Patent ID: 7456538
Filing Date: 2008-11-25
Classification: H02K

Abstract:
1. A probe head having a reaction balanced rotary drive mechanism, the probe head comprising: a first housing part for attachment to a position determining apparatus; a first rotary drive mechanism to provide rotation of a first output shaft about a first axis, the first rotary drive mechanism comprising a first motor having a first rotor and a first stator connected to the first housing part, and a second motor having a second rotor and a second stator connected to the first housing part, the second motor being mechanically independent of the first motor and being driven in an opposite direction such that acceleration torques of the first motor are at least partially inertia balanced by the second motor; a second housing part attached to the first output shaft, the second housing part containing a second rotary drive mechanism to provide rotation of a second shaft for attachment to a surface sensing device, the second shaft being rotatable about a second axis; and a control system having a first control loop inside a position control loop, the position control loop supplying a demanded velocity to both the first control loop and a second control loop, the position control loop controlling a position of the first motor, and the second control loop controlling a speed of the second motor, whereby external forces acting on the surface sensing device are reacted into the first housing part.