System and method for estimating a clutch torque of an electronic limited slip differential and tire longitudinal forces
A system includes a clutch state module and a clutch torque module. The clutch state module is configured to determine whether a clutch of an electronic limited slip differential is locked or unlocked. The electronic limited slip differential couples an engine of a vehicle to left and right wheels of the vehicle. The clutch torque module is configured to estimate an actual torque transferred by the clutch using a first clutch torque model when the electronic limited slip differential is unlocked, and estimate the actual clutch torque using a second clutch torque model when the electronic limited slip differential is locked. The second clutch torque model is different than the first clutch torque model.
1. A system comprising:
a clutch state module of a vehicle and configured to determine whether a clutch of an electronic limited slip differential is locked or unlocked, the electronic limited slip differential coupling an engine of a vehicle to left and right wheels of the vehicle; and
a clutch torque module of the vehicle and configured to:
estimate an actual torque transferred by the clutch using a first clutch torque model when the electronic limited slip differential is unlocked; and
estimate the actual clutch torque using a second clutch torque model when the electronic limited slip differential is locked, wherein the second clutch torque model is different than the first clutch torque model.
2. The system of claim 1 wherein the first clutch torque model includes a hyperbolic tangent function.
3. The system of claim 2 wherein the hyperbolic tangent function is a function of a difference between speeds of the left and right wheels.
4. The system of claim 1 wherein:
the first clutch torque model relates a requested clutch torque and a difference between speeds of the left and right wheels to the actual clutch torque; and
the requested clutch torque is a requested amount of torque to be transferred by the clutch.
5. The system of claim 1 wherein the second clutch torque model relates a tire longitudinal force at the left wheel and a tire longitudinal force at the right wheel to the actual clutch torque.
6. The system of claim 5 further comprising a tire longitudinal force module configured to:
estimate the tire longitudinal forces at the left and right wheels using a first longitudinal force model when the electronic limited slip differential is unlocked; and
estimate the tire longitudinal forces at the left and right wheels using a second longitudinal force model when the electronic limited slip differential is locked, wherein the second longitudinal force model is different than the first longitudinal force model.
7. The system of claim 6 wherein:
the first longitudinal force model relates the actual clutch torque and an axle input torque to the tire longitudinal forces at the left and right wheels; and
the axle input torque is an amount of torque transferred from the engine to the electronic limited slip differential.
8. The system of claim 6 wherein:
the second longitudinal force model includes:
a first relationship between an axle input torque and the tire longitudinal forces at the left and right wheels; and
a second relationship between tire vertical forces at the left and right wheels and the tire longitudinal forces at the left and right wheels; and
the axle input torque is an amount of torque transferred from the engine to the electronic limited slip differential.
9. The system of claim 8 wherein, based on a slip ratio of the left and right wheels, the tire longitudinal force module selects the second relationship from a plurality of different relationships between the tire vertical forces at the left and right wheels and the tire longitudinal forces at the left and right wheels.
10. The system of claim 1 wherein the clutch state module configured to determine whether the clutch is locked or unlocked based on:
a difference between speeds of the left and right wheels; and
a torque capacity of the clutch.
11. A system comprising:
a clutch state module of a vehicle and configured to determine whether a clutch of an electronic limited slip differential is locked or unlocked, the electronic limited slip differential coupling an engine of a vehicle to left and right wheels of the vehicle; and
a tire longitudinal force module of the vehicle and configured to:
estimate tire longitudinal forces at the left and right wheels using a first longitudinal force model when the electronic limited slip differential is unlocked; and
estimate the tire longitudinal forces at the left and right wheels using a second longitudinal force model when the electronic limited slip differential is locked, wherein the second longitudinal force model is different than the first longitudinal force model.
12. The system of claim 11 wherein:
the first longitudinal force model relates an actual clutch torque and an axle input torque to the tire longitudinal forces at the left and right wheels;
the actual clutch torque is an actual torque transferred by the clutch; and
the axle input torque is an amount of torque transferred from the engine to the electronic limited slip differential.
13. The system of claim 12 further comprising a clutch torque module configured to:
estimate the actual clutch torque using a first clutch torque model when the electronic limited slip differential is unlocked; and
estimate the actual clutch torque using a second clutch torque model when the electronic limited slip differential is locked, wherein the second clutch torque model is different than the first clutch torque model.
14. The system of claim 13 wherein:
the first clutch torque model relates a requested clutch torque and a difference between the left and right wheel speeds to the actual clutch torque; and
the requested clutch torque is a requested amount of torque to be transferred by the clutch.
15. The system of claim 13 wherein the second clutch torque model relates a tire longitudinal force at the left wheel and a tire longitudinal force at the right wheel to the actual clutch torque.
16. The system of claim 11 wherein the second longitudinal force model includes:
a first relationship between an axle input torque and the tire longitudinal forces at the left and right wheels; and
a second relationship between tire vertical forces at the left and right wheels and the tire longitudinal forces at the left and right wheels; and
the axle input torque is an amount of torque transferred from the engine to the electronic limited slip differential.
17. The system of claim 16 wherein, based on a slip ratio of the left and right wheels, the tire longitudinal force module selects the second relationship from a plurality of different relationships between the tire vertical forces at the left and right wheels and the tire longitudinal forces at the left and right wheels.
18. A system comprising:
a clutch state module of a vehicle and configured to determine whether a clutch of an electronic limited slip differential is locked or unlocked, the electronic limited slip differential coupling an engine of a vehicle to left and right wheels of the vehicle;
a clutch torque module of the vehicle and configured to:
estimate an actual torque transferred by the clutch using a first clutch torque model when the electronic limited slip differential is unlocked; and
estimate the actual clutch torque using a second clutch torque model when the electronic limited slip differential is locked, wherein the second clutch torque model is different than the first clutch torque model; and
a tire longitudinal force module configured to:
estimate tire longitudinal forces at the left and right wheels using a first longitudinal force model when the electronic limited slip differential is unlocked; and
estimate the tire longitudinal forces at the left and right wheels using a second longitudinal force model when the electronic limited slip differential is locked, wherein the second longitudinal force model is different than the first clutch torque model.
19. The system of claim 18 wherein:
the first clutch torque model includes a first-order transfer function that relates a requested clutch torque and a hyperbolic tangent function of a difference between speeds of the left and right wheels to the actual clutch torque;
the requested clutch torque is a requested amount of torque while accounting for transient dynamics of the clutch to be transferred by the clutch;
the second clutch torque model relates a tire longitudinal force at the left wheel and a tire longitudinal force at the right wheel to the actual clutch torque;
the first longitudinal force model relates the actual clutch torque and an axle input torque to the tire longitudinal forces at the left and right wheels;
the axle input torque is an amount of torque transferred from the engine to the electronic limited slip differential; and
the second longitudinal force model includes:
a first relationship between the axle input torque and the tire longitudinal forces at the left and right wheels; and
a second relationship between tire vertical forces at the left and right wheels and the tire longitudinal forces at the left and right wheels.
20. The system of claim 19 wherein, based on a slip ratio of the left and right wheels, the tire longitudinal force module selects the second relationship from a plurality of different relationships between the tire vertical forces at the left and right wheels and the tire longitudinal forces at the left and right wheels.