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DIRECT DRIVE DUAL AXIS POSITIONERS

These positioners make use of direct drive actuators. M-TEK has developed several elevation over azimuth direct-drive positioners and related control electronics, usually for radar and/or optronic tracking applications. Direct-drive motors are used to achieve high accuracy, fast dynamics and low friction. Dual-speed resolvers are used to accurately measure base-relative angles. Fibre-optic rate gyroscopes are used for sightline stabilisation.

One example is the positioner used for a naval Optronics/ tracker, which produces over 1000 Nm in azimuth and 500 Nm in elevation, in order to provide rapid large-angle slews and search patterns used by the radar. Tell-back accuracy is 0.25 mRad, and tracking accuracy normally better than 1 mrad. The control electronics includes DSP-based servo-amplifiers for the three-phase brushless motors, a power supply and a VME-based controller (using an off-the shelf CPU card and custom M-TEK I/O cards). The controller includes serial links to control the Customer-furnished optronics payloads (two thermal imagers, a laser rangefinder), receive data from the fibre-optic rate gyro, control the servos, read on-gimbal angles, and receive commands from the Radar Signal Processor.

A smaller system (100 Nm peak torque) has also been developed for an optronics tracker (with Customer-furnished daylight video camera, thermal imager, and laser rangefinder).

Both of the above systems are inertially stabilised using fibre-optic rate gyroscopes.