System and method for estimating lateral acceleration
Methods are provided for controlling various systems in a vehicle based on input signals from at least one physical sensor and at least one model of a vehicle or a portion of the vehicle. The controller may rely preferentially on one or the other inputs based on the frequency of a motion of the vehicle and the state of the vehicle or one or more portions of the vehicle.
1. A method for estimating a lateral acceleration of a vehicle, the method comprising:
generating a first signal based on a measurement from a sensor at time T;
computing the lateral acceleration of the vehicle with a model at the time T;
generating a second signal based on the computation at the time T;
generating an error signal based on a difference between the first signal and the second signal at the time T;
filtering the error signal to generate a filtered signal; and
estimating the lateral acceleration based on a sum of the filtered signal and the second signal.
2. The method of claim 1 , wherein the filtering is performed with a low pass filter that has a cutoff frequency.
3. The method of claim 1 , wherein the sensor is selected from the group consisting of an accelerometer and an IMU.
4. The method of claim 2 , further comprising adjusting the cutoff frequency based on an operating parameter of the vehicle.
5. The method as in claim 4 , wherein the operating parameter is selected from the group consisting of steering rate, steering angle, amount of driver counter steering, and timing of driver counter steering.
6. The method of claim 1 , wherein the model is a bicycle model.
7. The method of claim 2 , wherein the cutoff frequency of the low pass filter is increased with increasing steering rate.
8. A method for operating a system of a vehicle, the method comprising:
estimating a lateral acceleration of the vehicle, wherein in a first operating mode, the estimate of the lateral acceleration is based primarily on a measurement with a sensor on the vehicle, and wherein in a second operating mode, the estimate of the lateral acceleration is based primarily on a mathematical model of the vehicle; and
operating the system of the vehicle at least partially based on the estimate of the lateral acceleration;
wherein in the first operating mode and the second operating mode the estimating is based at least partially on a filtered signal using a low-pass filter.
9. The method of claim 8 , wherein the mathematical model is a bicycle model.
10. The method of claim 8 , wherein the system is an active suspension system.
11. A method for operating a system in a vehicle undergoing lateral acceleration, the method comprising:
producing a first signal representative of the lateral acceleration with a sensor that is sensitive to the lateral acceleration;
producing a second signal representative of the lateral acceleration using a mathematical model of the vehicle;
producing an error signal based on a difference between the first signal and the second signal;
filtering, using a low-pass filter, the error signal to produce a filtered error signal and adding the filtered error signal to the second signal to produce an estimate of the lateral acceleration; and
operating the system at least partially based on the estimate.
12. The method of claim 11 wherein the low-pass filter has a cutoff frequency.
13. The method of claim 11 , wherein the system is selected from the group consisting of a fully active suspension system, a semi-active suspension system, an active roll-control system, or a stability control system.
14. The method of claim 11 , wherein the mathematical model is a bicycle model.
15. The method of claim 12 , further comprising varying the cutoff frequency of the low-pass filter as a function of at least one vehicle operating parameter.
16. The method of claim 15 , wherein the at least one vehicle operating parameter is selected from the group consisting of steering rate, steering angle, amount of driver counter steering, and timing of driver counter steering.
17. The method of claim 11 , wherein operating the system includes providing the estimate to a microprocessor-based controller configured to operate the system.
18. A method of operating a microprocessor-based controller of a system in a moving vehicle, the method comprising:
determining a first value of a motion parameter with a sensor on-board the moving vehicle;
determining a second value of the motion parameter with a model of at least a portion of the moving vehicle;
determining a difference between the first value and the second value;
filtering the difference using a low-pass filter; and
based at least partially on the filtered difference, determining an estimated value of a motion parameter.
19. The method of claim 18 , wherein the motion parameter is a lateral acceleration of the moving vehicle.
20. The method of claim 18 , wherein the system is selected from the group consisting of a fully active suspension system, a semi-active suspension system, an active roll-control system, and a stability control system.
21. The method of claim 18 , further comprising setting a value of a filter parameter based on a value of an operating parameter of the moving vehicle.
22. The method of claim 21 , wherein the operating parameter of the moving vehicle is selected from the group consisting of steering rate, steering angle, amount of driver counter steering, and timing of driver counter steering.
23. The method of claim 18 , wherein the moving vehicle is selected from the group consisting of a car, a truck, a van, and a bus.
24. The method of claim 21 , wherein the filter parameter is a cutoff frequency of a low pass filter.