Tire load estimation system and method

A tire load estimation system comprising:

• at least one tire supporting a vehicle, the at least one tire including a pair of sidewalls extending to a circumferential tread;
• a sensor mounted to the at least one tire;
• a footprint formed by the tread, the footprint including a centerline with a footprint centerline length, wherein the footprint centerline length is measured by the sensor;
• a tire load estimator, the tire load estimator receiving as inputs:
• a pre-calibrated sensitivity;
• the footprint centerline length during straight-line driving conditions;
• a reference footprint value;
• and
• a reference load value;
• a reference footprint generator to determine the reference footprint value for input into the tire load estimator, the reference footprint generator including:
• an unladen state identifier to determine if the vehicle is unladen;
• and
• at least one of a vehicle mileage input and a driving/route severity estimator input to determine an expected change in tire wear, whereby the reference footprint generator determines the reference footprint value when the vehicle is unladen and there is an expected change in tire wear;
• and
• wherein the tire load estimator determines an estimation of tire load and outputs the estimation to at least one of a vehicle control system and a vehicle electronic control unit.

A method for estimating the load of a tire, the method comprising the steps of:

• mounting a sensor to at least one tire supporting a vehicle, wherein the at least one tire includes a pair of sidewalls extending to a circumferential tread, and the tread forms a footprint;
• measuring with the sensor a centerline length of the footprint;
• providing a tire load estimator;
• determining a pre-calibrated sensitivity;
• determining the footprint centerline length during straight-line driving conditions, wherein determining the footprint centerline length during straight-line driving conditions includes:
• selecting measurements of the footprint centerline length during straight-line driving conditions with an event detection module;
• inputting at least one of a steering wheel angle, a yaw rate, a gas pedal position and a brake pedal position into the event detection module;
• analyzing the event detection module input with a filtering module to determine if at least one of a cornering event, an acceleration event and a braking event is taking place;
• and
• excluding selection of measurements of the length of the footprint centerline with the filtering module when at least one of a cornering event, an acceleration event and a braking event is taking place;
• determining a reference footprint value;
• obtaining a reference load value;
• estimating a tire load with the tire load estimator based on the precalibrated sensitivity, the footprint centerline length during straight-line driving conditions, the reference footprint value and the reference load value;
• and
• outputting the estimated tire load to at least one of a vehicle control system and a vehicle electronic control unit.

A method for estimating the load of a tire, the method comprising the steps of:

• mounting a sensor to at least one tire supporting a vehicle, wherein the at least one tire includes a pair of sidewalls extending to a circumferential tread, and the tread forms a footprint;
• measuring with the sensor a centerline length of the footprint;
• providing a tire load estimator;
• determining a pre-calibrated sensitivity;
• determining the footprint centerline length during straight-line driving conditions;
• determining a reference footprint value, wherein determining a reference footprint value includes determining the reference footprint value with a reference footprint generator, the reference footprint generator including:
• an unladen state identifier to determine if the vehicle is unladen, the unladen state identifier receiving as an input at least one of an engagement of seat belts, a level of fluid in a fuel tank and whether a trailer is being hauled;
• and
• at least one of a vehicle mileage input and a driving/route severity estimator input to determine an expected change in tire wear, the driving/route severity estimator input including at least one of a vehicle lateral acceleration and a vehicle longitudinal acceleration, whereby the reference footprint generator determines the reference footprint value when the vehicle is unladen and there is an expected change in tire wear;
• obtaining a reference load value;
• estimating a tire load with the tire load estimator based on the precalibrated sensitivity, the footprint centerline length during straight-line driving conditions, the reference footprint value and the reference load value;
• and
• outputting the estimated tire load to at least one of a vehicle control system and a vehicle electronic control unit.