Sealed linear actuators for underwater drones

THE SOLUTION PROVIDED BY LF TECHNOLOGIES

Our client is a specialist manufacturer of underwater drones.

Main functions

Objective

Design a waterproof and autonomous system to activate the control surfaces of underwater drones.

PROBLEMATIC ISSUES

Our customer requires a waterproof system to operate the control surfaces of its underwater drones.
The actuators must provide a positional servo control, the setpoint of which will be sent by an external computer, and send back to the computer the actual position measurement as well as their operating status. These actuators must operate under prolonged immersion in salt or fresh water to a maximum depth of 100m and operate in all positions. Each assembly: “motor, servo card and sensor” is independent.

SOLUTION AND RESULT

To meet this demand, LF technologies has designed ultra-compact, high performance electric linear actuators. The linear actuators consist of an in-line component assembly contained in a 316L stainless steel tubular body. A stainless steel rod, with Cavidur coating, is guided into the front bushing containing the seal (double seal).
This spindle is hollow and ends in a ball nut system, with the ball screw housed inside when the spindle is retracted, allowing for compactness.
The movement is given by a ball screw, driven by a high performance brushless motor. This system and its control electronics allow precise and repeatable positioning and speed. These actuators provide both compression and traction movement.
The motor is controlled by an ultra-compact, high-efficiency inverter. Position control is provided by an analogue setpoint or via a serial link. The power supply is provided by a DC source of 60 to 150 V.
Position and force feedback (current image) is provided by a serial link. A special cable with a watertight connection provides the link with the power supply and control system.

Technical specifications :

• Maximum force: 1150N
• Maximum speed: 100mm/s (depending on supply voltage)
• Positional accuracy: 0.1mm
• Length (stem retracted): 330mm
• External Ø: 53mm
• Air weight: 2.2kg
• Maximum immersion depth: 100m (10bars)
• Maximum power consumption: 200W
• Power supply: 48 to 150 Vdc
• Relative position measurement
• Position and speed control
• Communication via CAN bus and RS232

Specificities:

• Type : electric
• Technology: ball screw, brushless motor
• Other features: waterproof, compact, high precision and rigidity, low power consumption
• Applications: rudder actuator for submarines, valve actuator for submarine ballast tanks, actuator on Rov arm