smart technologies for safety engineering

Adaptive Impact Absorption 187
(a)
Figure 5.34 Performance of (a) a standard controller in the time domain and (b) the improved controller
in the time domain
examples of operation of the developed controller with and without the regulation unit. The
graphs present exemplary time histories of the velocity sensor input and the generated control
signals. The tasks for the controller were identification of the vertical velocity on the basis
of the signal from a photosensor, determination of the proper control signal sequence and
application of the signal after a minimal time delay. The cases on both graphs are characterized
by an identical initial input of velocity photosensor, which are represented by channel 1 in
Figures 5.34(a) and (b). A dedicated numerical algorithm recalculated the signal readings in
order to determine the impact velocity in the time between the end of the velocity signal and the
beginning of the control signal, depicted as channel 2. The controller performed the required
logic operations and generated the output signal after 40 μs from receiving the velocity input
signal (Figures 5.34(a) and (b)). Channel 2 in both graphs in Figures 5.34(a) and (b) depicts the
time history of the control current generation by the developed system. The response time of
the current generation circuit determines the dominant time delays of the actuation system. In
the case presented in the graphs (a) and (b), the desired current magnitude to generate was 0.5
A. The plot (a) represents the current generation process (channel 2) which is not regulated by
the additional fast current generation unit, with the effect of the time delay equal to ca. 15 ms.
In the graph (b) the regulated generation process is presented, which allowed the current
generation time delay to be reduced to ca. 0.5 ms. Minimization of the response time made it
possible to implement the MR device for the impact application, as the original response time
of 15 ms gave no practical possibilities to control the process that lasts 50 ms in total.
5.5 Adaptive Inflatable Structures with Controlled Release of Pressure
5.5.1 The Concept of Adaptive Inflatable Structures (AIS), Mathematical
Modeling and Numerical Tools
Adaptive inflatable structures are one of the special technologies for adaptive impact absorption.
AIS are structures filled with compressed gas, the pressure of which is actively adjusted during
the impact process. Pressure adjustment relies on appropriate initial inflation and controlled
release of gas during the event. Such active control of internal pressure allows to change the
dynamic characteristics of the inflatable structure and enables adaptation to various impact
(b)