JP4085463B2 - Speed measuring method and speed measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a speed measuring device and a speed measuring method applied to speed measurement of a moving body, for example, an automobile.
[0002]
[Prior art]
Conventionally, as a device for measuring the speed of a moving body, for example, there is a speed measurement speed for measuring the speed of the moving body using an acceleration sensor. In this speed measuring device, an acceleration sensor is provided on the moving body, and the moving speed of the moving body is measured by taking a moving time over the acceleration that is the output of the acceleration sensor.
[0003]
In addition, there are measurement devices using a global positioning system (hereinafter referred to as GPS) that receives satellite radio waves from satellites and obtains information on the direction, position, and speed of a moving object, and a measurement device that combines the GPS and the acceleration sensor. It was.
[0004]
[Problems to be solved by the invention]
In a conventional speed measurement device using an acceleration sensor, there are many error factors such as disturbances such as vibration and temperature change, and the influence of gravitational acceleration due to tilt, and it is difficult to calculate the speed using only the acceleration sensor.
[0005]
Further, although the speed can be calculated based on GPS information, the speed cannot be calculated at low speed or when the GPS cannot be received, and the apparatus cannot be realized.
[0006]
Furthermore, even in a speed measurement device combining an acceleration sensor and GPS, an inclination is always used to interpolate GPS (an inclination due to the installation method of the apparatus, an inclination of a moving body on which the apparatus is mounted, an inclination of a road surface on which the moving body travels, etc. ), It is necessary to calculate the influence of gravitational acceleration, and sensors that can detect the inclination of angle sensors, angular velocity sensors, etc. have a problem that errors increase due to disturbances such as drift and vibration due to temperature changes. .
[0007]
The present invention has been made in view of the above points. The purpose of the present invention is to use GPS information and cancel the influence of gravitational acceleration even when GPS information is unavailable. An object of the present invention is to provide a speed measuring method and a speed measuring apparatus that can measure.
[0008]
[Means for Solving the Problems]
(1) The speed measurement method of the present invention is the speed measurement method for measuring the speed of the moving body using an acceleration sensor and a GPS receiver provided on the moving body.The reception status of the GPS receiver is good, and the speed obtained from the GPS receiver information is equal to or higher than the lower reliability limit X [km / h].When the first condition is satisfied, the gravitational acceleration component due to the inclination of the moving body is corrected using GPS speed information, and when the first condition is not satisfied, an angular velocity sensor that detects the inclination change of the moving body is corrected. Correct the gravitational acceleration component due to the inclination of the moving body using the detection output,The reception status of the GPS receiver is goodWhen satisfying the second condition, the speed based on the speed information obtained by the GPS receiver as a speed measurement value,The secondWhen the condition is not satisfied, a speed measured based on the output value of the acceleration sensor is used as a speed measurement value.age,
Also,In a speed measurement method for measuring the speed of the moving body using an acceleration sensor and a GPS receiver provided on the moving body, the reception status of the GPS receiver is good and the speed obtained from information of the GPS receiver Is equal to or more than the reliability lower limit X [km / h], the acceleration sensor offset is corrected for the gravitational acceleration component due to the inclination of the moving body using GPS speed information, and the speed of the moving body is corrected. When the above condition is not satisfied, the acceleration sensor offset is corrected for the gravitational acceleration component due to the tilt of the moving body using the detection output of the sensor that detects the tilt change, and the speed of the moving body is calculated. It is characterized by
  The correction of the offset of the acceleration sensor using the GPS receiver is performed based on average values of the speed information measured by the GPS receiver and the acceleration information measured by the acceleration sensor. .
[0009]
(2) The speed measuring device of the present invention is a speed measuring device that measures the speed of the moving body using an acceleration sensor and a GPS receiver provided on the moving body.The reception status of the GPS receiver is good, and the speed obtained from the GPS receiver information is equal to or higher than the lower reliability limit X [km / h].First correction means for calculating an offset obtained by correcting a gravitational acceleration component due to an inclination of the acceleration sensor based on speed information obtained by the acceleration sensor and the GPS receiver when the first condition is satisfied; Second correction means for calculating an offset obtained by correcting the gravitational acceleration component due to the inclination of the acceleration sensor based on information obtained by the angular velocity sensor for detecting a change in inclination when the condition is not satisfied;The reception status of the GPS receiver is goodWhen the second condition is satisfied, the speed is calculated using the acceleration sensor offset calculated by the first correction means, and when the GPS receiver speed information does not satisfy the second condition, And a speed calculating means for calculating a speed using the offset of the acceleration sensor calculated by the second correcting means.age,
SaidThe correction of the offset of the acceleration sensor using the GPS receiver is performed based on the respective average values of the speed information measured by the GPS receiver and the acceleration information measured by the acceleration sensor.
[0010]
(3) In the speed measuring method and speed measuring device of the present invention, the offset of the acceleration sensor isGPS receiverWhether or not can be used, the gravitational acceleration component due to the inclination of the apparatus installation method, the inclination of the moving body on which the apparatus is mounted, the inclination of the road surface along which the moving body travels, etc. is corrected. For this reason, a highly accurate speed can always be measured.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram when a speed measuring device 10 is connected to a navigation system 19 as a basic configuration example of an embodiment of the present invention.
[0012]
In FIG. 1, a speed measuring device 10 includes a GPS antenna 11, a well-known GPS receiver 12 for decoding a signal received from the GPS antenna 11, and an acceleration sensor for measuring the acceleration of a moving body by a capacitance method. 13, an angular velocity sensor 14 for detecting an angular velocity of a tilt change in the traveling direction of the moving body, an A / D converter 15 for converting the acceleration value and the angular velocity value of the analog output from the acceleration sensor 13 and the angular velocity sensor 14 into digital values, and An arithmetic processing unit 16 comprising a microprocessor unit that calculates information from the GPS receiver 12 and digital acceleration values from the acceleration sensor 13 and the angular velocity sensor 14, an offset of the acceleration sensor based on the angular velocity value, and the arithmetic processing unit The information from the GPS receiver 12 and the acceleration sensor 13 and the memory 17 for temporarily storing the digital acceleration value and angular velocity value data from the angular velocity sensor 14, and for outputting the velocity data and position data calculated by the calculation processing unit 16 to the external navigation system 19. And a communication unit 18 that performs an interface.
[0013]
Here, the GPS receiver 12 receives four GPS radio waves Wa, Wb, Wc, Wd from the satellite by the connected antenna 11, and information on longitude, latitude, altitude absolute coordinates and time of the reception position, and the ground It is configured to output absolute speed information. The acceleration sensor 13 measures acceleration using the relationship of acceleration = force / mass, and as a transducer for measuring force, for example, a displacement of mass supported by a leaf spring is accumulated in a capacitor. A capacitance method that measures the change in capacitance is used.
[0014]
The navigation system 19 displays the current position of the moving body on the map data based on the speed data and GPS data of the moving body supplied from the speed measuring device 10, and displays the longitude, latitude, altitude, date and time, GPS data such as heading to the ground, distance, estimated arrival time, estimated arrival time, etc. is displayed.
[0015]
The arithmetic processing unit 16 uses the absolute velocity information from the GPS receiver 12 to calculate an appropriate offset of the acceleration sensor 13 while taking into account the output values of the acceleration sensor 13 and the angular velocity sensor 14, and the offset. Is used to calculate the speed of the moving object.
[0016]
For example, even if the output value of the acceleration sensor becomes large due to the influence of gravitational acceleration when the moving body moves uphill, an appropriate offset is calculated by using absolute speed information from the GPS receiver 12 can do. Similarly, offset fluctuation due to temperature change can also be calculated.
[0017]
Note that the function of the arithmetic processing unit 16 may be performed by an arithmetic processing unit in the navigation system 19. The speed measuring device 10 may be taken into the navigation system 19.
[0018]
FIG. 2 shows the movement directions detected by the acceleration sensor 13 and the angular velocity sensor 14 mounted on the speed measuring device 10. The acceleration sensor 13 detects the acceleration of the moving body 20 in the traveling direction (22). The angular velocity sensor 14 detects the angular velocity of the inclination change (21) in the traveling direction of the moving body 20.
[0019]
In the present invention, when calculating the moving speed of the moving body, the speed is calculated mainly using information from GPS, and when the GPS information cannot be obtained or the speed accuracy obtained from the GPS information cannot be obtained. Then, the speed is calculated using the acceleration sensor information. At this time, the offset of the acceleration sensor is an appropriate value taking the gravitational acceleration into consideration, and needs to be sequentially calculated according to the road surface where the moving body is traveling.
[0020]
In the following, an offset calculation method for an acceleration sensor taking gravity acceleration into consideration will be described.
[0021]
  [When GPS information is available: Speed calculation method using GPS information]
  First, FIG. 3 shows the state of the moving body on the slope of this embodiment. In FIG. 3, when the moving body 20 moves on a slope 23 that is inclined by an angle θ [rad] with respect to the horizontal plane, in addition to the upward acceleration of the slope 23 caused by the movement of the moving body 20, the slope caused by the gravitational acceleration g. 23, a downward gravitational acceleration component g * sin θ is generated. Thus, when the moving body 20 moves on the slope 23 inclined by θ with respect to the horizontal plane, the acceleration of the moving body 20 and the moving body out of the acceleration applied to the acceleration sensor 13.20It is necessary to separate the gravitational acceleration component due to the inclination θ as an offset.
[0022]
In order to calculate the velocity v of the moving body in the arithmetic processing unit 16 based on the output from the acceleration sensor 13, it is calculated by the following equation (1).
[0023]
  v = as * t (1)
  Where v [m / s] is the velocity, as [m / s²] Is the gravitational acceleration component g * sinθ [m / s ² ], And t [s] is time.
[0024]
Further, the acceleration as excluding the gravitational acceleration component g * sin θ is calculated by the following equation (2).
[0025]
  as = As−g * sin θ = (Vout−Voffset) / S * g (2)
  Here, Vout is the output [mV] of the acceleration sensor, Voffset is the offset [mV] of the acceleration sensor considering the gravitational acceleration component, S is the sensitivity [mV / G] of the acceleration sensor, and g is the gravitational acceleration per 1 G [m. / S²], As is the acceleration including the gravitational acceleration component [m / s²] And θ are inclination angles [rad]. stillaccelerationThe offset Voffset of the sensor is a value that changes according to the road surface condition.
[0026]
For example, when the moving body moves up the slope, the offset Voffset increases by the gravitational acceleration component, and when the moving body moves down the slope, the offset Voffset decreases by the gravitational acceleration component.
[0027]
Here, the acceleration as calculated by the acceleration sensor 13 is the acceleration ag [m / s calculated from the speed information of the GPS receiver 12.²], The following equation (3) holds.
[0028]
as = ag (3)
The following equation (4) is obtained from the equations (2) and (3).
[0029]
ag = (Vout−Voffset) / S * g (4)
Therefore, the following equation (5) is obtained from equation (4).
[0030]
Voffset = Vout−ag * S / g (5)
Further, the speed vg [m / s] from the GPS receiver 12 is obtained from the acceleration ag from the GPS receiver 12 by the following equation (6).
[0031]
vg = ag * t (6)
Therefore, the following equation (7) is obtained from equations (5) and (6).
[0032]
Voffset = Vout−vg * S / g / t (7)
In this manner, the acceleration of the moving body 20 and the velocity of the gravitational acceleration component due to the inclination θ of the moving body 20 can be separated from the equation (7) as the offset Voffset.
[0033]
Further, since the offsets shown in the equations (5) and (7) have an error in the range of several percent in the speed and acceleration obtained from the GPS data, they are averaged in the arithmetic processing unit 16 for several seconds and the following (8) By obtaining the equations (9) and (9), the speed measurement accuracy and stability can be further improved. Further, when the GPS receiver 12 has good reception status of GPS data from the satellite, the acceleration ag data from the GPS receiver 12 is taken in.
[0034]
  “Voffset” = “Vout” − “ag” * S / g (8)
  “Voffset” = “Vout” − “vg” * S / g / t (9)
  However, S and g are constant, “Voffset” is an average value of the offset Voffset of the acceleration sensor at a certain time, “Vout” is an average value of the output Vout of the acceleration sensor at a certain time, and “vg” is a certain time. This is the average value of the speed vg from the GPS receiver 12.“Ag” is an average value of acceleration ag from the GPS receiver 12 at a certain time (“vg” = “ag” × t).
[0035]
As described above, the theoretical velocity offset of the acceleration sensor can be obtained from the equations (5) and (7), but the average value of the offset of the acceleration sensor at a certain time from the equations (8) and (9). By using “Voffset”, the influence of noise and the like is reduced, and a good speed measurement value with less error can be obtained. The average value “Voffset” of the acceleration sensor offset thus obtained is sequentially buffered from the data at the time of start-up, and is calculated by substituting sequentially into equations (1) and (2). It is done.
[0036]
[When GPS information is not available]
In FIG. 3, the gravitational acceleration received by the moving body 20 on the slope 23 is θ [rad] as the slope of the slope, and g [m / s as the gravitational acceleration per 1G.²]
g * sin θ [m / s²] ............ (10)
It is.
[0037]
When the acceleration sensor offset taking this gravitational acceleration into consideration is Voffset θ [mV], in FIG. 4 showing the change in gravitational acceleration due to the change in inclination applied to the acceleration sensor, the inclination of the slope 24 is θ1 [rad], θ2 [ rad] are acceleration sensor offsets Voffset θ1 [mV] and Voffset θ2 [mV], respectively.
[0038]
  Here, if the slope 24 changes (moves) from the inclination θ1 to θ2, the gravitational acceleration applied to the acceleration sensor 13 at the inclination θ2 is larger than that at the inclination θ1.
    g * sin θ3 [m / s²] ............ (11)
Only has increased. However, θ3 = θ2−θ1 [rad], Cos θ1≈1, cos θ3≈1.
  Therefore, when the inclination is θ2, the acceleration corresponding to the equation (11) must be subtracted from the measured acceleration. Therefore, the acceleration at the inclination θ2 is
    (Vout−Voffset θ1) / S * g−g * sin θ3 [m / s²] ............ (12)
It can be expressed as Here, Vout represents acceleration sensor output [mV], and S represents acceleration sensor sensitivity [mV / G].
[0039]
When the equation (12) is transformed,
(Vout− (Voffset θ1 + S * sin θ3)) / S * g [m / s²] ............ (13)
Therefore, when the inclination is θ2, the acceleration sensor offset Voffsetθ2 is
Voffset θ2 = Voffset θ1 + S * sin θ3 [mV] (14)
It becomes. Actually, Voffset θ1 is an acceleration sensor initial value (acceleration sensor output at the time of system activation), an acceleration sensor output when the moving body is stopped, an acceleration sensor offset obtained from GPS information and an acceleration sensor output ( [Speed calculation method using the GPS information]). Θ3 is obtained from the angular velocity sensor information.
[0040]
Using the calculated acceleration sensor offset Voffsetθ2, the speed is calculated as follows:
v = a * t = (Vout−Voffset θ2) / S * g * t [m / s]
………… (15)
It becomes. Where v is velocity [m / s], a is acceleration [m / s²] And t are time (seconds) [s].
[0041]
As described above, the offset considering the gravitational acceleration of the acceleration sensor must always be calculated and updated in order to interpolate GPS.
[0042]
In this acceleration sensor offset correction, for example, if the moving body 20 travels on the road 25 from A4 to F4 as shown in FIG. 5A, the corrected acceleration sensor offset graph is shown in FIG. 5B. It becomes like this.
[0043]
That is, the acceleration sensor offset voltage in section A4 to B4 is V1, the acceleration sensor offset voltage in section B4 to C4 is V2, the acceleration sensor offset voltage in section C4 to D4 is V1, and the acceleration sensor offset voltage in section D4 to E4. Is V0, and the acceleration sensor offset voltage in the E4 to F4 interval is V1, respectively.
[0044]
Here, the difference between the acceleration sensor offset voltage V1 when the moving body 20 is traveling in the A4 to B4 section and the acceleration sensor offset voltage V2 when the moving body 20 is traveling in the B4 to C4 section is the difference between the A4 to B4 section and the B4 to B4. This is due to the influence of the gravity acceleration component g * sin θ4 corresponding to the angle difference θ4 with respect to the C4 section.
[0045]
Next, FIG. 6 shows a functional block diagram of the speed measuring apparatus 10. In FIG. 6A, acceleration sensor output data from the acceleration sensor 13 that outputs an analog voltage in accordance with the acceleration applied to the traveling direction (22) of the moving body 20, and the inclination change (21 in the traveling direction of the moving body 20). ), The angular velocity sensor output data from the angular velocity sensor 14 that outputs an analog voltage according to the angular velocity and the velocity information obtained from the information of the GPS receiver 12 are obtained by each data obtaining means 30, and the respective data are stored in the memory means. (Memory) 17 stores temporarily.
[0046]
Using each stored data, the offset of the acceleration sensor taking into account the influence of gravitational acceleration is calculated. When the speed based on the GPS information can be used effectively (case 1), the acceleration sensor offset calculation means 31 using the GPS and the acceleration sensor calculates the acceleration sensor offset taking into account the influence of the gravitational acceleration (the above-mentioned [GPS information Can be used: According to the method described in the section “Speed calculation method using GPS information”).
[0047]
  If the speed based on the GPS information cannot be used effectively (case 2), the acceleration sensor offset calculation means 32 using the angular velocity sensor calculates the acceleration sensor offset taking into account the influence of gravitational acceleration.(According to the method described in the above section [When GPS information is not available]). In the speed calculation means 33, when the speed based on GPS information can be used effectively (case 3), the speed is set as the speed measured by the speed measuring device 10, and when the speed based on GPS information cannot be used effectively (case 4), GPS The speed is calculated using the acceleration sensor offset calculated by the acceleration sensor offset calculating means 31 using the acceleration sensor or the acceleration sensor offset calculating means 32 using the angular velocity sensor, and the speed is set as the speed measured by the speed measuring device 10.
[0048]
In addition, the conditions in the above-described case 1 and case 2 and the conditions in case 3 and case 4 may be different.
[0049]
  For example,
  Case 1: GPS reception is good and the speed obtained from GPS information is10km / hmore than
  Case 2: Case 1 other than 1
  Case 3: Good GPS reception
  Case 4: Case 3 other than
Different conditions may be used.
[0050]
The acceleration sensor offset calculating means 31 using the GPS and the acceleration sensor is configured as shown in FIG. That is, based on the GPS acceleration (speed) average calculating means 34 for calculating the average value based on the speed information from the GPS receiver 12 stored in the storage means 17 and the acceleration sensor output value stored in the storage means 17. The acceleration sensor output average calculating means 35 for calculating the average, and the acceleration sensor offset calculating means 36 for calculating the acceleration sensor offset using the GPS acceleration (speed) average value and the acceleration sensor output average value.
[0051]
For example, the sampling time of each data of the acceleration sensor output value data from the acceleration sensor 13 and the speed information from the GPS receiver 12 in each data acquisition means 30 is t, and the number of data that can be acquired in the period of the sampling time t is x, Svdx is the output value of the acceleration sensor, gvd1, gvd2,... Gvdx is the speed data from the GPS receiver 12, and the average output value of the acceleration sensor in the acceleration sensor output average calculating means 35 is “svd”. “The average value of velocity data from the GPS receiver 12 in the GPS acceleration (speed) average calculating means 34 is“ gvd ”, and the average value of acceleration data from the GPS receiver 12 in the GPS acceleration (speed) average calculating means 34 is“ gad ”. ”, The average output value“ svd ”of the acceleration sensor is expressed by the following equation (16): Velocity data an average value of from PS receiver 12 "GVD" The following equation (17), by the acceleration data mean "gad" the following equation (18) from the GPS receiver 12, are determined, respectively.
[0052]
“Svd” = (svd1 + svd2 +... + Svdx) / x (16)
“Gvd” = (gvd1 + gvd2 +... + Gvdx) / x (17)
“Gad” = (gvdx−gvd1) / t / x (18)
If the acceleration sensor offset in the acceleration sensor offset calculating means 36 is SDoffset, the acceleration sensor offset SDoffset is obtained from the following equation (19) from the equations (8), (16), and (18).
[0053]
SDoffset = “svd” − “gad” * S / g (19)
Further, from the equations (9), (16) and (17), the acceleration sensor offset SDoffset is obtained by the following equation (20).
[0054]
SDoffset = "svd"-"gvd" * S / g / t (20)
Accordingly, the velocity velocity in the velocity calculating means 33 is obtained from the following equation (21) when the output of the acceleration sensor is SDout from the equations (1) and (2).
[0055]
velocity = (SDout−SDoffset) / S * g * t (21)
In this way, it is possible to calculate the speed with high accuracy by sequentially calculating and updating the offset of the acceleration sensor that eliminates the influence of the gravitational acceleration component and the temperature drift from the equation (19) or the equation (20). it can.
[0056]
Next, FIG. 7 shows a flowchart in which the speed measuring device 10 calculates the speed.
[0057]
This flowchart is a case where the conditions of the case 1 and the case 2 are the same as those of the case 3 and the case 4.
[0058]
First, in step S1, the initial values of the acceleration sensor offset and speed are substituted. The acceleration sensor offset initial value is substituted with the output value of the acceleration sensor when the system is started, and the speed is substituted with 0 km / h.
[0059]
Next, in step S2, an acceleration sensor, an angular velocity sensor, and GPS data are captured (stored in the memory 17).
[0060]
In step S3, the reliability of the speed obtained from the GPS information is checked. It is a reliable condition that the GPS is positioned well and the speed obtained from the GPS information is equal to or higher than a certain speed.
[0061]
This is because the speed obtained from the GPS information has a large error at a low speed even if the GPS data is well received.
[0062]
In step S4, if it is determined in step S3 that the speed obtained from the GPS information is reliable, the offset of the acceleration sensor is calculated using the GPS data and the acceleration sensor data (executed according to the flow of FIG. 8 described later). ).
[0063]
Next, in step S5, since it is determined that there is reliability of the speed obtained from the GPS information in step S3, the speed is calculated using GPS data.
[0064]
In step S6, if it is determined in step S3 that the speed obtained from the GPS information is not reliable, it is determined whether the speed measuring device 10 (or the moving body equipped with the speed measuring device 10) is moving or stopped.
[0065]
As a result, in step S7, when it is determined in step S6 that the speed measuring device 10 (or the moving body on which the speed measuring device 10 is mounted) is stopped, the output values of the acceleration sensor and the angular velocity sensor at that time are respectively measured by the acceleration sensor. And update as offset of angular velocity sensor.
[0066]
Next, in step S8, since it is determined in step S6 that the speed measuring device 10 (or the moving body equipped with the speed measuring device 10) is stopped, the speed is set to 0 km / h.
[0067]
In step S9, it is determined that the speed obtained from the GPS information is not reliable in step S3, and in step S6, the speed measuring device 10 (or a mobile body equipped with the speed measuring device 10) is moving. If it is determined, the offset of the acceleration sensor is updated using the angular velocity sensor data.
[0068]
In step S10, it is determined in step S3 that the speed obtained from the GPS information is not reliable, and in step S6, it is determined that the speed measuring device 10 (or a mobile body equipped with the speed measuring device 10) is moving. Therefore, the speed is calculated using the acceleration sensor offset considering the output value of the acceleration sensor and the gravitational acceleration.
[0069]
In step S11, the speed calculated in step S5, step S8, or step S10 is output to the car navigation system 19.
[0070]
FIG. 8 is a flowchart showing an operation when the GPS information is reliable (steps S4 and S5) and the offset is calculated using the acceleration sensor offset calculation means 31 using the GPS and the acceleration sensor of FIG. In FIG. 8, the initial value of the acceleration sensor offset is calculated in step S21. Specifically, the acceleration sensor offset calculation unit 36 of the arithmetic processing unit 16 employs the average value for several seconds from the acceleration sensor output average calculation unit 35 to calculate the initial value of the acceleration sensor offset.
[0071]
In step S22, 0 is assigned to the counter i. Specifically, it becomes the basis of the average value in the acceleration sensor output average calculation means 35 and the GPS acceleration (speed) average calculation means 34 used when the acceleration sensor offset calculation means 36 of the arithmetic processing unit 16 calculates the acceleration sensor offset. Reset the counter that counts the number of data.
[0072]
In step S23, acceleration sensor data and GPS speed data are acquired. Specifically, each data acquisition means 30 acquires acceleration sensor output value data from the acceleration sensor 13 and speed information from the GPS receiver 12 and stores them in the memory 17 as storage means.
[0073]
In step S24, it is determined whether the reception status of the GPS receiver 12 is appropriate and whether it is equal to or higher than the reliability lower limit X [km / h] of the GPS speed data. Specifically, each data acquisition means 30 determines whether to adopt data on the condition of the reception status of GPS reception and the reliability lower limit X of GPS speed data. This is because the error becomes large when the GPS receiver 12 is not receiving GPS data or when the GPS speed data is low, so that it is not used as correction data.
[0074]
If the reception status of the GPS receiver 12 is appropriate in step S24 and is equal to or more than the reliability lower limit X of the GPS speed data, the GPS speed data reliable in the i-th data buffer and the acceleration sensor data at that time are obtained in step S25. Store. Specifically, the acceleration sensor data and the GPS speed data are stored in a counter buffer that counts the number of data that is the basis of the average value in the reliable GPS acceleration (speed) average calculating means 34 and the acceleration sensor output average calculating means 35 at that time. Store.
[0075]
In step S26, the counter i is counted up. Specifically, the counter i is sequentially incremented by the number of stored data. If the reception status of the GPS receiver 12 is appropriate in step S24 and is not greater than or equal to the reliability lower limit X of the GPS speed data, the GPS speed data is not reliable in step S27, and 0 is substituted for the counter i. Specifically, the counter i is reset.
[0076]
In step S28, it is determined whether the counter i is the same value as the number Y of sample data. Specifically, whether the counter i of the acceleration sensor output average calculating means 35 and the GPS acceleration (speed) average calculating means 34 has stored data in the counter i by a preset number of samples Y (data number) or not. to decide. If not stored, the process returns to step S23, and the processes and determinations from step S23 to step S28 are repeated.
[0077]
In step S29, GPS acceleration (speed) average calculation is performed. Specifically, in the GPS acceleration (velocity) average calculation means 34, when data is stored in the counter buffer i for a preset number of times Y (the number of data), based on those data ( The GPS acceleration (speed) average is calculated based on the equation (17) or (18).
[0078]
In step S30, average acceleration sensor output is calculated. Specifically, based on the data stored in the counter buffer i, the acceleration sensor output average calculating means 35 calculates the acceleration sensor output average based on the equation (16).
[0079]
In step S31, acceleration sensor offset calculation is performed. Specifically, based on the GPS acceleration (velocity) average value and acceleration sensor output average value calculated in steps S29 and S30, the acceleration sensor offset calculating means 36 is based on the equation (19) or (20). Acceleration sensor offset is calculated.
[0080]
In step S32, the number of sample data Y-1 is substituted into the counter i. And it returns to step S23 and repeats the process and determination from step S23 to step S32.
[0081]
【The invention's effect】
As described above, according to the present invention, the following excellent effects can be obtained.
(1) It is possible to always measure the speed by using the high-accuracy speed mainly obtained from GPS information and using the speed obtained from the acceleration sensor when the GPS cannot be received. The speed accuracy is higher than that of a measuring device or a speed measuring device using only GPS.
[0082]
(2) Using GPS information and acceleration sensor information, it is possible to calculate the offset of an acceleration sensor that cancels the effects of gravity acceleration and drift due to temperature changes of the acceleration sensor. In addition, the offset of the acceleration sensor in which the influence of the gravitational acceleration is canceled can be calculated by a sensor that can detect an angular change such as an angular velocity sensor. Therefore, the speed accuracy is improved by always using the optimum acceleration sensor offset.
[0083]
(3) Conventionally, in order to perform autonomous navigation in a car navigation system, it has been necessary to connect vehicle speed pulses from the vehicle side, but according to the present invention, connection of vehicle speed pulses is unnecessary.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic system configuration of an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a movement direction detected by an acceleration sensor and an angular velocity sensor according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a state of a moving body on a slope according to an embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a change in gravitational acceleration due to a change in inclination applied to the acceleration sensor according to the embodiment of the present invention.
5A and 5B show a relationship between an acceleration sensor offset and a tilt according to an embodiment of the present invention, in which FIG. 5A is an explanatory diagram illustrating a state of a moving body, and FIG. 5B is a characteristic diagram illustrating an offset state corresponding to the tilt. .
FIG. 6 is a functional block diagram of an embodiment of the present invention.
FIG. 7 is a flowchart showing a speed measurement operation according to the embodiment of the present invention.
FIG. 8 is a flowchart showing an operation of calculating an acceleration sensor offset according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... GPS antenna, 12 ... GPS receiver, 13 ... Acceleration sensor, 14 ... Angular velocity sensor, 15 ... A / D converter, 16 ... Arithmetic processing part, 17 ... Memory, 18 ... Communication part, 19 ... Navigation system, 20 ... 21: Movement direction detected by angle sensor, 22: Movement direction detected by acceleration sensor, 23: Slope, 24 ... Slope, 25 ... Road, 30 ... Each data acquisition means, 31 ... Acceleration by GPS and acceleration sensor Sensor offset calculating means, 32... Acceleration sensor offset calculating means using angular velocity sensors, 33... Speed calculating means, 34... GPS acceleration average calculating means, 35.

Claims (6)

In a speed measurement method for measuring the speed of the mobile body using an acceleration sensor and a GPS receiver provided in the mobile body,
When the acceleration sensor offset satisfies the first condition that the reception status of the GPS receiver is good and the speed obtained from the GPS receiver information is equal to or higher than the reliability lower limit X [km / h]. The gravitational acceleration component due to the inclination of the moving body is corrected using GPS speed information, and the moving body is detected using the detection output of the angular velocity sensor that detects a change in the inclination of the moving body when the first condition is not satisfied. Correct the gravitational acceleration component due to the tilt of
When satisfying the second condition that the reception status of the GPS receiver is good, the speed based on the speed information obtained by the GPS receiver as a speed measurement value,
When the second condition is not satisfied, a speed measured based on an output value of the acceleration sensor is used as a speed measurement value. In a speed measurement method for measuring the speed of the mobile body using an acceleration sensor and a GPS receiver provided in the mobile body,
When the reception condition of the GPS receiver is good and the condition that the speed obtained from the GPS receiver information is equal to or higher than the lower reliability limit X [km / h], the acceleration sensor offset is Using the speed information, correct for the gravitational acceleration component due to the inclination of the moving body, calculate the speed of the moving body,
When the condition is not satisfied, the acceleration sensor offset is corrected for the gravitational acceleration component due to the inclination of the moving body using the detection output of the sensor that detects a change in inclination, and the speed of the moving body is calculated. speed measurement method to. Correction of the offset of the acceleration sensor using the GPS receiver is performed based on average values of speed information measured by the GPS receiver and acceleration information measured by the acceleration sensor. The speed measuring method according to claim 1 . Correction of the offset of the acceleration sensor using the GPS receiver is performed based on average values of speed information measured by the GPS receiver and acceleration information measured by the acceleration sensor. The speed measurement method according to claim 2 . In a speed measuring device that measures the speed of the moving body using an acceleration sensor and a GPS receiver provided in the moving body,
  The acceleration sensor and the GPS receiver satisfy the first condition that the reception status of the GPS receiver is good and the speed obtained from the information of the GPS receiver is equal to or higher than the lower reliability limit X [km / h]. First correction means for calculating an offset obtained by correcting the gravitational acceleration component due to the inclination of the acceleration sensor based on the speed information obtained in step (i),
  Second correction means for calculating an offset obtained by correcting the gravitational acceleration component due to the inclination of the acceleration sensor based on information obtained by the angular velocity sensor for detecting a change in inclination when the first condition is not satisfied;
  When the second condition that the reception status of the GPS receiver is satisfactory is satisfied, the speed is calculated using the offset of the acceleration sensor calculated by the first correction means, and the speed information of the GPS receiver is calculated. When the second condition is not satisfied, speed calculation means for calculating the speed using the offset of the acceleration sensor calculated by the second correction means;
  A speed measuring device comprising: The correction of the offset of the acceleration sensor using the GPS receiver is performed based on average values of speed information measured by the GPS receiver and acceleration information measured by the acceleration sensor. Item 6. The speed measurement device according to Item 5 .

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