A. Hegyi, B. De Schutter, and J. Hellendoorn, "Optimal coordination of variable speed limits to suppress shock waves - Addendum," Tech. rep. CSE02-015a, Control Systems Engineering, Fac. of Information Technology and Systems, Delft University of Technology, Delft, The Netherlands, 4 pp., Mar. 2003.
The purpose of this document is to give a more detailed explanation of the performance degradation as described in the paper "Optimal coordination of variable speed limits to suppress shock waves" (by A. Hegyi, B. De Schutter, and J. Hellendoorn, Transportation Research Record, no. 1852, pp. 167-174, 2004). For the simulation settings in that paper the degradation occurs for the "floor" type of rounding of the real-valued control signal (resulting from the MPC optimization), but does not occur for "round" and "ceil" types of rounding. In this document we show and explain that if the discrete-valued speed limit step size is increased, the degradation occurs in all cases, but for the floor type of rounding first.