Rotational Detent

Double-sided, spring-loaded rotational detent

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Simscape / Driveline / Brakes & Detents / Rotational

  • Rotational Detent block

Description

The Rotational Detent block represents a double-sided, spring-loaded rotational detent.

The detent rod rotates over the detent case. The case has notches or magnets that create a net relative torque with the rod as the rod rotates. You can parameterize the block by using peak torque and notch width, or by using a table lookup. The block includes viscous damping and kinetic friction between the rod and case. You can set the friction to zero.

As the rod rotates over the case, the relative rotation, ϕ = ϕR – ϕC, induces a torque, τ. Depending on the setting of the Parameterization parameter, the torque is either defined by the peak torque and notch width, or by a table lookup that specifies relative rotation versus torque.

If you specify multiple detents, the detents have the same torque-relative rotation function.

Peak Torque and Notch Width

If you set Parameterization to By peak torque and notch width, the block ensures that the torque-relative rotation curve provides a continuous torque and torque derivative over the detent region. The peak torques are halfway between the detent center and detent edge, as shown in the figure.

By Table Lookup

If you set Parameterization to By table lookup, you can create an arbitrary function that relates torque to the relative rotation. Consider these best practices when creating the function.

  • To ensure that the detent conserves energy, the total integral of the torque-relative rotation curve, area under the curve, must be zero.

  • To stabilize simulation of the detent, avoid discontinuities in the torque-relative rotation function.

Assumption and Limitations

  • The block does not account for inertia. Add inertia terms externally to the R and C ports.

  • The kinetic friction is independent of the detent normal force.

Ports

Conserving

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Mechanical rotational conserving port associated with the rod.

Mechanical rotational conserving port associated with the case.

Thermal conserving port associated with heat flow.

Dependencies

To enable this port, set Thermal port to Model.

Parameters

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Detent Characteristics

Specification to use to parameterize the detent.

  • By peak torque and notch width — Specify detent characteristics by using the peak shear torque and the notch width.

  • By table lookup — Define the detent characteristics by using one-dimensional table lookup based on the relative displacement between the slider and case.

Peak shear torque inside the detent.

Dependencies

To enable this parameter, set Parameterization to By peak force and notch width.

Width of the region where the shear torque develops.

Dependencies

To enable this parameter, set Parameterization to By peak torque and notch width.

Relative displacement of the slider and case when simulation starts.

Vector of input relative rotations that corresponds to the values in the Torque vector parameter. This vector must be same the size as the Torque vector parameter. You must specify the displacements in increasing order.

Dependencies

To enable this parameter, set Parameterization to By table lookup.

Vector of input values for the shear torque. The elements in this vector correspond to the elements in the Relative rotation vector parameter.

Dependencies

To enable this parameter, set Parameterization to By table lookup.

Method to use for the lookup table breakpoint interpolation. The block uses the tablelookup function to model nonlinearity by using array data to map input values to output values. The approximation method that the function uses depends on the parameter setting:

  • Linear — Select this option for the lowest computational cost.

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

For more information, see tablelookup.

Dependencies

To enable this parameter, set Parameterization to By table lookup.

Spacing

Whether to space detents regularly or by angle vector:

  • Regularly spaced — Specify regular detent spacing according to the number of detents.

  • By angle vector — Specify detent spacing by custom intervals.

Number of identical, regularly spaced detents. The detents are evenly spaced from –180 to +180 degrees, with one detent centered at 0 degrees.

Dependencies

To enable this parameter, set Detent spacing to Regularly spaced.

Locations of the centers of the identical detents, as angles. The values must lie between –180 and +180 degrees. The minimum spacing between the detents must be greater than the value of the Notch width parameter.

Dependencies

To enable this parameter, set Detent spacing to By angle vector.

Friction

Viscous friction coefficient for the ball-notch contact.

Ratio by which to compute the kinetic friction. The kinetic friction is this ratio multiplied by the peak shear force.

Relative rotational velocity required for peak kinetic friction in the detent.

Thermal Port

Whether to enable the thermal port for the block. When you set this parameter to Model, the block enables port H.

Thermal energy required to change the component temperature by a unit increase. The thermal mass represents the ability of the detent to absorb and retain heat energy.

Dependencies

To enable this parameter, set Thermal port to Model.

Extended Capabilities

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

Version History

Introduced in R2011b

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See Also

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