Method and system for measuring deformation of a surface
Deformation of a surface, such as a pavement surface is measured using a rolling weight or wheel carrying one or more accelerometers positioned to measure the deformation occurring at a point on or near the perimeter of the wheel. The weight is rolled over the surface to be measured. The signals developed by the one or more accelerometers during a stationary cycloidal period of the point on the perimeter of the wheel are analysed to provide a measure of surface deformation based on the one or more signals.
1. A method of measuring deformation of a surface comprising:
a. providing an accelerometer at or near the periphery of a rolling weight, the accelerometer positioned to revolve with the rolling weight;
b. rolling the rolling weight over the surface to deform the surface;
c. analyzing one or more signals developed by the accelerometer during a stationary cycloidal period of the accelerometer in which centrifugal forces on the accelerometer are reduced and a signal developed by the accelerometer in response to the deformation of the surface is enhanced; and
d. developing a measure of the deformation of the surface based on the one or more signals.
2. The method claim 1 wherein:
the accelerometer is positioned to measure deformation directly beneath the rolling weight;
the measure of the deformation of the surface is a measure of deformation of the surface directly beneath the rolling weight.
3. A method as claimed in claim 1 employing a track passing about two or more wheels including one or more accelerometer in the track arranged so that measurements are obtained from the accelerometer when a wheel is above an accelerometer in the track.
4. A method as claimed in claim 1 wherein each accelerometer is enclosed in a ruggedised housing.
5. A method as claimed in claim 1 wherein each accelerometer is embedded in a tire tread generally with the tire surface.
6. A method as claimed in claim 1 wherein the accelerometer is embedded in a belt or mesh secured to the rolling weight.
7. A method as claimed claim 1 wherein a plurality of accelerometers are provided about the periphery of a rolling weight.
8. A method as claimed in claim 7 wherein the accelerometers are evenly spaced.
9. A method as claimed in claim 1 including a plurality of wheels in which different wheel configurations are employed in terms of one or more of: wheel tracking, wheel offset, wheel loading, wheel stiffness and wheel tire pressure.
10. A method as claimed in claim 1 wherein each accelerometer includes a data logger.
11. A method as claimed in claim 1 wherein each accelerometer or IMU includes a wireless transmitter.
12. A method as claimed claim 1 wherein each accelerometer includes a transmitter for transmitting information from each accelerometer or IMU that is mounted on the rolling weight away from the periphery of the rolling weight.
13. A method of measuring deformation of a surface comprising:
a. providing an inertial measurement unit (IMU) at or near the periphery of a rolling weight, the IIMU positioned to revolve with the rolling weight;
b. rolling the rolling weight over the surface to deform the surface;
c. analyzing one or more signals developed by the IMU during a stationary cycloidal period of the IIMU in which centrifugal forces on the IMU are reduced and a signal developed by the IMU in response to the deformation of the surface is enhanced; and
d. developing a measure of the deformation of the surface based on the one or more signals.
14. A method as claimed in claim 13 wherein the IMU includes one or more accelerometer and one or more gyroscope.
15. A method as claimed in claim 14 wherein the IMU includes three accelerometers with their axes of measurement orthogonal to one another.
16. A method as claimed in claim 14 wherein the IMU includes three gyroscopes with their axes of measurement orthogonal to one another.
17. A method as claimed in claim 14 wherein the IMU includes one or more magnetometers.
18. A method as claimed in claim 17 wherein the IMU includes three magnetometers with their axes of measurement orthogonal to one another.
19. A method as claimed in claim 13 wherein the rolling weight is a wheel.
20. A method as claimed in claim 19 wherein the wheel is a loaded wheel.
21. A method as claimed in claim 20 wherein a plurality of wheels are employed.
22. A method as claimed in claim 21 wherein two or more wheels are offset and each include an accelerometer at or near the periphery of each wheel.
23. A method as claimed in claim 21 including a loaded wheel and a wheel having a lesser loading offset from the loaded wheel having an accelerometer at or near its periphery.
24. A method as claimed in claim 13 wherein tire stiffness or pressure is adjusted to vary the effective loaded area of a rolling weight.