Diagnostic and control method for clutches in a vehicle system

1. A method for operation of a vehicle system, comprising:

at a diagnostic controller or processing unit independent from a driveline controller or processing unit, respectively, determining an engagement state of a first clutch in a transmission of the vehicle system, wherein the engagement state is selected from a group of three or more clutch engagement states;

identifying an unauthorized clutch state based on the engagement state of the first clutch and a speed of the vehicle; and

responsive to the identification of the unauthorized clutch state, operating the vehicle system in a fault state.

2. The method of claim 1 , wherein the three or more clutch engagement states include an engaged state, an intermediate state occurring during a shifting transient, and a disengaged state.

3. The method of claim 2 , wherein:

the engaged state, the intermediate state, and the disengaged state each are delineated by a lower pressure threshold and a higher pressure threshold;

the disengaged state is identified when a clutch pressure is below the lower pressure threshold;

the engaged state is identified when the clutch pressure is above the higher pressure threshold; and

the intermediate state is identified when the clutch pressure is above the lower pressure threshold and below the higher pressure threshold.

4. The method of claim 1 , wherein the engagement state of the first clutch is determined based on a pressure applied to the first clutch and/or a drive current provided to an actuator of the first clutch.

5. The method of claim 1 , wherein identifying the unauthorized clutch state includes:

comparing the engagement state of the first clutch against an engagement state of a second clutch; and

determining that the first clutch and the second clutch are opposite clutches in unauthorized engagement states.

6. The method of claim 5 , wherein the vehicle system is operated in the fault state in response to a duration of the unauthorized clutch state exceeding a fault tolerant time.

7. The method of claim 6 , wherein the fault tolerant time is variable.

8. The method of claim 6 , wherein the vehicle system is operated in the fault state in response to the vehicle speed exceeding a threshold speed.

9. The method of claim 1 , wherein the first clutch is a directional clutch, a gear clutch, or a range clutch.

10. A vehicle system, comprising:

a transmission including a plurality of clutches configured to selectively engage and disengage to shift between a plurality of discrete gear ratios;

a diagnostic controller or processing unit including:

instructions that, when executed, cause the diagnostic controller or processing unit to:

determine an engagement state of each of a plurality of clutches, wherein each of the engagement states are selected from a group of engagement states that include an engaged state, an intermediate state, and a disengaged state; and

operate the vehicle system in a fault state based on a comparison of the engagement states of the plurality of clutches.

11. The vehicle system of claim 10 , wherein the intermediate state is associated with a shifting transient.

12. The vehicle system of claim 10 , wherein the plurality of clutches include one or more range clutches, one or more gear clutches, and one or more directional clutches.

13. The vehicle system of claim 10 , wherein operating the vehicle system in the fault state includes disengaging the plurality of clutches.

14. The vehicle system of claim 10 , wherein the vehicle system is operated in the fault state when a vehicle speed exceeds a threshold speed.

15. The vehicle system of claim 14 , wherein the vehicle system is operated in the fault state when a duration of an unauthorized clutch state exceeds a fault tolerant time.

16. A method for operation of a driveline system, comprising:

at a diagnostic controller independent from a driveline controller, determining a vehicle speed;

determining an engagement state of each of a first clutch and a second clutch in a transmission based on a pressure or current associated with each of the first clutch and the second clutch, wherein the engagement state of each clutch is selected from a group of three or more clutch engagement states that includes an engaged state, an intermediate state, and a disengaged state;

identifying an unauthorized clutch state based on a comparison between the engagement states of the first and second clutches and a set of unauthorized clutch states; and

responsive to the identification of the unauthorized clutch state and the vehicle speed exceeding a threshold speed, operating the first clutch and the second clutch in a fault state.

17. The method of claim 16 , wherein the intermediate state occurs during a shifting transient.

18. The method of claim 16 , wherein the unauthorized clutch state includes an engaged or intermediate state of both of the first and second clutches.

19. The method of claim 18 , wherein the first and second clutches are gear clutches.

20. The method of claim 18 , wherein the first and second clutches are directional clutches or range clutches.