Inclination detector and onboard apparatus

• US 10,001,361 B2
• Filed: 08/01/2012
• Issued: 06/19/2018
• Est. Priority Date: 08/01/2012
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Yamashita, Toshiyuki
• Primary Examiner(s): Quigley, Kyle R
• Application Number:
  US14/395,771
• Publication Number:
  US 20150088455A1
• Time in Patent Office: 2,148 Days
• CPC Class Codes: B60Q 1/115 by electric means details of the electric drive components, e.g. motors, shafts, ball joints B60Q1/076
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01C 9/08 Means for compensating acceleration forces due to movement of instrument
• CPC Class Codes: G01P 15/14 by making use of gyroscopes gyroscopes per se G01C19/00
• CPC Class Codes: G01P 15/16 by evaluating the time-derivative of a measured speed signal

Abstract

A real acceleration computing unit 3 calculates the real acceleration Gw in the direction of travel of a vehicle by acquiring the velocity V a wheel speed sensor 12 installed in the vehicle detects. A road surface gradient computing unit 5 calculates the inclination of a road surface (road surface gradient θ1) from the real acceleration Gw and the accelerations Gx and Gz in the back and forth and up and down directions of the vehicle an acceleration sensor 11 installed in the vehicle detects. A pitching angle computing unit 6 calculates the inclination of the vehicle with respect to the road surface (pitching angle θ2) from the real acceleration Gw and the accelerations Gx and Gz.

Claims

1. An inclination detector comprising:

an inclination computing device that calculates one of or both of a road surface gradient θ

1 and a pitching angle θ

2 from acceleration G_x in back and forth direction and from acceleration G_z in up and down direction of a vehicle and from real acceleration G_w in direction of travel of the vehicle, the road surface gradient being an inclination in back and forth direction of a road surface on which the vehicle is placed, and the pitching angle θ

2 being an inclination in the back and forth direction of the vehicle with respect to the road surface; and

a first communication interface that transmits, to an onboard apparatus including an optical axis adjuster installed in the vehicle, a value calculated by the inclination computing device, wherein the pitching angle θ

2 as the calculated value is used for controlling an angle of light output by a light of the vehicle,

wherein the inclination computing device is configured to

calculate the road surface gradient θ

1 through an expression (1-2) which is derived from an expression (1-1) by linearly approximating sin<sup>−

1</sup> in the expression (1-1), where g is gravitational acceleration and γ

is a predetermined coefficient,

θ

1=sin<sup>−

1</sup>{(−

Gx²−

Gz²+Gw²+g²)/2Gwg} 

 

(1-1)

θ

1=γ

(−

Gx²−

Gz²+Gw²+g²)/2Gw g 

 

(1-2)

calculate the pitching angle θ

2 through an expression (2-2) which is derived from an expression (2-1) by linearly approximating tan<sup>−

1</sup> and sin<sup>−

1</sup> in the expression (2-1), where α and

β

are predetermined coefficients, and

θ

2=tan<sup>−

1</sup>(Gx/Gz)+sin<sup>−

1</sup>{(Gx²+Gz²+Gw²−

g²)/2Gw/sqrt(Gx²+Gz²)} 

 

(2-1)

θ

2=α

(Gx/Gz)+β

{(Gx²+Gz²+Gw²−

g²)/2Gw/sqrt(Gx²+Gz²)} 

 

(2-2)

obtain in advance the coefficients α

, β

, and γ

to be applied to the expressions (1-2) and (2-2).

2. The inclination detector according to claim 1, further comprising:

a second communication interface that acquires velocity in the direction of travel from a wheel speed sensor installed in the vehicle; and

a real acceleration computing device that calculates the real acceleration in the direction of travel by differentiating the velocity acquired via the second communication interface.

3. The inclination detector according to claim 1, further comprising:

a second communication interface that acquires acceleration in any two-axis directions from a two-axis acceleration sensor installed in the vehicle, the two-axis acceleration sensor being installed in a state in which at least one axis has a tilt with respect to a horizontal plane passing through the back and forth direction and right and left direction of the vehicle and with respect to a vertical plane passing through the right and left direction and up and down direction of the vehicle; and

an acceleration converter that converts accelerations in the any two-axis directions acquired via the second communication interface to acceleration in the back and forth direction and to acceleration in the up and down direction by using mounting information of the two-axis acceleration sensor.

4. The inclination detector according to claim 1, further comprising:

a second communication interface that acquires acceleration in the back and forth direction and acceleration in the up and down direction from a two-axis acceleration sensor which is installed in the vehicle in a state in which a first axis is parallel to the back and forth direction of the vehicle, and a second axis is parallel to the up and down direction of the vehicle.

5. The inclination detector according to claim 1, further comprising:

a two-axis acceleration sensor that is installed in the vehicle in a state in which a first axis is parallel to the back and forth direction of the vehicle and a second axis is parallel to the up and down direction of the vehicle, and that detects acceleration in the back and forth direction and acceleration in the up and down direction.

6. The inclination detector according to claim 1, wherein

the inclination computing device is configured to

determine whether the vehicle is running or stopped on a basis of a velocity acquired by a wheel speed sensor installed in the vehicle,

calculate the road surface gradient θ

1 and the pitching angle θ

2 through the expressions (1-2) and (2-2) when it is determined that the vehicle is running, and

when it is determined that the vehicle is stopped, hold the road surface gradient θ

1, which has been calculated in a condition where the vehicle is running, and calculate the pitching angle θ

2 by calculating or approximately calculating the following two expressions using the road surface gradient θ

1 having been held and the acceleration Gx or the acceleration Gz,

Gx=−

g sin(θ

1+θ

2) or Gz=−

g cos(θ

1+θ

2)

where g is gravitational acceleration.

7. The inclination detector according to claim 3, further comprising:

a sensitivity correcting device that corrects, while the vehicle is stopped and when difference between the gravitational acceleration and components of a vector of the acceleration in the back and forth direction and of a vector of the acceleration in the up and down direction is greater than a prescribed first threshold, sensitivity of the two-axis acceleration sensor in accordance with the individual accelerations and the gravitational acceleration.

8. The inclination detector according to claim 7, wherein

the sensitivity correcting device sends information to the inclination computing unit if the difference between the gravitational acceleration and the components of the vector of the acceleration in the back and forth direction and of the vector of the acceleration in the up and down direction is greater than a prescribed second threshold that is greater than the first threshold;

and

the inclination computing device substitutes a preset value for one of or both of the road surface gradient and the pitching angle when receiving the information from the sensitivity correcting device.