23.3. Cylindrical Joint¶
The Cylindrical Joint (
) removes all but two DOF (degrees of freedom) and allows the Rigid Body to rotate around the selected axis as well as travel along it.
As with all the joints, there are two ways of attaching the Cylindrical joint:
Attach it directly to an edge or an axis of a solid belonging to a Rigid Body, which attaches the joint between the Rigid Body and the world.
Attach it between two separate solids (each belonging to a separate Rigid Body).
23.3.1. Usage¶
In the first case you simply select the cylindrical tool from the ribbon menu and left-click on an edge or an axis of the Rigid Body you wish to add a joint to, a yellow Cylindrical icon will appear on the edge or axis. See Joint status.
In the second case where you wish to join two Rigid Bodies with a cylindrical joint you simply select the Cylindrical joint from the ribbon menu. Then, Ctrl-click somewhere on one of the Rigid Bodies, and then click the edge or axis on the other Rigid Body that the cylindrical should rotate around. A purple Cylindrical icon will appear on the edge or axis. See Joint status.
23.3.2. Properties¶
When a cylindrical joint (or multiple) is selected the properties of the joint can be changed from the properties tab.
23.3.2.1. Joint Properties¶
Enable: Specifies whether the joint is enabled or not.
Collision between Rigid Bodies: Specifies if there can be contacts generated between the two attached rigid bodies. Default is off. If collision is enabled, there might be jamming effects if the two bodies have overlapping geometry.
Type: Type of joint.
Solve type: Specifies which solver that will solve this joint.
Direct And Iterative: (Default), both the direct AND the iterative solver will see this joint. To get stable friction with the Split solver type for Material Pairs, both the iterative and the direct solver must see the joint.
Iterative - Only the iterative solver will see this joint. Will lead to instabilities for large mass ratios.
Direct - Only the direct solver will see this joint. This might lead to artifacts when involving a Material Pair with Split solve type.
Component1: Name of the first component associated to this joint.
Component2: Name of the second component associated to this joint.
Rigid Body1: Name of the first Rigid Body associated to this joint.
Rigid Body2: Name of the second Rigid Body associated to this joint.
Reverse direction: Visible only if joint is attached to two bodies. Will swap the two attached Rigid Bodies, effectively flip the direction of the joint.
Angular Position: The current position of the angular part of this cylindrical joint.
Linear Position: The current position of the linear part of this cylindrical joint.
Is Attached: A property that is set to true when the joint is directly attached to an edge/axis on a solid. When the joint is created, it is always directly attached to an edge/axis on a solid. If the solid is moved, the joint will follow the solid. However, if the joint is moved individually from the solid, this property is changed to false. This means that the joint will no longer follow the solid when the solid is moved, but will remain at its current world location. To reset the joint’s world position to the original solid position, set this flag to true.
23.3.2.2. Elasticity¶
Elasticity specifies the “stiffness” of the remaining degrees of freedom for the joint. The elasticity is specified in a local coordinate system relative to the constraint axis.
Translation X,Y: Specifies elasticity in the two remaining translational DOF.
Rotation X,Y: Specifies elasticity in the two remaining rotational DOF.
23.3.2.3. Angular Internal Friction¶
Specifies properties for the Internal Friction in the cylindrical joint around its axis. An internal friction will dissipate energy from the cylindrical joint, see Internal Friction.
Enable: Specifies whether the internal friction is enabled or not.
Static Friction Force Reverse Direction: The internal friction includes a setting for minimal static friction force, meaning there is a friction resistance even with the Coefficient of Friction set to zero. The static friction have one value for the reverse direction and one value for the forward direction.
Static Friction Force Forward Direction: The internal friction includes a setting for minimal static friction force, meaning there is a friction resistance even with the Coefficient of Friction set to zero. The static friction have one value for the reverse direction and one value for the forward direction.
Coefficient of Friction: The Coefficient of Friction. For the friction condition to be dimensionally correct, the axle radius should be included in the Coefficient of Friction, \(\tau_{friction} \leq \mu r F_{normal}\), where the given Coefficient of Friction should be \(\mu r\).
Non-Linear Friction Force Modeling: This mode is similar to direct friction for contacts and will affect the performance but will also increase the accuracy of the simulation, see Non-Linear Force Modeling.
23.3.2.4. Angular Motor¶
Properties for the motor for the angular part of the cylindrical joint. It has the same properties as a motor for a hinge.
23.3.2.5. Angular Spring¶
Properties for the spring for the angular part of the cylindrical joint. It has the same properties as a Spring.
23.3.2.6. Angular Range¶
Properties for the range for the angular part of the cylindrical joint. It has the same properties as a range for a hinge.
23.3.2.7. Linear Internal Friction¶
Specifies properties for the Internal Friction in the cylindrical joint along its axis. An internal friction will dissipate energy from the cylindrical joint, see Internal Friction.
Enable: Specifies whether the internal friction is enabled or not.
Static Friction Force Reverse Direction: The internal friction includes a setting for minimal static friction force, meaning there is a friction resistance even with the Coefficient of Friction set to zero. The static friction have one value for the reverse direction and one value for the forward direction.
Static Friction Force Forward Direction: The internal friction includes a setting for minimal static friction force, meaning there is a friction resistance even with the Coefficient of Friction set to zero. The static friction have one value for the reverse direction and one value for the forward direction.
Coefficient of Friction: The Coefficient of Friction (\(\mu\)), \(F_{friction} \leq \mu F_{normal}\).
Non-Linear Friction Force Modeling: This mode is similar to direct friction for contacts and will affect the performance but will also increase the accuracy of the simulation, see Non-Linear Force Modeling.
23.3.2.8. Linear Motor¶
Properties for the motor for the linear part of the cylindrical joint. It has the same properties as a motor for a prismatic.
23.3.2.9. Linear Spring¶
Properties for the spring for the linear part of the cylindrical joint. It has the same properties as a spring for a prismatic.
23.3.2.10. Linear Range¶
Properties for the range for the linear part of the cylindrical joint. It has the same properties as a range for a prismatic.
23.3.2.11. Current Properties¶
When a simulation is recorded, some information is available as read only properties. These include current angle/position and and applied torque/force for spring, range and motor (if enabled).
