Passive in-vehicle safety systems such as the air bag and the belt restrain the occupant during a crash. However, often their behavior is not optimal in terms of occupant injuries. This paper discusses an approach to design an ideal restraint system. The problem is formulated as a feedback tracking problem with the objective to force the controlled variables, i.e., the acceleration of the head and the chest of the occupant, to follow a priori defined reference signals by simultaneous manipulation of the belt and the air bag. The reference signals have to reflect minimal injuries to the head, the chest, and the neck. More or less realistic numerical models of a crash test are far too complex to be used in control design processes. Therefore, a strategy is presented to derive simple, linear MIMO models. These models approximate the local dynamic behavior of the complex model and are suitable for control design. Analysis of the interactions in these simple models makes it plausible that the control design problem can be split into two separate tracking problems. Next, stabilizing low order controllers are designed using these models, and implemented in the closed loop system with the realistic numerical model. Results are presented, suggesting that feedback control with low order controllers is extremely effective as a basis for ideal restraint systems. Reductions of the adopted injury measures of at least 40% in comparison with the uncontrolled restraint system are achieved.
To minimize occupant injuries, passive in-vehicle safety systems like the safety belt and the airbag restrain the occupant during a crash. This paper presents a design approach for a feedback controller for the belt force to reduce the maximum chest acceleration as a measure for the risk of occupant injuries. Only frontal crashes are considered. The available, experimentally validated numerical crash model is too complex to be used as a controller design model. Therefore, approximate linear models for the transfer from belt force to chest acceleration are derived by analysing the effect of stepwise perturbations of the belt force on the chest acceleration. Using these linear models, loop shaping is applied to arrive at a controller that satisfies a set of a priori defined criteria. The controller is implemented in and evaluated with the complex crash model, showing that a reduction of approximately 60 per cent in the adopted injury measure can be achieved. Furthermore, it is shown that this approach can be applied in different situations.Such real-world crash tests are very expensive and time consuming. For the design of (adaptive) Eindhoven, The Netherlands. email: m.steinbuch@tue.nl JAUTO29
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