23_WS23_SwitchMechanism.ppt

1、,WORKSHOP 23 SWITCH MECHANISM,Objective Determine the minimum force necessary to toggle the switch mechanism to the forward and rearward directions. Software ADAMS 2011 Files Required Switch_start_new.cmd Located in directory exercise_dir/mod_23_switch_workshop,Problem description The given switch m

2、odel contains parts with shell geometry and mass properties:,The switch model contains construction points for adding the necessary modeling elements to address the problem statement. They are: The switch model is mounted such that the models global negative x-axis defines forward and positive z-axi

3、s defines up .,Suggested Steps Import model and set up modeling environment. Add constraints Verify model and simulate. Change the constraint on the right_contact part. Create a Sphere-to-Plane contact force in front Create a Sphere-to-Plane contact force in rear. Add spring force to right half. Ove

4、rride default spring geometry and verify model. Replace the right_follower to right_contact curve-to-curve constraint with a force and verify the model. Simulate the model. Create sphere and plane in front Create a sphere-to-plane contact force in front. Create another sphere and plane in rear. Crea

5、te another sphere-to-plane contact force in rear. Verify the model and simulate Create a force application on the actuator part and verify the model,Suggested Steps (Cont.) Create a function measure. Create a sensor. Create a script and simulate the model. Refine the right_contact connections. Creat

6、e a point-to-point contact force. Verify the model and simulate. Connect the left follower and the left contact and verify the model. Simulate the model Add friction to the curve-curve contact forces. Verify the model and simulate.,There are five sections in this workshop: Section I: Test the right

7、half with constraints only. Section II: Test the right half with front and rear contacts. Section III: Refine the right half of the mechanism. Section IV: Add the left half. Section V: Refine the switch.,SECTION 1,Test the right half with constraints only You can think of the switch mechanism as con

8、sisting of two halves. In this exercise, first constrain the right half of the mechanism and perform a kinematic simulation to visually verify correct motion. Then, add spring and contact forces to the right half to ensure that the mechanism actually toggles. In the following sections you will add m

9、ore detail to the right half, refine it, introduce the left half, refine the entire model to account for friction, and then finally, perform a system-level simulation. This workshop emphasizes the crawl-walk-run method. In this section, you will crawl.,Step 1. Import Model and Set up Modeling Enviro

10、nment,To import the model: Start Adams/View, and set the directory to exercise_dir/mod_23_switch_workshop. Import the model command file switch_start_new.cmd. This file contains commands to build the model named switch. To set up the modeling environment: set the transparency of the actuator part by

11、 right clicking the actuator, and then select Part: actuatorappearance. Move the transparency slider to 80%,b,a,Step 1. Import File and Set up Modeling Environment (Cont.),Deactivate the left_contact part. Turn off the visibility of the left_contact part. Repeat steps a and b for the left_follower p

12、art. Using Settingsgravity, Set gravity in the global negative-z direction. The model should now look like the one shown below.,a,b,d,e,Step 2. Add Constraints,To add constraints: First, for easy picking of global direction vectors, establish a reference marker with global orientation on the base (g

13、round) part. Setting the color and size of the marker helps in referencing it later. Constrain the actuator to the base at POINT_1 such that the only relative allowable degree of freedom is rotation about g. To make selecting the parts easier, turn off the visiblity of the Shell_base_main_geo. Const

14、rain the right_follower to the actuator at POINT_2 such that the only relative allowable degree of freedom is translation along zg.,b,e,a,d,Constrain the tip of the right_follower to the upper curve on the right_contact part. When creating the curve-to-curve constraint, select the red circle, right_

15、follower.right_follower_circle_geo_2, at the tip of the right_follower part, parallel to the global-xz plane, and then select right_contact_upper_bspline.,Step 2. Add Constraints (Cont.),right_follower part,Step 2. Add Constraints (Cont.),Constrain the right_contact part to the base at POINT_8 such

16、that the only relative allowable degree of freedom is translation along g. This might not seem intuitive, but it ensures that there are no redundant constraints in the model. It is a good modeling practice to remove all redundant constraints in your system prior to performing a simulation. Add displ

17、acement joint motion to the actuator-to-base revolute joint such that the actuator oscillates sinusoidally with an amplitude of 15.1 degrees and one cycle per second.,right_contact part,base part,a,c,Step 3. Verify the Model and Simulate,To verify the model: Use the verify tool. Your system should h

18、ave 0 degrees of freedom and no redundant constraints at this configuration. If it does not, inspect the model to determine the discrepancy. To simulate: Simulate the model kinematically to visually verify correct motion using an end time of 1 second with 100 output steps. Save your work.,SECTION II

19、,Test the right half with front and rear contacts Change the constraints on the right_contact part so that it can rotate and make contact with the right front and rear terminals on the base part (It will rock back and forth like a see-saw). Use the curve-to-curve constraint created earlier. this sec

20、tion you will start to walk.,Step 4. Change the Constraint on the right_contact Part,Change the constraint on the right_contact part so that it can rotate and make contact with the right front and rear terminals on the base part (it will rock back and forth like a see-saw). Remove the translational

21、joint constraining the right_contact to the base at POINT_8. Constrain the right_contact to the base at POINT_13 such that the only allowable degree of freedom is rotation about g.,Create a sphere-to-plane contact force between the front end of the right_contact part and the sphere on the front righ

22、t corner of the base part. Use right_contact.PLANE_128 and base.ELLIPSOID_73 The contact parameters should be: Stiffness: 1e5 (milliNewton/mm) Force exponent: 2.2 Damping: 1e2 (milliNewton-sec/mm) Penetration depth: 1e-3 mm Static friction: off Dynamic friction: off Using the ellipsoid and plane geo

23、metries will improve run time when solving.,Step 5. Create a Sphere-to-Plane Contact force in Front,Create a sphere-to-plane contact force between the rear end of the right_contact part and sphere on the rear right corner of the base part. Use right_contact.PLANE_72 and base.ELLIPSOID The contact pa

24、rameters should be: Stiffness: 1e5 (milliNewton/mm) Force exponent: 2.2 Damping: 1e2 (milliNewton-sec/mm) Penetration depth: 1e-3 mm Static friction: off Dynamic friction: off,Step 6. Create a Sphere-to-Plane Contact Force in the Rear,Step 7. Add Spring force to the right half,To add a spring force

25、to the right half: You need markers to create the spring. First, create markers for each endpoint belonging to the appropriate parts. Create a spring between the right_follower at POINT_2 and actuator at POINT_4 using the following parameters: Stiffness: 600 (milliNewton/mm) Damping: 0.1 (milliNewto

26、n-sec/mm) Free length: 9 mm,Step 8. Override Default Spring Geometry and Verify the Model,To override the default spring geometry: With nothing selected, from the Edit menu, select Modify. Filter on geometry, then double-click SPRING_1, then select spring_graphic (not damper_graphic). Override defau

27、lt spring geometry by using these custom parameters: Coil count: 10 Diameter of spring: 2.5 mm Damper diameter at ij: 0, 0 Tip length at ij: 0, 0 Cup length at ij: 0, 0 To make the spring stand out, change the color to white. To verify the model: verify the model The system should now have one degre

28、e of freedom and one redundant constraint. At this time, does the redundant constraint affect what you are doing?,Created Spring,Step 9. Replace the right_follower to right_contact Curve-to-Curve Constraint with a Force and Verify the Model,To replace the right_follower to right_contact curve-to-cur

29、ve constraint with a force: Remove the curve-to-curve constraint between the tip of the right_follower and the upper curve on the right_contact part. Create a curve-to-curve contact force between the tip of the right_follower and the upper curve on the right_contact part. Use the same curves used in

30、 Step 2 on page WS23-13 and the following parameters: Stiffness: 1e5 (milliNewton/mm) Force exponent: 2.2 Damping: 1e2 (milliNewton-sec/mm) Penetration depth: 1e-3 mm Static friction: off Dynamic friction: off Note: After you fill in the I and J curve text boxes, press Enter in each text box to acti

31、vate the I and J Directions(s) text boxes. To verify the model: Use the verify tool. Your system should have two degrees of freedom and no redundant constraints.,Step 10. Simulate the Model,Before simulating the Model: Set Update Graphics to Never. Turn on Debug/Eprint so you can monitor the Adams/S

32、olver performance. To do this: Click on the Simulation tool At the bottom of the Main Tool box change NoDebug to Eprint using the pull down menu. To simulate the model: Perform a 1-second, 200-step dynamic simulation. The model will not animate, but the command window with the Adams/Solver informati

33、on should appear. Animate the results to visually verify the correct motion.,b,d,Step 11. Create a Sphere and Plane in Front,To create a sphere: create a sphere on the actuator part at POINT_12 with a radius of 0.5 mm. This sphere will be used in the sphere-to-plane contact force. To create a plane:

34、 create a plane on the base part at POINT_10, parallel to global yz plane. This plane will be used in the sphere-to-plane contact force. Note: To create this plane, you will need to relocate and reorient the grid. Reset the location to be POINT_10 with the orientation set to the global yz-plane. You

35、 may also need to decrease the size of the working grid (for example, size = 20 mm). Make sure that the points you snap to when creating the plane are on the working grid and not on the part geometry.,a,b,Step 12. Create a Sphere-to-Plane Contact Force in Front,Create a sphere-to-plane contact force

36、 between the front end of the actuator and the base part. As the actuator rotates, its sphere strikes a surface parallel to the global-yz plane on the base. Use the following parameters: Sphere: sphere on the actuator part at POINT_12 with a radius of 0.5 mm Plane: parallel to global yz-plane at POI

37、NT_10 Contact parameters: Stiffness: 1e5 (milliNewton/mm) Force exponent: 2.2 Damping: 1e2 (milliNewton-sec/mm) Penetration depth: 1e-3 mm Static friction: off Dynamic friction: off After you have created the contact force, make the plane and the ellipsoid transparent.,a,Step 13. Create Another Sphe

38、re and Plane in Rear,To create another sphere on the other side of the actuator: create a sphere on the actuator part at POINT_11 with a radius of 0.5 mm. This sphere will be used in the sphere-to-plane contact force. To create a plane on the other side of the base: Create a plane on the base part a

39、t POINT_9, parallel to global yz plane. This plane will be used in the sphere-to-plane contact force. Note: To create this plane, you will need to relocate and reorient the grid. Reset the location to be POINT_9 with the orientation set to the global yz-plane. You may also need to decrease the size

40、of the working grid (for example, size = 20 mm). Make sure that the points you snap to when creating the plane are on the working grid and not on the part geometry. Note: You will need to rotate the plane 180 such that the z-axis of the geometry anchor points toward the actuator.,a,b,Step 14. Create

41、 a Sphere-to-Plane Contact Force in Rear,Create a sphere-to-plane contact force between the rear end of the actuator and the base part. Use the following parameters: Sphere: sphere on the actuator part at POINT_11 with a radius of 0.5 mm Plane: parallel to global yz-plane at POINT_9 Contact paramete

42、rs: same as in Step 12 on page WS23-27 After you create the contact force, make the plane and the ellipsoid transparent.,a,Step 15. Verify the Model and Simulate,To Verify the model: Use the Verify tool. Your system should have two degrees of freedom and no redundant constraints. To Simulate: Before

43、 Simulating, change the solver setting. Use SettingsSolverDynamics Set the Integrator to GSTIFF. Set the Formulation to SI2 Formulation. Perform a static simulation followed by 1-second, 200-step dynamic simulation.,Step 16. Create a Force Application on the Actuator Part and Verify the Model,To cre

44、ate a force application: Remove the motion applied to the revolute joint constraining the actuator to the base. Apply a force to the actuator part at POINT_15 in the positive XG direction, moving with the body. Use the following function: f(f) = -200*time To verify the model: Use the verify tool. Yo

45、ur system should have three degrees of freedom and no redundant constraints.,b,Point_15,b,Step 17. Create a Function Measure,Create a function measure named contact_force, based on the force magnitude of the right rear contact force between the right_contact part and the base part. Use BuildMeasureF

46、unctionNew. Use Force in Object and select Contact Force. Press the assist button, the inputs are shown below. Note: the name for the contact force between the right rear contact and the base may vary depending on how you named the contact force.,Step 18. Create a Sensor,Create a sensor that trigger

47、s when the force magnitude of the right rear contact force (measured in the above step) is greater than or equal to 1 mN within a tolerance of 1e-3 mN. When sensed, Adams/Solver should terminate the current simulation step and continue the simulation script. For the Expression, use the function you

48、just built, (contact_force). You can use the Function Builder to assist in finding the function you want. First under the heading Getting Object Data select Measures. Then click in the textbox next to the measure field, and select RunTime MeasureBrowse. From the Database Navigator list, select the c

49、ontact_force measure. Click Insert Object Name. The measure name should appear in the Function builder area at the top of the dialog box. Click OK at the bottom of the dialog box, and the name should now appear in the expression text box of the sensor dialog.,c,d,e,g,h,i,Step 19. Create a Script and

50、 Simulate the Model,Remember, the force applied to the switch is a function of time. Before you run the simulation, you do not know how much force needs to be applied to toggle the switch; therefore, you do not know how long to simulate. For that reason, you created the sensor. You will purposely si

51、mulate for a larger amount of time than is needed, letting the sensor stop the simulation when the switch has been toggled. Simulate the model to visually verify correct rearward toggle motion using a simulation script based on the following Adams/Solver commands: INTEGRATOR/SI2,GSTIFF SIMULATE/DYNA

52、MIC, END=10.0, DTOUT=.01 DEACTIVATE/SENSOR, ID=your right rear sensor id # SIMULATE/DYNAMIC, DURATION=0.5, DTOUT=.01 Note: to get the rear sensor id# use the Data Navigator and double click on the sensor. Then, find the id# on the information dialog. By using this simulation script, the model will s

53、imulate until the switch is toggled (assuming it toggles before 10 seconds), at which time the sensor is deactivated and the model simulates an additional 0.5 seconds to review follow-on transient behavior. Save your work.,b,c,SECTION III,Refine the right half of the mechanism Replace the pivoting c

54、onstraint at POINT_3 (the lower_contact to base revolute joint) with a more realistic connection that accounts for dynamic phenomena like sliding and liftoff. Create a point-to-point contact force between the underside on the right_contact part and the mid-contact point.,Step 20. Refine the right_co

55、ntact Connections,To refine the right_contact connections. replace the pivoting constraint at POINT_13 (the lower_contact to base revolute joint) with a more realistic connection that accounts for dynamic phenomena like sliding and liftoff. Remove the revolute joint constraining the right_contact to

56、 the base at POINT_13. Constrain the right_contact to the base at POINT_8 such that the only allowable degrees of freedom are translation along zg and rotation about g. This involves creating two joint primitives (inline and parallel). You must ensure that the J marker of each primitive belongs to t

57、he base part, and not to the right_contact part. This will absolutely affect the simulation. See the instructor if you do not fully understand this concept.,a,b,Step 21. Create a Point-to-Point Contact Force,To create a point-to-point contact force: First, create a marker on the base part at POINT_1

58、3. Using this marker, create a point-to-curve contact force between the underside on the right_contact part (curve right_contact.right_contact_lower _bspline) and the mid-contact point, POINT_13, (created marker) on the base. Use the following parameters: Stiffness: 1e8 (milliNewton/mm) Force Expone

59、nt: 2.2 Damping: 1e2 (milliNewton-sec/mm) Penetration depth: 1e-3 mm Static friction: off Dynamic friction: off,Step 22. Verify the Model and Simulate,To verify the model: Use the Verify tool. Your system should have four degrees of freedom and no redundant constraints. To Simulate the model: Simulate the model to visually verify correct rearward toggle motion using a simulation script based on the following Adams/Solver commands: INTEGRATOR/SI2,GSTIFF SIMULATE/DYNAMIC, END=10.0, DTOUT=.01 DEACTIVATE/SENSOR, ID=your right rear sensor id # SIMULATE/DYNAMIC, DURATION=0.5, DTOUT=.01