1. Field of the Invention
The present invention relates to a system and method for road angle estimation.
2. Description of the Related Art
Information related to road angle may be used by vehicular control systems to enhance safety and performance.
Examples of patents and published patent applications that disclose conventional road angle estimation techniques include the following: U.S. Pat. No. 5,446,658, entitled “Method and Apparatus For Estimating Incline and Bank Angles of a Road Surface”; U.S. Pat. No. 6,714,851, entitled “Method For Road Grade/Vehicle Pitch Estimation”; and US Patent Application Publication No. 2006/0276939, entitled “Real-time Determination of Grade and Superelevation Angles of Road.” Examples of non-patent publications that disclose conventional road angle estimation techniques include the following: “Integrating Inertial Sensors With GPS For Vehicle Dynamics Control” by Ryu and Gerdes J. C. and published in the June 2004 issue of “Dynamic Systems, Measurement, and Control”; “Dynamic Estimation of Road Bank Angle” by Tseng H. E. and published in 2001 in “Vehicle System Dynamics”; and “Real-time Identification of Road-bank Angle Using Differential GPS” by Hahn J. O., Rajamani R., You S. H., and Lee K. I. and published in 2004 in “IEEE Transactions on Control Systems Technology.”
However, conventional techniques for estimating road angle, such as those listed above, have some or all of the following disadvantages:
1. Many existing techniques utilize empirical formulas to estimate road angle. However, such methods are imprecise, and are not applicable to a road surface having road angles that vary rapidly and frequently.
2. Existing techniques estimate two road angles separately, and are unable to estimate two road angles simultaneously.
3. Current techniques require the use of four or more sensors for road angle estimation.
4. Road angles defined by conventional techniques are relative to the front of the vehicle, and such a manner of defining road angles is different from traditional Euler angles. Hence, even if two angle values are obtained, road conditions on a global (or terrestrial) reference frame cannot be described sufficiently rapidly.