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Disc Clutch

Idealized disc clutch coupler

  • Library:
  • Powertrain Blockset / Drivetrain / Couplings

Description

The Disc Clutch block implements an idealized disc clutch coupler. The block couples the rotary input and output shafts through an idealized friction model. To determine the output torque, the block uses friction parameters, relative slip velocity, and applied input pressure.

In fuel economy and powertrain efficiency studies, you can use the Disc Clutch block to model the mechanical power transfer between common driveline elements such as transmissions, engines, and differentials.

To approximate the torque response, the Disc Clutch block implements friction and dynamic models that depend on the clutch lockup condition. The block determines the locked or unlocked condition based on an idealized dry clutch friction model. This table summarizes the logic the block uses to determine the clutch condition.

Clutch ConditionWhen
UnlockedωiωoorTfmax<|JoTi(JobiJibo)ωi/oJo+Ji|
Lockedωi=ωoandTfmax<|TiJi(bi+bo)ωiJo+Ji+boωi|

This table summarizes the friction and dynamic models that the block uses for locked or unlocked clutch conditions.

Clutch ConditionFriction ModelDynamic Model
UnlockedTfmax=Tkwhere,Tk=NdiscPcAeffReffμktanh[4(ωiωo)]Reff=2(Ro3-Ri3)3(Ro2-Ri2) andPc=max(PcPeng,0)ω˙iJi=TiTfωibiω˙oJo=Tf+Toωobo
LockedTfmax=Tswhere,Ts=NdiscPcAeffReffμsReff=2(Ro3-Ri3)3(Ro2-Ri2)ω˙i(Jo+Ji)=Toωi(bi+bo)+Tiωi=ωo

Power Accounting

For the power accounting, the block implements these equations.

Bus Signal DescriptionEquations

PwrInfo

PwrTrnsfrd — Power transferred between blocks

  • Positive signals indicate flow into block

  • Negative signals indicate flow out of block

PwrBase

Applied base power

ωiTi

PwrFlwr

Applied follower output power

ωoTo

PwrNotTrnsfrd — Power crossing the block boundary, but not transferred

  • Positive signals indicate an input

  • Negative signals indicate a loss

PwrDampLoss

Damping power loss

boωo2 biωi2

PwrCltchSlipLoss

Clutch slip power loss

Tk(ωiωo)

PwrStored — Stored energy rate of change

  • Positive signals indicate an increase

  • Negative signals indicate a decrease

PwrStoredBase

Rate change in base rotational kinetic energy

ω˙iωiJi

PwrStoredFlwr

Rate change in follower rotational kinetic energy

ω˙oωoJo

The equations use these variables.

ωi

Input shaft angular speed

ωo

Output shaft angular speed

bi

Input shaft viscous damping

bo

Output shaft viscous damping

Ji

Input shaft moment of inertia

Jo

Output shaft moment of inertia

Tf

Frictional torque

Ti

Net input torque

Tk

Kinetic frictional torque

To

Net output torque

Ts

Static frictional torque

Tfmax

Maximum frictional torque before slipping

Pc

Applied clutch pressure

Peng

Engagement pressure

Aeff

Effective area

Ndisc

Number of frictional discs

Reff

Effective clutch radius

Ro

Annular disk outer radius

Ri

Annular disk inner radius

Re

Effective tire radius while under load and for a given pressure

μs

Coefficient of static friction

μk

Coefficient of kinetic friction

Ports

Input

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Base gear input torque, Pc, in N·m^2.

Applied input torque, Ti, typically from the engine crankshaft or dual mass flywheel damper, in N·m.

Dependencies

To create this port, for Port Configuration, select Simulink.

Applied load torque, To, typically from the differential or drive shaft, in N·m.

Dependencies

To create this port, for Port Configuration, select Simulink.

Applied drive shaft angular speed, ωi, in rad/s. Applied drive shaft torque, Ti, in N·m.

Dependencies

To create this port, for Port Configuration, select Two-way connection.

Output

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Bus signal containing these block calculations.

SignalDescriptionUnits
BaseBTrq

Applied input torque, typically from the engine crankshaft or dual mass flywheel damper

N·m

BSpd

Applied drive shaft angular speed input

rad/s

FlwrFTrq

Applied load torque, typically from the differential

N·m

FSpd

Drive shaft angular speed output

rad/s

CltchCltchForce

Applied clutch force

N

CltchLocked

Clutch lock status

NA

CltchSpdRatio

Clutch speed ratio

NA

CltchEta

Clutch power transmission efficiency

NA

PwrInfo

PwrTrnsfrd

PwrBase

Applied base power

W
PwrFlwr

Applied follower output power

W

PwrNotTrnsfrd

PwrDampLoss

Damping power loss

W
PwrCltchSlipLoss

Clutch slip power loss

W

PwrStored

PwrStoredBase

Rate change in base rotational kinetic energy

W
PwrStoredFlwr

Rate change in follower rotational kinetic energy

W

Applied drive shaft angular speed input, ωi, in rad/s.

Dependencies

To create this port, for Port Configuration, select Simulink.

Drive shaft angular speed output, ωo, in rad/s.

Dependencies

To create this port, for Port Configuration, select Simulink.

Output drive shaft angular speed, ωoi, in rad/s. Output drive shaft torque, To, in N·m.

Dependencies

To create this port, for Port Configuration, select Two-way connection.

Parameters

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Block Options

Specify the port configuration.

Dependencies

Specifying Simulink creates these ports:

  • BSpd

  • FSpd

  • BTrq

  • FTrq

Specifying Two-way connection creates these ports:

  • B

  • F

Clutch force equivalent net radius, in m.

Number of disks, dimensionless.

Effective applied pressure area, in m^2.

Pressure to engage clutch, in Pa.

Input shaft inertia, in kg·m^2.

Output shaft inertia, in kg·m^2.

Kinetic friction coefficient, dimensionless.

Static friction coefficient, dimensionless.

Input shaft viscous damping, in N·m· s/rad.

Output shaft viscous damping, in N·m· s/rad.

Input shaft initial velocity, in rad/s.

Input shaft initial velocity, in rad/s.

Clutch actuation time constant, in s.

Select to lock clutch initially.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Introduced in R2017a