Detecting and distinguishing between stuck and failed rack in steering systems for vehicles

A system comprising:

• one or more steering sensors of a vehicle configured to obtain steering sensor data pertaining to a steering system of the vehicle, the steering system comprising a motor and a rack;
• and
• a processor that is coupled to the one or more steering sensors and that is configured to at least facilitate:
• determining an estimated electric current of the motor based on the steering sensor data;
• comparing the estimated electric current with a predetermined electric current threshold;
• and
• determining a condition of the steering system of the vehicle, including whether movement of the vehicle is inhibited and whether the rack has a failure, based on whether the estimated electric current is greater than or equal to the predetermined electric current threshold;
• wherein the processor is further configured to determine the estimated electric current of the motor by:
• using an observer to estimate a motor angle for a road wheel actuator (RWA) motor and current by integrating a prediction model for the RWA motor and a measurement model for observations, along with use of a Kalman filter;
• modeling the motor as a direct current (DC) permanent magnet motor, and by modeling electrical properties of the motor as a series connection of a resistor, an inductor, and a voltage source that represents back-EMF produced by the motor, and further including a relationship between a hand wheel actuator (HWA) requested rack displacement and a resulting RWA road wheel angle;
• and
• utilizing pinion angle sensor measurements and rack force estimations received from an actuator and determining the current based on the rack force using a mathematical model that represents an interaction between the rack and pinion, along with an electrical model that represents the interaction between motor torque and current.

A vehicle comprising:

• a steering system comprising a steer-by-wire steering system having a rack as well as a feedback motor coupled to a steering wheel of the vehicle and a road wheel actuator (RWA) motor coupled to a road wheel of the vehicle;
• and
• one or more steering sensors of the vehicle configured to obtain steering sensor data pertaining to the steering system of the vehicle;
• one or more cameras of the vehicle configured to obtain camera data as to one or more external objects that are in proximity to the vehicle;
• and
• a processor that is coupled to the one or more steering sensors and to the one or more cameras and that is configured to at least facilitate:
• determining an estimated electric current of the RWA motor based on the steering sensor data;
• comparing the estimated electric current with a predetermined electric current threshold;
• and
• determining a condition of the steering system of the vehicle, including whether movement of the vehicle is inhibited and whether the rack has a failure, based on whether the estimated electric current is greater than or equal to the predetermined electric current threshold;
• wherein the processor is coupled to the one or more cameras and is further configured to at least facilitate:
• determining that the condition comprises an operational condition in which the steering system is operating correctly, when the estimated electric current is less than the predetermined electric current threshold;
• determining that the condition comprises a rack failure condition in which a mechanical failure is present for the rack, when both of the following conditions are satisfied:
• the estimated electric current is greater than or equal to the predetermined electric current threshold;
• and
• the camera data does not show any external objects that are deemed to be inhibiting movement of the vehicle;
• and
• determining that the condition comprises a rack stuck condition in which the rack is deemed to be stuck by the one or more external objects, when both of the following conditions are satisfied:
• the estimated electric current is greater than or equal to the predetermined electric current threshold;
• and
• the camera shows an external object that is deemed to be inhibiting movement of the vehicle;
• wherein the processor is further configured to at least facilitate:
• providing a service instruction for a driver of the vehicle, via instructions provide by the processor, to obtain repair of the steering system when the condition comprises the rack failure condition;
• and
• providing a steering action instruction for the driver of the vehicle, via the instructions provide by the processor, when the condition comprises the rack stuck condition;
• and
• wherein the processor is further configured to determine the estimated electric current of the motor by:
• using an observer to estimate a motor angle for the RWA motor and current by integrating a prediction model for the RWA motor and a measurement model for observations, along with use of a Kalman filter;
• modeling the motor as a direct current (DC) permanent magnet motor, and by modeling electrical properties of the motor as a series connection of a resistor, an inductor, and a voltage source that represents back-EMF produced by the motor, and further including a relationship between a hand wheel actuator (HWA) requested rack displacement and a resulting RWA road wheel angle;
• utilizing pinion angle sensor measurements and rack force estimations received from an actuator and determining the current based on the rack force using a mathematical model that represents an interaction between the rack and pinion, along with an electrical model that represents the interaction between motor torque and current;
• and
• utilizing the Kalman filter in estimating an angle of the motor along with the current of the motor utilizing a requested disk replacement (drag), a motor voltage (Vm), a pinion angle (P), and rack force (Fr), and utilizing multiple predictions of the current at different points in time and using a motion model as well as measurements of the current using an observation model, along with a time delay for the Kalman filter.