More about Analogies
Editor | On 08, May 1998
By Kalevi Rantanen
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Different analogies are widely used as problem solving tools. The engineer can compare analogical systems consisting of object, tool, energy source, energy transmission and control. This like analogy is described in the paper of E. Domb. Using Analogies to Develop Breakthrough Concepts (TRIZ Journal April 98). I would like add another analogy that can be called a feature transfer analogy, or a bisystem analogy.
Feature transfer means that the “pluses” of several systems are accumulated into the new product, and the “minuses” are removed. Competing systems are compared pairwise. “Pluses” are combined and drawbacks “neutralized”. Innovative principles, effects, standard solutions etc. are used for realizing the feature transfer.
An example: mechanical and quartz watches are alternative systems for measuring time. The mechanical watch do not need any battery (+), but is complex (-). The quartz watch is simple (+), but requires a battery. There are already watches that combine the pluses of mechanical and electronic timepieces. Seiko Kinetic converts the kinetic energy of moving hand to electrical one. CitizenÂ´s Eco-Drive uses light as energy source. We can describe the solution by a simple table or matrix:
|Mechanical Watch||+ No battery||– Complex|
|Quartz Watch||– Battery needed||+ Simple|
|Quartz watch without batteries||+ Simple||+ Easy|
Now we can use this known solution to solve new problems. For example: how to improve a clinical thermometer (fever thermometer). There are at least two competing systems:
- Traditional mercury thermometer: Simple (+), but uncomfortable to use (-)
- Digital thermometer: Comfortable (+), but requires a battery
The matrix or table:
|Mercury thermometer||+ Simple||– Uncomfortable|
|Digital thermometer||– Battery needed||+ Comfortable|
A watch analogy gives nearly ready answer. A mercury thermometer should, anyway, be “tuned” by shaking. We can use “shaking power” to charge a thermometer. Or the user can press the device, and the energy of pressing can be converted to electrical one. Or the energy of light can be used.
To solve the same problem we can use the system analogy (Figure 3 in DombÂ´s paper). The worksheet seems as follows:
|ELEMENT||EXAMPLE, START||EXAMPLE, IMPROVED||MY PROBLEM, START||MY PROBLEM, IMPROVED|
|Tool||Quartz watch with battery||“No battery quartz watch”||Thermometer with battery||“No battery thermometer”|
|Energy Source||Battery||PersonÂ´s hand/Light||Battery||Muscular power/Light|
|Guidance & Control||Human||Human||Human||Human|
LetÂ´s compare the two models:
The “two pluses matrix”:
- Contradictions (pluses coupled with minuses) are displayed
- The inner structure of the system is consciously ignored
The system model:
- The main elements of the system are identified
- Features and contradictions remain outside the model
We see that the models complement each other.