A Brushless Hall Generator DC Servomotor

The brushless dc servomotor described consists of two basic components: 1) a brushless dc motor unit featuring a permanent magnet rotor with Hall effect devices for sensing rotor position, and 2) an electronic control package. One important feature of the control package was a nonlinear operational amplifier circuit which eliminated control input deadband and supplied a negative feedback control signal derived from the back emf of the stator windings. The result was a unit with torque versus speed characteristics which very nearly approximate those of the ideal servomotor; an evenly spaced family of negatively sloped straight lines.