Team P14029: McKibben Muscle Robotic Fish

Transcription

1 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

2 AGENDA Project Goal Overall Concept System Breakdown Head & Tail Frame Construction Orientation System Foam Contours and Skin Muscles & Actuation Pressurization & Flow Diagram Electronics & Power Supply Solenoids Preliminary Microcontroller Logic MSDII Test Plan Feasibility Testing BOM & Budget Risk Assessment and MSDII Preliminary Schedule

3 PROJECT GOAL Use McKibben muscles to power a robotic fish

4 OVERALL CONCEPT Morphological Analysis and Concept Selection resulted in: An untethered fish controlled by a microcontroller (Arduino) with onboard power and fluid pressurization An acrylic box in the head housing the electronics and pump Arduino, water pump, and solenoid valves controlling the flow of water Muscles in the head actuating tail segments via fishing line cord Passive air bladders and weights to control buoyancy, pitch, and possibly roll

5 INTERNAL SYSTEM OVERVIEW

6 SUBSYSTEMS Frame Head Tail Locomotion System Linkages Muscles Actuation System Pump Solenoids & manifold Plumbing Electrical System Microcontroller Batteries Shields Sensors Orientation System Air Bladders Appearance Foam Skin

7 FRAME - HEAD Head box is going to be segmented into two sections Lower section for pump and solenoids things that are likely to leak Upper section for Arduino and battery, completely sealed in order to add another level of water protection Box is constructed from 3/8 and 1/4" acrylic sheet Lid is going to be secured with machine screws outside of a rubber gasket

8 FRAME HEAD SEALING Custom Fabricated Waterproof Design Constructed of Acrylic Main walls 3/8, tray and lid are 1/4 Water lines in and out via push-to-connect bulkhead fittings 1/8 SBR gasket material to seal lid Waterproofing at corners acrylic glue along joint, silicone caulk on inside and outside of corner for a triple seal Specifically redesigned to cut cost of material by using 1/4 and 3/8 material obtained from shop scrap Fully sealed Arduino compartment Wiring routed out of Arduino compartment via a ribbon cable and sealed with silicone

9 FRAME - TAIL Tail segments and parts are identical for speed of machining Each tail segment has: Two acrylic plates forming the sides of the section HDPE end pieces with #8 bolts as joints. Another piece allows the fishing line (actuation cables) to pass through the center of rotation to avoid unintended actuation of other fins Aluminum angle brackets and adjustable mounting bars for attaching the fishing line to the tail segments at varying lever arm distances Tail fin Base of fin is a thin aluminum sheet Rest of fin is custom molded around it using Dragon Skin moldable silicone

10 ORIENTATION SYSTEM Center mass is at the center, both side to side, and front to back.

11 ORIENTATION SYSTEM Buoyancy calculations Not accounting for the foam, the weight of the entire model is 15.6 pounds The buoyancy force due to the main box in the head is 15.1 pounds. Pretty close on buoyancy Foam will give additional buoyant force Always have the possibility of adding extra weights strategically to fine tune

12 ORIENTATION SYSTEM Air bladders will be used to further control the orientation of the fish, both side-to-side, and pitching forward and back. Will not be an active system will inflate manually to make the fish neutrally buoyant and upright. Will use (3) arm floaties as the air bladders One on either side of the fish s head, and one in the front section

13 FOAM SECTIONS Purpose of foam sections Gives fish body the correct profile Assist with buoyancy We already have the foam Secured to the frame by Velcro for easy assembly and disassembly Placed along the sides of the head and tail sections, as well as at the nose Manufacturing process (we already have the foam) Stack and glue foam sheets together into a lay-up Cut them into the correct shape using Dr. Gomes CNC foam cutter

14 LIFELIKE OUTER SKIN Custom molded skin using brush-on silicone products Construction Process: Custom Carved Styrofoam Mold Brushed on Dragon Skin Silicone Green Silicone Pigment for Added Realism Spandex material section to help secure and to aid easy on/off Will be following tutorial for technique found on manufacturers website (

15 MUSCLES Muscles are attached to the underside of the head, to the front piece of the box. Total of 6 muscles (2 muscles for each of the 3 joints) Construction 1/2 ID x 1/16 thick x 8 long latex tubing (ID x thickness x length) Black PET mesh Barb-plug rear fitting and custom machined nylon front fitting Stainless steel hose clamps Muscles have been tested in the lab and have proven more than sufficient to actuate the fin in water 1/2 diameter muscle design will be more compact than the previous 1 diameter muscle design

16 USING THE FORCE Force Transferred from muscles to fin sections via 80-pound tensile strength braided fishing line Eye Bolts screwed into muscle plugs, sealed Teflon tape/silicone as attachment points on muscles Fishing line will be routed through 1/16 Teflon PTFE tubing to reduce chafing and prevent sloppy lines Guide points built into the design to help run lines Features at the front and rear of the box Guided at the beginning of each tail section Affixed to adjustable lever arms extending from fin sections to aid fine tuning of motion

17 PRESSURIZATION Pump is located in the bottom of the box Pump has been upgraded to a 100PSI version to eliminate minimum pressure concerns for force and strain, in addition to eliminating $40 from budget Only design change induced is pump goes in the lower portion of the box (it s not submersible) One was already bought by the arm team, and is currently being used for testing in the lab Water is pulled through a bulkhead fitting into the box, pressurized by the pump, sent into the solenoid manifold, and out through multiple bulkhead fittings to the muscles before being exhausted back to the atmosphere. See schematic on next slide

18 FLOW DIAGRAM

19 ELECTRICAL SYSTEM

20 POWER SOURCE Main power source will be (2) 11.1V Li-Po Batteries LiPo batteries are lightweight and cost effective, but only come in multiples of 3.7V Batteries will be connected to the solenoids in series for 22.2V output Solenoids expect 24V, +/- 10% Batteries will be connected to the pump in parallel for 11.1V output Pump expects 12VDC This configuration allows us to run the 12VDC pump and the 24V solenoids, a large cost savings Also avoids having to fit another component and have the power loss with using a step-down or step-up converter

21 ARDUINO ELECTRONICS An Arduino Mega has been purchased, has a total of 54 I/O pins, which is plenty. Continually checks conductance sensor(s) for water present at the bottom of the box (will trigger Arduino to turn everything off). Fuse protects the Arduino from power surges LED lights to indicate main power on, low battery, high condensation (green/yellow/red) Controls the pump via a relay shield Controls the solenoids through a Power Driver Shield Kit

22 SENSORS AND SWITCH Waterproof Temperature Sensor V Input Voltage -55 C to +125 C temperature Range Rain Detector Module Detect water ingression in the box with a conductive pad 5 V Input Voltage LiPo Fuel Gauge to monitor Battery Level ON/OFF Button to control Arduino Power

23 Single-Pole Double Throw Rated for up to 10 A PUMP RELAY

24 Power Driver Shield Kit 6 PWM outputs Power MOSFETS Max VDSS 60 V MAX ID 30 A SOLENOID CONTROL Arduino Ports Power Driver Shield Solenoids Muscles D2 JP1 1A 1A D3 JP2 1B 1B D4 JP3 2A 2A D5 JP4 2B 2B D6 JP5 3A 3A D7 JP6 3B 3B

25 SOLENOIDS Going to use the SMC NVJ way model Have already tested and proved water compatibility (short-term) in lab experiments, unlike the yellow Clippard solenoids which fail to operate with water Verified sufficient flow rate and were able to actuate our test fin Max pressure of.7mpa (101psi); pump has static head of 100psi Budget Concerns Found in the lab and given permission to use, resulting in a large cost savings. But there are only 3 left that are fully operational, now need to order 3 more (-$35/piece) straining our already overextended budget

26 ARDUINO LOGIC IMPLEMENTATION

27 MSDII TEST PLAN Pump Verify maximum current draw and static head Electronics Box Test Waterproofing of all fittings/seals before sensitive electronic equipment Motion Analysis Compare period and phase shifts to accepted values Measure turning radius Fish Resemblance Conduct student body poll: 1 (that s not a fish) 10 (real fish) Operating Time Run fish until low battery indication to verify minimum run time is met

28 FEASIBILITY TESTING

29 FEASIBILITY TESTING Muscles: ½ Diameter, 8 long Fin: 6 long, 45 degrees of angular displacement in each direction Solenoid opening duration: 2 seconds Delay between two muscles: 2 seconds Testing Fluid : Water Pressure : Up to 100 psi (max pressure of pump) Microcontroller : Arduino Uno controlling two solenoids using transistors

30 FEASIBILITY TESTING

31 BOM AND BUDGET ases Currently have $575 of projected expenditures, including $50 for unforeseen expenses. Options to reduce cost Reducing the number of joints (not recommended) - $70 on solenoids Use roll of gasket material in lab instead of buying new SBR gasket (could compromise sealing) - $9 Reduce battery life from 2.4 hours to.9 hours - $32 (assuming the solenoids have enough power when the battery nears depletion)

32 RISK ASSESSMENT UPDATES

33 PROJECTED MSDII SCHEDULE

34 PROJECTED MSDII SCHEDULE

35 QUESTIONS? CONCERNS? FEEDBACK?