Method of controlling a vehicle drivetrain and controller in the drivetrain
A method of controlling a vehicle drivetrain by an electric motor, in order to synchronize the speed of an internal combustion engine and the speed of gears in the drivetrain, wherein if a speed synchronization error e sync (t) is controlled to remain within a prespecified region for a specific period of time, the synchronization is finished, and a gear may be engaged.
1. A method of controlling a drivetrain of a vehicle by an electric motor to synchronize a speed of an internal combustion engine and a speed of gears in the drivetrain, comprising:
during an initialization step:
determining an initial speed synchronization error (e sync (0)) based on a difference between an angular speed and a target speed of a starter-generator of the vehicle,
determining a form of a synchronization Performance Function (ρ sync (t)) and a synchronization Maximum Overshoot Parameter (M sync ) wherein the form of the synchronization Performance Function (ρ sync (t)) and the synchronization Maximum Overshoot Parameter (M sync ) define performance limits,
determining a form of Safety Margin functions (σ min(t) ), (σ max(t) ), and
setting a Safety Margin violation flag (SLimViolFlag) to be OFF,
during a synchronization cycle:
determining a speed synchronization error (e sync (t)) at a specific time instance t k ,
determining an actual value of the synchronization Performance Function (ρ sync (t)) at the specific time instance t k ,
determining the Safety Margins (σ min(t) ), (σ max(t) ) at the specific time instance t k ,
determining a transformed synchronization error (ε sync (t)) at the specific time instance t k by way of:
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when the Safety Margin violation flag (SLimViolFlag) is OFF, using the synchronization Performance Function (ρ sync (t)) and the synchronization Maximum Overshoot Parameter (M sync ) by using the synchronization Transformation Function E sync (·),
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if the Safety Margin violation flag (SLimViolFlag) is ON, using a safe Performance Function (ρ sync (t)) and a safe Maximum Overshoot Parameter (M sf ) by using the safe Transformation function E sƒ (·),
when a new target speed (ω tgt ) is requested, interrupt the synchronization process and re-initialize the synchronization cycle (go to the initialization step),
determining a requested motor torque T SG (t) as an output of a Speed Synchronization Controller (SSC):
If |e sync (t)|≤iDisableThres, (T SG (t))=[T PPC (ε sync (t))+T PI (e sync (t)),
If |e sync (t)|>iDisableThres, (T SG (t))=T PPC (ε sync (t))+T P (e sync (t)), where iDisableThres is an integrator disabling error threshold, which determines the condition for the switching between the PI part and P part;
set the requested SG torque T SG (t),
during an End of the synchronization cycle:
when the speed synchronization error e sync (t) remains within a prespecified region for a specific time period Δt, completing the synchronization of the speed of the internal combustion engine and the speed of the gears in the drivetrain.
2. The method of claim 1 , further comprising the steps of engaging gear in the drivetrain when the synchronization is finished.
3. The method of claim 1 , further comprising:
choosing the synchronization Performance Function (ρ sync (t)) the synchronization Maximum Overshoot Parameter (M sync ) and the Safety Margins (σ min(t) ), (σ max(t) ) such that
− M sync ρ sync (0)<−σ min(0) <e sync (0)<σ max(t) <ρ sync (0)), if e sync (0)≥
−ρ sync (0)<−σ max(0) <e sync (0)<σ min(0) <M sync ρ sync (0), if e sync (0)<.
4. The method of claim 1 , wherein the safety margins (σ min(t) ), (σ max(t) ) satisfy the conditions 0<σ min(t) ≤σ max(t) and
− M sync ρ sync ( t )<−σ min(t) <σ max(t) <ρ sync ( t ), ∀ t if e sync (0)≥0
−ρ sync ( t )<−σ max(t) <σ min(t) <M sync ρ sync ( t ), ∀ t if e sync (0)<0.
5. The method of claim 1 , further comprising:
setting the Safety Margin violation flag (SLimViolFlag) to be OFF or remaining OFF when the speed synchronization error e sync (t) lies within the Safety Margins (σ min(t) ) (σ max(t) ), which are within and at a safety distance of the Prescribed Performance Limits, and set to be ON or remaining ON when the speed synchronization error e sync (t) lies on the Safety Margins (σ min(t) ), (σ max(t) ) or surpasses them.
6. The method claim 5 , wherein upon an abrupt speed change, if the speed synchronization error e sync (t) is forced to reach the Safety Margin (σ min(t) ), (σ max(t) ) at a time instance t viol , the Prescribed Performance Limits are expanded with the choice of a safe performance function ρ sƒ (t) and a safe Maximum Overshoot Parameter M sƒ , such that the speed synchronization error e sync (t) continues to evolve within expanded Prescribed Performance Limits.
7. The method of claim 6 , wherein upon a “change-of-mind” situation at the time instance t=t step , the synchronization cycle is interrupted and re-initialized, using a new Performance Function ρ sync ′(t) and a new Maximum Overshoot Parameter M sync ′, which are chosen such that the speed synchronization error e sync (t) continues to evolve within new Prescribed Performance Limits.
8. The method of claim 1 , further comprising:
determining the transformed synchronization error ε sync (t) by the equation
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where the synchronization Transformation Function E sync (·) and the safe Transformation Function E sƒ (·) are smooth, strictly increasing functions.
9. The method according to claim 8 , wherein the steps of the synchronization Transformation Function E sync (·) is defining a bijective mapping:
E sync :(− M sync ,1)→(−∞,∞), if e sync (0)≥0
E sync :(−1, M sync )→(−∞,∞), if e sync (0)<0
and the safe Transformation Function E sƒ (·) is defining a bijective mapping:
E sƒ :(− M sƒ ,1)→(−∞,∞), if e sync (0)≥0
E sƒ :(−1, M sƒ )→(−∞,∞), if e sync (0)<0.
10. The method of claim 1 , further comprising the steps of:
providing speed synchronization controller (SSC);
providing a vehicle having the drivetrain; and
synchronizing the speed of the internal combustion engine and the speed of gears in the drivetrain.
11. The method of claim 10 , further comprising:
providing a Prescribed Performance Control PPC part (T PPC (ε sync (t))); and
calibrating the Prescribed Performance Control PPC part (T ppG (ε sync (t))) to retain the speed synchronization error (e sync (t)) within the Prescribed Performance Limits at all time.
12. The method of claim 10 , further comprising:
providing a switching-PI part T P-PI (e sync (t)), the a switching-PI part T P-PI (e sync (t)) switching between a PI part T PI (e sync (t)) and a P part (T P (e sync (t)) according to whether the speed synchronization error (e sync (t)) is within a specific threshold or not.
13. The method of claim 10 , further comprising:
providing an electronic control unit (ECU), the speed synchronization controller (SSC) being part of the electronic control unit (ECU);
providing a DHT Manager being part of the electronic control unit (ECU);
controlling the vehicle with the electronic control unit (ECU); and
supervising the speed synchronization controller (SSC) with the DHT Manager.
14. The method of claim 13 , further comprising:
providing an internal combustion engine being part of the drivetrain;
providing a gearbox having an output shaft and being part of the drivetrain, the internal combustion engine coupled to the gear box;
providing dog clutches having an input side, the dog clutches being part of the gearbox; and
an electric machine integrated on the input side of the dog clutches in a P0, P1 or P2 configuration;
transferring torque from the internal combustion engine to the output shaft of the gearbox.
15. The method of claim 14 , further comprising:
providing the electric machine to be a Starter-Generator (SG) coupled to a crankshaft of the internal combustion engine.