LIBRARY
PlanarMechanics.examples.excavator.PlanarCylinderMount
Mounts a translational actuator between two planar frames as a line force element.
The flange position equals the distance between the two frame origins minus s_offset, so a translational actuator (such as a hydraulic cylinder) connected to flange acts along the straight line between the anchor points. A positive flange force pushes the anchors apart. The mount is massless and applies no torque; the actuator inertia acts along the line direction only, which is the standard approximation for cylinder-driven linkages.
An assertion guards the flange position against leaving the interval [0, stroke] (with a small margin for end-stop compliance), where the attached cylinder model is valid; a chamber volume of a DoubleActingCylinder would become non-positive outside it.
The component renders a cylinder barrel anchored at frame_a and a piston rod reaching back from frame_b, overlapping mid-stroke.
This component extends from MultibodyComponents.Renderable
Usage
MultibodyComponents.PlanarMechanics.examples.excavator.PlanarCylinderMount(render=true, color=[0.85, 0.75, 0.15, 1.0], specular_coefficient=1.5, s_offset=1.0, stroke=1.0, guard_margin=1e-3, barrel_radius=0.05, rod_radius=0.025, barrel_fraction=0.62, rod_fraction=0.55, rod_color=[0.55, 0.57, 0.6, 1.0], z_position=0)
Parameters:
| Name | Description | Units | Default value |
|---|---|---|---|
render | – | true | |
color | – | [0.85, 0.75, 0.15, 1.0] | |
specular_coefficient | – | 1.5 | |
s_offset | Anchor distance at zero flange position | m | 1.0 |
stroke | Stroke of the attached actuator, bounding the valid flange position | m | 1.0 |
guard_margin | Allowed excursion beyond the stroke before the guard assertion fires | m | 1e-3 |
barrel_radius | Radius of the rendered barrel | – | 0.05 |
rod_radius | Radius of the rendered piston rod | – | 0.025 |
barrel_fraction | Fraction of the anchor distance covered by the barrel in animations | – | 0.62 |
rod_fraction | Fraction of the anchor distance covered by the rod in animations | – | 0.55 |
rod_color | Color of the rendered piston rod | – | [0.55, 0.57, 0.6, 1.0] |
z_position | z-position of the shapes in animations | – | 0 |
Connectors
frame_a- Coordinate system (2-dim.) fixed to the component with one cut-force and cut-torque.
All variables are resolved in the planar world frame. (Frame2D)
frame_b- Coordinate system (2-dim.) fixed to the component with one cut-force and cut-torque.
All variables are resolved in the planar world frame. (Frame2D)
flange- This connector represents a mechanical flange with position and force as the potential and flow variables, respectively. (Flange)
Variables
| Name | Description | Units |
|---|---|---|
l | Distance between the frame origins | m |
ex | x-component of the unit vector from frame_a to frame_b | – |
ey | y-component of the unit vector from frame_a to frame_b | – |
Behavior
Source
dyad
"""
Mounts a translational actuator between two planar frames as a line force
element.
The flange position equals the distance between the two frame origins minus
`s_offset`, so a translational actuator (such as a hydraulic cylinder) connected
to `flange` acts along the straight line between the anchor points. A positive
flange force pushes the anchors apart. The mount is massless and applies no
torque; the actuator inertia acts along the line direction only, which is the
standard approximation for cylinder-driven linkages.
An assertion guards the flange position against leaving the interval
`[0, stroke]` (with a small margin for end-stop compliance), where the attached
cylinder model is valid; a chamber volume of a `DoubleActingCylinder` would
become non-positive outside it.
The component renders a cylinder barrel anchored at `frame_a` and a piston rod
reaching back from `frame_b`, overlapping mid-stroke.
"""
component PlanarCylinderMount
extends MultibodyComponents.Renderable(color = [0.85, 0.75, 0.15, 1.0])
frame_a = Frame2D() {
"Dyad": {
"placement": {
"diagram": {"iconName": "default", "x1": -50, "y1": 450, "x2": 50, "y2": 550, "rot": 0}
},
"tags": []
}
}
frame_b = Frame2D() {
"Dyad": {
"placement": {
"diagram": {"iconName": "default", "x1": 950, "y1": 450, "x2": 1050, "y2": 550, "rot": 0}
},
"tags": []
}
}
"Flange of the translational actuator acting between the frames"
flange = Flange() {
"Dyad": {
"placement": {
"diagram": {"iconName": "default", "x1": 450, "y1": -50, "x2": 550, "y2": 50, "rot": 0}
},
"tags": []
}
}
"Barrel visualization anchored at frame_a"
barrel_shape = MultibodyComponents.CylinderShape(render = render, color = color, r = [frame_a.x, frame_a.y, z_position], length_direction = [ex, ey, 0], width_direction = [0, 0, 1], length = barrel_fraction * l, width = 2 * barrel_radius, height = 2 * barrel_radius)
"Piston rod visualization anchored at frame_b"
rod_shape = MultibodyComponents.CylinderShape(render = render, color = rod_color, r = [frame_b.x, frame_b.y, z_position], length_direction = [-ex, -ey, 0], width_direction = [0, 0, 1], length = rod_fraction * l, width = 2 * rod_radius, height = 2 * rod_radius)
"Anchor distance at zero flange position"
parameter s_offset::Length = 1.0
"Stroke of the attached actuator, bounding the valid flange position"
parameter stroke::Length = 1.0
"Allowed excursion beyond the stroke before the guard assertion fires"
parameter guard_margin::Length = 1e-3
"Radius of the rendered barrel"
parameter barrel_radius::Real = 0.05
"Radius of the rendered piston rod"
parameter rod_radius::Real = 0.025
"Fraction of the anchor distance covered by the barrel in animations"
parameter barrel_fraction::Real = 0.62
"Fraction of the anchor distance covered by the rod in animations"
parameter rod_fraction::Real = 0.55
"Color of the rendered piston rod"
parameter rod_color::Real[4] = [0.55, 0.57, 0.6, 1.0]
"z-position of the shapes in animations"
parameter z_position::Real = 0
"Distance between the frame origins"
variable l::Length
"x-component of the unit vector from frame_a to frame_b"
variable ex::Real
"y-component of the unit vector from frame_a to frame_b"
variable ey::Real
relations
l = sqrt((frame_b.x - frame_a.x) ^ 2 + (frame_b.y - frame_a.y) ^ 2)
ex = (frame_b.x - frame_a.x) / l
ey = (frame_b.y - frame_a.y) / l
flange.s = l - s_offset
# A positive flange force pushes the anchors apart (power balance:
# flange.f * der(flange.s) + frame_a.f * v_a + frame_b.f * v_b = 0)
frame_a.fx = flange.f * ex
frame_a.fy = flange.f * ey
frame_a.fx + frame_b.fx = 0
frame_a.fy + frame_b.fy = 0
frame_a.tau = 0
frame_b.tau = 0
assert(flange.s >= -guard_margin and flange.s <= stroke + guard_margin, "Piston extension outside the actuator stroke; the cylinder model is invalid there (a chamber volume becomes non-positive). Increase the cylinder length/stroke or adjust the commanded trajectory.")
metadata {
"Dyad": {"icons": {"default": "dyad://MultibodyComponents/PlanarCylinderMount.svg"}}
}
endFlattened Source
dyad
"""
Mounts a translational actuator between two planar frames as a line force
element.
The flange position equals the distance between the two frame origins minus
`s_offset`, so a translational actuator (such as a hydraulic cylinder) connected
to `flange` acts along the straight line between the anchor points. A positive
flange force pushes the anchors apart. The mount is massless and applies no
torque; the actuator inertia acts along the line direction only, which is the
standard approximation for cylinder-driven linkages.
An assertion guards the flange position against leaving the interval
`[0, stroke]` (with a small margin for end-stop compliance), where the attached
cylinder model is valid; a chamber volume of a `DoubleActingCylinder` would
become non-positive outside it.
The component renders a cylinder barrel anchored at `frame_a` and a piston rod
reaching back from `frame_b`, overlapping mid-stroke.
"""
component PlanarCylinderMount
parameter render::Boolean = true
parameter color::Real[4] = [0.5, 0.5, 0.5, 1.0]
parameter specular_coefficient::Real = 1.5
frame_a = Frame2D() {
"Dyad": {
"placement": {
"diagram": {"iconName": "default", "x1": -50, "y1": 450, "x2": 50, "y2": 550, "rot": 0}
},
"tags": []
}
}
frame_b = Frame2D() {
"Dyad": {
"placement": {
"diagram": {"iconName": "default", "x1": 950, "y1": 450, "x2": 1050, "y2": 550, "rot": 0}
},
"tags": []
}
}
"Flange of the translational actuator acting between the frames"
flange = Flange() {
"Dyad": {
"placement": {
"diagram": {"iconName": "default", "x1": 450, "y1": -50, "x2": 550, "y2": 50, "rot": 0}
},
"tags": []
}
}
"Barrel visualization anchored at frame_a"
barrel_shape = MultibodyComponents.CylinderShape(render = render, color = color, r = [frame_a.x, frame_a.y, z_position], length_direction = [ex, ey, 0], width_direction = [0, 0, 1], length = barrel_fraction * l, width = 2 * barrel_radius, height = 2 * barrel_radius)
"Piston rod visualization anchored at frame_b"
rod_shape = MultibodyComponents.CylinderShape(render = render, color = rod_color, r = [frame_b.x, frame_b.y, z_position], length_direction = [-ex, -ey, 0], width_direction = [0, 0, 1], length = rod_fraction * l, width = 2 * rod_radius, height = 2 * rod_radius)
"Anchor distance at zero flange position"
parameter s_offset::Length = 1.0
"Stroke of the attached actuator, bounding the valid flange position"
parameter stroke::Length = 1.0
"Allowed excursion beyond the stroke before the guard assertion fires"
parameter guard_margin::Length = 1e-3
"Radius of the rendered barrel"
parameter barrel_radius::Real = 0.05
"Radius of the rendered piston rod"
parameter rod_radius::Real = 0.025
"Fraction of the anchor distance covered by the barrel in animations"
parameter barrel_fraction::Real = 0.62
"Fraction of the anchor distance covered by the rod in animations"
parameter rod_fraction::Real = 0.55
"Color of the rendered piston rod"
parameter rod_color::Real[4] = [0.55, 0.57, 0.6, 1.0]
"z-position of the shapes in animations"
parameter z_position::Real = 0
"Distance between the frame origins"
variable l::Length
"x-component of the unit vector from frame_a to frame_b"
variable ex::Real
"y-component of the unit vector from frame_a to frame_b"
variable ey::Real
relations
l = sqrt((frame_b.x - frame_a.x) ^ 2 + (frame_b.y - frame_a.y) ^ 2)
ex = (frame_b.x - frame_a.x) / l
ey = (frame_b.y - frame_a.y) / l
flange.s = l - s_offset
# A positive flange force pushes the anchors apart (power balance:
# flange.f * der(flange.s) + frame_a.f * v_a + frame_b.f * v_b = 0)
frame_a.fx = flange.f * ex
frame_a.fy = flange.f * ey
frame_a.fx + frame_b.fx = 0
frame_a.fy + frame_b.fy = 0
frame_a.tau = 0
frame_b.tau = 0
assert(flange.s >= -guard_margin and flange.s <= stroke + guard_margin, "Piston extension outside the actuator stroke; the cylinder model is invalid there (a chamber volume becomes non-positive). Increase the cylinder length/stroke or adjust the commanded trajectory.")
metadata {
"Dyad": {"icons": {"default": "dyad://MultibodyComponents/PlanarCylinderMount.svg"}}
}
endTest Cases
No test cases defined.
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