Patent ID: 7359166

Claim:
A method for the safety management of a boat thruster control system, said thruster control system controlling an electric thruster motor for a thruster, said motor connected via an operating relay to a supply voltage source, said thruster control system comprising: a manually operated control means for commanding the motor to drive the thruster to selectively move the boat in a port direction or a starboard direction; said manually operated control means providing one of a first control signal or a second control signal respectively representing one of said port direction or said starboard direction; said first and said second control signals controlling said operating relay having first and second relay windings, and actuating first and second relay contacts making said motor run in a first or second direction respectively; said method comprising: monitoring a supply voltage from said supply voltage source; continuously monitoring a state of said first and second relay contacts; delaying a re-excitation of said first or second relay windings after a break if said monitored supply voltage is too low to maintain said relay in a stable pick-up state in order to avoid chattering and burning of said relay contacts; continuously comparing said control signals with signals representing the state of said first and second relay contacts to determine whether one of said first or second relay contacts is erroneously activated to run the motor either in said first or second direction; if one of said first or second relay contacts is erroneously activated, actuating the other of said first or second relay contacts to supply the same; voltage level to both terminals of the motor, thereby interrupting the current to the motor; and if the control signal indicates that only the erroneously activated relay contact should be activated, the other of relay contacts is released, thereby running the motor in the direction corresponding to the erroneously activated relay contact.