Hua Chen

Vibration affects the accuracy and efficiency of mechanical systems, especially in high-speed mechanical systems. Input shaping is an open-loop active vibration suppression technology that does not require complex sensor feedback hardware and offers the advantages of low cost and ease of deployment. However, traditional impulse-based shapers still have shortcomings in vibration suppression performance, delay, and robustness. This paper proposes a new shaping design method based on linear signals, namely, LS. The LS shaper is linear, has high solution efficiency, and has significant improvements in amplitude suppression effect and delay compared to traditional pulse shapers. Moreover, by differentiating with respect to natural frequency, a more robust shaper (LDS) can be obtained, which significantly improves the disturbance rejection capability of motion system without significantly increasing the time delay. Simulation and experiments have verified the excellent performance of LS and LDS. The method proposed in this paper provides a new and more effective vibration suppression method for open-loop control systems and is expected to be widely applied in precision motion control fields.

In selective laser melting (SLM), the relationships between process parameters and surface quality are highly nonlinear, while different quality indicators are often mutually conflicting, making multi-objective optimization under limited experimental budgets challenging. To address this issue, this study proposes a direct Gaussian process (GP)-based multi-objective Bayesian optimization framework for the efficient optimization of SLM process parameters. Targeted improvements in surrogate modeling and acquisition function design enable effective characterization of coupled multi-objective responses with a limited number of evaluations. Surface roughness ( S _a ), defect area ratio, and macroscopic warpage root mean square were selected as optimization objectives based on laser confocal microscopy measurements, while laser power, scanning speed, and hatch spacing were treated as design variables. Comparative studies with the conventional GP-expected hypervolume improvement method and the evolutionary algorithm Non-dominated Sorting Genetic Algorithm II (NSGA-II) demonstrated that the proposed approach achieved faster convergence and superior Pareto front approximation under the same evaluation budget. From an engineering perspective, the proposed framework reduces reliance on extensive experiments and enables the identification of practically feasible parameter combinations, providing an efficient and transferable solution for intelligent SLM process optimization.

Motion stages are critical in semiconductor manufacturing equipment for processes like die bonding, wafer loading, and chip packaging, as their performance must meet the industry's stringent precision requirements. Vibration, a significant yet often overlooked adversary to precision motion stages, is challenging to identify and mitigate due to its subtle nature. This study, conducted at a motion stage manufacturer facing frequent vibration-related complaints, proposes a novel approach to resolving vibration issues. By leveraging the DMAIC methodology, it introduces VIBGUARD, an active vibration monitoring and mitigation solution, instead of solely focusing on traditional hardware vibration control. This comprehensive strategy enhances value and competitiveness, increasing UPH (units per hour) by 15.3% from 8,500 to 9,800 and reducing downtime by 68.2% from 2.2 to 0.7 occurrences per month. This case study and the DMAIC methodology offer valuable resources for quality control and problem analysis in the semiconductor industry.

The assembly precision of the spindle has a direct impact on quality and performance of the high-speed winder. Assembly sequence is one of the key influencing factors. In actual production activities, the spindle assembly of high-speed winder has the characteristics of numerous parts and long process, which easily leads to illogical arrangement of assembly sequences and a high reassembly rate. In this paper, for the issue of assembly sequence planning (ASP), a novel assembly sequence evaluation system was established, and an ASP algorithm was designed. Firstly, the structure and assembly characteristics of spindle were analyzed. Then, an evaluation system for planning assembly sequences was built, taking into consideration two key factors: assembly efficiency and quality. A discrete flower pollination-genetic algorithm (DFP-GA) was explored to plan the spindle assembly sequence, presenting the rules for generating the initial population, designing a mechanism of dynamically adjusting the conversion probability, and incorporating a crossover-mutation operation of the genetic algorithm. These modifications have effectively addressed the problem of local optimal solutions, making the algorithm suitable for discrete optimization issues. Finally, this study conducted a comparative experiment of different algorithms using a simplified spindle. DFP-GA demonstrated a probability of obtaining the optimal sequence of up to 83%, exceeding other algorithms by 35%, 6%, and 31% respectively. It also exhibited significantly faster convergence speed, confirming its superiority in solving the ASP problem. This algorithm can enhance production efficiency and reduce manufacturing costs of spindles.

Tracking rigid objects in three-dimensional (3D) space and 6DoF pose estimating are essential tasks in the field of computer vision. In general, the region-based 3D tracking methods have emerged as the optimal solution for weakly textured objects tracking within intricate scenes in recent years. However, tracking robustness in situations such as partial occlusion and similarly colored backgrounds is relatively poor. To address this issue, an improved region-based tracking method is proposed for achieving accurate 3D object tracking in the presence of partial occlusion and similarly colored backgrounds. First, a regional cost function based on the correspondence line is adopted, and a step function is proposed to alleviate the misclassification of sampling points in scenes. Afterward, in order to reduce the influence of similarly colored background and partial occlusion on the tracking performance, a weight function that fuses color and distance information of the object contour is proposed. Finally, the transformation matrix of the inter-frame motion obtained by the above region-based tracking method is used to initialize the model point cloud, and an improved point cloud registration method is adopted to achieve accurate registration between the model point cloud and the object point cloud to further realize accurate object tracking. The experiments are conducted on the region-based object tracking (RBOT) dataset and the real scenes, respectively. The results demonstrate that the proposed method outperforms the state-of-the-art region-based 3D object tracking method. On the RBOT dataset, the average tracking success rate is improved by 0.5% across five image sequences. In addition, in real scenes with similarly colored backgrounds and partial occlusion, the average tracking accuracy is improved by 0.28 and 0.26 mm, respectively.

The engine is a typical complex machine with many mechanisms and high precision. The tolerance of the valve gap is an accumulative result of component tolerances on the valve mechanism, which is very critical to engine performance. The current tolerance analysis is carried out using the traditional linear dimension chain, and it is difficult to consider a large number of geometric tolerances. The analysis result is not consistent with reality. Based on an innovative three-dimensional tolerance model, i.e., the unified Jacobian-Torsor model, tolerance analysis and allocation for valve gap were presented in this paper, where large geometric and partial parallel connections were taken into consideration. For the special conical structure in the valve mechanism, the expression and variation of the conical torsor were deduced. At last, a real engine was selected as an example of the analysis process. Sufficient comparison and discussion were made for the results, which demonstrated the effectiveness of the method.