Detailed Design Review P09009: Wheelchair with One –Arm Operation Michelle Allard (ME) Sean Bodkin (IE) Deborah Chen (IE) Nick Rehbaum (ME) Brad Stroka (IE) Alex Vogler (ME)

Project Overview Background: Stroke patients often lose function of one side of their body. Electric wheelchairs have some disadvantages including not being foldable and expensive. There is a potential market for a foldable, manual wheelchair that can be propelled and steered with one arm. Purpose: The purpose of this project is to design a one-arm, manual-powered wheelchair that can be operated by stroke patients or any other individual who has a reduced capacity to perform bilateral operation of a standard manual wheelchair. Typical wheelchairs are not easily operated by individuals who lack full use of both upper extremities. The desired wheel chair will enable stroke patients to independently power and steer the manual chair.

Customer Needs Hierarchy Need 1: Ease of Use Need 1.1: Must be useable by persons with one arm (10) Need 1.2: Must be able to fold for easy transport (7) Need 1.3: Must be easy to maneuver by user Can be maneuvered through standard width of doorway (10) Must be able to turn comfortably during day-to-day operation (10) Straight line deviation must be minimal (10) Need 1.4: Must allow for a second individual to push the wheelchair easily (5) Need 1.5: Minimal number of user control interfaces (7) Easy to assemble and disassemble (4) Need 1.6: Must be able to use the brakes on both wheels and remain stationary on ramps (5) Need 1.7: Should be able to traverse difficult terrain (6) Need 2: Safety Need 2.1: Forces applied must be safe to user (8) Need 2.2: Should handle weight of 95 th percentile male user and below (7) Need 2.3: Should be within safe boundaries for arm range of motion (5) Need 2.4: Minimize possibility of pinch points for grips (8) Need 2.5: Should be comfortable for long periods of time (3+ hours) (4) Need 2.6: Wheelchair weight should be minimal (4) Need 2.7: Should be within safe boundaries for grip strength (7) Need 3: Economics Need 3.1: Should be within budget of around $1500 (7) Need 3.2: Should be able to be easily reproduced in manufacturing environment (4) Need 3.3: Should be adaptable to different users with minimal changes (4) Need 4: Aesthetics Need 4.1: Must have good style (3)

Target Specifications

Target Specifications (Cont’d) Assumptions: -Wheelchair is for home use and surrounding environment. (Includes nursing homes and long term care facilities) -250lbs weight limit is 95 th percentile male - End user is stroke patient with sufficient use of one arm and one leg. Importance Ranking High Medium Low

System Design Model Figure A Figure B

System Design Model (Cont’d) Figure C Figure D Figure E

Bill of Materials

Project Background Load Constant (LC)=51lbs. Horizontal Multiplier (HM)= (10/H) Vertical Multiplier (VM)= ( |V-30|) Distance Multiplier (DM)= ( /D) Asymmetric Multiplier (AM)= ( A) Frequency Multiplier (FM)= table Coupling Multiplier (CM)= table LI>1: Task is increased risk for some. LI>3: Task is high risk for most.

Grip Strength Analysis

Lever Height Analysis

Force Calculations Constraints and assumptions: Lever push angle = 30o (based on experimental data) Lever reset time = 0.4 sec (based on experimental data) Lever push time no shorter than 0.4 sec (based on experimental data) Frictional losses are a function of speed (Figure 9) Frictional losses found experimentally Assumed stopped at 3% of initial speed The lever does not start at rest but at 0.01 rad/s 40 N hand force can be maintained 120 N hand force can be exerted for short periods 2 miles/hr is a comfortable and safe speed for indoor application

Force Calculations (Cont’d)

FMEA

Risk Assessment

Doorway Test This test is designed to verify the need of a wheelchair to fit through a standard doorway. The individual will maneuver the wheelchair using the lever through a standard doorway 30” in width. The distance from both the left and right side of the wheelchair to the doorway will be measured and recorded. The right side will be measured from the farthest point of the wheelchair whether it is the hand or the wheelchair itself. A failure occurs when the wheelchair does not fit through the doorway while the individual is propelling.

Turning Radius Test The purpose of this test is to determine the wheelchair’s turning radius. This radius must be acceptable to turn in a standard hallway which may nor may not have other objects. Also, turning will occur in the room or residence. Therefore, the smallest possible turning radius is desirable. This test will be run with several subjects each running several trials in hopes of eliminating variability and obtaining an accurate measurement. Process: 1. Subject sits in wheelchair 2. Grabs lever at “starting” position 3. Chalk/Mark the starting location of the wheels 4. At rest engage one of the parking brakes 5. Apply force to turn chair 6. Complete 180 degree turn 7. Mark ending location of wheels 8. Measure/Record

Straight Line Test This test is designed to verify the customer need of maintaining movement in a straight line without the need to correct using one’s feet. The individual conducting the test will place a 50ft string on an area of level ground that does not contain any obstructions and align the wheelchair so that the string is in the center between the two wheels. There will be two parts to this test. In the first part of the test, the individual will propel the wheelchair using the lever with both feet on the foot rests for the full 25ft. Deviation from the line in inches will be recorded below at the 25ft mark. In the second part of the test, the individual will propel using the lever and also have the ability to correct with their feet in order to maintain straight line movement. The number of corrections and power pulses will be recorded. A “power pulse” is considered a round-trip movement of the lever. A failure occurs when the ratio of corrections to power pulses is greater than 1 to 1. Part 1:Deviation without corrections (inches): ___________ Part 2:Number of corrections _________ Number of power pulses _________ Ratio_________

Grip Strength Test The purpose of this test is to determine that grip strength to engage the braking mechanism is acceptable. Based on the design there will be two brake handles, one for each wheel, which will enable turning. In order to slow down the entire chair both brake handles must be engaged. The target force is 6 KG based on user studies. Confirm this is achievable through grip strength on force gage and brakes. Braking distance should also be reasonable. Process: 1. Subject sits in wheelchair 2. Grabs lever at “starting” position 3. Operate chair to obtain speed of approximately 2 mph 4. Attempt turn 5. Measure grip force applied to handle brake with force gage 6. Repeat 3 7. Attempt to stop wheelchair 8. Measure force with gage

Pinch Point Test This test is designed to verify the customer’s need of a minimal number of pinch points on the wheelchair during operation. The individual conducting the test will operate the wheelchair and evaluate potential pinch points. The probability, situation, and severity for each pinch point should be noted. The test can receive a conditional passing if the there are a moderate amount of pinch points, but the probabilities for each are relatively low. However, it will be considered a failure if there are high probability or high severity pinch points.

Foldability Test This test is designed to verify the customer’s need of foldability for wheelchair transport. The individual conducting the test will fold the seat back down to meet the seat, remove 2 wheels, 2 arm rests, 2 foot rests, and telescope the lever down. The remaining wheelchair frame and all removed components will be placed into the trunk of a small, common vehicle, a Ford Focus Sedan, and the trunk will be shut. Ergonomic issues will be taken note of. The test can receive a conditional passing if the wheelchair and its components fit into the back seat of the vehicle. However, it will be considered a failure if the wheelchair does not fit into the trunk or the backseat.

Weight Limit Test The purpose of this test is to determine that the wheelchair can be operated with added weight of up to 250 pounds (standard for the industry). This test will consist of two specs being tested. First the an operator(s) of approximately 250 pounds will operate the wheelchair over a ten minute period at varying speeds. This will assure that during use the chair can meet this requirement. Secondly, 250 pounds of weight (in plates) will be added to the chair and it will be set-up to set in the lab overnight. This aspect of the test will verify that no stress or strain is sustained by the chair at that weight over such a period of time. Process: 1. Subject sits in wheelchair 2. Grabs lever at “starting” position 3. Operate chair to obtain speed of approximately 2 mph 4. Operate chair for ten minutes 5. Investigate chair for stress/strain 6. Set-up chair with weights 7. Leave chair in lab overnight

Terrain Test This test is designed to verify the customer need of the wheelchair being able to adequately traverse common terrain. Common terrain includes surfaces that a user would typically encounter in a long-term care facility environment. Examples are plush carpet and hard wood floors indoors, and grass and blacktop outdoors. The test would be considered a success if the wheelchair can traverse the various surfaces successfully and without requiring an unsafe level of force. The test would be considered a failure if the wheelchair fails to traverse the more common indoor terrains, or requires an unsafe amount of force to travel across the indoor terrains.

Attendant Maneuverability Test This test is designed to verify the need of the wheelchair to be maneuverable by an attendant. The attendant will push and maneuver the wheelchair while an individual is sitting in the chair. The test shall include pushing the chair down a straight hallway, turning a 90 degree corner, and fitting through a standard sized doorway. The test would be considered an overall success if the attendant is able to maneuver through each scenario successfully. The test would be considered an overall failure if the attendant fails to maneuver through any of the scenarios.

Ramp Test This test is designed to verify that the wheelchair can meet the ADA standard of maintaining stationary on a 1:12 ramp grade. And individual of approximately 170lbs will sit on the wheelchair on a 1:12 ramp grade with the parking brakes engaged. This test will be done in idea conditions meaning, no ice or other obstructions on the ramp. A failure occurs if the wheelchair is unable to maintain stationary on a 1:12 ramp. This test will also be performed on a 1:6 ramp grade.

Range of Motion Test The purpose of this test is to determine that during lever propulsion, the arm angle does not exceed the anthropometric limits ( degrees). It will be important to analyze the arm angle of several subjects to accurately capture the usage population. If the range of motion at the elbow is not acceptable for repetitive application than hyper-extension or repetitive stress injury (RSI) can occur. Process: 1. Subject sits in wheelchair 2. Grabs lever at “starting” position 3. Measure arm angle record 4. Subject pushes lever to “fully extended” position 5. Measure arm angle 6. Record 7. Repeat several pulses in order to verify results

Comfort Test This test is designed to verify the need of comfort. The wheelchair will be tested by 3-4 members of the team. Each person will use the wheelchair continuously for 24 hours and maintain a record of comfort in terms of seating and using the lever to propel. A failure occurs if the test subjects do not believe that the wheelchair was comfortable for a minimum of 3 hours. The customer, a stroke patient, will also test the comfort of the chair, focusing more on the lever propulsion, only when accompanied by at least one member of the team Comments will be recorded.

Weight Test This test is designed to verify the weight of the entire wheelchair. The entire wheelchair consists of wheels, foot rests, arm rests, and entire frame along with the differential and disc brakes. The wheelchair will be placed on a large scale to measure and record the weight. If a large scale is unavailable, a bathroom scale will be used. The weight of the individual will be subtracted from the weight of the wheelchair and the individual, together. A failure occurs if the weight of the wheelchair exceeds 50 lbs.

Ease of Assembly/Disassembly Test This test is designed to determine the ease of assembly and disassembly of the wheelchair. 5 test subjects between the ages of will be chosen to perform an assembly and disassembly of the wheelchair, and to lift the wheelchair when disassembled. Assembly includes attaching 2 wheels, inserting 2 armrests, attaching 2 foot rests, and extending the lever. The subject will first be instructed on how to perform the tasks. The time spent to assemble and disassemble will be recorded in the table below. A failure occurs when the time it takes to assemble or disassemble the wheelchair is >4 minutes.

Reproducibility Test This test is designed to verify the need of the wheelchair to be reproducible at a reasonable cost. A reasonable cost is defined as approximately the cost of an average one- arm wheelchair that exists in the market as-of-today. Economies of scale will be taken into consideration when evaluating the total cost of materials for assembling the new one- arm wheelchair. The test would be considered a success if the total cost is less than a 50% increase of the average cost of the current one-arm wheelchairs. The test would be considered a failure if the total cost is greater than a 50% increase of the average cost of the current one-arm wheelchairs. The test can receive a conditional passing grade at the discretion of the tester (based on experience). Average Cost of Current One-Arm Wheelchair: $__________ Total Cost of Designed One-Arm Wheelchair:$__________ Percentage of Designed Wheelchair to Current Wheelchair:____%

Anthropometric Adjustability Test The purpose of this test is to assure that the chair can be operated comfortably by a 5th percentile male as well as a 95th percentile male. Based on the anthropometric tables a 5th percentile male has a seated elbow height of 7.6 inches from the seat; a 95th percentile male’s value is 11.6 inches. Several subjects will be selected to operate the lever and brake handles representing varying percentiles. Based on subject feedback/rating it will be determined if the handle positioning is acceptable. Process: 1. Subject sits in wheelchair 2. Grasp on handle where comfortable 3. Note positioning in regards to brake and elbow angle 4. Operate chair for ten minutes 5. User rate chair

Style Test This test is designed to verify the need of acceptable style for the wheelchair. The wheelchair will be shown in operation to various demographics (age range, gender) and opinions will be recorded. Each individual will give their opinion on whether they believe the wheelchair is stylistically acceptable or not, and why. The test would be considered a success if the majority of the individuals questioned believe the wheelchair has acceptable style. The test would be considered a failure if the majority of the individuals questioned believe the wheelchair does not have acceptable style.

Action Items Addressed

Next Steps -Finalize Bill of Materials (Suppliers, Costs, Lead Times) -Order materials w/ long lead time -Create assembly Plan