Design of a Vibration Absorber and Evaluation Using Teleoperation Before coming to Lab: You will need to design a pendulum type vibration absorber (length and mass) using the following physical constraints The pendulum arm itself is fixed to be a steel threaded rod with a length of 19.00cm and a diameter of 0.8cm The mass (based on your design) can be placed on the rod with a permitted length between 5.00cm and 17.00cm measured from the top of the rod to the center of gravity of the mass You can select any number of masses between and for your design, each having a mass of 46g and thickness of 0.50cm (3/16”) Refer to figure Two nuts are used to affix the masses to the threaded rod The number of masses and the position of them on the pendulum must be emailed to your lab TA by 9am on the day of your lab so that he/she can set up the proper design before your lab session begins Your ability to communicate the design clearly to your TA will factor in your grade for this lab Objectives: To design and validate the performance of a vibration absorber Observe the forced responses and compare the responses with and without the vibration absorber Background: The multi-degree-of-freedom (MDOF) system consists of a system including a two story Fig Shake Table Lab Station building model with a vibration absorber which is driven by an instructional shake table The shake table provides an acceleration input to the structural system An integrated circuit DC accelerometer is placed on the moving surface of the shake table, and another accelerometer is attached to each of the building floors The acceleration of the third degree of freedom, the vibration absorber, is not measured Signals are acquired and transmitted to the client using a PC-based data acquisition system Refer to figure This experiment is to be conducted remotely using an internet tool designed based on Network for Earthquake Engineering Simulation (NEES) cyberinfrastructure technology The student has the ability to use teleoperation to run this experiment remotely using the instructional shake table and to use the webcam to view the experiment in real time A Graphical User Interface (GUI) is used at the client side to select the frequency and amplitude of the input motion to the shake table Data from the three accelerometers (one on the table and the Fig Vibration Absorber other ones on the building floors) are streamed from the server to the client at a remote computer (your computer) using the Ring Buffered Network Bus (RBNB) Data and video are available for viewing and storing at the client side (your computer) through the use of the real-time data viewer (RDV) READING: Review notes and textbook sections on free and forced responses of MDOF systems To perform this experiment, you will need to have an internet connection (not wireless), java 1.6 installed, and use a computer that has Matlab available Note that the computers in the CEC are recommended READ THE INSTRUCTIONS BELOW CAREFULLY BEFORE DOING THIS LAB Procedure: a) Follow the instructions provided in Appendix A of this experiment to open the RDV client from your PC b) Using the video provided in the RDV client, sketch the experimental apparatus, test specimen and location of the sensors Plan on including a clean version of this schematic diagram in your report c) You will be provided with the measured responses of the test structure without the vibration absorber You will need to run the system with your vibration absorber design to validate the ability of your design to reduce the overall vibrations of the primary structural system STRUCTURAL DETAILS FOR THE BUILDING PLACED AT WASHU: The masses of the structure on each floor (including the accelerometer and mounting plates) are 848g for the first floor and 1120g for the second floor The stiffness of each column is 68.5 N/m The stiffness on each floor can be considered as two times the stiffness of each column Sensor readings are given in gravities (1g=9.8 m/sec^2) The saturation level (maximum reading) for the each accelerometer is +/-10g Note that in some cases there may be an offset in the accelerometer that you will need to remove in your data d) Observe and record forced responses: Set the Ground Motion Parameters in the client GUI to a sinusoid input with a frequency equal to that of the first mode of the primary structural system and an amplitude as indicated below: For all those students who run the experiment at Washington University in St Louis (WASHU), the first mode frequency should be considered as 1.12 Hz (Use 1.10 to avoid resolution limitations) and the amplitude of 0.0013m For all those students who run the experiment at University of Connecticut (UCONN), the first mode frequency should be considered as 0.89 Hz and the amplitude of 0.02in e) Run the excitation Observe the responses and EXPORT data for the entire response (To export data refer to Appendix – step to step 12) f) Repeat step (d) at the frequency corresponding to the second mode of the primary structural system and the same amplitude as indicated below: For all those students who run the experiment at Washington University in St Louis (WASHU), the second mode frequency should be considered as 3.12Hz (Use 3.10 to avoid resolution limitations) and the same amplitude of 0.0013m For all those students who run the experiment at University of Connecticut (UCONN), the second mode frequency should be considered as 2.8 Hz and the same amplitude of 0.02in After the lab: Describe qualitatively the response for this type of excitation in your report Note: you should begin each test with the structure at rest therefore you should wait until you stop seeing motion at the camera NOTE: The mode frequency values can be corroborated by solving the “eigenproblem” using the corresponding values for stiffness and masses of the system Disconnect the connection so that the next user will be able to connect Theory: After the lab, using the data provided to you for the responses of the primary structural system without the vibration absorber at the two natural frequencies of the system, and the data that you obtained during the experiment, evaluate your design Comment on the ability of your design to reduce the vibrations of the primary system Report: The lab report has not set format Appendix: Teleoperation of the Shake Table 1.) 2.) 3.) 4.) 5.) 6.) 7.) 8.) 9.) Contact your TA by IM to be sure that the experiment is set up and ready to go Open the Teleoperation Control Panel available at the link: http://mase.wustl.edu/wusceel/UCIST/MASE431/lab5_page.htm Right click on “CLICK HERE TO LAUNCH EXPERIMENT” and choose “save target as” to save on a desired location as “RDV.jnlp” A window containing Figure (shown below) will open, indicating everything is working properly Adjust frequency and amplitude sliders to the desired value (REMEMBER THE VALUES THAT MUST BE USED FOR THE AMPLITUDE AND THE FREQUENCY DEFINED AT STEPS “d” AND “f” UNDER PROCEDURE) Press the “START” button View the experiment as the table starts up If you can not view the video and vibration data simultaneously, try manually change the ‘Time Scale’ from the drop down menu to a larger number The “red data” corresponds to accelerometer placed on the shake table The “blue data” corresponds to the accelerometer placed at the first floor of the building The “green data” corresponds to the accelerometer placed at the second floor of the building To export the data as a file, follow the following path through the menus: File - Export - Export data Channels 10.) A window “Export data to Disk” will appear Choose the desired time and select the desired channels as indicated below: For the WASHU-RDV: Select JUST the boxes with extension “NEES a_tbl(g)/1 (Shake table), “NEES f1(g)/0 (First floor) and “NEES f2(g)/0 (Second Floor) For the UCONN-RDV: Select JUST the boxes with extension “xdda1/0” (First floor), “xdda2/0”(Second floor) and “xddg/0” (Shake table) 11.) Select the location to send the obtained data by using the “Browse” button and click on “Export” 12.) A “data.dat” file will be created by default at the location that you choose containing the data for the experiment You are encouraged to use different names for your “data.dat” file so you not overwrite your old data when new data is exported Ex: “data_1.dat” and “data_2.dat” .“data.dat” file should be opened with a “txt” extension 13.) After a short time the “START” button will be re-enabled automatically and no new data will be collected from the experiment At this time adjust your frequency and amplitude values and hit “START” again to run the next sinusoidal excitation 14.) Repeat from step to step 13 to obtain the data associated to the second mode frequency ( Read step “f” under procedure) NOTE: If any problems occur during the experiment, please contact your TA by IM or phone (314) 935-4436 Class IM: MASE431@hotmail.com Please not exceed your time window so that the next group will have their full time allotment Figure View of the RDV window in operation ... new data is exported Ex: “data_1.dat” and “data_2.dat” .“data.dat” file should be opened with a “txt” extension 13.) After a short time the “START” button will be re-enabled automatically and. .. have an internet connection (not wireless), java 1.6 installed, and use a computer that has Matlab available Note that the computers in the CEC are recommended READ THE INSTRUCTIONS BELOW CAREFULLY... Teleoperation Control Panel available at the link: http://mase.wustl.edu/wusceel/UCIST/MASE431 /lab5 _page.htm Right click on “CLICK HERE TO LAUNCH EXPERIMENT” and choose “save target as” to save