Aerodynamic parameters obtained from separation experiments of internal stores in a wind tunnel are significant in aircraft designs. Accurate wind tunnel tests can help to improve the release stability of the stores and in-flight safety of the aircrafts in supersonic environments. A simulative system for free drop experiments of internal stores based on a practical project is provided in this paper. The system contains a store release mechanism, a control system and an attitude measurement system. The release mechanism adopts a six-bar linkage driven by a cylinder, which ensures the release stability. The structure and initial aerodynamic parameters of the stores are also designed and adjusted. A high speed vision measurement system for high speed rolling targets is utilized to measure the pose parameters of the internal store models and an optimizing method for the coordinates of markers is presented based on a priori model. The experimental results show excellent repeatability of the system, and indicate that the position measurement precision is less than 0.13 mm, and the attitude measurement precision for pitch and yaw angles is less than 0.126°, satisfying the requirements of practical wind tunnel tests. A separation experiment for the internal stores is also conducted in the FL-3 wind tunnel of China Aerodynamics Research Institute.

•A novel triangular vision-based measurement system and method are first proposed for the contouring error detection of machine tools.•Three-dimensional contouring error detection of an arbitrary trajectory for a machine tool under a high feed rate and large motion range can be accomplished in one set-up.•Experimental results verified the vision-based contouring error measurement accuracy and feasibility.Contouring error detection for machine tools can be used to effectively evaluate their dynamic performances. A triangular vision-based contouring error detection system and method is proposed in this paper, realizing the three-dimensional error measurement of an arbitrary trajectory in conditions of a high feed rate and wide motion range. First, a high-precision measurement fixture, which consists of high-precision circular coded markers and a highly uniform light source, is designed to accurately characterize the motion trajectory of a machine tool and realize the high-quality collection of an image sequence. Then, to improve the contouring error detection accuracy, a coded marker decoding and center location method for the automatic recognition and high-precision center positioning of the circular coded markers are applied. Using image preprocessing and matching, the markers’ three-dimensional coordinates in the camera coordinate system can be constructed. Moreover a data transformation method induced by the orthogonal motion of machine tools is proposed to obtain the three-dimensional trajectory in the machine tool coordinate frame and the contouring error can be calculated. Finally, a three-dimensional contouring error detection study of an equiangular spiral interpolation at different feed rates is performed in the laboratory. It is shown that the average contouring error for a feed rate of 1000 mm/min is about 3 µm, which verifies the vision measurement accuracy and feasibility.

•Online detection method with noise suppression is proposed for cylindrical objects.•The method uses credibility evaluation of centre points.•Correlation expression for energy and light stripes cross-section positions presented.•Centre points credibility determination method for greyscale distribution rule given.•Proposed noise suppression method practically eliminates cylinder objects’ noises.Measurement based on vision sensors plays a significant role in process control and product quality in manufacture process. In extreme conditions, the ability to effectively distinguish information from noise is essential in the measurement process. In this paper, an online detection method that achieves noise suppression based on credibility evaluation of centre points is proposed which is applicable to cylindrical objects. A correlation expression between energy and relative position of the cross-section of the light stripes is also derived, and a method for determining the credibility of centre points with the greyscale distribution rule of the correlation expression is established. Experimental results indicate that the greyscale distribution rule for light stripes is reliable, and the noise suppression method can eliminate the noise of cylindrical objects. In the experiments conducted, the relative error of laboratory measurements using the proposed method reduced from 1.84% to 0.33%.

•An image evaluation model based on the SNR of the ROI is proposed.•An image quality compensation method for image acquisition in different temperature is proposed.•The image quality of hot forgings at high temperatures are significantly improved.•Experiments are performed both in a laboratory and a forging workshop.Machine vision has already been used for measuring the dimensions of hot forgings. However, the features of hot forgings are not sufficiently clear to be extracted robustly and efficiently because of the poor image quality caused by the radiation that the hot forgings emit. Therefore, to obtain clear images, an improved image acquisition method for the measurement of hot forgings using machine vision is proposed in this paper. Firstly, an image evaluation model based on the Signal to Noise Ratio (SNR) of the Region of Interest (ROI) is established. Then, main interference factors that affect the quality of image, such as the forgings radiation light and laser light, are analysed. Next, the compensation parameters for clear image acquisition in spite of time-varying temperature are obtained. Finally, the laboratory experiments indicate that the quality of the forging images with the laser strips is improved effectively. Meanwhile, three hot parts with different heights are measured in laboratory, and the absolute error is less than 0.32 mm, the relative error is less than 0.27%. The dimensional measurement of the hot forging in a workshop is also conducted to verify the effectiveness of the presented system.

In micro-electrical discharge machining (micro-EDM) process, the property of high-frequency discharge and complex interference causes the discharge state to vary fast, and conventional control methods of micro-EDM have the hysteresis characteristic, which make it very difficult to conduct efficient and stable control. Firstly, in this paper, based on calamities grey prediction theory, a new method for discharge state prediction is proposed, where the voltage and current signal are replaced with the output velocity of conventional control system as the direct predictive target, and the negative velocity (electrode pullback) is regarded as a calamity value. Owing to avoidance of processing voltage and current signals with nonstationarity, nonlinearity, and internal coupling characteristics, the proposed discharge state prediction method, which predicts that whether the future processing cycles are in short-circuit discharge state, exhibits good real-time performance. Thereafter, by virtue of multi-thread technology, the proposed discharge state-predictive method is added to a conventional control system, and a discharge state real-time predictive control system of micro-EDM is established in this paper. Finally, experiments on machining micro-holes and micro-grooves are conducted using the proposed predictive control method and fuzzy control method. Experiment results indicate that the proposed predictive control method has stable and good real-time performance, and it can effectively reduce electrode pullbacks and improve the processing efficiency and processing quality in both micro-hole and micro-groove EDM.

Non-contact dimensional measurements of forgings are desirable to permit real-time process control. Machine vision technology has been widely employed as a high-speed, non-contact method in dimensional measurement. However, the extracted features of high-temperature forgings are not suitable for application because of self-emitted radiation. This paper primarily introduces a spectrum selective method for improving the image quality of hot parts. By filtering certain wavelength range light and projecting light to hot parts surface, the images of the hot parts can be obtained without interference from self-emitted radiation. Experiments were also conducted to indicate that the images of hot parts were greatly improved and the feature points could be extracted and matched using the proposed method.

•We propose a vision measurement method for measuring pose parameters of high-speed models in wind tunnel.•An acceleration-helix layout is proposed to overcome hidden phenomenon of small markers.•A pose calculation method based on identified points was proposed to implement the solution of pose parameters.•Experimental results indicate that the proposed measurement method is effective.The position and attitude measurement of high-speed isolates for hypersonic facilities plays an important role in structural design and aerodynamic analysis for the core facilities of aeronautics, astronautics, and navigation industries. One of the important high-speed isolates for hypersonic facilities is the high-speed and rolling target. In this paper, a rapid position and attitude measurement method based on binocular vision theory has been proposed for high-speed and rolling target in the dark wind tunnel environment. Firstly, by selecting and combining the proper light and markers, high-resolution images of the high-speed and rolling target are captured by two high-speed CCD cameras in the dark and complicated wind tunnel. Then, an acceleration–helix layout of markers is proposed to solve the markers hidden-phenomenon during the rolling procedure of for the elongated high-speed target in the larger space. Moreover, the high-accuracy recognition of the corresponding markers in the images is achieved on the basis of the markers layout. Then, position and attitude parameters of the high-speed and rolling target are calculated according to the recognized markers on the surface of the rolling target. Finally, simulative experiments on measuring the pose parameters of the rolling target in wind tunnel are conducted, and the experimental results indicate that the proposed measuring method is effective. Besides, an additional experiment in the laboratory verifies that the measurement accuracy can meet the measuring requirements in wind tunnel facilities.

•A sub-regional processing method with variable machining parameters is proposed.•The proposed approach is suitable for parts with rapidly varied geometric feature.•The generation mechanism of the machining error is studied.•The relation between the programmed feed speed and the curvature is established.•The drive constraint is taken into account in the NC machining method.As the existence of rapidly varied geometric feature and during the NC manufacturing process of this kind of parts, the actual moving speed of the workbench of the NC machine tool cannot reach the feed speed set in the NC program timely due to the drive constraint of NC machine tool. Furthermore, the machine tool would vibrate violently with the drive constraint when employing the constant machining parameter to process the parts with rapidly varied geometric feature, which seriously restricts the improvement of processing this kind of parts with high quality and high efficiency. In order to manufacture such parts with high quality and high efficiency, a sub-regional processing method with variable machining parameters is proposed. Firstly, the generation mechanism of the machining error is studied, and its mathematical model is built. Then the change rule of the machining error influenced by the curvature and the NC programmed feed speed is found out. Finally, taking the drive constraint and the machining error requirement into account, the relationship between the programmed feed speed and the curvature is established, and the corresponding programmed feed speeds to different curvatures are obtained. Taking the NC machining of the edge line of spiral microstrip antenna, which is an equiangular spiral, for example, the experiment results show that compared with the machining result with constant machining parameter, the maximum machining error of the sub-regional processing method with variable machining parameters decreases by 35.51% and the average value of the machining error decreases by 46.65%. For another example, the clover rose line is machined and the processing quality is also improved. This study proves that the method distributing the programmed feed speeds based on the curvature variation can improve the machining precision and ensure processing efficiency, and provides an effective method to manufacture parts with rapidly varied geometric feature.