Design is the creation of synthesized solutions in the form of products or systems
that satisfy customer’s requirements [9, 25, 30, 34]. When we are given a design
problem, we try to make the best use of our knowledge and the available information
to understand the problem and generate as many feasible solutions as possible. Then
we evaluate these concepts against the customer’s requirements and select a most
promising concept for design analysis and design optimization. We may think of the
design as a mapping of the customer’s requirements into a physical embodiment. The
better we understand the problem associated with the customer’s requirements, the
.better design we can achieve
The design process can be logically divided into three interrelated phases: (1) product
specification and planning phase, (2) conceptual design phase, and (3) product
design phase. During the product specification and planning phase, we identify the
customer’s requirements and translate them into engineering specifications in terms
of the functional requirements and the time and money available for the development
and plan the project accordingly. In the conceptual design phase, we generate as
many design alternatives as possible, evaluate them against the functional requirements
and select the most promising concept for design detailing. A rough idea of
how the product will function and what it will look like is developed. In the product
design phase, we perform a thorough design analysis, design optimization, and simulation
of the selected concept. Function, shape, material, and production methods are
considered. Several prototype machines are constructed and tested to demonstrate
the concept. Finally, an engineering documentation is produced and the design goes
into the production phase. However, if the concept selected for the product design
is shown to be impractical, it may be necessary to go back to the conceptual design
phase to select an alternate concept or to generate additional concepts. In this regard
it may be necessary to reevaluate the engineering specifications developed in
.the product specification and planning phase
Design is a continuous process of refining customer requirements into a final product
.The process is iterative in nature and the solutions are usually not unique
It involves a process of decision making. A talented and experienced engineer can
often make sound engineering decisions to arrive at a fine product. Although the
third phase is usually the most time consuming phase, most of the manufacturing cost
of a product is committed by the end of conceptual design phase. According to a
survey, 75% of the manufacturing cost of a typical product is committed during the
first two phases. Decisions made after the conceptual design phase only have 25%
influence on the manufacturing cost. Therefore, it is critical that we pay sufficient
attention to the product specification and conceptual design phases. One approach
for the generation of concepts is to identify the overall function of a device based
on the customer’s requirements, and decompose it into subfunctions. Then, various
concepts that satisfy each of the functions are generated and combined into a complete
design. Techniques for generation of concepts include literature and patent search
imitation of natural systems, analysis of competitor products, brainstorming, etc
In this text, we concentrate on the conceptual design phase of mechanisms. The
conceptual design is traditionally accomplished by the designer’s intuition, ingenuity
and experience. An alternate approach is to generate an atlas of mechanisms
classified according to functional characteristics for use as the sources of ideas for
mechanism designers [1, 17, 19, 20, 21, 24]. This approach, however, cannot ensure
the identification of all feasible mechanisms, nor does it necessarily lead to an
.optimum design
Recently, a new approach based on an abstract representation of the kinematic
structure, which is somewhat similar to the symbolic representation of chemical
compounds, has evolved. The kinematic structure contains the essential information
about which link is connected to which other links by what types of joint. It can be
conveniently represented by a graph and the graph can be enumerated systematically
using combinatorial analysis and computer algorithms [6, 7, 8, 10, 13, 15, 35]. This
approach, which appears to be promising, is the basis of this text
In the following, we briefly introduce the methodology and review some of the
fundamentals of the kinematics of mechanisms to facilitate the development of the
.methodology
1.2A Systematic Design Methodology
The methodology is based on the application of graph theory and combinatorial
analysis. First, the functional requirements of a class of mechanisms are identified.
Then, kinematic structures of the same nature are enumerated systematically using
graph theory and combinatorial analysis. Third, each kinematic structure is sketched
and qualitatively evaluated according to its potential in meeting the functional requirements
Finally, a promising concept is chosen for dimensional synthesis, design
optimization, computer simulation, and prototype demonstration. The process may
.be iterated several times until a final product is achieved
:We summarize the methodology as follows
Identify the functional requirements, based on customers’ requirements, of a -
.class of mechanisms of interest
,(
etermine the nature of motion(i.e., planar, spherical, or spatial mechanism
ما دانشجویان مکانیک دانشگاه آزاد سمنان هستیم،که جهت افزایش اطلاعاتمون در زمینه مکانیک مطلب قرار میدهیم.