Search results

The purpose of this paper is to report on the global practical uniform h-stabilization for certain classes of nonlinear time-varying systems and its application in a separately excited DC motor circuit.

Based on Lyapunov theory, the practical h-stabilization result is derived to guarantee practical h-stability and applicated in a separately excited DC motor.

A controller is designed and added to the nonlinear time-varying system. The practical h-stability of the nonlinear control systems is guaranteed by applying the appropriate controller based on Lyapunov second method. Another effective controller is also designed for the global practical uniform h-stability on the separately excited DC motor with load. Numerical simulations are demonstrated to verify the effectiveness of the proposed controller scheme.

The introduced approach is interesting for practical h-stabilization of nonlinear time-varying systems and its application in a separately excited DC motor. The original results generalize well-known fundamental result: practical exponential stabilization for nonlinear time-varying systems.

The methodology of mainstream neoclassical economics deals with knowledge deficiency problems in a deterministic manner and as “refinements to the theory of economic action rather than rudiments of it” (Coddington, 1975, p. 151). For Shackle (1972), such an approach to the subject is unacceptable, since its deterministic nature is fundamentally at odds with his argument that, to be meaningful, choice must make a difference to the unfolding skein of events. Central to his view of the nature of choice is clearly a rejection of the concept of equilibrium and of the assumptive fiction that co‐ordination is achieved, on a once‐and‐for‐all basis, via the costless efforts of an omniscient auctioneer. If choices are meaningful in Shackle's sense, the skein of events contains many surprises, many incentives for agents to rethink their views of things and change their behaviour. For example, the workings of a multiplier process falsify expectations and these surprises may then spark off euphoric or depressing super‐multiplier effects. In markets for financial assets, “bulls” and “bears” cannot both be right in their predictions, while in product markets the creative exercise of marketing and research and development personnel's imaginations may continuously send out waves and backwashes in keeping with Schumpeterian notions of creative destruction. If one accepts Shackle's alternative starting point, one must sacrifice notions pertaining to “given” preferences and technologies and, with them, the stable functions upon which IS‐LM macro models (see Shackle, 1982(a)) and orthodox value theory are built.

To show how the use of conductor spacings below 4 mil in printed wiring boards (PWBs) can introduce an unanticipated failure mechanism, leading to current leakage and short circuit failure.

The tests in this study were conducted in accordance with IPC‐TM‐650 2.6.25, using boards designed with conductor spacings between plated through holes (PTHs) ranging from 6 to 3 mil and from 8 to 3 mil between PTHs and ground planes. The board types and conductor spacings were selected to include current and future printed circuit board fabrication technology.

For PWBs that may be used in harsh environments where the relative humidity and temperature may approach those of the test environments, even for relatively short periods of time, spacings of 4 mil or less in the materials tested may not be appropriate. However, it is unlikely that the 85°C and 85 percent RH conditions are the minimum conditions to induce this failure mechanism. More tests at lower temperatures and relative humidity combinations should be conducted to evaluate conditions at which this type of failure begins.

The value of the paper lies in that the tests show that the IPC industry standard for conductive filament formation (CFF) testing of PTH‐PTH conductor spacings of 4 mil or less, at 85°C/85 percent RH can introduce a CFF variant failure mechanism, and therefore, may need to be modified to ensure that the test conditions accelerate the CFF mechanism and not other low resistance paths.