Currently, most propeller machining adopts single-sided machining, and its vibration and deformation seriously affect the machining accuracy. To reduce the machining vibration and deformation, a dynamic, flexible support machining method is proposed, i.e., while the tool is machining, the multi-point flexible support device supports the blade and counteracts the milling force to suppress the vibration and deformation. Due to the blade’s complex shape and the support device’s special structure, the blade is divided into different areas. A support motion trajectory combining symmetric and asymmetric motions is planned, and then, a set of post-processing systems is introduced. After obtaining the tool position points, the ergodic method solves the support points cyclically. Subsequently, the support points are interpolated, and the vectors are smoothed to get smooth and continuous support trajectories. Finally, the machining parameters are calculated, and the machining data applicable to the XYZ-3RPS hybrid machine are integrated. The feasibility of the proposed support trajectory and post-processing algorithm was ultimately demonstrated through practical machining experiments. Finally, comparative experiments between supported and unsupported were conducted, and the results showed that supported machining reduced blade deformation by 35

To improve the motion accuracy of an XYZ-3RPS hybrid kinematic machine (HKM), a geometric error calibration method via binocular vision measurement is studied. First, to separately calibrate the series kinematic mechanisms (SKMs) and parallel kinematic mechanisms (PKMs), the geometric error identification equations (GEIEs) of the XYZ SKM and 3RPS PKM are derived, respectively. By analyzing the different influence principles of the geometric errors on the position and attitude of the 3RPS PKM, a constraint function is added to the GEIE of the PKM to improve the calculation accuracy. Moreover, the geometric error compensation strategy is based on the structural characteristics of the XYZ-3RPS HKM. In addition, based on the principle of binocular vision measurement, two calibration plates, called dynamic and static calibration plates, are designed as markers to define the coordinate systems, enabling the acquisition of full positions and attitudes. Furthermore, a marker transformation method and an in-situ adjustment method are designed to determine the positions and attitudes of the HKM required for calibration such that the marker is always at the center of the field of view of the camera to improve measurement accuracy. Finally, the effectiveness of the calibration method is verified through prototype experiments.

Addressing the challenge of deformation in thin-wall components due to insufficient rigidity, particularly during the machining of complex geometries, this paper draws on the digital twin framework to establish an optimization framework for dual-sided co-machining scheme. This method not only controls the milling forces on both sides to reduce deformation of the workpiece but also doubles the machining efficiency. In this paper, an overall framework with autonomous decision-making and evolutionary capabilities is introduced. Then, the practical effectiveness of the method is demonstrated through the complex task of machining propeller blades. Firstly, cutter path planning strategy and data processing method are devised. Next, in light of specific machining characteristics, implementation strategies are developed: an trial cutter path planning method based on the D-optimal design is devised using approximate periodicity to rapidly accumulate high-quality data; furthermore, a prediction function for deformation based on the neural network is developed through path relevance design. Once the prediction function is obtained, multi-objective optimization is performed to yield the most efficient machining scheme that meets the requirements for deformation. Finally, machining experiments confirm the effectiveness of this method in reducing deformation and enhancing machining efficiency.

To address the ill-conditioning of the Jacobian matrix in the geometric error calibration of parallel mechanisms, a Newton method with characteristic value correction (NMCVC) is proposed. This method integrates and enhances the principles of the characteristic value correction iteration method (CVCIM), and Newton method, offering targeted improvements for more effective calibration. First, the damping coefficient is introduced into the CVCIM, and an adaptive strategy for determining the damping coefficient is developed with rigorous proof steps according to the relationship between the condition number and the singular value, which enhances computing efficiency while avoiding the ill-conditioning of the Jacobian matrix. Second, a dynamic adjustment strategy for the CVCIM’s termination condition is designed. This strategy initially estimates the descending direction roughly to approximate the actual descending direction, enhancing computing speed, and then estimates it more accurately at the end of the training stage to obtain precise geometric error values. Finally, by taking a 3RPS parallel mechanism as the instance, three sets of simulation experiments have been designed to test and verify the effectiveness of the algorithm.

In this paper, a kinematic separation calibration method of 6R series manipulator is proposed, and its absolute accuracy is improved by a binocular camera and standard sphere. First, a geometric error mapping model for the robotic arm was established, and the error parameters were divided into position parameters and attitude parameters for calibration purposes. Second, in the process of solving error parameters using numerical algorithms, it is easy to encounter matrix ill-conditioned problems. The spectral correction iteration method is introduced to improve the calculation accuracy. Third, three standard balls are installed at the end of the robotic arm as markers, and the center coordinates are measured using a binocular camera to obtain the actual end pose parameters. To verify the effectiveness of the proposed method, a simulation model verification was designed, and the results showed that the separation calibration method was the best. Finally, the IRB-1200 robot was successfully calibrated using the proposed method; the average robot position and angle error after calibration was significantly decreased. The position accuracy was improved by 66.9%, and the attitude accuracy was improved by 86.2%.

Propeller blades have freeform surfaces, and the overlap among the blades limits the adjustment range of cutter orientation, making it extremely difficult to generate the required cutter orientation. Therefore, to assist in quickly designing a safe and reasonable machining scheme, a projection-offset method is designed to calculate the feasible region of a ballend cutter and an XYZ-3RPS hybrid kinematic mechanism. Based on this, a reasonable and smooth cutter orientation can be generated using path-planning and trajectory-optimization algorithms. To this end, a method for obtaining point clouds was first developed. By arranging the point clouds of a blank in the cutter path order, the changes to the blank during the machining process can be reflected through point-cloud deletion. A hierarchical bounding box is established for the moving platform of the cutter, spindle, and mechanism, which can realize the quick screening and classification of collision-point clouds. Second, the collision points are projected onto the same plane, an envelope boundary of the projected point cloud was constructed using an alpha-shapes algorithm, and its cross boundary trimmed using the auxiliary boundary method to obtain the feasible region at the cutter contact point. Moreover, to reduce the computational load, an interpolation method, which reduces the number of calculations, is used. The basic rules for cutter-orientation generation were established using a planning function. Then, the cutter-orientation path was smoothed using the trajectory-optimization algorithm to prevent the cutter from swinging violently. Finally, the effectiveness of this method was verified through propeller experiments.

The concomitant vibration and deformation produced by propeller blades in single-sided machining seriously affect the surface machining precision. Double-sided symmetrical machining can improve system rigidity through mutual shoring on both sides which abates the concomitant vibration and deformation. However, the actual double-sided symmetrical machining cannot be applied to blade machining due to its shape complexity. The double-sided collaborative machining method combining symmetrical machining and staggered machining is devised in this paper, and its tool path planning algorithm is investigated. Firstly, the algorithm achieves smooth fitting and correspondence of bilateral cutter position points through double-curve interpolation and position data alignment. Secondly, the blade surface is divided into four regions by two partition parameters: tip region, internal region, variable region, and edge region. Then, the conversion between symmetrical machining and staggered machining is completed through the Sigmoid deformation curve in the variable region. Finally, the feasibility and superiority of double-sided collaborative machining are verified through machining experiments.

The velocity/ acceleration analysis is an important part of the kinematic analysis, which is of great significance to establish a universal and simple velocity / acceleration analysis model to realize the precise control of parallel mechanism. In this paper, according to the differential relationship among position, velocity and acceleration, the velocity / acceleration mapping formula between the driving branch and the position and attitude parameters of the moving platform is established. Moreover, in order to ensure the accuracy of calculation, the characteristic value correction iteration method is used to solve the singular and ill-conditioned of Jacobian matrix and Hessian matrix which may be generate under some special attitudes. The principle of the method is universal and easy to understand, moreover, the experiments show that the method can realize the velocity / acceleration solution of hybrid drive mechanism.

Screw assemblies of radar are characterized by numerous densely distributed small screws of various types, rendering their manual assembly difficult and inefficient. To improve the assembly quality and efficiency, an automatic assembly system was developed. First, the position and attitude relationships among the workpiece, camera, and base coordinate systems of the manipulator were obtained using three-point location and nine-point calibration methods. Second, a visual servoing strategy is designed for guiding the manipulator such that its position can be adjusted adaptively to achieve the high-precision positioning of threaded holes. Third, a method for evaluating assembly quality is developed. The templates of angle–torque curves of various screws were produced by fitting experimental data. Furthermore, the assembly quality was determined by calculating the similarity between the angle–torque curves and templates based on the Fréchet distance. Finally, the feasibility was verified using a flat plate component with five threaded holes.

At present, propeller blades are machined single-sided with low efficiency. Thus, a propeller needs to be turned over after completion of the machining of the first side of the blade, which requires second clamping and causes a decline in accuracy. Therefore, a double-sided collaborative machining method for propeller blades is proposed herein. Two XYZ-3RPS hybrid kinematics machines were symmetrically distributed to machine both sides of a propeller blade simultaneously; therefore, the blade could be machined in clamping once, improving the machining efficiency and eliminating the accuracy decline caused by repetitive clamping. Moreover, a supporting device with rigid-flexible switching capability was developed to reduce the cantilever length of the blade, thereby eliminating the substantial deformation and vibration of the blade during the double-sided collaborative machining process to ensure machining accuracy. Additionally, the inverse kinematics formula for XYZ-3RPS hybrid kinematics machines was deduced and the elongation of each drive shaft through the cutter location point and cutter orientation was solved in this study. Thereafter, the decomposition method of the blade shift data was applied to obtain the deformation and vibration amplitude of the blade so that the performance of the double-sided cooperative machining could be quantitatively analyzed. Finally, experiments were conducted on the self-developed prototype, and the results verified the effectiveness of the double-sided collaborative machining method in reducing the deformation and vibration of a blade and improving machining efficiency.

Reducing carbon emissions and improving revenue in the face of global warming and economic challenges is a growing concern for airlines. This paper addresses the inefficiencies and high costs associated with current aero-engine on-wing washing strategies. To tackle this issue, we propose a reinforcement learning framework consisting of a Similar Sequence Method and a Taylor DQN model. The Similar Sequence Method, comprising a sample library, DTW algorithm, and boundary adjustment, predicts washed aero-engine data for the Taylor DQN model. Leveraging the proposed Taylor neural networks, our model outputs Q-values to make informed washing decisions using data from the Similar Sequence Method. Through simulations, we demonstrate the effectiveness of our approach.

Machine parts are increasingly adopting complex and free-form surface structures to achieve good performance. In this context, technology for collision avoidance is paramount for ensuring that cutters and machining parts do not collide with each other during machining. Therefore, a boundary construction method for obtaining cutter feasible regions is proposed in this study. To ensure that our algorithm is universal and applicable to all conventional cutters, we chose the round nose cutter as the base model. The fixed point of the cutter was analyzed with respect to the cutter contact point, and a hierarchical bounding box was established for the cutter, spindle, and end-effector. Accordingly, the construction methods of the global collision boundary and the local collision boundary were derived, and both were integrated into the feasible region of the cutter orientation. Finally, a marine propeller is taken as an example to verify the effectiveness of the algorithm.

Aiming at the problem that the sequence of operation in the processing of complex parts directly affects the processing cost, an improved harmony search algorithm with the lowest processing cost as the optimization goal is proposed. The constraint relationship between the operation is represented by a process priority diagram. Then use the topological sorting method on the graph to generate the initial sequence as the initial harmony of the harmony memory. The crossover operator is introduced to ensure the feasibility of the new generation of harmony, and the local search method is used to change the machine and tool resources available for the operation to avoid falling into the local optimum. Experimental results show that the improved harmony search method can effectively solve the cost optimization problem of step sequencing.

Decision rules for machining method chains mined from historical machining documents can help technologists quickly design new machining method chains. However, the main factor that limits the practical application of existing rough set models is that the boundary regions are too large. Therefore, a decomposition-reorganization method (DRM) is proposed to mine rules for machining method chains. First, binary coding is used to decompose the existing machining method chains, and the decision rules for a single machining method are mined based on rough set reduction. Then, machining method chains are obtained by reorganizing the machining methods in accordance with the decision rules. DRM can eliminate the boundary regions without human intervention and recommend machining method chains for all features whose parameters have appeared in historical machining documents. Finally, three types of shell parts are used to verify the effectiveness of DRM.