| We develop two new procedures for the discrete event system (DES) software package TCT. Each is useful in the context of working with hierarchical DES, where 'high-level' model abstractions are used to synthesize control action for the original, more complex, 'low-level' plant. The first procedure tests whether or not a DES satisfies the observer property. If it fails to, then its high-level transition structure is modified so that it does. The second procedure tests a DES for the hierarchical nonblocking (HNB) property. When the test is inconclusive the original DES is modified to ensure this property. Each is accompanied by a thorough complexity study and examples to illustrate its utility. We also discuss the pros and cons of various HNB control architectures. |
