Crankshaft shape inspection method, arithmetic unit, program, and shape inspection apparatus

A crankshaft shape inspection method, comprising:

• acquiring, by a computer processor including processing circuitry, three-dimensional point cloud data of a surface of a crankshaft by a three-dimensional shape measuring device measuring a surface shape of the crankshaft;
• generating, by the computer processor, while using the three-dimensional point cloud data, first point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a first threshold value and second point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a second threshold value that is larger than the first threshold value;
• and
• extracting, by the computer processor, based on the first point cloud data and the second point cloud data, counterweight point cloud data, which are point cloud data of a counterweight of the crankshaft, calculating a side dimension of the counterweight using the counterweight point cloud data extracted from the first point cloud data, and calculating a longitudinal position of the counterweight using the counterweight point cloud data extracted from the second point cloud data,
• wherein generating, by the computer processor, the first point cloud data and the second point cloud data comprises
• translating and rotating, by the computer processor, the three-dimensional point cloud data to make a distance between the three-dimensional point cloud data and a surface shape model of the crankshaft prepared in advance based on design specifications of the crankshaft minimum, and superposing the three-dimensional point cloud data on the surface shape model, and
• performing, by the computer processor, isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the first threshold value on the three-dimensional point cloud data superposed on the surface shape model to generate the first point cloud data, and at the same time, performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the second threshold value on the three-dimensional point cloud data superposed on the surface shape model to generate the second point cloud data.

An arithmetic unit for inspecting a shape of a crankshaft, the arithmetic unit comprising:

• a computer processor including processing circuitry programmed to perform operations comprising:
• acquire three-dimensional point cloud data of a surface of the crankshaft based on a result obtained by a three-dimensional shape measuring device measuring a surface shape of the crankshaft;
• generate, while using the three-dimensional point cloud data, first point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a first threshold value and second point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a second threshold value that is larger than the first threshold value;
• and
• extract, based on the first point cloud data and the second point cloud data, counterweight point cloud data, which are point cloud data of a counterweight of the crankshaft, calculate a side dimension of the counterweight using the counterweight point cloud data extracted from the first point cloud data, and calculate a longitudinal position of the counterweight using the counterweight point cloud data extracted from the second point cloud data,
• wherein generating the first point cloud data and the second point cloud data comprises
• generate first point cloud basic data by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the first threshold value on the three-dimensional point cloud data, and at the same time, generate second point cloud basic data by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the second threshold value on the three-dimensional point cloud data, and
• translate and rotate the first point cloud basic data and the second point cloud basic data to make distances between the first point cloud basic data and the second point cloud basic data and a surface shape model of the crankshaft prepared in advance based on design specifications of the crankshaft minimum and set the first point cloud basic data and the second point cloud basic data superposed on the surface shape model to the first point cloud data and the second point cloud data.

A crankshaft shape inspection apparatus, comprising:

• a plurality of optical three-dimensional shape measuring devices that are arranged around a rotation center axis of a crankshaft, and measure a three-dimensional shape of the crankshaft by projecting and receiving light on and from the crankshaft while relatively moving in a direction parallel to the rotation center axis of the crankshaft;
• and
• an arithmetic unit that receives measurement results obtained by a plurality of the three-dimensional shape measuring devices and executes a predetermined arithmetic operation, wherein
• at least some of the three-dimensional shape measuring devices are arranged to be inclined to make light projection directions different from each other with respect to a direction orthogonal to the rotation center axis of the crankshaft, and
• the arithmetic unit includes:
• a computer processor including processing circuitry programmed to perform operations comprising:
• acquire three-dimensional point cloud data of a surface of the crankshaft based on results obtained by the three-dimensional shape measuring devices measuring a surface shape of the crankshaft;
• generate, while using the three-dimensional point cloud data, first point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a first threshold value and second point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a second threshold value that is larger than the first threshold value;
• and
• extract, based on the first point cloud data and the second point cloud data, counterweight point cloud data, which are point cloud data of a counterweight of the crankshaft, calculate a side dimension of the counterweight using the counterweight point cloud data extracted from the first point cloud data, and calculate a longitudinal position of the counterweight using the counterweight point cloud data extracted from the second point cloud data,
• wherein generating, by the computer processor, the first point cloud data and the second point cloud data comprises
• generate, by the computer processor, first point cloud basic data by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the first threshold value on the three-dimensional point cloud data, and at the same time, generate second point cloud basic data by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the second threshold value on the three-dimensional point cloud data, and
• translate and rotate, by the computer processor, the first point cloud basic data and the second point cloud basic data to make distances between the first point cloud basic data and the second point cloud basic data and a surface shape model of the crankshaft prepared in advance based on design specifications of the crankshaft minimum and set the first point cloud basic data and the second point cloud basic data superposed on the surface shape model to the first point cloud data and the second point cloud data.

An arithmetic unit for inspecting a shape of a crankshaft, the arithmetic unit comprising:

• a computer processor including processing circuitry programmed to perform operations comprising:
• acquire three-dimensional point cloud data of a surface of the crankshaft based on a result obtained by a three-dimensional shape measuring device measuring a surface shape of the crankshaft;
• generate, while using the three-dimensional point cloud data, first point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a first threshold value and second point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a second threshold value that is larger than the first threshold value;
• and
• extract, based on the first point cloud data and the second point cloud data, counterweight point cloud data, which are point cloud data of a counterweight of the crankshaft, calculate a side dimension of the counterweight using the counterweight point cloud data extracted from the first point cloud data, and calculate a longitudinal position of the counterweight using the counterweight point cloud data extracted from the second point cloud data,
• wherein generating the first point cloud data and the second point cloud data comprises
• translate and rotate the three-dimensional point cloud data to make a distance between the three-dimensional point cloud data and a surface shape model of the crankshaft prepared in advance based on design specifications of the crankshaft minimum, and superpose the three-dimensional point cloud data on the surface shape model, and
• perform isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the first threshold value on the three-dimensional point cloud data superposed on the surface shape model to generate the first point cloud data, and at the same time, perform isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the second threshold value on the three-dimensional point cloud data superposed on the surface shape model to generate the second point cloud data.

A crankshaft shape inspection apparatus, comprising:

• a plurality of optical three-dimensional shape measuring devices that are arranged around a rotation center axis of a crankshaft, and measure a three-dimensional shape of the crankshaft by projecting and receiving light on and from the crankshaft while relatively moving in a direction parallel to the rotation center axis of the crankshaft;
• and
• an arithmetic unit that receives measurement results obtained by a plurality of the three-dimensional shape measuring devices and executes a predetermined arithmetic operation, wherein
• at least some of the three-dimensional shape measuring devices are arranged to be inclined to make light projection directions different from each other with respect to a direction orthogonal to the rotation center axis of the crankshaft, and
• the arithmetic unit includes:
• a computer processor including processing circuitry programmed to perform operations comprising:
• acquire three-dimensional point cloud data of a surface of the crankshaft based on results obtained by the three-dimensional shape measuring devices measuring a surface shape of the crankshaft;
• generate, while using the three-dimensional point cloud data, first point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a first threshold value and second point cloud data based on point cloud data generated by performing isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than a second threshold value that is larger than the first threshold value;
• and
• extract, based on the first point cloud data and the second point cloud data, counterweight point cloud data, which are point cloud data of a counterweight of the crankshaft, calculate a side dimension of the counterweight using the counterweight point cloud data extracted from the first point cloud data, and calculate a longitudinal position of the counterweight using the counterweight point cloud data extracted from the second point cloud data,
• wherein generating the first point cloud data and the second point cloud data comprises
• translate and rotate the three-dimensional point cloud data to make a distance between the three-dimensional point cloud data and a surface shape model of the crankshaft prepared in advance based on design specifications of the crankshaft minimum, and superpose the three-dimensional point cloud data on the surface shape model, and
• perform isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the first threshold value on the three-dimensional point cloud data superposed on the surface shape model to generate the first point cloud data, and at the same time, perform isolated point removal processing that removes data points whose distance to the nearest neighbor data point is equal to or more than the second threshold value on the three-dimensional point cloud data superposed on the surface shape model to generate the second point cloud data.