When it comes to the choosing of pneumatic actuators, experts have advocated a multiple criteria decision making approach that can be traced back to more than fifty years ago or even earlier times. At the same time, the study about the actuator FAQ goes on in parallel with development of electric actuators decision making methods in the application of the utility theory. In general, the majority of the study and the methods are involved with making preference decisions over a set of alternatives that are characterized by a variety of criteria like the common fuzzy object evaluation and the gray correlation analysis so that mathematic model of pneumatic actuators can be established around the machines’ mechanical properties. However, in actuator FAQ, the amount of the indexes can be overwhelmingly huge and thus it might be a bit difficult to make up your mind when you intend to choose the right pneumatic actuators. Thanks to the gray correlation analysis, comprehensive pneumatic actuators evaluation can be obtained in a simple manner from both qualitative and quantitative factors without the need for any extra time. What is more, this analysis method involves the use of a hierarchical structure to deal with the actuator FAQ as major representatives of the the decision problem. And in the gray correlation analysis, it is useful to incorporate intangible qualitative criteria with tangible quantitative actuator FAQ, according to a number of articles and books that are committed to the study of this method and its application. As a matter of fact, the gray correlation analysis requires the pneumatic actuator decision maker to compare each alternative in the first place and then determine which one is more preferable in terms of working efficiency and performance.
On the other hand, with the common fuzzy object evaluation, pneumatic actuator decision makers in general do not agree or disagree with each other since the evaluation data are already presented in detail. Under this circumstance, the decision makers tend to agree on which one of the pneumatic actuators will have the best performance is a specific condition and just need to take consideration of the actuator FAQ at the same time. What is more, the higher level of agreement is not impossible when using the common fuzzy object evaluation because the amount of information elicited by this method is greater than that of the gray correlation analysis, which may result in a more accurate reflection of preferences on the pneumatic actuator. To conclude, although the common fuzzy object evaluation may generate more information bits, it remains a better choice over the gray correlation analysis in choosing the right pneumatic actuator since the later may require extra time in comparison to the former.