Energy Flow in Active Attitude Control Suspensions: A Bond Graph Analysis

Fully active ground vehicle suspensions which completely replace the passive spring and damper elements with a force generating actuator have required a significant amount of power. Alternative systems which retain compliant elements to handle high frequency isolation but include active elements to control the vehicle body attitude have been developed to reduce the power requirements. These suspensions are called “low bandwidth” or “fast load leveler” systems and they often incorporate semi-active dampers which produce high frequency controllable forces with low power requirements. Here, two contrasting attitude control systems are studied to show that actuator power can be significantly reduced if the actuator is used to vary a lever ratio instead of being used to compress the suspension spring directly. Both types of systems have been successfully implemented in prototype form. Bond graphs for idealized versions of the suspensions show clearly the significant differences in actuator power and energy requirements even though the abstract mathematical structures of the two systems are remarkably similar. Computer simulations confirm the analytical results.     

Effects of Model Complexity on the Performance of Automated Vehicle Steering Controllers: Model Development, Validation and Comparison

Recent research on autonomous highway vehicles has begun to focus on lateral control strategies. The initial work has focused on vehicle control during low-g maneuvers at constant vehicle speed, typical of lane merging and normal highway driving. In this paper, and its companion paper, to follow, the lateral control of vehicles during high-g emergency maneuvers is addressed. Models of the vehicle dynamics are developed, showing the accuracy of the different models under low and high-g conditions. Specifically, body roll, tire and drive-train dynamics, tire force saturation, and tire side force lag are shown to be important effects to include in models for emergency maneuvers. Current controllers, designed for low-g maneuvers only, neglect these effects. The follow on paper demonstrates the performance of lateral controllers during high-g lateral emergency maneuvers using these vehicle models.     

Comparison of In-Vehicle Auditory Public Traffic Information With Roadside Dynamic Message Signs

Dynamic message signs (DMS) have been widely used by transportation agencies to disseminate traffic information (referred to in this article as “public traffic information”) for decades. Unfortunately, their effectiveness is limited, based on the following reasons: they are costly, can only present a limited amount of information, and typically only display information in one language. The wide availability of smart devices and the development of connected vehicles offer the possibility to create “virtual” DMS (VDMS), utilizing geofencing and audible messages to convey public traffic information. This research compares the ability of VDMS to convey public traffic information with existing DMS. A mixed repeated-measure experiment using a driving simulator was designed that examined the impacts of driver age, information transmission mode, amount of information, and driving complexity on message comprehension. Forty-two participants were recruited and each of them was tested under different combinations of the three within-subject factors. Participant performance was measured in terms of message comprehension, distraction, and self-reported overall difficulty level in receiving messages. Results revealed that VDMS generally performs better than DMS as information content increases and driving condition complexity increases, regardless of driver age. VDMS increased message comprehension by 16% under relatively complex driving conditions, reduced driver reaction time to unexpected stimuli (as measured with a reduced time-to-brake of 0.39 s), and made the same messages easier to process and retain for drivers than DMS. Based on these results, it is recommended that transportation agencies give careful consideration to VDMS as a future strategy for delivering public traffic information in a connected vehicle environment.     

Customization of Automatic Incident Detection Algorithms for Signalized Urban Arterials

Non-recurrent congestion or incidents are detrimental to the operability and efficiency of busy urban transport networks. There exist multiple automatic incident detection algorithms (AIDAs) to remotely detect the occurrence of an incident in highway or freeway scenarios; however, very little research has been performed to automatically detect incidents in signalized urban arterials. This limited research attention has mostly been focused on developing new urban arterial specific algorithms, rather than identifying alternative methods to synthesize existing freeway-based algorithms for urban conditions. The main hindrance to such synthesis is that the traffic patterns on the signalized urban arterials are significantly different from the same on highways/freeways due to the presence of traffic intersections. This article introduces a new strategy of customizing the existing AIDAs (freeway based or otherwise) to significantly improve their adaptability to signalized urban arterial transport networks. The new strategy focuses on preprocessing the traffic information before being used as input to a freeway/highway-based AIDA to lessen the effect of traffic signals and to imitate the input patterns in highway/freeway-based incident conditions. The effectiveness of this new strategy has been established with the help of four existing AIDAs. The proposed strategy is a simple solution to implement existing algorithms to signalized urban networks without any further instrumentation or operational cost.