We consider a speed regulation problem under varying load by using an observer and cascade PI-PD controllers for this problem. This research discusses the use of disturbance-torque estimation and PD control to compensated for the disturbance torque. Disturbance-torque estimation is performed by an augmented observer followed by a torque calculator. The controller has the form of cascade feedback compensation: the inner loop PD control to compensate for the disturbance torque, and the outer loop PI control to compensate for the speed error. The purpose of this study is to quickly compensate speed error when disturbance torque substantially changes.