Realtime estimation of clutch piston position
The present invention provides an apparatus and method for estimating the realtime position of a clutch piston during the fill cycle using noisy pressure measurements which ensures proper and desired clutch operation. Pressures on both sides of a flow controlling orifice, at the fluid control actuator and the clutch cylinder are measured and these measurements in conjunction with other system parameters such as orifice size, clutch volume and return spring characteristics are used to solve nonlinear dynamic equations (algorithms) which reside in a microprocessor. The microprocessor provides outputs corresponding to an estimate of the current position of the clutch piston, an estimate of the current speed of the piston and an estimate of the current hydraulic pressure. The method can also be utilized to detect clutch wear.
1. An apparatus for estimating a present position of a clutch piston comprising, in combination,
a source of pressurized hydraulic fluid,
a proportioning control valve having an inlet communicating with said source of hydraulic fluid and an outlet,
a first pressure sensor disposed to sense hydraulic fluid pressure proximate said outlet and having a first output,
a flow restricting orifice in fluid communication with said outlet,
a clutch cylinder in fluid communication with said orifice,
a second pressure sensor disposed to sense hydraulic fluid pressure proximate said clutch cylinder and having a second output, and
a microprocessor having inputs for said first and second outputs and including a model based prediction processor and a measurement correction processor for determining an acceleration of said clutch piston, a change in pressure at said clutch piston and a position of such clutch piston.
2. The apparatus of claim 1 wherein said source of pressurized hydraulic fluid includes a pump.
3. The apparatus of claim 1 wherein said source of pressurized hydraulic fluid includes an electric pump and an accumulator.
4. The apparatus of claim 1 wherein said control valve is a variable bleed (VBS) solenoid valve and a pressure regulator valve.
5. The apparatus of claim 1 wherein said control valve is a variable force (VFS) solenoid valve.
6. The apparatus of claim 1 further including a friction clutch pack acted upon by said piston and having an input member and an output member.
7. The apparatus of claim 1 further including a friction clutch pack acted upon by said piston, a wave plate adjacent said friction clutch pack and a return spring acting on said piston.
8. The apparatus of claim 1 wherein said microprocessor is a component of a transmission control module.
9. An apparatus for determining a position of a hydraulic piston in a clutch assembly comprising, in combination,
a source of pressurized hydraulic fluid,
a control valve having an inlet communicating with said source of hydraulic fluid and an outlet,
means for determining hydraulic fluid pressure at or near said outlet,
a flow restricting orifice in fluid communication with said outlet,
a clutch cylinder in fluid communication with said orifice,
a pressure sensor for sensing hydraulic fluid pressure at or near said clutch cylinder, and
a transmission control module for receiving data from said sensor and said means for determining and including a model based prediction processor and a measurement correction processor for determining an acceleration of said clutch piston, a change in pressure at said clutch piston and a position of such clutch piston.
10. The apparatus of claim 9 wherein said source of pressurized hydraulic fluid includes a pump and an accumulator.
11. The apparatus of claim 9 wherein said control valve is a variable bleed (VBS) solenoid valve and a pressure regulator valve.
12. The apparatus of claim 9 wherein said control valve is a variable force (VFS) solenoid valve.
13. The apparatus of claim 9 further including a friction clutch pack acted upon by said piston and having an input member and an output member.
14. The apparatus of claim 9 further including a friction clutch pack acted upon by said piston, a wave plate adjacent said friction clutch pack and a return spring acting on said piston.
15. The apparatus of claim 9 wherein said means for determining is one of a dedicated pressure sensor, a pressure sensor in another system and a predetermined design value.
16. A method for estimating a position of a hydraulic piston in a clutch assembly comprising, in combination,
providing a source of pressurized hydraulic fluid,
controlling a flow of hydraulic fluid from said source of hydraulic fluid into an outlet line,
determining hydraulic fluid pressure in said outlet line,
restricting a flow of hydraulic fluid in said outlet line through an orifice,
providing said restricted flow of hydraulic fluid to a clutch cylinder;
sensing hydraulic fluid pressure at said clutch cylinder,
utilizing said determined and said sensed hydraulic fluid pressures to determine an acceleration of said clutch piston, a time rate of change in pressure at said clutch piston and a rate of change of position of such clutch piston, and
utilizing said acceleration and rates of change to compute estimates of a position of a clutch piston, a velocity of said piston and fluid pressure in said cylinder.
17. The method of claim 16 further including the step of providing a transmission control module for receiving said sensed hydraulic fluid pressures and controlling said flow of hydraulic fluid.
18. The method of claim 16 wherein said pressure determining step includes assuming an operating design pressure.
19. The method of claim 16 wherein said pressure determining step includes sensing said pressure with a sensor.