Coarse and fine positioning performance of an L-shaped seal mechanism with three degrees of freedom

This paper deals with a small mobile device, called the 'seal mechanism', with three degrees of freedom (3-DOF) for a scanning probe microscope. An L-shaped structure for the seal mechanism is proposed. This device consists of two controlled electromagnets connected by two piezoelectric actuators with an electromagnet that generates constant friction. The friction at the controlled electromagnets is alternated by an on–off control. The whole device wriggles by deforming the piezoelectric actuators. The 3-DOF device can move up to micrometre steps in the x - and y -directions and rotates up to submilliradian steps in the θ-direction. The displacements in the experiments correspond with the displacements analysed using static mechanics. The inertial force by the controlled electromagnets and their time constant restrict the cycle time. Positioning accuracy in each direction is twice as small as the resolution in the coarse mode and once in the fine mode.