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We present several new matrix inequalities which connect the Schur complement, sector matrices and weighted arithmetic mean, geometric mean and harmonic mean, extending a key result in Lin [Extension of a result of Hanynsworth and Hartfiel. Arch Math. 2015;1:93–100]. [ABSTRACT FROM AUTHOR]

A translational oscillator with a rotational actuator (TORA) is an underactuated mechanical system with two degrees of freedom. This paper presents a new method to solve the global stabilisation control problem for this underactuated system. First, a set of suitable state variables is chosen for the TORA. It transforms the system into a cascade affine nonlinear system. Then, a positive-definite Lyapunov function is constructed based on the structural characteristics of the system. A control law is designed to guarantee that the derivative of the Lyapunov function is non-positive. Finally, the global stability of the closed-loop control system is analysed using the Lasalle invariance principle. The condition on the control parameters is presented to globally stabilise the TORA at the origin. The effectiveness and robustness of the method are verified by a numerical example. [ABSTRACT FROM AUTHOR]