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Ravigneaux 4-Speed

Model Ravigneaux four-speed transmission based on Ravigneaux gear

Library

Transmission Templates

Description

The Ravigneaux 4-Speed transmission block is a subsystem that models a standard automotive transmission having four selectable forward gear ratios and a single reverse gear ratio. The main component of the transmission is a Ravigneaux gear. The input, or driver, shaft is connected, through a combination of the five clutches, to the small sun, the large sun, and the carrier of the Ravigneaux gear. The output, or driven, shaft is connected to the ring of the Ravigneaux gear. The five transmission clutches A, B, C, D, and E 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 two independent degrees of freedom and therefore requires two 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 five-component Simulink® vector signal of the normalized pressures applied to each clutch. The order of the pressure signals is ABCDE.

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 Ravigneaux 4-speed transmission gear ratios are

gRSl = Ring/large sun gear ratio = rR/rSl = NR/NSl

gRSs = Ring/small sun gear ratio = rR/rSs = NR/NSs

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

Ravigneaux 4-Speed Clutch Schedule

Gear SettingDrive RatioABCDE
Reverse-gRSlFFLLF
1gRSsFLFLF
2(gRSl + gRSs)/(1 + gRSl)FLFFL
31LLFFF
4gRSl/(1 + gRSl)LFFFL

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