To rotate a rotary body at a constant velocity, a swing control device of an electric rotary excavator controls rotation of the rotary body with a small first torque command value. By contrast, when operating a swing lever for acceleration, the rotation is controlled with a larger second torque command...http://www.google.com.au/patents/US7772792?utm_source=gb-gplus-sharePatent US7772792 - Rotation control device
