On-Ramp Decentralized Nonlinear Control with Disturbance Rejection

A method based on disturbance estimation and bounded controls is proposed to reduce congestion in highways where on-ramp metering can be implemented. An existing model is first extended to account for friction and other interactions between the mainstream and the on-ramp flows. A local variable structure observer is then proposed to estimate the lumped upstream and downstream flows that affect one section of the highway. Using the estimates of the disturbances, a local nonlinear controller stabilizes the system while maintaining the control effort bounded. The boundedness of the control effort is necessary to guarantee the feasibility of the control law. The controller is robust in the sense that the estimator accounts also for modeling errors and parameter variations.