A method for verifying a control system (
2) of a vessel (
4), in which said control system (
2) in its operative state receives sensor signals (
7) from sensors (
8) and command signals (
9) from command input devices (
10), and as a response provides control signals (
13) to actuators (
3) in order to maintain a desired position, velocity, course or other state of said vessel (
4), characterized by the following steps:
- during a time (t0), disconnecting the reception of real sensor signals (7a, 7b, 7c, . . . ) and replacing said real sensor signals by a test sequence (T0) of artificial measurements (7a′, 7b′, 7c′, . . . ) from a test signal source (41);
- letting said control system (2) work based on the artificial sensor signals (7, 7′) to generate control signals (13′) to be recorded as a response (S0) to said first test sequence (T0) for said first time (t0) on a control signal logger (42) and storing response (S0) to the test sequence (T0) as the control system's (2) “signature” response (S0);
said method having the purpose of, at a later time (t1, t2, t3, . . . ), to use the test sequence (T0) input to the control system (2), and record a later response (S1, S2, S3, . . . ) and determining whether said later response similar to the signature response (S0) to verify that said control system (2) is unchanged, or not.