# US 2015/0176989 A1 · Accelerometer-Based Hill Angle Estimation

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- Number: US 2015/0176989 A1
- Document ID: US20150176989A1
- Status: Published application
- Kind: A1
- Application number: 14/139,726
- Filed: 2013-12-23
- Published: 2015-06-25
- Earliest claimed: 2013-12-23
- Assignees: Hti IP, LLC
- Applicants: Hti IP, LLC
- Inventors: Stephen Christopher Welch; JAMES RONALD BARFIELD, JR.
- Web page: https://patentgrep.com/patent/US20150176989A1

## CPC

- G01C 9/02: Details
- G01P 21/00: Testing or calibrating of apparatus or devices covered by the preceding groups
- 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)
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})

## Abstract

The embodiments disclosed are directed to systems and methods for determining the inclination of a surface beneath a vehicle. In some embodiments, a method uses an accelerometer to determine a final surface inclination value. The final surface inclination value can then be used to compensate for the acceleration of the vehicle caused by gravity. The method includes receiving accelerometer values from the accelerometer. The method also includes determining surface inclination values based on the accelerometer values. The method further includes storing the surface inclination values. And the method includes applying a digital filter to the stored surface inclination values to determine a final surface inclination value.

## Claims

### Claim 1

A system comprising:
an accelerometer; and
an analysis component configured to:
determine a plurality of surface inclination values, wherein the surface inclination values are based on acceleration values received from the accelerometer;
store the surface inclination values;
determine, based on the stored surface inclination values, a final surface inclination value; and
output the final surface inclination value.

### Claim 2 (depends on 1)

The system of claim 1, wherein the analysis component is further configured to:
determine a plurality of products, wherein the products are the result of multiplying the surface inclination values by filter coefficients;
sum the products; and
output the sum.

### Claim 3 (depends on 2)

The system of claim 2, wherein the analysis component is further configured to:
record a plurality of GPS values;
record a plurality of sample acceleration values;
determine a plurality of elevation values, wherein the elevation values are based on referencing a digital elevation model (DEM) for the recorded GPS values;
determine, based on the elevation values, a plurality of DEM-based inclination values;
determine, based on the recorded sample acceleration values, a plurality of sample surface inclination values;
fit a model to the DEM-based inclination values and the sample surface inclination values; and
output coefficients of the model.

### Claim 4 (depends on 3)

The system of claim 3, wherein the analysis component determines the DEM-based inclination values by calculating an arctangent of a change in elevation values between consecutive DEM tiles divided by a distance between the consecutive DEM tiles.

### Claim 5 (depends on 3)

The system of claim 3, wherein the model is a linear model and the model is determined by a least squares method.

### Claim 6 (depends on 3)

The system of claim 3, wherein the analysis component is further configured to apply a Gaussian Process to the DEM-based inclination values.

### Claim 7 (depends on 1)

The system of claim 1, wherein the analysis component is further configured to:
transform the acceleration values to a coordinate frame of a vehicle;
determine, based on the final surface inclination value, a first force and a second force;
determine a plurality of compensated acceleration values, wherein the compensated acceleration values are determined by subtracting the forces from the transformed acceleration values; and
output the compensated acceleration values.

### Claim 8 (depends on 7)

The system of claim 7, wherein the analysis component is further configured to provide information showing a behavior of an operator of the vehicle based on the compensated acceleration values.

### Claim 9

A system comprising:
an analysis component including one or more processors configured to:
determine a plurality of surface inclination values, wherein the surface inclination values are based on acceleration values received from an accelerometer;
store the surface inclination values;
determine, based on the stored surface inclination values, a final surface inclination value; and
output the final surface inclination value.

### Claim 10 (depends on 9)

The system of claim 9, wherein the analysis component is further configured to:
transform the acceleration values to a coordinate frame of a vehicle;
determine, based on the final surface inclination value, a first force and a second force;
determine a plurality of compensated acceleration values, wherein the compensated acceleration values are determined by subtracting the forces from the transformed acceleration values; and
output the compensated acceleration values.

### Claim 11 (depends on 10)

The system of claim 10, wherein the analysis component is further configured to provide information showing a behavior of an operator of the vehicle based on the compensated acceleration values.

### Claim 12

A method for determining a surface inclination with respect to a vehicle, the method being performed by one or more processors and comprising:
determining a plurality of surface inclination values, wherein the surface inclination values are based on acceleration values received from an accelerometer;
storing the surface inclination values;
determining, based on the stored surface inclination values, a final surface inclination value; and
outputting the final surface inclination value.

### Claim 13 (depends on 12)

The method of claim 12, wherein determining the final surface inclination value comprises:
determining a plurality of products, wherein the products are the result of multiplying the surface inclination values by filter coefficients;
summing the products; and
outputting the sum.

### Claim 14 (depends on 13)

The method of claim 13, wherein the filter coefficients are determined by:
recording a plurality of GPS values;
recording a plurality of sample acceleration values;
determining a plurality of elevation values, wherein the elevation values are based on referencing a digital elevation model (DEM) for the recorded GPS values;
determining, based on elevation values, a plurality of DEM-based inclination values;
determining, based on the recorded sample acceleration values, a plurality of sample surface inclination values;
fitting a model to the DEM-based inclination values and the sample surface inclination values; and
outputting coefficients of the model.

### Claim 15 (depends on 14)

The method of claim 14, wherein the DEM-based inclination values are determined by calculating an arctangent of a change in elevation values between consecutive DEM tiles divided by a distance between the consecutive DEM tiles.

### Claim 16 (depends on 14)

The method of claim 14, wherein the model is a linear model and the model is determined by a least squares method.

### Claim 17 (depends on 14)

The method of claim 14, further comprising applying a Gaussian Process to the DEM-based inclination values.

### Claim 18 (depends on 12)

The method of claim 12, further comprising:
transforming the acceleration values to a coordinate frame of the vehicle;
determining, based on the final surface inclination value, a first force and a second force;
determining a plurality of compensated acceleration values, wherein the compensated acceleration values are determined by subtracting the forces from the transformed acceleration values; and
outputting the compensated acceleration values.

### Claim 19 (depends on 18)

The method of claim 18, further comprising providing information showing a behavior of an operator of the vehicle based on the compensated acceleration values.

### Claim 20 (depends on 19)

The method of claim 19, wherein the information showing the behavior of the operator is used to adjust an insurance rating model.