Injecting position dependent currents in order to reduce oscillations caused by the gearbox of a dc-motor drive

An electrical drive consisting of a pwm-fed, digital-signal-processor controlled dc-motor, of a gearbox and the load is investigated. The gearbox features a high gear transmission ratio and converts the rotation of the dc-motor into a vertical translatory movement. Due to construction insufficiencies the gearbox causes torque disturbances, which influence the vertical acceleration. The underlying idea is to compensate the torque disturbances by position dependent control of the armature current. The appropriate phases and amplitudes of the currents are calculated using the signal derived from an acceleration sensor and the extrapolated angular rotor position information. Experimental results clearly show that it is possible to reduce the oscillations by improving the control algorithm of the drive. The mechanical system acts in a sufficiently linear manner; the dc-machine's nonlinearity due to slotting has only a minor effect.