Team P14029: McKibben Muscle Robotic Fish Project Manager: Zachary Novak Mechanical Design Lead: John Chiu Lead Engineer: Seaver Wrisley Controls and Instrumentation Lead: Felix Liu

Agenda Project Background Propulsion System Feasibility Problem Statement Pressure Drag Calculations Deliverables McKibben Muscle Test Results Updates to Engineering Reqs Control System Feasibility Feedback from Last Review Electronics Schematic Concept Breakdown Logic Flow Chart Internal System Diagram Microprocessor Options/Selection Subsystem Identification Solenoid Options/Selection Critical Subsystem Identification Solenoid Control Circuit Schematic Orientation Control Feasibility Kinematic Analysis Preliminary Subassembly Design Buoyancy Calculations Design Concept CAD Power System Feasibility Materials Updated Budget Assessment Power Flow Analysis Power Source Selection Updated Risk Assessment Battery Life Analysis Detailed Design Schedule

Project background

Problem Statement This project is designed to prove the feasibility of McKibben muscles for use in underwater robotic applications, and to develop core technology and a platform for other teams to use in the future. The project specifically seeks to develop a soft-bodied pneumatic fish that looks, moves, and feels like a fish. The robotic fish should be capable of swimming forward, backward, and turning, most likely using Body Caudal Fin propulsion, and the primary mechanism for generating the swimming motion must be McKibben muscles.

Deliverables A functional prototype which meets all customer requirements, and that may be used as a platform to be expanded upon by future MSD teams Detailed documentation covering project design, testing, and fabrication Appropriate test data ensuring all customer needs are met Detailed user manuals for operation and troubleshooting Suggestions for future expansion

Engineering Requirements Selected engineering specifications Maximum turning radius: Two body lengths Maximum height: 3 feet Operation time: .25 hour Corrosion spec: ASTM B-117 Safety Maximum voltage present: 24V DC Maximum allowable pressure: 70psi Maximum pinching force in joints: 10lbs Body and fin motions: 30% tolerance to published values (next slide) This will be difficult to see, maybe we should mark this up to focus on important sectors and/or blow up certain part(s) of it

Questions from last review Buoyancy Calculations How do known components affect the buoyancy? Will we be able to offset this to achieve our neutral buoyancy desired? Power Analysis How much power is needed to run the components and how does that translate into expected operating time? Spatial Analysis How will all the components fit? How big will the robot be? Muscle Testing In the operating range of the centrifugal pump, will the muscles be able to produce enough force/displacement to make the fish “swim”?

Concept Breakdown

Internal system diagram

Subsystem Identification Skin Control System Body Structure Microcontroller Voltage Regulation Frame/Supports Programming Locomotion System Wiring Linkages Orientation System Muscles Air Bladders Actuation System Power System Pump Battery Solenoids Manifold Waterproofing Plumbing

Critical Subsystem determination Guidelines Highest Technical Risk Most Challenging Technically Most Important Engineering Requirements Most Important System Level Behavior

Critical Subsystem Determinations Actuation System Locomotion System Control System Power System Honorable Mention: Orientation Control System “Propulsion System”

Orientation control system feasibility

Buoyancy Calculations

Design idea Inflatable Air Bladders Side Mounted (Trim Tanks) Will allow Roll Control Front and Rear Bladders Will allow Pitch Control Passive System Manually inflate Fine tune for neutral buoyancy before run Butyl/Schrader Valve Capacity (4 total) 20-25 cubic inches each Easily fit design footprint Feasible

Power system feasibility analysis

Power flow chart

Power consumption (Main components) Thanks Thermoelectric team!

Summary Found that Lithium polymer batteries were the best combination of power, weight, and cost. Does require the use of a “smart charger” for safe charging. Presents additional risk item: Battery catching on fire, happens during charging if done incorrectly. Action to mitigate risk: Design fish such that battery can be removed for charging.

Decision/lifetime analysis Class: Lithium Polymer (LiPo) Specs: 25.9V, 4 Amp-Hour (4000mAh) Weight: 1.41 pounds Cost: $52 Expected Battery Life Analysis

Propulsion system feasibility analysis

How much force is required? Pressure and friction drag forces act to slow the fish down The muscles, in order to move the fins, must overcome: Pressure drag of the fin due to rotation Pressure drag on the fin due to apparent incoming fluid velocity Reactions from the other fins Friction drag slows the fish, but is NEGLIGIBLE as far as muscle force is concerned

Preliminary Drag Calculations

Free body Diagrams

Drag Calcs (continued) The pressure drag force is dependent on the perpendicular velocity squared. The torque is found by integrating the drag force times distance along the fin section.

Drag calcs (continued)

Drag calcs (continued)

Muscle testing Test Rig Components: LabVIEW Interface Load Cell Air Compressor Data Gathered Force vs. Pressure Deflection vs. Pressure To get Strain (%)

1st Round of Testing - lessons Dead zone due to space between tubing and fabric mesh. 30 psi was the pressure required to take up the initial slack between the tubing and mesh. Slope inversely related to rubber stiffness, and directly related to the ratio of inner circumference over wall thickness

2nd round of testing Assembled new muscles with existing tubing and fabric mesh. Used tubing with high inner circumference to thickness ratio (it was thinner). Made sure there was no space between tubing and mesh. Tested the effect of using a slightly smaller mesh than needed, on the same tubing.

2nd testing session results Tighter mesh nearly eliminated the dead zone Obtained a force of approximately 4 pounds at 20psi

2nd testing session results No significant difference seen between mesh types as long as they are tight to the tubing, ~13% contraction @ 20psi

Force feasibility Force required due to overcome pressure drag with a muscle lever arm of 4cm (1.57”): 1.83 pounds Force produced by first set of muscles: 4 pounds Reaction forces from other fin sections are significant, but also actuate out-of-phase. Are ultimately due to the drag as well, so should be on the same order. Clearly within feasibility, using a muscle assembled from a limited selection of scrap materials.

Strain feasibility Strain level of 13% at 20psi found during testing. A lever arm of 4cm, and maximum angle of 30 degrees requires a 30.8cm (12.2”) muscle Has to actuate the section 30 degrees, as well as accommodate 30 degrees of motion in the other direction Larger muscles can be used, making it possible to lower the lever arm length, decreasing the required muscle length.

Control System Feasibility analysis

Electrical control Schematic

Logic diagram

Microcontroller options

selection: Arduino mega 2560 PROS Vast amount of resources available 54 Channel for future expansion capability 8 KB SRAM Ease of coding and debugging Shields compatibility Used by Roboant team CONS More expensive ($50)

Solenoid valve options Key requirements: Inexpensive Compatible manifolds Ease of system integration (electrical connections) Reliability Additional considerations: Prior experience (reputation)

Solenoid selection: Pugh analysis Clippard valves were selected as the best option Superior for all critical aspects except for power consumption

Selection: Clippard 15mm 3-way Valves 12V and 24V choices Moderate but acceptable power consumption Several manifold options Variety of wiring options Least expensive, total cost around $160 Used in previous air muscle projects at RIT, such as muscle test stand Professor John Wellin has been using them for several years controlling flow of water * There are some similar valves in the lab currently that we will can use for testing purposes. If they end up working well enough we may not need to purchase these at all.

Solenoid control circuit

Fish Motion Analysis Forward Tuning Parameters Turning Tuning Parameters Value l1 [in] 12 l2 [in] 6 l3 [in] 3 l4 [in] Theta_1 [deg] 20 Theta_2 [deg] Theta_3 [deg] Theta_4 [deg] 10 Theta_2 Phase Delay [Rad] Theta_3 Phase Delay [Rad] Angular Frequency [Rad/Sec] 6.28 Forward Tuning Parameters Value l1 [in] 12 l2 [in] 6 l3 [in] 3 l4 [in] Theta_1 [deg] 30 Theta_2 [deg] 45 Theta_3 [deg] 75 Theta_4 [deg] 10 Theta_2 Phase Delay [Rad] 3.5 Theta_3 Phase Delay [Rad] Angular Frequency [Rad/Sec] 6.28

Preliminary Subassembly Design Side View 13.5in 36in

Isometric view

Preliminary Subassembly Design Front View

Preliminary Subassembly Design Top View Air Bladders Tail Segments Sealed Compartment Pump Air Muscles

Preliminary Subassembly Design Sealed Compartment Arduino Microcontroller Foam or other structure Battery Solenoid Block

Preliminary Subassembly Design Materials Outer skin and fish structure Wire mesh for contoured outer shell Larger gauge wire to support the wired mesh Skin can be made of molded silicone, waterproof fabric, etc. Sealed Compartment Made from acrylic/plexiglass walls for visibility of internals The walls will be sealed with waterproofing silicone filler along the seams. Tail Segments ABS plastic or HDPE (high density polyethylene)

Updated budget projection This leaves ~$200 for: Plumbing Body/Skin Structures Wiring McKibben Muscles Air Bladders Linkages

Risk Assessment scale

Risk Assessment updates

Schedule: Next gate

Questions? Concerns? Feedback?