Mohapatra, Pratap K. J. with Sushil K. Sharma, "Synthetic Design of Policy Decisions in System Dynamics Models-A Modal Control Theoretic Approach", 1983
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Researchers and practitioners in System Dynamics usually folllow a trial-and-error process to design new policy decisions. They mainly use causal loop diagrams for this purpose. However, these diagrams portray 'directions' of influence and not its 'strength'. Therefore, the process of policy design becomes time consuming especially for a beginner and those working with insufficient computer facility. This paper presents an alternative approach for policy design using Modal Control Theory. In this approach, policy variables are treated as control variables by delinking them from other variables. This generally leads to greatly simplified models which are free from many nonlinearities. Providing that this reduced system is linear and controllable, it is possible to synthetically generate control policies by modal control theory to ensure any prescribed degree of stability. These theoretical control policies can then be used to design realistic policy decisions. The Chapter-8 problem of Coyle is used here as a test example. It is shown that policies designed in the light of modeal control theoretic results are superior to those suggested by Coyle.