DESIGN, ANALYSIS AND MANUFACTURE OF AN ACTIVE CONTROL PANEL WITH VIBRATION SUPPRESSION ON AN AUTONOMOUS INTERPLANETARY ROVER

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1 DESIGN, ANALYSIS AND MANUFACTURE OF AN ACTIVE CONTROL PANEL WITH VIBRATION SUPPRESSION ON AN AUTONOMOUS INTERPLANETARY ROVER Lee Do Department of Mechanical Engineering University of Hawai i at Mānoa Honolulu, HI ABSTRACT Our mission is to accomplish the tasks of determining damping coefficient which would help us construct a new method of suppressing vibration throughout the circuit board of the rover. By doing so, we have to calculate each individual product that we are using to determine whether or not our method would actually be valuable to our autonomous rover. By accomplishing the tasks of this project, we could create a rover that would be capable of exploring extraterrestrial terrains within our solar system. The Gantt Chart explains our goals for the research where we need to obtain and derive a second order differential equation with constant coefficients to determine the dampening needed to reduce vibration shock between the wheels and electronic board. Instead, we have constructed a simple spring and foam deposit layer in between the drive wheels and electronic board to see if this could be the first step to dampening out vibration throughout the board. Our task after creating this suppression mount is to then figure out what the dampening coefficient is. But before we could get to the stage of determining the coefficient, we have to fully construct the interplanetary rover using different equipment that incorporates one another. INTRODUCTION Another key feature of the suspension that has not been emphasized in previous technology and flight applications is the ability to absorb significant driving loads (Harrington, B.) explains in an article found online that an important key feature of a vibration suppression system would be the ability to absorb the driving loads which is our goal for this future of this project. In the first stage of constructing this rover, we purchased a design and manufactured rover chassis as well as a drive train. Since other parts needed to construct the vehicle were already on hand, we worked together to make sure all the purchased necessities will contrast one another. The chassis design was a rectangular shaped simple crossbeam constructed by a light weight c-channel Aluminum metal. Our drive train assembly consists of four tough gearbox transmission kit that are powered by 2.5 inch CIM motor that has 337 Watts at 2655 RPM with stall torques of 2.42 N m. The transmission kit has four Hex output shafts with ½ inch Hex Bore Flanged Shielded ball bearings that supply torque to the Aluminum Mecanum wheels that supplies 45 degree angles covering the outer surfaces of each wheel. What powers the four CIM motors is by a 12 Volt, 17 Amp-hour Lead Acid Battery which gives each wheel its own control system. 10

2 The second stage after completion of the rover is to determine whether or not we could manually run the Cross-Link Robot Control System (CLRCS) software program using the schools network system. By assigning different IP addresses to the system, we have created our own network off of Kapi olani Community College s network to control the Rovers movements. In this case we purchased a Controller Area Network device (2CAN) and a Canipede Robot Control Module to receive communication between the hardware s and software s of this project. In order to get the wheels moving, four Jaguar motors also known as the motor controllers are used to monitor the various voltages in all four wheels that is in connection with the Canipede which is interfaced to the computer. Dual Gyro s and Accelerometer sensor boards are used to determine the position and acceleration of the four individual motors which is used to connect the four wheels to the computer program. Lastly, we provided a Pan and Tilt frame to the front of the rover with an attached webcam so that we could manually see where the rover is on the computer program. All of the controls from the wheels are manually programmed into a controller using the CLRCS. What we have achieved so far in this project encompasses the two projects that finally tie in together. Before my partner Eric Caldwell could start on the math portion of this big project, we need to determine the dampening coefficient of the whole vehicle itself. But as stated earlier, we need to come up with a solution that would help decrease the amount of vibration traveling from the wheels to the circuit board. By using simple spring and foam materials, we layered the springs and foam between the Aluminum Chassis and the circuit board. To determine the spring constant (k), we did a simple spring and weight test configuration to figure out the coefficient in each spring. Since all of the springs have the same geometry and length, we simplified the math by just determining one spring constant (k) and multiplying it by the amount of springs we plan to attach to our circuit board to figure out the total spring constant between the drive motors and the circuit board. At this stage, we are still continuing to work to determine the dampening coefficient of the whole rover itself. My partner Eric Caldwell will later perform a Hardware-in-the-Loop simulation that will determine the solution to achieve Autonomous success. The (HIL) mathematical model of the rover needs to be tested in order to advance into our research. All of the variables of this model have been named and the procedures are given with the help of our mentor Aaron Hanai. The force of each wheel is used as a column of variables in a 3X4 matrix which is matched by the x and y direction as well as the torque supplied on the wheels which is defined as the row of variables. This mathematical matrix model cannot be performed since the rows and columns do not match. The solution for this model could be performed using a Pseudoinverse which Maple is used to program this solution. By performing this technique, we could determine the amount of torque that is created in each wheel which we will then advance our project to redistribute the power and current into other wheels when one is losing traction. Before we could get to the mathematical model of the HIL simulation, we will need to discuss and do more research on determining the dampening coefficient of the whole vehicle with an installed vibration suppression mount. Our plans for determining this coefficient is to use a Vernier Motion Detector (VMD) to determine the amount of frequency that the motors are giving off into the circuit board. 11

3 EXPERIMENTAL METHODS Our goal in this project is to design a rover that could be able to carry great amounts of devices that would be useful to explore the different harsh terrains of different inner interplanetary terrains of our universe. Our goals in this method is to use a Vernier Motion Detector to transform the frequency of waves traveled to the device when in motion would take the information from that to plot a graph in which the Fast Fourier Transformation (FFT) graph is shown in the experiments in the Fall 13 as well as Spring 14. In addition for our renewed project, we have constructed a rover that is capable of exploring extraterrestrial terrain within our solar system. Specifically for this project, we aim to improve our dampening and spring suppression mount below the electronic board that can eventually deduce all shocks and vibrations on the electronic platform. By creating a test subject of a vibration suppression using simple foam deposits and springs, we have created a fundamental layout of how we plan to improve our design to eventually absorb all the vibrations that is generated between the rover chassis and the electronic board. With our other colleague Arvin Niro working on a new wheel suspension called Design and Development of a Suspension System used in Rough-Terrain Vechicle Control for Vibration Suppression in Planetary Exploration, this will improve the overall design and analysis of the vibration suppression in our whole system of the rover. By finding new materials and creating a new design around the first test subject of the vibration suppression, we plan to determine the dampening/spring coefficients of our materials as well as find more data that will help us determine our maximum frequency that is created from the rover running at full speed. By developing the understanding on our desired coefficient, we could construct new methods of how remove all shock in our electronics platform which improves the overall performance of the rover. This will allow competitive opportunities for the commercial community to develop quality products as stated in 1.2 of NASA s strategic Goals for 2011 to 2021 and beyond. According to Strategic Plans 2.3 and 2.4, by creating a rover that is capable of operating in various harsh environments, we could advance our autonomous planetary rover to collect valuable information to help advance and prepare human sustainability beyond Earth. By implementing an active control panel with a linear spring suspension system, we can reduce the amount of vibration between the rover chassis and the electronics board. Finally, the completion of this rover at the Kapi olani Community College STEM center with Dr. Aaron Hanai, will help NASA obtain goal number six. NASA Strategic Goal 6 states Share NASA with the public, educators and students to provide opportunities to participate in our Mission, foster innovation, and contribute to a strong national economy. PROJECT TASK AND DATA COLLECTION FOR FALL 2013 The tasks we had to consider in order for our project to be successful as planned. The following is a timeline of the proposed completion of the Vibration Suppression Suspension utilized by our Rover. Our task in this project is to create a vibration suppression system for our electronics board in order to deduce the amount of frequency traveling into our platform. In the tasks that we have performed, we have completed finding the dampening material for our spring which we aligned in parallel between the chassis and electronic platform. By determining the coefficient of the spring, we haven t completed the task of determining the coefficient for our foam material used. With our Gantt Chart changing as we progress through the semester, we started to create a vibration suppression test subject which we used a simple design constructing 12

4 of springs and foam materials. By performing this prototype of the vibration suppression, we have a solid-based foundation of what needs to be done in order to improve a new design of the vibration suppression mount. By creating a prototype of this mount, we performed simple tests using a Vernier Motion Sensor to construct a graph that will help us determine the amount of frequency traveling throughout our rover. Figure 1 FFT Chart: Shows a test chart of the Rover without the Vibration Suppression Mount By constructing a simple vibration suppression mount using springs and foam material, we have created another test subject after attaching in the simple spring and foam prototype mount. We ran the rover in place with the mount attached and this is the new FFT chart with the suppression mount. Figure 2: Shows a test chart of the rover running with a simple spring and foam dampening prototype With just a simple prototype of a vibration suppression mount included on our rover itself, we could see the significant changes in frequency once the mount was applied to the rover. By creating this solid foundation of what we need to figure out for this project, we could improve our suppression mount possibly creating a 3-D image of a new and improved vibration suppression mount on our rover. With determining this, we could easily relate our goals to NASA s strategic goals. A strategic point is found so that materials as well as possible manufacturing procedures can be judged successfully. This will help to test and find the most 13

5 efficient vibration suppression system possible while keeping the project cost effective. By doing this, we are creating an obtainable goal for manufacturing competition to create the best active composite panel. This competition will subsequently help NASA reach their strategic goal number 1.2, which is to develop products that utilize the best and new technology while allowing for competitive opportunities for commercial companies. The Vibration Suppression Control System is an important part of the longevity and exploration time allowed by the vehicle. The rover should be able to withstand various harsh terrains without the capabilities of repair for lengthy missions. This will help obtain NASA Strategic Goals 2.3 and 2.4 by being able to explore extremely distant planetary terrain. Goals 2.3 and 2.4 are NASA s goals to find and understand the origin and evolution, while searching for potential life elsewhere, within our solar system. Goals 3.1, and 3.2 will be reached by sponsoring early stage innovation, while Goal 3.3, which vows to make technologies more affordable, will also be fulfilled by creating new technologies capable of modeling complex ideas with the usage of mathematics and electrical circuit schematics. The development of this rover will ultimately help NASA reach all of Strategic Plan number six in NASA s Strategic Goals for and beyond. This strategic goal is to Share NASA with the public, educators, and students to provide opportunities to participate in our mission, foster innovation, and contribute to a strong national economy. Strategic Goal 6.1 is set to attract and retain students in STEM disciplines along the full length of the education pipeline. Strategic Goal 6.2 is to build strategic partnerships that promote STEM literacy. Strategic Goal 6.3 will engage the public in NASA s mission by providing new pathways for participation. Finally, Strategic Goal 6.4 is used to inform, engage, and inspire the public by sharing NASA s mission, challenges, and results (NASA Strategic Goals, 2011). PROJECT TASK AND DATA COLLECTION FOR SPRING 2014 Our goal is to use what we found from the prototyped modeled vibration suppression and improve our data and design to improve the quality of the vibration suppression as well as design a mount that will give us better data results. Since we have already figured out the coefficient for the spring using simple physics equations, we can now use higher advanced math equations (i.e. Differential Equations) to determine the dampening coefficient of the foam deposit. Once we determine that result, we will design an actual vibration suppression mount using better quality springs and foam material which we could take data using the same process as before. We will use different materials to design a mount which the data collected on the FFT Chart will determine which material is better to use. We will perform two simple tests with and without the new vibration suppression mount design and work on creating new designs which will work at its best. With Arvin Niro working on the suspension of the system, we can work around his design to construct possibly a spring and rubber material as our dampener. The project process will be the same as last semester but now that we have a foundation of what is needed to improve our design, we will work around that and create a more valuable suppression mount that can withstand different terrain. 14

6 EXPECTED RESULTS When completed, this rover will have the benefits of an Active Control Panel with vibration suppression capabilities. This will allow the rover to research and explore greater distances without repair from vibrations. The finished rover is expected to develop new technology for future exploration missions, while educating students as well as educators of STEM programs and NASA related goals. By collecting more FFT data on the new materials, we could improve our overall rover exploration for the future goals we have on this rover. Including a new suspension design will help decrease vibration as well as increase the performance of the rover overall. What we expect after completion of Spring 2014 project on my portion of a vibration suppression is to complete the design and attachment of a new spring suspension system for the rover which we can finally find new data using the same process of plotting a FFT graph with the suspension and a few newer foam material which would act as the dampener for our rover. This time, we could find new material that would be beneficial to outdoor activity as well as indoor. In addition to our results for Spring 2014, we have just purchased one new material where we did different tests at different power outputs to determine our amplitude versus frequency domain graph. Below are the new FFT graphs with having different power outputs with 1 as its max power output. Figure 3: Shows an FFT Chart testing with 100% Power Output at 1 w/ New Foam Purchased from City Mill (Polyurethane Foam) 15

7 Figure 4: Shows an FFT Chart testing with 90% Power Output at 0.9 w/polyurethane Foam Figure 5: Shows an FFT Chart testing with 80% Power Output at 0.8 w/polyurethane Foam 16

8 Figure 6: Shows an FFT Graph testing at 70% Power Output at 0.7 w/polyurethane Foam CONCLUSION & FUTURE RESEARCH In order to achieve further research on figuring out a way to decrease the highest amplitude in our rover, we need to purchase more equipment in order to determine where in the system of our rover is causing that massive spike in the FFT graph. An adaptive inverse dynamics control was used to suppress the vibration of a simply supported panel with equipment s. The piezoelectric layers as sensors and actuators were attached to the panel (Azadi, M.) explains another useful idea which we could actuators and sensors to determine the vibration in the control panel. What we could do is use accelerometers and gyro s which we would attach them to different parts of our active control panel to determine which part is causing the most spikes in which we could adjust and further advance our equipment to determine the important information needed to decrease the vibration in our active control panel. We could also further use Eric Caldwell s portion of the project as well as Arvin Niro s portion to help tie in all the necessary research needed to advance our rover so it could withstand harsh terrains. ACKNOWLEDGEMENTS I would like to thank Hawai i Space Grant Consortium here at University of Hawai i at Mānoa for giving me this great opportunity to advance my knowledge and experience in research which would help me learn more about the advancements of autonomous rovers used to explore our universe. These skills obtained would be honored and appreciated from the help of my two hard working mentors Dr. Aaron Hanai and Dr. Herve Collin as well as the entire STEM center at Kapi olani Community College for providing me this great opportunity and also my two partners Eric Caldwell and Arvin Niro. 17

9 OTHER USEFUL RELATED REFERENCES: Azadi, M., Azadi, E., and Roopaei, M. (2011). Adaptive Inverse Dynamics Control for Vibration Suppression of Flexible Panel with Piezoelectric Layers. Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, FARS, Iran. e=pdf Harrington, B. D and Voorhees, C. (2003). The Challenges of Designing the Rocker-Bogie Suspension for the Mars Exploration Rover. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA. 18