Road Surface Friction Estimation Using Lateral Force and Slip Angle

The patent introduces lateral force and slip angle as intermediary parameters to estimate road surface friction coefficient. Instead of directly measuring friction coefficient through wheel slippage, the system uses lateral force detecting means and slip angle detecting means to obtain indirect measurements, then calculates the friction coefficient through coordinate transformation and characteristic curve comparison. This intermediary approach allows estimation without requiring actual wheel slippage.

The patent replaces the mechanical slippage-based measurement method with a computational approach. Instead of relying on physical wheel slippage to generate measurable rotational speed changes, the system substitutes a calculation-based method that uses lateral force and slip angle data transformed into coordinate systems, comparing them against pre-stored characteristic curves to determine friction coefficient. This substitution eliminates the requirement for mechanical slippage while maintaining estimation capability.

The patent makes existing vehicle components serve multiple functions. The lateral force detecting means and slip angle detecting means, while adding detection capabilities, are integrated into the existing vehicle control system architecture. These detectors not only provide data for friction coefficient estimation but also contribute to overall vehicle dynamics control, stabilizing systems, and traction control, thereby amortizing the added complexity across multiple functional benefits.

The patent uses pre-stored characteristic curves as reference models that represent the relationship between lateral force, slip angle, and friction coefficient under various conditions. Instead of requiring complex real-time physical modeling, the system copies known characteristic behaviors into lookup tables or stored curves, then compares actual detector readings against these pre-characterized models to rapidly determine friction coefficient. This copying approach simplifies real-time computation while maintaining accuracy.