Method of controlling a synchronizer actuator fork of a transmission

1. A method of controlling a transmission including a shaft, the shaft having a synchronizer and a gear mounted thereon, the method comprising:

moving, at a pre-synchronization fork velocity, an actuator fork of the synchronizer in a gear engagement direction, through a pre-synchronization phase of a synchronization event;

wherein:

the synchronization event includes the pre-synchronization phase and a synchronization phase;

movement of the actuator fork is controlled by an actuator including an actuator piston;

the actuator is operatively connected to the actuator fork and actuable to move the actuator fork in the gear engagement direction by applying a fluid pressure to the actuator piston at an applied fluid pressure level;

the applied fluid pressure is commanded by a controller in communication with the actuator; and

the pre-synchronization fork velocity is defined by the applied fluid pressure level;

determining, via the controller, the pre-synchronization fork velocity;

comparing, via the controller, the pre-synchronization fork velocity to a fork velocity target; and

adjusting, via the controller, the applied fluid pressure level when the pre-synchronization fork velocity and the velocity target are not equal.

2. The method of claim 1 , further comprising:

comparing, via the controller, the pre-synchronization fork velocity to a predetermined range defined by the velocity target;

maintaining the applied fluid pressure level when the pre-synchronization fork velocity is within the predetermined range; and

adjusting the applied fluid pressure level when the pre-synchronization fork velocity is outside of the predetermined range.

3. The method of claim 2 , further comprising:

adjusting the applied fluid pressure level by a predetermined amount when the pre-synchronization fork velocity is outside the predetermined range;

wherein the predetermined amount is defined by the difference between the pre-synchronization fork velocity and the velocity target.

4. The method of claim 1 , further comprising:

selecting, via the controller, a look-up table;

wherein the look-up table provides a predetermined amount to adjust the applied fluid pressure according to the difference between the pre-synchronization fork velocity and the velocity target; and

determining the predetermined amount to adjust the applied fluid pressure from the look-up table.

5. The method of claim 1 , further comprising:

commanding, via the controller, a shift including the synchronization event;

wherein:

the commanded shift is characterized by a shift type;

the shift type is one of a plurality of shift types executable by the transmission; and

the velocity target is defined by the shift type.

6. The method of claim 5 , further comprising:

selecting, via the controller, a look-up table from a plurality of look-up tables, each corresponding to a respective one of the plurality of shift types;

wherein the selected look-up table corresponds to the shift type of the commanded shift and provides a predetermined amount to adjust the applied fluid pressure according to the difference between the pre-synchronization fork velocity and the velocity; and

determining the predetermined amount to adjust the applied fluid pressure from the selected look-up table.

7. The method of claim 1 , wherein:

moving the actuator fork through a pre-synchronization phase comprises moving the actuator fork in the gear engagement direction from a first fork position to a second fork position;

the method further comprising:

sensing, via the at least one fork position sensor in communication with the controller, the actuator fork at the first fork position at a first time;

outputting a first signal to the controller at the first time;

sensing, via at least one fork position sensor, the actuator fork at the second fork position; and

outputting a second signal to the controller at the second time.

8. The method of claim 7 , further comprising:

determining the pre-synchronization fork velocity using the first and second fork positions and the first and second times.

9. The method of claim 7 , further comprising:

time stamping, via the controller, the first signal with a first time stamp;

time stamping, via the controller, the second signal with a second time stamp; and

determining the pre-synchronization fork velocity using the first and second fork positions and the first and second time stamps.

10. The method of claim 9 , further comprising:

storing the first and second timestamps to a memory in communication with the controller.

11. The method of claim 7 , wherein:

the actuator fork is operatively attached to a synchronizer sleeve; and

the first position is defined by a neutral position of the actuator fork relative to the synchronizer sleeve.

12. The method of claim 7 , further comprising:

monitoring, via the controller, synchronizer slip of the synchronizer during the synchronization event;

wherein during the pre-synchronization phase the synchronizer slip is characterized by a first rate of slip and a second rate of slip; and

wherein the second fork position is defined by a change in the rate of synchronizer slip from the first rate to the second rate.

13. A method of controlling a transmission including a shaft, the shaft having a synchronizer and a gear mounted thereon, the method comprising:

commanding, via a controller, application of a fluid pressure at an applied fluid pressure level to an actuator piston of an actuator;

applying the fluid pressure to the actuator piston at the applied fluid pressure level to move an actuator fork operatively connected to the actuator in a gear engagement direction from a first pre-synchronization position to a second pre-synchronization position;

wherein the actuator fork is moved from the first pre-synchronization position to the second pre-synchronization position at a pre-synchronization fork velocity defined by the applied fluid pressure level;

measuring an elapsed time to move the actuator fork from the first pre-synchronization position to the second pre-synchronization position;

determining the pre-synchronization fork velocity of the fork using the first and second pre-synchronization positions and the elapsed time;

comparing, via the controller, the pre-synchronization fork velocity to a fork velocity target; and

adjusting, via the controller, the applied fluid pressure level when the pre-synchronization fork velocity and the velocity target are not equal.

14. The method of claim 1 , further comprising:

comparing, via the controller, the pre-synchronization fork velocity to a predetermined range defined by the velocity target;

maintaining the applied fluid pressure level when the pre-synchronization fork velocity is within the predetermined range; and

adjusting the applied fluid pressure level by a predetermined amount when the pre-synchronization fork velocity is outside of the predetermined range;

wherein the predetermined amount is defined by the difference between the pre-synchronization fork velocity and the velocity target.

15. The method of claim 13 , further comprising:

sensing, via at least one fork position sensor in communication with the controller, the actuator fork at the first fork position at a first time;

sensing, via at least one fork position sensor, the actuator fork at the second fork position; and

determining the elapsed time using the first and second times.

16. The method of claim 13 , further comprising:

outputting, via at least one fork position sensor in communication with the controller, a first signal to the controller when the at least one fork position sensor senses the actuator fork at the first fork position;

time stamping, via the controller, the first signal with a first time stamp;

outputting, via the at least one fork position sensor in communication with the controller, a second signal to the controller when the at least one fork position sensor senses the actuator fork at the second fork position;

time stamping, via the controller, the second signal with a second time stamp; and

determining the pre-synchronization fork velocity using the first and second fork positions and the first and second time stamps.

17. The method of claim 13 , further comprising:

commanding, via the controller, a shift including a synchronization event;

wherein:

the commanded shift is characterized by a shift type;

the shift type is one of a plurality of shift types executable by the transmission; and

the velocity target is defined by the shift type.

18. A system for controlling a transmission including a shaft, the shaft having a synchronizer and a gear mounted thereon, the system comprising:

a controller programmed to move an actuator fork of the synchronizer in a gear engagement direction through a pre-synchronization phase of a synchronization event at a pre-synchronization fork velocity;

an actuator piston operatively connected to the actuator fork and actuable by a fluid applied to the actuator piston at an applied fluid pressure level;

wherein:

the actuator piston is actuable to move the fork axially relative to an axis defined by the shaft;

during axial movement of the fork by the actuator piston, the pre-synchronization fork velocity is defined by the applied fluid pressure level; and

the controller is operable to adjust the applied fluid pressure level to control the pre-synchronization fork velocity of the actuator fork during the pre-synchronization phase within a predetermined range defined by a velocity target.

19. The system of claim 18 , wherein the controller is operable to:

sense movement of the actuator fork from a first fork position to a second fork position during the pre-synchronization phase;

determine an elapsed time to move the actuator fork from the first position to the second position;

determine the pre-synchronization fork velocity using the first and second fork positions and the elapsed time; and

adjust the applied fluid pressure level when the pre-synchronization fork velocity is outside the predetermined range.

20. The system of claim 18 , wherein the controller is operable to:

command a shift including the synchronization event;

wherein:

the commanded shift is characterized by a shift type;

the shift type is one of a plurality of shift types executable by the transmission; and

the velocity target is defined by the shift type.