An Electrical Alternative to Fluid Power Systems

Because electrical power is often used to create the fluid power in fluid systems, Exlar engineers thought it logical to find an actuation method that relied exclusively on electric power. Such an approach would eliminate the conversion of electrical power to fluid power first and then to mechanical motion. For a linear motion solution, however, it can be difficult to find electric counterparts with similar form factor and size and that exhibit robustness and long life.

After considerable examination, Exlar engineers turned to roller screws for a better actuation product, and developed the integrated actuator. It uses a brushless servomotor with a cylindrically shaped armature with an inside thread. The design embeds a rotary-to-linear converter within the confines of the rotating armature of a conventional servomotor by turning a conventional screw configuration “inside-out.” An output rod with external threads that match the internal threads of a rotating cylinder would extend or retract (if kept from turning) as the armature rotates. This design yields a compact device and eliminates the requirements for connecting components between the servomotor and a separate rotary-to-linear converter device or screw actuator. This actuator produces an electric equivalent to hydraulic actuation and makes a linear actuator electronically controllable.

To reduce size and weight, the engineers developed a segmented lamination motor design. The resulting T-LAM motor, with its higher slot fill, minimal end turns, and improved heat transmission characteristics increased the available continuous force capabilities of the actuator by 30-50%. These actuators can provide up to 50% more thrust in the same size package and operate much cooler.