A Direct-Drive, Linear Actuator of a Hybrid Structure

A novel, direct drive, linear actuator suitable for sun tracking applications, heliostats, was proposed and investigated. The proposed actuator has a hybrid structure which combines a permanent magnet excited component (PEC) and a current excited component (CEC). The PEC provides the force to hold the load still when power is switched off; the CEC together with the PEC provides the drive force to move the attached load when power is switched on. First, FE models were benchmarked using actuators of simple magnetic structures, and good agreement was observed between predictions by FE models and experimental measurements. Next, 2D axisymmetric and 3D full size FE models were developed to simulate the proposed actuator. Investigation shows that, with a stator of a length of 1 m and a radius of 49.5 mm, the proposed actuator is able to move and hold still a load as high as 200 N. Replacing the ferrite magnets with neodymium magnets further improves the load carrying ability of the actuator to approximately 380 N.