Micro-abrasive jet machining technology is a type of abrasive erosion and wear machining technology based on high-energy fluid, which has been widely used in machining difficult-to-machine materials, complex threedimensional surfaces, and smooth surfaces. In order to further improve the ability of precise shape control in abrasive jet machining, domestic and foreign scholars have carried out many investigations on basic machining theory and technology exploration. Based on summarizing the development of abrasive jet machining technology, this paper comprehensively summarizes the main research results of domestic and foreign scholars in micro-abrasive air-jet machining technology. Such technologies include the divergence effect of micro-abrasive air-jet beam and its suppression strategy, the impact of material mechanical properties on material erosion removal mode, the abrasive embedding inhibition strategy in material erosion processing and the geometric characteristics of micro-structure erosion machining. Difficulties and the development trend of micro-abrasive jet machining technology are also investigated.

The permeability tensor of fiber reinforcement, as the decisive input parameter of resin flow simulation of liquid composite molding process, is closely related to the resin flow and final product quality, and is the key to realize the high-quality and large-scale manufacturing of composite materials. In this paper, the permeability measurement techniques are classified according to the flow states (saturated or unsaturated), flow dimensions and measurement directions (in-plane or out-of-plane). The permeability measurement techniques and research progress under different conditions are listed, and the real-time monitoring techniques of flow front in unsaturated flow are summarized. The problems such as different experimental factors and large dispersion of permeability results are analyzed, and the future development trends are discussed.

With the focus on one kind of mirror milling system consisting of two hybrid robots, the canonical forward and inverse kinematic model of the mirror milling system is developed by the vector method, in which the forward kinematic has the advantage of high computational efficiency and accuracy compared with the solution method using the Newton iterative method. A method for generating mirrored machining path is proposed, which specifies the positional relationship between the reference coordinate systems of two hybrid robots, and calculates the mirrored symmetric tool and support head paths by setting the desired machining wall thickness of the thin-walled structural part. Two methods for executing mirrored machining path are proposed by employing 10-axis linkage and dual 5-axis linkage respectively. The latter has the features of reconfigurability and modularity compared with the former, which supports single-machine operation of the milling or supporting robot, and satisfies the needs of rapid on-site arrangement and efficient collaborative machining of single or multiple machines in a large workspace. In order to verify the correctness and effectiveness of the proposed kinematic model and methods for generating and executing machining paths, experiments of machining a large scale thin-walled structural component are carried out. The experimental results show that the error of the machined wall thickness can be guaranteed within ±0.18 mm.

To measure the real assembly force of industrial robots precisely in aircraft assembly, a method of gravity identification and online compensation for the robot end-effector based on the laser tracker is proposed. With the help of external measuring equipment such as a laser tracker, the global kinematics model of the robot system is set up to realize the accurate acquisition of the end-effector pose of the robot. Then, Kalman filtering is utilized to process the force/torque signal to obtain more exact and stable external information, and the relationship between the gravity component and the pose of the end-effector is established, considering the influence of the zero-point bias of the sensor and the error of the robot installation. Finally, an online gravity compensation experiment of the robot end-effector is conducted and demonstrates the effectiveness of the proposed method.

In order to explore the influence of different machining paths and their arrangement on workpiece grinding effect, the influence law of robotic grinding paths on workpiece surface quality was studied. Based on Preston removal equation and Hertz contact theory, the material removal depth model of abrasive belt grinding was established. Then the formation mechanism of surface residual texture was analyzed. Taking curved aero-engine blades as experimental objects, equidistant paths and cycloidal paths were used respectively for machining experiments on a self-built robotic grinding system. Material removal effect and surface texture were analyzed. The experimental results show that the traditional linear machining isometric path produces strip texture at the joint. Because of its multi-directional machining action, the cycloid homogenizes the surface texture and improves the consistency of machining surface.

With the development of the aviation industry, the performance of aircraft has been improving, and the requirements for quality inspection have been continuously increasing. Compared with traditional manual methods, robot-based automated inspection technology has higher operating accuracy and efficiency, and has been widely used in aviation manufacturing and maintenance processes. This article focuses on the application of robot-based automated inspection technology in various aspects such as component processing, finished product quality inspection, and aircraft maintenance and repair over the past decade, especially in surface drilling process inspection, large, irregular and complex component processing inspection, internal material nondestructive inspection, structural shape inspection, aircraft skin and surface quality inspection and aircraft internal narrow space inspection. This paper reviews in detail the application effects of different kinds of robots such as six-axis industrial robots, wheeled mobile robots, crawling robots, continuum robots and unmanned aerial vehicles with ultrasonic, optical and other types of detection technologies. Most of the articles reviewed were summarized in a table for reference by the researchers concerned. In conclusion, research on robot-based automated inspection technology is of great practical significance for improving quality control in aviation manufacturing and maintenance processes, but it still faces challenges of insufficient flexibility, insufficient algorithm intelligence and insufficient human-computer interaction research.

In order to remove paint from aero-engine casing surface, a study on laser cleaning of Cessna 172 aircraft engine casing surface was carried out by using nanosecond pulse laser. By analyzing the surface topography and roughness of the paint removal area of the casing, the influence of laser energy density and scanning speed on the cleaning effect of the paint layer on the casing surface was explored, and the optimal process parameters of laser paint removal on the casing were determined. The surface quality, microhardness and roughness of the casing after removing paint were comprehensively evaluated. The results show that both energy density and scanning speed significantly affect the paint removal quality of casing. When the energy density is 18.33 J/cm² and the scanning speed is 1600 mm/s, the paint removal rate is 98.7%, the surface roughness S_a is 2.48 μm, the casing itself is not damaged, and the surface microhardness is increased by 1.9%, which meets the paint removal quality requirements of the casing surface. The research results provide theoretical and technical support for laser paint removal of engine casing.

Laser surface texturing is an effective method to improve the shear strength of the dissimilar joints, and has been widely used in laser joining CFRP to metal. In this work, a femtosecond laser with a wavelength of 515 nm was used to fabricate microstructure on the surface of 2060 Al–Li alloy. And on this basis, high-speed fiber laser joining of CFRP to 2060 Al–Li alloy was realized by a rectangular beam spot, which could provide a relatively uniform energy density. The influence of ablated depth of the microstructure and the scanning line space on the shear strength of dissimilar joints was investigated. The results indicate that the shear strength of the dissimilar joints is greatly improved through femtosecond laser texturing. All the dissimilar joints fail with the mixed failure mode composed of the CFRP matrix fracture and interface fracture. Remarkably, the average shear strength of the dissimilar joints is 35.7 MPa at a relatively high welding velocity of 3.6 m/min and a laser power of 5 kW, which is 2.3 times that of the joint without femtosecond laser texturing.

The sensor installation position is limited and the collected signal is easily disturbed by external noise in the existing RV reducer condition recognition. The comprehensive utilization of servo characteristic information to monitor the load condition of the RV reducer can improve the service performance of industrial robots in the field of manufacturing. Firstly, according to the structural parameters and working mechanism of the RV reducer, analyzed the correlation between the input speed and the important frequency, the servo characteristic information and the load of the RV reducer. Then, constructed the correlation identification model between servo feature information and RV reducer load based on the K-means clustering algorithm. Finally, the experimental platform of the RV reducer is built to collect the feedback information of the servo system under different load conditions. After corresponding processing, the correlation identification model is used to realize the accurate identification of load state, and the recognition rate is as high as 97.45%. This paper can provide technical support for monitoring the running state of RV reducer based on servo characteristic information.

Cutting chatter can lead to problems such as poor surface quality of the machined workpiece, reduced material removal rate and increased tool wear. The tool tip modal parameters are essential inputs for constructing stability lobe diagrams and selecting chatter free machining parameters. However, in the machining process, the tool tip modal parameters change with the tool pose and the tool changes frequently, and the classical impact test method has low efficiency and high cost, so how to accurately and efficiently predict the tool tip modal parameters under the changed pose has become an urgent problem to be solved in the cutting process. In this paper, combined with the idea of transfer learning, a method of modal parameter prediction based on multi-source transfer learning is proposed. When a new tool is used, the tool point modal parameters under only a few positions need to be measured through impact test, and then the tool point modal parameter prediction model for the new tool can be obtained by multi-source transfer combined with the modal parameter data of multiple existing tools. Finally, a practical experiment on a five-axis machine tool shows that the proposed method is effective.

Injection molding of the TC4 titanium alloy was investigated using the low-cost hydrogenationdehydrogenation (HDH) powders modified by jet-milled (JMed) as the raw material. Three types of powders, including HDH, jet-milled (JMed) HDH and gas-atomized (GA), were compared in terms of maximum loading capacity, sintered density, impurity content, microstructure, and mechanical properties. Results showed that the particle sphericity of the JMed powder was significantly improved and thus enhanced the maximum loading capacity (volume fraction) by 6%, and exhibited higher sintering densification, as compared to the original HDH powders. After sintering at 1300 ℃ for 2 h, the density of the sintered parts using the JMed powders is 98.3%, higher than that using the original HDH powders (95.3%), while equivalent to that using the GA powders (98.4%). The room temperature mechanical properties of the sintered parts using the JMed powders showed the tensile strength of 904.2 MPa, yield strength of 809.1 MPa, elongation of 8.14% respectively, much better than those using the original HDH powders. Furthermore, the strength of the sintered parts using the JMed powders demonstrated equivalent performance to that using the GA powders, indicating the quasi-spherical TC4 powders exhibiting a great potential for engineering applications.