Control of electric motor

1. A method performed by an electronic control unit in a vehicle for controlling an electric machine during a synchronisation procedure of a first shaft and a second shaft, whereby said first shaft is in drive connection with an output shaft of said electric machine and said first shaft and said second shaft are connectable over a synchronisation mechanism, comprising:

controlling, by the electronic control unit, the output shaft to an actual speed close to a target speed of said second shaft by using speed control;

continuously controlling, by the electronic control unit, an electrical torque of said electric machine, such that a torque on said output shaft becomes essentially equal to zero during the synchronisation procedure of the synchronisation mechanism; and

controlling, by the electronic control unit, said synchronisation mechanism to synchronise the speed of the first shaft and the second shaft.

2. The method according to claim 1 , further comprising:

continuously measuring an actual speed of the first shaft,

wherein controlling the electrical torque of said electrical machine is performed dependent on any changes of said actual speed of said first shaft.

3. The method according to claim 1 , further comprising:

continuously measuring a position of said synchronising mechanism, an actual speed of said first shaft, and an actual speed of said second shaft; and

controlling the output torque of said electrical machine when said synchronisation mechanism reaches a predetermined position,

wherein said output torque of said electrical machine is dependent on a difference between said actual speed of said first shaft and an actual speed of said second shaft.

4. The method according to claim 3 , wherein said output torque is based on said difference in actual speed between the first and the second shaft.

5. A vehicle comprising:

a transmission having an input shaft and a second shaft,

wherein the input shaft and the second shaft are connected by a synchronisation mechanism;

an electrical machine having an output shaft,

wherein said input shaft of the transmission is connected to said output shaft of said electrical machine;

at least one gear allocated to said input shaft, wherein said gear is synchronised with the synchronising mechanism; and

an electronic control unit for controlling the electrical machine during a synchronising procedure of the input shaft and the second shaft,

wherein the electrical control unit is configured to:

control the output shaft to an actual speed close to a target speed of said second shaft by using speed control;

continuously control an electrical torque of said electrical machine, such that a torque on said output shaft of said electrical machine becomes essentially equal to zero during the synchronisation procedure of the synchronisation mechanism; and

control said synchronisation mechanism to synchronise the speed of the input shaft and the second shaft.

6. The vehicle according to claim 5 , wherein said transmission is a dual-clutch multi speed transmission and said input shaft is one of a first and a second input shaft and a plurality of gears are allocated to said input shaft.

7. A non-transitory computer readable medium storing a computer program comprising program code for controlling an electric machine during a synchronisation procedure of a first shaft and a second shaft, whereby said first shaft is in drive connection with an output shaft of said electric machine and said first shaft and said second shaft are connectable over a synchronisation mechanism, the program code, when executed by at least one processor of a device, causes the device to:

control the output shaft to an actual speed close to a target speed of said second shaft by using speed control;

continuously control an electrical torque of said electric machine, such that a torque on said output shaft becomes essentially equal to zero during the synchronisation procedure of the synchronisation mechanism; and

control said synchronisation mechanism to synchronise the speed of the first shaft and the second shaft.