An apparatus (16) for estimating a grip factor (G) of at least one wheel (2, 3) of a road vehicle (1);
- the apparatus (16) comprising:
- at least one steering factor detecting device (17) physically connected to a steering system (11) of the road vehicle and configured to cyclically detect at least one of the steering parameters comprising an actual rack (RF) force (R) applied to the steering system (11) of the road vehicle (1), which extends from a steering wheel to a suspension (8) of the road vehicle (1);
- detection elements (18) comprising at least one sensor selected from a speed sensor, an inertial measurement unit, and a yaw rate sensor, each physically mounted on the road vehicle (1) and configured to cyclically detect actual vehicle state variables (1);
- a control unit (10) operatively connected to the at least one steering factor detecting device (17) and the detection elements (18), and further configured to receive real-time sensor data and further configured to cyclically process, depending on at least the actual state variables of the vehicle (1), an actual slip angle (α) of said wheel (2, 3) of the road vehicle (1);
- a storage unit (19), within which, in a consultation table (CT), a plurality of grip curves (GC) correlating a plurality of values of the steering parameter comprising the rack force (RF) to a plurality of values of the slip angle (α) are recorded;
- wherein on a same curve, the value of the grip factor (G) remains constant;
- wherein the control unit (10) is configured to cyclically estimate at least one raw value (RG) of the grip factor (G) of the at least one wheel (2, 3) based on the position of a current condition (AC) within the consultation table (CT), as a function of the actual slip angle (α) and the actual rack force (RF);
- wherein the control unit (10) is configured to process a finite value (FV) of the grip factor (G) by filtering the raw value (RG) of the grip factor (G) according to at least one reliability index (Q);
- in particular, the control unit (10) is configured to perform a weighted average of the last n raw values (RG) wherein the weight is given by the reliability index (Q);
- and
- wherein the control unit (10) is further configured to output the estimated grip factor (G) to at least one vehicle control system, and to adjust at least one vehicle control parameter selected from torque delivery, braking force, or suspension damping, based on the estimated grip factor (G), thereby improving the performance and safety of the road vehicle (1).