evaluation of titanium ultralight manual wheelchairs using ansi/resna standards.

by:AIRWOLF     2020-06-14
Choosing the right wheelchair requires serious consideration. TheU. S.
The Food and Drug Administration recommends the use of the National Standards Association of the United States (ANSI)
/North American Society of Rehabilitation Engineering and auxiliary technology (RESNA)
Test criteria [1]
Evaluate the performance and safety of the wheelchair and estimate the life expectancy of the wheelchair.
The results of the ANSI/RESNA standard test are sources of information about technical quality and performance and allow comparison of results across devices.
The content of the standard test covers many aspects that affect the use and selection of wheelchairs, such as size, static stability, braking effectiveness, strength and durability.
The dimensions, weight, and turning radius give consumers an idea that wheelchairs will be suitable for their home, working environment, and transportation.
The performance of the wheelchair in the static stability test reveals the estimated behavior of the wheelchair on the slope.
The results show how the adjustment of the shaft and other components affects the stability of the wheelchair.
It is difficult to determine the strength and durability of the wheelchair from the retail advertising and user manual.
Although Medicare prescriptions typically take 3 to 5 years to replace wheelchairs, previous studies have shown that life expectancy in some wheelchairs is significantly lower [2-7].
Premature wheelchair failures can hurt users and may require them to pay for a replacement, which can cost thousands of dollars.
According to Smith and others.
Wheelchair users expect wheelchairs to improve their quality of life and help them maintain or achieve the desired level of activity. 8].
Users want their wheelchair to be comfortable, easy to advance, safe and attractive [8].
In a survey of wheelchair users with muscle atrophy lateral cable hardening, the ideal feature of a manual wheelchair is a lightweight frame and a small turning radius [9].
Comfortable push and support, light weight and small size are very important functions, especially for active manual wheelchair users [10-11].
The lighter wheelchair has lower rolling resistance, thus reducing the force required to push the wheelchair.
So, in order to keep up-
Limb function of manual wheelchair users [12].
Developing a lighter and more functional wheelchair is the goal of many manual wheelchair designs.
Titanium wheelchairs are products launched to achieve this goal.
ANSI/RESNA standard tests provide specific test protocols for evaluating wheelchair performance and durability and serve as a common platform for data collection and comparison.
Reports using the ansi/RESNA standard evaluated aluminum ultra light wheelchairs and steel light wheelchairs.
Before the failure of the ultra-light wheelchair in the fatigue test, the duration is more than five times that of the light wheelchair [2-3].
However, there are more component failures in the ultra-light wheelchair, such as bolts or casters.
Stem glitches and screaming loose.
While fixable component failures do not damage the integrity of the frame, multiple component failures require frequent maintenance and may put users in a dangerous environment.
Many ultra light wheelchairs have titanium frames and/or components.
Due to the higher strength of titaniumto-
The weight is more than aluminum, and if the design is correct, it can maintain the strength of the wheelchair frame while reducing the weight.
The traditional view of our wheelchair clinic is that people using titanium chairs benefit from their highly durable and lightweight performance, although the standard test results for titanium wheelchairs are not reported in the literature.
Similar to previous work in this field, our goal in this study is to test a range of commercial titanium rigidity-
Frame wheelchair using ANSI/RESNA test program.
Standard test for determining braking effectiveness according to the International Organization for standardized (ISO)
This study was also included in [13]
Because the current ANSI/RESNA standard does not include the brake effectiveness test for manual wheelchairs.
We assume that these titanium wheelchairs meet ANSI/RESNA standards and are more durable than previously tested aluminum ultra-light and lightweight wheelchairs.
Research Method of 12 titanium rigid wheelchair
Four models of frame wheelchairs representing three manufacturers were tested using the ANSI/RESNA wheelchair standard: Invacare tip (Invacare; Elyria, Ohio)
, TheInvacare A4, Ti in a hurry (Sunrise Medical;
Langmont, Colorado)
And TiLite ZRA (TiLite;
Kenneswick, Washington)(Figure 1).
They are the most popular ultra-light rigid titanium-
Frame wheelchair specified by the University of Pittsburgh Medical Center auxiliary technology center.
They ordered the same seat size specifications and standard parts.
Due to the cost and time of testing a wheelchair, we only tested three wheelchairs per model.
Standard test procedure we completed the entire battery of the ANSI/RESNA manual wheelchair standard test and evaluated the braking effectiveness using the ISO standard test.
This paper focuses on the test results of static stability;
Braking efficiency;
As well as static, impact and fatigue strength tests.
The dummies used in this study were built according to the requirements of the ansi/RESNA standard. [
Figure 1 slightly]
The wheelchair was tested for static stability in the most stable and unstable configuration (
Forward and backward directions)
In the static stability test ([section]
1 of the ANSI/RESNA wheelchair standards).
The test wheelchair was loaded with a dummy of 100.
The wheelchair is secured on the platform using straps that do not interfere with tilt movement.
Anengineer slowly increased the angle of the platform and recorded the angle of the front casters lifted from the platform, enough for a piece of paper to be passed between the casters and the platform.
In the back stability test, the rear wheels are locked by the parking brake, or the wheels are fixed with straps, limiting the rolling movement of the wheels relative to the frame.
In other parts of the static stability test, blocks or brackets that do not prevent wheel rolling movement are used to prevent the wheelchair from rolling downhill.
We put the wheelchair in its most unstable position by moving back.
The front shaft is reclined forward, the backrest is tilted back, and the height of the front seat is increased by adjusting the bracket position.
We position the wheelchair in the most unstable position because the range of the wheelchair is not shown or restricted
The axle position is indicated on the wheelchair or user manual.
Most wheelchairs, in their most unstable environment, lean backwards on the level of the loading dummy.
Although these extremely unstable positions in the backward direction are not really wheelchair settings, we continue to carry out and record the tests because the purpose of the standardized tests is to reveal the actual properties of the wheelchair.
To address this limitation, we put the downhill facing wheelchair on the platform and secure it with a strap to prevent it from tilting completely (Figure 2(a)).
Then the slope is increased and the angle of the front caster contact platform is recorded (Figure 2(b)).
This reading is negative.
Braking efficiency in brake performance test ([section]
3 of the isowheelair standard)
, We put the wheelchairs in the same environment as when they came out of the box (
The axle is at the back)
, Load them with 100 kg dummy and engage the rear brake.
The test is performed on the same platform as the static stability test.
While increasing the platform slope, we recorded the angle at which the wheelchair began to descend.
The wheelchair wastes time in the forward and backward directions.
Due to the obstacle slope that meets the requirements of the US Disability Act (ADA)is 7[degrees](1:8)
The biggest increase is 75mm (3 in. )
For existing buildings and facilities, we expect the wheelchair to be able to stay still on Highway 7degrees]slope.
Test of static, impact and fatigue strength (
Durability Test)
Test of static, impact and fatigue strength ([section]
Meet ansi/RESNA wheelchair standards)
The strength of the wheelchair structure is assessed by applying different types of loads to specific components.
Apnoatic ram is used to apply static force to footrest, handrails and tipping rods (if present)
According to the standard.
Use a pendulum to exert an impact on several parts of a wheelchair (
Footrest, casters, pushlin)
Easily affect the object.
Any permanent deformation or component failure is considered a fault as indicated in the standard.
Fatigue strength through double-drum and curb-droptests (
(DDT and DDT, respectively).
During the test, each wheelchair was loaded with a dummy of 100 kg.
In Deloitte, the position of the drive wheel is set at the mid-axis position according to the standard requirements.
Because the titanium wheelchair is unstable in this position, we place the rear bridge horizontally at the end and vertically in the middle position (
How did they arrive from the supplier).
Other wheelchair settings are set according to the requirements in the standard.
The length of the legs of the dummy is adjusted to fit the dimensions of the wheelchair and the feet are fixed on the foot pedal.
The torso and legs of the dummy are fixed to the wheelchair, although the hips
Saved the joint campaign through aspring
Wind door system allowing physiological-loading
Like the action when testing.
According to the standard, the dummy is placed centrally in the seat.
Under normal circumstances, the weight of the legs is 32 percent of the weight [14].
Individuals 6 months after spinal cordinjury may lose the lower half of 15 to 46%
Muscle area of limbs]15].
We keep our weight carefully.
Loading the front casters within 20-25 percentage of the total weight of the dummy and wheelchair to approximate the impact of occupant weight and wheelchair weight, and prevent the caster from overloading the position of the dummy in the front or rear direction by adjusting. The 12 mm-
The high slats on the drum simulate sidewalk cracks, door thresholds, potholes and other small obstacles on the rolling surface.
Two clips attached to the back-
The half shaft maintains the position and balance of the wheelchair in the wheelchair
Drum machine but allows vertical movement without obvious lateral drift (Figure 3).
The Therear drum runs at a speed of 1 m/s, and the front drum turns 7 percentage points faster to change the frequency of the front and rear wheels encountering slats.
Wheelchairs that complete 200,000 cycles on the test machine are considered to have passed DDT. [
Figure 2:
Only wheelchairs through DDT continue to enter DDT.
In CDT, the wheelchair is repeatedly free to drop from a height of 5 m high to a concrete floor to simulate a drop along a small curb.
Awheelchair passed the wheelchair standard test, and when it survived 200,000 cycles in DDT and 6,666 cycles in DDT, there was no harmful damage [1].
The strength of the fatigue test simulates daily use for 3 to 5 years [16].
We repeated the fatigue test until there was a permanent damage to each wheelchair to determine the exact life span.
To compare the fatigue life, we use the following formula to calculate the number of equivalent cycles (ECs)[2,6-7]
However, the breaking line through the hole means that the hole reduces the structural strength.
The figure of the translucent pattern in Figure 14 shows more clearly the proximity of the holes on the frame.
The pedals of two Invacare A4 wheelchairs slide repeatedly during Deloitte.
Although the only set of screws is caught in the avikang A4 and the top Endwheelchairs footrest tube (Figure16(c))
, A4 has a large difference in the diameter between the tubeof of the footrest and the outer sheet of the main frame (Table 6).
The strength of a fixing screw is not enough to compensate for the uneven tube diameter and the vertical vibration of the dummy leg during Deloitte, so the footrest slides down. In real-
In the world settings, afootrest keeps sliding down, bothering users because of the vertical vibration caused by riding on uneven terrain or cloning.
Although this installation mechanism of the footrest does not affect the integrity of the main frame, the accidental relocation of the footrest may be inconvenient and may cause damage. [
Figure 11 omitted]
The Quickie Ti and TiLite ZRA wheelchairs have the same type of functionality in the first or second screw holes near the frame cantilever turn.
These screw holes are used to install the sling on the frame (Figure 17).
Both models are cantilever frames (Figure 18(a)).
The anti-Rod frame does not have the same lower longitudinal tube as the box frame.
Impact force (Figure 18(a)(i))
Generate bending torque (Figure 18(a)(ii))
Bend the front vertical part of the frame.
Bending torque compresses the lower part of the tube (Figure 18 (a)(iii))
And extend the upper part of the tube (Figure 18(a)(iv)).
The first and second screw holes are just behind the bend of the frame and act as the point of stress concentration.
Therefore, the fracture inevitably occurs in this position.
Box box design (Figure 18(b))
, The lower longitudinal tube helps to distribute the force passed to the casters (Figure 18(b)(iii)).
This reduces the bending torque on the frame (Figure 18 (b)(ii)).
Invacare A4 also has screw holes near the corners of the front frame, but lower stress helps to protect the chair from failure in these stress concentration positions.
In addition to using screws, there are other ways to fix the seat sling on the frame.
For example, the InvacareTop end Terminator daily rigid wheelchair uses the Velcro strap to connect the seat sling [23]
This may have improved prematurefaults. [
Figure 12:
When there is a crack, the wheelchair material and design titanium alloy have a higher ability to resist brittle breakage than aluminum alloy [22].
Although titanium has ideal mechanical properties, titanium is 1.
6 times the weight of aluminum.
The balance between the total weight of the product and the strength of the structure needs to be carefully considered. The rigid-
The frame design and standard use of the 80mm casters are also key issues affecting the stability and durability of this set of wheelchairs.
Manufacturers and designers need to evaluate based on our results
The frame titanium wheelchair design is more detailed to understand the impact of material selection and mechanical design on the strength, durability and function of the wheelchair.
If the future direction is classified with a similar rigid wheelchair
As with the frame design in this article, the wheelchair standard test can be considered as a modification to the test methods and standard values of these wheelchair models. [
Figure 13:[
Figure 14 omitted][
Figure 15 omitted][
Figure 16 omitted]
First, sample size is a limitation of this study.
We will have to test 12 to 60 wheelchairs per model to get the statistical power of 0.
8. According to the test results of this study.
It is unrealistic to spend time and money to test the number of wheelchairs required.
Second, the test dummy cannot accurately simulate the real wheelchair user.
A real wheelchair user can dynamically adjust his or her posture to avoid situations that could endanger him --
Or herself or her wheelchair.
For example, during the fatigue test, repeated shocks of the dummy torso may not occur in the real environment
The world of this group of wheelchairs, but some users hang their backpacks on the back, which also puts bending pressure on the back.
The ANSI/RESNA standard test was originally designed to test the K0001 wheelchair 10 years ago, so the requirements for today\'s technology and manufacturing quality should not be so harsh.
In addition, in this study, the weight of the test dummy was less than the maximum weight of the wheelchair.
Although testing dummies does not completely mimic real wheelchair users, the general physical properties of dummies are actually less stressful than the manufacturer\'s claimed maximum weight capacity.
Third, we can only derive general results from standard tests, because this information is not thorough enough to distinguish between the specific causes or mechanisms of important failures in fatigue testing.
Therefore, future research is needed to solve these problems. [
Figure 17 slightly][
Figure 18 slightly]
Conclusion This group of rigidity
Frame titanium wheelchair is widely used.
Their height adjustable rear
When pushing the wheel chair, the axle, super light weight and compact size help reduce the user\'s physical pressure and increase ease of use.
This study reveals important design issues that need to be addressed.
Our results should remind manufacturers and designers that changes in the design of each welding point, screw hole and structure and frame have an impact on the strength and durability of the wheelchair.
Our results suggest that manufacturers may need to conduct more careful analysis before new products are commercialized.
Abbreviation: ADA = USA disability act, ANSI = National Standards Association of America, CDT = curbdrop test, DDT = double-
Drum testing, EC = equivalent circulation, ISO = International Organization for standardized, RESNA = Association of Rehabilitation Engineering and Assistive Technologies in North America.
This material is based on the work supported by the Department of Veterans Affairs Rehabilitation Research and Development Service (grantB3142C)
National Science Foundation-
Comprehensive Graduate Education and Research Training Program (
Grant DGE 0333420).
The author claims that there is no competitive interest.
Published in December 7, 2007.
Amendments were accepted in June 23, 2008. REFERENCES [1. ]
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Rosemarie Cooper, Ministry of mail and television, ATP,(1-2)
Samuel Connor of BS1)(1)
Human Engineering Research Laboratory, Department of Veterans (VA)
Rehabilitation Research and development services for healthcare systems, Pittsburgh, PA;
Department (2)
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Research Laboratory of Human Engineering
7180 Dr. Highland, Pittsburgh, PA 15206; 412-954-5287; fax:412-954-5340.
Email: rcooper @ pittedu DOI:10. 1682/JRRD. 2007. 12.
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