unacceptable because it hinders vehicle size reduction, weight reduction, and price reduction.
However, in the first embodiment, since the power consumption of the anti-theft device 10 can be reduced by using the low power consumption tilt variation detection device 20, it is not necessary to increase the size of the in-vehicle battery and is mounted on the vehicle. It is suitable for.

Second Embodiment
The configuration of the second embodiment is the same as that of the first embodiment shown in FIG.
The second embodiment is different from the first embodiment only in the inclination angle variation detection process executed by the microcomputer 24.

6 and 7 are flowcharts showing the flow of the tilt angle variation detection process executed by the microcomputer 24 in the second embodiment.
In the second embodiment, the sampling period at which the microcomputer 24 samples the output signal of the A / D converter 23 is set to one of three stages (2 sec, 100 msec, and 20 msec).

The microcomputer 24 first determines whether or not the sample period is set to the first stage (2 sec) (S201), and if it is set to the first stage (S201: Yes), It is determined whether or not the timing corresponding to one stage is reached (S202), and when the sample timing is reached (S202: Yes), the output signal of the A / D converter 23 is sampled (S203).
The microcomputer 24 performs a software digital filter process that functions as a low-pass filter on the output signal of the A / D converter 23 sampled in the process of S203, thereby removing noise components included in the output signal. (S204).

When the microcomputer 24 determines that the first stage is not set (S201: No), the microcomputer 24 determines whether the sample period is set to the second stage (100 msec) (S205). If it is set to the stage (S205: Yes), it is determined whether or not the timing corresponding to the second stage of the sample period is reached (S206), and at the time when the sample timing is reached (S206: Yes). The output signal of the A / D converter 23 is sampled (S207).
Then, the microcomputer 24 performs a software digital filter process that functions as a low-pass filter on the output signal of the A / D converter 23 sampled in the process of S207, thereby removing a noise component included in the output signal. (S208).

If the microcomputer 24 determines that the second stage is not set (S205: No), the microcomputer 24 determines whether the sample period is set to the third stage (20 msec) (S209). If it is set to the stage (S209: Yes), it is determined whether or not the timing corresponding to the third stage of the sample period has been reached (S210), and when the sample timing is reached (S210: Yes). The output signal of the A / D converter 23 is sampled (S211).
Then, the microcomputer 24 performs a software digital filter process that functions as a low-pass filter on the output signal of the A / D converter 23 sampled in the process of S211 to remove a noise component included in the output signal. (S212).
If the sample period is not set to the third stage (S209: No), the process returns to S201.

Here, in each process of S202, S203, S206, S207, S210, and S211, the sampling period for sampling the output signal of the A / D converter 23 is the period t (the inclination from the sensor power supply device 25) that the microcomputer 24 wakes up. It is set to be the same as the period t) at which power is supplied to the angle sensor 21.
The sample timing for sampling the output signal of the A / D converter 23 is set to be the same as the timing at which the microcomputer 24 wakes up.
That is, the period t and the timing at which the microcomputer 24 wakes up are changed to different values for each process of S203, S207, and S211 in accordance with the sample period and sample timing of each process of S202, S206, and S210. Yes.

When any one of S204, S208, and S212 is completed, the microcomputer 24 determines whether it is time to determine the change in the tilt angle of the detection target (S213), and the tilt angle change determination timing is reached. At the time (S213: Yes), the inclination angle variation determination / sample period setting process is executed (S214), and then the process returns to S201.
Further, when it is not the tilt angle variation determination timing (S213: No), the processing returns to S201.

Here, in the process of S213, the cycle (determination cycle) for determining the variation in the tilt angle of the detection target is set to be the same as the first stage (2 sec) of the sample cycle.
The tilt angle variation determination timing is set to be the same as the timing corresponding to the first stage of the sample period.

FIG. 8 is a flowchart showing the flow of the tilt angle variation determination / sample period setting process (S214) executed by the microcomputer 24 in the second embodiment.
First, similarly to the above [c], the microcomputer 24 calculates the average value of the tilt angles sampled for the first predetermined number of times from the past to the present and the average value of the tilt angles sampled for the second predetermined number of times less than the first predetermined number of times. A difference (angle difference) is obtained, and it is determined whether the difference is equal to or greater than a predetermined threshold (S301). If the difference is less than the predetermined threshold (S301: No), the sample period is set to the first. The stage (2 sec) is set (S302), and then the process proceeds to S201.

  Further, when the difference is equal to or greater than the predetermined threshold (S301: Yes), the microcomputer 24 continues the difference with the third predetermined number of samples from the past to the present as in [d]. Whether the difference is equal to or greater than the predetermined threshold (S303). If the difference is continuously less than the predetermined threshold in the third predetermined number of samples (S303: No), the sample period is set to The second stage (100 msec) is set (S304), and then the process proceeds to S201.

  The microcomputer 24 sets the sample period to the third stage (20 msec) when the difference is continuously equal to or greater than the predetermined threshold value in the third predetermined number of samples (S303: Yes). (S305), and then the process proceeds to S201.

[Operation and Effect of Second Embodiment]
According to the second embodiment, in addition to the operations and effects of [1-1] to [1-3] of the first embodiment, the following operations and effects can be obtained.

[2-1] In the first embodiment, in order to further reduce the power consumption of the tilt variation detection device 20, the time constant is reduced by setting the cut-off frequency of the analog filter 22 low, and the rise characteristic is steep. By doing so, it is only necessary to shorten the activation time Tk required until the tilt variation detection device 20 can operate stably.
In this case, since the noise removal capability of the analog filter 22 is reduced, the microcomputer 24 performs software digital filter processing that functions as a low-pass filter on the output signal of the A / D converter 23, and outputs the output signal. What is necessary is just to remove the noise component contained in.

Incidentally, the noise component included in the output signal of the A / D converter 23 is generated due to the following causes.
[A] Noise generated by the sensors (acceleration sensor, height sensor, etc.) constituting the tilt angle sensor 21 itself.
[A] Noise generated by an amplifier built in the tilt angle sensor 21.
[C] Noise caused by vibration or impact generated on the object to be detected. For example, when the object to be detected is a vehicle, when another vehicle passes near the parked vehicle, when the vehicle is exposed to a strong wind, when a passerby's body contacts the parked vehicle, Vibration or shock may occur.

Thus, when the digital filter processing is performed by the microcomputer 24, according to Shannon's sampling theorem, it is more than twice the maximum frequency that the microcomputer 24 wants to use to determine the variation in the tilt angle of the detection object in the processing of S103. The output signal of the A / D converter 23 must be sampled at the frequency in the processing of S101 and S102.
However, since the sampling period is set to be the same as the period t and the period t is set as described in [1-2], the highest frequency is naturally determined according to the period t. It was.

Therefore, the noise component in the band from the half of the sample frequency (= the cutoff frequency in the digital filter processing) to the cutoff frequency of the analog filter 22 cannot be removed even by the digital filter processing of the microcomputer 24. The noise component may reduce the ability to detect the change in the tilt angle of the detection target.
As a result, in the first embodiment, a decrease in the detection capability of the inclination variation detection device 20 may cause an erroneous determination of the antitheft device 10, which may cause a decrease in reliability of the antitheft device 10.

For example, when the detection target is a vehicle, the vehicle vibration frequency determined from the vehicle spring constant is assumed to be 0.8 to 1.0 Hz.
Further, it is assumed that the cutoff frequency of the analog filter 22 is 10 Hz.
At this time, if the period t (= sampling period) is 1 sec, the sample frequency is 1 / t and thus 1.0 Hz, and the half of the sample frequency is 0.5 Hz.

As a result, in the first embodiment, due to the causes [A] and [A], a noise component of 0.5 to 10 Hz, which is a band from a half frequency of the sample frequency to the cutoff frequency of the analog filter 22, is generated. When included in the output signal of the A / D converter 23, the detection capability is reduced by the noise component.
In addition, when vibration / impact of 0.5 to 1.0 Hz, which is a band from 1/2 of the sample frequency to the upper limit value of the vibration frequency of the vehicle, is generated in the vehicle due to the above [c] When a noise component due to vibration / impact is included in the output signal of the A / D converter 23, the detection capability is reduced by the noise component.

  [2-2] On the other hand, in the second embodiment, since the sample period is set to three stages (2 sec, 100 msec, and 20 msec), the frequency band of the noise component is different for each stage of the sample period.

<In the case of the first stage (2 sec)>
When the period t (= sample period) is in the first stage (2 sec), the sample frequency is 1 / t and thus 0.5 Hz, and the half of the sample frequency is 0.25 Hz.
As a result, due to the causes [A] and [A], a noise component of 0.25 to 10 Hz, which is a band from a half frequency of the sample frequency to the cutoff frequency of the analog filter 22, is generated by the A / D converter 23. When included in the output signal, the detection capability is reduced by the noise component.
In addition, when vibration / impact of 0.25 to 1.0 Hz, which is a band from 1/2 of the sample frequency to the upper limit value of the vibration frequency of the vehicle, is generated in the vehicle due to the above [c] When a noise component due to vibration / impact is included in the output signal of the A / D converter 23, the detection capability is reduced by the noise component.

<In the case of the second stage (100 msec)>
When the period t (= sample period) is in the second stage (100 msec), the sample frequency is 1 / t and thus becomes 10 Hz, and the half of the sample frequency is 5 Hz.
As a result, due to the causes [A] and [A], a noise component of 5 to 10 Hz, which is a band from a half frequency of the sample frequency to the cutoff frequency of the analog filter 22, is output from the A / D converter 23. If it is included, the detection capability is reduced by the noise component.
However, since the half of the sample frequency is 5 Hz, which is sufficiently higher than 1.0 Hz, which is the upper limit value of the vehicle vibration frequency, noise due to the vibration frequency of the vehicle is caused by the above [c]. Even when a component is included in the output signal of the A / D converter 23, the detection capability is not reduced by the noise component.

<In the case of the third stage (20 msec)>
When the period t (= sample period) is in the third stage (20 msec), the sample frequency is 1 / t and thus 50 Hz, and the half of the sample frequency is 25 Hz.
As a result, since the half frequency of the sample frequency (cutoff frequency in the digital filter processing) is sufficiently higher than 10 Hz that is the cutoff frequency of the analog filter 22, noise components that cannot be removed by the analog filter 22. Also, it can be almost completely removed by the digital filter processing of the microcomputer 24, and the detection capability is not lowered by the noise component.
Moreover, since the half of the sample frequency is 25 Hz, which is much higher than 1.0 Hz, which is the upper limit value of the vehicle vibration frequency, the noise component caused by the vehicle vibration frequency is A / D converter 23. Even if the output signal is included in the output signal, the detection capability is not reduced by the noise component.

[2-3] In the second embodiment, since the sample period is set to three stages, the average consumption current Ia of the inclination variation detection device 20 is different for each stage of the sample period.
Similar to the first embodiment, also in the second embodiment, the average current consumption Ia when the tilt variation detection device 20 is intermittently operated can be obtained from Equation 2.
For example, assume that Ton = 10 msec, Ion = 20 mA, and Ioff = 1 mA.

<In the case of the first stage (2 sec)>
When the period t is in the first stage (t = 2 sec), Toff = 1990 msec, so that the average current consumption Ia = 1.015 mA, which is further than the average current consumption Ia = 1.19 mA in the first embodiment. Since it becomes smaller, power consumption can be greatly reduced.

<In the case of the second stage (100 msec)>
When the period t is in the second stage (t = 100 msec), Toff = 90 msec, so that the average consumption current Ia = 2.9 mA, which is compared with the average consumption current Ia = 1.19 mA in the first embodiment. Although it increases, the power consumption can be reduced because it is much smaller than the average current consumption Ia = 20 mA when the tilt variation detection device 20 is continuously operated (conventional form).

<In the case of the third stage (20 msec)>
When the period t is the third stage (t = 20 msec), Toff = 10 msec, so that the average consumption current Ia = 10.5 mA, which is compared with the average consumption current Ia = 1.19 mA in the first embodiment. Although it increases, the power consumption can be reduced because it is smaller than the average current consumption Ia = 20 mA when the tilt variation detection device 20 is continuously operated (conventional embodiment).

[2-4] The method [d] can detect a change in the tilt angle of the detection object with higher accuracy than the method [c].
For this reason, when it is determined by the method [d] that the tilt angle of the detection target is fluctuating, there is a high possibility that the tilt angle of the detection target is actually fluctuating.
In addition, when it is determined that the tilt angle of the detection target is changed only by the method [c], the tilt angle of the detection target is not actually changed, and vibration or impact is applied. Could only be.

Therefore, when it is determined by the method [c] that the tilt angle of the detection target has not changed (S301: No), the detection target may be regarded as stationary.
Further, it is determined that the tilt angle of the detection target is changed by the method [c] (S301: Yes), and the tilt angle of the detection target is not changed by the method [d]. When it is determined (S303: No), it may be considered that the detection target may be subjected to vibration or impact.
Then, it is determined that the tilt angle of the detection object is changed by the method [c] (S301: Yes), and the tilt angle of the detection object is changed by the method [d]. If it is determined (S303: Yes), it may be considered that the inclination angle of the detection target may actually vary.

Therefore, when it is determined that the detection target is stationary (S301: No), the detection capability is reduced by setting the sampling period to the largest first stage (2 sec), but the power consumption is reduced. Is minimized.
When it is determined that there is a possibility that the detection target has been subjected to vibration or impact (S303: No), the power consumption and the above-mentioned are set by setting the sample period to the second intermediate stage (100 msec). The detection capability is also in the middle.
If it is determined that there is a possibility that the tilt angle of the detection target is actually fluctuating (S303: Yes), the sample period is set to the minimum third stage (20 msec). Although the power increases, the detection capability is greatly enhanced.

  In other words, in the second embodiment, when it is determined in the process of S301 that the detection target is stationary (S301: No), the sample period is set to the largest first stage (2 sec). (S302). If it is determined in S301 and S303 that the detection target may have been subjected to vibration or impact (S303: No), the sample period is set to the second intermediate stage (100 msec). (S304). If it is determined in S301 and S303 that there is a possibility that the tilt angle of the detection object actually fluctuates (S303: Yes), the third stage (20 msec) with the smallest sample period. (S305).

  In other words, in the second embodiment, the possibility that the inclination angle of the detection object actually fluctuates is determined based on the past fluctuation state of the inclination angle of the detection object (S301, S303). The higher the is, the smaller the sample period is changed (S302, S304, S305).

As described above, in the second embodiment, in the tilt angle variation determination / sample cycle setting process (S214: S301 to S305), the sample cycle is divided into three stages (2 sec) according to the past variation state of the tilt angle of the detection target. , 100 msec, 20 msec), it is possible to achieve both an improvement in economy due to a reduction in power consumption and an improvement in the ability to detect fluctuations in the tilt angle of the detection target.
The sample periods of the first to third stages are not limited to the specific example (2 sec, 100 msec, 20 msec) of the second embodiment, and may be set by finding an optimum value experimentally by cut-and-try.

<Another embodiment>
The present invention is not limited to the above-described embodiments, and may be embodied as follows. Even in this case, operations and effects equivalent to or higher than those of the above-described embodiments can be obtained.

[1] In the second embodiment, the period (determination period) for determining the change in the tilt angle of the detection target in the processes of S213 and S214 is set to be the same as the first stage (2 sec) of the sample period.
The tilt angle variation determination timing is set to be the same as the timing corresponding to the first stage of the sample period.
However, it is not necessary to set the determination period to be the same as the first stage (2 sec) of the sample period, and it is not necessary to set the tilt angle variation determination timing to be the same as the timing corresponding to the first stage of the sample period.

The determination period may be set to any period as long as it is less than or equal to the maximum period determined by performing a simulation experiment for stealing a detection target. For example, when the object to be detected is a vehicle, it usually takes 10 seconds or more to jack up the vehicle and steal the vehicle body or wheels, so the maximum cycle may be set to 10 seconds.
Incidentally, the first stage (2 sec in the second embodiment), which is the maximum value of the period t (= sample period), needs to be set to be equal to or less than the determination period.

Note that, as the determination period is increased, the detection capability of the change in the tilt angle of the detection target decreases, but the number of times the microcomputer 24 executes the process of S214 decreases, so that the power consumption of the microcomputer 24 can be reduced. In other words, the power consumption and the detection capability are in a trade-off relationship with respect to the size of the determination period.
Therefore, the determination period may be set by experimentally finding an optimum value by cut-and-try, taking into consideration power consumption and the detection capability.

  [2] In the second embodiment, the difference between the average value of the tilt angles sampled for the first predetermined number of times from the past to the present and the average value of the tilt angles sampled for the second predetermined number of times less than the first predetermined number of times is obtained. If the difference is less than the predetermined threshold (S301: No), the sample period is set to the first stage (2 sec) (S302).

At this time, the predetermined threshold value may be set in a plurality of stages, and the first stage may be further divided into a plurality of stages.
For example, the predetermined threshold value is set in two steps of a first threshold value and a second threshold value (second threshold value> first threshold value), and the first step value is α step. , Β stage and γ stage (α stage sampling period> β stage sampling period> γ stage sampling period).

In this case, when the difference is less than the first threshold, the sampling period is set to α stage (for example, 6 sec), and when the difference is greater than or equal to the first threshold and less than the second threshold. The sample period is set to β stage (for example, 4 seconds), and when the difference is not less than the first threshold value and less than the second threshold value, the sample period is set to γ stage (for example, 2 seconds).
That is, the sample period is set smaller as the difference exceeds a larger threshold value.

  Thus, if the first stage is further divided into a plurality of stages, it becomes possible to optimize by setting the sample period more finely according to the past fluctuation state of the tilt angle of the detection target. As a result, the power consumption can be further reduced.

  [3] In the second embodiment, when the difference is equal to or greater than the predetermined threshold value (S301: Yes), and the difference is continuously calculated with the third predetermined number of samples from the past to the present. If it is equal to or greater than the threshold (S303: Yes), the sample period is set to the third stage (20 msec) (S305).

At this time, the third predetermined number of times may be set in a plurality of stages, and the third stage may be further divided into a plurality of stages.
For example, the third predetermined number of times is set in two stages of number δ and number of times ε (number of times ε> number of times δ), and the third stage is divided into three stages of η stage, ρ stage, and σ stage. Alternatively, the sample period of η stage> the sample period of ρ stage> the sample period of σ stage.

In this case, when the difference is continuously less than the predetermined threshold value less than the number of times δ (for example, 5 times), the sample period is set to η step (for example, 70 msec), and the difference is If the number δ is equal to or greater than the number δ and less than the number ε (for example, 10 times) continuously, the sample period is set to ρ steps (for example, 50 msec), and the difference is equal to the number ε If it is continuously greater than or equal to the predetermined threshold (for example, 10 times) or more, the sample period is set to σ stage (for example, 20 msec).
That is, the sample period is set to be smaller as the number of times the difference continuously exceeds the threshold value increases.

  Thus, if the third stage is further divided into a plurality of stages, it becomes possible to optimize by setting the sample period more finely according to the past fluctuation state of the tilt angle of the detection target. As a result, the power consumption can be further reduced.

[4] In each of the above embodiments, the sensor power supply device 25 supplies power to the tilt angle sensor 21 when the control signal Cb is at a high level (power on), and tilt angle when the control signal Cb is at a low level. The power supply to the sensor 21 is cut off (power off).
However, when the control signal Cb is at a low level, the power supply to the tilt angle sensor 21 is not interrupted, but at least one of the voltage and current of the power supplied to the tilt angle sensor 21 is reduced to thereby control the control signal Cb. The tilt angle sensor 21 may be placed in a standby state when Cb is at a low level.
In the standby state of the sensor 21, power consumption is smaller than that in the operating state.

That is, the sensor power supply device 25 may be brought into a non-operating state by reducing at least one of the voltage and current of the power supplied to the tilt angle sensor 21.
In this way, it is possible to reduce the time required until the operation of the tilt angle sensor 21 can be stably used in the period Ton, and it is necessary until the tilt variation detection device 20 can be stably operated. The activation time Tk can also be shortened.

[5] In each of the embodiments described above, the sensor power supply device 25 switches the supply / cutoff of power to the tilt angle sensor 21 (power on / off) according to the control signal Cb.
However, as shown in FIG. 9, when the operation of the tilt angle sensor 21 is driven and controlled by the control clock generated by the microcomputer 24, the microcomputer 24 stops the output of the control clock so that the operation of the tilt angle sensor 21 is performed. Or the microcomputer 24 may make the operation of the tilt angle sensor 21 stand by by increasing the period of the control clock.

That is, the microcomputer 24 is put into an operating state by outputting a control clock to the tilt angle sensor 21, and stops outputting the control clock to the tilt angle sensor 21, or is increased by increasing the cycle of the control clock. You may make it an operation state.
In this way, the control signal Cb and the sensor power supply device 25 can be omitted as shown in FIG. 9 after obtaining the same operation and effect as the above embodiments.

[6] In the second embodiment, software digital filter processing that functions as a low-pass filter is performed on the output signal of the A / D converter 23 in the processing of S204, S208, and S212.
However, a digital filter may be provided as hardware, and the processing of S204, S208, and S212 may be performed by the hardware digital filter.

1 is a block diagram illustrating a configuration of an antitheft device 10 according to a first embodiment that embodies the present invention. It is explanatory drawing for demonstrating the system which uses an acceleration sensor as the inclination-angle sensor. It is a characteristic view which shows the timing chart of the control signal Cb in 1st Embodiment, and the fluctuation characteristic of the consumption current of the inclination fluctuation | variation detection apparatus 20. FIG. It is a flowchart which shows the flow of the inclination angle fluctuation | variation detection process which the microcomputer 24 performs in 1st Embodiment. It is explanatory drawing for demonstrating the relationship between the starting characteristic of the inclination fluctuation | variation detection apparatus 20, and the period Ton. It is a flowchart which shows the flow of the inclination angle fluctuation | variation detection process which the microcomputer 24 performs in 2nd Embodiment which actualized this invention. It is a flowchart which shows the flow of the inclination angle fluctuation | variation detection process which the microcomputer 24 performs in 2nd Embodiment. It is a flowchart which shows the flow of the inclination-angle fluctuation | variation determination and sample period setting process (S214) which the microcomputer 24 performs in 2nd Embodiment. It is a block diagram which shows the structure of the antitheft device 10 of another embodiment which actualized this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Anti-theft device 20 ... Inclination fluctuation detection device 30 ... Alarm / notification device (notification means)
21 ... Inclination angle sensor (inclination angle detection means)
22 ... Analog filter 23 ... A / D converter 24 ... Microcomputer (determination means, switching means)
25. Sensor power supply device (switching means)
24a ... Central processing unit (CPU)
24b ... Read-only storage device (ROM)
24c: Read / write storage device (RAM)
24d: Input / output device (I / O) 24d
24e ... Timer Ca, Cb ... Control signal Vcc ... DC power supply t ... Period Ton, Toff ... Period Ion, Ioff ... Current consumption Ia ... Average current consumption

Claims (2)

An inclination angle detecting means for detecting an inclination angle of the detection object;
Determination means for determining a change in the inclination angle of the detection object based on the inclination angle detected by the inclination angle detection means;
An inclination variation detection device comprising a switching means for switching each of the inclination angle detection means and the determination means to either an operating state or a non-operating state,
The determination means determines a possibility that the inclination angle of the detection target is actually changed based on a past fluctuation state of the inclination angle;
It said switching means when the switch between the intermittently the tilt angle detecting means and the judging means for a predetermined time period in the operating state at predetermined intervals, the higher the possibility that the determination means determines, the tilt angle detecting The predetermined cycle for switching the means and the determination unit to the operating state is changed small, and the change of the predetermined cycle is divided into a plurality of stages of three or more stages;
The tilt angle detecting means and the determination means inclined variation detecting apparatus characterized that the the <br/> power consumption is smaller than that when the operation state when the non-operating state. A tilt variation detection device according to claim 1 ;
An anti-theft device comprising an informing unit that performs at least one of generating an alarm and notifying an administrator of an object to be detected based on a determination result of the determining unit of the inclination variation detecting device. .

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