Accelerometer leveling in an actively controlled vehicle suspension
In an aspect, in general, a system and method compensate for a misalignment characteristic of one or more acceleration sensors fixed to a sprung mass of a vehicle, each acceleration sensor having a location on the vehicle and a desired orientation relative to the vehicle.
1. A method of determining a correction to be applied to an output of an acceleration sensor fixed to a vehicle having an active suspension system, the method comprising:
actuating the active suspension system to angularly displace the vehicle in one of roll, pitch and a combination of roll and pitch, relative to a surface that the vehicle is on;
receiving multiple, acceleration sensor, outputs due to the angular displacement of the vehicle; and
determining the correction based on the received multiple, acceleration sensor, outputs and a degree of angular displacement when each output is produced;
wherein each of the received multiple, acceleration sensor, outputs is effectively in response only to gravity.
2. The method of claim 1 , further comprising:
completing the method of claim 1 a first time and a second time; and
determining a first correction during the first time;
determining a second correction during the second time; and
determining the correction by averaging the first correction and the second correction;
wherein a direction that the vehicle is facing during the second time is effectively opposite a direction that the vehicle is facing during the first time.
3. The method of claim 1 , further comprising:
operating the vehicle;
during operation of the vehicle, obtaining a second acceleration sensor output;
modifying the second acceleration sensor output based on at least the correction; and
operating the active suspension system during the operation of the vehicle based on the modified second acceleration sensor output.
4. The method of claim 1 wherein determining the correction comprises:
determining an angular displacement at which the acceleration sensor output is at a maximum.
5. The method of claim 4 further comprising:
generating a curve fit of the received multiple, acceleration sensor, outputs as a function of the angular displacement;
wherein determining the angular displacement at which the outputs are at the maximum includes determining a maximum of the curve fit.
6. An apparatus for determining a correction for an output of an acceleration sensor fixed to a vehicle, comprising:
an active suspension system;
a controller configured to:
(a) actuate the active suspension system to angularly displace the vehicle in one of roll, pitch, and a combination of roll and pitch, relative to a surface that the vehicle is on;
(b) receive multiple, acceleration sensor outputs due to the angular displacement of the vehicle; and
(c) determine the correction based on the received multiple, acceleration sensor, outputs and a degree of angular displacement when each output is produced;
wherein each of the received multiple, acceleration sensor, outputs is effectively in response only to gravity.
7. The apparatus of claim 6 , wherein the controller is further configured to:
complete (a) through (c) a first time and a second time; and
determine a first correction during the first time;
determine a second correction during the second time; and
determine the correction by averaging the first correction and the second correction;
wherein a direction that the vehicle is facing during the second time is effectively opposite a direction that the vehicle is facing during the first time.
8. The apparatus of claim 6 , wherein the controller is further configured to:
during operation of the vehicle, obtain a second acceleration sensor output;
modify the second acceleration sensor output based on at least the correction; and
operate the active suspension system during the operation of the vehicle using the modified second acceleration sensor output.
9. The apparatus of claim 6 wherein the controller is further configured to:
determine the correction by determining an angular displacement at which the acceleration sensor output is at a maximum.
10. The apparatus of claim 9 wherein the controller is further configured to:
generate a curve fit of the received multiple, acceleration sensor, outputs as a function of the angular displacement;
wherein determining the maximum of the acceleration sensor signal output includes determining a maximum of the curve fit using one of interpolation, extrapolation and a combination of extrapolation and interpolation.