# US 8,150,651 B2 · Acceleration compensated inclinometer

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- Number: US 8,150,651 B2
- Document ID: US8150651B2
- Status: Granted
- Kind: B2
- Application number: 12/157,577
- Filed: 2008-06-11
- Published: 2009-12-17
- Granted: 2012-04-03
- Earliest claimed: 2008-06-11
- Assignees: Trimble Navigation Limited
- Inventors: Peter Van Wyck Loomis
- Web page: https://patentgrep.com/patent/US8150651B2

## CPC

- G01C 21/12: executed aboard the object being navigated; Dead reckoning
- G01C 9/08: Means for compensating acceleration forces due to movement of instrument
- G01C 21/30: Map- or contour-matching
- G01S 19/47: the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
- G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S)
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

An inclinometer using a speedometer and a forward-looking accelerometer for measuring inclination angle.

## Claims

### Claim 1

An inclinometer, comprising:
a speedometer to determine a forward speed;
an accelerometer to measure a forward acceleration;
a yaw rate sensor to measure a yaw angle rate;
a yaw distance compensator configured to use said yaw angle rate with a linear position offset of said accelerometer respective to a turn radius line to determine a position offset error; and
an incline angle calculator configured to use said acceleration, said yaw angle rate, said position offset error and said speed to calculate an incline angle.

### Claim 2 (depends on 1)

The inclinometer of claim 1, further comprising:
a return-to-position compensation detector to estimate said linear position offset using a double return loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

### Claim 3 (depends on 1)

The inclinometer of claim 1, further comprising:
a return-to-position compensation detector to estimate an accelerometer bias based on a comparison of a return altitude with a start altitude after a return to the same position; and
the incline angle calculator is further configured to use said accelerometer bias to calculate said incline angle.

### Claim 4 (depends on 1)

The inclinometer of claim 1, further comprising:
a return-to-position compensation detector to estimate an accelerometer bias based on a comparison of a return altitude to a start altitude after a return to the same position facing in an opposite direction; and
the incline angle calculator is further configured to use said accelerometer bias to calculate said incline angle.

### Claim 5 (depends on 1)

The inclinometer of claim 1, further comprising:
a restart bias detector to estimate an accelerometer bias at a restart of motion after a dormant time period, said estimate based on a last said incline angle before said dormant time period; and
the incline angle calculator is further configured to use said accelerometer bias to calculate said incline angle.

### Claim 6 (depends on 1)

The inclinometer of claim 1, further comprising:
a DR altitude calculator to calculate an altitude change based on said acceleration, said position offset error, and said speed;
a Kalman filter configured to filter said altitude change with at least one external altitude fix to estimate an accelerometer bias; and
the incline angle calculator is further configured to use said accelerometer bias for calculating said incline angle.

### Claim 7

An inclinometer, comprising:
a speedometer to determine a forward speed;
an accelerometer to measure a forward acceleration;
a yaw rate sensor to measure a yaw angle rate;
a yaw alignment compensator configured to use said yaw angle rate with said speed and a yaw alignment angle of said yaw rate sensor respective to a forward direction to determine a yaw alignment error; and
an incline angle calculator configured to use said acceleration, said yaw alignment error and said speed to calculate an incline angle.

### Claim 8 (depends on 7)

The inclinometer of claim 7, further comprising:
a return-to-position compensation detector to estimate said yaw alignment angle using a double return loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

### Claim 9

An inclinometer, comprising:
a speedometer to determine a forward speed;
an accelerometer to measure a forward acceleration;
a restart bias detector to estimate an accelerometer bias at a restart of motion after a dormant time period, said estimate based on a last incline angle before said dormant time period; and
an incline angle calculator configured to use said acceleration, said accelerometer bias and said speed to calculate a new said incline angle.

### Claim 10

An inclinometer, comprising:
a speedometer to determine a forward speed;
an accelerometer to measure a forward acceleration;
a DR altitude calculator to use said speed and said acceleration to calculate an altitude change;
a Kalman filter configured to filter said altitude change with at least one external altitude fix to estimate an accelerometer bias; and
an incline angle calculator configured to use said acceleration, said accelerometer bias and said speed to calculate an incline angle.

### Claim 11 (depends on 10)

The inclinometer of claim 10, wherein:
said external altitude fix is derived from GNSS signals.

### Claim 12 (depends on 10)

The inclinometer of claim 10, wherein:
said external altitude fix is derived from map matching.

### Claim 13

An inclinometer, comprising:
a speedometer to determine a forward speed;
an accelerometer to measure a forward acceleration;
an incline angle calculator to calculate incline angle based on said measured acceleration and rate of change of said speed;
a GNSS receiver to determine a GNSS-based position and a three dimensional GNSS-based heading including a GNSS-based incline angle;
a yaw rate sensor to measure a yaw angle rate; and wherein:
the incline angle calculator is configured to use said yaw angle rate, said GNSS-based position, said speed rate and said measured acceleration to determine a dead reckoning incline angle with a better accuracy than said GNSS-based upward heading.

### Claim 14 (depends on 13)

The inclinometer of claim 13, further comprising:
an electronic road map having a first and second parallel connecting ramp roads near to one another having different road incline angles; and wherein:
said dead reckoning incline angle is used to distinguish between said first and second ramp roads when said ramp roads are not reliably distinguished by said GNSS-based position.

### Claim 15

A method for determining incline angle, comprising:
determining a forward speed;
measuring a forward acceleration;
measuring a yaw angle rate;
using said yaw angle rate with a linear position offset respective to a turn radius line for determining a position offset error; and
using said acceleration, said position offset error and said speed for calculating an incline angle.

### Claim 16 (depends on 15)

The method of claim 15, further comprising:
estimating said linear position offset includes using a double loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

### Claim 17 (depends on 15)

The method of claim 15, further comprising:
estimating an accelerometer bias by comparing a return altitude with a return altitude to a start altitude after a return to the same position; and
using said accelerometer bias with said acceleration, said position offset error, and said speed for calculating said incline angle.

### Claim 18 (depends on 15)

The method of claim 15, further comprising:
estimating an accelerometer bias by comparing a return altitude with a start altitude after a return to the same position facing in an opposite direction; and
using said accelerometer bias with said acceleration, said position offset error, and said speed for calculating said incline angle.

### Claim 19 (depends on 15)

The method of claim 15, further comprising:
at a restart of motion after a dormant time period, estimating an accelerometer bias based on a last said incline angle before said dormant time period; and
using said accelerometer bias with said acceleration, said position offset error, and said speed for calculating said incline angle.

### Claim 20 (depends on 15)

The method of claim 15, further comprising:
using said speed and said acceleration for calculating an altitude change; and
Kalman filtering said altitude change with an external altitude fix for estimating an accelerometer bias; and
calculating an incline angle based on said acceleration, said accelerometer bias, and said speed.

### Claim 21

A method for determining incline angle, comprising:
determining a forward speed;
measuring a forward acceleration;
measuring a yaw angle rate;
using said yaw angle rate with said speed and a yaw alignment angle of said yaw rate sensor respective to a forward direction; and
using said acceleration, said yaw alignment error and said speed for calculating an incline angle.

### Claim 22 (depends on 21)

The method of claim 21, further comprising:
estimating said yaw alignment angle includes using a double loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

### Claim 23

A method for determining incline angle, comprising:
determining a forward speed;
measuring a forward acceleration;
at a restart of motion after a dormant time period, estimating an accelerometer bias based on a last said incline angle before said dormant time period; and
using said acceleration, said accelerometer bias and said speed for calculating an incline angle.

### Claim 24

A method for determining incline angle, comprising:
determining a forward speed;
measuring a forward acceleration;
using said speed and said acceleration for calculating an altitude change; and
Kalman filtering said altitude change with an external altitude fix to estimate said accelerometer bias; and
using said acceleration, said accelerometer bias and said speed for calculating an incline angle.

### Claim 25 (depends on 24)

The method of claim 24, further comprising:
deriving said external altitude fix from GNSS signals.

### Claim 26 (depends on 24)

The method of claim 24, wherein:
deriving said external altitude fix from map matching.

### Claim 27

A method for determining incline angle, comprising:
determining a forward speed;
measuring a forward acceleration;
calculating an incline angle based on said measured acceleration and a rate of change of said speed;
determining a GNSS-based position and a three dimensional GNSS-based heading including a GNSS-based incline angle;
measuring a yaw angle rate; and wherein:
calculating said incline angle includes using said yaw angle rate, said GNSS-based position, said speed rate and said measured acceleration for providing a dead reckoning incline angle having a better accuracy than said GNSS-based incline angle.

### Claim 28 (depends on 27)

The method of claim 27, further comprising:
providing an electronic road map having a first and second parallel connecting ramp roads near to one another having different road incline angles; and
using said dead reckoning incline angle to distinguish said first and second ramp roads when said ramp roads are not reliably distinguished by said GNSS-based position.