Abstract: An apparatus for providing feedback control of a device having multi-degrees of freedom. The apparatus comprises a first input device for receiving control signals based upon desired reference inputs and first feedback signals from the device, a second input device for receiving second feedback signals from the device, and a processing device receiving the control signals from the first input device and the second feedback signals from the second input device for determining a compensating signal for supply to the device. The compensating signal compensating for changes in structural frequencies due to configuration changes of the device so as to enable the first feedback signals to be independent of variations of the structural frequencies.

Abstract: Apparatus for compensating for positioning, pointing and/or orientation errors caused by deflections of structural members and components of a high performance machine or device and/or for reducing vibration inputs to such machine or device and/or for micro-positioning such machine or device so as to improve the operational performance of such machine or device. The apparatus utilizes one or more active-type actuators, such as piezoelectric ceramic type actuators, which are arranged in a predetermined manner relative to the machine or device. A servo control device operating in accordance with a predetermined algorithm may be utilized for controlling the actuators or, alternatively, the apparatus may operate in an open loop manner.