Comparing the Performance of Different Heavy Duty Platooning Control Strategies

Platooning is a promising technology which can mitigate greenhouse gas impacts and reduce transportation energy consumption. Platooning is a coordinated driving strategy where trucks align themselves in order to realize aerodynamic benefits to reduce required motive force. The aerodynamic benefit is seen as either a “pull” effect experienced by the following vehicles or a “push” effect experienced by the leader. The energy savings magnitude increases nonlinearly as headway (following distance) is reduced [1]. In efforts to maximize energy savings, cooperative adaptive cruise control (CACC) is utilized to maintain relatively short headways. However, when platooning is attempted in the real world, small transient accelerations caused by imperfect control result in observed energy savings being less than expected values.

This study analyzes the performance of a recently developed nonlinear model predictive control (NMPC) platooning strategy over challenging terrain. The NMPC strategy is compared to the previous proportional-integral-derivative (PID) control scheme in terms of headway, commanded torque, and fuel rate variances along with the total fuel consumed per lap. These comparisons reveal that the NMPC based controller’s ability to optimize headway variation while considering upcoming grade disturbances reduces the harshness of commanded torque and fuel rate transients. These platoon behavior changes result in significant fuel energy consumption reductions. In all platooning configurations analyzed, the NMPC strategy consumed less fuel than the comparable PID based data. This is best exemplified by findings from platoons with increased headway spacing. When compared to PID platoon control, the NMPC produced 25.5% and 31.6% fuel consumption decreases for the final truck in four-truck platoon configurations when targeting 50 foot and 100 foot follow distances, respectively. These results suggest that the NMPC implementation minimizes extraneous acceleration events associated with rigid PID headway adherence.