A new non-linear multivariable control method called the QLQG/LTR method is presented, which is the integration of statistical linearization, loop-shaping and loop transfer recovery techniques. The QLQG/LTR method is a powerful one for designing controllers of non-linear systems with hard non-linearities such as Coulomb friction, backlash and saturation. In order to show the effectiveness of the QLQG/LTR method, the LQG/LTR and QLQG/LTR methods are applied to a robot manipulator with Coulomb friction. The computer simulation results show that the performance and stability robustness of the QLQG/LTR control system is insensitive to the magnitude and direction of the command input.
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