1. WORKSHOP 3 Belt Modeling – Lawn Mower

3. Workshop Objectives Software Version Files Required
Learn how to create pulleys, belts and actuators.
Software Version
Adams
Files Required
lawn_mower_start.cmd
Located: exercise_dir/mod_03_lawnmower

4. Suggested Exercise Steps
Import File
Create Pulleys, Specify Method
Geometry Properties
Specify Materials
Pulley Connections
Pulley Outputs
Pulley Completion
Tensioners
Tensioner Properties
Tensioner Connections
Tensioner Completion
Create Belt
Belt Geometry
Belt Contact Settings
Belt Mass
Belt Wrapping Order
Belt Outputs & Completion
Simulation Setup
Simulate & Animate
Investigate System

5. Step 1. Import File To import the file: b a
Open Adams/View from the directory exercise_dir/mod_03_lawnmower.
Load the model file lawn_mower_start.cmd. b a

6. Step 2. Create Pulleys: a b c d e To create pulley:
Step1 of 11 (Type):
Click on Create Pulley icon under Belt ribbon.
Create Pulley dialog box will be displayed that consists of 11 steps.
Keep default values as shown below for Belt System and Pulley Set, and Select Poly-V Grooved as a Type.
Step 1:
Belt System Name: beltsys_1
Pulley Set Name : pulleyset_1
Type : Poly-V Grooved
Read a brief note about Poly-V Grooved belt system
Click on Next button to move on to Step 2 of 11. a b c d e

7. Step 2. Specify Method a b c Creating pulley: Step 2 of 11 (Method):
Select 2D Links as a Method.
Step 2:
Method : 2D Links
Read a brief note about Method – 2D Links.
Click on Next button to move on to Step 3 of 11. a b c

8. Step 3. Geometry Properties:
Creating pulley:
Step3 of 11 (Geometry-Pulleys):
Enter 3 in the field Number of Pulleys and hit Enter.
Select Axis of Rotation as Global Z
Click on tab “1” to enter Name motor_p for Pulley1
Browse and select motor_pulley marker of part motor_shaft in the field Center Location.
Enter 150 in the field Pulley pitch diameter
Step 3 -1:
Number of Pulleys: 3
Axis of Rotation: Global Z
Tab 1:
Pulley1 Name : motor_p
Center Location : motor_pulley
Pulley Width : 30
Pulley pitch diameter :150
Click on tab “2” to enter values for pulley2 a b f c d e

9. Step 3. Geometry Properties:
Creating pulley:
Step 3 of 11 (Geometry-Pulleys):
Enter Name left_p for Pulley2
Browse and select left_pulley marker of part left_blade_shaft in the field Center Location.
Enter 180 in the field Pulley pitch diameter
Step 3 -2:
Tab 2:
Pulley2 Name : left_p
Center Location : left_pulley
Pulley Width : 30
Pulley pitch diameter : 180
Click on tab “3” to enter values for pulley3 d a b c

10. Step 3. Geometry Properties:
Creating pulley:
Step 3 of 11 (Geometry-Pulleys):
Enter Name right_p for Pulley3
Browse and select right_pulley marker of part right_blade_shaft in the field Center Location.
Enter 180 in the field Pulley pitch diameter
Step 3 -3:
Tab 3:
Pulley3 Name : right_p
Center Location : right_pulley
Pulley Width : 30
Pulley pitch diameter : 180
Click on Next button to move on to Step 4 of 11. a b c

11. Step 4. Specifying Materials:
Creating pulley:
Step 4 of 11 (Material-Pulleys):
Keep default Material Type for Pulley1, Pulley2 and Pulley3
Step 4:
Define Mass By: Geometry and Material Type
Material Type: .material.steel
Click on Next button to move on to Step 5 of 11. a b

12. Step 5. Pulley Connections:
Creating pulley:
Step 5 of 11 (Connection-Pulleys):
Click on Pulley1 tab to define connection for pulley1 name motor_p
Select Fixed as a Type to fix pulley to shaft motor_shaft
Select Existing for Body to enter existing part name to which pulley will be connected using selected Type as joint.
Right click -> Body -> Guesses -> and select part name motor_shaft (or Browse for existing part)
Step 5:
Tab Pulley1:
Type: Fixed
Body: Existing -> motor_shaft
Click on Tab Pulley2 to define connection for Pulley2 name left_p a e b d c

13. Step 5. Pulley Connections:
Creating pulley:
Step 5 of 11 (Connection-Pulleys):
Select Fixed as a Type to fix pulley to shaft left_blade_shaft
Select Existing for Body to enter existing part name to which pulley will be connected using selected Type as joint.
Right click -> Body -> Guesses -> and select part name left_blade_shaft
Step 5:
Tab Pulley3:
Type: Fixed
Body: Existing -> left_blade_shaft
Click on Tab Pulley3 to define connection for Pulley3 name right_p d a c b

14. Step 5. Pulley Connections:
Creating pulley:
Step 5 of 11 (Connection-Pulleys):
Select Fixed as a Type to fix pulley to shaft right_blade_shaft
Select Existing for Body to enter existing part name to which pulley will be connected using selected Type as joint.
Right click -> Body -> Guesses -> and select part name right_blade_shaft
Step 5:
Tab Pulley3:
Type: Fixed
Body: Existing -> right_blade_shaft
Click on Next button to move on to Step 6 of 11. a c b d

15. Step 6. Pulley Outputs: a c b d Creating pulley:
Step 6 of 11 (Output-Pulleys):
Click on tab Pulley1 to select required output for post-processing using Adams/PostProcessor
Keep default selection for Angular Displacement, Angular Velocity, Angular Acceleration and Joint Force.
Click on tab Pulley2 and Pulley3 and keep default selection of Angular Displacement, Angular Velocity, Angular Acceleration and Joint Force
Click on Next button to move on to Step 7 of 11. a c b d

16. Step 7. Pulley Completion:
Creating pulley:
Step 7 of 11 (Completion-Pulleys):
This concludes the pulley specification.
Click on Next button to move on to Step 8 of 11 to define tensioning devices. a b

17. Step 8. Tensioner Pulleys:
Creating pulley:
Step 8 of 11 (Geometry-Tensioners):
Enter 2 in the field Number of Tensioner with Deviation Pulley and hit Enter to define first as a tensioner with deviation pulley and second as only deviation pulley with no tensioner.
Click on Tab 1, and select Rotational as a Type.
Enter ten1 in the field Tensioner1 Name.
Browse for tensioner_pulley maker on the part tensioner_shaft
Select Global Z as Axis of Rotation
Enter 160 in Length, 30 in Width and 20 in Depth field
Enter 340 degrees into Installation angle field
Enter ten1_dev1 in the field Deviation Pulley1 Name
Enter 70 in Pulley radius and 30 in Pulley width
Click on Tab 2 to enter specification of Deviation Pulley 2. a i b c d e f g h i j

18. Step 8. Tensioner Pulleys:
Creating pulley:
Step 8 of 11 (Geometry-Tensioners):
Select Fixed as a Type.
Enter dev2 in the field Deviation Pulley2 Name.
Browse for idler_pulley maker on the part idler_shaft
Select Global Z as Axis of Rotation
Enter 75 in Pulley radius and 30 in Pulley width
Click on Next button to move on to Step 9 of 11 to define material properties for tensioning devices. a b c d e f

19. Step 9. Tensioner Properties:
Creating pulley:
Step 9 of 11 (Material-Tensioners):
Click on Tab 1 to material properties for Deviation pulley and Tensioner.
Deviation Pulley: Keep default setting for Define Mass By and Material Type Define Mass by : Geometry and Materail Type Material Type : .materials.steel
Tensioner: Keep default setting for Define Mass By and Material Type Define Mass by : Geometry and Materail Type Material Type : .materials.steel
Click on Tab 2 to select material properties for Deviation Pulley2. a d b c

20. Step 9. Tensioner Properties:
Creating pulley:
Step 9 of 11 (Material-Tensioners):
Deviation Pulley: Keep default setting for Define Mass By and Material Type Define Mass by : Geometry and Materail Type Material Type : .materials.steel
Click on Next button to move on to Step 10 of 11 to define connection for tensioning devices. a b

21. Step 10. Tensioner Connections:
Creating pulley:
Step 10 of 11 (Connection-Tensioners):
Click on Tab 1 to define connection for tensioner.
Select Existing for Body
Right Click -> Body -> Guesses -> select tensioner_shaft
Enter 100 in stiffness, 1 in damping and 100 in preload.
Click on Next button to move on to Step 11 of 11 to complete pulley and tensioner devices specifications. a b c d e

22. Step 11. Tensioner Completion
Creating pulley:
Step 11 of 11 (Completion):
This concludes the pulley set specification.
Click on Finish button to create the pulley set as specified. a b

23. Step 11. Tensioner Completion
Notice that three pulleys, tensioner along with deviation pulley of tensioner and idler pulley has been created. a

24. Step 12. Create Belt: To create the belt component:
From the Machinery tab select the Create Belt icon.
Specify the name of the existing pulleyset to be used.
Select Next to advance to the next (Method) tab.
On the Method tab specify ‘2D Links’ for the belt type.
Advance to the Geometry tab.

25. Step 13. Belt Geometry:
The geometry specifications for the belt are as follows:
Specify a Global Z axis of rotation.
Make segment length 20 mm.
Specify the other geometry properties as shown.
Select the Contact Settings button and use the settings shown on the following page.

26. Step 14. Belt Contact Settings:
In the Contact Settings screen use the values shown here:
Specify the properties as shown.
Select OK to return to the wizard tab.

27. Step 15. Belt Mass: Advance to the Mass tab and:
Specify the properties as shown.
Select Next to advance to the Wrapping Order tab.

28. Step 16. Belt Wrapping Order:
Read the Notes below and then use the following for the belt wrapping order:
.lawn_mower.beltsys_1.pulleyset_1.pulleyset_1_motor_pulley
.lawn_mower.beltsys_1.pulleyset_1.pulleyset_1dev_tensioner1_dev1
.lawn_mower.beltsys_1.pulleyset_1.pulleyset_1_right_pulley
.lawn_mower.beltsys_1.pulleyset_1.pulleyset_1_left_pulley
.lawn_mower.beltsys_1.pulleyset_1.pulleyset_1dev_dev2
Important Notes on Belt Wrapping:
Belts must be wrapped in a clockwise fashion with respect to the belt axis of rotation.
Right-click and ‘pick’ functionality does not currently work for pulleys – you must use the ‘Guesses’ and ‘Browse’ functionality.
Note that pulley names are shown in the modeling window to help when using the ‘Guesses’ functionality.

29. Step 17. Belt Outputs: Advance to the Output Request tab and:
Select both the Span Request and Segment Request checkboxes.
Select an arbitrary belt part for both the belt span and segment outputs.
Select Next to move on.

30. Step 17. Belt Completion:
The system with a properly wrapped belt should look like the following:

31. Step 18. Simulation Setup:
Ensure that appropriate settings are used for Adams/Solver while handling belt (many parts) simulations. Do the following:
Open the Solver Dynamics settings via the menu picks:
Settings  Solver  Dynamics
For Dynamics use these parameters:
Integrator = HHT
ERROR = 1e-5
In this dialog box change the Category to be Executable and make the changes:
Choice = C++
Verify First = No
Thread Count = (or as appropriate for your machine. Use 2X the number of CPUs as a rule of thumb)
The changes above instruct the Solver to use the HHT integrator which is best for belt/chain models. Using multiple threads typically results in wall-time simulation speed increases.

32. Step 19. Simulate & Animate:
To simulate and animate:
Ensure that there is a MOTION on the motor shaft joint, JOINT_6. The MOTION should be of type Velocity and use the following function expression to gradually spin the motor shaft input up:
-1 * step5(time, 0, 0, 1, 180d)
Run a dynamic simulation for 5 seconds, 500 output steps.
Animate the results and watch the tensioner pulley and the belt in the first second or two of simulation. The tensioner should have some initial transient behavior as the system starts up. The transient behavior should settle out after about 4 seconds of simulation time.

33. Step 20. Investigate System:
Create further animations and plots to illustrate things such as:
How does the belt tension (found in the belt segment REQUEST) vary over time?
Does slippage occur in the belt tensioner? (View the angular velocity of the tensioner deviation pulley through time).
Right-click on the belt system and modify the tensioner parameters named pulleyset_1ten_tensioner1. Try changing the tensioner stiffness and/or preload and re-running the simulation to see the effect on the system dynamics.

34. Review: Workshop Questions
1. When specifying a belt wrapping order, what orientation must be used?
___________________________________________________
Pulleys can be connected to the model using three different specifications; list them:
Which integrator is suggested for belt/chain systems (systems with many inter-connected parts that move only slightly with respect to one another)?

35. Answers:
When wrapping the belt the pulleys must be specified in a clockwise sequence with respect to the pulley axis of rotation.
Pulleys can be attached to the model using rotational joints, fixed joints or bushings (compliant).
The HHT integrator is generally best for belt/chain-type systems. Run your simulation with the default ERROR control (1e-5) for HHT and then re-run with tighter ERROR control to see if results change. If results change with tighter ERROR then run a solution convergence study on the ERROR parameter to identify a proper setting.