Method and system for gear engagement

A method for motion control of a shift sleeve in a stepped gear transmission during a synchronisation and gear engagement sequence for avoiding gear teeth interference, wherein the stepped gear transmission comprises an axially displaceable shift sleeve arranged on and rotationally secured to a shaft, and a constant mesh gear wheel arranged on and rotatable relative to said shaft, the method comprising:

• receiving a gear shift command,
• determining a target relative displacement between the sleeve teeth and gear teeth for a state when a gear wheel rotational speed reaches a shift sleeve rotational speed at the end of a synchronisation phase, which target relative displacement is determined for avoiding impact between sleeve teeth and gear teeth during a following gear engagement phase,
• determining a starting relative displacement between the sleeve teeth and gear teeth that causes the shift sleeve and gear wheel to reach said target relative displacement simultaneously with said rotational speed difference becomes zero at the end of the synchronisation phase when applying a synchronisation torque from the start to the end of the synchronisation phase,
• starting to apply said synchronisation torque when the real relative displacement reaches said starting relative displacement.

A control system for motion control of a shift sleeve in a stepped gear transmission during a synchronisation and gear engagement sequence for avoiding gear teeth interference, wherein the stepped gear transmission comprises an axially displaceable shift sleeve arranged on and rotationally secured to a shaft, and a constant mesh gear wheel arranged on and rotatable relative to said shaft, the control system being configured for performing the following steps:

• receiving a gear shift command,
• determining a target relative displacement between the sleeve teeth and gear teeth for a state when a gear wheel rotational speed reaches a shift sleeve rotational speed at an end of a synchronisation phase, which target relative displacement is determined for avoiding impact between sleeve teeth and gear teeth during a following gear engagement phase,
• determining a first phase plane trajectory defining a relationship between a rotational speed difference between the shift sleeve and the gear wheel and a relative displacement between the sleeve teeth and gear teeth, wherein the relative displacement according to the first phase plane trajectory equals the target relative displacement when said rotational speed difference becomes zero at the end of the synchronisation phase,
• determining a second phase plane trajectory defining the relationship between the rotational speed difference between the shift sleeve and the gear wheel and the relative displacement between the sleeve teeth and gear teeth, wherein the relative displacement according to the second phase plane trajectory equals the target relative displacement when said rotational speed difference becomes zero at the end of the synchronisation phase,
• applying a synchronisation torque,
• controlling said synchronisation torque for keeping a real relative displacement between the sleeve teeth and gear teeth within boundaries of the first and second phase plane trajectories for any rotational speed difference, such that the real relative displacement between the sleeve teeth and gear teeth reaches said target relative displacement simultaneously with said rotational speed difference becomes zero at the end of the synchronisation phase.