Prismatic joint where the translational distance is computed from a length constraint (1 degree-of-freedom, no potential state)


This information is part of the Modelica Standard Library maintained by the Modelica Association.

Joint where frame_b is translated along axis n which is fixed in frame_a. The two frames coincide when "s + s_offset = 0", where "s_offset" is a parameter with a zero default and "s" is the relative distance.

This variant of the prismatic joint is designed to work together with a length constraint in a kinematic loop. This means that the relative distance "s" of the joint is computed such that the length constraint is fulfilled.

Usually, this joint should not be used by a user of the MultiBody library. It is only provided to built-up the Modelica.Mechanics.MultiBody.Joints.Assemblies.JointXYZ joints.

In releases before version 3.0 of the Modelica Standard Library, it was possible to activate the force projection equation (= cut-force projected to the translation axis must be identical to the driving force of flange axis) via parameter axisForceBalance. This is no longer possible, since otherwise this model would not be "balanced" (= same number of unknowns as equations). Instead, when using this model in version 3.0 and later versions, the force in the length constraint component (Joints.SphericalSpherical or Joints.UniversalSpherical) must be calculated such that the driving force in direction of the translation axis is (RC shall be the name of the instance of PrismaticWithLengthConstraint):

    0 = RC.axis.f + RC.e*RC.frame_b.f;

If this equation is used, usually the force in the length constraint and the second derivative of the prismatic distance will be part of a linear algebraic system of equations. In some cases it is possible to solve this system of equations locally, i.e., provide the rod force directly as function of the prismatic constraint force. In any case, this projection equation or an equivalent one has to be provided via variable "constraintResidue" in the "Advanced" menu of "Joints.SphericalSpherical" or "Joints.UniversalSpherical".

Parameters (10)


Value: true

Type: Boolean

Description: = true, if animation shall be enabled



Type: Position (m)

Description: Fixed length of length constraint


Value: {1, 0, 0}

Type: Axis

Description: Axis of translation resolved in frame_a (= same as in frame_b)


Value: 0

Type: Position (m)

Description: Relative distance offset (distance between frame_a and frame_b = s(t) + s_offset)


Value: 0

Type: Position (m)

Description: Select the configuration such that at initial time |s(t0)-s_guess| is minimal


Value: {0, 1, 0}

Type: Axis

Description: Vector in width direction of box, resolved in frame_a


Value: world.defaultJointWidth

Type: Distance (m)

Description: Width of prismatic joint box


Value: boxWidth

Type: Distance (m)

Description: Height of prismatic joint box



Type: Boolean

Description: Selection of one of the two solutions of the non-linear constraint equation


Value: Modelica.Math.Vectors.normalizeWithAssert(n)

Type: Real[3]

Description: Unit vector in direction of translation axis, resolved in frame_a

Inputs (2)


Default Value: Modelica.Mechanics.MultiBody.Types.Defaults.JointColor

Type: Color

Description: Color of prismatic joint box


Default Value: world.defaultSpecularCoefficient

Type: SpecularCoefficient

Description: Reflection of ambient light (= 0: light is completely absorbed)

Connectors (6)


Type: Frame_a

Description: Coordinate system a fixed to the component with one cut-force and cut-torque


Type: Frame_b

Description: Coordinate system b fixed to the component with one cut-force and cut-torque


Type: Flange_a

Description: 1-dim. translational flange that drives the joint


Type: Flange_b

Description: 1-dim. translational flange of the drive bearing


Type: RealInput[3]

Description: Position vector from frame_a to frame_a side of length constraint, resolved in frame_a of prismatic joint


Type: RealInput[3]

Description: Position vector from frame_b to frame_b side of length constraint, resolved in frame_b of prismatic joint

Components (2)


Type: World


Type: Shape

Used in Components (2)



Universal - spherical - prismatic joint aggregation (no constraints, no potential states)



Spherical - spherical - prismatic joint aggregation with mass (no constraints, no potential states)