The direct drive (DD) actuator is a high-torque and low-speed electric motor which can drive a mechanism without a speed reducer. It can eliminate unfavorable effects of non-linear backlash and low stiffness of gears, thus it accomplishes high precision, high speed, and reliable positioning. The two different types of direct drive motors, linear and rotary, work in similar ways. Rotary direct drive motors operate using magnets, these are attached to the rotor and the windings which are on the stator of the motor.
A direct drive transmits motion to a system or object requiring actuation without the use of any further mechanical components. Direct drive motors are commonly used in the medical, aerospace, defense and industrial sectors. One of the most frequent applications is for use in gimbals in antennas and satellites, due to the reliability and dynamic motion created by direct drive engines. Direct drive motors offer significant design advantages over traditional motors. As they consist of just two parts – the stator and rotor, they can be engineered to fit into many different compact forms. Also, without the need for a controller, the direct drive can afford more space around the motor itself.
With an overall efficiency level of 98 percent, direct drives are extremely energy-efficient and very maintenance-friendly. Direct-drive motors usually have many poles—more than 30 and sometimes more than 100. This lets them output high torque at no or low speed, usually slower than 1,000 rpm. The first direct-drive turntable was invented by Shuichi Obata, an engineer at Matsushita (now Panasonic), based in Osaka, Japan. It eliminated belts, and instead employed a motor to directly drive a platter on which a vinyl record rests.
