U-Series linear actuation product

The U-Series from Ultra Motion is a family of pressure-compensated, oil-filled electromechanical linear actuators for subsea use. The actuator is rated for operation to depths of 20,000 feet (6,000 meters), which corresponds to 10,000 psi, and it is used on uncrewed underwater and surface vehicles that need compact, reliable linear actuation in a flooded environment.

The internal design is oil-filled with a built-in compensator, so the internal pressure follows the ambient pressure and the housing does not need to resist a large pressure difference. This gives a small footprint for the force delivered. The drive is electromechanical (EMA): the motor options are NEMA 17 (U1) and NEMA 23 (U2) stepper motors or brushless DC motors, and the screw options are a self-locking Acme leadscrew or a high-efficiency ballscrew. In-line planetary gearheads are offered for the brushless versions where high force at low speed is wanted.

Performance figures are a peak force of up to 500 lbf and a peak speed of up to 5 in/s. Standard strokes are 2, 4, 6 and 8 inches, and strokes from 1 to 16 inches are available. Nominal axial backlash is 0.005 inch. The actuator is rated for a mechanical maximum load of 500 lbf, and the force-versus-speed curves give the continuous capability in air. The operating temperature range in air is -40 C to +60 C.

Every U-Series actuator has a built-in linear potentiometer that provides absolute position feedback. The stepper versions are wired in parallel by default and need an external controller able to supply at least 1.7 A rms per phase for the U1 and 4.2 A rms per phase for the U2. The brushless versions include Hall sensors for commutation and need external drive electronics. Because the control electronics are not built in, the choice of controller and its communication interface belongs to the system design. SubConn wet-mate connectors are standard, and custom cable lengths and outputs are available.

Stepper versions suit positioning that needs high resolution and high force at low speed with simple operation. Brushless versions give higher dynamic capability over a wider speed range and closed-loop commutation, so they suit control surfaces and loads that can reach large peak hydrodynamic forces, where an open-loop stepper could lose synchronisation.

Typical applications are the operation of hydroplanes on subsea vehicles, the deployment of instruments such as float releases and sensors, the raising of masts and antennas on unmanned surface vessels, the control of hydrofoils and rudders, and the actuation of subsea valves.