Model the robot arm motion using articulation

Practice defining articulation in a robot arm model. You will define the robot joints and articulation to model the robot arm motion.

Download and extract the part files.

Open the model Simulation file

Open the Simulation file and reset the dialog box settings.

  1. Choose File→Open and open robot_arm\Robot_assembly_assyfem1_sim1.sim.
  2. Choose File→Preferences→User Interface and on the Dialog and Precision page, reset the dialog box memory.
  3. Click OK.
    The robot arm is designed to help maintenance crew with repairs and construction. It performs limited tasks, such as holding components in a place. It is designed to move slowly to reduce the risk to the crew, during the testing phase. You will model this robot arm motion using articulation. The robot arm model includes five components: base, shoulder, elbow, extender and gripper. The model is meshed and all the material and properties are defined.

Define shoulder joint

Define a robot shoulder joint, which controls the joint movement during an analysis.

  1. Choose Home tab→Properties group→Modeling Objects .
  2. In the Create group, from the Type list, select Joint.
  3. Click Create.
  4. In the Name box, type Shoulder Joint.
  5. In the Magnitude group, from the Rotation Rate Type list, select Field.
  6. From the Specify Field list, choose Table Constructor .
  7. On the Name page, type Shoulder rotation.
  8. On the Definition page, click Import from Text File .
  9. Click Browse .
  10. Select the sinusoid_arm_1.csv file located in the simulation directory.
  11. Click OK three times.
  12. In the Magnitude group, click Plot(XY) .
  13. Click Create a New Window to Plot .
    Notice that the shoulder starts at a 45° angle and rotates through its physical range over the course of one day.
  14. Close the Graphics Window.
  15. In the Orientation group, from the Specify Vector list, select the -ZC axis .
  16. Click Specify Point.
  17. From the Type list, select Arc/Ellipse/Sphere Center .
  18. In the graphics window, select the displayed polygon edge as the point of rotation.
  19. Click OK.

Define elbow joint

Repeat the same procedure from step 3 through to 14 used to define the shoulder joint, to create the elbow joint.

Use the following settings:
Item Setting
Name Elbow Joint
Table Fields Name Elbow rotation
Import from Text File sinusoid_arm_2.csv
Specify Vector -ZC axis
  1. Click Specify Point, and select the arc center of the polygon edge as shown.
  2. In the Parent Joint group, from the Select Joint list, select Shoulder Joint. The position of the elbow joint is dependent on the rotation of the shoulder joint.
  3. Click OK.
  4. Click Close.

Define the shoulder and elbow articulation

Define the robot shoulder and elbow articulation.

  1. Choose Home tab→Loads and Conditions group→Simulation Object Type list→Solid Motion Effects .
  2. In the Name box, type Shoulder Articulation.
  3. In the Region group, click Select Object .
  4. On the scene toolbar, from the Method list, choose Related Faces.
  5. In the graphics window, select the following 6 polygon faces.
  6. In the Joint Selection group, from the Joint list, select Shoulder Joint.
  7. Click Apply.
  8. Repeat the same procedure from step 2 to 7, to create the elbow articulation with the settings in the following table.
    Item Setting
    Name Elbow Articulation
    Joint Selection Elbow Joint
  9. In the graphics window, select the elbow part, the extender, and the gripper 38 faces.
  10. Click OK.

Define articulation parameters

Define constant time intervals method to compute time steps for the articulation modeling of 1 day period.

  1. In the Simulation Navigator, right-click Solution 1 node, and choose Edit.
  2. In the Transient Setup page, in the Articulation Parameters group, in the Start Time box, type 0 s.
  3. In the End Time box, type 86400 s.
  4. In the Calculation Interval box, type 7200 s.
  5. Click OK.
  6. Choose File tab→Save to save the modification in the simulation file.

Solve the model

  1. Right-click the Solution 1 node and choose Solve.
  2. Click OK.
  3. Wait for the solve to end, before proceeding.
  4. In the Review Results dialog box, click No.
  5. Close the Information window.
  6. In the Analysis Job Monitor dialog box, click Cancel.

View the articulation motion results

  1. In the Simulation Navigator, expand the Solution 1 node and double-click the Results node.
  2. In the Post Processing Navigator, expand the Thermal → Increment 15, 7200s nodes and double-click the Articulation Displacement - Nodal node.

Animate the articulation motion results

  1. Choose Results tab→Animation group→Animate .
  2. From the Animate list, select Iterations.
  3. In the Synchronized frame delay (mS), type 400.
  4. Click Play .
  5. Click Stop .
  6. Click Close.
You have completed this lab.