Over the past 15 years, Foster-Miller has developed new technology under contracts from the U.S. Navy and other government agencies related to linear motor design, and magnetic levitation. Programs funded by NAVAIR  in Lakehurst, NJ, focused specifically on the problem of closed-loop arrest of aircraft by electric linear machines (EARS program). Recent work under this program has been aimed at developing electronic controls that measure motor position about 4,000 times per second and update commands. To develop a system to stop an aircraft traveling at about 150 mph over a precise braking trajectory, a demonstration subscale induction machine, about 1/8 the length of the actual carrier deck, has been designed, fabricated, controlled, and tested.

The linear induction motor design is a somewhat unusual configuration that was necessitated by the desire for an extremely high force density in the motor. An air gap winding configuration is employed. This configuration allows for very high shear pressure on the shuttle and produces relatively mild plate end effects, at the cost of a fairly poor power factor. This test system includes two 20 ft long linear induction motors. The position of each motor is measured by a linear encoder, which is then used inside a vector control scheme so that prescribed forces can be applied to the linear motor's shuttle with a relatively high bandwidth. These motors are attached to each end of a cable. A 150 lb vehicle is shot into the cable at speeds of up to 30 mph, and the system brings the vehicle to a carefully controlled stop. System development and optimization have been performed. Control and simulation work that was performed under the SBIR program has direct applicability to the Advanced Linear Motor (ALM) Advanced Technology Demonstrator. Ongoing testing with this system is evaluating the interaction of the motor control dynamics with the arresting cable dynamics in an arresting  system.

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