Constraints are one of the main factors that hinder the optimal synthesis of linkages to obtain the global optimum. At present, the most commonly used constraint handling method is called the penalty function (PF) method, but this technique has proven to be inefficient and unreliable in path synthesis. In this paper, a novel and effective constraint handling method called the individual repairing (IR) method is developed for the optimization model of four-bar mechanisms for path synthesis. The function of the IR method is to check the conformity of each individual to the Grashof condition, the sequence condition, and the variable range condition after population initialization and each iteration as well as to repair all unreasonable individuals according to the corresponding repairing technique to make them all satisfy the constraint conditions. In other words, the new constraint handling method establishes a transformation method so that each infeasible point in the search space uniquely corresponds to a feasible point. Based on the IR method, the optimization of path synthesis can be effectively carried out. Finally, the validity and reliability of the new constraint handling method are verified using three examples.

The fast and accurate locating of the tube-sheet annular seam is the key factors to ensure the high efficiency and quality of automatic welding of pressure vessels. Considering the problems of welding sheet deformation and tubes deviation caused by machining process and welding thermal, this paper builds an automatic welding robot platform, which is equipped with a measurement system coordinated by multiple lasers and visual sensors, and put forward a real-time welding distance measurement method based on cross lasers and visual sensors, at the same time, the multi spot laser assisted vision sensor is used to quickly and accurately measure the center of the tube, so as to guide the adjustment of the welding robot and posture of the welding torch in real time. Then, through the measurements of system error, static and dynamic measurement error, it is known that the dynamic accuracy of tube sheet welding distance is not less than 0.22mm, and the positioning accuracy of welded tube center is not less than 0.219mm, which can meet the accuracy requirements of automatic tube sheet welding.

During tungsten inert gas welding process, arc length will change due to thermal deformation, uneven surface of workpiece and tungsten electrode loss. Considering the large fluctuation of arc length in all-position annular seam welding under the action of multi-variable coupling, a mathematical model of arc length and arc voltage was established in this paper, and an isolated and high frequency arc voltage acquisition circuit was designed. An improved sliding filtering algorithm was proposed, and after filtering the real-time arc voltage data, fuzzy control algorithm was used to realize the online tracking control of arc length in annular seam welding, in order to improve the reliability and stability of welding quality of tube-sheet. The experimental results show that the dynamic response time of the proposed arc length tracking compensation method is not more than 40 ms , and the arc length tracking deviation is less than 0.2 mm , which can fully meet the requerements of welding seam tracking of tube-sheet welding.

Hopper scales are critical dynamic metering equipment in industrial production, yet their metrological performance is often compromised by wear on weighing units over long-term service. This study proposes a wear state assessment method based on the evolution of vibration features. Focusing on the rocker-column weighing unit, we analyzed the mechanism by which geometric changes in the spherical indenter—caused by fretting wear—alter the system’s constraint state. A global-to-local coupled Discrete Element Method and Finite Element Method (DEM–FEM) model was constructed to account for material-structure interactions, alongside a dynamic simulation model considering wear evolution. The simulation accuracy was validated through a dedicated experimental platform. The results indicate that as spherical wear intensifies, the low-frequency swaying of the indenter is suppressed, causing the system’s vibration mode to transition from a flexible, swaying-dominated state to a high-frequency, rigid-impact-dominated state. In the frequency domain, this manifests as energy migration, characterized by attenuation of the low-frequency main peak and an elevation of the high-frequency broadband noise floor. Crucially, as a key innovation for wear diagnosis, this study reveals the directional sensitivity of statistical indicators. While the Root Mean Square (RMS) exhibits a non-monotonic V-shaped trend, the Kurtosis and Margin factors of the tangential vibration demonstrate superior monotonic sensitivity. Under severe wear conditions, these two indicators increase by 14 and 11 times, respectively. These findings provide highly effective diagnostic criteria and hold significant engineering application value for the predictive maintenance of industrial dynamic weighing systems.