Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2000-03-20
2001-12-25
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S155000, C701S060000
Reexamination Certificate
active
06332860
ABSTRACT:
TECHNICAL FIELD
This invention relates to a model-based shift control for an automatic transmission, and more particularly to a pressure control of the on-coming clutch during an upshift.
BACKGROUND OF THE INVENTION
In general, a motor vehicle automatic transmission includes a number of gear elements and selectively engageable friction elements (referred to herein as clutches) that are controlled to establish one of several forward speed ratios between the transmission input and output shafts. The input shaft is coupled to the vehicle engine through a fluid coupling such as a torque converter, and the output shaft is coupled to the vehicle drive wheels through a differential gearset.
Shifting from a currently established speed ratio to new speed ratio involves, in most cases, disengaging a clutch (off-going clutch) associated with the current speed ratio and engaging a clutch (on-coming clutch) associated with the new speed ratio. Various combinations of shift type (upshift or downshift) and power flow (power-on or power-off) have been analyzed for control purposes in order to achieve consistent high quality shifting. Power-on upshifting, the subject of this invention, is generally characterized as comprising three phases: a fill phase in which an apply chamber of the on-coming clutch is filled with hydraulic fluid in preparation for torque transmission, a torque phase in which a torque exchange between on-coming and off-going clutches occurs without a corresponding speed change, and an inertia phase in which the input shaft changes speed.
Various techniques have been used for electronically controlling the above-mentioned phases of a power-on upshift; see, for example, the U.S. Pat. No. 5,058,460 to Hibner et al., issued on Oct. 22, 1991, and assigned to the assignee of the present invention. In Hibner et al., the fill, torque and inertia phases are carried out by successively executed control routines. In the fill phase, the on-coming clutch pressure (referred to herein as Ponc) is commanded to a maximum value for a predetermined fill time, or until a pull-down of the input speed is detected. The torque phase is then carried out by releasing the off-going clutch, reducing Ponc to an initial value, and then progressively increasing Ponc until a pull-down of the input speed is detected. Thereafter, the inertia phase is carried out by adjusting Ponc as required to drive the input speed to its post-shift level in accordance with a predetermined speed vs. time profile. In Hibner et al., the clutch pressure (on-coming and off-going) is controlled in an open-loop manner during the fill and torque phases, but is controlled in a closed-loop manner based on input speed error during the inertia phase. In another technique described in the U.S. Pat. No. 4,707,789 to Downs et al., issued on Nov. 17, 1987, and assigned to the assignee of the present invention, the clutch pressures are controlled in an open-loop manner, and the open-loop parameters are adaptively adjusted after a shift is completed based on parameters measured during the shift, such as the inertia phase time or the occurrence of over-filling or under-filling.
SUMMARY OF THE INVENTION
The present invention is directed to an improved control for an automatic transmission upshift, wherein the on-coming clutch pressure (Ponc) is scheduled during the torque and inertia phases of the shift in accordance with the summation of feed-forward and feed-back control terms, the feed-forward control term being developed using an inverse dynamic model of the transmission. The feed-forward control term is determined by developing a desired acceleration trajectory of the input shaft, and periodically applying the acceleration trajectory to the inverse dynamic model to obtain an estimate of the required on-coming clutch pressure, given the transmission input torque. The feed-back control term is based on a comparison of the expected input speed response with the actual input speed response, and corrects for modeling errors in the feed-forward control, providing disturbance rejection and improved command following. Additionally, the closed-loop feedback error is used to enable adaptive correction of the feed-forward control so that the estimated on-coming clutch pressure more nearly produces the commanded input shaft acceleration. Controlling the input shaft acceleration in this manner achieves more consistent shift feel and energy dissipation in the on-coming clutch, with less intensive calibration effort and improved adaptability to different powertrain and vehicle-type configurations.
REFERENCES:
patent: 5029086 (1991-07-01), Yoshimura
patent: 5058460 (1991-10-01), Hibner et al.
patent: 5123302 (1992-06-01), Brown et al.
Hubbard Gregory A
Runde Jeffrey Kurt
Estremsky Sherry
General Motors Corporation
Hargitt Laura C.
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