Cosmos work motion essential
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Transcript of Cosmos work motion essential
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
COSMOSMotion Essentials Training
COSMOSMotion 2007
2 © 2007 SolidWorks Corp. Confidential.
About this course
Prerequisites
Course Design Philosophy
Using this book
A note about files
Conventions used in this book
Class Introductions
3 © 2007 SolidWorks Corp. Confidential.
COSMOSWorks
Adv. Professional
Professional
Design Validation Products
Designer
Static
Vibration
& Buckling Thermal
Drop Test
Fatigue
Nonlinear
Post-dynamics
COSMOSEMS
Electromagnetic
COSMOSMotion
COSMOSFloWorks
Flow Simulation
Optimization
4 © 2007 SolidWorks Corp. Confidential.
What is Motion Simulation ?
Study of moving systems or mechanisms
Motion of a system is determined by
– Mechanical joints connecting the parts
– The mass and inertia properties of the components
– Applied forces to the system (Dynamics)
– Driving motions (Motors or Actuators)
– Time
5 © 2007 SolidWorks Corp. Confidential.
Mechanism types
Kinematic System
– Movement of part(s) under enforced or constrained motion
– Fully controlled and only one possible motion result irrespective of force and mass
– Zero degree of freedom
Dynamic System
– Movement of part(s) under free motion subject to forces
– Partially controlled and infinite number of results depending on forces
– Greater than zero degrees of freedom
6 © 2007 SolidWorks Corp. Confidential.
Understanding Basics
Mass and Inertia – Newton’s First Law
– Conservation of momentum
Degrees of freedom – Rigid body
– Grounded parts
– Moving parts
Constraints – Restrictions placed on a part’s
movement in specific degrees of freedom
– Mechanical joints are connections that restrict the movement of one part to another
Joint motion
Gravity
x
y Pendulum restrained
to pivot about mounting
point
7 © 2007 SolidWorks Corp. Confidential.
Mapping of SolidWorks assembly mates (constraints) to COSMOSMotion joints.
100+ ways of defining SolidWorks mates.
Basic constraint types are merged to simplified mechanical joints.
– One Orthogonal Concentric mate in SolidWorks becomes a Concentric joint.
– One Coincident and One Orthogonal Concentric mates in SolidWorks becomes a Revolute joint.
– One Point to Point coincident mate in SolidWorks becomes a spherical joint
Constraint Mapping
8 © 2007 SolidWorks Corp. Confidential.
User Interface
Pull down menu
Intellimotion builder
Motion toolbar
Intellimotion browser
9 © 2007 SolidWorks Corp. Confidential.
User Interface
Pull down menu
Intellimotion builder
Motion toolbar
Intellimotion browser
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 1
Governor Mechanism
11 © 2007 SolidWorks Corp. Confidential.
Lesson 1: Topics
Introduction to the COSMOSMotion Feature Manager
Understand basic capabilities of COSMOSMotion
Run a Simulation
Create a result plot
12 © 2007 SolidWorks Corp. Confidential.
Lesson 1: Defining and Simulating a Mechanism
Parts
– Moving Parts
– Ground Parts
Constraints
– Joints
– Joint Primitives
– Cam Constraints
Forces
– Applied Forces
– Flexible Connectors
– Gravity
Results
Translational Distance
Collar and Slider.
Initial Distance : 345 mm
Slider Distance: 323 mm
Minumium Distance : 22 mm
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 2
Crankslider Mechanism
14 © 2007 SolidWorks Corp. Confidential.
Lesson 2: Topics
Create moving and ground parts
Review basic joint types in COSMOSMotion
Understand Automatic Constraint mapping
Apply motion to a joint
Create a result plot
15 © 2007 SolidWorks Corp. Confidential.
Lesson 2: Constraint Mapping Concept
1 Coincident and 1 concentric mates becomes a revolute joint
1 Concentric mate becomes a cylindrical joint
A point on a point coincident mate becomes a spherical joint
A point on an axis coincident mate becomes an Inline Joint
16 © 2007 SolidWorks Corp. Confidential.
Lesson 2: Results
Collar-1 not only translates along collar_shaft-1 but also rotates.
The rotation needs to be prevented
17 © 2007 SolidWorks Corp. Confidential.
Lesson 2: Motion on Joints
Joint Types Type of motion allowed Available options
under Motion On
list
Cylindrical Rotation and translation in one
direction
Rotate Z
Translate Z
Revolute Only Rotation in one direction Rotate Z
Translational Only Translation in one direction Translate Z
Spherical Rotations in all directions, No
translation
Rotate X
Rotate Y
Rotate Z
18 © 2007 SolidWorks Corp. Confidential.
Lesson 2: Results
Power Consumption in Mechanism
Why is Power Consumption negative
in some places?
Conversion:
Pound_force foot/sec to Watt
Pound_force foot/sec to HP
1 Pound_force foot/sec = 1.3558 W
1 Pound_force foot/sec = 0.00134 HP
1 ft = 12 in
4 pound_force foot/sec = 0.451933 W
4 pound_force foot/sec = 0.000447 HP
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 3
Piston Crankshaft Mechanism
20 © 2007 SolidWorks Corp. Confidential.
Lesson 3 Topics
Review basic joint types in COSMOSMotion
Create Mechanical Joints
Apply motion to a joint
Create and review results
21 © 2007 SolidWorks Corp. Confidential.
Lesson 3: Basic Joint Types
Joints used to constrain the relative motion of a pair of rigid bodies by physically connecting them.
Joint Primitives used to enforce standard geometric constraints
22 © 2007 SolidWorks Corp. Confidential.
Lesson 3: Joint definition
Location
Direction
23 © 2007 SolidWorks Corp. Confidential.
Lesson 3 Results
Torque required to drive the mechanism
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 4
Coupler
25 © 2007 SolidWorks Corp. Confidential.
Lesson 4 Topics
Simulate motion of gears using joint couplers
Joint coupler to associate the movement of one joint with another
Modeling gear-mate from SolidWorks model
Conversion
Convert RPM to deg/s
1 RPM = 360 degree
1 min = 60 s
100 RPM = 600 deg/s
26 © 2007 SolidWorks Corp. Confidential.
Lesson 4: Couplers
Any one of the following joint combinations will create
a coupler:
– Revolute-Revolute
– Revolute-Translational
– Revolute-Cylindrical
– Translational-Cylindrical
– Translational-Translational
– Cylindrical-Cylindrical
Only motion transfer. No load transfer
27 © 2007 SolidWorks Corp. Confidential.
Lesson 4: Coupler Definition
28 © 2007 SolidWorks Corp. Confidential.
Simulate Couplers using Gear Mate in SolidWorks
Lesson 4: Gear Mate in SolidWorks
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 5
Door Mechanism
30 © 2007 SolidWorks Corp. Confidential.
Lesson 5 Topics
Create springs and damper entities in COSMOSMotion
Attach different parts together to move them as a single entity
Constrain the motion of a cylindrical joint to achieve correct mechanism behavior
Modify springs and dampers to achieve desired design goals
31 © 2007 SolidWorks Corp. Confidential.
Lesson 5 Attaching Parts
Physically attach one part to another
Two parts will be welded or rigidly connected to one
another.
No relative motion between the two parts
Initial orientation between the two parts will be locked and
will be maintained throughout the simulation
32 © 2007 SolidWorks Corp. Confidential.
Lesson 5: Springs
Translational Spring Force = -k (X - X0)n + F0
Where:
k = Spring stiffness coefficient (always > 0)
X = Current distance between the spring connection points
X0 = Reference length of the spring (Free length)
n = Exponent defining spring characteristic
F0 = Reference force of the spring (preload)
Positive force repels the two parts.
Negative force attracts the two parts.
Similar force expression applies to Torsional Springs
33 © 2007 SolidWorks Corp. Confidential.
Lesson 5: Dampers
Translational Damper Force = c*vn
Where:
c - Translational damping coefficient
v - Current relative velocity between parts at the attachment points
n - Exponent.
Similar force expression applies to Torsional Dampers
34 © 2007 SolidWorks Corp. Confidential.
Lesson 5: Results
gas_piston-1 not only translates along gas_cylinder-1 but also rotates.
The rotation needs to be prevented
35 © 2007 SolidWorks Corp. Confidential.
Lesson 5: Results
Velocity goal is satisfied
Door does not stop in 30 seconds
Should we increase or decrease spring stiffness?
Spring stiffness: 1 N/mm
Damper Co-efficient: 5 N (sec/mm)
36 © 2007 SolidWorks Corp. Confidential.
Lesson 5: Results
Velocity goal is satisfied
Door stops in 30 seconds
Spring stiffness: 2 N/mm
Damper Co-efficient: 10 N (sec/mm)
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 6
Hatchback Mechanism
38 © 2007 SolidWorks Corp. Confidential.
Lesson 6 Topics
Create an Action Only force to simulate an
Change the mass properties of a part
Use Impact forces to control two parts from interfering each other
39 © 2007 SolidWorks Corp. Confidential.
Affect the dynamic behavior of a mechanism
Do not prohibit or prescribe motion and so do not add or remove degrees-of-freedom from your model.
Force Entities
– Translational and Torsional Springs
– Translational and Torsional Dampers
– Action-Only Forces/Moments
– Action-Reaction Forces/Moments
– Impact Forces
– Flexible Connectors
– Gravity
Lesson 6: Forces
40 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Force Definition
Force Type – Whether the loading is a force or
a moment.
Location
Direction – Along an axis defined by an
edge, plane or cylindrical surface.
– Along the line-of-sight between two points
Magnitude – Enter a pre-defined function
expression (step, harmonic, spline).
– Enter an equation directly into the Function Expression field using the library of built-in COSMOSMotion functions.
Cylinder Component
Bore Diameter: 0.49 in
Bore Radius : 0.245 in
Area: 0.19 sq. in
Pressure : 500 Psi
Force: 94.30 Lbs
41 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Action Only Force
42 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Material Properties
Adding Materials Modifying Material Properties
43 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Results
44 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Impact Forces
Intermittent force that is dependent on relative distance between two components).
Impact forces are used to simulate the collision between two parts.
As two parts approach within a specified distance, the impact force becomes active, and a force specified by the impact parameters is applied to both of the colliding parts.
The collision is dependent on the materials and geometry of the bodies colliding.
45 © 2007 SolidWorks Corp. Confidential.
Impact Force = Spring Force + Damping Force
Stiffness: Depends on material properties and curvature of interacting surfaces
Exponent: Determines impact force characteristic
Max Damping: Simulates energy loss in collision
Penetration: Depth at which maximum damping occurs.
Length: distance at which the impact force is activated (parts contact)
Lesson 6: Impact Parameters
46 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Impact Parameters
Good numbers for impact parameters:
Stiffness: 10000 lb/in 10000 N/mm
Exponent: 1.1-1.3 1.1-1.3
Damping: 0.1-100 lb-s/in 1-100
Penetration: 0.0001 in 0.01 mm
d cannot be specified as 0
Height of Piston: 0.95 in
Impact Distance Clearance Distance
1 in 0.05 in
0.95 in 0 in
0.9 in -0.05 in Components interfere
0.85 in -0.15 in
1.3 in 0.35 in
This values are linearly proportionaly due to the exponent input.
47 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Results
Translational displacement of the concentric joint between the piston and cylinder parts
Notice that the displacement is held at 8 inches
which means that the impact force does not
allow further translation between the parts
48 © 2007 SolidWorks Corp. Confidential.
Lesson 6: Results
Magnitude of the impact force applied
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 7
Contacts
50 © 2007 SolidWorks Corp. Confidential.
Lesson 7 Topics
Apply Point to curve contact
Apply Curve to curve contact
Apply 3D Contact
51 © 2007 SolidWorks Corp. Confidential.
Point-curve - Restricts a point on one rigid body to lie on a curve on a second rigid body.
Curve-curve - Constrains one curve to remain in contact with a second curve.
Intermittent curve-curve - Applies a force to prevent curves from penetrating each other. Only active if the parts are touching
3D Contact – Applies a force to prevent bodies from penetrating each other. Only active if the parts are touching
Lesson 7: Understanding Contacts
52 © 2007 SolidWorks Corp. Confidential.
Contact is similar to an impact force in that the material properties of the parts are used to define the contact parameters.
Contact differs from an impact force since any point along a curve or geometry is used in the contact
Contact simulates friction forces between parts.
Lesson 7: Impact Forces Vs Contacts
53 © 2007 SolidWorks Corp. Confidential.
Lesson 7: 3D Contact
Surface Representation of parts:
– Tessellated Geometry
Faster but less accurate in certain contact situations like point to surface or multiple contacts
– Precise Geometry
Longer simulation time but produces accurate results
Contact Containers
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 8
Railcar Mechanism
55 © 2007 SolidWorks Corp. Confidential.
Lesson 8: Topics
Apply Gravity force to the mechanism
Create an Action-Reaction force to accelerate the railcar
Learn some advanced plotting techniques in COSMOSMotion
56 © 2007 SolidWorks Corp. Confidential.
Lesson 8: Action Reaction Force
57 © 2007 SolidWorks Corp. Confidential.
Lesson 8: Results
Probing translational velocity plot of body-1
58 © 2007 SolidWorks Corp. Confidential.
Lesson 8: Results
Plotting multiple plots in the same XY graph
59 © 2007 SolidWorks Corp. Confidential.
Lesson 8: Results
Replacing X axis time scale with a desired results
quantity
Image courtesy of National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.
Lesson 9
Floor Jack Mechanism
61 © 2007 SolidWorks Corp. Confidential.
Lesson 9 Topics
Apply motion to a part
Use different types of motion functions
Make a design change and study mechanical advantage
62 © 2007 SolidWorks Corp. Confidential.
Lesson 9: Part Motion
63 © 2007 SolidWorks Corp. Confidential.
Lesson 9: Function Types
Constant
Step Function
d0 = Initial value of displacement
d1 = Final value of displacement
t0 = Start step time
t1 = Final step time
Harmonic
Amplitude; Frequency; Time Offset; Phase Shift; Average
64 © 2007 SolidWorks Corp. Confidential.
Lesson 9: Function Types
Spline
–You can use your own motion data to control your mechanism by importing data points.
–To import data points, they must be in a .TXT or .CSV file format.
–You may import an unlimited number of data points.
-20
0
20
40
60
80
100
0 1 2 3 4
Overshoot
0
20
40
60
80
100
0 1 2 3 4
Data Points
65 © 2007 SolidWorks Corp. Confidential.
Lesson 9: Results
Translational Displacement of the
cylinder joint connecting the
piston and cylinder
Force on handle
Force to move the piston. A very
small force is required to push the
handle. This gets amplified
internally at the piston cylinder
area