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CR-CR 4-Speed

Model CR-CR four-speed transmission based on two planetary gear sets


Transmission Templates


The CR-CR 4-Speed transmission block is a subsystem model based on a simple planetary gearbox consisting of two standard planetary gear sets, an input set and an output set, connected together. (CR-CR stands for "carrier-ring–carrier-ring.") The ring of the input planetary gear set is connected to the carrier of the output planetary set. Similarly, the ring of the output planetary gear set is connected to the carrier of the input planetary gear set. The input, or driver, shaft is connected either to the carrier of the input planetary gear set or to the ring of the output planetary gear set. The output, or driven, shaft is connected to the carrier of the output planetary gear set and to the ring of the input planetary gear set. The five transmission clutches A, B, C, D, and R are modeled with Controllable Friction Clutch blocks. (The R clutch engages only in reverse.) 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 internal degrees of freedom and therefore requires that 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 ABCDR.

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 10–4 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 CR-CR 4-speed transmission gear ratios are

gi = Input planetary ring/input planetary sun gear ratio = rRi/rSi = NRi/NSi

go = Output planetary ring/output planetary sun gear ratio = rRo/rSo = NRo/NSo

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

CR-CR 4–Speed Clutch Schedule

Gear SettingDrive RatioABCDR
11 + goLFFLF
21 + go/(1 + gi)LFLFF
4gi/(1 + gi)FLLFF


These Simscape™ Driveline™ example models make use of CR-CR transmission blocks to transfer drivetrain torque and motion:

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