Ideal System, Or Why the Question What? May Be More Important Than the
Question How?
Victor Fey, Eugene Rivin
The TRIZ Group, LLC
fey@trizgroup.com,
rivin@trizgroup.com
When solving an engineering problem by the trial-and-error
method, the starting point of the engineer's thinking is usually the given
problem. "My problem is because this part does not perform well. How to improve
it?" these are typical reflections when attempting the problem. The engineer
tries to solve the given problem, that is to find an answer to the question
How? for example, How to increase efficiency of this part? or How
to prevent damage to this part? etc. This implies that an object of
modification is known. However, it may turn out that the real problem is quite
different, and the creative efforts should be concentrated on changing another
object.
A technological system is not a goal in itself, we need it
only to perform a certain function, i.e., to serve some object,
may it be another technological system or a human being. Examples of
interactions between technological systems and objects are shown in Fig. 1.
Various systems may perform the same function. A system is a “fee” for
realization of the required function. Among several systems performing similar
function, a better one is such that requires fewer resources to build and
maintain. An ideal technological system is one that requires no material
to build, consumes no energy, does not need space and time to operate, etc. In
other words, an ideal system is an absent system. A notion of ideal
system is one of the cornerstones of TRIZ. An ideal technological system
does not exist as a physical entity but fully performs the required function.
Fig. 1. A function links a system with an object.
The notion of ideality suggests, before looking for solution
to the question how? to clear up the situation and find the object to
improve, i.e., to answer the question what? How one can realize the
concept of ideality? Since the function has to be performed, some material body
ought to be responsible for this performance. This can be realized by the
following Design Streamlining Approaches:
-
A system is eliminated, if the object of its function is
also eliminated (see Fig. 2,a)
-
A system is eliminated, but the object (or some of its
components) itself performs the function (see Fig. 2,b)
-
A system is eliminated, but another system or the
environment performs its function (see Fig. 2,c).
Fig. 2. Design Streamlining Approaches.
The following examples illustrate these approaches.
Case Story 1
Initial situation
This case story relates to a robotic test station for
computer components. The gripper of the robot (see Fig. 3) performs
complex manipulations (clamping, handling, and inserting) with very delicate
parts. It is energized by two vacuum lines and four compressed air lines and has
several sensors transmitting signals via electrical cables. All vacuum,
compressed air, and electrical communications are channeled to the
distribution/control box at the robot base by a so-called “umbilical cord”
corrugated plastic hose encasing all the tubes and wires. The purpose of this
“umbilical cord” is to contain fine particles generated by rubbing between the
tubes and wires. The cord has shown a tendency to rupture in service. The
rapture was due to fatigue associated with large amplitude high-speed link
motions resulting in excessive twisting of the cord. This allowed the wear
particles to escape into environment and led to additional contamination due to
rubbing of the ruptured surfaces.
The company was trying to improve the situation by solving a
problem How to prevent breakage of the cord? However, more durable
plastics for the cord were also more expensive, while not significantly
expanding the cord’s useful life. It was also suggested to evacuate air from the
“umbilical cord,” thus creating a negative pressure that would not let the dust
particles out. However, this would have increased costs.
Fig. 3. Robotic test station.
TRIZ analysis
There is no need to solve this problem, if we know which
part of the test station should be changed. The only part that cannot be
broken or damaged and does not need any service is an absent one. An ideal
“umbilical cord” should not exist. This is possible if the dust particles are
not generated in the first place (see Design Streamlining Approach 1).
Solution
To prevent dust generation, i.e., rubbing between the inner
conduits and wires, they were separated by elastic support braces (see
Fig. 4).
Fig. 4. Ideal "umbilical cord" is absent.
Case Story 2
Initial situation
Compact cars are usually powered by four-cylinder engines
that have intense second order vibrations. The second order frequency at idle
regimes is not fully attenuated and, for some vehicles, may resonate with the
structural modes causing discomfort.
A compact car was equipped with a driver air bag. The steering
column without the air bag had its natural frequency well outside the idle RPM,
but adding the heavy (~1.6 kg or 3.5 lbs.) air bag substantially reduced its
natural frequency. As a result, the steering wheel started shaking with large
amplitudes at the idle regimes. This effect was somewhat alleviated by a (rather
expensive) reinforcement of the steering column, but still the shake intensity
was unacceptable. The shake was so intense that the car could not be launched
before a dynamic vibration absorber - a one-pound (0.5 kg) lead block - was
installed inside of the steering wheel and attached to the steering column by
rubber connectors (see Fig. 5). The lead absorber reduced the shake
marginally. But even with this addition there were numerous customer complaints,
since the shake intensity was much higher than in other car models of this size.
Fig. 5.Conventional remedy for suppressing steering column
shake.
To abate the shake effectively, the absorber had to be at
least 4-5 times heavier, but there was no space available for so large chunk of
lead. Another way of reducing vibration by avoiding the resonance was increasing
the idle rpm, but this would have led to deterioration of the fuel efficiency,
and thus could not be accepted. The situation triggered customers’ complaints
and high warranty costs.
TRIZ Analysis
We need to reduce vibration of the steering column
without major changes in the system. For this, we need to resolve a conflict: a
damper reduces vibration of the steering column but increases its size, weight,
and cost. So, an ideal solution involves elimination the lead damper and
delegating its function to a resource component elsewhere in the car, preferably
in the steering column (see Design Streamlining Approach 2).
Solution
It is known in the theory of vibration that in a complex
dynamic system, such as a car, an appropriately tuned damper may change (reduce)
vibration intensity of a component not directly connected to the damper, or even
remotely located. The important parameters determining performance
characteristics of a damper are its tuning and the “mass ratio” between the
damper's mass and the effective mass of the element whose vibration has to be
reduced.
It was found in testing that the air bag was the most
effective "damper" (see Fig. 5). To a large extent, this was due to the
fact that using the air bag as a damper resulted in separating it from the
steering column structure by flexible tunable connectors. It reduced the
effective mass of the column from 7 lbs. (~3.2 kg) down to 3 - 3.5 lbs.
(~1.4-1.6 kg) and resulted in the mass ratio of about 1.0, as compared with the
mass ratio of the lead-based damper of 0.14. Consequently, shake amplitudes of
the steering wheel were dramatically - six to seven times - reduced (see
U.S. Patent No. 6,164,689 granted to Ford Global Industries, Inc.).
Fig. 6. Airbag-damper.
Case Story 3
Initial situation
A space agency was designing an autonomous probe to land on
Venus. The probe had to carry various electronic devices to the planet. When the
project was close to completion, the agency got a request from a group of
scientists, headed by a renowned chemist, to place one more device into the
probe. This was impossible to do, for the probe was already so crammed with
other devices that one could hardly tuck a matchbox in between them, let alone a
6-kg device. However, the person who signed the request had much clout both in
the space industry and government, so turning him down would have been
politically imprudent. A creative solution to the problem How to find the
extra space for the device? was badly needed.
TRIZ Analysis
As it often happens, a problem that many perceive as a
management one may have an elegant engineering solution. The ideality approach
calls for delegating several functions to one object. What other device
can provide the required function? The only way to "squeeze-in" the extra device
without removing another one was to integrate functions of the former with some
already existing resource.
Solution
A judicious analysis of the probe design revealed the
previously overlooked opportunity. Each planetary probe built earlier had
carried to outer space almost 6 kg (what a coincidence!) of a "dead weight" made
of cast iron. This "dead weight" controlled position of the probe's center of
gravity during landing. The "dead weight" was replaced with the device of
interest (see Design Streamlining Approach 3) that performed both
functions its scientific duty and positioning of the center of gravity.
