Olympus Mons i

Astro the Rover

Mars Rover Development and Design

Christopher Nguyen, Lauren DuCharme, Kenneth Greene, Greg Maisch, Jerame Taylor, Maria Gutierrez, Christopher Thompson, Yolanda Mora, Melanie Valenzuela, Matt Wolfenden, Quy Tran, Nathan Johnson, Carissa Pariseau

Collaborators: Jesse Grimes –York ∙ Brett Kennedy Faculty Advisor: Dr. Nina Robson

California State University, Fullerton

College of Engineering and Computer Science EGME 414

December 22, 2014

TABLE OF CONTENTS LIST OF FIGURES ........................................................... 1 LIST OF TABLES ............................................................. 1 ACKNOWLEDGEMENTS ............................................... 1 ABSTRACT ....................................................................... 1 PROJECT BACKGROUND ............................................ 2

INTRODUCTION .......................................................... 2 LITERATURE SURVEY .............................................. 2

PROPOSED CONCEPTUAL DESIGN ......................... 2 CHASSIS ....................................................................... 2 SUSPENSION .............................................................. 3 DIFFERENTIAL GEAR BOX ...................................... 5 WHEELS ........................................................................ 6 TELEMETRY ................................................................. 7 ROBOTICS .................................................................... 8

ROBOTIC ARM ........................................................ 8 END EFFECTORS ................................................. 10 SAMPLE ANALYSIS .............................................. 13

PROJECT MANAGEMENT .......................................... 14 TEAM STRUCTURE .................................................. 14 PROJECT SCHEDULING ......................................... 14 PROJECT DELIVERABLES ..................................... 14

APPENDICES ................................................................... 0 LIST OF FIGURES Figure I JPL Opportunity Rover (image courtesy of NASA) ...................................................................... 2 Figure II JPL Curiosity Rover (image courtesy of NASA) ...................................................................... 2

Figure III Chassis block diagram structure ................ 3 Figure IV Chassis design concept ............................. 3 Figure V Proposed rocker design .............................. 4 Figure VI Proposed bogie design .............................. 4 Figure VII Proposed complete concept ..................... 4 Figure VIII Suspension FEA displacement at 300 𝑙𝑙𝑙1T5 Figure IX Differential gear box .................................. 5 Figure X Differential shaft FEA at 21.4 𝑙𝑙𝑙\𝑖𝑖1T ........... 6 Figure XI Wheel assembly design without rubber tread and foam substrate .......................................... 6 Figure XII Diagram of rover communication .............. 7 Figure XIII Closed electrical bay with cabinet locks and hinges ................................................................ 8 Figure XIV Open electrical bay, batteries, and Arduinos to scale. ..................................................... 8 Figure XVIII Planar workspace of robotic arm ........... 9 Figure XV Robotic arm design without end effector attachment ................................................................ 9 Figure XVI Basic 4 bar linkage design (REF) .......... 10 Figure XVII Right view of arm in stowing configuration ............................................................................... 10 Figure XX Longworth chuck design concept with internal view............................................................ 11 Figure XIX Longworth chuck block diagram ............ 11 Figure XXII Single finger actuation gripper .............. 11 Figure XXI Single finger actuation gripper block diagram .................................................................. 12 Figure XXIV Single scoop bulk sampling tool .......... 12 Figure XXIII Bulk sampling sscoop block diagram... 13

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Figure XXV CPT motion breakdown ....................... 13 Figure XXVI Linear actuator directly mounted to servo ............................................................................... 13 Figure XXVII Fully extended linear actuator ............ 14 Figure XXVIII Sensor housing for data retrieval ...... 14 Figure XXIX Project schedule and GANT chart ........ 6

LIST OF TABLES Table I .................................................................... 14 Table II Team structure by sub-team division ........... 6 Table III Chassis morph chart ................................... 0 Table IV Chassis pugh chart ..................................... 0 Table V Material properties of aluminum and silicon bronze ...................................................................... 1 Table VI Suspension morph chart ............................. 1 Table VII Suspension pugh chart .............................. 1 Table VIII Differential morph chart ............................ 2 Table IX Differential pugh chart ................................ 2 Table X Wheel morph chart ...................................... 3 Table XI Wheel pugh chart ....................................... 3 Table XII Robotic arm morph chart ........................... 4 Table XIII Robotic arm pugh chart ............................ 4 Table XIV End effector morph chart .......................... 5 Table XV End effector pugh chart ............................. 5

ACKNOWLEDGEMENTS The Olympus Mons Rover Team would like to thank

the many individuals and companies that have provided support and sponsorship for the project so far. The team would like to recognize Dr. Nina Robson, the team advisor and professor for EGME 414, for her dedication to the success of future engineers and researchers. In addition, Olympus Mons would like to thank collaborators Jesse Grimes-York and Brett Kennedy of the Jet Propulsion Laboratory for their constant assistance and constructive feedback of designs and potential competition strategies. The CSUF electrical engineering department, and specifically Dr. JiDong Huang and Ye Daniel Lu, have been incredible resources for information regarding design and use of electronic components. The team would also like to extend appreciation to the CSUF Geology Department for its assistance in designing and understanding the requirements of geological surveying and analysis that are required of competition. Lastly, the team would like to acknowledge and thank the many sponsors who have reached out and provided gifts in kind and financial support, such as ServoCity, and Quoc Viet Foods.

ABSTRACT The successful exploration of Mars began in the 1970s

with a probe launched by the Soviets. Since then, NASA has launched several rover missions that have collected valuable data. The current rover mission, Curiosity, has been searching for evidence of past, or possible future, habitability. Due to the more advanced explorations of the planet and its terrain, the capabilities of the rover must evolve.

The proposed research will involve the conceptual design of a robotic vehicle capable of performing tasks for a sample return mission within the parameters and requirements of the University Rover Challenge. Beginning with 2014 rover design, every component and module was evaluated, and solutions for improvement were proposed.

Utilizing Pugh charts, risk analysis, and finite element analysis (FEA), subsystem designs and material options were evaluated and selected. The subsystems evaluated include the chassis, suspension, wheels, robotic arm, end effectors, and telemetry. SolidWorks designs were created, analyzed, surveyed, modified, and optimized. Design considerations included minimizing overall weight, stability, maneuverability, workspace of robotic arm, and control systems.

The chassis design is an octagon shape with an aluminum tubing frame which reduces weight and prevents wheel or suspension interference. The suspension has a rocker bogie design capable of a 90 degree departure and approach. It also utilizes a differential system consisting of a beveled geared shaft with a 1:1 ratio for stability. The wheels have a 10 inch diameter, are light weight, and an elevated gear box. The robotic arm has three degrees of freedom, utilizing a four bar linkage with linear actuator capable of being stowed while traversing terrain. The robotic arm will use custom grippers, Longworth chuck for equipment servicing tasks, single finger gripper for astronaut assistance, and a collection scoop for sample analysis and return. The telemetry system will use two Arduinos for remote control with the combination of a cloverleaf and Air Max Bullet for antennas to facilitate communication and response of rover. A final conceptual model was completed with each element, from design to materials, evaluated and decisions made based on proposed

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improvements that will make this rover more stable, protected, agile, and improve overall functions.

PROJECT BACKGROUND INTRODUCTION

Originally created as an extracurricular activity, the California State University, Fullerton Mars Rover project has grown into a senior design project. The extracurricular activity was designed to start a pathway into robotics. Geared towards competitions, students are challenged by the tasks given by each competition. The University Rover Challenge was the first competition the project was the first competition where a remote controlled vehicle is design

LITERATURE SURVEY

Initial research was conducted by investigating current Mars rovers that are being used for interplanetary research, such as Mars Exploration Rovers Opportunity and Spirit and the Mars Science Laboratory Curiosity Rover. Each of these rovers, designed by Jet Propulsion Laboratory for NASA, were tasked with conducting tasks and investigating the Mars surface, just as required by the University Rover Challenge. Many components of each rover were considered and provided inspiration for the technologies that will be featured on the Olympus Mons Rover.

Figure I JPL Opportunity Rover (image courtesy of NASA)

Upon investigating the Opportunity and Spirit rovers, an initial assessment of its features were made. For example, this rover features a 6 wheel design using a rocker bogie suspension system. Each of the wheels is capable of being independently steered and the suspension system is safely operational at a maximum slope of 30°. The size of the rover was also considered and was found to

be 1.5 𝑚 × 2.3 𝑚 × 1.6 𝑚. In addition, the rover also utilizes a robotic arm containing a 5 degrees of freedom that can be stowed during terrain traversing to prevent wear and damage.

Curiosity was also investigated, as it is the largest and most advanced Mars rover ever created, launched, and successfully landed on another planet. This rover also features a 6 wheel configuration with a rocker bogie suspension. Since this rover was designed to contain a sample analysis laboratory on board, its design was also helpful in determining what kinds of scientific tools should be featured on an exploration robot. Many of the tools used for sample analysis on Curiosity utilize the 5 degree of freedom arm and are housed on the end effector turret that rotates as needed for drill bit and science tool exchange. The robotic arm also features a stowing configuration and is mounted on the front of the chassis.

Figure II JPL Curiosity Rover (image courtesy of NASA)

PROBLEM STATEMENT AND PROJECT OBJECTIVES

The project is designed to help engineering students accomplish necessary learning skills that would prepare them for industry. As a part of this goal, allowing students work in multidisciplinary environment will help broaden their vision of many different aspects of engineering. Specifically this project will help students understand spacecraft design as well as scientific procedures.

PROPOSED CONCEPTUAL DESIGN CHASSIS

The main functions of the chassis are to support the rover’s components, weight distribution, stability, storage, and the ability to minimize forces generated from the

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components and/or terrain. The chassis is composed of an aluminum tubular frame with a bi-level structure. It has a flat aluminum plate welded to the frame for the support of other attachments. The chassis has a single brace attached laterally across the center for the differential and the overall stability of the rover.

Figure III Chassis block diagram structure

The aluminum tubes are one inch (25.4mm) in diameter with an 1

8 𝑖𝑖. (3.18mm) thick wall. The chassis

base is an octagon shape with over-all dimensions of 29 in. (736.6mm) square, angles of 45° from one side to the next, and each side is 12.6 in. (320.04 mm) in length. The second level is 6.2 in. (157.48mm) high from the base. The base has approximately 766.56 𝑖𝑖2 of space for the components to be attached to.

A maximum weight of 110lbs (50kg) for the rover is specified by the competition guidelines. The current weight of the model chassis is 13.05lbs(5.92 𝑘𝑘). The aluminum tubing offers us a light weight yet strong frame with which to work with. The material is easily available and fairly simple to manufacture into specified designs. The team imposed other requirements including that the rover be able to fit thru a standard sized door (usually 30 in. (762 mm)), and that components be easily secured and attached to the chassis.

The chassis was designed starting with last year’s model which was made from wood and metal. It had a very basic box design and was inherently unstable. This year, the chassis is designed using all aluminum which minimizes the weight and increases stability. The initial square shape posed a problem for maneuverability. After some design concepts the wheels should be capable of rising above the base. Cutting the corners and making the

resulting eight sides equal in length moved the wheels and suspension closer in towards the center of the rover, adjusted the center of gravity below the base, and lightened the weight. Several iterations and simple designs were considered.

Figure IV Chassis design concept

The strength of material, component assembly, the weight of the material, and physical design of the material were the major considerations in the early design. The comparisons can be seen in Figure VI in the Appendices.

With the current design, the chassis will be able meet the requirements of the competition and the requirements of the team. The machinability of the aluminum will allow for the easy removal and replacement of components as well as provide the strength and stability for movement of the rover and task conditions of the robotic arm.

SUSPENSION

Both of the supporting components of the suspension, the rocker and the bogie, will be constructed from the aluminum alloy 6065-T6. This alloy is determined to have properties that limit both weight and inhibit corrosion. Having a lower density than that of steel the aluminum weighs approximately 2.5 times less than its steel counterpart. Aluminum is a very desirable metal as it is more malleable and elastic than steel. Steel is a very tough and resilient metal but cannot generally be pushed to the same extreme dimensional limits of deflection as aluminum without cracking or ripping even though the steel will resist more force initially. While malleability is very important for manufacturing, aluminum’s greatest attribute is that it is corrosion resistant without any further treatment it doesn’t rust as its steel counterpart does. As where the loaded friction bearing components are concerned, the pivot points will consist of oil impregnated silicon bronze bushings SAE code 841. Bearings are typical for use in high load applications where the friction

Chassis

Torsional

Shifting While Moving

Suspension and Robotic Arm Movements

Weight Distribution

Cargo

Robotic Arm

Telemetry

Support

All Components

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coefficient must be low. The problem lies in the exceptions of a low pressure atmosphere or fine dirt environments such as the surface of mars. In these situations the typical open bearing has the potential to cease up due to the buildup of debris in the races. Though if a sealed bearing is used the same potential problem may occur. Over time as thermal expansion occurs and due to prolonged use in a corrosive and low pressure environment, all that needs to happen is for the bearing to fail is the glue holding the seal to creep or the rubber to degrade and the bearing will fill with silt inducing a failure. In low pressure environments there is not enough air pressure to resist the back pressure created in semi sealed object. This may cause the seal to fail leading to further damage of components. As such bronze metallic bushings impregnated with 18 % SAE 30 weight oil to smooth the rotation of the shaft. Due to the tight tolerances there is not a gap large enough for material to contaminate the rotation surface. But if a contaminant were to enter the surface there are no moving components to induce a problem, the dirt would simply work its way out the other side of the bushing. Air pressure has no effect as there are no seals just a machined surface. Also brass does not rust thus in a corrosive environment the system will not degrade integrity. Table VII of the Appendices shows the material properties of the alloys that have been chosen.

Due to the length requirement for the competition that the rover be less than or equal to 1 meter the suspensions workspace is limited to 28 inches square. This limit was imposed to allow for the adaptation of a 10 inch wheel. The suspension mounts to each wheel assembly along the centerline of the wheel. With a 10 inch wheel that means for an additional 5 inches on both the front and back of the 28 inch limit. This will put the overall resting length at 38 inches, 1.4 inches under the 1 meter length requirement. Below are the proposed designs in Figure V-VII.

Figure V Proposed rocker design

Figure VI Proposed bogie design

Figure VII Proposed complete concept

At a total of 1.28 lbs. the system has been lightened through the use of low density metals and the removal of unnecessary material along the length of the components to represent a lightweight solution to the design request. Numerous force calculations were used to create a stable system. Through basic finite element analysis and hand calculations the center of mass was able to be located at X = 0.30 inches, Y = -4.02 inches, and Z=0 inches from the center of the main mounting hole. This states the center of mass is 0.3 inches forward and set low at 2.48 inches above the base plate mount of the wheel assemblies. This low weight and mass center will aid the other components in creating a stable platform as the chassis bottom is at approximately this mass height.

Through several designs as seen in Table IX, one of which was an eight wheeled configuration that could not work due to the maximum length requirement. This was due to many factors including length, cost, and programmability, the 6 wheeled system above is chosen. Another important factor that was considered was how to adapt to the wheel assembly. Single post fixed or free, or a bolt pattern. By determining the types of servos that are to be used for wheel rotation it was decided that a 4 bolt pattern with a radius of 0.35 in and clearance for #6 machine screws would be sufficient to attach the assemblies.

The system is supported on a single pivot on each side of the chassis allowing freedom of movement in the suspension. Since the systems center of mass is fixed, unlike traditional spring damper systems, the wheels are

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capable of traveling 1.3 times the wheel diameter vertically while maintaining latitudinal and longitudinal stability. This result was measured at full drop of the rocker arm while the bogie is set to an elevated level position. This is done in an attempt to simulate the case of the rover climbing down sheer ledge as is one of the competitions tasks.

To be able to support rover in its entirety the suspension was tested using FEA to determine the load it is capable of handling. At a center load of 300lbf the arms are capable of supporting this load with a maximum deflection of 0.033 inches on the lower beam, as can be seen in Figure 4. Still with double the load on the rover suspension the system still has a minimum factor of safety of 2.1. Furthermore at a maximum VonMises stress of 18,600 psi at this test load. The components are far under the yield strength of 40,000 psi thus eliminating the possibility of failure due to loading. At maximum load the rocker arm will be under 55 𝑙𝑙𝑓. The competition has a requirement that the entire rover be under a mass of 110 𝑙𝑙𝑓. With one rocker bogie assembly per side, this weight is divided in half. The reason to have this large factor of safety is to resist the moment of inertia created by the height of the wheel assembly when the Rover is at a 45 degree side angle. At this point there is a moment of 137.5 𝑙𝑓 − 𝑙𝑙𝑓 to resist. The arms are capable of resisting this force with a VonMises stress of 2.9𝑥104 Psi and a maximum deflection of 0.04 inches.

Figure VIII Suspension FEA displacement at 300 𝑙𝑙𝑓

DIFFERENTIAL GEAR BOX The differential gear box utilizes the weight of the

system to stabilize the body as the rover traverse through uneven terrain. The gear box contains four bevel gears that are connected to aluminum shafts where two shafts will link across the chassis to the rocker arms. In addition, the use of six pillow blocks with bearing inserts will be mounted to the chassis which is where the aluminum shafts will be mounted through. Figure IX illustrates the system of the differential gear box.

Figure IX Differential gear box

The method to assemble each component varies depending on the simplicity of the design. To mount the bevel gears onto the aluminum shaft, set screws will be used to fix the two parts together. The aluminum shafts will also be mounted to the bearing inserts with set screws so the shaft does not slide out of the inserts. The connections to the rocker arms and shaft will be mounted using keyways and bolts to lock the rotation of the system.

Figure IX shows that the rover will have only one pivot point where the weight of the system will be held. Without the bevel gears, the chassis will rock from front to rear as it traverses on an uneven terrain. By adding a differential gear box to the system, the chassis will stabilize because if the counter rotating affects that the system makes. Since the two shafts connected to the rocker arms are rotating the same direction, the forces applied to the two center gears will be equal from both shafts. The forces from rocker arm shaft are acting on the two center bevel gears in opposite directions which will create a level chassis. The force being applied to the differential gear box will be determined by the weight of the chassis and components on the chassis.

Initially, the preliminary design was to utilize a differential link/restraint. A differential link was designed to prevent the rotation of the chassis at the pivot point where the rocker arms are connected to the chassis. The differential link creates a crossbar link from one end of the main differential pivot to the other pivot. In addition, it adds a center differential pivot at the center of the crosslink bar that is attached to the chassis of the system. The problem with the differential link is that the heim joints had too much play which caused vibration. There were difficulties with the alignment and concentricity of the joints on the rotational pivot of the differential.

The second design concept was using a differential gear box to stabilize the rover. This created a much simpler design since it does not use a crosslink bar. The first iteration using a gear box system was with three bevel

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gears, carbon fiber tubing, and aluminum ends. The idea of using carbon fiber was to reduce the weight of the system while keeping the rigidity of the shaft. The method required carbon tubing to be epoxy aluminum ends. This idea was not used since the system was complex to manufacture. In addition, the worth of using carbon fiber on the system could not be compared to using full aluminum. After some risk assessment, using carbon fiber will increase cost and time which is not worth creating to reduce the overall weight by a couple of pounds.

The final design utilizes four bevel gears with a one to one ratio and a full aluminum shafts connecting the bevel gears and the rocker arms. This design created a much simpler look and provides more room for other components on the rover. The diameter of the shaft between the two pillow blocks is one inch to withstand the load of the chassis. The ends of the shaft have a half inch diameter to fit through the bore of the bearing inserts, bevel gears and rocker arms. Table X shows a morph chart of the down selection of the final design concept.

Through FEA analysis, the aluminum shaft was simulated for stress, strain and deformation. Figure X shows the stress that the shaft encounters at the keyways.

Figure X Differential shaft FEA at 21.4 𝑙𝑙𝑓\𝑖𝑖

The yield strength of this material is greater than the maximum stress that the shaft encounters at a torque of 21.4 𝑙𝑓/in. The maximum displacement that occurs in the shaft is 0.05774 mm. Through this analysis, the design of the shaft can hold the weight of the rover.

WHEELS

The 2015 Ion Rover wheel assembly features a 9-inch diameter aluminum machined wheel. A single SPG7950A-CM Channel Mount Servo is secured at the top of the assembly, allowing full rotation of each of the six wheels

in any direction. Two machined brackets anchor this servo to a 1:256 gear ratio gearbox and brushless electric motor. These three elements reside above the wheel itself, the motor and gearbox driving a sprocket and belt, which in turn drives another sprocket attached to the hub of the wheel’s shaft. This distance is supported by two struts, one on either side of the wheel, which are connected to the lower shaft by bearings. A length of mountain bike tire is wrapped around the wheel to provide traction, with closed-cell foam substrate in order to provide adequate deformation of the tire.

Figure XI Wheel assembly design without rubber tread and foam

substrate

One of the major factors taken into consideration throughout the design process was the need to increase the diameter of the wheel itself. The previous design included an 8-inch pneumatic wheel and tire, but had difficulty climbing certain obstacles. This new design will allow each wheel a more ideal angle at which to traverse the terrain. The initial design included finding a pneumatic wheel and tire that would include these dimensions. However, pneumatic wheels with a diameter larger of 8 inches are typically designed for use with heavy load-bearing needs, such as wheelbarrows. These wheels were far too heavy for their intended operation, each individual wheel weighing in excess of 5 pounds. At 30 pounds total for the wheels alone, this would put far too much strain on the weight requirement for the team as a whole. The next consideration was whether or not the wheel would be pneumatic. Upon further research, the process to design and manufacture a custom designed pneumatic wheel would be far too time-intensive and difficult to design for the role it needs to fill. In order to simulate the benefits of a pneumatic tire, a mountain bike tire will be used in conjunction with a closed-cell foam substrate. The foam itself can be found at various densities in order to simulate

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the ideal pressure of a pneumatic tire, allowing for adequate deformation when traversing difficult obstacles.

Another consideration for the design of the wheel was cost and manufacturability. Initially, the wheel was to be machined out of a single puck of aluminum. However, due to the amount of material that would be cut away during this process, it was deemed to be less than ideal. Instead, an aluminum pipe with a 9-inch outer diameter and 8-inch inner diameter will be used, cut, faced, and turned such that the wheel itself will have a thickness of ¼ inch. A ¼ inch thick wall offset will be left along the inside of the wheel, allowing for a machined rim to be bolted to it. This process will allow for less material to be cut away, saving on both cost and time while still maintaining adequate structural integrity of the wheel.

Because of the structure of the gearbox, it serves as a major structural component of the wheel assembly. It is the heaviest of all the parts, and its position above the wheel minimizes the rotational inertia and the necessary torque to activate the servo and turn the wheel.

TELEMETRY

Figure XII Diagram of rover communication

This rover is going to be using 3 Arduinos. One Arduino Uno, will be used to gather information from 4 different sensors, pH, moisture, UV, and ultrasonic sensors. Given that one of the tasks in this year’s competition is to test soil samples, the pH, moisture, and UV sensors will be used on the CPT, known as the cone penetration tester, for these samples and will be tested remotely. The ultrasonic sensors the rover will have are going to be used when controlling the rover to make sure it does not collide with any unwanted entities.

The other Arduinos that are going to be used are two Arduino Megas. The difference between the Uno and the Mega, is that Uno has less I/O pins located on its board

meaning it can control less and has a smaller memory storage system. One of these will be used for the overall dynamic control of the rover. The last mega will be used as central control and will monitor and collect data gathered by the multiple servos and other Arduinos. A GUI system will also be created to show the data the Arduinos receive and output for further analysis in the command station since one of the requirements is to view the information and control one’s rover from afar.

Since the rover will be operating from a remote location, it will not have a constant direct power source. Therefore, lithium polymer batteries are going to be used to provide power to all electrical components in the system. These components are going to be kept in an electrical bay that will be mounted on top the chassis. This electrical bay will provide both storage and protection from the surrounding environment such as sunlight and dirt particles. This bay will also allow for wires to be organized and placed where they will not be a disturbance to any other component on or around the rover.

The rover will be operating in Mars like conditions, in other words, it will be operated from a remote command station. Since the rover will not be seen from this command station due to distance, Lorex security camera system will be used as the eyes for the rover. These “eyes” provide the ability to visually see using different cameras simultaneously instead of requiring the use of video switching to monitor each camera.

Three different cameras will be used for the entire visual system. One of the cameras will be mounted underneath the chassis to monitor the wheels so that, in the event of any disturbance or problem with the wheels or around the body of the rover, it can be assessed from the command station. Another camera will be mounted above the chassis, on a pole, essentially made from a PVC pipe, so that the command station can get a good idea of the rover’s surroundings during testing. The last camera that is going to be used is going to be mounted on the robotic arm so that the samples collected can be analyzed and assessed visually.

Since the rover is required to be controlled remotely, it will utilize radio frequencies to communicate with the command station. Two different types of frequencies will be used, one for controlling the visuals and one for the overall general control, to avoid interference. By reducing the amount of interference, the rover’s communication and visuals will have much better____. The frequency ranges that are going to be used are 2.4 GHz and 5.8 GHz frequencies.

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The rover will be controlled on a 2.4 GHz frequency range with the use of an Airmax bullet antenna, and the visual systems will communicate over the 5.8 GHz radio frequency with a cloverleaf antenna. The 5.8 GHz frequency is going to be used for the visual feed because its tags can easily read at higher speeds without mistakes and large amounts of data can be transmitted at this band. Visual feed is something that cannot lag or have interference during testing, and since the 5.8 GHz band offers the most accuracy and consistency, it is ideal to operate the visual feed on this band.

Two Arduino Megas, instead of three, are to be used for the system because a third Mega is not required. Arduino Uno’s are mainly used for smaller projects, since they contain only 32KB of memory as oppose to 128KB of memory of the Mega. Since the Uno could only contain about 1000 lines of code, this microcontroller fit perfectly to collect data gathered from the sensors. Arduino Megas were used for the higher end tasks such as controlling the entire rover and collecting the information from every other component because memory storage is greater and has 8KB of SRAM, which is a type of memory chip that is faster.

There were different cameras for this project that were looked into. Go Pros were the best option for the design a couple weeks ago, until the dilemma of viewing all 3 cameras at the same time had occurred. Camera switches were the best option, but some switches only worked with certain frequencies, to save the hassle and avoid any risks, Lorex camera systems for homes were the next best option. These cameras are all linked together, meaning the team holds the ability to view all three camera feeds at the same time from the command station. These cameras were not only better for the system, but they were cost effective. One Go Pro would have cost nearly two hundred dollars, while the Lorex system with three cameras would cost roughly the same price.

The competition regulations for Telemetry are as follows:

The team has the option to choose frequencies of 900MHz or 2.4GHz, any other frequencies being used are prohibited unless the team sends a notification. Both omnidirectional and directional antennas could be used for the system, and must not exceed a height of 3m. Teams must bring at least 20m of antenna cables to deal with any scenario they may face. Students must have the ability to view the rover from the command station and require the team to not make any contact with the rover while in competition. (REF)

Figure XIII Closed electrical bay with cabinet locks and hinges

Figure XIV Open electrical bay, batteries, and Arduinos to scale.

ROBOTICS

ROBOTIC ARM The 2015 robotic arm features 3 DOF with an

additional roll located at the interface between the robotic arm and end effectors. In combination with the end effectors, the robotic arm is designed to accomplish the various competition tasks featured in the 2015 University Rover Challenge. The complete assembly for the robotic arm consists of a base plate, a 4 bar linkage sub assembly, 3 arm links, 3 servo mounts, 2 secondary servo mounts, 1 linear actuator, and 3 servo motors. Standard black-oxide screws and binding posts are used to secure the system while still allowing mobility between links.

When designing the 2015 robotic arm, both successful and failed design concepts associated with the previous model were taken into consideration. One major design flaw with the previous model was its inability to stow away when not in use. As the rover would traverse over rocky terrain the extended robotic arm would bounce and rock resulting in excess stress on the arm. Furthermore, an extended arm displaces the center of gravity of the rover thus compromising the stability of the entire system.

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Therefore, the 2015 robotic arm is designed to be able to retract and fold on top of itself when not in use. This additional design feature significantly reduces the risk of components being damaged during competition.

Early development of the kinematics for the robotic arm was a crucial part of design. The robotic arm needed to be capable of completing complex tasks without overcomplicating the overall design of the arm. A higher DOF would exponentially increase the complexity for motion planning and control. However, the arm needed to be a multi degree of freedom system in order to accomplish competition tasks. To help resolve this issue, the rover itself will be used to provide the yaw motion for the robotic arm. By utilizing the rotational motion of the rover, the arm is able to encompass a substantially larger workspace while still remaining a 3 DOF planar arm.

Figure XV Planar workspace of robotic arm

With the exception of the fasteners and motors, all the components for the robotic arm will be machined in shop on the CNC machines. Because of this, designs were intentionally kept simple and repetitive to streamline production. 6061 aluminum alloy will be used for all manufactured components due to its light weight, durability, and accessibility. SolidWorks CAM software will be used to create codes when manufacturing parts. FEA will be done on each part to ensure the arm doesn’t experience any form of deflection or sagging. A code on MATLAB is currently being developed to analyze the various torques experienced during movement.

Figure XVI Robotic arm design without end effector attachment

1) Base: The base, which mounts to the chassis, provides a stable, stationary platform for the robotic arm. The base features 4 mounting points for the 4 bar linkage and is designed to mount from the base center to the chassis. The decision to center mount the base keeps the option for redesign open without having to change mounting spots on the chassis.

2) 4 Bar Linkage sub assembly: A 4 bar linkage design is featured for the base link, or shoulder, of the robotic arm. With the use of a 4 bar linkage, the translation motion produced from the attached linear actuator is converted to a pitch motion for the second link. More importantly, the 4 bar linkage allows for the first link to dip below the chassis. This added vertical drop provided by the first link allows for shorter, and consequently lighter preceding links.

In order to analyze and ultimately optimize the system a series of general equation must be derived beginning with the constraint equation. To better explain the following process, a general model is used as represented in figure X. The constraint equation for a 4 bar linkage is derived using the existing parameters. A general form of the equation is represented as:

𝜓 = 𝛿 ± acos

⎝

⎛ −𝐶𝑐𝑐𝑐𝑓𝑓

�𝐴𝑐𝑐𝑐𝑓𝑓2 + 𝐵𝑐𝑐𝑐𝑓𝑓2⎠

⎞

The above equation determines the follower angle 𝜓, for each value of the input crank 𝜃. Next, the position loop equation can be derived. The position loop equation determines the coupler angle 𝜙. The general equation for position loop is represented as:

𝜙 = 𝑎𝑎𝑎𝑓𝑎𝑖 �𝑙𝑏𝑖𝑖𝜓 − 𝑎𝑏𝑖𝑖𝜃

𝑘 + 𝑙𝑎𝑏𝑏𝜓 − 𝑎𝑎𝑏𝑏𝜃�

-20 -15 -10 -5 0 5 10 15 20 25

-15

-10

-5

0

5

10

15

Horizontal Workspace [in]

Ver

tical

Wor

kspa

ce [i

n]

Workspace of Robotic Arm Iteration

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Figure XVII Basic 4 bar linkage design (REF)

With these two equations, the optimal lengths of links and placement of linear actuator can be calculated to produce a desirable second link pitch angle.

3) Links: All three arm links share the same general design. Beginning with the link closest to the base, the edge farthest from the chassis is designed to support the servo mounts and servos. Beginning at the base and moving down the arm, each preceding link is intentionally shorter and lighter to reduce the amount of torque needed at each joint to move the preceding links and end effector. The total reach of the robotic arm is approximately 25” including end effector. Each link is designed with a cut out to allow for the arm to fold on itself when stowing. One on end of each link, a 1/8” thick piece of metal protrudes out and connects to the various servo motors. The end of the extended piece is designed to mirror the shape and 4 bolt pattern of the hub located on the servo.

Figure XVIII Right view of arm in stowing configuration

4) Servo Mount: The robotic arm features 3 servo mounts located at the end of each link. The servo mounts clamp down to both the top and bottom of the link to support the vertical loads experienced at each joint.

5) Secondary Servo Mount: The secondary servo mounts can be found connecting link 1 to 2 and 2 to 3. The secondary servo mount functions to help support the weight of the preceding link by attaching it to the prior link’s servo mount. The design and mounting location is set concentric to axis of rotation of the servo as to no impede rotation.

6) Servo Motor: The arm features 3 SPG7950A-CM Channel Mount Servos at the joints connecting link 1 to link 2 and link 2 to link 3 and a final servo located at interface between the arm and the end effectors. The first two servos feature a max torque of 3,402 oz.-in and 180° rotation. Although the intermediate servo connecting link 2 to 3 supports a far lighter load than the servo connecting link 1 to link 2, equally powerful servos will be used at both joints. The decision to keep a stronger intermediate servo motor is due to its multipurpose functionality. The intermediate servo works to power the forward kinematics of the robotic arm as well as provides the power needed when the task requires any form of surface penetration or digging. The final servo motor provides rotational movement for the end effector.

7) Linear Actuator: A standard heavy duty linear actuator will be used to power the first link and 4 bar linkage sub assembly. During early stages of design, linear actuators were considered for the control throughout the entire arm due to its power capabilities. However, the weight of the motors proved to create more complications in design and added excessive weight to the arm. As an alternative, only one linear actuator is incorporated into the design. Ranking the different joints in order of power needed to perform tasks, the linear actuator was assigned to the base link/4 bar linkage sub assembly.

END EFFECTORS For the end effectors, as compared to last year where

only one was used, three end effectors will be interchanged throughout the competition to complete as many requirements as necessary for the three tasks. Last year, due to lack of time, it was impossible to come up with a fully working design; therefore an off the shelf, two finger parallel gripper was used to complete the task. Due to the lack of engineering, the gripper did not allow any of the tasks to be completed. For example, since the gripper was made of only plastic with no type of rubberized finger attachment, there was not enough frictional force to hold or lift items. In addition, this two finger gripper was not able

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to open very wide, making it impossible to grab onto or hold items during tasks. The servo used was also underpowered, resulting in an insufficient amount of gripping force to lift objects. Therefore, it was decided that a completely renovated design had to be made. Many ideas were considered and down selected, as seen in Table XVI, and three end effectors were designed.

Three new end effectors are the result of much thought into how to complete the task. The three end effectors that will be used are, the Longworth chuck, the encompassing grip and the scooper:

LONGWORTH CHUCK FOUR FINGER GRIPPER The Longworth chuck is the end effector that will be

used to perform the service task of the competition. The way in which the Longworth chuck works is that it is able to use the method of the Longworth chucks that are used in the wood industry but it is applied in a smaller scale for a specific task. This chuck converts the rotational motion that is generated by the servo that is attached to the bottom of the end effector, into a linear movement by using spacers that are connected to a plate. Two plates are used each of which have curved slits into them that face opposing directions when placed next to each other.

Figure XIX Longworth chuck design concept with internal view

The upper plate used is formed as a shell to the whole system with the top of the shell being the upper plate and the sides being what surround the lower plate, the spacers, the servos and almost everything of which the end effector consists of. On the other hand, the lower plate is attached to the spacers, which is what keeps it up in place and which is the plate that moves in the chuck when the servo rotates. “Fingers” are inserted through the gap that is formed in between the slits. Thus as the servo rotates, the fingers follow the tangential path of the slit and force them to move inwardly or outwardly. There will be four “fingers that will be placed which are what grab any of the items necessary. Due to the fact that that the fingers move with the trajectory of the path, this end effector is able to open and close varying lengths to be able to wrap around pipes or valves in order to complete the tasks necessary. As can

be seen in the block diagram of how the components are assembled.

Figure XX Longworth chuck block diagram

It is important that the fingers are able to protract to a length large enough to encompass any size valve or a pipe. This is necessary to be able to accomplish the tasks that are required under the servicing task of the competition. Expanding from what was mentioned earlier, the tasks completed in the servicing task are to flip a switch on and off, turn a valve, and to pick up and screw in a pipe. There are unknown dimensions to both the valve and the pipe. Thus with these requirements, a few end effectors were considered as can be seen in the Pugh Chart in Table XIV.

Three different iterations for the end effector were analyzed in order to identify which would be best to use. First is the datum which represents the gripper that was used last year for the competition. Everything is referenced from that, however breaking down the analysis, it can be seen that the two finger parallel gripper is not a good fit for the competition. Due to the fact that this gripper is very small, it is not able to wrap around any item necessary.

SINGLE FINGER ACTUATION GRIPPER To complete the Astronaut Assistance task, a custom

gripper was designed as shown in Figure XXII.

Figure XXI Single finger actuation gripper

This single actuation finger gripper is designed using two stationary plates that house a servo. The housing of this gripper contains a single stationary finger that protrudes outward by approximately1 in. Attached to the main gear hub is a set of fingers with an encompassing capacity range of 0.5 in − 3 in to account for any handle types or sizes that may be experienced during competition. This set of fingers was designed using four layers of sheet

Servo Hub Gear Spacers Lower Plate Upper Plate Fingers

Task (i.e. hold pipe, turn pipe, etc.)

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metal protrusions connected using multiple threaded standoffs. These provide support to the fingers, as well as ensure that the concentricity of the finger workspace is maintained.

Figure XXII Single finger actuation gripper block diagram

Due to the requirements of the competition, the design used for the Astronaut Assistance task must be capable of lifting items weighing approximately 5 kg. Initial considerations, as shown in the Pugh chart in Table XIV, included frictional and encompassing grip types. Although a frictional grip could be designed and constructed, the gripping force required to maintain a reliable grip on a 5 kg object is four times greater than that of an encompassing grip. This is due to the number of contact points of a frictional grip being limited to 2-3 points, rather than the infinite number of contact points of an encompassing grip. This was determined by calculating the gripping force with known mass, acceleration, safety factor, and friction coefficient. Due to the tasks of competition, a friction coefficient of 0.3 was used for the interface between steel and plastic. The gripping force for a friction grip was calculated below.

F =m(g + a)n

µ

F =(5 kg)(9.81m/s)(1)

0.3

F = 163.5 N = 589.075 oz

With this design, the moment arm of the finger is approximately 3 𝑖𝑖; therefore, the torque required for a servo with a friction grip was found using the torque equation below.

𝑇 = 𝐹𝐹

𝑇 = (589.075 𝑏𝑜)(3 𝑖𝑖)

𝑇 = 1767.225 𝑏𝑜 − 𝑖𝑖

This number was then compared to the required force and torque of an encompassing grip.

F =m(g + a)n

4µ

F =(5 kg)(9.81m/s)(1)

(4)(0.3)

F = 40.875 N = 149.518 oz

𝑇 = 𝐹𝐹

𝑇 = (149.518 𝑏𝑜)(3 𝑖𝑖)

𝑇 = 448.552 𝑏𝑜 − 𝑖𝑖

Based on these calculations, the friction grip proved to be much more efficient and reasonable. To account for a factor of safety of 1.2, the servo used in the single finger actuation gripper has a 3:1 gear ratio, resulting in 535 𝑏𝑜 −𝑖𝑖 of torque available during competition.

BULK SAMPLING SCOOP Another task requirement of the URC is the completion

of a Sample Return task. This task requires teams to collect samples, whether in bulk or as cores, that are a minimum of 5 𝑘. In addition to a minimum mass requirement, the sample must also be collected from at least 5 cm below the surface of the soil.

To complete this requirement, many different designs were considered as shown in 𝑇𝑎𝑙𝑙𝑇 𝑋𝑋𝑋 . These designs included a two finger scooping jaw, a single scooping jaw, as well as a coring drill. After multiple iterations and considerations for torque and force requirements, a single bulk sampling scoop was chosen and can be observed in Figure XXIV. This design features a single scoop made of welded sheet metal that is attached to a servo by a simple interface bracket. Since this bracket directly connects to the servo hub on only one side, support on the opposing side had to be considered and a solution was determined. This solution utilizes a binding post that is directly connected to the bracket and is seated in a hole of the servo mount. This allows the forces to be distributed during motion and allow the servo shaft to be supported during sample collection.

Figure XXIII Single scoop bulk sampling tool

Gripper Base Servo Movable

Fingers

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With this configuration, a large sample can be taken by aligning the blade parallel with the soil surface, actuating the servo, and scooping in a shoveling motion. This motion is similar to that seen in bulldozers and construction equipment and will allow the rover to collect bulk samples in the dry desert terrain. The prevent deformation or damage during the sample collection process, the scoop will be constructed using gauge 12 sheet metal that will be cut using a water jet. The pieces of sheet metal that will form into the scoop will be then welded together and fastened to the aluminum servo bracket.

Figure XXIV Bulk sampling sscoop block diagram

SAMPLE ANALYSIS

CONE PENETRATION TESTER A specific portion of the University Rover Challenge is

to be able to have on board science tools. As a requirement, all vehicles must be able to record and analysis pH and humidity levels of soils. As a design solution, initial research is able to tell us of various sampling methods. A cone penetration tester is able to give stratigraphic data and determine how data can change per strata. This can be further expanded to find information regarding materials and temperature of the sub layers. This method will minimize the amount of equipment on the robotic arm and increase the data that can subsequently be recorded.

The cone penetration tester, CPT, will be mounted to the center of the chassis and will have three design components; two degrees of motion and cone housing. The two actuations will be controlled via a servo and linear actuator. To reduce complexity the components will be purchase and an adapter will be created to mount the linear actuator directly to the servo. This will allow for a direct drive to the linear actuator and reduce the amount of moving parts.

Figure XXV CPT motion breakdown

When the linear actuator is in position, it will extend with a maximum stroke length of 8in. The position will be determined when the linear actuator will be orthogonal to the surface at which the rover sits. This information will be extrapolated from the orientation of the chassis and the angle for servo. The servo will have an output of 3.2 ft-lbs. The combined weight of the moving system and extended length requires a maximum torque of .9 ft-lbs. Overall the system is designed with a safety factor of over 3.5. However the calculations are disregarding any stall points.

Figure XXVI Linear actuator directly mounted to servo

The linear actuator is designed by the static weight of the rover. The rover can only weigh a maximum weight of 110 lbs. This will determine how much force the linear actuator can output. The chosen linear actuator for this will output 180 lbs. of force. This will allow for a compensation of the variety of soils. As mentioned the actuator will have a stroke length of 8 inches. The minimum depth required by competition is 2 inches. The 8 inches is to accommodate contact to soil as well as being able to travel deeper than 5 inches into the ground.

Lastly the sensor housing will contain all information with data retrieval. The sensor will have a harden cone shape designed from a 1020 cold steel. This will protect the housing from compression as well as assist with penetration any sediment. The sensors themselves will be

Servo Hub Gear

Support Bracket Scoop

Servo Linear Actuator

Sensor Housing

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analog based sensors. An array of opening will hold contact points. These contact points will connect upon touching soil. This information will be sent up via wires into a microprocessor. The raw data will be sent back to command station to further analyzed.

Figure XXVII Fully extended linear actuator

Figure XXVIII Sensor housing for data retrieval

PROJECT MANAGEMENT TEAM STRUCTURE

As part of the goals of this project, the University Rover Challenge presents certain tasks that are designed to test engineers with real world problems. The tasks are listed as Astronaut Assistance, Equipment Servicing, Soil Sampling, and Terrain Traversing. In order combat the given requirements the overall structure of the rover has been broken into 5 sub-teams that will help achieve certain portions of the combination. It is through the breakdown of the structure of the rover that will achieve not only research in each section, but the improvement from last year’s model. (REF TO WBS IN APPENDIX)

PROJECT SCHEDULING

As this is a required class for senior mechanical engineering students, large milestones are set by the classroom structure to ensure students finish their projects; however due to the nature of a competition, this project is on an accelerated course. In order to place well in

competition, a lot of time has to be spent on testing material the overall design of the rover. To achieve the goals of making the rover on time the project has been broken up into 4 main stages. Design, Manufacturing, Testing, and Fine-tuning are the 4 stages required to ensure a well-designed system.

PROJECT DELIVERABLES

Table I A-Specs for 20115 rover

Design Parameter Requirement

Entire Vehicle Weight < 50 kg

Vehicle Volume < 1 m3

Vehicle Width < 32 in

Functional Temperature Range

Up to 110°F

Minimum Lift Capacity 5 kg

Movement Control Wireless/Remote Control

Minimum Reach Capability

5 cm below ground

Science Tools pH and humidity meter

Video Feed Wireless

Frequency Band 900MHz-2.4GHz

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APPENDICES

Table II Chassis morph chart

Function Solution

Provide Support to

Vehicle C-Channel Bar-Stock Flat, Solid Tubing

Maintain Shape and

Strength Aluminum Steel Plastic PVC Carbon Fiber

Maneuverable Rectangular Box Circular Octagon Square

Provide Space for

Arm and Electrical

Components

Flat Bi-Level -- --

Table III Chassis pugh chart

Function C-channel Bar-stock Flat, solid piece Tubing

Material

Aluminum 0 -1 -2 0 Steel 0 -2 -1 +1

Plastic 0 -2 -2 -1 Carbon Fiber 0 1 0 +1

General Shape

Rectangular 0 -1 +1 0

Circular 0 -2 -2 -1

Octagon 0 -2 0 +2

Square 0 -1 +1 +1

Vertical Shape Flat 0 -1 +1 +1

Bi-level 0 0 0 +1 Support 0 0 -1 +1 Stability 0 -1 -1 +1 Weight 0 -2 -1 0

Cost 0 0 0 +1

Total 0 -14 -7 8

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Table IV Material properties of aluminum and silicon bronze

Material Alloy

Specific Weight � 𝒍𝒍𝒇𝒕𝟑�

Yield Strength

[ksi]

Ultimate Strength

[ksi]

Modulus of

Elasticity [1000 ksi]

Poisons Ratio

Elongation over 2 inch

Gauge Length

[%]

Coefficient of Thermal

Expansion

[𝟏𝟎−𝟔

°𝑭]

Aluminum 6061-T6 170 40 45 10 0.33 30.0 10

Bronze SAE 841 492.48 46 91 14.5 0.34 19.0 12

Table V Suspension morph chart

Function Solution Support Chassis

Weight 8 wheels 6 wheels 4 wheels

Smooth Pivot Points Bearings Bushings None Rocker Length within

A-Specs 14” 15” 12”

Bogie Length within

A-Specs 14” 13” 12”

Attachable to

Assembly 4 Bolt Pattern Single Post Free Single Post Fixed

Support Load 0.25” Tall 0.375 Tall 0.50 Tall Maintain Shape and

Minimize Deflection 0.125” Thick 0.25” Thick 0.375” Thick

Table VI Suspension pugh chart

Function

Datum Type 1 Type 2

Support Rover

Material Aluminum 0 +1 +1

Steel 0 0 0 Plastic 0 -1 -1

Carbon Fiber 0 -2 -2

Provide Traction over obstacles

Wheel Number

4 - +1 +1 6 0 +1 +2

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8 - +1 0

Smooth Pivot

Pivot type

None 0 -2 -2 Bushing - +1 +2 Bearing - 2 +1

Bolt Pattern of Wheel Assembly

4 Bolt 0 +1 +2 Post Fixed - +1 +1 Post Free - +1 -1

Minimize Deflection

Thickness 0.125 - -2 +2 0.25 - -1 +1

0.375 - 0 +1 0.5 0 -1 -1

Stability 0 +1 2 Weight 0 -1 -2

Cost 0 +1 -1 Total 0 2 6

Table VII Differential morph chart

Function Carbon Fiber Datum Aluminum Differential Shaft (3 Bevel Gears)

Aluminum Differential Shaft (4 Bevel Gears)

Strength 0 +1 +2

Weight 0 -2 -2 Cost 0 +1 +1

Reliability 0 +2 +2

Simplicity 0 +1 +1

Manufacturability 0 +1 +1

Stability 0 0 0 Total 0 4 5

Table VIII Differential pugh chart

Function Carbon Fiber Datum Aluminum Differential Shaft (3 Bevel Gears)

Aluminum Differential Shaft (4 Bevel Gears)

Strength 0 +1 +2

Weight 0 -2 -2

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Cost 0 +1 +1

Reliability 0 +2 +2

Simplicity 0 +1 +1

Manufacturability 0 +1 +1

Stability 0 0 0

Total 0 4 5

Table IX Wheel morph chart

Function Solution

Maintain Traction Rubber Cleats Pneumatic Foam and Tread

Meet Size

Requirements 8 in 10 in 9.5 in

Motor Placement

Protects Power

System

Gearbox Away from Wheel Gearbox Above Wheel --

Should be Light

Weight Rubber Aluminum Stainless Steel

Must be Easy to

Manufacture

Single Piece Aluminum

Configuration

Pocketed Single Piece

Aluminum Configuration

Separately Machined

Aluminum Plates

Table X Wheel pugh chart

Function Enclosed Wheel Solid Block (External) Solid Block (Internal) Multi-Plate

Motor Location 0 +2 +2 +3

Structural Strength 0 +2 +2 +1

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Weight 0 -3 +2 +3

Cost 0 -1 -3 -2

Reliability 0 +2 +1 +2

Simplicity 0 +2 -3 +2

Moment about Pivot 0 -2 -1 +3

Manufacturability 0 -2 -4 -1

Total 0 -14 -7 8

Table XI Robotic arm morph chart

Function Solution

Control and Power Systems Linear actuator Servo Stepper Motor Closed loop linkage

Must Attach to Gripper Interface Bracket Directly Mounted Stepper Motor Ball screw

Should Be Stowable Pre-Programmed

Upward Configuration

Pre-Programmed Downward

Configuration

Manual Upward Configuration

Manual Downward Configuration

Length Must Have Sample Collection

Reachability 25” 36” 20” 18”

Workspace Must Allow for Task

Completion Below Above Adjacent to the

chassis All the above

End Effector Must Have Position Capabilities

Linear actuator Servo Stepper Motor Ball screw

Must Be Mounted to

Chassis Top Bottom Center Rear

Table XII Robotic arm pugh chart

Functions 4 DOF 4 DOF 5 DOF 6 DOF

Structural Stability 0 +2 +1 -1

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Durability 0 +2 +1 -1

Stowable 0 +1 +1 +1

Power 0 +1 +1 +1

Maneuverability 0 +1 +2 +3

Weight 0 +1 -1 -2

Cost 0 +1 -1 -2

Total 0 9 4 -4

Table XIII End effector morph chart

Function Solution

Multi-Task Functionality Removable Gripper Fingers Removable Gripper Removable Final Linkage

w/ Gripper

Sample Collection Capability Scooping Jaws Sample Coring Drill Sample Coring Probe

Sample Containment Capability Glass Beaker on Top of Chassis Canvas w/ Framing on Side

of Chassis Bag Attached to Gripper

pH Analysis Capability pH Cards in Sample Receptacle pH Probe in Sample

Receptacle Electronic pH Sensor w/

Arduino

Humidity Analysis Capability pH Cards in Sample Receptacle Humidity Probe in Sample

Receptacle Electronic Humidity Sensor

w/ Arduino

Astronaut Assistance Capability

3 Finger Gripper with Independent Control

3 Finger Gripper with Overall Control 2 Finger Gripper

Servicing Task Capability

Re-use Astronaut Assistance Gripper

Conveyer Belt Finger Gripper 3 Finger Angled Gripper

Table XIV End effector pugh chart

Function Datum Type 1 Type 2 Type 3 Type 4

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Weight 0 -3 +2 +2 -1

Cost 0 -3 +1 +1 +1

Reliability 0 +2 -2 -2 +2

Simplicity 0 -4 +1 +2 +1

Durability 0 0 -2 +2 +2

Easily Adjustable 0 -4 +1 +3 +2

Task Achievement 0 4 +1 +2 +3

Manufacturability 0 -4 +2 +2 +1

Figure XXIX Project schedule and GANT chart

Table XV Team structure by sub-team division

Team Lead

Christopher Nguyen

Chassis Robotic Arm Suspension Telemetry Wheel Jerame

Taylor Lauren

DuCharme Ken Greene Maria

Gutierrez Greg

Maisch

Yolanda Mora Quy Tran

Matt Wolenden

Chris Thompson

Melanie Valenzuela

Daniel Lu

Nathan Johnson

Carrisa Pariseau

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