Integrated steering actuation systems for torpedoes.

Typically the source of power for a long-endurance control system necessary in torpedoes such as
Spearfish is a hydraulic pump with a return oil system.

To cover essential control activity in the immediate post-launch period and prior to the run-up speed of the propulsion engine, a
stored-pressure system gives a smooth hand-over to pump-driven operation.

The following subassemblies are required:
High-pressure pack
Low-pressure pack
Ring main
Fins (with rudder and actuator)
Electronic controller.

Integrated steering actuation systems for torpedoes. (cont)

These hydraulic systems are specifically configured to suit the space envelope constraints in a torpedo tailcone. The ring main integrates the following essential components in an electrohydraulic system: pump, hoses (pressure and return) with quick-disconnect couplings, pressure and return ring-main pipes, relief valve, accumulator with gas cartridge release valve and filter, pressurised reservoir, electrohydraulic servo valves (four), rotary actuator with position feedback (four), and the control system's electronic package.

In electrohydraulic systems a pump, usually near the torpedo motor and remote from the ring main, is connected via hoses and quick-disconnect couplings. Particular attention is paid to pump noise levels and to mounting structure stiffness for maximum noise attenuation.
Quick-disconnect couplings enable a modularised torpedo to be broken down easily for servicing without draining oil from the system.
A ring main of concentric pressure and return rigid pipes links mounting pads to which are attached accumulator, reservoir, relief valve, and four electrohydraulic servo valves. These components are arranged around the propeller shaft giving an optimum use of space. A low-hysteresis relief valve limits the pressure peaks in the hydraulic system and discharges from the high- to the low-pressure ring main. An accumulator provides a back-up source during the starting period and
when actuator demands momentarily peak above the pump output flow.
On torpedo release an electrical signal actuates a frangible valve in a sealed gas bottle. This gas immediately pressurises accumulator fluid to provide hydraulic power to the actuators via the electrohydraulic valves.

A spring-loaded reservoir maintains a positive return-line pressure at all times and absorbs fluid displacements due to accumulator discharge and fluid expansion.
Four two-stage electrohydraulic servo valves mounted on the ring main control four rotary actuators. Each valve receives an electrical signal from the torpedo guidance system via an electronic control loop-closure package.
Four rotary actuators directly coupled to the control rudders are fitted in the fins. The actuator/control rudder position is monitored through a mechanically linked rotary potentiometer which provides the position feedback signal to the electronics package. The fins are individually attached to the torpedo tailcone.
Test sets are provided to put the four-axis control system through its paces by injecting various electrical demand input signals, including steady-state, sinusoidal and other forms. Hydraulic power is used to energise the ring main of the control system under test; an electronic section simulates the torpedo control. A microprocessor is programmed to take each control system through the complete test routine.