Revolute Joint


Symbol:
Identifier: Mechanics.MechanicsMBS.Joints.RevoluteJoint
Version: 3.9
File: MechanicsMBS.cat
Connectors: Kinetic MBS Connector ctr1 Connectable to kinematic MBS connector.
Kinematic MBS Connector ctr2 Connectable to kinetic MBS connectors.
Position: (see Table 1 in main chapter Initial Position of the Elements)
Parameters: Definition of Joint Revolution Axis
Axis of Rotation axis Defaults to Z-Axis.
Axis of Rotation n Only visible if axis = Input.
Initial Values
Initial Rel. Angle phiRel0
Initial Rel. Angular Velocity omRel0
Preset of Torque (Drive) or Motion Quantities around the Axis of Revolution
Preset of Drive kindD
  • "at 1D Connectors (or no Preset)"
  • "Torque"
  • "Angle"
  • "Angular Velocity"
Torque T Only visible if kindD=="Torque"
Rel. Angle Preset phiRelPre Only visible if kindD=="Angle"
Rel. Angular Velocity Preset omRelPre Only visible if kindD=="Angular Velocity"t
Friction: Consideration of Friction around Joint Revolution Axis
Consideration of Friction withFriction Defaults to false.
Rigid Friction with kindF Only visible if withFriction = true. Defaults to Continuous Transition.
Static Friction Coefficient mu0 Only visible if withFriction = true and kindF = Stick-Slip.
Sliding Friction Coefficient mu Only visible if withFriction = true.
Limit Angular Velocity Difference domL Only visible if withFriction = true and kindF = Continuous Transition.
Friction Radius rf Only visible if withFriction = true. Defaults to Visualization Radius rd.
End Stop: Consideration of an internal End Stop around Joint Revolution Axis
End Stop withStop Defaults to false.
End Stop 1 phiRel1 Only visible if withStop = true.
End Stop 2 phiRel2 Only visible if withStop = true.
Model mode Only visible if withStop = true. Defaults to Elastic End Stop.
Kind of Impact kind Only visible if withStop = true and mode = Rigid End Stop. Defaults to Plastic.
Coefficient of Restitution ci Only visible if withStop = true, mode = Rigid End Stop and kind = By Coefficient of Restitution.
Stiffness 1 k1 Only visible if withStop = true and mode = Elastic End Stop.
Stiffness 2 k2 Only visible if withStop = true and mode = Elastic End Stop.
Damping 1 b1 Only visible if withStop = true and mode = Elastic End Stop.
Damping 2 b2 Only visible if withStop = true and mode = Elastic End Stop.
Advanced: Advanced Settings for Joint Friction and End Stop
Advanced Settings adv Only visible if withStop = true and mode = Rigid End Stop or if withFriction = true.
Min. Separation Torque eps_Ti Only visible if withStop = true and mode = Rigid End Stop.
Max. Speed After Impact for Permanent Contact eps_dom Only visible if withStop = true and mode = Rigid End Stop.
Minimum Separation Impact eps_dI Only visible if withStop = true and mode = Rigid End Stop or withFriction = true and kindF = Stick-Slip.
Transition Shape of Force of Sliding Friction kindTrans Only visible if withFriction = true and kindF = Continuous Transition. Defaults to Gevrey Approach.
Shape Coefficient (Transition Shape) eps_sigma Only visible if withFriction = true and kindF = Continuous Transition.
Relative Minimum Difference of the Friction Torques dTfrel Only visible if withFriction = true and kindF = Stick-Slip.
Minimum Separation Speed Difference eps_domsl Only visible if withFriction = true and kindF = Stick-Slip.
Visualization: Color and Transparency
RGB Color color
Transparency alpha
Geometry (additional)
Radius rd
Length along Axis of Rotation lz
Rel. Kinematic Results: Relative Motion Quantities around Joint Axis
Rel. Rotation Angle phiRel
Rel. Angular Velocity omRel
Rel. Angular Acceleration alpRel
Kinematic Results: (see Table 1 in Joints Kinematic Results)
Kinetic Results: Internal Forces and Torques in Element Coordinates
Internal Force Fi
Internal Torque Ti
Magnitude of Normal Force FnAbs
Moment of Inertia and Acceleration Torque w.r.t. Rotation Axis
Moment of Inertia w.r.t. Axis of Rotation J
Acceleration Torque w.r.t. Axis of Rotation Ta
Result Quantities if Joint Friction is considered
Internal Torque due to Friction Tf Only visible if withFriction = true.
State of Friction sf Only visible if withFriction = true.
Power Loss due to Friction Pl Only visible if withFriction = true.
Result Quantities if an End Stop within the Joint is considered
Internal Torque due to End Stop TStop Only visible if withStop = true.
State of End Stop stop Only visible if withStop = true.
  • Representiert einen rotatorischen Freiheitsgrad um eine wählbare Achse
  • Optional mit Reibung und Endanschlägen
  • Der Antrieb kann durch rotatorische 1D-Modelle, Drehmomente oder Bewegungsgrößen definiert werden
  • Represents one rotational degree of freedom about a selectable axis
  • Optionally with friction and end stops
  • Actuation can be defined by rotational 1D models, torques or motion quantities

Description:

This element models an actuated revolute joint. It represents one rotational degree of freedom about a selectable axis. The revolute joint generates two potential state variables for the relative angle phiRel and the relative angular velocity omRel about the selected axis. Both motion quantities are measured w.r.t. to the input frame at ctr1.

Additionally, the model is able to represent a motion preset about the DoF or a torque preset about this axis. It it also possible to take friction about the revolution axis into account.

The revolte joint features two additional Rotational Connectors connectable to elements of the Rotational Mechanics library. Connector ctrR1 represents the mounting and connector ctrR2 represents the driving flange.

Parameters:

Position:

See Joints Parameters Position for more information.

It is possible to either choose the X-, Y- or Z-Axis as axis of rotation or freely set the direction vector n of the axis (if axis = Input). Axis vector n is resolved in local coordinates and will be internally normalized.

Initial Values:

The initial motion quantities (joint state) are determined by the initial angle phiRel0 and the initial angular velocity omRel0 around the axis of revolution.

Preset of Torque (Drive) or Motion Quantities around Axis of Revolution:

You can select between 4 possibilities of drive models (enumeration kindD):

  • kindD=="at 1D Connectors (or no Preset)": connect a drive model at the 1D-mechanical connectors ctrR1 and ctrR2
  • kindD=="Torque": enter a driving torquerce T (parameter
  • kindD=="Displacement": enter an angle preset phiRelPre, measured w.r.t. to the pin point frame atr ctr1
  • kindD=="Velocity": enter an angular velocity preset omRelPre, measured w.r.t. to the pin point frame atr ctr1

End Stop:

By default the joint models an unlimited degree of freedom. Optionally (withStop = true) the joint model is able to consider an internal end stop model for a limitation of the body motion. This can be selected in order to physically restrict the angle phiRel within the interval . The end stop can be modeled either as a rigid or as an elastic end stop. For a detailed description of the models and the corresponding parameters and advanced parameters, see the help chapter Mechanics Translation End Stop.

Note: This option is only available if there is no preset of motion quantities inside the element (kindD)

Friction:

Optional joint friction can be taken into account by the parameter withFriction. For a detailed description of the friction models, see the help Mechanics Translation Elastic Friction or ... Rigid Friction. These chapters describe also the corresponding parameters and advanced parameters of the friction models.

The parameter Tst, the Static friction torque, for the friction models is computed by
where is the normalized axis of rotation.
The Sliding friction torque parameter Tsl is similarly computed by
.

Note: This option is ponly available if there is no preset of motion quantities inside the element (kindD)

Visualization:

This element type is represented by a cylinder in 3D View. Its shape is given by radius rd and length lz.

Results:

Kinematic Results:

See Joints Results Kinematic Results for more information.

Relative Kinematic Results:

The rotation angle phiRel around axis n gives the relative motion between two connected elements. Furthermore, the time derivatives of the relative rotation angle, i.e. the relative angular velocity omRel and the relative angular acceleration alpRel are available as results.

Kinetic Results:

The internal force Fi and the internal torque Ti are computed in joint coordinates. FnAbs is the magnitude of normal force which is used for the calculation of friction torque. The quantity J is the articulated moment of inertia of all subsequent bodies projected onto the axis n of rotation. Subsequent is defined by means of the kinematic successor relationship of the MBS connection, i.e. those bodies are included that are connected to the kinematic MBS connector ctr2 by joints and bodies excluding connections by elastic bodies, constraints and force elements. The moment of inertia J is required to be non-zero otherwise an assertion is thrown. The articulated acceleration torque Ta is the corresponding torque with respect to the axis n of rotation.

If end stop behavior is modeled the stop state stop and the internal stop torque TStop are available as results, too. The internal stop torque TStop is also included by the articulated acceleration torque Ta.

If friction behavior is modeled the state of friction sf, the internal friction torque Tf and the power loss Pl are available as results, too. The internal friction torque Tf is also included by the articulated acceleration torque Ta.

Remarks:

The assertion "Moment of inertia is zero." is thrown if no articulated moment of inertia J with respect to the axis n of rotation is modeled at the kinematic MBS connector ctr2.