- Email: [email protected]
CAM Application
Copyright © IFAC Control Science and Technology (8th Triennial World Congress) Kyoto. Japan. 1981
WHEELCHAIR ANALYSIS-A CAD/CAM APPLICATION V. A. Rogers* and R. E. Fulton** -Department of Mechanical Engineering, Drexel University, Philadelphia, Pennsylvania, USA --[PAD Project, NASA-Langley Research Center, Hampton, Virginia , USA
Abstract. Computers have not been effectively utilized in rehabilitation engineering for the design of artificial limbs, wheelchairs or other supporting devices. Advances in computer aided design and manufacturing (CAD/CAM) technology offer the opportunity for significant improvements in health care delivery. Three software programs are evaluated for health care applications. These programs are part of the software released under a NASA sponsored joint industry/government effort denoted Integrated Programs for Aerospace-Vehicle Design (IPAD) Project for the advancement of CAD/CAM technology. Included are: three dimensional graphics, structural analysis and data base management and manipulation. This paper describes a spin off application in rehabilitation engineering. Keywords. Computer aided design; three dimensional graphics; structural analysis; data base management; wheelchairs. INTRODUCTION The engineering industry relies more and more heavily on computerized automation and automatic controls to solve complex technological problems and to increase the productivity of its workers. We believe significant improvements are possible through effective application of current and future computer aided design and manufacturing (CAD/CAM) technology. In the United States the aerospace industry has assumed a leadership role in encouraging the use of the computer to enhance the industrial rate of performance and quality of life of the workers. The National Aeronautics and Space Administration (NASA) has actively supported this effort through a joint NASA/ industry mu1timi11ion dollar project called Integrated Programs for Aerospace-Vehicle Design (IPAD) (Fu1ton, 1980). The IPAD project has been underway for several years and is making significant progress in advancing integrated CAD/CAM technology. The project goal is to raise aerospace industry productivity through application of computers to integrate company wide management of engineering data. Work under the IPAD project is being implemented principally through a NASA contract to the Boeing Commercial Airp1ane Company under the guidance of an Industry Technical Advisory Board (ITAB) composed of members of the aerospace and computer industries. A mature operational IPAD capability will consist of system software, including executive, data management, and geometry/
graphics software, together with disciplinary technical programs installed in IPAD to implement its integrated design features and project data. The IPAD project is developing prototype system software and will use available technical programs and data for demonstration and evaluations. CAD/CAM AND WHEELCHAIR DESIGN The CAD/CAM technology can be readily exploited in wheelchair design and manufacture. Wheelchairs, probably the most commonly used handicapped human aide, provide personna1 freedom and increase the physical function of hundreds of thousands of men, women, and children and generally improve the quality of their lives. Yet wheelchairs have not changed appreciably during the last forty years eventhough great technological advances have occured throughout the world in the interim. Consumers complain of frequent breakdowns high maintenance costs, and interminable delays in acquiring replacement parts. Wheelchairs are often purchased haphazardly and the user is faced with a device which is too large or too small, painful, dangerous, difficult to propel, unnecessarily expensive and even harmful physiologically. The time has come for a reassessment of wheelchair design and to apply the technology of the space age to rehabilitation of the
]997
J998
v.
A. Rogers and R. E. Fulton
handicapped.
HUMAN BODY SIMULATION
Wheelchair design is a complex endeavor. The rehabilitation engineer must consider specifications for materials, construction, overall dimensions, folding mechanisms, foot rests and supports, wheels, tires, brakes, clothing guards, accessories, joint construction, finish and quality control testing. In addition to these items, and perhaps more importantly, one must consider center of mass adjustments or stability, aerodynamic drag, propulsion methods, curb climbing capabilities, maintainability and aesthetics. Wheelchairs may be designed for the indoor, outdoor or recreational environment.
Since the wheelchair user is an integral part of the total structure and contributes substantially to the stability or instability of the assembly, it is essential that a model of the human body be developed for design testing of wheelchairs. Standard wheelchairs are manufactured in five sizes: small child, large child, junior, adult and oversize. Are these sizes adequate? Most users think not. Inherent in the sizing specification is the human body configuration modeling requirement. A prototype method for achieving this goal has been developed and is described below.
Computer aided design (CAD) has been used for many years in the development of aerospace vehicles where dynamic stability, light weight and minimal propelling power are important. It is surprising that these same design criteria must be met in the optimization of wheelchair performance and, therefore, automated aerospace analytical techniques are directly applicable to the wheelchair problem. Aerospace CAD technology provides an in hand, custom made, software package for analysis of wheelchairs. Utilization of the automated three dimensional geometric simulator (AD2000) and the structural analysis software package (SPAR) insures that the wheelchair design can progress beyond the "cut and try" methods of the past. Three CAD/CAM software packages are being evaluated in this study for health care applications - AD2000, SPAR, and RIM. These programs, from the NASA IPAD project, have found broad application in diverse fields. AD2000, Automated Design and Drafting for 2000 AD, is a CAD/CAM software system which provides basic three dimensional geometry, mechanical drafting, geometric analysis, and numerical control operations for manufacturing. SPAR is a structural analysis system employing finite element methods for determining the static and dynamic response of structures. RIM, Relational Information Management, is data base management software which contains relational algebra manipulating capability. Once a design concept has been identified, it can be easily simulated and evaluated using the CAD technology. The initial design concept might be an existing wheelchair model, a modification of an existing model or a completely new and innovative idea. In any case the candidate wheelchair design can be geometrically defined using the graphics three dimensional simulator, AD2000. Once this is accomplished the wheelchair can be loaded with a human body model and stability relationships determined. Design recommendations can follow immediately from this simulation.
The current technique for obtaining nondestructive, inertial measurements of a three dimensional, non-homogeneous, irregular, semi-solid, such as a human body, is complex. In the past, human body models have been developed by assuming simple geometric shapes for components of the human body such as the ellipsoidal segments in the work of McConville (1976) and Bartz (1973). Cadavers have been used extensively to determine volume, mass, center of mass, and moments of inertia of body segments. Jensen (1976) refined the model by employing elliptical slices of uniform density for each segment. Watkins (1976) later proposed a method for predicting component mass properties based on experimental data for whole body mass properties. The CAD/ CAM software employed here offers the opportunity to integrate these methods with the biostereometric (two dimensional photographic) work of Herron and Walker (1973) to produce a three dimensional human body model which is not limited to uniform densities or fixed geometric shapes. With the method described in this paper it is possible to calculate the necessary stability relationships for the chair and its occupant as a combined entity. A method has been devised for finding the center of gravity or moment of inertia of the whole body or parts thereof on an individual basis. Body silhouettes are input to the software system through a Tektronics pen tablet digitizer. A three dimensional model is produced which is a summation of mass cells located in a global coordinate system within the body silhou-
Wheelchair Analysis - A CAD/CAM Application
ette. The center of gravity for each body part is found according to the following equations:
automatic numerical control of the manufacturing process. CONCLUDING REMARKS
X.=I:X.W., J __ 1_1
I: W i
Y.= I:Y.W. , J __ 1_1
I: W i
where X. is the coordinate of the centroid of the I th cell and W. is its weight. P(X., Y., Z.) is the p6sition of the center df gtavity of the j th body part. The moment of inertia is found similarly using the parallel axis theorem. Body part boundaries may be chosen arbitrarily and mass density may be changed on an individual cell basis. The number of mass cells is limited only by storage space. The modeling is initiated by producing a three dimensional lattice of cells of any desired density as shown in Fig. 1. The image to be produced is projected on the X-Y plane and the Y-Z plane of the lattice and portions of the lattice or cells outside the projected image are deleted, thus producing the finished model. One of the key features is that the methodology and geometric modeling can be carried out by medical technicians unskilled in CAD/CAM technology. ANALYSIS OF THE WHEELCHAIR UNDER STATIC AND DYNAMIC LOAD Structural analysis of the wheelchair is conducted employing applied loads calculated from the human body simulation described in the previous section. After geometric definition the input data for the structural analysis program, SPAR, is transfered from AD2000 to SPAR. SPAR calculates the static reactions, static deflections, stresses and dynamic response of the chair to vibrations and applied forces. Constraints and applied forces may be simulated and the weight of individual elements of the chair optimized. The graphical analysis of a loaded wheelchair is shown in Fig. 2. The wheels have been removed from the chair and the axis fixed. A static vertical load of 150 pounds is applied to the lateral sides of the seat of the chair. The unloaded chair is indicated by solid lines and the deformed chair under load is shown by dotted lines. The deflections, joint locations, applied forces and stresses are printed on a disc file. Following structural analysis the resulting data is stored by a data management software package called RIM. RIM is a relational data base management system which enables the user to compare results of one test with another or one chair with another in an interactive mode. If evaluation and testing so indicate, the wheelchair design may be modified and the analytical procedure repeated. Once a design has been accepted for testing and manufacture, AD2000 is then employed in preparing magnetic tapes for
The wheelchair simulator described here can be adapted to the individual patient and ultimately will be utilized by an unskilled technician working with a minicomputer of the DEC VAX 11/780 class. The CAD/CAM concepts that are utilized in this study are not new and are frequently used in aerospace applications. Their spin off use in human rehabilitation, however, has not been exploited and is believed to be of significant value. The study is continuing and this paper indicates the direction of future work in applying CAD/CAM technology to rehabilitation engineering. Applications discussed and illustrated are applicable to both wheelchairs and artificial limbs and future study will cover apparatus modeling, analysis and fabrication using CAD/CAM technology developed for use in other fields. This particular research is a direct spin off from the ongoing IPAD project. REFERENCES Bartz, J. A. and C. R. Gianotti (1973). Computer program to generate dimensional and inertial properties of the human body. American Society of Mechanical Engineers, Winter Annual Meeting, Detroit, Michigan, 9 p. Fulton, R. E. (1980). National meeting to review IPAD status and goals. Astronautics and Aeronautics, 49-52. Herron, R. L., Cuzzi, J. R. and J. Hugg (1976). Mass distribution of the human body using biostereometrics. Texas Institute for Rehabilitation and Research, Houston, Texas, Final Report, 203 p. Jensen, R. K. (1976). International Series on Biomechanics, Volume lB, Biomechanics V-B, Proceedings of the Fifth International Congress of Biomechanics, Jyvaskyla, Finland, p. 380. McConville, J. T. and C. E. Clauser (1976). Anthropometric assessment of the mass distribution characteristics of the living human body. International Ergonometrics Association, 6th Congress and Human Factors Society, 379-383. Walker, L. B., Harris, E. H. and D. R. Pontius (1973). Mass volume cent er of mass and mass moment of inertia determined for head and neck of
J999
2000
V. A. Rogers and R. E. Fulton
Human Body. TLSP: Final Report Tulane University, New Orleans, LA, CNT #N00014-69-A-0248-000, 35 p. Watkins, R. D. and W. T. Fowler (1976). Dynamic determination of the mass properties of an astronaut. AlAA 14th Aerospace Sciences Meeting, Washington, D. C.
Whittle, M. W., Herron, R. L. and J. R. Cuzzi (1976). Biostereometric analysis of body form. Aviation, Space, and Environmental Medicine, 47, 410-412. Whittle, M. W., Herron, R. L., Cuzzi, J. R. and C. W. Keys (1976). The effects of prolonged space flight on the regional distribution of fluid, muscle and fat; biostereometric results from Skylab. AGARD Conference Proceeding No. 203, 5 p .
.............•.•.. •• ..
..••
.. ••
...... ..... •••••
••••• •••••• •••••• •••••• •••••• ••••••
....... ....... •••••••
••••••• .• ....... ••••••• .. ......
.• ..... ••••• • ...... ••••• . • ••••• .• ...... . •••••• • •••••• • •••••• • ••••••
...... ... ..... ... .. • ••••••• ,
•••••••. .. • .......
...... .
•.. ••••••• •••••••• •••••• •• •••••• • • •••••••
........
••••••• ...... c•
.....
••••••• ••••••• •••••• •• • •••••• ••••••••••••••••••••• .........•...• ~~
Figure 1.
A typical simplified wheelchair simulation.
Wheelchair Analysis -
A CAD/CAM Application
2001
----, \ \
, \ \
\
, \ \ \ \
---------
---------~
" '1 11
I,
"
i!
Figure 2.
A typical wheelchair analysis showing deformation. Solid lines indicate the structure prior to loading. Dotted lines show deflections created by the application of loads. Deflections are exaggerated for effect.
Discussion to Paper 69.3 J. Hatvany (Hungary): My impression is that the tools you are using are a case of overkill with respect to the magnitude of the wheelchair problem - especially in comparison to the results in actual wheelchair design that you have presented. V.A. Rogers (USA): I believe that to be a comment rather than question so there is nothing to add. Y. Nakamura (Japan): Has the SPAR program any relation to NASTRAN? V.A. Rogers (USA) : SPAR was developed by the same people who developed NASTRAN. SPAR is specifically designed for the minicomputer and I believe it has most of the capabilities that NASTRAN has, although I am not familiar with NASTRAN other than to know that it is very popular. K. Tani (Japan) : How many percent in weight do you deduce in your wheelchair design? V.A. Rogers (USA): We are in the early stages of the project and have not yet performed an optimization based on weight. G.E. Ennis (USA): To exactly what mini-
computer is A2000 implemented and to what extent are AD2000 and RIM integrated? V.A. Rogers (USA): Joint locations from AD2000 are transferred to RIM as are element properties . .. From RIM a command file is generated and sent to SPAR. The output from SPAR is then sent back t o RIM for analysis. The mini-computers used are the PRIME 400 and VAX-ll. H. Yoshikawa (Japan) : Your contribution is very important from the viewpoint that you showed industrial techniques can be applied to social problems. I am especially interested in formalization of demands in such cases as rehabilitation. The description of demands for the wheelchair might not be so different from the normal industrial products. How did you formalize the demand for it in your project? V.A. Rogers (USA): Defining the live loads, the wheelchair experiences and environmental specifications for its design are the most difficult portions of the wheelchair project. This is why the human body simulator is necessary. It may be that we will have to employ active elements in the final model.
WHEELCHAIR ANALYSIS-A CAD/CAM APPLICATION V. A. Rogers* and R. E. Fulton** -Department of Mechanical Engineering, Drexel University, Philadelphia, Pennsylvania, USA --[PAD Project, NASA-Langley Research Center, Hampton, Virginia , USA
Abstract. Computers have not been effectively utilized in rehabilitation engineering for the design of artificial limbs, wheelchairs or other supporting devices. Advances in computer aided design and manufacturing (CAD/CAM) technology offer the opportunity for significant improvements in health care delivery. Three software programs are evaluated for health care applications. These programs are part of the software released under a NASA sponsored joint industry/government effort denoted Integrated Programs for Aerospace-Vehicle Design (IPAD) Project for the advancement of CAD/CAM technology. Included are: three dimensional graphics, structural analysis and data base management and manipulation. This paper describes a spin off application in rehabilitation engineering. Keywords. Computer aided design; three dimensional graphics; structural analysis; data base management; wheelchairs. INTRODUCTION The engineering industry relies more and more heavily on computerized automation and automatic controls to solve complex technological problems and to increase the productivity of its workers. We believe significant improvements are possible through effective application of current and future computer aided design and manufacturing (CAD/CAM) technology. In the United States the aerospace industry has assumed a leadership role in encouraging the use of the computer to enhance the industrial rate of performance and quality of life of the workers. The National Aeronautics and Space Administration (NASA) has actively supported this effort through a joint NASA/ industry mu1timi11ion dollar project called Integrated Programs for Aerospace-Vehicle Design (IPAD) (Fu1ton, 1980). The IPAD project has been underway for several years and is making significant progress in advancing integrated CAD/CAM technology. The project goal is to raise aerospace industry productivity through application of computers to integrate company wide management of engineering data. Work under the IPAD project is being implemented principally through a NASA contract to the Boeing Commercial Airp1ane Company under the guidance of an Industry Technical Advisory Board (ITAB) composed of members of the aerospace and computer industries. A mature operational IPAD capability will consist of system software, including executive, data management, and geometry/
graphics software, together with disciplinary technical programs installed in IPAD to implement its integrated design features and project data. The IPAD project is developing prototype system software and will use available technical programs and data for demonstration and evaluations. CAD/CAM AND WHEELCHAIR DESIGN The CAD/CAM technology can be readily exploited in wheelchair design and manufacture. Wheelchairs, probably the most commonly used handicapped human aide, provide personna1 freedom and increase the physical function of hundreds of thousands of men, women, and children and generally improve the quality of their lives. Yet wheelchairs have not changed appreciably during the last forty years eventhough great technological advances have occured throughout the world in the interim. Consumers complain of frequent breakdowns high maintenance costs, and interminable delays in acquiring replacement parts. Wheelchairs are often purchased haphazardly and the user is faced with a device which is too large or too small, painful, dangerous, difficult to propel, unnecessarily expensive and even harmful physiologically. The time has come for a reassessment of wheelchair design and to apply the technology of the space age to rehabilitation of the
]997
J998
v.
A. Rogers and R. E. Fulton
handicapped.
HUMAN BODY SIMULATION
Wheelchair design is a complex endeavor. The rehabilitation engineer must consider specifications for materials, construction, overall dimensions, folding mechanisms, foot rests and supports, wheels, tires, brakes, clothing guards, accessories, joint construction, finish and quality control testing. In addition to these items, and perhaps more importantly, one must consider center of mass adjustments or stability, aerodynamic drag, propulsion methods, curb climbing capabilities, maintainability and aesthetics. Wheelchairs may be designed for the indoor, outdoor or recreational environment.
Since the wheelchair user is an integral part of the total structure and contributes substantially to the stability or instability of the assembly, it is essential that a model of the human body be developed for design testing of wheelchairs. Standard wheelchairs are manufactured in five sizes: small child, large child, junior, adult and oversize. Are these sizes adequate? Most users think not. Inherent in the sizing specification is the human body configuration modeling requirement. A prototype method for achieving this goal has been developed and is described below.
Computer aided design (CAD) has been used for many years in the development of aerospace vehicles where dynamic stability, light weight and minimal propelling power are important. It is surprising that these same design criteria must be met in the optimization of wheelchair performance and, therefore, automated aerospace analytical techniques are directly applicable to the wheelchair problem. Aerospace CAD technology provides an in hand, custom made, software package for analysis of wheelchairs. Utilization of the automated three dimensional geometric simulator (AD2000) and the structural analysis software package (SPAR) insures that the wheelchair design can progress beyond the "cut and try" methods of the past. Three CAD/CAM software packages are being evaluated in this study for health care applications - AD2000, SPAR, and RIM. These programs, from the NASA IPAD project, have found broad application in diverse fields. AD2000, Automated Design and Drafting for 2000 AD, is a CAD/CAM software system which provides basic three dimensional geometry, mechanical drafting, geometric analysis, and numerical control operations for manufacturing. SPAR is a structural analysis system employing finite element methods for determining the static and dynamic response of structures. RIM, Relational Information Management, is data base management software which contains relational algebra manipulating capability. Once a design concept has been identified, it can be easily simulated and evaluated using the CAD technology. The initial design concept might be an existing wheelchair model, a modification of an existing model or a completely new and innovative idea. In any case the candidate wheelchair design can be geometrically defined using the graphics three dimensional simulator, AD2000. Once this is accomplished the wheelchair can be loaded with a human body model and stability relationships determined. Design recommendations can follow immediately from this simulation.
The current technique for obtaining nondestructive, inertial measurements of a three dimensional, non-homogeneous, irregular, semi-solid, such as a human body, is complex. In the past, human body models have been developed by assuming simple geometric shapes for components of the human body such as the ellipsoidal segments in the work of McConville (1976) and Bartz (1973). Cadavers have been used extensively to determine volume, mass, center of mass, and moments of inertia of body segments. Jensen (1976) refined the model by employing elliptical slices of uniform density for each segment. Watkins (1976) later proposed a method for predicting component mass properties based on experimental data for whole body mass properties. The CAD/ CAM software employed here offers the opportunity to integrate these methods with the biostereometric (two dimensional photographic) work of Herron and Walker (1973) to produce a three dimensional human body model which is not limited to uniform densities or fixed geometric shapes. With the method described in this paper it is possible to calculate the necessary stability relationships for the chair and its occupant as a combined entity. A method has been devised for finding the center of gravity or moment of inertia of the whole body or parts thereof on an individual basis. Body silhouettes are input to the software system through a Tektronics pen tablet digitizer. A three dimensional model is produced which is a summation of mass cells located in a global coordinate system within the body silhou-
Wheelchair Analysis - A CAD/CAM Application
ette. The center of gravity for each body part is found according to the following equations:
automatic numerical control of the manufacturing process. CONCLUDING REMARKS
X.=I:X.W., J __ 1_1
I: W i
Y.= I:Y.W. , J __ 1_1
I: W i
where X. is the coordinate of the centroid of the I th cell and W. is its weight. P(X., Y., Z.) is the p6sition of the center df gtavity of the j th body part. The moment of inertia is found similarly using the parallel axis theorem. Body part boundaries may be chosen arbitrarily and mass density may be changed on an individual cell basis. The number of mass cells is limited only by storage space. The modeling is initiated by producing a three dimensional lattice of cells of any desired density as shown in Fig. 1. The image to be produced is projected on the X-Y plane and the Y-Z plane of the lattice and portions of the lattice or cells outside the projected image are deleted, thus producing the finished model. One of the key features is that the methodology and geometric modeling can be carried out by medical technicians unskilled in CAD/CAM technology. ANALYSIS OF THE WHEELCHAIR UNDER STATIC AND DYNAMIC LOAD Structural analysis of the wheelchair is conducted employing applied loads calculated from the human body simulation described in the previous section. After geometric definition the input data for the structural analysis program, SPAR, is transfered from AD2000 to SPAR. SPAR calculates the static reactions, static deflections, stresses and dynamic response of the chair to vibrations and applied forces. Constraints and applied forces may be simulated and the weight of individual elements of the chair optimized. The graphical analysis of a loaded wheelchair is shown in Fig. 2. The wheels have been removed from the chair and the axis fixed. A static vertical load of 150 pounds is applied to the lateral sides of the seat of the chair. The unloaded chair is indicated by solid lines and the deformed chair under load is shown by dotted lines. The deflections, joint locations, applied forces and stresses are printed on a disc file. Following structural analysis the resulting data is stored by a data management software package called RIM. RIM is a relational data base management system which enables the user to compare results of one test with another or one chair with another in an interactive mode. If evaluation and testing so indicate, the wheelchair design may be modified and the analytical procedure repeated. Once a design has been accepted for testing and manufacture, AD2000 is then employed in preparing magnetic tapes for
The wheelchair simulator described here can be adapted to the individual patient and ultimately will be utilized by an unskilled technician working with a minicomputer of the DEC VAX 11/780 class. The CAD/CAM concepts that are utilized in this study are not new and are frequently used in aerospace applications. Their spin off use in human rehabilitation, however, has not been exploited and is believed to be of significant value. The study is continuing and this paper indicates the direction of future work in applying CAD/CAM technology to rehabilitation engineering. Applications discussed and illustrated are applicable to both wheelchairs and artificial limbs and future study will cover apparatus modeling, analysis and fabrication using CAD/CAM technology developed for use in other fields. This particular research is a direct spin off from the ongoing IPAD project. REFERENCES Bartz, J. A. and C. R. Gianotti (1973). Computer program to generate dimensional and inertial properties of the human body. American Society of Mechanical Engineers, Winter Annual Meeting, Detroit, Michigan, 9 p. Fulton, R. E. (1980). National meeting to review IPAD status and goals. Astronautics and Aeronautics, 49-52. Herron, R. L., Cuzzi, J. R. and J. Hugg (1976). Mass distribution of the human body using biostereometrics. Texas Institute for Rehabilitation and Research, Houston, Texas, Final Report, 203 p. Jensen, R. K. (1976). International Series on Biomechanics, Volume lB, Biomechanics V-B, Proceedings of the Fifth International Congress of Biomechanics, Jyvaskyla, Finland, p. 380. McConville, J. T. and C. E. Clauser (1976). Anthropometric assessment of the mass distribution characteristics of the living human body. International Ergonometrics Association, 6th Congress and Human Factors Society, 379-383. Walker, L. B., Harris, E. H. and D. R. Pontius (1973). Mass volume cent er of mass and mass moment of inertia determined for head and neck of
J999
2000
V. A. Rogers and R. E. Fulton
Human Body. TLSP: Final Report Tulane University, New Orleans, LA, CNT #N00014-69-A-0248-000, 35 p. Watkins, R. D. and W. T. Fowler (1976). Dynamic determination of the mass properties of an astronaut. AlAA 14th Aerospace Sciences Meeting, Washington, D. C.
Whittle, M. W., Herron, R. L. and J. R. Cuzzi (1976). Biostereometric analysis of body form. Aviation, Space, and Environmental Medicine, 47, 410-412. Whittle, M. W., Herron, R. L., Cuzzi, J. R. and C. W. Keys (1976). The effects of prolonged space flight on the regional distribution of fluid, muscle and fat; biostereometric results from Skylab. AGARD Conference Proceeding No. 203, 5 p .
.............•.•.. •• ..
..••
.. ••
...... ..... •••••
••••• •••••• •••••• •••••• •••••• ••••••
....... ....... •••••••
••••••• .• ....... ••••••• .. ......
.• ..... ••••• • ...... ••••• . • ••••• .• ...... . •••••• • •••••• • •••••• • ••••••
...... ... ..... ... .. • ••••••• ,
•••••••. .. • .......
...... .
•.. ••••••• •••••••• •••••• •• •••••• • • •••••••
........
••••••• ...... c•
.....
••••••• ••••••• •••••• •• • •••••• ••••••••••••••••••••• .........•...• ~~
Figure 1.
A typical simplified wheelchair simulation.
Wheelchair Analysis -
A CAD/CAM Application
2001
----, \ \
, \ \
\
, \ \ \ \
---------
---------~
" '1 11
I,
"
i!
Figure 2.
A typical wheelchair analysis showing deformation. Solid lines indicate the structure prior to loading. Dotted lines show deflections created by the application of loads. Deflections are exaggerated for effect.
Discussion to Paper 69.3 J. Hatvany (Hungary): My impression is that the tools you are using are a case of overkill with respect to the magnitude of the wheelchair problem - especially in comparison to the results in actual wheelchair design that you have presented. V.A. Rogers (USA): I believe that to be a comment rather than question so there is nothing to add. Y. Nakamura (Japan): Has the SPAR program any relation to NASTRAN? V.A. Rogers (USA) : SPAR was developed by the same people who developed NASTRAN. SPAR is specifically designed for the minicomputer and I believe it has most of the capabilities that NASTRAN has, although I am not familiar with NASTRAN other than to know that it is very popular. K. Tani (Japan) : How many percent in weight do you deduce in your wheelchair design? V.A. Rogers (USA): We are in the early stages of the project and have not yet performed an optimization based on weight. G.E. Ennis (USA): To exactly what mini-
computer is A2000 implemented and to what extent are AD2000 and RIM integrated? V.A. Rogers (USA): Joint locations from AD2000 are transferred to RIM as are element properties . .. From RIM a command file is generated and sent to SPAR. The output from SPAR is then sent back t o RIM for analysis. The mini-computers used are the PRIME 400 and VAX-ll. H. Yoshikawa (Japan) : Your contribution is very important from the viewpoint that you showed industrial techniques can be applied to social problems. I am especially interested in formalization of demands in such cases as rehabilitation. The description of demands for the wheelchair might not be so different from the normal industrial products. How did you formalize the demand for it in your project? V.A. Rogers (USA): Defining the live loads, the wheelchair experiences and environmental specifications for its design are the most difficult portions of the wheelchair project. This is why the human body simulator is necessary. It may be that we will have to employ active elements in the final model.