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Technical Briefs

Automotive Transmission Clutch Fill Control Using a Customized Dynamic Programming Method

[+] Author and Article Information
Xingyong Song, Mohd Azrin Mohd Zulkefli, Zongxuan Sun

 Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455

Hsu-Chiang Miao

 Retiree Research and Development Center, General Motors Corporation, Warren, Michigan 48090

J. Dyn. Sys., Meas., Control 133(5), 054503 (Aug 05, 2011) (9 pages) doi:10.1115/1.4003797 History: Received December 21, 2009; Revised December 29, 2010; Published August 05, 2011; Online August 05, 2011

Clutch to clutch shift control technology, which is the key enabler for a compact and low cost transmission design, is important for both automatic and hybrid transmissions. To ensure a smooth clutch to clutch shift, precise synchronization between the on-coming and off-going clutches is critical. This further requires the on-coming clutch to be filled and ready for engagement at the predetermined time. Due to the compact design, currently there is no pressure sensor inside the clutch chamber, and therefore the clutch fill can only be controlled in an open loop fashion. The traditional clutch fill approach, by which the clutch fill input pressure command is manually calibrated, has a couple of limitations. First, the pressure profile is not optimized to reduce the peak flow demand during clutch fill. Moreover, it is not systematically designed to account for uncertainties in the system, such as variations of solenoid valve delay and parameters of the clutch assembly. In this paper, we present a systematic approach to evaluate the clutch fill dynamics and synthesize the optimal pressure profile. First, a clutch fill dynamic model, which captures the key dynamics in the clutch fill process, is constructed and analyzed. Second, the applicability of the conventional numerical dynamic programming (DP) method to the clutch fill control problem, which has a stiff dynamic model, is explored and shown to be ineffective. Thus, we proposed a customized DP method to obtain the optimal and robust pressure profile subject to specified constraints. The customized DP method not only reduces the computational burden significantly, but also improves the accuracy of the result by eliminating the interpolation errors. To validate the proposed method, a transmission clutch fixture has been designed and built in the laboratory. Both simulation and experimental results demonstrate that the proposed customized DP approach is effective, efficient and robust for solving the clutch fill optimal control problem.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Scheme diagram of a six speed automatic transmission

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Figure 2

Schematic diagram of a clutch mechanism

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Figure 3

Stick friction diagram

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Figure 4

Desired trajectory of x2

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Figure 5

Shifted trajectory of x2

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Figure 6

State space quantization

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Figure 7

Clutch fill experimental setup

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Figure 8

The hydraulic circuit scheme diagram

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Figure 9

Experiments for measuring the stick friction Fstatic

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Figure 10

System identification model verification

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Figure 11

Optimal input pressure and the experimental tracking results

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Figure 12

Experimental results for clutch displacement, velocity and input flow rate

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Figure 13

Clutch fill repeatability test. (a) Five groups of displacement profiles. (b) Histogram of data error comparing with optimal trajectory

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Figure 14

Clutch fill robustness test

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Figure 15

Histogram of clutch fill piston final position

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Figure 16

Experimental data demonstrating clutch fill robustness on time delay

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Figure 17

Optimal and nonoptimal clutch fill velocities profile comparison

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