JP2011209162A - Navigation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a navigation system capable of determining a mount angle accurately by eliminating any influence of road inclination.SOLUTION: A navigation system 1, which can be mounted at an arbitrary angle on a mounting pedestal attached to a vehicle, includes a triaxial acceleration sensor 4 to detect the acceleration in each direction of three axes that are perpendicular to each other, and a control section 2 to calculate a mount angle of the navigation system 1. The control section 2 obtains first and second accelerations that are accelerations in each direction of two axes for the acceleration detected by the triaxial acceleration sensor 4 during driving of a vehicle, calculating the mount angle in accordance with the ratio of absolute values for the first and second accelerations and the acceleration polarity.

Description

  The present invention relates to a navigation device that can be installed at an arbitrary angle on a mounting base attached to a vehicle and includes a three-axis acceleration sensor.

  Many of the currently used navigation devices include an acceleration sensor and a gyro sensor.

  The output sensitivity of the acceleration sensor and the gyro sensor decreases depending on the size of the navigation device mounting angle. This is because these sensors can only detect physical quantities along the detection axis direction of the sensors. That is, if the detection axis of the sensor is deviated from the direction to be originally detected, the physical quantity that should be detected by that amount is not output, resulting in a reduction in sensitivity.

  If the decrease in output sensitivity due to these mounting angles is not corrected, the position and direction of the vehicle cannot be calculated correctly. Therefore, the conventional navigation apparatus calculates the mounting angle and corrects the output of the gyro sensor or the acceleration sensor based on this angle.

  On the other hand, instead of a stationary navigation device, a portable navigation device called PND (Portable Navigation Device) has recently been installed in a vehicle. Unlike the stationary navigation device, the portable navigation device is installed in the vehicle via a mounting base that is mounted on the dashboard of the vehicle by a sucker or the like. The portable navigation device is a navigation device that can be removed from the mounting base and used (portable) outside the vehicle.

  Since the portable navigation device is portable, removal and installation are frequently repeated. Since the installation of the navigation device on the mounting base is performed by the user, the mounting angle is different every time and is not uniquely determined.

  Therefore, some conventional navigation devices that calculate the mounting angle calculate the mounting angle from the absolute value and the polarity of the acceleration with the front-rear direction output from the acceleration sensor as the detection axis.

  Since the absolute value of the acceleration output to the longitudinal detection axis of the acceleration sensor changes according to the mounting angle, the mounting angle can be calculated from the absolute value of the output acceleration.

  For example, Patent Document 1 is known as a prior art document relating to the invention of this application.

JP 2009-14732 A

However, the navigation device that calculates the mounting angle calculates the mounting angle from the absolute value of acceleration with the front-rear direction detected by the acceleration sensor as the detection axis. This calculation is based on the assumption that the vehicle is on a horizontal road. For example, when the conventional attachment angle is calculated when the vehicle is on a sloped road, the attachment angle is erroneously calculated by the inclination angle of the road.

  As described above, the conventional navigation device has a problem in that when the road has an inclination, the inclination angle of the road is included as an error and the attachment angle cannot be calculated correctly.

  The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a navigation device that can eliminate the influence of road inclination and can accurately determine the mounting angle.

  In order to achieve the above object, the navigation device of the present invention acquires first and second accelerations that are accelerations in the respective directions for the two axes of acceleration detected by the three-axis acceleration sensor during traveling of the vehicle. The mounting angle is calculated from the ratio between the absolute values of the first and second accelerations and the polarity of the acceleration.

  The navigation device of the present invention calculates the attachment angle from the ratio of the absolute values of the first and second accelerations and the polarity of the acceleration. Since the ratio between the first acceleration and the second acceleration is constant without depending on the inclination angle of the road, there is an effect that the attachment angle of the navigation device can be accurately obtained even when the vehicle is on an inclined road. .

The block diagram of the navigation apparatus in one embodiment of this invention Diagram for explaining installation of the device in the passenger compartment The figure for demonstrating the acceleration at the time of vehicle start of the apparatus Flow chart for explaining the operation of the apparatus Flow chart for explaining the operation of the apparatus Flow chart for explaining the operation of the apparatus Flow chart for explaining the operation of the apparatus Flow chart for explaining the operation of the apparatus

  Hereinafter, a navigation device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a navigation apparatus according to an embodiment of the present invention. FIG. 2 is a view for explaining installation of the navigation device in the vehicle interior according to the embodiment of the present invention, and FIG. 3 is a view for explaining acceleration at the time of vehicle start.

  A navigation device 1 shown in FIG. 1 includes a control unit 2, a gyro sensor 3, a triaxial acceleration sensor 4, a GPS receiver 5, a storage unit 6, a speaker 7, and a display unit 8.

  The control unit 2 calculates the current position of the navigation device 1 based on the outputs of the gyro sensor 3, the triaxial acceleration sensor 4, and the GPS receiver 5, and reads out the calculated map information around the current location from the storage unit 6. Subsequently, the control unit 2 superimposes a mark indicating the current location on the map information around the current location and displays it on the display unit 8. When the user of the navigation device 1 has set a destination, the route from the current position to the destination is also superimposed on the map information. Further, the control unit 2 guides the route from the speaker 7 to the destination by voice as necessary.

  The navigation device 1 is installed via a vehicle and a mounting base 9 as shown in FIGS. The mounting base 9 is mounted on the dashboard of the vehicle by a sucker or the like. The navigation device 1 is fixed to the holder of the mount 9.

  First, the positional relationship used when describing the navigation device according to one embodiment of the present invention will be described. The X axis in FIG. 2 is an axis whose forward direction is the direction in which the vehicle goes straight. This X-axis is called the front-rear direction axis. Further, the positive direction of the X axis is referred to as the vehicle front direction, and the negative direction of the X axis is referred to as the vehicle rear direction.

  The Y axis in FIG. 2 is an axis that is perpendicular to the X axis and that has the positive direction as the positive direction when viewed from the front of the vehicle. This Y-axis is called the left-right direction axis. Further, the positive direction of the Y axis is called the vehicle left direction, and the negative direction of the Y axis is called the vehicle right direction.

  Further, the Z axis in FIG. 2 is an axis that is perpendicular to the X axis and that has a positive direction when viewed from the front of the vehicle. This Z axis is referred to as the vertical axis. Further, the positive direction of the Z axis is referred to as the vehicle upward direction, and the negative direction of the Z axis is referred to as the vehicle downward direction.

  The front-rear direction axis, the left-right direction axis, and the vertical direction axis are all axes based on the vehicle, not based on the ground surface or the installation surface of the vehicle.

  Next, each axis viewed from the navigation device 1 will be described. The X ′ axis, Y ′ axis, and Z ′ axis described below are axes by which the triaxial acceleration sensor 4 detects acceleration.

  The X ′ axis in FIG. 2 is an axis whose forward direction is the direction from the back surface of the navigation device 1 toward the display unit 8. This X ′ axis is referred to as a “front-rear direction detection axis”. The positive direction of the X ′ axis is referred to as “front detection direction”, and the negative direction of the X ′ axis is referred to as “rear detection direction”.

  2 is an axis that is perpendicular to the X ′ axis and has a positive direction as a positive direction when viewed from the front of the display unit 8 of the navigation device 1. This Y ′ axis is referred to as a “left / right direction detection axis”. The positive direction of the Y ′ axis is referred to as “left detection direction”, and the negative direction of the Y ′ axis is referred to as “right detection direction”.

  2 is an axis that is perpendicular to the X ′ axis and that has a positive direction as a positive direction when the display unit 8 of the navigation device 1 is viewed from the front. This Z′-axis is referred to as “vertical direction detection axis”. The positive direction of the Z ′ axis is referred to as “upper detection direction”, and the negative direction of the Z ′ axis is referred to as “lower detection direction”.

  “Pitch attachment angle θ” in FIG. 2 is the difference between the longitudinal detection axis of the acceleration sensor and the longitudinal axis, and is the attachment angle of the navigation device 1 in the pitch direction. Similarly, the difference in angle between the vehicle left-right direction axis and the left-right direction detection axis of the acceleration sensor is the yaw attachment angle φ, and the angle difference between the vehicle vertical direction axis and the acceleration sensor vertical direction detection axis is the roll attachment angle ψ. Call.

  FIG. 3 is a schematic diagram of acceleration output when the vehicle starts. The output of the triaxial acceleration sensor 4 when the vehicle starts when the road inclination angle is α is shown.

  If the acceleration in the traveling direction at the start of the vehicle is Accx, acceleration corresponding to the mounting angle is output to each axis of the triaxial acceleration sensor 4. The acceleration output to the front-rear direction detection axis is referred to as ΔAx, the acceleration output to the left-right direction detection axis is referred to as ΔAy, and the acceleration output to the vertical direction detection axis is referred to as ΔAz.

  The “absolute value” of acceleration indicates the magnitude of the output amount of ΔAx, the magnitude of the output amount of ΔAy, and the magnitude of the output amount of ΔAz in each output of ΔAx, ΔAy, and ΔAz.

  The “polarity” of acceleration is a plus or minus sign in each output of ΔAx, ΔAy, ΔAz, and is defined by the output direction with respect to the front-rear direction detection axis, the left-right direction detection axis, and the vertical direction detection axis. Is done.

  The control unit 2 controls each unit of the navigation device 1. The controller 2 includes a CPU or MPU (not shown), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

  The CPU or MPU executes a program stored in a ROM (not shown) to control the operation of each functional block shown in FIG. The CPU and MPU use the RAM as a work area during execution of the program.

  The storage unit 6 includes a storage device such as a DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory), and stores the calculation results of the navigation device 1 such as the calculation results of the control unit 2.

  The control unit 2 is a processing unit that calculates the mounting angle of the navigation device 1 with respect to the vehicle using the output of the triaxial acceleration sensor 4. The calculated mounting angle information is used for correcting the outputs of the triaxial acceleration sensor 4 and the gyro sensor 3.

  The gyro sensor 3 detects an angular velocity of rotation about the vertical axis of the vehicle. From this output, it is possible to calculate a relative azimuth change amount in the traveling direction of the host vehicle. In addition, by using together the gyro sensor 3 that detects the angular velocity of rotation about the vehicle longitudinal axis (roll rotation direction) and the angular velocity of rotation about the vehicle horizontal axis (pitch rotation direction), This can be applied to the correction of the vehicle position.

  The triaxial acceleration sensor 4 detects the acceleration of the longitudinal detection axis, the acceleration of the lateral detection axis, and the acceleration of the vertical detection axis. In addition to calculating the mounting angle of the navigation device with respect to the vehicle, it is also possible to calculate the acceleration of the vehicle when radio waves from a GPS (Global Positioning System) satellite cannot be received.

  The GPS receiver 5 receives radio waves from a plurality of GPS satellites and demodulates them to measure the absolute position of the receiver. The current position of the vehicle, the current position after map matching, the speed, and the direction of travel can be measured by using the GPS receiver 5 and various sensors described later alone or in combination.

The storage unit 6 stores map information such as road data, facility data, and background data.
For example, it is a non-volatile storage element such as a hard disk or a flash memory. In addition, the memory | storage part 6 does not need to memorize | store map information beforehand, and may download map information from a center by communication means (not shown), such as a mobile phone. The control unit 2 reads map information from the storage unit 6.

  The speaker 8 guides the route to the destination to the user of the navigation device 2 by voice under the control of the control unit 2.

  The display unit 8 includes a screen such as a liquid crystal display, and displays a map image around the vehicle position along with guidance information such as a mark indicating the current position of the vehicle and a route to the destination under the control of the control unit 2. Is. Moreover, the touch panel which a user can input can be provided.

  The mounting base 9 is a base that is mounted on the dashboard of the vehicle by a sucker or the like, and is used for fixing the navigation device 1 to the vehicle. The navigation device 1 is fixed to the holder of the mount 9.

  The user of the navigation device 1 can remove the navigation device 1 from the holder and use it outside the vehicle. Further, the user can attach the navigation device 1 to the holder again and use it in the vehicle.

  The processing operation of the navigation device 1 configured as described above will be described with reference to FIGS. 4-8 is a figure explaining operation | movement of the navigation apparatus 1 in one embodiment of this invention.

  The control unit 2 determines whether the vehicle is traveling (S1). The controller 2 uses the outputs of the GPS receiver 5 and the triaxial acceleration sensor 4 for this determination. Whether the vehicle is traveling can be determined from speed information obtained from the GPS receiver 5, but since GPS is not always capable of positioning, it is desirable to determine from the output of the three-axis acceleration sensor.

  When the navigation device 1 is activated, the control unit 2 continues to acquire the acceleration output to the front-rear direction axis of the triaxial acceleration sensor 4 or the acceleration of all three axes in a fixed time unit.

  The control unit 2 calculates the variation width of the acquired acceleration, and when the variation width falls within an arbitrary variation width for a certain time (for example, 3 seconds), the control unit 2 determines that the vehicle is stopped and performs processing. Proceed to S2. The control unit 2 determines that the vehicle is running when the width does not fall within an arbitrary variation width, and advances the process to S3.

  The arbitrary variation width can be set to an appropriate value in advance, or can be set to the output width of the triaxial acceleration sensor 4 when the speed information obtained from the GPS receiver 5 indicates almost zero. If it is determined that the vehicle is stopped, the control unit 2 stores the position where the vehicle is stopped using the vehicle position information calculated from the GPS receiver 5 and the triaxial acceleration sensor 4.

  When NO in S1, the control unit 2 acquires the output of the triaxial acceleration sensor 4 when the vehicle is stopped. The output data obtained from the triaxial acceleration sensor 4 is averaged until it is determined that the vehicle is traveling.

  The averaging process is executed separately for the output of the front-rear direction detection axis, the output of the left-right direction detection axis, and the output of the vertical direction detection axis. The averaging process is, for example, a section average or a moving average. The output of the triaxial acceleration sensor 4 averaged when the vehicle is stopped is stored as the acceleration sensor output at the time of stop. This value is held until the stop position is changed in S1. When the stop position is changed, the acceleration sensor output at the time of stop is recalculated and the value is updated.

  The stop acceleration sensor output is an error component in which a gravity acceleration component due to road inclination or an error inherent in the device is output, and is an output component different from the vehicle acceleration. By calculating the acceleration sensor output at the time of stopping, these error components can be removed from the acceleration sensor output.

  When YES in S1, the control unit 2 calculates the acceleration sensor output during travel (S3). The output of the longitudinal detection axis, the output of the horizontal direction detection axis, and the output of the vertical direction detection axis are acquired from the triaxial acceleration sensor 4, and the averaging process is executed on each of them in the same manner as in S2. The acceleration sensor output averaged during traveling is stored as the traveling acceleration sensor output. When the stop position is updated in S1, the traveling acceleration sensor output value is cleared.

  After S3, the control unit 2 calculates the vehicle acceleration output to each detection axis of the triaxial acceleration sensor 4 (S4). Details of the processing operation of the control unit 2 will be described with reference to FIG.

The control unit 2 refers to the stop acceleration sensor output (S41), and then refers to the travel acceleration sensor output (S42). Subsequently, the control unit 2 calculates the difference between the traveling acceleration sensor output and the stopping acceleration sensor output (S43). The acceleration sensor output at the time of running is defined as Ax (running), Ay (running), Az (running) as the output of the longitudinal detection axis, the output of the left and right direction detection axis, and the acceleration of the stop direction If the sensor output of the front / rear direction detection axis, the left / right direction detection axis, and the vertical direction detection axis are defined as Ax (stop), Ay (stop), and Az (stop), ΔAx and ΔAy in FIG. , ΔAz, is calculated by the following calculation.
ΔAx = Ax (travel) −Ax (stop) (1)
ΔAy = Ay (running) −Ay (stop) (2)
ΔAz = Az (running) −Az (stop) (3)
The triaxial acceleration sensor 4 has a certain amount of inherent error due to the device, and this error is referred to as “device-induced offset error”. Note that the device-induced offset error varies with temperature.

  Both the travel acceleration sensor output and the stop acceleration sensor output include an equal amount of device-induced offset error. However, when the device passes for a long time, the offset error due to the device fluctuates due to the influence of temperature.

  In addition, as long as the update interval of the acceleration sensor output at the time of stop is short, both outputs include an equal amount of gravitational acceleration components. However, when the update interval of the acceleration sensor output at the time of the stop becomes longer, the magnitude of the gravitational acceleration component included in the output does not become equal due to the influence of the road inclination change.

  Therefore, by taking the difference between them, it is possible to remove these influences, and only the acceleration of the vehicle is output to ΔAx, ΔAy, ΔAz.

  The control unit 2 converts ΔAx, ΔAy, and ΔAz obtained here from a voltage value to an acceleration unit system (S44). Note that any two of ΔAx, ΔAy, and ΔAz correspond to the first and second accelerations.

  Next to S3, the control unit 2 determines how many meters the current traveling position has advanced from the previously stopped position, and controls the calculation of the attachment angle according to the result. The current traveling position is calculated from the outputs of the GPS receiver 5 and the triaxial acceleration sensor 4 (S5).

  As the previously stopped position, the stop position stored in S1 is used. If the difference between the two is taken and the travel distance is within a threshold meter (for example, 10 meters), the control unit 2 advances the process to S6. If the travel distance is greater than or equal to the threshold meter, the process proceeds to S8.

  When YES in S5, the control unit 2 calculates the pitch attachment angle (S6). Details of S6 will be described with reference to the flowchart of FIG.

The controller 2 acquires the vehicle acceleration ΔAx output to the longitudinal detection axis of the acceleration sensor calculated in S44 (S61). Subsequently, the control unit 2 acquires the vehicle acceleration ΔAz output in the vertical direction detection axis of the acceleration sensor calculated in S44 (S62).

These ΔAx and ΔAz have the following relationship with the acceleration Accx in the traveling direction of the vehicle. The following formulas (4) and (5) are simplified formulas when the yaw mounting angle and the roll mounting angle are smaller than the pitch mounting angle. The exact formula is complex and is equivalent to the simplified formula unless the mounting angles are combined. When the mounting angles are combined, correction is performed in S11 described later.
ΔAx = Accx · cos θ Formula (4)
ΔAz = Accx · sin θ (5)
When Equation (4) and Equation (5) are solved by the pitch mounting angle θ, they are expressed by Equation (6).
θ = arctan (ΔAx / ΔAz) Equation (6)
The pitch attachment angle θ obtained by the equation (6) is obtained by the control unit 2 because the influence of the offset-induced error and the road inclination has been removed.

  After S6, the control unit 2 calculates the yaw attachment angle φ (S7). Details of S7 will be described with reference to the flowchart of FIG.

The control unit 2 acquires the vehicle acceleration ΔAx output to the longitudinal detection axis of the acceleration sensor calculated in S44 (S71). Subsequent to S71, the control unit 2 acquires the vehicle acceleration ΔAy output to the left-right direction detection axis of the acceleration sensor calculated in S44. These ΔAx and ΔAy have the following relationship with the vehicle traveling direction acceleration Accx. The following formula is a simplified formula when the pitch mounting angle θ and the roll mounting angle ψ are smaller than the yaw mounting angle φ.
ΔAx = Accx · cosφ Equation (7)
ΔAy = −Accx · sinφ (8)
When Equation (7) and Equation (8) are solved by the yaw attachment angle φ, they are expressed by Equation (9).
φ = arctan (ΔAy / ΔAz) Equation (9)
When NO in S5 or after the end of S7, the control unit 2 calculates the centrifugal force acceleration applied to the vehicle, and controls the calculation of the mounting angle according to the result (S8).

  Here, the centrifugal force acceleration uses the outputs of the GPS receiver 5 and the gyro sensor 3. The centrifugal force acceleration is obtained from the product of the velocity obtained from the GPS receiver 5 and the angular velocity in the yaw direction obtained from the gyro sensor 3. When the centrifugal force acceleration is output above a certain value, the control unit 2 advances the process to S9. When the centrifugal force acceleration falls within a certain value, the control unit 2 advances the process to S10.

  When YES in S8, the controller 2 calculates the roll mounting angle ψ (S9).

  When only the roll mounting angle ψ exists in the navigation device 1, the ratio of the vehicle traveling direction acceleration Accx output to each axis of the triaxial acceleration sensor 4 is constant regardless of the size of the roll mounting angle ψ. Therefore, the control unit 2 cannot calculate the roll attachment angle ψ from the ratio of Accx output to each axis of the triaxial acceleration sensor 4.

  Therefore, in the case of the roll mounting angle ψ, the calculation is performed based on the ratio of the lateral acceleration Accy of the vehicle output to each axis of the triaxial acceleration sensor 4. The lateral acceleration Accy of the vehicle is substantially 0 in a normal running state, but is greatly output when a centrifugal force is generated at the time of turning right or left at an intersection or a large curve.

When it is determined that the lateral acceleration Accy of the vehicle is sufficiently larger than the traveling acceleration Accelx of the vehicle, the acceleration output to each axis of the triaxial acceleration sensor 4 is assumed to be due to the lateral acceleration Accy of the vehicle. Can do. Since a dependency relationship is recognized between the roll mounting angle ψ and the ratio of Accy output to each axis of the acceleration sensor, the roll mounting angle ψ can be calculated.

  Details of S9 will be described with reference to the flowchart of FIG. First, the controller 2 acquires the vehicle acceleration ΔAy output to the left / right direction detection axis of the acceleration sensor calculated in S44 (S91). Subsequently, the control unit 2 acquires the vehicle acceleration ΔAz output to the vertical direction detection axis of the acceleration sensor calculated in S44 (S92).

These ΔAy and ΔAz have the following relationship with the lateral acceleration Accy of the vehicle. The following formula is a simplified formula when the pitch mounting angle θ and the yaw mounting angle φ are smaller than the roll mounting angle ψ.
ΔAy = Accy · cos ψ (10)
ΔAz = −Accy · sinψ Equation (11)
When Equation (10) and Equation (11) are solved by the roll mounting angle ψ, they are expressed by Equation (12).
ψ = arctan (ΔAz / ΔAy) (12)
When NO in S8 or after the end of S9, the control unit 2 has any two or more mounting angles among the pitch mounting angle θ, the yaw mounting angle φ, and the roll mounting angle ψ in the navigation device 1. It is determined whether or not (S10).

  Specifically, the control unit 2 determines whether any two of the pitch attachment angle θ, the yaw attachment angle φ, and the roll attachment angle ψ are equal to or larger than a threshold angle (for example, 5 degrees). . A case where any two angles are equal to or greater than the threshold angle for each is referred to as “composite”.

  If the number of attachment angles exceeding the threshold angle is two or more, the control unit 2 advances the process to S11. If the number of attachment angles exceeding the threshold angle is two or less, the control unit 2 advances the process to S12.

  When YES in S10, the control unit 2 corrects the pitch mounting angle θ, the yaw mounting angle φ, and the roll mounting angle ψ according to the combination of mounting angles determined to exceed the threshold angle (S11). .

  Since formulas (4), (5), (7), (8), (10), and (11) are not strict formulas, if any two or more of the mounting angles have a large angle, the calculation accuracy is descend. Therefore, it is necessary to correct the mounting angle as necessary.

The expression of the mounting angle varies depending on the coordinate system used for angle calculation, but in the present embodiment, a z-yx rotational coordinate system is adopted. When a strict expression is used, the following relational expression is established among the yaw attachment angle φ, the pitch attachment angle θ, the roll attachment angle ψ, and ΔAx, ΔAy, ΔAz. In the case where centrifugal force acceleration is generated, the lateral acceleration Accy of the vehicle is added to this and becomes a more complicated expression. Here, the following expression with Accy = 0 is an exact expression.
ΔAx = Accx (cosφ · cosθ) (13)
ΔAy = Accx (cosφ · sinθ · sinψ−sinφ · cosψ) (14)
ΔAz = Accx (cosφ · sinθ · cosψ + sinφ · sinψ) Equation (15)
The control unit 2 corrects the mounting angle using the relationship of Expression (13), Expression (14), and Expression (15). The attachment angle to be corrected is determined by a combination of the yaw attachment angle φ, the pitch attachment angle θ, and the roll attachment angle ψ whose attachment angle is equal to or greater than the threshold angle.

  For example, when the roll mounting angle ψ is 0, and the yaw mounting angle φ and the pitch mounting angle θ are greater than or equal to the threshold angle, only the yaw mounting angle φ is subject to correction. The reason why the pitch mounting angle θ is not subject to correction is that when the roll mounting angle ψ is 0, the calculation result is the same regardless of whether the simplified formula or the exact formula is used.

In the above case, when the yaw attachment angle φ is corrected using a strict formula, the correction formula is expressed as shown in formula (16). This equation is expressed by equation (16) when equation (13) and equation (14) are solved by yaw attachment angle φ after setting the roll attachment angle ψ to zero.
φ = −arctan (ΔAy / ΔAx · cos θ) (16)
Compared with the calculation formula (9) of the yaw attachment angle by the simplified formula, the difference depends on cos θ. When the pitch mounting angle θ is small, the influence is small, but when θ is large, the correct mounting angle is corrected by using a strict formula.

  The control unit 2 executes the correction of the attachment angle based on the same concept even when the combination of the attachment angles that are equal to or larger than the threshold angle is different from the above example.

  After S11, the control unit 2 stores the yaw mounting angle φ, pitch mounting angle θ, and roll mounting angle ψ corrected in S11 in the storage unit 6 (S12).

  When the yaw mounting angle φ, the pitch mounting angle θ, and the roll mounting angle ψ are newly calculated, an averaging process is performed using the mounting angle stored in the storage unit 6, and the mounting angle information in the storage unit 6 is obtained. Update.

  The mounting angle stored in the storage unit 6 is used for at least one sensitivity correction of the triaxial acceleration sensor 4 and the gyro sensor 3. It can also be used to correct sensitivity errors on other axes. Here, the sensitivity error in the other axis is an acceleration component in a direction different from the acceleration in the direction desired to be detected, which is included in the output of the triaxial acceleration sensor 4. For example, there is a case where acceleration in the vehicle left-right direction is output to the longitudinal detection axis of the triaxial acceleration sensor 4.

  As described above, the navigation device according to the embodiment of the present invention calculates the attachment angle based on the ratio of the absolute values of acceleration and the polarity of acceleration on the two axes. Since the ratio of the accelerations on the two axes is constant without depending on the inclination angle of the road, there is an effect that the attachment angle of the navigation device 1 can be obtained accurately even when the vehicle is on an inclined road. .

  In the present embodiment, using the acceleration when the vehicle starts running from the state where the vehicle is stopped as the two-axis acceleration used for calculating the mounting angle has the following effects.

  If the vehicle travels for a long time, the output of the triaxial acceleration sensor 4 is offset due to the temperature, and an error appears in the biaxial acceleration used to calculate the mounting angle. However, there is an effect that the influence of this error can be eliminated by using the acceleration when the vehicle starts running from the state where the vehicle is stopped. This is because there is no time difference between immediately before starting and immediately after starting, and therefore the influence of fluctuations in offset error due to temperature can be ignored.

In addition, when the road inclination α changes during traveling, an error due to the acceleration of the two axes used to calculate the attachment angle appears. However, by limiting the calculation of the attachment angle immediately after starting, the influence of the change in road inclination is also affected. There is an effect that it can be excluded. This is because the road inclination angle is the same when the vehicle stops and when the vehicle starts.

  INDUSTRIAL APPLICABILITY The present invention can be installed at an arbitrary angle on a mounting base attached to a vehicle, and is useful as a navigation device provided with a triaxial acceleration sensor.

DESCRIPTION OF SYMBOLS 1 Navigation apparatus 2 Control part 3 Gyro sensor 4 Triaxial acceleration sensor 5 GPS receiver 6 Memory | storage part 7 Speaker 8 Display part 9 Mounting stand

Claims (7)

A navigation device that can be installed at an arbitrary angle on a mounting base attached to a vehicle,
A three-axis acceleration sensor that detects acceleration in each direction of three axes orthogonal to each other;
A control unit for calculating the mounting angle of the navigation device,
The control unit obtains first and second accelerations that are accelerations in respective directions with respect to two axes of acceleration detected by the three-axis acceleration sensor during traveling of the vehicle, and absolute values of the first and second accelerations. A navigation device characterized in that the mounting angle is calculated from the ratio and acceleration polarity. The navigation device according to claim 1, wherein the control unit uses, as the first and second accelerations, accelerations when the vehicle starts running from a state where the vehicle is stopped. The navigation device according to claim 1, wherein the control unit calculates an attachment angle by calculating an arc tangent with respect to a ratio of absolute values of the first and second accelerations. The controller further calculates an offset value by averaging the outputs of the three-axis acceleration sensor for a predetermined time while the vehicle is stopped, and calculates the mounting angle after subtracting the offset value from the first and second acceleration values. The navigation device according to claim 1. The control unit pitch-mounts the rotation angle of the navigation device about the vertical direction of the vehicle as a mounting angle and the rotation angle of the navigation device about the horizontal direction when the vehicle is viewed from the front. The rotation angle of the navigation device with the angle and the longitudinal direction of the vehicle as an axis is defined as a roll mounting angle, and at least one of the yaw mounting angle, the pitch mounting angle, and the roll mounting angle is calculated. The navigation device according to 1. A gyro sensor that calculates an angular velocity with respect to a yaw rotation direction that is a rotation of the navigation device about the vertical direction of the vehicle;
A speed detector for detecting the speed of the vehicle in the traveling direction;
The control unit calculates a centrifugal force acceleration that is a product of the speed in the traveling direction of the vehicle detected by the speed detection unit and the angular velocity calculated by the gyro sensor, and the absolute value of the centrifugal force acceleration is a predetermined value. 6. The navigation apparatus according to claim 5, wherein a roll mounting angle is calculated when the above is true. The control unit, when at least two of the calculated yaw mounting angle, pitch mounting angle, and roll mounting angle satisfy an angle equal to or greater than a predetermined threshold,
The correction amount for the yaw mounting angle, pitch mounting angle, and roll mounting angle is calculated from the ratio of the calculation results of the two angles that satisfy the angle equal to or greater than the predetermined threshold, and each mounting angle is re-applied using the correction amount. The navigation apparatus according to claim 5, wherein calculation is performed.