Patent ID: 11891261
Assignee: TAIYUAN UNIVERSITY OF SCIENCE AND TECHNOLOGY
Field: Machine tools (Mechanical engineering)
Classification: CPC B  G | IPC B  G

Claim 0:
1. A method for detecting a flatness of a sheet material using a device, wherein:
the device comprise: a conveyor; a gantry; a beam; a camera unit a speed measurement unit; a vibration measurement unit; a multi-line laser for emitting laser beams; a cable carrier; a controller; and a control cabinet wherein, the conveyor is disposed beneath the gantry and comprises a plurality of pinch roll assemblies for feeding a sheet material; the beam is disposed on the gantry and comprises a first side and a second side; the camera unit is disposed on the first side of the beam and comprises at least two cameras; the speed measurement unit is disposed between the at least two cameras; the vibration measurement unit is disposed on the second side of the beam and comprises at least two distance measurement devices; the multi-line laser is disposed between the at least two distance measurement devices; the controller is connected via the cable carrier to the camera unit, the speed measurement unit, and the vibration measurement unit; and the controller is connected through a communication cable to the controller; and
the method comprises:
1. calibrating the cameras to estimate intrinsic parameters, extrinsic parameters, and lens distortion parameters;
2. calibrating a structured-light measurement system formed by each camera and the multi-line laser, and determining an equation of a laser plane in a coordinate system defined by each of the cameras;
3. starting the speed measurement unit to detect and measure a position and speed of a sheet material;
4. when the sheet material starts moving, starting the speed measurement unit, the distance measurement devices, and the multi-line laser;
5. determining a sampling frequency of each camera according to the speed of the sheet material; and collecting images taken with each camera;
6. analyzing laser beams in each image;
7. determining a fast variable value acquired by the vibration measurement unit, calculating a vibrational amplitude of each point on a centerline of each laser beam; and compensating for a first point cloud data with the vibrational amplitude, wherein the first point cloud data is a collection of points scanned by the centerline of the laser beams;
8. measuring the same position of the sheet material with all of the laser beams; obtaining a maximum distance from each camera to each point on the sheet material; regenerating a second point cloud data and storing the second point cloud data in a table;
9. constructing a sheet material model from the second point cloud data for each camera, thereby reconstructing a partial 3D flatness of the sheet material;
10. numbering the cameras from 1 to n from a leftmost camera to a rightmost camera; numbering the sheet material model created by each camera with a serial number corresponding to the camera; selecting a first sheet material model as a reference, performing a data fusion for an overlapped area between the first sheet material model and a second sheet material model; continuing the data fusion in the same manner until no sheet material model is left, thereby reconstructing a complete 3D flatness of the sheet material; and
11. calculating a deflection and a radius of curvature according to the complete 3D flatness data; transferring the deflection and the radius of curvature to the controller to provide a basis for correction of the flatness of the sheet material.