Boots – shoes – and leggings
Patent
1987-10-28
1990-04-03
Fleming, Michael R.
Boots, shoes, and leggings
364183, 364148, G06F 100, G06F 1520
Patent
active
049145649
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to the improvement of the accuracy and stability of control systems with a particularly low energy requirement. In addition to the components characteristic of every control loop, namely (see FIG. 1), a suitable measuring element (12) for determination of the deviations of the system to be controlled, the controlled system (16), from its desired state, a controller network (13) (or a control algorithm corresponding to its function in a programmable digital electronic system) and a final-control-element assembly (15) generating the forces or moments required for control, control loops of low corrective energy consumption of the type here considered further comprise a dead-band section (14), which usually is disposed between the controller network (13) and the final control element (15).
BACKGROUND OF THE INVENTION
A dead-band section is defined with respect to its transfer characteristics in that in the case of input quantities whose magnitude is below a certain preset threshold value it does not supply an output signal whereas it reproduces the input-signal components which exceed the threshold values unchanged so far as their frequency and phase are concerned, though with the amplitude reduced by the constant magnitude of the threshold value.
In addition to dead-band sections of the above type, there are a number of control-loop components with a high degree of nonlinearity which serve for the execution of switching functions, for example, hysteresis elements, relay or three-point elements, which may likewise incorporate preset response thresholds, with the latter, however, serving primarily to secure unambiguous circuit states. The introduction of an artificial dead band into a control loop has a beneficial effect on corrective energy consumption only because the final control elements are not actuated so long as the deviations are below the response threshold of the dead-band section. Only when external disturbances or dynamic events in the control loop give rise to deviations which result in an overshooting of the response thresholds of the dead-band section are forces and/or moments generated which tend to reduce the deviation, but only until the response thresholds are again undershot. Especially during periods and operating conditions when external disturbances affecting the controlled system are slight, the system will remain within the range of the dead band for a relatively long time and consume no corrective energy.
Now from these basic facts it follows directly that the absolute value of the response threshold is a direct measure of the attainable accuracy of the control system, and that the demands for saving corrective energy and for accuracy conflict with each other. While the accuracy increases when the range of the dead band is increased, the frequency of corrective interventions also increases, and with it the consumption of energy. If, on the other hand, the deadband is dispensed with altogether, the final control elements will be actuated even by the unavoidable system and measured-value noise, and an increase in accuracy will be limited by the increasing stochastic excitation of the control-loop dynamics. Moreover, the noise level in a control system, that is, signal noise and system dynamics, is dependent, apart from external disturbances, in large measure on environmental and operating conditions, such as temperature fluctuations, parameter tolerances, aging processes and the like, which results in a sizable range of variation and considerable uncertainty in the system behavior of conventional control loops and does not permit the setting up of a fixed dead band that is optimally adjusted to changing operating conditions. Thus, once a dead band has been set to a fixed value allowing in particular for the high-frequency noise level for nominal conditions, the "effective dead band", that is, the actually effective deadband range remaining between noise amplitudes and threshold value, changes in an inverse ratio to the magnitude of the di
REFERENCES:
patent: 4463432 (1984-07-01), Carter
patent: 4509110 (1985-04-01), Levesque
patent: 4604681 (1986-08-01), Sakashita
Bittner Helmut
Surauer Michael
Fleming Michael R.
Messerschmitt-Bolkow-Blohm Gesellschaft mit beschrankter Haftung
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