In February 2003 Claverham was awarded a contract by BAE Systems to investigate Electro-Mechanical Actuation for Hydrodynamic Control Surfaces (ELAHCS). The contract scope was to design & demonstrate an electromechanical stabiliser on a Type 23 frigate. Claverham was also awarded a study / contract to investigate other potential EM opportunities as a lead into the all electric ship.

The ELAHCS Stabiliser System comprises a number of key assemblies configured for installation in the existing space envelope within a Type 23 Frigate. The major assemblies are the two electro-mechanical actuators (EMA), the electronic control unit (ECU) and motor control unit (MCU) both housed in a common enclosure together with a data logger, a single manual input device (MID) which can be fixed to either EMA and the interconnecting cable harnesses providing power feed and signal data transfer. Figure 1 shows this architecture in simplified form. The system is generally in one of two conditions; ACTIVE - when the system is in operation, and STAND-BY when the control system is powered but the motors are isolated.

The EMAs are pin-mounted actuators, designed to fit within the existing mounting frame and crosshead arrangement, see Figure 2. Each actuator comprises a single DC motor that, through a transfer spur gear train, drives into a planetary roller screw. By ‘earthing’ the roller screw nut assembly the rotational energy is transferred into linear force acting on the output rod.