“…In the past few years, much effort has been made on the control of first-order hyperbolic PDEs, because these PDEs can be used to model many physical phenomenons, such as chemical reactors, heat exchangers, traffic flows, and population dynamics (e.g., [1][2][3][4][5][6][7][8][9][10][11][12] and references therein). Specifically, by semigroup theory, Guo and Sun [6] and Sano [7] investigated the optimal control and the output tracking for first-order linear hyperbolic PDEs, respectively. In [8], the infinite-dimensional backstepping method was successfully extended from parabolic PDEs to first-order hyperbolic PDEs to achieve boundary stabilization, and subsequently, in [9][10][11], the case with known spatially varying parameter was solved.…”