In this paper, we study a speed tracking and load torque disturbance rejection problem of PM synchronous motor by internal model design. We first formulate the problem into a global robust output regulation problem of a special class of multivariable systems. Then we further convert the output regulation problem into a global stabilization problem of an augmented system composed of the original plant and an internal model. As the augmented system does not take any known special form, we have to develop a specific tool to deal with the stabilization problem. In particular, a generalized changing supply function technique applicable to non-ISS (input-to-state stable) systems is developed. This technique, in conjunction with a particular nonlinear internal model, leads to an effective solution to the problem.