Torque management techniques for engine systems having belt-driven starter generators
View Patent ↗A method can include determining a desired torque output from an engine system in response to a torque request, the engine system including an engine and a belt-driven starter generator (BSG). The method can include determining a current engine torque capacity. When the desired torque output is greater than the current engine torque capacity, the method can include (i) determining a maximum engine torque capacity, (ii) determining a current BSG torque capacity, (iii) commanding the BSG to operate as a torque generator or a torque consumer based on a difference between the desired torque output and the maximum engine torque capacity and a state of a battery system configured to power the BSG, and (iv) controlling the engine and the BSG to collectively generate the desired torque output at a flywheel of the engine.
1. A method, comprising:
determining, at a controller for an engine system comprising an engine, the controller having one or more processors, a desired torque output from the engine system in response to a torque request, wherein the engine is configured to generate torque at a flywheel, and wherein the engine system includes a belt-driven starter generator (BSG) coupled to the flywheel by a belt and an absence of a variable tensioner;
determining, at the controller, a current engine torque capacity; and
when the desired torque output is greater than the current engine torque capacity:
(i) determining, at the controller, a maximum engine torque capacity;
(ii) determining, at the controller, a current BSG torque capacity;
(iii) commanding, by the controller, the BSG to continuously operate as either a torque generator or a torque consumer while the engine is running based on a difference between the desired torque output and the maximum engine torque capacity and a state of a battery system configured to power the BSG;
(iv) maintaining, by the controller, a desired minimum tension on the belt without requiring the variable tensioner by continuously operating the BSG as either the torque generator or the torque consumer while the engine is running; and
(v) controlling, by the controller, the engine and the BSG to collectively generate the desired torque output at the flywheel of the engine.
2. The method of claim 1 , further comprising:
controlling, by the controller, the engine to generate a sum of (i) the desired torque output and (ii) a portion of the current BSG torque capacity at the flywheel of the engine when the BSG is commanded to operate as the torque consumer, wherein the BSG is configured to consume the portion of the current BSG torque capacity generated at the flywheel; and
controlling, by the controller, the engine to generate a difference between (i) the desired torque output and (ii) the portion of the current BSG torque capacity when the BSG is commanded to operate as a torque generator, wherein the BSG is configured to generate the portion of the current BSG torque capacity at the flywheel.
3. The method of claim 2 , wherein the BSG includes an electric motor configured to generate the portion of the current BSG torque capacity at the flywheel using a current from the battery system while the BSG is operating as a torque generator.
4. The method of claim 3 , wherein commanding the BSG to operate as a torque generator includes controlling, by the controller, the BSG according to a duty cycle, wherein the duty cycle is based on (i) the portion of the current BSG torque capacity generated by the BSG at the flywheel and (ii) a rotational speed of the BSG.
5. The method of claim 3 , wherein the BSG further includes an alternator configured to generate a current recharge the battery system using the portion of the current BSG torque capacity consumed by the electric motor while the BSG is operating as a torque consumer.
6. The method of claim 2 , further comprising calculating, at the controller, the portion of the current BSG torque capacity based on a product of (i) a coefficient and (ii) the current BSG torque capacity, wherein the coefficient is a value between zero and one.
7. The method of claim 6 , wherein the coefficient is approximately 0.5 to provide an optimal response time by the BSG when an expected magnitude of the desired engine torque is unknown.
8. The method of claim 7 , wherein the coefficient of approximately 0.5 causes the BSG to switch less frequently between operating as a torque generator and a torque consumer to eliminate response delays due to an inherent elasticity of the belt.
9. The method of claim 6 , wherein:
the coefficient is greater than but approximately equal to zero when (i) the desired torque output is expected to be greater than the current engine torque capacity and the BSG is operating as a torque generator, or (ii) the desired torque output is expected to be less than the current engine torque capacity and the BSG is operating as a torque consumer; and
the coefficient is equal to or approximately equal to one when (i) the desired torque output is expected to be less than the current engine torque capacity to maintain at least a desired minimal tension of the belt and the BSG is operating as a torque generator, or (ii) the desired torque output is expected to be greater than the current engine torque capacity to maintain at least the desired minimal tension of the belt and the BSG is operating as a torque consumer.
10. The method of claim 1 , further comprising controlling, by the controller, the engine to generate the desired torque output at the flywheel when the desired torque output is less than or equal to the current engine torque capacity.
11. An engine system, comprising:
an internal combustion engine configured to generate torque at a flywheel in response to a torque request, the torque request indicating a desired torque output of the engine system;
a belt-driven starter generator (BSG) coupled to the flywheel by a belt and configured to continuously operate as either a torque generator or a torque consumer while the engine is running to maintain a desired minimum tension on the belt such that the BSG is not associated with a variable tensioner configured to maintain the desired minimum tension on the belt; and
a controller configured to:
determine a current engine torque capacity; and
when the desired torque output is greater than the current engine torque capacity:
(i) determine a maximum engine torque capacity;
(ii) determine a current BSG torque capacity;
(iii) command the BSG to operate as the torque generator or the torque consumer based on a difference between the desired torque output and the maximum engine torque capacity and a state of a battery system configured to power the BSG; and
(iv) control the engine and the BSG to collectively generate the desired torque output at the flywheel of the engine.
12. The engine system of claim 11 , wherein the controller is further configured to:
control the engine to generate a sum of (i) the desired torque output and (ii) a portion of the current BSG torque capacity at the flywheel of the engine when the BSG is commanded to operate as the torque consumer, wherein the BSG is configured to consume the portion of the current BSG torque capacity generated at the flywheel; and
control the engine to generate a difference between (i) the desired torque output and (ii) the portion of the current BSG torque capacity when the BSG is commanded to operate as a torque generator, wherein the BSG is configured to generate the portion of the current BSG torque capacity at the flywheel.
13. The engine system of claim 12 , wherein the BSG includes an electric motor configured to generate the portion of the current BSG torque capacity at the flywheel using a current from the battery system while the BSG is operating as a torque generator.
14. The engine system of claim 13 , wherein the controller is configured to command the BSG to operate as a torque generator by controlling the BSG according to a duty cycle, wherein the duty cycle is based on (i) the portion of the current BSG torque capacity generated by the BSG at the flywheel and (ii) a rotational speed of the BSG.
15. The engine system of claim 13 , wherein the BSG further includes an alternator configured to generate a current recharge the battery system using the portion of the current BSG torque capacity consumed by the electric motor while the BSG is operating as a torque consumer.
16. The engine system of claim 12 , wherein the controller is further configured to calculate the portion of the current BSG torque capacity based on a product of (i) a coefficient and (ii) the current BSG torque capacity, wherein the coefficient is a value between zero and one.
17. The engine system of claim 16 , wherein the coefficient is approximately 0.5 to provide an optimal response time by the BSG when an expected magnitude of the desired engine torque is unknown.
18. The engine system of claim 17 , wherein the coefficient of approximately 0.5 causes the BSG to switch less frequently between operating as a torque generator and a torque consumer to eliminate response delays due to an inherent elasticity of the belt.
19. The engine system of claim 16 , wherein:
the coefficient is greater than but approximately equal to zero when (i) the desired torque output is expected to be greater than the current engine torque capacity and the BSG is operating as a torque generator, or (ii) the desired torque output is expected to be less than the current engine torque capacity and the BSG is operating as a torque consumer; and
the coefficient is equal to or approximately equal to one when (i) the desired torque output is expected to be less than the current engine torque capacity to maintain at least a desired minimal tension of the belt and the BSG is operating as a torque generator, or (ii) the desired torque output is expected to be greater than the current engine torque capacity to maintain at least the desired minimal tension of the belt and the BSG is operating as a torque consumer.
20. The engine system of claim 11 , wherein the controller is further configured to control the engine to generate the desired torque output at the flywheel when the desired torque output is less than or equal to the current engine torque capacity.