Transcript Power System Feasibility

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
• Problem Statement
• Deliverables
• Updates to Engineering Reqs
• Feedback from Last Review
• Concept Breakdown
• Internal System Diagram
• Subsystem Identification
• Critical Subsystem Identification
• Orientation Control Feasibility
• Buoyancy Calculations
• Design Concept
• Power System Feasibility
• Power Flow Analysis
• Power Source Selection
• Battery Life Analysis
•
Propulsion System Feasibility
• Pressure Drag Calculations
• McKibben Muscle Test Results
• Control System Feasibility
• Electronics Schematic
• Logic Flow Chart
• Microprocessor Options/Selection
• Solenoid Options/Selection
• Solenoid Control Circuit Schematic
• Kinematic Analysis
• Preliminary Subassembly Design
• CAD
• Materials
• Updated Budget Assessment
•
Updated Risk Assessment
•
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)
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
• Programming
• Wiring
• Orientation System
• Frame/Supports
• Locomotion System
• Linkages
• Muscles
• Actuation System
•
•
•
•
Pump
Solenoids
Manifold
Plumbing
• Air Bladders
• Power System
• Battery
• Wiring
• Waterproofing
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
“Propulsion System”
• Control System
• Power System
Honorable Mention: Orientation Control 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
Battery type
Lithium polymer (LiPo)
Lithium polymer (LiPo)
Lithium ion
Lithium ferrophosphate (LFP)
Ext. Price
$51.98
$64.58
$112.48
$121.20
Volts
25.9
25.9
25.9
25.6
mAhr
4000
5000
4400
3600
Weight (lb)
1.41
1.8
1.97
3
•
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
Component
Voltage Quantity
Peak
Amperage
Watts
• Class:
Lithium
BLDC
50E series
pump*Polymer (LiPo) 24
1
3.6
86.4
• Specs:
25.9V,
Amp-Hour
Solenoid
valves
(only4half
at once) (4000mAh)
24
2
0.104
2.5
• Weight: 1.41 pounds
Microcontroller
TBD
1
Negligible Negligible
• Cost: $52
Total:
3.70
88.90
*assuming worst case of maximum flow
Expected Battery Life Analysis
Battery Voltage (V)
25.9
Battery Capacity (Ah)
4
Battery Capacity (Wh)
103.6
Expected Battery Life (Hours)
1.17
The customer requirement for
power is only 15 minutes. It is
important to have long enough
battery life to make testing
proceed quickly, but there is
room to cut back here
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)
Clippard
Power consumption
Cost
Manifold options
Wiring options
Prior experience
Size
Totals:
DATUM
SOLENOID SELECTION: PUGH ANALYSIS
Parker
+
-
Omega
-
NITRA
+
s
s
s
Pneumadyne
s
s
s
+
s
-
1
0
5
0
0
6
1
0
2
0
0
3
• 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
l1 [in]
l2 [in]
l3 [in]
l4 [in]
Theta_1 [deg]
Theta_2 [deg]
Theta_3 [deg]
Theta_4 [deg]
Theta_2 Phase Delay [Rad]
Theta_3 Phase Delay [Rad]
Angular Frequency [Rad/Sec]
Value
12
6
3
3
30
45
75
10
3.5
3.5
6.28
Turning Tuning Parameters
Value
l1 [in]
12
l2 [in]
l3 [in]
6
3
l4 [in]
3
Theta_1 [deg]
20
Theta_2 [deg]
20
Theta_3 [deg]
20
Theta_4 [deg]
10
Theta_2 Phase Delay [Rad]
0
Theta_3 Phase Delay [Rad]
0
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
Air Muscles
Sealed
Compartment
Pump
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:
• Body/Skin Structures
• McKibben Muscles
• Linkages
• Plumbing
• Wiring
• Air Bladders
RISK ASSESSMENT SCALE
Likelihood Scale
Severity Scale
1
This cause is
unlikely to
happen
1
2
This cause
could
conceivably
happen
2
3
This cause is
very likely to
happen
3
The impact on the project is very
minor. We will still meet needs on time
within budget, but it will cause extra
work
The impact on the project is
noticeable. We will deliver reduced
functionality, go over budget or fail to
meet some of our Engineering
Specifications
The impact on the project is severe.
We will not be able to deliver anything,
or what we deliver will not meet the
customer's needs
RISK ASSESSMENT UPDATES
SCHEDULE: NEXT GATE
QUESTIONS?
CONCERNS?
FEEDBACK?