Documentation

# 4-Speed Ravigneaux

Clutch schedule for a four-speed Ravigneaux transmission

• Library:
• Simscape / Driveline / Transmissions

## Description

The 4-Speed Ravigneaux block consists of one Ravigneaux gear set and five clutches. The follower shaft connects to the ring gear of the Ravigneaux set. Three of the clutches determine the gears that the base shaft connects to for power transfer. The other two clutches serve as brakes, grounding various gears of the Ravigneaux set to the transmission housing.

This diagram shows a four-speed Ravigneaux gear transmission. The labels for the gear components are superimposed on the input and output gears. The table lists the gear and clutch components that are labeled in the diagram.

LabelComponent
R.G.Ravigneaux gear
R Ring gear
CPlanet gear carrier
SLLarge sun gear
SSSmall sun gear
A–CForward clutches that control the power flow path
D–EForward, braking clutches

### Drive Ratios, Clutch Schedule, and Power Flow

The drive ratio between the transmission input and output shafts follows from the elementary gear ratios specified for the gear blocks. The elementary gear ratios are

`${g}_{1}=\frac{{N}_{R}}{{N}_{SL}},$`

and

`${g}_{2}=\frac{{N}_{R}}{{N}_{SS}},$`

where:

• NR is the number of teeth in the Ravigneaux ring gear.

• NSL is the number of teeth in the Ravigneaux large sun gear.

• NSS is the number of teeth in the Ravigneaux small sun gear.

The table shows the clutch schedule, drive-ratio expressions, drive-ratio default values, and the power-flow diagrams for each gear of the 4-Speed Ravigneaux block.

The letters in the clutch schedule columns denote the brakes and clutches. A value of `1` denotes a locked state and a value of `0` an unlocked state. The clutch schedule generates these signals based on the Gear port input signal. The signals are scaled through a Gain block and used as actuation inputs in the clutch blocks.

The power-flow diagrams show the power flow paths between input and output shafts for each gear setting. Power flow is shown in orange. Connections to the transmission housing (a mechanical ground) are shown in black.

GearClutch ScheduleDrive Ratio EquationDefault RatioPower Flow
ABCDR
410001$\frac{{g}_{1}}{1+{g}_{1}}$0.67

311000$1$1

201001$\frac{{g}_{1}+{g}_{2}}{1+{g}_{1}}$1.67

101010${g}_{2}$3

R00110$-{g}_{1}$-2

## Ports

### Input

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Specify -1 for reverse, 0 for neutral, and 1–4 for the forward gears.

Data Types: `single` | `double`

### Conserving

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Conserving port associated with the base shaft.

Conserving port associated with the follower shaft.

## Parameters

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Sets the initial engagement or disengagement of the clutches using the clutch schedule. When the transmission is in neutral, there is no power flow from the base shaft to the follower shaft.