Pain Points & Technical Challenges
During fiber-array unit (FAU) assembly, an adhesive-coated ceramic ferrule must be pressed into a V-groove with an extremely low force of 0.8?1.2 N and force-control accuracy of ?0.05 N. Conventional voice-coil motors can provide the force, but their stroke-to-force output is nonlinear, with maximum nonlinearity up to ?3%. Significant center-position drift and temperature drift of 0.02 N/?C require weight calibration every 30 minutes, making continuous mass production impractical.
The assembly platform also requires a compact Z axis no more than 65 mm high. A conventional servo motor and precision reducer cannot be embedded because of excessive axial length. Frequent starts and stops at acceleration of at least 2.5 g generate inertial forces that couple into the force sensor and can falsely trigger overload alarms.
Yiruiju Customized Technical Solutions
Yiruiju developed a miniature linear-motor servo electric cylinder using a U-shaped ironless core and carbon-fiber frame. Its axial height is only 58 mm, with 15 mm travel, ?0.5% thrust linearity, and less than 1% thrust ripple. An integrated high-resolution analog Hall array provides 0.1 ?m position resolution. Force-control bandwidth reaches 1 kHz and closed-loop force response is within 2 ms, enabling stable output of 1 N ?0.02 N.
An acceleration feed-forward compensation algorithm reads cylinder-body acceleration in real time through a MEMS accelerometer. Compensation current is added to the forward channel to cancel dynamic force caused by 2.5 g starts and stops. Force fluctuation remains within ?0.01 N during 0.2 mm/s creep motion, eliminating false alarms caused by coupling.
Full-stroke friction identification and online compensation use an online LuGre friction model. Stick-slip caused by the Stribeck effect during static-to-dynamic friction transition is reduced by 90%, enabling sub-micron stepping for demanding optical-chip coupling and alignment. ISO Class 4 cleanliness is available for long-term unattended operation in optical-communications cleanrooms.
