Miniature linear motor accelerates to 40G
A matchbox-sized linear motor that produces an acceleration up to 40 times that of gravity has been developed by Essex-based Linear Drives. The miniature motor, based on the company`s tubular ThrustTube technology, will deliver a continuous force of 7N over its 50cm-long operating length and will position to an accuracy of 0.1µm when used with an appropriate encoder.
The Mini ThrustTube, due to be launched in September, is expected to cost less than £200 and is designed for precise positioning duties. The 100g moving element runs on a 11mm diameter magnet-containing tube, compared to the 25mm and 38mm diameter tubes used for the larger ThrustTubes. Another difference is that whereas the full-size versions operate at 320V, the miniature version will operate at 50V, thus complying with extra low-voltage safety requirements.
Linear Drives is also launching a low-cost, cartridge version of the ThrustTube aimed at OEMs. The motor weighs 25% less than the standard versions and has a smaller diameter. It dispenses with the integrated heatsink and Hall-effect sensors of the standard models and has less internal electronics.
Linear Drives claims that the patented ThrustTube technology offers several advantages over other types of linear motor. For a start, because the armature coils encircle the stator magnets, all of the coils cut all of the flux. This maximises efficiency, ensures that direct linear thrust is produced and eliminates the need for forced cooling. There are no cogging forces and no attractive forces between the components, Linear Drives asserts.
Also, because the tubular design avoids the need for precision airgaps and alignments, it is quick and easy to install. It can be used a direct, drop-in replacement for ballscrew systems. Because the ThrustTube is similar electrically to a rotary servo motor, it can be powered and controlled by standard servo drives.
Unlike other linear motors, the ThrustTube has to be supported at both ends and has a maximum length of 2m. The full-size motors are available in versions that can produce accelerations up to 16G, velocities up to 13m/s, and continuous forces up to 262N.
