JP3491543B2 - Vehicle speed detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed detecting device, and more particularly to a vehicle speed detecting device suitable for calculating a vehicle speed and a moving distance in a vehicle-mounted navigation device.

[0002]

2. Description of the Related Art In a vehicle-mounted navigation device, for example, in order to obtain the travel distance of a vehicle from a certain point O ₀ by autonomous navigation, the rotational speed of a wheel is obtained from the output of a wheel speed sensor, and the rotational speed and the wheel The vehicle speed v is calculated from the length of the outer circumference, and this vehicle speed v is time-integrated (double integration by the time t) to calculate the moving distance. When the wheel speed sensor is a rotation pulse generator type that generates n (n is an integer of 1 or more) pulses per one rotation of the wheel, the rotation speed can be determined by measuring the period T between the pulses (1 / ( nT) corresponds to the rotation speed), and can also be found by counting the number C of pulses generated per certain unit time t ₀ (C / (n
t ₀ ) corresponds to the rotation speed). In the case where the wheel speed sensor is a magnetic sensor that detects the intensity of magnetism magnetized to the wheel, the output of the magnetic sensor changes periodically as the wheel rotates (one cycle change per wheel rotation. 18), the rotation speed can be known by measuring the time T between peaks generated in the output of the magnetic sensor (1 / T corresponds to the rotation speed), and the number of peaks C generated per certain unit time t ₀ It is also known by counting (C / t ₀ corresponds to the rotation speed).

FIG. 19 is a block diagram of a vehicle speed detection system of a conventional vehicle-mounted navigation device. 1 is a wheel, 2 is a wheel 1
A rotation pulse generator that generates n pulses (where n is an integer of 1 or more) per rotation, and 3 counts and counts the pulses output from the rotation pulse generator 2 every unit time t ₀ (sec). The measurement circuit 4 that outputs the value data C is a microcomputer. The count value data C counted by the measurement circuit 3 is read, and the length of the outer circumference of the wheel 1 is set to L (m), and v = LC / (nt ₀ ) (m / sec) ··· The vehicle speed v is calculated from the formula (1) and output.

[0004]

However, there are various sizes of wheels, and when the vehicle speed is calculated with the length L of the outer circumference of the wheel as a standard fixed value, the difference from the actual wheel is calculated. A calculation error will occur by the amount. In particular, a large cumulative error occurs when the travel distance is obtained by autonomous navigation. The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a vehicle speed detection device capable of accurately detecting a vehicle speed with a simple configuration.

[0005]

In the vehicle speed detecting device according to the first aspect of the present invention, there are provided a rotational speed detecting means for detecting the rotational speed of the wheels, an acceleration detecting means for detecting the acceleration of the vehicle, and an acceleration detecting means. A reference vehicle speed is calculated using the detected acceleration, and an estimation means for estimating the outer circumference of the wheel from the reference vehicle speed and the rotation speed detected by the rotation speed detection means, and the rotation detected by the rotation speed detection means Vehicle speed calculation means for calculating the vehicle speed using the speed and the length of the outer circumference of the wheel estimated by the estimation means. According to this vehicle speed detection device, the acceleration of the vehicle is detected, the reference vehicle speed is calculated using the acceleration, and the length of the outer circumference of the wheel is estimated from the reference vehicle speed and the rotation speed detected by the rotation speed detection means. To do. Then, since the vehicle speed is calculated using the rotation speed detected by the rotation speed detecting means and the outer circumference length of the wheel estimated by the estimating means, a value close to the actual outer circumference length of the wheel is used. It becomes possible to calculate the vehicle speed with a small error, and since the reference vehicle speed is calculated by a system different from the rotation speed detecting means, it is not necessary to use an expensive and complicated device such as a GPS receiver, and the burden on the configuration is reduced. Few . In the vehicle speed detecting device according to the second aspect of the present invention, the rotation speed detecting means is provided near the wheel, and the magnetic detecting means for detecting the magnetism of the wheel in a non-contact manner and the cycle of change in the detection output of the magnetic detecting means. And a measuring means for measuring. Thus, the rotation speed detecting means can be realized with a relatively simple structure .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of a vehicle speed detection system of a vehicle-mounted navigation device according to the present invention, and the same components as those in FIG. 19 are designated by the same reference numerals. 1 is a wheel, 2 is a rotation pulse generator that generates n pulses per rotation of the wheel (where n is an integer of 1 or more), 3 is a predetermined number of pulses output from the rotation pulse generator 2 A measuring circuit that counts every unit time t ₀ (sec) and outputs count value data C (see FIG. 4, t.
₀ is a numerical value such as 1, 2, 5, 10 or the like), and 4A is a microcomputer, which reads the count value data DC output from the measurement circuit 3 during autonomous navigation to
Let L (m) be the length of the outer circumference of the vehicle, and calculate and output the vehicle speed v from the equation (1). Each time the microcomputer 4A starts the autonomous navigation for one time, after the autonomous navigation is started, the vehicle speed v is integrated over time to calculate the moving distance R _SE from the autonomous navigation start point O ₀ by the autonomous navigation.

When the microcomputer 4A calculates the vehicle speed v and the moving distance R _SE for the first time by autonomous navigation, L in the equation (1) is set to L in the formula (1) in advance. A predetermined standard value L ₀ (stored in the built-in memory at the time of shipment) is used, but the estimated value L ′ is used after the estimated value L ′ is obtained by the method described later.

Reference numeral 5 denotes an acceleration sensor which is provided at a predetermined position of the vehicle and detects an acceleration in the front-rear direction and outputs a detection voltage proportional to the acceleration. Reference numeral 6 denotes the detection voltage of the acceleration sensor 5 at a predetermined sampling frequency A / The A / D converter D-converts and outputs acceleration data DA. Since the microcomputer 4A starts from O ₀ , the vehicle speed v and the traveling distance R
_In parallel with the calculation of _SE , the acceleration indicated by the acceleration data DA is time-integrated based on the acceleration data DA and the reference vehicle speed v _{ref is} calculated.
To calculate. Then, after the autonomous navigation is started from O ₀ , when the traveling distance R reaches a predetermined value, the outer peripheral length of the wheel 1 is estimated from the vehicle speed v and the reference vehicle speed v _ref at that time using the following equation. The value L'is calculated and stored in the built-in memory. L ′ = v _ref · (nt ₀ / C) ··· (2) Then, in the following, L in the equation (1) is obtained by the equation (2).
To calculate the vehicle speed by autonomous navigation and minimize the error. Hereinafter, the estimation is performed again each time the autonomous navigation is newly started, and L ′ used in the calculation of the equation (1) is updated.

Next, the operation of the above-described embodiment will be described with reference to FIGS. 2 and 3 are flowcharts showing the autonomous navigation processing by the microcomputer 4A,
FIG. 4 is an explanatory diagram of a method of measuring the rotation speed. Note that, first, it is assumed that the vehicle is stopped at a certain point O ₀ , the moving distance R _{SE is} 0, and the reference vehicle speed v _ref = 0 obtained from the acceleration detected by the acceleration sensor 5 is set. .
Further, the built-in memory stores the standard value L ₀ of the outer peripheral length of the wheel 1 written by the manufacturer before shipment,
It is assumed that the estimated value L ′ of the outer circumference of the wheel 1 does not yet exist.

(1) When the vehicle is stopped When the vehicle is stopped at a certain point O ₀ , the rotation pulse generator 2 does not output a pulse because the wheel 1 does not rotate.
Since the measuring circuit 3 cannot count the pulses, the values of the pulse count value data C for each unit time t ₀ are all 0 (see C ₋₁ and C _{0 in} FIG. 4 (1)). On the other hand, while the vehicle is stopped,
The acceleration sensor 5 outputs a detection voltage corresponding to acceleration = 0, and the A / D converter 6 outputs a sampling cycle T ₀ (sec).
To A / D convert and output acceleration data DA. When the microcomputer 4A is stopped, A /
When new data DA is output from the D converter 6, the new data DA is read and the reference vehicle speed v _ref is calculated by the following equation with the acceleration indicated by DA being α (m / sec ² ) (steps S1 and S2 in FIG. 2). ). v _ref ← v _ref + αT ₀ (m / sec) ··· (3)

Then, it is checked whether or not the count value data C indicating the first value other than 0 is output from the measuring circuit 3 (step S3). If C = 0, the answer is NO.
Returning to step S1, the same processing is repeated. Stopped,
Since all the accelerations indicated by the acceleration data DA output from the A / D converter 6 are 0, v _ref remains 0.

(2) When the vehicle starts traveling from the point O ₀ after the start of traveling, the acceleration sensor 5 outputs a detection voltage indicating a positive acceleration while the vehicle is accelerating, and the A / D converter 6 Is A / D converted and output. Therefore, by the processing of steps S1 and S2, v
_ref gradually increases from 0. Incidentally, the acceleration sensor 5
Outputs a detection voltage indicating zero acceleration while the vehicle is traveling at a constant speed, and outputs a detection voltage indicating negative acceleration while the vehicle is decelerating. On the other hand, when the vehicle 1 starts traveling, the wheel 1 rotates at a speed corresponding to the traveling speed, and the rotation pulse generator 2 generates n pulses while the wheel 1 makes one rotation.
As shown in (1) of FIG. 4, the measuring circuit 3 sequentially measures the number of pulses for each unit time t ₀ , and outputs count value data C = C ₁ , C ₂ , ... Each time the measurement is completed. When the first count value data C = C ₁ indicating a value other than 0 is output from the measurement circuit 3, the microcomputer 4A starts calculation of the vehicle speed and the movement distance from O ₀ by autonomous navigation (YES in step S3, S4). ).

Specifically, first, the timer used to determine whether or not the vehicle has stopped is stopped (step S
4) It is checked whether the estimated value L'exists in the built-in memory (step S5). Since it is NO, L ← L ₀ is set (step S6), and the first count value data C = C ₁ which indicates a count value other than 0 The vehicle speed v is calculated by using the following equation and is output to the outside. v ← LC / (nt ₀ ) (m / sec) ··· (4) Furthermore, using v obtained by the equation (4), the moving distance R _SE from O ₀ is calculated by the following equation and output to the outside. (Step S
7). R _SE ← R _SE + vt ₀ (m) ··· (5)

Next, it is checked whether new acceleration data DA is output from the A / D converter 6 (step S in FIG. 3).
8) If NO, the process proceeds to step S10, but if YES, the reference vehicle speed v _ref is calculated in step S9 by the equation (3) with the acceleration indicated by the current DA set as α. Then, the moving distance R _SE from O ₀ is a predetermined threshold value R _C (R _C is a certain fixed value, for example, 1 km, 5 k
m, 10 km, etc.) is checked for the first time (step S10), because it is not here yet,
It is checked whether or not the next count value data C indicating a value other than 0 is output from the measuring circuit 3 (step S11). If not, check if the timer is counting (step S1
2) Since it is NO here, the timer is started (step S13). Then, returning to step S8, the A / D
It is checked whether new acceleration data DA is output from the converter 6, and if NO, the process proceeds to step S10 and YES.
If so, the process proceeds to step S9, the reference vehicle speed v _ref is calculated, and then the process proceeds to step S10.

If the result of the determination in step S10 is still NO, the process proceeds to step S11, in which it is checked whether the measurement circuit 3 has output the next count value data C other than 0. If not yet output, the timer is currently since time counting operation (YES determination at step S12), the measured time T _tm of the timer is checked whether exceeds a predetermined threshold value T _C (step S14). T _C is sufficient time to determine that the vehicle is stopped, for example, 1 minute, 5
It is set to minutes or the like, and the answer is NO during traveling, and the process returns to step S8 to repeat the same processing.

After that, when the next count value data C = C ₂ indicating a value other than 0 is output from the measuring circuit 3, the timer is once stopped (YES in step S11, S15),
Returning to step S5, it is checked whether the estimated value L'exists in the internal memory. Since it is still NO, L ← L ₀ is set (step S6), and using this time C = C ₂ , (4),
The vehicle speed v and the moving distance R _SE are calculated by the equation (5) and output to the outside (step S7). Next, it is checked whether new acceleration data DA is output from the A / D converter 6, and N
If O, the process proceeds to step S10, but if YES,
In step S9, the reference vehicle speed _vref is calculated by the equation (3), where α is the acceleration indicated by the current DA. Less than,
The same process is repeated to calculate the vehicle speed v and the moving distance R _SE using the standard value L ₀ based on the output of the measurement circuit 3, and the reference vehicle speed v _ref based on the output of the acceleration sensor 5.

After that, when moving from O ₀ by R _C and YES is obtained in step S10, the microcomputer 4A
Is an estimated value L ′ of the outer circumference of the wheel 1 calculated by the following equation, where C is the count value measured by the latest measurement circuit 3.
It is stored in the built-in memory (step S16). L ′ ← v _ref · (nt ₀ / C) (m) ··· (6) This L ′ is closer to the actual length of the outer circumference of the wheel 1 than the standard value L ₀ set by the manufacturer. . After that, when the next count value data C indicating a value other than 0 is output from the measurement circuit 3, the microcomputer 4A determines YES in the check in step S5, and sets L ← L '(step S
17), (4), and (5) according to vehicle speed v and travel distance R _SE
Is calculated (step S7). Therefore, it is possible to reduce the calculation error of the vehicle speed v and suppress the increase of the accumulated error of the moving distance R _SE .

After that, when the vehicle decelerates and stops, the rotation of the wheel 1 stops and the pulse output from the rotation pulse generator 2 stops. At this time, the count value data C output from the measurement circuit 3 is gradually reduced to finally 0 (FIG. 4).
(See C _k-2 , C _k-1 , and C _{k in} (2)). Then, the microcomputer 4A repeatedly determines NO in step S11, and the timer counts. Then, when the measured time T _tm exceeds the threshold value T _C , YES is determined in step S14, v _ref and R _SE are initialized to 0, and the process returns to step S1 to enter the standby state for the next running ( Step S18).

When the next running is started, the microcomputer 4A starts the second autonomous navigation from the time when the first count value data C indicating a value other than 0 is output from the measuring circuit 3, but the previous autonomous navigation is started. When the estimated value L ′ of the outer circumference of the wheel 1 is obtained by the above, the vehicle speed v and the moving distance R _SE are calculated from the beginning using the estimated value L ′ (YES in step S5, S17). , S7), the calculation with a small error is possible from the beginning.

According to this embodiment, the rotation speed is measured by counting the pulses output from the rotation pulse generator 2 as the wheel speed sensor at every unit time t ₀ , and the rotation speed is measured in parallel therewith. to a reference vehicle speed v _ref and calculates the output of the acceleration sensor 5 installed in the vehicle time integral to, the rotational speed of the wheel 1 measured by v _ref and the measurement circuit 3 at a certain timing of the outer circumference of the wheel 1 length Since the vehicle speed v and the travel distance R _SE are calculated by autonomous navigation using the estimated value and the rotation speed measured by the measurement circuit 3,
It is possible to calculate the vehicle speed v and the moving distance R _SE with a small error by using a value close to the actual outer circumference of the wheel 1. Moreover,
In order to calculate the reference vehicle speed with a system different from the wheel speed sensor, G
You don't have to use expensive and complicated equipment such as PS receiver,
There is little structural burden.

In the above embodiment, the acceleration detected by the acceleration sensor 5 is integrated over time to obtain the reference vehicle speed v.
_ref is calculated, and the reference vehicle speed v _ref and the rotation pulse generator 2 are calculated.
The estimated value L ′ of the outer circumference of the wheel 1 is calculated from the rotation speed of the wheel 1 detected by the measurement circuit 3 and the acceleration detected by the acceleration sensor 5 is integrated over time to perform the reference movement. The distance L is calculated by multiplying the convenient outer circumference length L of the wheel 1 by a ratio with the travel distance obtained by autonomous navigation using the convenient outer circumference length L of the wheel 1. The estimated value L ′ of the length of the outer circumference may be calculated.

Specifically, the flowcharts of FIGS. 2 and 3 are modified as shown in FIGS. 5 and 6, and step S of FIGS.
2, in steps S2 ′ and S9 ′ corresponding to S9,
In addition to calculating the reference vehicle speed v _ref by the formula (3), the reference moving distance R _ref from the autonomous navigation start point is calculated according to the following formula. R _ref ← R _ref + v _ref · T ₀ ··· (7) However, the reference movement distance R _ref is initialized to 0 at the time of starting the flowchart of FIG. 5 and at step S18 ′ corresponding to step S18 of FIG. To be done.

Then, when the vehicle moves by R _C from the autonomous navigation start point and becomes YES in step S10, an estimated value L'of the outer circumference of the wheel 1 is calculated by the following equation (step S16 '). L ′ ← L · (R _ref / R _SE ) ·· (8) For L in the above formula, L ₀ set by the manufacturer before shipment immediately after the start of the first autonomous navigation is conveniently used. (NO in step S5, step S6). If the estimated value L ′ has already been obtained last time, the previously obtained L ′ is used for convenience (YES in step S5, S17). Also in the examples of FIGS. 5 and 6, it is possible to calculate the vehicle speed v and the moving distance R _SE with a small error by using a value close to the actual outer peripheral length of the wheel 1, and a system separate from the wheel speed sensor. Therefore, it is not necessary to use an expensive and complicated device such as a GPS receiver to calculate the reference vehicle speed, and the burden on the configuration is small.

Further, in step S7 of FIG.
Instead of calculating the moving distance R _SE by the equation (5), the cumulative rotational speed RT _SE of the wheel 1 from the autonomous navigation start point O ₀ is calculated by the following equation. RT _SE ← RT _SE + (C / n) (times) (5) 'Then, in step S10, RT _SE is a certain threshold value R.
It is checked whether T _C (RT _C is, for example, a value corresponding to traveling of about 1 km, 5 km, 10 km) is exceeded, and in step S16 ′, instead of calculating the estimated value L ′ by the formula (8), It may be calculated by the following formula. L '← R _ref / RT _SE ··· (8) ′ In this case, RT _SE starts when the process of FIG.
In step S18 ', R _SE is set to 0.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a block diagram showing the configuration of the vehicle speed detection system of the vehicle-mounted navigation device according to the present invention, and the same components as those in FIG. 1 are designated by the same reference numerals. Reference numeral 1 is a wheel, and 7 is a magnetic sensor for detecting the magnetism naturally magnetized to the wheel, which outputs a detection voltage having a magnitude proportional to the strength of the magnetism. Normally, since the steel radial type wheel 1 is naturally magnetized, the detection voltage of the magnetic sensor 7 periodically changes as the wheel 1 rotates, as shown in FIG. Two adjacent upper peaks P ₁ and P of the waveform of FIG.
The time interval of _{2 is} the cycle T required for one rotation of the wheel 1,
The rotation speed is 1 / T (times / sec). Reference numeral 8 is an A / D converter for A / D converting the detection voltage of the magnetic sensor 7 at a predetermined sampling period and outputting magnetic detection data DM, 4B
Is a microcomputer, which reads the magnetic detection data DM output from the A / D converter 8 during autonomous navigation and additionally stores it in a built-in memory (not shown), and a predetermined unit time t ₀ (sec) New magnetic detection data DM
The rotational speed of the wheel 1 is detected by counting the number of peak occurrences C during the time t ₀ , and the outer peripheral length of the wheel 1 is L (m), and the vehicle speed v is calculated from the following equation. Are output (however, t ₀ is a value such as 1, 2, 5, 10, etc., see FIG. 10). v = LC / t ₀ (m / sec) ··· (9) Each time the microcomputer 4B starts the autonomous navigation, it starts the autonomous navigation and then integrates the vehicle speed v by time to perform the autonomous navigation. The moving distance R _SE from the autonomous navigation start point O ₀ is calculated.

When the microcomputer 4B calculates the vehicle speed v and the moving distance R _SE by the autonomous navigation for the first time, L in the equation (9) is set to a certain value which is preset by the manufacturer of the device. A predetermined standard value L ₀ (stored in the built-in memory at the time of shipment) is used, but the estimated value L ′ is used after the estimated value L ′ is obtained by the method described later.

An acceleration sensor 5 is provided at a predetermined position of the vehicle and detects an acceleration in the front-rear direction and outputs a detection voltage proportional to the acceleration. Reference numeral 6 denotes the detection voltage of the acceleration sensor 5 at a predetermined sampling frequency A / The A / D converter D-converts and outputs acceleration data DA. After the microcomputer 4B starts from O ₀ , the vehicle speed v and the moving distance R
_In parallel with the calculation of _SE , the acceleration indicated by the acceleration data DA is time-integrated based on the acceleration data DA and the reference vehicle speed v _{ref is} calculated.
To calculate. Then, after the autonomous navigation is started from O ₀ , when the traveling distance R _SE reaches a predetermined value, the wheel 1 is calculated from the vehicle speed v and the reference vehicle speed v _ref at that time using the following equation.
An estimated value L ′ of the outer circumference length of is calculated and stored in the built-in memory. L ′ = v _ref · (t ₀ / C) ··· (10) Then, in the equation (9), L is obtained by the equation (10).
By substituting ´, the vehicle speed is calculated by autonomous navigation to minimize the error. Hereinafter, the estimation is performed again each time the autonomous navigation is newly started, and L ′ used for the calculation of the equation (9) is updated.

Next, the operation of the above-described embodiment will be described with reference to FIGS. 8 and 9 are flowcharts showing the autonomous navigation processing by the microcomputer 4B, and FIG. 10 is an explanatory diagram of the method of measuring the rotation speed. Note that, first, it is assumed that the vehicle is stopped at a certain point O ₀ , the moving distance R _{SE is} 0, and the reference vehicle speed v _ref = 0 obtained from the acceleration detected by the acceleration sensor 5 is set. . Further, the built-in memory of the microcomputer 4B stores the standard value L ₀ of the outer circumference of the wheel 1 written by the manufacturer before shipment, but the estimated value L ′ of the outer circumference of the wheel 1 is stored. Shall not yet exist.

(1) When the vehicle is stopped When the vehicle is stopped at a certain point O ₀ , the output of the magnetic sensor 7 does not change because the wheel 1 does not rotate, and the output data DM of the A / D converter 8 also has a value. Does not change (Fig. 10
(See (1)). On the other hand, the acceleration sensor 5 outputs a detection voltage corresponding to acceleration = 0, and the A / D converter 6 performs A / D conversion at a sampling cycle T ₀ (sec) to obtain acceleration data DA.
Is output. When new data DA is output from the A / D converter 6 when the microcomputer 4B is in a stopped state, the microcomputer 4B reads the new data DA, and the acceleration indicated by DA is α
As (m / sec ² ), the reference vehicle speed v _ref is calculated by the following equation (steps S20 and S21 in FIG. 8). v _ref ← v _ref + αT ₀ (m / sec) ··· (11)

Then, it is checked whether new magnetic detection data DM is output from the A / D converter 8 (step S2).
2) If NO, the process returns to step S20, and if YES, it is stored in the built-in memory (step S23). The latest magnetic detection data DM can be stored for at least t ₀ hours in the built-in memory.
Write M to internal memory. Subsequently, it is checked whether or not new magnetic detection data DM for the time t ₀ , for which the number of peak occurrences has not been measured yet, is accumulated in the built-in memory (step S24), and if NO, the process returns to step S20. While the vehicle is stopped, the acceleration indicated by the acceleration data DA output from the A / D converter 6 is all 0, so v _ref remains 0.

When the magnetic detection data DM for the unit time t ₀ for which the number of peak occurrences has not been measured is accumulated in the built-in memory, YES is determined in step S24, and the magnetic detection data DM for the t ₀ is stored. Based on this, the number C of peak occurrences caused by the temporal change of the magnetic strength during t ₀ is counted (step S25). Here, the wheel 1 is not rotating and t ₀
During that period, C = 0 because the magnetic strength is constant. continue,
It is checked whether the peak occurrence frequency C during this time t ₀ is other than 0, and since it is NO, the process returns to step S20 (step S20).
No in 26). After that, the microcomputer 4B makes t ₀
The number of peak occurrences C caused by the temporal change in the magnetic strength during t ₀ is counted every time the magnetic detection data DM for the latest t ₀ is elapsed, but it is 0 if the vehicle is still stopped.
(Step S25. C = C in FIG. 10A)
_-1 , see C ₀ ).

(2) When the vehicle starts traveling from the point O ₀ after the start of traveling, the acceleration sensor 5 outputs a detection voltage indicating a positive acceleration while the vehicle is accelerating, and the A / D converter 6 Is A / D converted and output. Therefore, v _ref gradually increases from 0 by the processing of steps S20 and S21. Incidentally, the acceleration sensor 5 outputs a detection voltage indicating zero acceleration while the vehicle is traveling at a constant speed, and outputs a detection voltage indicating negative acceleration while the vehicle is decelerating. On the other hand, when the vehicle 1 starts traveling, the wheel 1 rotates at a speed corresponding to the traveling speed, and the magnetic strength detected by the magnetic sensor 7 peaks once every one rotation of the wheel 1. Then, when the result of counting the number of peak occurrences C caused by the temporal change of the magnetic strength during the time t _{0 in} the step S25 by the microcomputer 4B becomes the first count value C = C ₁ indicating a value other than 0 (FIG. 10). (1)
Then, the calculation of the vehicle speed and the movement distance from O ₀ by the autonomous navigation is started (YES in step S26, S27).

Specifically, first, the timer used to determine whether or not the vehicle has stopped is stopped (step S
27), it is checked whether the estimated value L'exists in the built-in memory (step S28), and since it is NO, L ← L ₀ is set (step S29), and the first count value C = C ₁ indicating that the count result is other than 0 Using the following equation, the vehicle speed v is calculated and output to the outside. v ← LC / t ₀ (m / sec) ··· (12) Further, using v obtained by the equation (11), the moving distance R _SE from O ₀ is calculated by the following equation and output to the outside (step S30). R _SE ← R _SE + vt ₀ (m) ··· (13)

Next, it is checked whether new acceleration data DA is output from the A / D converter 6 (step S in FIG. 9).
31), if NO, proceed to step S33, but YES
In this case, in step S32, the reference vehicle speed _vref is calculated by the equation (11) with the acceleration indicated by the current DA as α. Then, the moving distance R _SE from O ₀ is a predetermined threshold value R _C (R _C is a certain fixed value, for example, 1 km,
It is checked whether it exceeds 5 km, 10 km, etc.) for the first time (step S33). Since it is not yet here, it is checked whether new magnetic detection data DM is output from the A / D converter 8 (step S34), If NO, the process returns to step S31, and if YES, it is additionally stored in the built-in memory (step S35). Then, it is checked whether or not new magnetic detection data DM for the time t ₀ for which the number of peak occurrences has not been measured is stored in the built-in memory (step S36). If NO, the process returns to step S31.

[0035] Then, in the internal memory, still determines YES in step S36 the magnetic detection data DM of the new t ₀ hour that has not the measurement of peak occurrences is accumulated, minute magnetic detection data of the t ₀ Based on DM, the number C of peak occurrences caused by the temporal change of the magnetic strength during t ₀ is counted (step S37). Then, the current count value C = C ₂
It is checked whether (see FIG. 10 (1)) is other than 0. If it is not 0, the process returns to step S28 through step S39 in FIG. 8 to check whether the estimated value L ′ exists in the built-in memory. Since it is still NO, set L ← L ₀ (step S2
9), using the current count value C = C ₂ , (12), (1
The vehicle speed v and the moving distance R _SE are calculated by the formula 3) and output to the outside (step S30). Next, it is checked whether new acceleration data DA is output from the A / D converter 6 (step S31). If NO, the process proceeds to step S33, but if YES, step S32 causes the current D
The reference vehicle speed v _ref is calculated from the equation (11), where α is the acceleration indicated by A. After that, the same processing is repeated, and A /
Based on the output of the D converter 8, the vehicle speed v and the moving distance R _SE are calculated using the standard value L ₀ , and the reference vehicle speed v _ref is calculated based on the output of the acceleration sensor 5.

After that, when it is moved from O ₀ by R _C and YES is obtained in step S33, the microcomputer 4B
Calculates the estimated value L'of the outer peripheral length of the wheel 1 using the latest count value C by the following equation and stores it in the built-in memory (step S39). L ′ ← v _ref · (t ₀ / C) (m) ··· (14) This L ′ is closer to the actual length of the outer circumference of the wheel 1 than the standard value L ₀ set by the manufacturer. . After that, the microcomputer 4B checks Y in step S28.
ES is determined, and L ← L ′ is set (step S40),
The vehicle speed v and the moving distance R _SE are calculated by the equations (12) and (13) (step S30). Therefore, it is possible to reduce the calculation error of the vehicle speed v and suppress the increase of the accumulated error of the moving distance R _SE .

After that, when the vehicle decelerates and stops, the rotation of the wheels 1 stops and the output change of the magnetic sensor 7 stops.
At this time, the count value C in step S37 is gradually reduced to finally 0 (C _k-2 , C _k-1 , C of FIG. 10 (2)).
See _k ). Then, the microcomputer 4B determines NO in step S38, checks whether the timer is counting time (step S41), and since it is NO here, starts the timer (step S42).

When the vehicle is once stopped and the traveling is resumed immediately after the time counting operation of the timer is started, step S38
The answer is YES, so after the timer is stopped (step S39), the process proceeds to step S28, but if the count value C remains 0 after that, the next step S
When the answer is NO in 38, the timer is in the time counting operation (YES in step S41), so it is checked whether the timer counting time T _tm exceeds a predetermined threshold value T _C (step S43). T _C is a time sufficient to determine that the vehicle is stopped, and is set to, for example, 1 minute, 5 minutes or the like, and if not yet, the process returns to step S31. And
When the time measured by the timer T _tm exceeds the predetermined threshold value T _C , YES is determined in step S43, v _ref and R _SE are initialized to 0 (step S44), and the process returns to step S20 to wait for the next running. It becomes a state.

When the next running is started, the microcomputer 4B starts the second autonomous navigation from the time when the count value C of the number of peak occurrences per unit time t ₀ becomes _nonzero for the first time, but When the estimated value L ′ of the outer circumference of the wheel 1 is obtained by the autonomous navigation, the vehicle speed v and the moving distance R _SE are calculated from the beginning using the estimated value L ′ (YES in step S28). , S40, S3
0), the calculation with a small error is possible from the beginning.

According to this embodiment, the peak change of the detection voltage of the magnetic sensor 7 caused by the rotation of the wheel 1 is counted every unit time t ₀ to measure the rotation speed, and in parallel therewith, the output of the acceleration sensor 5 installed in the vehicle time integration to calculate the reference vehicle speed v _ref, estimate the length of the outer circumference of the wheel 1 from the rotational speed of the wheel 1 measured by v _ref and the measurement circuit 3 at a certain timing Then, since the vehicle speed v and the moving distance R _SE are calculated by the autonomous navigation using the estimated value and the rotation speed measured by the measurement circuit 3, a value close to the actual outer circumference of the wheel 1 is used. It is possible to calculate the vehicle speed v and the moving distance R _SE with a small error. Moreover, since the reference vehicle speed is calculated separately from the wheel speed sensor, it is not necessary to use an expensive and complicated device such as a GPS receiver, and the burden on the configuration is small.

Moreover, the magnetic sensor 7 arranged close to the wheel 1 detects the magnetism of the wheel 1 which is naturally magnetized, and the peak of the detection output of the magnetic sensor 1 as the wheel 1 rotates. Since the rotation speed of the wheel 1 is detected by measuring the number of occurrences per unit time, a relatively simple configuration is sufficient.

In the above embodiment, the acceleration detected by the acceleration sensor 5 is integrated over time to obtain the reference vehicle speed v.
_{Although the ref} is calculated, the estimated value L ′ of the outer peripheral length of the wheel 1 is calculated from the reference vehicle speed v _ref and the rotation speed of the wheel 1 detected from the peak change of the detected voltage of the magnetic sensor 7. , The acceleration detected by the acceleration sensor 5 is integrated over time to calculate the reference movement distance, and the ratio to the movement distance obtained by the autonomous navigation using the convenient outer peripheral length L of the wheel 1 is calculated as the convenient movement. The estimated value L ′ of the outer peripheral length of the wheel 1 may be calculated by multiplying the outer peripheral length L of the wheel 1.

Specifically, the flowcharts of FIGS. 8 and 9 are modified as shown in FIGS. 11 and 12, and steps S21 'and S32' corresponding to steps S21 and S32 of FIGS. 8 and 9 are performed.
Then, in addition to calculating the reference vehicle speed v _ref by the formula (11), the reference moving distance R from the autonomous navigation start point is calculated according to the following formula.
Calculate _ref . R _ref ← R _ref + v _ref · T ₀ ··· (15) However, the reference moving distance R _ref is initialized to 0 at the time of starting the flowchart of FIG. 11 and at step S44 ′ corresponding to step S44 of FIG. To be done.

Then, when the vehicle moves by R _C from the autonomous navigation start point and becomes YES in step S33, the estimated value L'of the outer circumference of the wheel 1 is calculated by the following equation (FIG. 12).
Step S39 '). L '← L- (R _ref / R _SE )-(16) For L in the above formula, L ₀ set by the manufacturer before shipment immediately after the start of the first autonomous navigation is conveniently used. (NO in step S28, step S29). If the estimated value L ′ has already been obtained last time, the previously obtained L ′ is used for convenience (YES in step S28, S4).
0). 11 and 12, it is possible to calculate the vehicle speed v and the moving distance R _SE with a small error by using a value close to the actual outer circumference of the wheel 1, and a system separate from the wheel speed sensor. Therefore, it is not necessary to use an expensive and complicated device such as a GPS receiver to calculate the reference vehicle speed, and the burden on the configuration is small.

Further, in step S30 of FIG.
Instead of calculating the moving distance R _SE by the equation (13), the cumulative rotational speed RT _SE of the wheel 1 from the autonomous navigation start point O ₀ is calculated by the following equation.
To calculate. RT _SE ← RT _SE + C (times) ··· (13) ′ Then, in step S33, RT _SE is a certain threshold value R.
It is checked whether T _C (RT _C is, for example, a value corresponding to traveling of about 1 km, 5 km, or 10 km) is exceeded, and in step S39 ′, the estimated value L ′ is calculated by the equation (16).
Instead of calculating, the following formula may be used. L '← R _ref / RT _SE ··· (16) ′ In this case, RT _SE is set to 0 instead of R _SE at the time of starting the process of FIG. 11 for the first time.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 13 is a block diagram showing the configuration of the vehicle speed detection system of the vehicle-mounted navigation device according to the present invention, and the same components as those in FIG. 1 are designated by the same reference numerals. Reference numeral 1 is a wheel, and 2 is a rotation pulse generator for generating n pulses per rotation of the wheel (where n is an integer of 1 or more). Reference numeral 5 denotes an acceleration sensor which is provided at a predetermined location of the vehicle, detects acceleration in the front-rear direction, and outputs a detection voltage proportional to the acceleration, and 6 A / D-converts the detection voltage of the acceleration sensor 5 at a predetermined sampling frequency. , Acceleration data DA
Is an A / D converter that outputs 4C is a microcomputer, in autonomous navigation, and calculates a reference distance traveled by integrating the acceleration indicated by the acceleration data DA time R _{re f} (m). Then, in parallel with the calculation of the reference movement distance R _ref , the output pulse of the rotation pulse generator 2 is input to measure the period ΔT (sec) between the pulses, and the reference movement distance R _ref during the period ΔT The vehicle speed v is calculated by dividing the change by ΔT.

Next, the operation of the above-described embodiment will be described with reference to FIG. FIG. 14 shows a microcomputer 4
It is a flowchart which shows the autonomous navigation process by C. At first, it is assumed that the vehicle is stopped at a certain point O ₀ , and the reference vehicle speed v _ref = 0 and the reference movement distance R _ref = 0 obtained from the acceleration detected by the acceleration sensor 5. To do.

(1) When the vehicle is stopped When the vehicle is stopped at a certain point O ₀ , the rotation pulse generator 2 does not output a pulse because the wheel 1 does not rotate. On the other hand, while the vehicle is stopped, the acceleration sensor 5 outputs a detection voltage corresponding to acceleration = 0, and the A / D converter 6 performs A / D conversion at the sampling cycle T ₀ (sec) and outputs acceleration data DA. When new data DA is output from the A / D converter 6 while the microcomputer 4C is stopped, the microcomputer 4C reads the new data DA, and D
Acceleration indicated by A as α (m / sec ^2), the reference vehicle speed v _{re f} and the reference travel distance R _ref is calculated by the following equation (14
Steps S50 and S51). v _ref ← v _ref + αT ₀ (m / sec) ··· (17) R _ref ← R _ref + v _ref · T ₀ (m) ··· (18)

Then, it is checked whether or not the first pulse is input from the rotation pulse generator 2 (step S52), and since it is NO while the vehicle is stopped, the process returns to step S50 and the same processing is repeated. While the vehicle is stopped, the acceleration indicated by the acceleration data DA output from the A / D converter 6 is all 0, so v
_ref and R _ref remain 0.

(2) When the vehicle starts traveling from the point O ₀ after the start of traveling, the acceleration sensor 5 outputs a detection voltage indicating a positive acceleration while the vehicle is accelerating, and the A / D converter 6 Is A / D converted and output. Thus, the process of step S50, S51, v _ref, the R _{re f} gradually increases from zero. By the way,
The acceleration sensor 5 outputs a detection voltage indicating zero acceleration while the vehicle is traveling at a constant speed, and while the vehicle is decelerating,
It outputs a detection voltage that indicates negative acceleration. On the other hand, when the vehicle 1 starts traveling, the wheel 1 rotates at a speed corresponding to the traveling speed, and the rotation pulse generator 2 generates n pulses while the wheel 1 makes one rotation. When the first pulse is input, the microcomputer 4C starts calculating the vehicle speed by autonomous navigation (YES in step S52, S53).

Specifically, first, the first timer for measuring the period ΔT between pulses is started, and at the same time, the second timer used for determining whether or not the vehicle is stopped is stopped to update the latest timer. The obtained reference movement distance R _ref is registered as R ₁ (step S53). Next, it is checked whether new acceleration data DA is output from the A / D converter 6 (step S54). If NO, the process proceeds to step S56, but if YES, step S55 indicates the current DA. The reference vehicle speed v _ref and the reference movement distance R _ref are calculated by the equations (17) and (18) with the acceleration α. Then, it is checked whether the next pulse is input from the rotation pulse generator 2 (step S56). If not, check whether the second timer is counting (step S5).
7) Since it is NO here, the second timer is started (step S58). Then, returning to step S54,
It is checked whether new acceleration data DA is output from the A / D converter 6, and if NO, the process proceeds to step S56.
If YES, the process proceeds to step S55 and the reference vehicle speed v
After calculating _ref and reference movement distance R _ref , step S5
Go to 6.

If the judgment in step S56 is still NO, the second timer is currently counting (step S5).
It is checked whether the time t _{2 of the} timer exceeds a predetermined threshold value T _C (step S5).
9). T _C is a time sufficient to determine that the vehicle is stopped, and is set to, for example, 1 minute, 5 minutes, etc., and is NO during traveling, returns to step S54, and repeats similar processing. .

[0053] Thereafter, when a new pulse from the rotary pulse generator 2 is input, the microcomputer 4C determines YES in step S56, the period between the count time t ₁ of the current first timer first pulse ΔT In addition, the vehicle speed v is calculated by the following equation using the difference between the current reference movement distance R _ref and R ₁ as the movement distance ΔR during the first period ΔT, and output to the outside (step S59). v ← ΔR / ΔT (m / sec) ··· (19)

Thereafter, the first timer is restarted to newly start time counting from 0, the second timer is stopped, and the current R _ref is registered as R ₁ (step S60). Then, returning to step S54,
Until the next pulse is input from the rotation pulse generator 2,
The microcomputer 4C continues to calculate the reference vehicle speed v _ref and the reference movement distance R _ref based on the output of the acceleration sensor 5 (step S55), and at the time when the next pulse is input,
The time t ₁ of the first timer is set to the period Δ between the second pulses.
T and the difference between the reference movement distance R _ref and R ₁ as the movement distance ΔR during the second period ΔT, the vehicle speed v is calculated by the equation (19) and output to the outside (steps S56 and S5).
9). Thereafter, by repeating the same processing, the microcomputer 4C can calculate and output a vehicle speed without error from the pulse output from the rotation pulse generator 2 without knowing the size of the wheel 1. .

After that, when the vehicle decelerates and stops, the rotation of the wheels 1 stops and the pulse output from the rotation pulse generator 2 stops. Then, since the second timer is not stopped in step S60, if the time t ₂ of the second timer exceeds T _C at a certain timing, the microcomputer 4C
Determines YES in step S59, initializes v _ref and R _ref to 0, returns to step S50, and enters a standby state for the next run (step S61).

According to this embodiment, the microcomputer 4C controls the rotation pulse generator 2 according to the rotation of the wheel 1.
While measuring the period ΔT of the pulse emitted from
ΔT by integrating the acceleration detected by the acceleration sensor 5 with time
A moving distance [Delta] R calculated between. Thus to calculate the vehicle speed by the calculation of [Delta] R / delta T, even without knowing the size of the wheel 1, it is possible to calculate the low speed of the error, moreover, moving There is no need to use expensive and complicated devices such as a GPS receiver to calculate the distance, and the configuration load is small.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 15 is a block diagram showing the configuration of the vehicle speed detection system of the vehicle-mounted navigation device according to the present invention. The same components as those in FIG. 7 are designated by the same reference numerals. Reference numeral 1 is a wheel, and 7 is a magnetic sensor as a rotation signal generating means, which detects the magnetism naturally magnetized in the wheel and outputs a detection voltage having a magnitude proportional to the strength of the magnetism. Reference numeral 8 denotes an A / D converter that A / D-converts the detection voltage of the magnetic sensor 7 as a rotation signal at a predetermined sampling period and outputs the magnetic detection data DM.

Reference numeral 5 denotes an acceleration sensor which is provided at a predetermined position of the vehicle and detects acceleration in the front-rear direction and outputs a detection voltage proportional to the acceleration. Reference numeral 6 denotes the detection voltage of the acceleration sensor 5 at a predetermined sampling frequency A / The A / D converter D-converts and outputs acceleration data DA. Reference numeral 4D is a microcomputer, which calculates a reference movement distance R _ref (m) by time-integrating the acceleration indicated by the acceleration data DA based on the acceleration data DA during autonomous navigation. Then, in parallel with the calculation of the reference moving distance R _ref , the magnetic detection data DM output from the A / D converter 8 is read and the latest fixed amount of data is left in an internal memory (not shown). It is stored, and it is determined whether or not a new peak has occurred by using the stored latest series of magnetic detection data DM as a target, and a period ΔT (se
c) is measured, and the vehicle speed v is calculated by dividing the change amount ΔR of the reference movement distance R _ref during the period ΔT by ΔT.

Next, the operation of the above-described embodiment will be described with reference to FIGS. 16 and 17 are flowcharts showing the autonomous navigation processing by the microcomputer 4D. Initially, the vehicle is in a stopped state at a certain point O ₀ , the reference vehicle speed v _ref = 0 obtained from the acceleration detected by the acceleration sensor 5, and the reference movement distance R _ref.
= 0.

(1) When the vehicle is stopped When the vehicle is stopped at a certain point O ₀ , the output of the magnetic sensor 7 does not change because the wheel 1 does not rotate, and the output data DM of the A / D converter 8 also has a value. Does not change. On the other hand, while the vehicle is stopped, the acceleration sensor 5 outputs a detection voltage according to acceleration = 0, and the A / D converter 6 outputs the sampling cycle T ₀ (se
A / D conversion is performed in c) and acceleration data DA is output. When the microcomputer 4D is stopped,
When new data DA is output from the A / D converter 6, it is read and the acceleration indicated by DA is α (m / sec ² )
Then, the reference vehicle speed v _ref and the reference movement distance R _ref are calculated by the following equations (steps S70 and S71 in FIG. 16). v _ref ← v _ref + αT ₀ (m / sec) ··· (20) R _ref ← R _ref + v _ref · T ₀ (m) ··· (21)

Then, it is checked whether new magnetic detection data DM is output from the A / D converter 8 (step S7).
2) If NO, the process returns to step S70, and if YES, it is stored in the built-in memory (step S73). The latest magnetic detection data DM can be stored in the built-in memory for at least t ₀ hours, and the magnetic detection data DM is written in the built-in memory so that new data is left in time. Then, it is determined whether or not a peak has occurred for the latest series of magnetic detection data DM stored in the built-in memory (step S74). When the vehicle is stopped, the determination is NO. At this time, the process returns to step S70, and the same processing is repeated thereafter.

(2) When the vehicle starts traveling from the point O ₀ after the start of traveling, the acceleration sensor 5 outputs a detection voltage indicating a positive acceleration while the vehicle is accelerating, and the A / D converter 6 Is A / D converted and output. Thus, the process of step S70, S71, v _ref, the R _{re f} gradually increases from zero. On the other hand, when the vehicle 1 starts traveling, the wheel 1 rotates at a speed corresponding to the traveling speed, and the magnetic sensor 7 rotates once every time the wheel 1 makes one rotation.
A peak appears in the magnetic strength detected by. When the first peak occurs, the microcomputer 4D executes step S7.
When it is determined in step 4 whether or not a peak has occurred by using the latest series of magnetic detection data DM stored in the built-in memory, YE
After S, the calculation of the vehicle speed by the autonomous navigation and the moving distance from O ₀ is started (step S75).

Specifically, first, the first timer for measuring the period ΔT between pulses is started, and at the same time, the second timer used for determining whether or not the vehicle is stopped is stopped to update the latest timer. The obtained reference movement distance R _ref is registered as R ₁ (step S75). Next, it is checked whether new acceleration data DA is output from the A / D converter 6 (step S76 in FIG. 17). If NO, the process proceeds to step S78, but if YES, the process proceeds to step S77. Let the acceleration indicated by DA be α, (20), (2
The reference vehicle speed v _ref and the reference movement distance R _ref are calculated by the equation 1). Then, it is checked whether new magnetic detection data DM is output from the A / D converter 8 (step S7).
8), if NO, the process returns to step S76, and if YES, it is stored in the built-in memory (step S79). Also here, the magnetic detection data DM is written in the built-in memory by leaving new data more temporally. Then, it is determined whether or not the next new peak has occurred by targeting the latest series of magnetic detection data DM stored in the built-in memory (step S80).

If not, it is checked whether or not the second timer is counting (step S81), and since it is NO here, the second timer is started (step S82). Then, the process returns to step S76, and it is checked whether new acceleration data DA is output from the A / D converter 6. If NO, the process proceeds to step S78, and if YES, the process proceeds to step S77 and the reference vehicle speed v _ref , After calculating the reference movement distance R _ref , the process proceeds to step S78. A / D in step S78
It is checked whether new magnetic detection data DM is output from the converter 8. If NO, the process returns to step S76, and YE
If S, it is stored in the built-in memory (step S79).
Then, it is determined whether or not the next new peak has occurred by targeting the latest series of magnetic detection data DM stored in the built-in memory (step S80).

If the judgment in step S80 is still NO, the second timer is currently counting (step S8).
It is checked whether the time t ₂ of the second timer exceeds a predetermined threshold value T _C (step S8).
3). T _C is a time sufficient to determine that the vehicle is stopped, and is set to, for example, 1 minute, 5 minutes, etc., becomes NO during traveling, returns to step S76, and repeats similar processing. .

After that, when a second peak is generated in the magnetic intensity detected by the magnetic sensor 7, the microcomputer 4D newly targets the latest series of magnetic detection data DM stored in the built-in memory in step S80. When it is determined whether or not the peak has occurred, YES is determined. At this time, the microcomputer 4D causes the current time t ₁ of the first timer to be counted.
Is the cycle ΔT between the first peaks, and the difference between the current reference travel distance R _ref and R ₁ is the travel distance ΔR between the first cycles ΔT, and the vehicle speed v is calculated by the following equation and output to the outside. Yes (step S84). v ← ΔR / ΔT (m / sec) ··· (22)

Thereafter, the first timer is restarted to newly start time counting from 0, the second timer is stopped, and the current R _ref is registered as R ₁ (step S85). Then, returning to step S76,
The microcomputer 4D continues to calculate the reference vehicle speed v _ref and the reference movement distance R _ref based on the output of the acceleration sensor 5 until the next peak appears in the magnetic intensity detected by the magnetic sensor 7 (step S77), and When the peak occurs, the time t ₁ of the first timer is set as the cycle ΔT between the second peaks, and the difference between the reference moving distance R _ref and R ₁ is set as the moving distance ΔR during the second cycle ΔT. , (22) is used to calculate the vehicle speed v and output it to the outside (step S80,
S84). After that, by repeating the same processing, the microcomputer 4D does not know the size of the wheel 1,
From the detection output of the magnetic sensor 7, a vehicle speed without error can be calculated and output.

After that, when the vehicle decelerates and stops, the rotation of the wheel 1 stops, the output change of the magnetic sensor 7 stops,
The peak does not occur. Then the second timer goes to step S
Since it will not be stopped at 85, the time t of the second timer
Where ₂ exceeds T _C , microcomputer 4D
Determines YES in step S83, initializes v _ref and R _ref to 0, returns to step S70, and enters a standby state for the next run (step S86).

According to this embodiment, the microcomputer 4D measures the cycle ΔT of the peak generated in the detection output of the magnetic sensor 7 according to the rotation of the wheel 1 and integrates the acceleration detected by the acceleration sensor 5 with respect to time. Since the moving distance ΔR between ΔT is calculated and the vehicle speed is calculated by calculating ΔR / ΔR, the vehicle speed with a small error can be calculated without knowing the size of the wheel 1. Therefore, it is not necessary to use an expensive and complicated device such as a GPS receiver for calculating the moving distance, and the burden on the configuration is small. It should be noted that the wheel 1 has n pieces per rotation (where n is an integer of 2 or more) in advance depending on the magnetic strength detected by the magnetic sensor 7.
Even if magnetized so that the peak of
The vehicle speed with a small error can be calculated in exactly the same manner as in the case of.

[0070]

According to the present invention, a vehicle speed with a small error can be calculated by autonomous navigation, and an expensive and complicated device such as a GPS receiver is used to calculate the reference vehicle speed and the reference moving distance. There is no need to do it, and the burden on the configuration is small.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a vehicle speed detection system of a vehicle-mounted navigation device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

3 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

FIG. 4 is an explanatory diagram illustrating a method of measuring a rotation speed according to the first embodiment.

5 is a flowchart showing an autonomous navigation process by a microcomputer according to a modification of FIG.

FIG. 6 is a flowchart showing an autonomous navigation process by a microcomputer according to a modification of FIG.

FIG. 7 is a block diagram showing a configuration of a vehicle speed detection system of a vehicle-mounted navigation device according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

9 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

FIG. 10 is an explanatory diagram illustrating a rotation speed measurement method according to the second embodiment.

11 is a flowchart showing an autonomous navigation process by the microcomputer according to the modification of FIG.

FIG. 12 is a flowchart showing an autonomous navigation process by the microcomputer according to the modified example of FIG.

FIG. 13 is a block diagram showing a configuration of a vehicle speed detection system of a vehicle-mounted navigation device according to a third embodiment of the present invention.

FIG. 14 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

FIG. 15 is a block diagram showing a configuration of a vehicle speed detection system of a vehicle-mounted navigation device according to a fourth embodiment of the present invention.

16 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

FIG. 17 is a flowchart showing an autonomous navigation process by the microcomputer in FIG.

FIG. 18 is a diagram showing how the magnetic intensity detected by a magnetic sensor changes during traveling.

FIG. 19 is a block diagram showing a configuration of a vehicle speed detection system of a conventional vehicle-mounted navigation device.

[Explanation of symbols]

1 Wheel 2 Rotational Pulse Generator 3 Measuring Circuit 4A, 4B, 4
C, 4D microcomputer
5 Acceleration sensor 7 Magnetic sensor

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01P 3/42 G01P 3/50 G01P 7/00 G01B 21/02 G01C 21/16

Claims (2)

(57) [Claims] 1. A rotational speed detecting means for detecting a rotational speed of a wheel, an acceleration detecting means for detecting an acceleration of a vehicle, and a reference vehicle speed calculated by using the acceleration detected by the acceleration detecting means. Using the estimation means for estimating the outer circumference of the wheel from the rotation speed detected by the rotation speed detection means, and the rotation speed detected by the rotation speed detection means and the outer circumference length of the wheel estimated by the estimation means A vehicle speed detecting device comprising: a vehicle speed calculating means for calculating a vehicle speed. 2. The rotation speed detection means is provided near a wheel, detects the magnetism of the wheel in a non-contact manner, and measures the cycle of change in the detection output of the magnetism detection means to rotate the wheel. The vehicle speed detecting device according to claim 1, further comprising: a measuring unit that obtains a speed.