Post on 21-Jan-2016
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Multi-Chamber Programmable Air Cushion (MC-PAC)
Joli-A Kabamba
Masahiro Ohno
Scott Paik
Joe Suarez
The Pressure Ulcer Problem
• Tissue damage caused by restricted
blood flow, friction, and shear force
• Found on 12.3% of all hospitalized
patients. 4% of patients die from it
• Prolonged hospital stay up to 5
times longer than patients without
pressure sores Picture courtesy of the National Pressure Ulcer
Advisory Panel (NPUAP)
MC-PAC
• Programmed system to control distribution of
individual air cell pressure in the cushion
• Based on suggestion from Shepherd Spinal Center to
reduce occurrence of pressure ulcers on paraplegic
patients in wheelchairs
• Sponsored by Texas Instruments Analog University
Design Competition
• Expected price: $2,000.00
Design Objectives
• Provide automated means of pressure relief for
wheelchair bound
• Minimize risk of friction, shear force on skin
• Maximize user comfort
• Easy to use
• Operate on 12V battery
Technical Objectives
• Maintain pressure in air cells at set levels
• Remap contact pressure distribution on cushion
periodically, as suggested by NPUAP
• Use microcontroller to display status of each air
chamber
• Pressure configuration changeable by user via
intuitive user interface (UI)
MC-PAC Block Diagram
Microcontroller(TI MSP-430)
User Interface
Cell Pressure Sensors
Air Pump5x5 Air Valves
5x5 Air Cells
Air ReleaseAir Intake
Signal
Air
PRESS?HI LOW
OK
Pressure Regulation AlgorithmAlgorithm is programmed to maintain set pressure in individual air cells
CHECKSENSOR
(X,Y)
DELAYPRESS
HI LOW OK
DUMP SOME AIR
ADVANCE (X,Y)
COUNT
HI HI LOW
OK
OK
DONE
DONE
LOW
START
Sequential Control
Control Panel
• User Interface consists
of three switches and
one knob
• User can stop/switch
cycle, or change cycle
time
• Control panel displays
cell status
Display
Power Hold
Next Cycle
Timer
Parts Acquired for Project Build
Pressure sensors
5x5Air Cushion Air
Valve
Air Pump
MSP430LaunchpadMOSFET
Switches
Design Challenges / Alternatives
• Number of Cells
• More cells better for user comfort
• Up to 25 cells controllable by single MSP430
microcontroller
• Difficulty to construct custom cushion
• Cell sealing challenges
• Project time constraints
Development CostProject Component
Labor Hours
Labor CostsEquip. Costs
Total Cost
Algorithm Coding 160 $6,400.00 $6,400.00
Simulation 160 $6,400.00 $6,400.00
Code Debugging 80 $3,200.00 $3,200.00
Pressure Control Device Design 50 $2,000.00 $200.00 $2,200.00
Cushion Design 150 $6,000.00 $300.00 $6,300.00
Prototype Product Design (Tech Demo) 200 $8,000.00 $1,407.97 $9,407.97Final Product Design (Improved Prototype) 200 $8,000.00 $1,500.00 $9,500.00
Testing, Demo Preparation 160 $6,400.00 $6,400.00
Lecture / Group Meetings 300 $12,000.00 $12,000.00
Total Labor 1460 $58,400.00
Fringe Benefits and Overhead $113,324.00 $113,324.00
Total Parts Cost ($) $3,907.97
Project Total $175,621.97
Production Run Cost
Production Item Cost
Development Cost per Unit $35.00
Assembly Labor (2 hr) $40.00
Testing Labor (1 hr) $20.00
Customer Support (5 hr) $100.00
Fringe Benefits (30% of Labor) $48.00
Production Equipment ($500,000) $100.00
Material Cost $411.00
Overhead and Sales Expense $943.00
Selling Price $2000.00
Profit Per Unit $303.00
• 5,000 units for 5 years
Components Selected, Tested, Integrated
• Semiconductor switches (TI)
• Air compressor (Ryobi)
• Pressure transducer (MSP-2202-ASX)
• Solenoid Valves (GEMS-M-SERIES)
• Air Cushion (ROHO MOSAIC)
• MCU (Texas Instruments MSP430)
Project Milestones
• March 25th : Modify ROHO seat cushion.
• March 28th : Mount the sensors and valves to the
air regulation block.
• April 4th : Complete circuits and wiring harnesses
• April 18th : Develop and calibrate the MCU
algorithm.– Control inflation and deflation of cells.
Future Improvement
• Graphical Display Touchscreen.
• More air cells, moisture control, and temperature
control.
• Custom user pressure mapping interface.
• MC-PAC for car seats and beds.
• Make profile smaller, quieter, lighter, and more
efficient.
Questions