“…However, it is worth pointing out that Assumption 2 may be difficult to achieve in some cases, because it is usually hard to determine the unique desired input u d (i, j) for the 2-D reference trajectory. To avoid using the Assumption 2, an alternative analysis approach for ILC is to directly consider the tracking errors e k (i + 1, j + 1) and e k+1 (i + 1, j + 1) in [9] and [24]. Assumption 3: Let the reference trajectory y d,k (i, j), system parameters A 1,k (i + 1, j), A 2,k (i, j), A 3,k (i, j + 1), B k (i, j) and C k (i, j), boundary states x k (i, 0) and x k (0, j) be the progressively convergent, i.e.,…”