Note: Objective: Lab Procedure: ME 5286 Robotics Labs Lab 4: Flashlight Assembly Duration: 3 Weeks

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1 ME 5286 Robotics Labs Lab 4: Flashlight Assembly Duration: 3 Weeks Note: Two people must be present in the lab when operating the UR5 robot. Read all warnings and cautions in the manual. Once you are done with all your tasks for the day, 1) Save all your programs to permanent storage (i.e. flash drive or H drive) and 2) Remove all of your programs from the robot controller (tablet) including the script files. Failure to remove your programs from the robot controller will result in a loss of points. There is a TCP offset and mass created by the gripper. Use a gripper offset in the Z-direction of 148.9mm and a mass of 0.9kg. Objective: Use the UR5 robot to assemble a flashlight. Lab Procedure: For this lab you will be programming the robot with your software of choice to assemble a flashlight. The flashlight has undergone subassemblies before assembly with the robot, reducing the assembly to four parts. The four parts that you will be assembling are the head, barrel, tail cap, and battery as shown in Figure 1. Figure 1: Flashlight parts that will be assembled during the lab. 1

2 In order to assemble the flashlight you will need to clamp the head of the flashlight into the pneumatic chuck mounted to the table, which is controlled by digital I/O in the robot controller. A sample script for using the pneumatic chuck is provided in the Appendix and posted to the course website. The layout of the components is shown in Figure 2. The four flashlight components will be placed onto a tray. The drawing file for this tray can be seen in the Appendix. Figure 2: The frame of the robot, {XX RR, YY RR }, relative to the frame of the chuck, {XX CC, YY CC }, and tray, {XX TT, YY TT },. The origin of the tray frame is located in the center of the hole in which the flashlight head is mounted, as outlined in the Appendix. The steps of the assembly should go as follows: 1) Place the head into the chuck. 2) Clamp the chuck using the Digital I/O. 3) Place the barrel onto head. 4) Screw the barrel onto the head until 3 Nm is reached. Use the get_joint_torques() command to do this. Ignore the torque readings from the first few rotations as high forces will occur when you try to insert onto the threads. 5) Insert battery pack into barrel. Make sure you place the battery pack into the flashlight with the correct polarity. 6) Place the tail cap onto the barrel 7) Align and screw the tail cap until a torque of 2 Nm is reached. 8) Unclamp the assembly with the Digital I/0. 9) Remove the assembled flashlight from the chuck and place it in the head location of the flashlight tray. 2

3 Notes: - Verify that all the flashlight components are oriented in the same manner for each test. - Tightening the threads with the robot takes a lot of time. After you have the threading started, you can pause your threading task, manually thread the next few rotations and then resume the robot doing the threading. This will save you considerable time during the robot assembly task development. When you take a video of your assembly or demo your assembly the robot needs to perform the whole assembly without human assistance. - Ignore the torque measurement during the first few thread rotations. The torque will be high during the initial threading but will come down. - Start the assembly at slow speeds. Once you have the flashlight assembly working, then try to assemble the flashlight as quickly as possible. The speed setting that we started out with are: speed_ms = 0.25 [m s^-1], speed_rads = 0.25 [rad s^-1], acc_mss = 0.2 [m s^- 2], blend_radius = [m]. - When you release a part, it may stick to the gripper and become misaligned. Think about gripper release methods which will minimize this issue. - The positions in Table 1 provide you with a starting point for the location of parts. You will need to fine tune these locations in order to assemble the flashlight. - Adding delays into your assembly program can be helpful. - Save multiple versions of your code. If you have parts of the assembly working, save it. Keep track of version numbers of your code. - Slowing down the robot s movements before inserting a part will result in a more accurate assembly and will not trigger the protective stop as easily. - The robot often times tries to rotate past its joint range when using its inverse kinematic solvers. Adding poses defined by joint angles will reduce this issue. Table 1: Fixture locations wrt robot base frame, the Z direction is omitted in this table Fixture/ Component X (mm) Y (mm) (1) Trays (2) Chuck

4 Deliverables: - A single report which addresses the following issues and includes: 1) An abstract, introduction, methods, results, discussion, and conclusion section. 2) Description of the steps and method you used to assemble the flashlight. 3) How would you describe the effectiveness of assembling the flashlight? Is your code good enough for an industrial flashlight assembly? Why or why not? 4) How quickly were you able to assembly the flashlight? Provide the time in seconds that it took for your assembly. 5) Speeding up the assembly without increasing the robot s speed, describe how you would do this. Assume that you are in an industrial setting and have ten thousand dollars left in the budget. 6) Based upon your experience with the UR5 robot, what are other assemblies that you feel confident doing? Provide details on how you would accomplish these other assemblies. 7) What was your desired programming method for all the labs. - A single zip file named [last_name]_[first name]_lab4.zip uploaded to Moodle which contains: 1) A PDF of your report. 2) All robot files (RoboDK, URScript, Universal Robot Projects). 3) A video of your robot assembling the flashlight. The format for the video should be.mp4,.avi, or.m4v. - A hard copy of your report is due at the start of class on April 5 th. - Demos of your assembly will be evaluated by Professor Donath from March Additionally requirements and information about these submissions will be posted at a later point. 4

5 Appendix: Figure 3: Drawing file of the flashlight tray that holds parts for 3 flashlights. The tray coordinate frame is centered where one head piece of the flashlight is located. All units are reported in inches. Figure 4: Drawing file of the chuck assembly. All units are reported in inches. 5

6 Figure 5: Sample script for clamping and unclamping the chuck. 6