Picker International, Inc.

Other

Patrick M Flanagan

Dennis K Everett

Mark D Stojkov

Victor J Hrdlicka

John D Geither

The instant invention is a dynamic piezoelectric touch probe for use with coordinate measurement machines. The touch probe is characterized by five subsystems; (1) piezoelectric vibrator controlled by a self-tuning drive circuit that adjusts operating frequency and amplitude, (2) a high sensitivity, resonant accelerometer unit coupled to the piezoelectric vibrator, (3) a flexible suspension/stylus with transverse resonant frequencies tuned to the operating frequency band of the piezoelectric vibrator, (4) a digital control circuit that automatically sweeps the operating band of the piezoelectric vibrator to (a) detect the resonant frequency of the stylus/suspension, (b) set the drive signal frequency at the resonance of the stylus/suspension and (c) control the drive signal amplitude, and (5) a triaxial load cell system that is useful for detecting excessive low frequency suspension/stylus vibration, and excessive impact force during a touch event.

Piezoelectric touch probe

A system and method is disclosed for minimizing residual vibration of a radiographic system due to rapid movement of a radiographic film cassette between a park and expose position. The cassette is moved by a servo system including a servo motor which is responsive to a voltage input waveform to drive the cassette. A waveform is chosen for the voltage input such that no inpulse derivatives appear until the waveform has been diferentiated at least three times. The primary natural resonant frequency of the system is determined and noted. The duration of the selected input waveform is adjusted such that the frequency spectrum of the adjusted input waveform defines a relative null which approximately coincides with the primary resonant frequency. The amplitude of the voltage input waveform is then further adjusted as a function of the distance to be traveled by the cassette between the park and expose positions. The servo system can optionally be operated over a portion of the cassette transit in a closed loop fashion. In a mechanical embodiment, sinusoidal cassette acceleration can be effected by the use of a mechanical drive linkage coupled between a motor and the cassette, the drive linkage employing a cycloidal cam and associated cam follower to govern the profile of cassette movement.

Spot filmer cassette transport vibration suppression

A system and method is disclosed for minimizing residual vibration of a radiographic system due to rapid movement of a radiographic film cassette between a park and expose position. The cassette is moved by a servo system including a servo motor which is responsive to a voltage input waveform to drive the cassette. A waveform is chosen for the voltage input such that no impulse derivatives appear until the waveform has been differentiated at least three times. The primary natural resonant frequency of the system is determined and noted. The duration of the selected input waveform is adjusted such that the frequency spectrum of the adjusted input waveform defines a relative null which approximately coincides with the primary resonant frequency. The amplitude of the voltage input waveform is then further adjusted as a function of the distance to be traveled by the cassette between the park and expose positions. The servo system can optionally be operated over a portion of the cassette transit in a closed loop fashion. In a mechanical embodiment, sinusoidal cassette acceleration can be effected by the use of a mechanical drive linkage coupled between a motor and the cassette, the drive linkage employing a cycloidal cam and associated cam follower to govern the profile of cassette movement.

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Westlake, OH, United States of America

Patrick M Flanagan