Brake-to-Steer lateral stability management based on stability indicator correlation
A number of variations are disclosed including a system and method for modifying, in real-time, at least one brake or powertrain application to individual roadwheels of a vehicle to increase lateral maneuver capability in a vehicle having an operational, partially operational, failing, or failed electronic steering system. The system and method may include modifying at least one brake or powertrain command to individual roadwheels where vehicle instability is detected.
1 . A computer readable medium comprising:
non-transitory memory having instructions stored thereon executable by an electronic processor, the instructions when executed by the electronic processor implement the following functions comprising:
receiving or calculating at least one stability indicator wherein the received at least one stability indicator comprises at least one of vehicle speed, lateral acceleration, vehicle yaw rate, steering wheel angle, steering wheel torque, speed, wheel speed, yaw rate, or wheel slip ratios, and wherein the calculating at least one stability indicator comprises calculating a yaw rate;
calculating an estimated yaw rate based on at least one of vehicle speed, wheel speed or lateral acceleration;
calculating a yaw rate error based on at least one of the estimated yaw rate or measured vehicle yaw rate;
determining a brake command modifier value based on at least one of measured vehicle speed or the yaw rate error;
modifying at least one brake command based on the brake command modifier value to provide a modified brake command;
communicating the modified brake command to a brake-to-steer system to mitigate lateral instability and unintended vehicle oversteer.
2 . A computer readable medium as in claim 1 , further comprising determining a modified powertrain modifier value based on at least one of measured vehicle speed or the yaw rate error; and modifying at least one powertrain command based on the powertrain command modifier value wherein the powertrain command modification is performed concurrently with brake command modification to maintain overall lateral stability.
3 . A computer readable medium as in claim 2 , wherein the powertrain command modifier value is a scalar value adjusted proportionately to differential wheel slip measurements between left and right wheels.
4 . A computer readable medium as in claim 2 , wherein the powertrain command modifier value is a reduction value that decreases applied to work to minimize lateral instability.
5 . A computer readable medium as in claim 1 , wherein the brake command modifier value is a scalar value calculated dynamically based upon the magnitude and direction of the rate error.
6 . A computer readable medium as in claim 1 , wherein the brake command modifier value is a reduction value calculated when the yaw rate error exceeds a defined stability threshold in a direction indicating oversteer.
7 . A computer readable medium as in claim 1 , wherein determining a brake command modifier value based on at least one of measured vehicle speed or the yaw rate error comprises utilizing at least one of: a two-dimensional yaw rate error versus speed table; a one-dimensional yaw rate error table;
a single yaw rate error value; a two-dimensional yaw rate error verses wheel speed table; a two-dimensional yaw rate error verses yaw rate table; a three-dimensional table of yaw rate error, yaw rate, wheel speeds; or other numeric calculations derived from real-time sensor feedback from individual vehicle wheels.
8 . A computer readable medium as in claim 1 , further comprising communicating Brake-to-Steer commands in a pre-scaled state to a Brake-to-Steer command modifier prior to modifying at least one brake command based on the brake command modifier value wherein pre-scaled commands are derived from driver or autonomous system intended steering inputs.
9 . A computer program product comprising instructions executable by an electronic processor to carry out actions, comprising:
determining that a steering maneuver is underway in a vehicle;
receiving vehicle data comprising at least one of vehicle feedback information or actuator feedback information;
calculating a stability indicator threshold;
calculating a stability indicator, wherein the stability indicator includes at least one of a yaw rate error or a differential wheel slip;
determining a difference between the stability indicator and the stability indicator threshold;
comparing the stability indicator threshold and the stability indicator; and
based on the comparison generating at least one alteration to a Brake-to-Steer actuator command by scaling, reducing, or adjusting the Brake-to-Steer actuator command.
10 . A computer readable medium as in claim 9 , further comprising determining a modified Brake-to-Steer command modifier value based on the comparison, and wherein the generating at least one alteration to a Brake-to-Steer actuator command is based on the Brake-to-Steer command modifier value, applied only when the stability indicator exceeds a dynamic threshold range configured for current road surface conditions.
11 . A computer readable medium as in claim 10 , wherein the brake command modifier value is a scalar value.
12 . A computer readable medium as in claim 10 , wherein the brake command modifier value is a reduction value.
13 . A computer readable medium as in claim 10 , wherein determining a brake command modifier value based on the comparison comprises utilizing at least one of: a two-dimensional yaw rate error versus speed table; a one-dimensional yaw rate error table; a single yaw rate error value; a two-dimensional yaw rate error verses wheel speed table; a two-dimensional yaw rate error verses yaw rate table; a three-dimensional table of yaw rate error, yaw rate, wheel speeds; or other numeric calculations updated adaptively during vehicle operation.
14 . A computer program product as set forth in claim 9 further comprising based on the comparison generating at least one alteration to a powertrain command, wherein the alteration is configured to induce compensatory yaw moment via torque veectoring.
15 . A computer readable medium as in claim 14 , further comprising determining a modified powertrain modifier value based on the comparison, and wherein the generating at least one alteration to a powertrain command is based on powertrain command modifier value in response to vehicle lateral acceleration and wheel slip imbalance.
16 . A computer readable medium as in claim 15 , wherein the powertrain command modifier value is a scalar value.
17 . A computer readable medium as in claim 15 , wherein the powertrain command modifier value is a reduction value.
18 . A computer readable medium as in claim 9 , further comprising communicating Brake-to-Steer commands in a pre-scaled state to a Brake-to-Steer command modifier prior to modifying at least one brake command based on the brake command modifier value, wherein said modifier operates in real-time during steering system failure conditions.