Pivoted arm control arrangement

Apparatus for use in controlling the movement of an arm which is pivoted for movement in first and second orthogonal planes including means to generate a first electrical signal related to a movement of the arm in one direction in the first plane, a first motor arranged to move the arm in a direction opposite to the one direction, control means, an input of the control means being coupled to the said first signal and an output of the control means being coupled to the first motor and arranged to cause a force tending to counter movement of the arm in the one direction to be applied to the arm in accordance with the first signal, the first motor comprising a magnet attached to the arm for movement about orthogonal axes, the pivot axis of the arm and the magnet for movement thereof in the first plane being coincident and passing through the motor, and the pivot axis of the arm and of the motor for movement thereof in the second plane being coincident and passing through the motor and the first-mentioned axis at right angles thereto, stabilizing magnet pole pieces arranged one on each side of the magnet with their fields arranged to oppose the movement of the said magnet in the first direction and in a direction opposite to the first direction and a coil to which the output from the control means is coupled arranged to modify the said opposing fields according to a signal applied thereto.