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Dog Clutch

Clutch with toothed plates that engage when plate teeth become enmeshed

  • Dog Clutch block

Libraries:
Simscape / Driveline / Clutches

Description

The Dog Clutch block represents a nonslip clutch that uses the positive engagement of interlocking teeth to transfer torque between drive shafts. Dog clutches used in manual transmissions that engage and disengage power transmission by sliding two mating parts together. The ring and hub are the primary components of a dog clutch. The input shaft turns the ring, which has slots or teeth. The hub connects to an output shaft that has protruding "dogs" that fit into the slots of the ring. When you shift the transmission, the dogs on the hub engage with the slots on the ring, locking the two components and transmitting power. You shift again to disengage the clutch, which causes the dogs to disengage from the slots and allows the transmission to spin freely.

Engagement occurs when the ring and hub interlock. The ring and the hub spin together as a unit. To control engagement, the dog clutch contains a shift linkage that governs the position of the ring with respect to the hub. You can control the shift linkage with a physical signal or a mechanical translational conserving port by using the Torque transmission model parameter. The torque transmission model that you choose corresponds to a fidelity and level of abstraction:

  • Two-mode — Fully abstracted torque transmission model based on mode charts. This setting is fast enough for real-time simulation and does not require knowledge of the clutch dimensions. You can control the shift linkage only with a physical or logic-controlled signal.

  • Friction clutch approximation - Suitable for HIL and linearization — Medium- to high-fidelity composite implementation of the Fundamental Friction Clutch block. This setting supports thermal modeling. You can control the shift linkage with either a physical signal or a mechanical translational conserving port.

  • Dynamic with backlash — High-fidelity clutch engagement model that accounts for phenomena such as backlash, torsional compliance, and contact forces between the ring and hub teeth.

Moving the ring toward the hub so that the teeth interlock changes the clutch state to engaged. Tooth overlap must exceed a minimum value for engagement. Moving the ring in reverse so that the two sets of teeth no longer interlock changes the clutch state back to disengaged. Port S specifies the shift linkage position. When the clutch is fully disengaged, the shift linkage position is zero. When the clutch is fully engaged, the shift linkage position equals the sum of the tooth height and the ring-hub clearance of the fully disengaged state,

z=h+zGap,

where:

  • z is the shift linkage position.

  • h is the tooth height.

  • zGap is the ring-hub clearance when disengaged.

The figure shows side and front views of the dog clutch and some of its relevant variables.

Torque Transmission Models

You can choose from three torque transmission models.

Two-Mode

To simulate an abstracted dog clutch, set Torque transmission model to Two-mode. The two-mode torque transmission model uses mode charts to control whether the clutch is engaged or disengaged. You can control the shift linkage position using logic-based commands or a linkage position physical signal. When you use logic-based commands, false at port X represents a disengaged clutch, and true represents an engaged clutch.

Friction Clutch Approximate Model

When you set Torque transmission model to Friction clutch approximation - Suitable for HIL and, the block treats the clutch engagement as a friction phenomenon between the ring and the hub. This setting is better suited for linearization, fixed-step simulation, and hardware-in-loop (HIL) simulation. The block uses a composite implementation of the Fundamental Friction Clutch block.

When you use this setting, the clutch has three possible configurations: disengaged, engaged, and locked. When disengaged, the contact force between the ring and the hub is zero. This force remains zero until the shift linkage reaches the minimum position for engagement.

When the ring-hub tooth overlap, h, exceeds the minimum value for engagement, the contact force between the two components begins to increase linearly with the shift linkage position, z.

At full engagement, the contact force reaches its maximum value and the clutch state switches to locked. In this state, the ring and the hub spin as a unit without slip. To unlock the clutch, the transmitted torque must exceed the value of the Maximum transmitted torque parameter.

Dynamic Model with Backlash

When you set Torque transmission model to Dynamic with backlash, the block simulates clutch phenomena such as backlash, torsional compliance, and contact forces between ring and hub teeth. This model provides greater accuracy than the friction clutch approximation.

When you use this setting, the clutch has two possible configurations: disengaged and engaged. When disengaged, the contact force between the ring and the hub is zero. This force remains zero until the shift linkage reaches the minimum position for engagement.

When the ring-hub tooth overlap, h, exceeds the engagement threshold value, the clutch transmits torque. This torque is the sum of torsional spring and damper components, including backlash between the ring and hub teeth, such that

TC={kRH(ϕδ2)μR·ωϕ>δ20δ2<ϕ<δ2kRH(ϕ+δ2)μRωϕ<δ2,

where:

  • kRH is the torsional stiffness of the ring-hub coupling.

  • ϕ is the relative angle, about the common rotation axis, between the ring and the hub.

  • δ is the backlash between ring and hub teeth.

  • ω is the relative angular velocity between the ring and the hub. This variable describes how fast the two components slip past each other.

Compliant end stops limit the translational motion of the clutch shift linkage and the ring. The compliance model treats the end stops as linear spring-damper sets. The location of the end stops depends on the relative angle and angular velocity between the ring and hub teeth:

  • If the teeth align and the relative angular velocity is smaller than the maximum value for clutch engagement, the end stop location is the sum of the ring-hub clearance when fully disengaged and the tooth height. The clutch can engage in this end stop position.

  • If the teeth do not align or the relative angular velocity exceeds the maximum value for clutch engagement, the end-stop location is set to prevent the ring from engaging the hub. The clutch does not engage in this end stop position.

Translational friction opposes shift linkage and ring motion. This friction is the sum of Coulomb and viscous components, such that

FZ=kK·FN·tanh(4vvth)μTv,

where:

  • FZ is the net translational friction force acting on the shift linkage and ring.

  • kK is the kinetic friction coefficient between ring and hub teeth.

  • FN is the normal force between ring and hub teeth, where FN = TC/Rm.

  • v is the translational velocity of the shift linkage and the ring.

  • vth is the translational velocity threshold. Below this threshold, a hyperbolic tangent function smooths the Coulomb friction force to zero as the shift linkage and ring velocity tends to zero.

  • μT is the viscous damping coefficient acting on the shift linkage and the ring.

Clutch Engagement Conditions

The clutch engages when it satisfies these geometrical and dynamic conditions:

  • The minimum position where the ring and the hub can engage is

    z=h0+zGap,

    where h0 is the minimum tooth overlap for clutch engagement. Adjust this parameter to minimize engagement instability, that is, the tendency of the clutch to switch rapidly between engaged and disengaged states

  • The magnitude of the relative angular velocity between the ring and the hub is smaller than the maximum engagement velocity, such that

    |ω|<|ωmax|,

    where ωmax is the maximum value of the relative angular velocity at which engagement can occur.

  • If Torque transmission model is Friction clutch approximation - Suitable for HIL and linearization, the engagement occurs only if torque transfer between the ring and the hub is smaller than the maximum transmitted torque that the clutch supports.

  • If Torque transmission model is Dynamic with backlash, the engagement occurs only if the relative angular position of the ring and hub teeth allows them to interlock.

Rotational Power Dissipation

When the clutch slips under an applied torque, it dissipates power. The power loss equals the product of the slip angular velocity and the contact torque between the ring and the hub, such that

Ploss=ω·TC,

where:

  • Ploss is the dissipated power due to slipping.

  • TC is the kinetic contact torque.

Thermal Modeling

When you set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, you can model the effects of heat flow and temperature change by using the optional thermal conserving port, T.

Linearization

To optimize your model for linearization, use the Clutch > Torque transmission model parameter default setting, Friction clutch approximation - Suitable for HIL and linearization.

Hardware-in-the-Loop Simulation

For optimal simulation performance, use the Clutch > Torque transmission model parameter default setting, Friction clutch approximation - Suitable for HIL and linearization.

Ports

Input

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Physical signal input port associated with the shift linkage, unitless. A logical true allows the clutch to engage if the relative speeds of the hub and ring are within tolerance. A logical false causes the clutch to disengage.

Dependencies

To enable this port, set Torque transmission model to:

  • Two-mode

  • Friction clutch approximation - Suitable for HIL and linearization, and set Shift linkage control to Physical signal

  • Dynamic with backlash, and set Shift linkage control to Physical signal

Output

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Physical signal output port associated with the clutch position, in m or unitless. When you set Torque transmission model to Two-mode, the port outputs a logical value true for engaged or false for disengaged. Otherwise, the port outputs the position of the clutch.

Conserving

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Mechanical rotational conserving port associated with the clutch hub

Mechanical rotational conserving port associated with the clutch ring.

Mechanical translational conserving port associated with shift linkage.

Dependencies

To enable this port, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash and set Shift linkage control to Conserving port.

Thermal conserving port associated with heat flow.

Dependencies

To enable this port, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Parameters

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Clutch

Computational framework for modeling the dynamic behavior of the dog clutch:

  • Two-mode — Fully abstracted torque transmission model based on mode charts. This setting is fast enough for real time simulation and does not require knowledge of the clutch dimensions. You can control the shift linkage only with a physical or logic-controlled signal.

  • Friction clutch approximation - Suitable for HIL and linearization — Medium- to high-fidelity composite implementation of the Fundamental Friction Clutch block. This setting supports thermal modeling. You can control the shift linkage with either a physical signal or a mechanical translational conserving connection.

  • Dynamic with backlash — High-fidelity clutch engagement model, that accounts for phenomena such as backlash, torsional compliance, and contact forces between the ring and hub teeth.

Minimum rotational speed at which the clutch delivers power.

Dependencies

To enable this parameter, set Torque transmission model to Two-mode.

Whether to enable the thermal conserving port, T.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization.

Distance from the ring or hub center to the corresponding tooth center. The mean tooth radius determines the normal contact forces between the ring and hub teeth given the transmission torque between the two components. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash.

Largest torque that the clutch can transmit. This value corresponds to a nonslip engaged configuration. If the torque transmitted between the ring and the hub exceeds this value, the two components begin to slip with respect to each other. This torque determines the static friction limit in the friction clutch approximation.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Omit.

Temperature values. The minimum number of values depends on the interpolation method that you select. For linear interpolation, provide at least two values per dimension. For smooth interpolation, provide at least three values per dimension. The values in the vector must increase from left to right.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Maximum transmitted torque for a given temperature in the Temperature vector parameter.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Interpolation method for approximating the output value when the input value is between two consecutive grid points:

  • Linear — Select this option for the best performance.

  • Smooth — Select this option to produce a continuous curve with continuous first-order derivatives.

For more information on interpolation algorithms, see the PS Lookup Table (1D) block reference page.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Extrapolation method for determining the output value when the input value is outside the range specified in the argument list:

  • Linear — Select this option to produce a curve with continuous first-order derivatives in the extrapolation region and at the boundary with the interpolation region.

  • Nearest — Select this option to produce an extrapolation that does not go above the highest point in the data or below the lowest point in the data.

  • Error — Select this option to avoid going into the extrapolation mode. If the input signal is outside the range of the table, the simulation stops and generates an error.

For more information on extrapolation algorithms, see the PS Lookup Table (1D) block reference page.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Total number of teeth in the ring or the hub. The two components have equal tooth numbers. The value must be greater than or equal to one.

Dependencies

To enable this parameter, set Torque transmission model to Dynamic with backlash.

Allowable angular motion, or play, between the ring and hub teeth when the clutch is engaged. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Dynamic with backlash.

Linear torsional stiffness coefficient at the contact interface between the ring and hub teeth. This coefficient characterizes the restoring component of the contact force between the two sets of teeth. Greater stiffness values correspond to greater contact forces. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Dynamic with backlash.

Linear torsional damping coefficient at the contact interface between the ring and hub teeth. This coefficient characterizes the dissipative component of the contact force between the two sets of teeth. Greater damping values correspond to greater energy dissipation during contact. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Dynamic with backlash.

Shift Linkage

Abstract shift linkage control to use for two-mode torque transmission.

  • Logic-controlled — Input the shift linkage as a Boolean operator using the physical signal port S.

  • Physical signal — Input shift linkage position directly through the physical signal port S.

Dependencies

To enable this parameter, set Torque transmission model to Two-mode.

Port type for shift linkage control:

  • Physical signal — Input shift linkage position directly through the physical signal port, S.

  • Conserving port — Input the shift linkage position dynamically through the translational conserving port, S.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash.

Distance between the base and crest of a tooth. The ring and hub teeth share the same height. The tooth height and the ring-hub clearance when fully disengaged determine the maximum travel span of the shift linkage. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to:

  • Two-mode, and set Abstract shift linkage control to Physical signal

  • Friction clutch approximation - Suitable for HIL and linearization

  • Dynamic with backlash

Maximum open gap between the ring and hub tooth crests along the shift linkage translation axis. This gap corresponds to the fully disengaged clutch state. The tooth height and the ring-hub clearance when fully disengaged determine the maximum travel span of the shift linkage. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to:

  • Two-mode, and set Abstract shift linkage control to Physical signal

  • Friction clutch approximation - Suitable for HIL and linearization

  • Dynamic with backlash

Whether to enable a hard stop when the shift linkage travels beyond the fully disengaged position.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash and set Shift linkage control to Conserving port.

Linear stiffness coefficient of the ring end stop. This coefficient characterizes the restoring component of the contact force that resists translational motion past the end stops. Greater stiffness values correspond to greater contact forces and a smaller end stop compliance. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash and set Shift linkage control to Conserving port.

Linear damping coefficient of the ring end stop. This coefficient characterizes the dissipative component of the contact force that resists translational motion past the end stops. Greater damping values correspond to greater energy dissipation during contact. The value must be greater than or equal to zero

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash and set Shift linkage control to Conserving port.

Linear damping coefficient acting on the shift linkage. This coefficient characterizes the dissipative force that resists shift linkage motion due to viscous damping. Greater coefficient values correspond to greater energy dissipation during shift linkage motion. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash and set Shift linkage control to Conserving port.

Kinetic friction coefficient at the contact interface between the ring and hub teeth. This coefficient characterizes the dissipative force that resists shift linkage motion due to tooth-to-tooth contact during clutch engagement and disengagement.

Greater coefficient values correspond to greater energy dissipation during shift linkage motion. The value must be greater than zero.

Dependencies

To enable this parameter, set:

  • Torque transmission model to Dynamic with backlash

  • Shift linkage control to Conserving port

Engagement Conditions

Direction the shift linkage must travel in to engage the clutch.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash.

Relative angular velocity between the ring and the hub above which the clutch cannot engage. The value is specific to the specific gearbox or transmission. Minimizing the value helps avoid high dynamic impact during engagement. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash.

Overlap length between the ring and hub teeth along the common longitudinal axis. The clutch engages when the tooth overlap is greater than this value. The clutch remains disengaged until the tooth overlap by at least this length. The value must be greater than zero.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization or Dynamic with backlash and set Shift linkage control to Conserving port.

Initial Conditions

Clutch state at the start of simulation:

  • off — Clutch transmits zero torque between the ring and the hub.

  • on — Clutch transmits torque between the ring and the hub.

Shift linkage position at simulation time zero. The clutch is disengaged when this value is between zero and the sum of the ring-hub clearance.

Dependencies

To enable this parameter, set:

  • Torque transmission model to Dynamic with backlash

  • Thermal model to Omit

  • Shift linkage control to Conserving port

Rotation angle between the ring and the hub at simulation time zero. This angle determines whether the ring and hub teeth can engage. The initial offset angle must satisfy these conditions:

  • If the clutch initial state is disengaged, the initial offset angle must fall in the range

    180°Nϕ0+180°N,

    where N is the number of teeth present in the ring or the hub. The two components contain the same number of teeth.

  • If the clutch initial state is engaged, the initial offset angle must fall in the range

    δ2ϕ0+δ2,

    where δ is the backlash angle between the ring and hub teeth.

Dependencies

To enable this parameter, set Torque transmission model to Dynamic with backlash, and set Thermal port to Omit.

Thermal Port

Thermal energy required to change the component temperature by a single degree. The greater the thermal mass, the more resistant the component is to temperature change.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Component temperature at the start of simulation. The initial temperature alters the component efficiency by adjusting the starting meshing or friction losses.

Dependencies

To enable this parameter, set Torque transmission model to Friction clutch approximation - Suitable for HIL and linearization, and set Thermal port to Model.

Extended Capabilities

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

Version History

Introduced in R2011a

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