A Case Study in Creative Problem Solving in Engineering Design JAMES C. CONWELL Department of Mechanical Engineering Louisiana State University

GEORGE D. CATALANO Department of Mechanical Engineering Louisiana State University

JOHN E. BEARD Department of Mechanical Engineering Michigan Technological University

ABSTRACT The senior design sequence at Louisiana State University is a two semester, design, build and test experience. Groups of two, three or four students work together in a team setting to produce a functioning prototype which meets predetermined design goals. One particular project, which had as its goal the requirement to extend the reach of an occupant confined to a standard sized wheelchair, was used as a mechanism to integrate the development of critical and creative thinking skills necessary to solve technical problems into the undergraduate mechanical engineering curriculum. Special attention was paid to the nature of creativity and exercises were introduced in order to facilitate this historically neglected aspect of engineering education. The result of this effort was a unique wheelchair, which provides the occupant access to shelves located over their head or objects on the floor via an adjustable height seat.

I. INTRODUCTION As engineering educators, how do we provide the engineers of tomorrow with the problem solving skills needed in a rapidly changing technological world? At Louisiana State University, we have used the mechanism of the senior design course sequence to meet this challenge. The two semester sequence forces students to move beyond the lower levels of learning (memorization and recitation) as described in Bloom’s taxonomy(4) to the highest levels or most difficult (design, implementation and evaluation). In To Engineer is Human(1), Petroski writes “the idea of design—of making something that has not existed before—is central to engineering.” Harrisberger(2) notes in a chapter entitled “The Design Process . . . Doing Engineering Problem Solving”: ‘‘The crux of the design process is creating a satisfactory solution to a need . . . it is what engineering is all about— using knowledge and know-how to achieve a desired out-

come. Designing is problem solving. It is creative problem solving.’’ These goals can be accomplished through the careful guidance of a senior design team as it moves through the various stages of a design project. One such project, the subject of this report, challenged the student team to design a device to extend the reach and improve the accessibility of physically handicapped individuals confined to a wheelchair.

II. PROBLEM STATEMENT AND THE DESIGN PROCESS Imagine someone working feverishly away on a sketch of a new gadget, a new electronic circuit diagram, or a water drainage elevation plan with pencil and sketch pad in hand. In a moment of contemplation, the pencil slips and falls to the floor, out of immediate reach. Imagine someone brewing a cup of coffee and noticing the sugar bowl perched precariously on the top shelf in the kitchen pantry, just beyond the reach of his or her outstretched hand. Trivial challenges to be sure—to pick up the pencil off the floor or to reach up for the sugar bowl, unless that same person is confined to a wheelchair. These challenges were the basis of a task given to a group of senior level mechanical engineering students: to design and build a device that allowed the wheelchair occupant to pick up objects off the floor and to grasp something from a raised shelf. Once the task was identified, the students were provided three different models for analyzing the processes that serve as the foundation for effective solution of problems. The models chosen are those described by Koberg and Bagnall(5), Bransford and Stein(6) and Harrisberger(3). In fact, a great deal of research focused on the steps used in successful problem solving has taken place over the last two decades; so the choice of a particular model is somewhat arbitrary. The Koberg and Bagnall, Bransford and Stein, and Harrisberger approaches all were accessible to our students, and thus, proved to be useful frameworks for activities and discussions throughout the design sequence. Along with the introductions of the different models, emphasis was placed on the importance of being able to criticize ideas (critical thinking skills) and generate alternatives (creative thinking skills). Critical thinking is convergent, seeks to assess worth or validity of something that already exists, and applies accepted principles. It involves the analysis of factual claims, the logic of arguments, and the analysis of basic assumptions. Creative thinking is divergent, usually seeks to generate something new, and often violates accepted princi-

© 1993 American Society for Engineering Education. Reprinted from Journal of Engineering Education, Vol. 82, No. 4, October 1993.

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ples. Creative thinking is driven by a desire to seek the original; it values mobility, revels in exploration, requires flexibility and respects diversity. In problem solving, there is a shifting back and forth between the critical thinking skills and the creative thinking skills. In fact, research has shown that critical and creative thinking skills are synergistic, the development of one set of skills will aid in the development of the other set. Critical thinking skills are perhaps somewhat easier to teach as they are easier to quantify(9). Factual accuracy can be ascertained, fallacies in the development of a logical argument can be identified and the validity/applicability of basic assumptions can be checked. The nature of creativity and the development of creative thinking skills is a much more abstract and daunting task for the educator(10,11). Some strategies exist for enhancing creative solutions to problems, for example, Bransford and Stein(12) list the following methods: 1. Make implicit assumptions explicit through searching for inconsistencies, worst case scenarios, making predictions and seeking criticism. 2. Fractionation involves breaking ideas into component parts, thereby breaking down ‘programmed’ assumptions. 3. The use of analogies. 4. Brainstorming incorporates the first three activities into a group setting in order to facilitate the quantity of new ideas. 5. Incubation requires breaks in a determined search for a solution and helps to alleviate mental fatigue. 6. Communication of new ideas to others, for it is in the process of putting ideas into words that new ideas come to mind.

III. APPROACH TO THE DESIGN PROBLEM After the introduction to design methodology and the importance/development of both critical and creative thinking skills, a student design team was given the following problem: Design ‘something’ to help an individual (perhaps a paraplegic) confined to a wheelchair pick up an object off the floor and retrieve an object resting on the top shelf of a kitchen cabinet. That was the extent of the formal direction given to the three students. In order to have the students become personally involved with the project, they were led through a series of role-playing exercises, designed to help them more fully understand the

limitations of a wheelchair occupant. This caused the design team to become personally involved with the project, an important factor in determining the success of problem solving efforts. Next, the students were asked to respond to a series of questions such as “What is the scope of the project?”, “What is fixed?”, “What can I control?”, “What are my resources?”, and “Where can I seek additional/outside advice?”. Here the design group quantified the task by measurement of distances from the floor to the tips of an extended arm of an average height person sitting in a wheelchair and the height such an average person could reach over his/her head. Critical thinking skills were essential in that this stage of the problem solving involves the gathering of relevant information and the dissection of main tasks into small sub-tasks. In the case of a partially paralyzed individual, the main problem became one of extending his/her accessibility in a vertical plane. A standard wheelchair already provides lateral traversing capability so that it is this additional degree of freedom of movement that is the central issue, and hence one of the major design obstacles. To meet and overcome this barrier, the students were challenged to use their creative thinking skills both individually and collectively in brainstorming to generate possible solutions to the posed problem. To assist in the generation of ideas, the students were introduced to the notions of leap-frogging (using ideas/methods/solutions from other descriptions) and piggybacking (modifying/amplifying ideas previously given). A partial listing of the ideas generated included: ● A periscoping gripper ● An air cushion (Hovercraft-type) wheelchair ● Movable shelving ● Movable flooring ● An adjustable height wheelchair Having generated a number of possible approaches, a final decision was made after a careful consideration of its ‘doability’ within the limitations of the course and whether or not it successfully achieved the identified goals. To aid in this selection, the design team was introduced to attribute listing -an evaluative technique of identifying pros and cons of possible options. Lists generated for the periscoping gripper and the adjustable height wheelchair are shown in Table 2. The design team then further refined each of these choices, using critical thinking skills combined with engineering analysis of each of the above design choices. The engineering studies included the following:

Table 1. Comparison of Problem Solving Models. 228

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© 1993 American Society for Engineering Education. Reprinted from Journal of Engineering Education, Vol. 82, No. 4, October 1993.

Force and Stress Calculations Stress levels and factors of safety were determined for all critical members contained in each of the design choices. Ease of Manufacturability A determination of the number of machining operations, as well as tolerance requirements, assembly difficulties and availability of materials and parts were considered. Reliability and Safety Component fatigue, overall stability, inherent user dangers and miscellaneous safety considerations for the individuals who might be adjacent or in proximity to the finished project were all considered. The list of attributes (contained in Table 2) was then combined with the information collected from engineering calculations to determine a potentially ‘best’ design solution. Following an extensive investigation, the design team chose the adjustable height wheelchair concept. This particular choice was made for several basic reasons: ● Capability of the finished project to meet a wide variety of the needs of a disabled individual. In addition to the basic needs of a person confined to a wheelchair (transportation and ease of use) an adjustable height wheelchair would provide vertical access in a unique and compact package. ● The amount of training required for an individual to use this design would be minimal. Many occupants of wheelchairs are already familiar with the operation of electric wheelchairs, and a adjustable height wheelchair would be practical extension to that concept. ● An adjustable height wheelchair would be a unique design, and enable the student group to design, build and test a device that is not readily available upon the open market. This would require extensive applications of innovation and creativity. ● Many current users of wheelchairs indicated to the students

that an adjustable height wheelchair seat would be the most readily accepted design choice. Implementation means “making real” or “realizing that which has been intended”. Having chosen the adjustable height wheelchair as their solution, the students set out to make the chair a reality. The following is an outline of the parameters and constraints for the wheelchair as discussed and agreed upon by the design team. The main task for the wheelchair is to provide disabled individuals with greater reach by lowering and raising the seat. The variable elevation was chosen to extend from 10 inches to 40 inches from the floor. These elevations were determined in the following manner: 1. The lowest position was determined by having each member of the design team sit on a stack of blocks. The height of the stack was adjusted until an object on the ground could easily be picked up without excessive or abnormal bending at the waist. When the height of the stack was approximately 10 inches, each member in the group could pick up the object. This distance was also verified using the dimensions of the standard 50th percentile male and female. 2. The elevation of the seat for the normal seated position was determined through measurement of existing standard wheelchairs. In addition, the dimensions of wheelchairs were obtained from several wheelchair manufacturers’ catalogs. Nearly all sources indicate that approximately 18 inches above the ground is a standard seat elevation. 3. The highest elevation was determined by measuring the distance that can be reached by a standing person and subtracting the distance that can be reached in a seated position. Approximately a 35 inch seat elevation was required for an average-height seated person to obtain comparable reach with a standing person. Possible solutions to this overall design problem were obtained through individual ‘brainstorming’. Each design team member was required to conceive and sketch twenty different mechanisms or ideas that could accomplish the lift require-

Table 2. Comparative Analysis of Basic Design Choices. © 1993 American Society for Engineering Education. Reprinted from Journal of Engineering Education, Vol. 82, No. 4, October 1993.

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ments. At this stage, no restrictions were placed on the design, even far-fetched ideas were encouraged. Each of the ideas was presented to the whole team for discussion and evaluation. All of the designs were given consideration. Designs which did not seem physically or economically possible were eliminated. For example, it was decided early on that any modification to a wheelchair should not change the basic size (or ‘footprint’) of the chair. Many of the suggestions made at this stage were, of necessity, discarded due to this constraint. For example, a Hovercraft type wheelchair would have required a large skirt which extended outside the frame of the wheelchair to support the weight of the chair and the occupant. Of the remaining designs, the best five were selected on the basis of: ● Component availability: A determination was made regarding whether components could be located at local supply houses or required the order of a specially constructed element. ● Economics: As with all of the groups in the senior design sequence, this particular group was required to complete the project within a certain budget. Which of the designs could be constructed and remain within the budget?

Manufacturing Ease: The number of machining operations, material choices and assembly procedures were all considered. ● Appearance and General Operation: The student group did not want to attract any undue attention to the user of this type of specialized wheelchair. As a result, appearance became a major design criteria. Additionally, ‘user friendliness’ was considered at each stage of the design process. To help determine evaluative criteria for this step, the student group utilized input from a local disabled individuals support group. This group suggested several criteria by which to judge the design, including the required location of controls, overall placement of the lift mechanism, and final appearance of the device. After several design team meetings and discussions (highlighted in Table 3), it was determined that the best lift mechanism for the wheelchair would be a double scissors mechanism. Two other major subsystems of the wheelchair were identified by the project group as the base subsystem and the leg support subsystem. As previously stated, a fundamental design criteria for the wheelchair base was that its overall dimensions should not be ●

Table 3. Comparative Analysis of Five Lift Mechanisms. 230

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larger than the dimensions of a standard wheelchair base. The design team also determined that the attachments of the lift mechanism should be integrated into the design of the base. This is in contrast to a modular type of design where the lift and the base would be very distinct entities. The modular base/lift design was given significant consideration. If a modular lift mechanism were designed so that it could be easily adapted to fit standard wheelchairs, the mechanism could be manufactured and marketed alone. However, after further analysis, it was determined that the modular design concept could not satisfy the constraints set for this project. The integrated base/lift design was deemed superior to the modular design for the following reasons: ● The integrated design would provide a more stable, secure and safe base for the wheelchair. ● The integrated design would have greater continuity in appearance. ● The integrated design would cost less to manufacture than a modular type of unit. The design team decided that the integrated base design would be best for this project. The leg support subsystem had to meet one important design parameter. Namely, the leg support system must rotate and extend as the seat lowers from the normal seated position to the lowest elevation. After a variety of ideas were considered, the team selected the two best ideas—a combination telescoping and a sliding mechanism. Further evaluation by team members was performed to determine the feasibility of implementing the two concepts into a workable design. This investigation revealed that a slider mechanism under the seat was a more practical solution. The extension of the leg support could be accomplished by simply attaching a push device at the end of the slider. The rotation could be accomplished by attaching another member to the push bar and the support bar. Discussions with individuals familiar with the needs of the disabled (relatives, doctors, nurses and the disabled themselves), assisted in the identification of the other design parameters and constraints associated with the leg support subsystem. First, the leg supports should be completely and easily removable from the wheelchair. This is desirable because it significantly reduces the size of the wheelchair during storage and transportation. Secondly, the leg supports should lock securely at the desired position to provide an adequate sense of security and stability for the user. Finally, the leg supports should rotate to the sides, completely out of the way of the front of the wheelchair. This rotation allows for easier entry and exit to and from the wheelchair. The development of the leg support subsystem followed a similar progression as in the design of the lift mechanism. Each member of the design team “brainstormed” to conceive and sketch several ideas for obtaining the required rotation and extension. Each idea was then presented to the project group and critically evaluated, using many of the criteria previously discussed (cost, manufacturability, etc.) as well as the input of the disabled individuals serving as consultants to this project. The evaluation of the adjustable height wheelchair has been an ongoing process. At the completion of the fabrication of the chair, a series of tests were run in order to document the actual

achieved performance. Information included the following: ● Approximate operational times between electrical battery charging. ● Confidence and comfort of the occupant when the chair is in the fully extended upward position. ● Ease of manufacturability and any/all problems associated with the adjustable height wheelchair’s size and weight. ● Responsiveness of the control system and any noted associated discomfort to the occupant, notably at the beginning and ending of the vertical movement. . ● Effect of the environment on the integrity of the electronic system (especially with regards to rain, snow, etc.) Many of these parameters had to be evaluated by the disabled individuals from the local support group. As a result, some of the criteria were rather nebulous (‘the control joystick seems to be in the right position’) but illustrated to the design group the types of feedback typically received for a project of this type. The design team’s successful efforts were duly noted in their selection as the outstanding senior design (out of a class of eighteen projects) project in the Department of Mechanical Engineering in May, 1990. The award was decided through the vote of the faculty and student body and is the highest recognition of achievement given in Mechanical Engineering at Louisiana State University. The project serves today as a standard by which the efforts put forth by subsequent design teams are judged.

REFERENCES 1. Petroski, H., To Engineer is Human, Vintage: New York, 1992, p. vii. 2. Harrisberger, L., Engineermanship, Brooks/Cole: Belmont, CA, 1982, p. 39. 3. Bransford, J. D. and Stein, B., The Ideal Problem Solver, Freeman: New York, 1983, p. 3. 4. Gross, R., Peak Learning, Tarcher: Los Angeles, CA, 1991, pp. 142-145. 5. Koberg D., and Bagnall, J., The All New Universal Traveler, Kaufman: Los Angels, CA, 1981. 6. Bransford, J. D. and Stein, B., The Ideal Problem Solver, Freeman: New York, 1983, pp. 11-32. 7. Harrisberger, L., Engineermanship, Brooks/Cole: Belmont, CA, 1982, pp. 39-48. 8. Lombardi, L., Moral Analysis, SUNY Press: Albany, 1988, pp. 1-42. 9. Grudin, R., The Grace of Great Things, Tichsnor and Fields: New York, 1990, p. 5. 10. Diaz, A., Freeing the Creative Spirit, Harper Collins: San Francisco, 1992, p. 11. Bransford, J. D. and Stein, B., The Ideal Problem Solver, Freeman: New York, 1983, pp. 93-108 12. Dyson, F., Infinite in All Directions, Harper-Row: New York, 1989, pp. 36-41.

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