Kyungyeol Song

Preventing Automotive Pileup Crashes in Mixed-Communication Environments

Recent news illustrates the frequent occurrence of pileup crashes on highways. A predominant reason for the occurrence of such crashes is that current vehicles (including those equipped with an automatic cruise control system) do not provide drivers with advance information of events occurring far ahead of them. The use of intervehicular communication to provide advance warnings to enhance automotive safety is therefore being actively discussed in the research community. In this paper, we investigate scenarios wherein only a subset of the vehicles in a multivehicle stream is equipped with such advance-warning capabilities. These vehicles (which are equipped with the capability to receive far-ahead information) are arbitrarily distributed among other unequipped vehicles that are capable of receiving only local near-neighbor information. It is seen that there are conditions wherein even a partial equipage of the system can be beneficial to both equipped and unequipped vehicles in a mixed-vehicle stream. We demonstrate this through both simulations and a theoretical analysis. We also developed a prototype of an advance-warning system and conducted road tests to test the concept. These road tests have demonstrated the systems performance to be satisfactory, subject to good communication links, for the class of scenarios tested.

A GPS-based slowdown warning system for automotive safety

We propose the concept of a slow-down warning system in automobiles. If a driver on a highway decelerates suddenly or progresses abnormally slowly (thereby posing a hazard to the vehicles behind him), then, with such a system, all the cars behind him are provided information of this, near simultaneously. This advance information gives the drivers additional time to react in preparation of the impending slow-down. Simulations demonstrate that this additional time is sufficient to alleviate collisions. Furthermore, it is seen that even if only a fraction of the cars in a platoon are equipped with such a system, this can still be sufficient to alleviate crashes even in the unequipped cars. A prototype of such a system has been developed and installed in a few cars, and road tests have been conducted to verify the hardware performance.

A slowdown warning system for automobiles

In this paper, we propose the concept of a slowdown warning system in automobiles. If a driver on a highway decelerates suddenly or progresses abnormally slowly (thereby posing a hazard to the vehicles behind him), then, with such a system, all the cars behind him are provided information of this, near simultaneously. This advance information gives the drivers additional time to react; in anticipation of an impending slowdown, and this helps to alleviate collisions. Furthermore, it is seen that even if only a fraction of the cars in a platoon are equipped with such a system, this can still be sufficient to alleviate crashes even in the unequipped cars. This partial equipage also has the ability to considerably weaken (and often altogether eliminate) the shock waves that would otherwise have occurred. A prototype of such a system has been developed and road tests have demonstrated the systems performance to be satisfactory.

Active structural acoustic control of a thick-walled cylindrical shell

We consider the problem of reducing the noise radiation from a thick-walled cylindrical shell by actively controlling the motion of the shells outer surface. Because the shell is very stiff, it is difficult to directly control the shell deflections. Instead, the proposed approach is to cover the shells outer surface with curved active composite panels. Each panel contains several embedded accelerometers mounted to its outer and inner surfaces, which can sense both the motion of the panel base (i.e., the outer motion of the shell) and the outer surface of the panel (i.e., the radiating surface). The accelerometers are used in both feedback and feedforward architectures, in which the accelerometer signals are used to command the panel displacement, in order to reduce the motion of the panel outer surface, reducing the radiated noise. Experimental results show that, in the best case, 10 - 30 dB of surface vibration reduction can be achieved in the frequency range of interest, which is 250 - 2000 Hz.

Study of Mobile Mixed Sensing Networks in an Automotive Context

Mixed sensing mobile networks comprise of mobile sensors that have different sensing capabilities. We look at such sensor networks in an automotive context; wherein automobiles with two levels of sensing (and consequently with two different dynamics) are ‘mixed’ among one another. The two levels of sensing considered are local, near-neighbor information sensing; and advance, far-ahead information sensing. We look for conditions governing the way the two types of sensors should be mixed (i.e., required minimum number and distribution of the far-ahead information sensing vehicles in a mixed N-vehicle string) in order to meet certain performance objectives. In this regard, two types of models are considered – microscopic models (using ODEs) governing individual vehicle behavior; and macroscopic models (using PDEs) governing average behavior of groups of vehicles. The performance objective that we address is related to the safety of the overall network, and depends on the type of model being adopted – thus in the microscopic model, the performance metric is one of achieving zero collisions, in conditions where there otherwise would have been multi-vehicle collisions; while in the macroscopic model, the metric is one of weakening the shock waves that otherwise would have existed.

New wave-number domain sensing method for active structural acoustic control

A new wavenumber domain sensing method has been developed and applied to feedback controller design for active structural acoustic control. The approach is to minimize the total acoustic power radiated form vibrating structures in the wavenumber domain. If the disturbance spectrum is given, the target wavenumbers in the supersonic domain (i.e., the radiating wavenumbers) can be determined. Then, a state-space model can be found to estimate the magnitude of the supersonic wavenumber components. Once we have a state-space model that can be used for active structural acoustic control, a modern control design paradigm can be applied to minimize the acoustic power radiated from vibrating structures. The new sensing method was numerically validated on a thick-walled cylindrical shell with 55 active composite panels mounted. It is found that the method enables us to systematically find a state-space model for wavenumber components in the supersonic region, and therefore makes it easy to design MIMO LQG controller.