This paper presents a control algorithm for semi-active suspensions to reduce the braking distance of passenger cars. Active shock absorbers are controlled and used to influence the vertical dynamics during ABS-controlled full braking. The core of the approach presented in this paper is based on switching control logic. The control algorithm is implemented in a compact class passenger car. Test drives on a real road, using a braking machine for reproducibility reasons, have been executed. The main result of the research work presented is the experimentally achieved proof that a reduction of braking distance by control of active shock absorbers is possible in general. The reduction achieved is 1.3 %, compared to the best passive damper setting-hard damping. This value ought to be seen as starting value for optimization circles now following. Due to the small differences in braking distance for different damper settings it is only now that it is possible to execute optimization processes for the controller parameters. Furthermore, the integral of dynamic wheel load has been identified as the connecting element between vertical and longitudinal dynamics. The theoretically derived approach has been validated in experiments. It could also be shown that both wheel load and braking force can purposefully be affected by switching the active shock absorbers from soft to hard setting or vice versa. From 105 braking test drives the statistically confirmed conclusion can be drawn that the control algorithm developed shortens the braking distance as well as it decreases the velocity integral. In upcoming test drives the control algorithm will be tested for other initial velocities and other proving grounds, like an ideally flat pavement and a very rough road. Beside that the pitching of the vehicle and its effect on the braking performance will be investigated in more detail. With the help of the wheel load integral it is possible for the first time to purposefully incorporate a quantity of the vertical dynamics to the control of lateral and longitudinal processes. Up to now, ABS- and active shock absorber-controller work independently from each other. By using the wheel load integral, wheel load and braking torque induced slip oscillations can be measured and handled separately from each other. For example, the ABS-controller does not necessarily have to react on every increase of braking slip. If it is a wheel load induced one, the active shock absorber-controller is the better choice to handle it. The connection of active shock absorber- and ABS-controller-or better, the merger of both to a new braking distance reducing approach-is promising and lets expect a further reduction of braking distance. Besides controlling the active shock absorbers during an ABS-braking, the approach presented can also be used for other states of driving dynamic. Connecting the Electronic Stability Program (ESP) with the shock absorber-controller in curve driving situations is possible and should be investigated in more detail.


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    Titel :

    Improving braking performance by control of semi-active suspension


    Beteiligte:
    Niemz, Tobias (Autor:in) / Winner, Hermann (Autor:in)


    Erscheinungsdatum :

    2007


    Format / Umfang :

    12 Seiten, 6 Bilder, 11 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch