Hysteretic controllers

Author s Comments The first company representative seems to have dished out the stock reply on reducing output ripple in conventional (PWM) regulators. But his second point is a fairly good run-down on capacitors in general. However, the 2621 is a hysteretic controller and therefore depends on output ripple to behave. So the advice doesn t really apply. 

Looking at the blog entry that follows, this one is technically correct if rather peremptorily explained. Hysteretic controllers are actually quite simple. In Chapter 2 we discussed the leverage factor of a voltage divider. In this case the reference is 1.24V and Vom is 3.8V. So the leverage factor is 3.8/1.24 = 3.0645. So... 

Another form current-mode control is called hysteretic current-mode control. Here both the peak and the valley currents are controlled. This is obviously better for continuous-mode forward for boost converters. It is somewhat complicated to set-up, but it does offer very fast response times. It is not a very common method of control and its frequency varies. 

Structures made of transforming materials exhibit a striking capacity to hysteretically recover significant deformation with a controllable amount of energy absorbed m the process. The unusual properties of these materials are due to the fact that large deformations and inelastic behavior are accomplished by coordinated migration of mobile phase or domain boundaries. Intensive research in recent years has led to well-defined static continuum theories for some of the transforming materials (see Pitteri and Zanzotto (1997) for a recent review). Within the context of these theories, the main unresolved issues include history and rate sensitivity in the constitutive structure. 

Like the Wein-bridge oscillator, the Schmitt trigger only needs a power supply of 5 to 15V to begin its oscillation. This entails that the maximum lead that the clock pulse can drive is in the 1 mA range. The oscillation is controlled by the RC time constant and the hysteretic native to the Schmitt trigger. 

With all batch techniques, there is the common problem of not removing the desorbed species. This can cause an inhibition of further adsorbate release (Sparks, 1985, 1987a), promote hysteretic reactions, and create secondary precipitation during dissolution of soil minerals (Chou and Wollast, 1984). However, one can use either exchange resins or sodium tetraphenylboron, which is quite specific for precipitating released potassium, as sinks for desorbed species and still employ a batch technique (Sparks, 1986). Also, since in most batch methods the reverse reactions are not controlled, problems are created in calculating rate coefficients. This is particularly true for heterogeneous systems such as soils. 

The scanner controlling the tip position and tip scanning is made from piezoelectric materials. The intrinsic physical and mechanical properties of piezoelectric materials, such as nonlinear piezoelectricity, hysteretic piezoelectricity and creep deformation affect the performance of the scanner. Such properties can generate distortion of SPM imaging during scanning. 

If any systems we design are to operate as potential electronically controllable molecular-based memory devices, then they must show a similar hysteretic profile, except Magnetization has to be replaced by Current and External Magnetic Field by Voltage . 

Since primary carbon black structure tends to increase the effective volume loading, it will accentuate the hysteretic effects. However, because of the intimate relationships between primary structure, dispersibility and secondary aggregation, the influence of primary structure will not always emerge clearly. In carefully controlled experiments energy dissipation increases moderately with primary structure with little change in resilience. This is illustrated in Table 4 with data on some of the vulcanizates of Fig. 11, Section V-3. 

Suzuki M (1991) Amphoteric poly(vinyl alcohol) hydrogel and electrodynamic control method for artificial muscles. In D. DeRossi, K. Kajiwara, Y. Osada, A. Yamauchi (ed) Polymer gels Fundamentals and biomedical applications. Plenum Press New York, 221-236 Suzuki A, Suzuki H (1995) Hysteretic behavior and irreversibility of polymer gels by pH change. J OiemPhys 103 4706 710... 

BasiU M De Angelis M. (2007b). Optimal p>assive control of adjacent structures interconnected with non-Unear hysteretic devices. Journal of Sound and Vibration, vol. 301 p. 106-125, ISSN 0022-460X... 

Ashrafi, S.A., Smyth, A.W. Betti, R. 2005. A parametric identification scheme for nondeteriorating and deteriorating non-linear hysteretic behavior. Structural Control and Health Monitoring, 13,108-131. 

Muto, M. Beck, J.L. 2008. Bayesian updating and model class selection for hysteretic structural models using stochastic simulation,/owrwa/ of Vibration and Control, 14, 7-34. 

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