Metrology device and a method for compensating for bearing runout error
First Claim
1. A method of determining an angular rotation position of a metrology device, the method comprising:
- providing an encoder coupled to at least one bearing, the encoder having at least a first read head and a second read head, the encoder configured to measure in operation an angular rotation of the at least one bearing;
rotating the at least one bearing for a predetermined number of rotations;
generating a first signal with the first read head and a second signal with the second read head in response to the rotation of the at least one bearing;
defining a first waveform by subtracting the first signal from the second signal;
perform a Fourier analysis on the first waveform to define a series of sinusoidal waves for the predetermined number of rotations;
generating with a processor circuit operably coupled to the metrology device a transfer function of bearing runout based on the series of sinusoidal waves as a function of absolute angular position of the at least one bearing; and
storing, in a memory of the processor circuit, the first waveform and the transfer function.
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Accused Products
Abstract
A system and method for determining the angular position of a bearing assembly and compensating measurements for bearing runout error in metrology devices, such as an articulated arm coordinate measurement device and a laser tracker, is provided. The system and method includes measuring the bearing runout error and defining a waveform from encoder readings for a first set of rotations. In one embodiment, a transfer function is created based on an analysis of the bearing runout error, such as with a Fourier analysis for example. In another embodiment the bearing runout error is mapped to an absolute angular position. During operation, the angular position of the bearing assembly is determined by comparing a waveform to the waveform from the first set of rotations. With the angular position determined, the bearing runout error may be used to compensate the measurements of the metrology device.
68 Citations
19 Claims
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1. A method of determining an angular rotation position of a metrology device, the method comprising:
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providing an encoder coupled to at least one bearing, the encoder having at least a first read head and a second read head, the encoder configured to measure in operation an angular rotation of the at least one bearing; rotating the at least one bearing for a predetermined number of rotations; generating a first signal with the first read head and a second signal with the second read head in response to the rotation of the at least one bearing; defining a first waveform by subtracting the first signal from the second signal; perform a Fourier analysis on the first waveform to define a series of sinusoidal waves for the predetermined number of rotations; generating with a processor circuit operably coupled to the metrology device a transfer function of bearing runout based on the series of sinusoidal waves as a function of absolute angular position of the at least one bearing; and storing, in a memory of the processor circuit, the first waveform and the transfer function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining an angular rotation position of a metrology device, the method comprising:
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providing the metrology device having a manually positionable articulated arm portion having opposed first end and second end, the arm portion including a plurality of connected arm segments, wherein the plurality of connected arm segments includes a first arm segment and a second arm segment, the metrology device further having a processor circuit having a memory; providing an encoder coupled to at least one bearing, the encoder and the at least one bearing configured to couple between the first arm segment and the second arm segment, the encoder having at least a first read head and a second read head, the encoder configured to measure in operation an angular rotation of the at least one bearing, wherein the encoder is configured to transmit a signal to the processor circuit; rotating the at least one bearing for a predetermined number of rotations; generating a first signal with the first read head and a second signal with the second read head in response to the rotation of the at least one bearing; defining a first waveform by subtracting the first signal from the second signal; perform a Fourier analysis on the first waveform to define a series of sinusoidal waves for the predetermined number of rotations; generate a transfer function based on the series of sinusoidal waves as a function of absolute angular position; and storing, in the memory, the first waveform and the transfer function. - View Dependent Claims (11, 12, 13, 14)
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15. A method of determining an angular rotation position of a metrology device, the method comprising:
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providing a laser tracker having a structure configured to rotate about a first axis and a second axis, a first light source that launches a first light beam from the structure, a distance meter, and a processor circuit having memory; providing an encoder coupled to at least one bearing, the encoder and the at least one bearing configured to couple to the laser tracker and rotate the structure about the first axis, the encoder having at least a first read head and a second read head, the encoder configured to measure in operation an angular rotation of the at least one bearing, wherein the encoder is configured to transmit a signal to the processor circuit; rotating the at least one bearing for a predetermined number of rotations; generating a first signal with the first read head and a second signal with the second read head in response to the rotation of the at least one bearing; defining a first waveform by subtracting the first signal from the second signal; perform a Fourier analysis on the first waveform to define a series of sinusoidal waves for the predetermined number of rotations; generate a transfer function based on the series of sinusoidal waves as a function of absolute angular position; and storing, in the memory, the first waveform and the transfer function. - View Dependent Claims (16, 17, 18, 19)
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Specification