Proportional-Derivative (PD) Controller for Heuristic Rule-based Motorway Coordinated Ramp Meters

Abstract

This study proposes a new control method for rule-based motorway coordinated ramp metering. Coordinated ramp metering makes use of the network-wide measurements and allows multiple meters to participate in the control action to prevent or delay the onset of congestion on motorways. An essential component is a controller to dynamically adjust the level of contribution to coordination of each participating meter. The new control method builds on the concept of proportional-integral-derivative (PID) controller. A comprehensive sensitivity analysis is carried out to formulate the controller structure and coefficients. The final structure takes the form of PD controller with P-term as the main controller and D-term as supplementary to accelerate response speed and to improve the control stability. The PD controller is embedded in a rule-based coordinated ramp metering strategy for performance evaluation. A simulation study demonstrates the effectiveness of the PD controller. The coordinated control improves the mainstream traffic condition by reducing 60% and 8.4% of average traffic delay time over the base case assuming no metering and the local metering control scenario, respectively. The overall traffic travel time also decreased by the coordinated control by 25.1% and 2.0% over the base case and local metering, respectively. The enhanced mainstream traffic flow is achieved by balanced utilization of local meters and on-ramp spaces.