Driving an automobile is an example of a goal-directed activity with high complexity in which different behavioral elements have to be integrated and brought into a sequential order. On the basis of the reafference principle and experimental results on temporal perception and cognitive control, we propose a hierarchical model of driving behavior, which can also be adapted to other goal-directed activities. Driving is conceived of as being controlled by anticipatory neuronal programs; if these programs are disrupted by unpredictable stimuli, which require an instantaneous reaction, behavioral control returns after completion of the reactive mode to the anticipatory mode of driving. In the model different levels of anticipation windows are distinguished which, however, are interconnected, in a bi-directional way: (a) Strategic level with a representation of the driving activity from the beginning to reaching the final goal; (b) Segmented tactical level with the sequence of necessary milestones to reach the goal; (c) Maneuver level where actions like passing another car or keeping a lane are controlled; (d) Short-term integration level of a few seconds which allows immediate anticipations; and (e) Synchronization level for sensorimotor control and complexity reduction within neuronal assemblies. A flow diagram schematically describes different driving situations stressing the anticipatory mode of control. In a pilot experiment with 20 subjects using a virtual driving situation in a car simulator predictions of the model could be verified, i.e., subjects showed a significant preference for the anticipatory mode of driving.
Prediction of drowsiness based on an objective measure is demanded in machine and vehicle operations in which human errors may cause fatal accidents. Currently we focused on the pupil of the eye which is controlled by the autonomic nervous system, and easily observable non-invasively from the outside of the body. We employed uneventful driving simulation to induce drowsiness of human subjects, and an anti-saccade task to evaluate their cognitive and motor performance. First we confirmed that pupil diameter fluctuates with large amplitude at low frequencies when the subject is aware of his/her drowsiness as reported previously. During this period, the latency of anti-saccade initiation was elongated and varied. We then found that prior to this fluctuation, pupil diameter decreases gradually in most subjects, and they were not aware of sleepiness during this period. We conclude that this monotonic gradual miosis can be a reliable premonitor of drowsiness.
SUMMARYA pair of hybrid mass dampers has been installed on an actual 23-storey building located in Tokyo. The aim of the dampers is to counteract wind and smaller earthquake excited oscillations. H ∞ control theory has been applied to control the dampers for reducing both bending and torsion vibrations simultaneously. For the design of the controller, identiÿcation parameters resulting from the forced vibration test of the building are adopted. The target of the controller performance is to reduce the vibration of ÿrst mode and to keep robust stabilization over the second or higher mode. From the results of forced vibration tests conducted after installation of the controller, it was conÿrmed that this system has proven control e ect, largely satisfying what was aimed for in the design. Furthermore, system performance has been continually recorded during earthquakes, and analysis of the data has proved control e ect.
Vibration of long‐span bridges can be caused by various types of dynamic excitation, wind‐induced vibration may be the most critical for long‐span bridges such as suspension bridges and cable‐stayed bridges. Typical example are pylons, and wind induced vibration of these during erection affects the safety serviceability of the structure. Formerly, sliding‐block dampers using wires were installed to reduce wind‐induced vibration of pylons, but these had the defects of requiring large space for installation, and there were difficulties with evaluation of damping effects. For the past 15 years, passive‐type tuned mass dampers or tuned liquid dampers have become popular in Japan, but as natural frequencies of pylons vary widely according to the height of pylons during erection, several sets of mass dampers of different natural frequencies have to be prepared. To overcome these drawbacks of passive type mass dampers, actively controlled mass dampers have been developed to reduce the vibration of various modes of structures. The pylons of the Rainbow Suspension Bridge in Tokyo incorporated the first application of the active control system in the world in 1991. The results of active control were found to be very effective, and its technologies have already been applied to more than 10 pylons of long‐span bridges in Japan. This paper reviews progress in the application of active vibration control technologies to long‐span bridges in Japan.
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