主题：Machine Tool and Robot Volumetric Error Compensation

　　主讲人：Dr. Robert G. Landers, Professor of Mechanical Engineering

　　时间：2015年6月16日下午14:30

　　地点：机电工程学院四楼会议室

　　主办单位：武汉理工大学机电工程学院

　　报告内容简介：

　　Due to inaccuracies in component fabrication and assembly, machine tools and robots have geometric errors (i.e., difference between nominal and actual kinematic motions), which greatly contribute to the errors in parts fabricated on these machines, as well as unduly long process certification times. To compensate for machine tool geometric errors, the standard practice is to directly measure each error individually using a device such as a laser interferometer or ball bar and, from these measurements, directly populate compensation tables found in the machine tool controller. The drawback to this method is that it is extremely slow and does not capture the complexity (e.g., sagging, twisting) of large machine tools. To compensate for industrial robot geometric errors, circle point analysis is used where each joint is measured independently and the Denavit-Hartenberg parameters are adjusted in the robot controller. While faster, this method still does not capture the complexity of robot kinematic errors.

　　This talk will discuss recent work on the volumetric error compensation of large machine tools (i.e., machine tools with strokes of several meters and rotary axes with travels greater than 180°) and industrial robots used for manufacturing tasks such as deburring. A laser tracker is used to measure the machine tool or robot geometric errors over the entire visible joint space. A 6 Degree of Freedom (6DoF) geometric error model is constructed for every joint. Each translational and rotational error for each joint is described by a set of joint-position dependent basis functions, in this case Chebyshev polynomials. The Implicit Loop Method, which is based on a maximum likelihood estimator, is employed to identify the coefficients of the geometric error model. Using this model, an optimization algorithm is used to populate compensation tables for machine tools, or the inverse Jacobian method is used to modify the joint commands for robots. In this talk we discuss the details of the new volumetric error compensation methodology and provide several examples of machine tools and robots we have modeled and compensated for a variety of industrial partners.

　　武汉理工大学机电工程学院

　　2015年6月3日