System and method for detecting torque trap in a vehicle drivetrain

A system for detecting whether a vehicle has shifted from a first drive mode to a second drive mode in which fewer axles are driven than in the first drive mode, the system comprising:

• a first drive axle configured to drive a first set of vehicle wheels;
• a second drive axle configured to drive a second set of vehicle wheels;
• a transfer case or power take-off unit including an actuator and a coupling, the coupling being operable in a first state in which the first and second drive axles receive power from the transfer case or power take-off unit and a second state in which only one of the first and second drive axles receive power from the transfer case or power take-off unit, the actuator being configured to move the coupling between the first and second states;
• a first sensor configured to measure a first speed of a first drive axle;
• a second sensor configured to measure a second speed of a second drive axle;
• a third sensor configured to determine a coupling position of the transfer case or power take-off unit;
• and
• a controller in communication with the first, second, and third sensors, and the actuator, the controller configured to:
• operate the actuator;
• determine an actual axle speed difference value based on the measured first speed and the measured second speed;
• determine an expected axle speed difference value based on a vehicle speed and a vehicle torque;
• compare the actual axle speed difference value and the expected axle speed difference value to obtain an error value;
• determine whether the coupling of the transfer case or power take-off unit has moved from the first state to the second state based on the error value;
• and
• generate an output signal in response to the coupling being in the first state.

A method for detecting whether a vehicle has shifted from a first drive mode to a second drive mode in which fewer axles are driven than in the first drive mode, the method comprising:

• measuring, using a first sensor, a first speed of a first drive axle of the vehicle;
• measuring, using a second sensor, a second speed of a second drive axle of the vehicle;
• determining, using a controller, an actual axle speed difference value based on the measured first speed and the measured second speed;
• determining, using the controller, an expected axle speed difference value based on a vehicle speed and a vehicle torque;
• comparing, using the controller, the actual axle speed difference value and the expected axle speed difference value to obtain an error value;
• and
• generating an output signal, using the controller, in response to the error value being above a predetermined threshold value, the output signal configured to generate an alert indicating the vehicle is trapped in the first drive mode.