Remotely-operated water cannon offered as defence against pirates

Commercial ships are to be fitted with water cannons for close defence against Somali pirates. The cannons will be operated remotely, so the pirates cannot readily shoot the operators.

Developed by UK-based electrical and mechanical engineering firm Mirage Services, and incorporating motor control technology from robotics specialist Roboteq, the water cannons can propel a jet of over 3000 litres a minutes and have a range of 50 metres. Two thumb-operated industrial joysticks control servo motors along the cannon's X and Y axes. Limit switches prevent jamming should the motor be asked to move too far.

Most commercial ships do not carry lethal weaponry for safety and legal reasons, but this of course leaves them vulnerable to modern-day pirates armed with assault rifles and RPGs. Some ships have tried to defend themselves by using fire hoses to prevent the assailants from boarding, but this exposes the crew operating the hoses to being shot at.

Mirage said that water cannon not only have much greater force than fire hoses, but they can be remotely operated from a safe location, making this repelling technique much safer for the crew. The system has been tested onboard ships and is now going into manufacture.

The project was commissioned by an international shipping company, Mirage added. It said that, as it had already done several projects using Roboteq's AX2550 motor controller, it proposed a similar solution this time too.

The operator controls for the cannon servo motors are two Apem joysticks, these use magnetic Hall effect sensors which can operate in hostile environments without wear. The X and Y motors are operated in open loop speed mode, and are simply commanded to go faster or slower based on the joystick position. The Roboteq controller's ultra low transistor resistance and the uses of synchronous rectification technique give the motors high torque, even at very slow speed, making the aiming very precise, Mirage said.

Ships equipped with these systems will soon be transiting high piracy-risk areas. “While we all hope that the cannons will never be needed, all who participated in this development will take great pride should one of these ships come under attack, and successfully repel its assailants as a result of the efforts and ingenuity put into this system,” Mirage concluded.

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