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The study proposes an optimum controller design for servo position control of a drive train that incorporates a magnetic gear. Based on the integral of time multiplied by absolute error polynomials for a step response, the designed proportional plus derivative (PD) controller minimises position overshoot whereas optimising rise time. To facilitate the rejection of load-side disturbances applied to a magnetic gear, a disturbance observer is designed based on a minimum-order input-output state estimator. To compensate for load-side torsion-induced position errors, an enhanced dual observer is proposed which simultaneously compensates for non-linearity errors that result from the non-linear torque transfer characteristic of the prototype magnetic coupling used. The major advantage of the proposed optimised controller plus enhanced dual observer is that accurate set-point position tracking can be obtained using only motor-side measurements of position and velocity. This results in an optimised controller with analytically parameterised tuning, combined with computationally simple minimum-order disturbance observer and load position observer with non-linearity error correction, thereby providing accurate load-side position set-point tracking of a low dynamic stiffness drive train in the presence of torque disturbances.