Real-time exact contour error calculation of NURBS tool path for contour control

Gong

et al. 2022

JMSE

A deep-water bolt flange automatic connection tool plays a very important role in the process of offshore oil exploitation and transportation. In the connection process, the alignment error of bolts and nuts is the key factor to ensure the connection process is successful. Using the kinematics modeling method, this paper created the alignment error model of the deep-water bolt flange automatic connection tool and analyzed the influence of manufacturing accuracy on the alignment error of bolts and nuts through computer simulation software. Based on the error matching design method, the manufacturing accuracy of parts were optimized with a part-size-based priority sequence to ensure the bolt–nut alignment error was within the allowable limits. The land tests, the pool tests and the sea test were carried out. The test results showed that the bolt and nut can be connected in the subsea environment reliably.

Section: Error Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Alignment Error Modelling, Analysis and Experiment of the Deep-Water Bolt Flange Automatic Connection Tool

Gong

et al. 2022

JMSE

“…Through estimating the response error of a single-axis servo system, the CNC contour error is decoupled and compensated by regulating each axis. In [11,12], an improved contour error estimation method is proposed, and the CCC controller is extended to arbitrary trajectories. The contour error is approximated as the projection of the tracking error onto the normal direction of the reference point.…”

Section: Introductionmentioning

confidence: 99%

A Feedrate Planning Method in CNC System Based on Servo Response Error Model

et al. 2023

Reducing servo response error and further making reduction on contour error is crucial for high-precision computer numerical control (CNC) machine tools. For a permanent magnet synchronous motor (PMSM) servo system, there is always a response lag in feedrate tracking, which would introduce response error into the machining trajectory. Therefore, it is necessary to improve the performance of feedrate planning and interpolation for trajectory path. In this paper, a novel contour error compensation strategy is proposed. Compared with the mainstream methods, the proposed method offers a simplified alternative to existing contour error estimation techniques. Through a three-closed-loop control structure of a PMSM servo system, a response error model is founded. Afterwards, an improved S-model feedrate planning method is introduced according to the servo response error compensation. This predicted error is subsequently compensated in each interpolation cycle, resulting in a reduction of contour error. Finally, simulations and experiments are performed to demonstrate that the contour error can be reduced in both the ‘∞’-shaped Non-Uniform Rational B-Spline (NURBS) curve path and the butterfly-shaped NURBS curve path using the proposed method.

Proceedings of the Institution of Mechanical Engineers, Part C:

“…5 To accurately estimate the contour error at high-curvature region, a real-time numerical algorithm of contour error calculation is proposed for machining nurbs curves. 6 By applying the second-order Taylor expansion to a point-to-curve function, Zhu et al 7 approximate the contour error of arbitrary tool paths. Taking full advantage of interpolated command position information, Yang et al 8,9 developed a generalized contour error estimation algorithm based on Jacobian function.…”

Section: Introductionmentioning

confidence: 99%

Design of a real-time three-axis controller for contour error reduction based on model predictive control

Kang

Zhao

et al. 2022

Self Cite

The machining accuracy is mainly indicated by the contour error especially in high-precision processing. Previously, scholars have proposed many controllers to reduce contour errors in real-time machining, such as the cross coupling controller and sliding mode controller. In this paper, we propose a controller based on model predictive control (MPC), and the contour error caused during path tracking can be effectively reduced by this controller. First of all, for two-dimensional (2D) and three-dimensional (3D) tool paths, their contour errors are deduced based on coordinate system transform. Second, the MPC-based controller is designed with the state-space discrete model of a machine tool. The contour error is regarded as a constraint during receding optimization. These are reasons why the presented control scheme is adapted with both bi-axis and three-axis machine tools. Furthermore, in order to improve the efficiency of receding optimization, the contour error of a 3D curve is simplified. Subsequently, the optimization problem is transformed into the standard form of quadratic programming. Finally, a 2D tool path and a 3D tool path are machined to test the proposed controller. Simulations and experiments show satisfactory results which indicate effectiveness of the proposed method.