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Lepelletier 7-Speed

Model seven-speed Lepelletier transmission based on planetary gear and Ravigneaux gear


Transmission Templates


The Lepelletier 7-Speed transmission block is a subsystem that models a standard automotive transmission having seven selectable forward gear ratios and a single reverse gear ratio. The Lepelletier gearbox is constructed by connecting a planetary gear to a Ravigneaux gear. The sun of the planetary gear is connected by a clutch (F) to the housing and can be braked. The carrier of the planetary gear is connected, by another clutch (C), to the small sun wheel of the Ravigneaux gear. The input, or driver, shaft is always connected to the ring of the planetary gear and can simultaneously be connected to the carrier and large sun of the Ravigneaux gear using separate clutches (B and A). The output, or driven, shaft is connected to the ring of the Ravigneaux gear. The six transmission clutches A, B, C, D, E, and F are modeled with Controllable Friction Clutch blocks. You connect the transmission along a driveline axis, with the In and Out connector ports representing the input and output shafts, respectively.

This transmission subsystem has three independent internal degrees of freedom and therefore requires that three clutches be locked at any instant in order to achieve a unique drive ratio from the input shaft to the output shaft. The clutch schedule and the corresponding drive ratios are provided in the block subsystem's clutch schedule table. You disengage this transmission by unlocking all its clutches simultaneously.

Using Transmission Template Subsystems

A Transmission Template block is not library-linked. Once you make a copy in your model, you can use it as is. You can also open and customize it as a subsystem by reconfiguring the properties of the individual Gear, Controllable Friction Clutch, and Inertia blocks.

You must provide a six-component Simulink® vector signal of the normalized pressures applied to each clutch. The order of the pressure signals is ABCDEF.

Default Inertia, Gear, and Clutch Settings

All the Controllable Friction Clutch blocks in this Transmission subsystem have their default settings. The Gear ratios are reset to nondefault values.

To prevent dynamical singularities, some of the gear wheels have attached Inertia blocks with small default inertias in the 10–2 kg-m2 (kilogram-meters2) range.

Subsystem Parameters

The gear ratio is the ratio of gear wheel radii r, gear wheel teeth N, or torque transferred τ. The gear ratio is the reciprocal of the ratio of the angular velocities ω transferred. The drive ratio is the effective gear ratio, output to input, of the entire transmission.

The basic Lepelletier 7-speed transmission gear ratios are

gRS = Planetary ring/sun gear ratio = rpR/rpS = NpR/NpS

gRSl = Ravigneaux ring/large sun gear ratio = rR/rSl = NR/NSl

gRSs = Ravigneaux ring/small sun gear ratio = rR/rSs = NR/NSs

This table specifies the locked (L) and free (F) clutches A, B, C, D, E, and F for each gear setting. A free clutch is completely disengaged.

Lepelletier 7-Speed Clutch Schedule

Gear SettingDrive RatioABCDEF
2(gRSl + gRSs)·(1 + gRS)/[gRS·(1 + gRSl)]FFLFLL
3(1 + gRS)/gRSLFLFFL
4gRSs·(1 + gRS)/[gRSs·(1 + gRS) - 1]FLLFFL
6gRSl·(1 + gRS)/[gRSl·(1 + gRS) + 1]LLFFFL
7gRSl/(1 + gRSl)FLFFLL

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