Aravind Kailas

Operational Concepts for Truck Maneuvers with Cooperative Adaptive Cruise Control

Cooperative adaptive cruise control (CACC) has been loosely defined in recent literature to represent a wide variety of vehicle-following control concepts, and when trucks are discussed, CACC is often used synonymously with platooning. This paper discusses the similarities and differences between CACC and platooning and provides a more precise functional description of CACC operations for trucks. CACC operations include not only the steady state cruising mode but also the maneuvers needed to join vehicles together and separate them when a vehicle needs to leave a CACC string or when the string is interrupted by a cut-in maneuver by a noncooperative vehicle. Activity diagrams are used to describe the CACC maneuvers; the diagrams specify the sequence of actions that need to be taken by each driver and each vehicle (and its CACC software) and the information that needs to be exchanged between them. These precise definitions can be used to specify the vehicle-to-vehicle messages that need to be exchanged between vehicles to implement CACC and the driver–vehicle interface displays and controls that are needed. The paper also addresses practical considerations in CACC operation, such as maximum lengths for strings of CACC trucks, strategies for sequencing the trucks in CACC strings, and higher-level strategies for clustering CACC-capable trucks; these strategies range from ad hoc to local and global coordination.

Influences on Energy Savings of Heavy Trucks Using Cooperative Adaptive Cruise Control

An integrated adaptive cruise control (ACC) and cooperative ACC (CACC) was implemented and tested on three heavy-duty tractor-trailer trucks on a closed test track. The first truck was always in ACC mode, and the followers were in CACC mode using wireless vehicle-vehicle communication to augment their radar sensor data to enable safe and accurate vehicle following at short gaps. The fuel consumption for each truck in the CACC string was measured using the SAE J1321 procedure while travelling at 65 mph and loaded to a gross weight of 65,000 lb, demonstrating the effects of: inter-vehicle gaps (ranging from 3.0 s or 87 m to 0.14 s or 4 m, covering a much wider range than previously reported tests), cut-in and cut-out maneuvers by other vehicles, speed variations, the use of mismatched vehicles (standard trailers mixed with aerodynamic trailers with boat tails and side skirts), and the presence of a passenger vehicle ahead of the platoon. The results showed that energy savings generally increased in a non-linear fashion as the gap was reduced. The middle truck saved the most fuel at gaps shorter than 12 m and the trailing truck saved the most at longer gaps, while lead truck saved the least at all gaps. The cut-in and cut-out maneuvers had only a marginal effect on fuel consumption even when repeated every two miles. The presence of passenger-vehicle traffic had a measurable impact. The fuel-consumption savings on the curves was less than on the straight sections.

On Augmenting Adaptive Cruise Control Systems with Vehicular Communication for Smoother Automated Following

This paper focuses on evaluating, in a structured manner, the potential benefits, along with the implementation and performance issues, of utilizing dedicated short range communication-based communication in conjunction with adaptive cruise control (ACC) systems. This work was done in the United States under a cooperative agreement between the Crash Avoidance Metrics Partners LLC and the Federal Highway Administration. Designing cooperative adaptive cruise control (CACC) as an extension of ACC, and by using a combination of a comprehensive simulation framework and test vehicles, benefits of vehicular communication on string stability were established, and the performance of the novel CACC-enabling software modules were validated. Another key contribution of this work is the consideration of vehicles with different dynamic responses as a part of a single string. Four light-duty vehicles (hatchback, mid- and full-size sedans, large SUV), each from a different automotive original equipment manufacturer, were retrofitted with common ACC and vehicular communication systems. They were tested under many different conditions to obtain performance data (such as radar sensor readings, etc.) when operating in a vehicle string. These data were then integrated into the simulation environment to develop and validate the CACC modules. The paper concludes with a recommendation of some data elements for over-the-air messages to enable CACC functionality.

A First Investigation of Truck Drivers’ Preferences and Behaviors using a Prototype Cooperative Adaptive Cruise Control System

Cooperative adaptive cruise control (CACC) is a driver-assist technology that uses vehicle-to-vehicle wireless communication to realize faster braking responses in following vehicles and shorter headways compared with adaptive cruise control. This technology not only enhances road safety, but also offers fuel savings benefits as a result of reduced aerodynamic drag. The amount of fuel savings is dictated by the following distances and the driving speeds. So, the overarching goal of this work is to explore driving preferences and behaviors when following in “CACC mode,” an area that remains largely unexplored. While in CACC mode, the brake and throttle actions are automated. A human factors study was conducted to investigate truck drivers’ experiences and performance using CACC at shorter-than-normal vehicle following time gaps. “On-the-road” experiments were conducted by recruiting drivers from commercial fleets to operate the second and third trucks in a three-truck CACC string. The driving route spanned 160 miles on freeways in Northern California and five different time gaps between 0.6 and 1.8 seconds were tested. Factors such as cut-ins by other vehicles, road grades, and traffic conditions were found to influence the drivers’ opinions about use of CACC. The findings presented in this paper provide insights into the factors that will influence driver reactions to the deployment of CACC in their truck fleets.

Development of a Duty Cycle for the Design and Optimization of Advanced, Heavy-Duty Port Drayage Trucks

Hybrid electric and electric trucks are potential technology solutions for reducing emissions at ports. However, developing an advanced, low-emission technology driveline entails thoroughly understanding typical truck operations in the real-world environment. This paper presents the work performed to develop a novel, more representative drayage duty cycle that characterizes drayage truck operations in the ports of San Pedro Bay in California. Unlike a conventional vehicle, an optimized hybrid driveline requires detailed understanding not only of torque requirements and vehicle speeds but also of the potential recovery of dynamic brake energy, charging opportunities, stopping and idling times, and many other operational requirements. Keeping this in mind, the duty cycle presented in this paper incorporated real-world, near-dock activities of Class 8 drayage trucks such as daily hours of operation, mileage, altitude profiles of routes, and idling and key-off patterns. The empirical duty cycle model was subsequently integrated with a complete vehicle simulation to explore the best solutions to minimize energy consumption for drayage applications in and around the ports. The analysis presented indicates that trucks spent most of the generated power in overcoming aerodynamic drag and rolling resistance of tires for a complete drayage shift and that electrical auxiliary loads dominated for near-dock operations because of idling and low-speed profiles. Therefore, achieving zero-emission near-dock operations entails focusing on auxiliary loads and rolling resistance. By using simulations, it was estimated that a hybrid truck with electrical power limited to about 100 kW could deliver a greenhouse gas emission reduction of about 30%.