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Feedrate scheduling with kinematic constraints is a challenging problem for five-axis machining. Linear and rotary drives of five-axis machine tools have different capabilities and limits. The main issue is that the feedrate profile generated by the existing five-axis feedrate scheduling method might violate kinematic constraints since the tangential and axial jerk could not be directly correlated due to nonlinear kinematics transformation. In this paper, a novel master-based feedrate scheduling (MBFS) approach with real-time and drive constraints is developed to generate smooth trajectories along five-axis linear toolpaths. Based on inverse kinematic equations, tooltip feed parameters are evaluated by a five-axis feed regulation formula (FFRF) such that axial velocities, accelerations, and jerks could be constrained within given limits simultaneously. The tooltip or rotary axis having the largest motion duration is selected to be the master, and the others are regarded as the slaves which move with the master synchronously. Rather than planning the feedrate profile using the curve parameter algorithm, linear and angular trajectories are planned by matching the same motion duration to realize time synchronization of five-axis motion. The local corner smoothing method is adopted to blend the velocities of the motion axes and generate cornering trajectories while satisfying corner position tolerance and drive constraints. Finally, experiments are conducted on a five-axis engraving machine to verify that the proposed method can satisfy the kinematic constraints, and improve tracking and contour accuracy. [ABSTRACT FROM AUTHOR]

In this study, we developed a bending moment model that considers the cutting forces acting on a sensory tool holder along the rotational direction. The polar plot of the bending moment during cutting can be used to investigate the cutting behavior. Cutting processes with different cutting depths and widths result in different polar plots, as verified experimentally. To evaluate the effect of tool wear on the polar plot, the bending moment equations were modified to incorporate the developed tool wear model. The simulation results indicated that tool wear can increase the size of the polar plot and vary the angle of the plot. By examining the change of this angle, one can determine the level of tool wear. The experimental results of this study indicated that the derived equation can predict the tool wear behavior with an average accuracy of 84%. Thus, the proposed integrated model enables the accurate prediction of tool wear. Consequently, the polar plot can feasibly be used to detect the level of tool wear. [ABSTRACT FROM AUTHOR]

Flank wear is the most common wear that happens in the end milling process. However, the process of detecting the flank wear is cumbersome. To achieve comprehensively automatic detecting the flank wear area of the spiral end milling cutter, this study proposed a novel flank wear detection method of combining the template matching and deep learning techniques to expand the curved surface images into panorama images, which is more available to detect the flank wear areas without choosing a specific position of cutting tool image. You Only Look Once v4 model was employed to automatically detect the range of cutting tips. Then, popular segmentation models, namely, U-Net, Segnet and Autoencoder were used to extract the areas of the tool flank wear. To evaluate the segmenting performance among these models, U-Net model obtained the best maximum dice coefficient score with 0.93. Moreover, the predicting wear areas of the U-Net model is presented in the trend figure, which can determine the times of the tool change depend on the curve of the tool wear. Overall, the experiments have shown that the proposed methods can effectively extract the tool wear regions of the spiral cutting tool. With the developed system, users can obtain detailed information about the cutting tool before being worn severely to change the cutting tools in advance. [ABSTRACT FROM AUTHOR]

This paper presents an integrated servo-feed-drive model including the cutting force and structural effect to predict tracking errors in an end-milling process. Most conventional approaches consider the cutting force to be an equivalent torque to servo feed drive. However, in addition to acting as the equivalent torque to the servo feed drive, cutting forces also cause the machine table to vibrate. This paper considers the aforementioned cutting-force effects to predict tracking errors and then verifies the tracking errors using experimental results. Experiments are conducted on a 3-axis computer numerical control (CNC) machining center to validate the tracking errors predicted by the proposed servo-feed-drive model. For one case study, the peak-to-peak tracking errors from the experimental, proposed, and traditional models are 3 μm, 2.8 μm, and 0.5 μm, respectively, for the x-axis, and 2.1 μm, 1.7 μm, and 0.4 μm, respectively, for the y-axis. The experimental results illustrate that the tracking errors predicted using the proposed model are more accurate than those predicted using the traditional model without consideration of the transmission path. Therefore, it can be concluded that the proposed integrated model provides much accurate tracking-error prediction, and thus, the ball-screw and machine-table flexibilities should be considered. [ABSTRACT FROM AUTHOR]

In this paper, a tool center point (TCP) feedrate scheduling algorithm for 5-axis machine tool is developed to generate the axes interpolation commands. The proposed algorithm considers not only the constraints of TCP velocity, acceleration and jerk, but also the velocity differences of each axes at the junction of each block. First, the proposed method determines the maximum speed for each block segment at the TCP coordinate based on the computed length. Then the kinematics of the five axis machine tool is employed to derive the five-axis corner velocity difference (FCVD) formulation. The FCVD utilizes the axis velocity difference at the junction of blocks as the designed variable. As the starting and end velocities of each block are determined, the S-shape acceleration/deceleration (Acc/Dec) method is adopted to generate both smooth TCP and rotary axis profile based on the given interpolation parameters. The servo dynamics of the five axis machine tool are utilized to evaluate the performances of the FCVD. Simulation results demonstrate that the FCVD can achieve better contour accuracy with less machining time as compared to the five-axis feedrate regulation formulation (FFRF) algorithm. Furthermore, the FCVD are compared with Heidenhain CNC controller and the results show that the FCVD has similar behaviors as the Heidenhain controller, but it can achieve less machining time. [ABSTRACT FROM AUTHOR]

In this paper, an integrated dynamic acceleration/deceleration (IDAD) interpolation algorithm which combines the acceleration/deceleration before interpolation (ADBI) and acceleration/deceleration after interpolation (ADAI) is proposed. The IDAD scheme could confine the maximum contour error at the junction of a linear line (G01) block under consideration of the command and servo dynamic errors. The contour error formulation for the IDAD is derived analytically and then utilized for interpolation design. Because the error formulation could predict the command and dynamic errors analytically, the IDAD could adjust the connecting velocity of two blocks such that the overall contour errors are bounded within the given tolerance. The simulation results validate the proposed algorithm that can reduce the contour errors by 50 % but only an increase of 10 % machining time as compared to the integrated acceleration/deceleration (IAD) interpolation technique. [ABSTRACT FROM AUTHOR]

Modern motion control adopts acceleration/deceleration before interpolation (ADBI) motion planning to eliminate path command errors. However, the individual velocity profiles might not be continuous at the junction of the blocks. Acceleration/deceleration after interpolation (ADAI) method may provide an alternative for solving the discontinuous problems, but it causes path command errors. In this paper, an integrated acceleration/deceleration interpolation (IAD) scheme which integrates the ADBI and ADAI modules is proposed. The ADBI provides a look-ahead function which plans the feedrate profiles based on chord errors, command errors, curvatures, and acceleration limits. Within the look-ahead function, the command error equation is utilized to determine the feedrate at the junction of adjacent blocks. Then the ADBI performs non-uniform rational B-spline (NURBS) interpolation using the planned feedrate profile and outputs the position points to the ADAI module. The ADAI module processes the points by a digital convolution technique such that the continuity of the block junction velocity is ensured. Finally, the IAD is applied to the multi-block NURBS interpolation to validate its effectiveness. Simulations and experiments are conducted to demonstrate the IAD scheme. It is shown that the IAD scheme can reduce the acceleration significantly at the junctions of the blocks under the given tolerance of the command error. Furthermore, the proposed algorithm can improve tracking and contour accuracies as compared to the hybrid multi-blocks look-ahead approach. [ABSTRACT FROM AUTHOR]

In this paper, a novel dynamic model is developed for analysis and control of a 3-PRS (Prismatic, Revolute, Spherical) parallel mechanism. The dynamic model is formulated in the joint space and three holonomic constraint equations are derived to specify the coupling relationships between the actuated legs and the moving platform. The associated constraint forces are determined to be internal forces and it leads to a novel model where the dynamics of the moving platform can be separated from that of the actuated legs. By utilizing the developed model, the constraint forces can be computed more efficiently as compared to the conventional approach. After compensation of the coupling dynamics, each actuated legs could be considered as a decoupled system. The coupling behavior of the parallel mechanism can then be easily illustrated by the proposed model. To facilitate real-time control implementation, the derived model can be further simplified and a decentralized control scheme integrated with a disturbance observer is proposed. The computational efficiency and tracking performances for the proposed control method are then validated by computer simulations. [ABSTRACT FROM AUTHOR]

Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-021-97610-y, published online 7 October 2021 Hong-Tsu Young was omitted from the author list in the original version of this Article. The original article can be found online at https://doi.org/10.1038/s41598-021-97610-y. [Extracted from the article]

In the accepted paper, the authors' affiliation has been wrongly typeset as People's Republic of China, but this should read Taiwan. The correct affiliations are shown below. [ABSTRACT FROM AUTHOR]