Testing of hydraulic solenoid valve in brake-by-wire system with brake fluid is difficult to clean and high corrosiveness.The use of compressed air as test medium can effectively solve these problems.Now,the relationship between qualified limits of dynamic response time of hydraulic and pneumatic test has become the focus of research.Therefore,according to structural parameters of solenoid valve,the flow field is analyzed using ANSYS,and fluid force parameters are obtained.Then,MATLAB/Simulink is utilized to construct simulation model,to obtain the relational equation between the response time of hydraulic and pneumatic test.Finally,hydraulic and pneumatic test system are designed to test qualified limit of response time.The results show that when qualified limit of hydraulic test is 3.50 ms,the actual value of pneumatic test is 3.33 ms and the theoretical value is 3.125 ms.The relative error is 6.16％,which verifies the accuracy of model.It is of guiding significance for gas-liquid test of solenoid valve.
Online wear state recognition of key friction pairs in the axial piston pump is of great significance for stable operation and predictive maintenance of the whole hydraulic system. Edge computing (EC) meets the real-time and low-cost requirements of online wear state recognition whereas two challenges limit its application. One is that current fault diagnosis methods only focus on local fault information, causing inaccuracy and poor generalization ability in different working conditions. The other is that the computing power and storage of EC devices are limited. Therefore, a lightweight knowledge-distilled vision transformer (ViT) is proposed for online wear state recognition. A novel time-frequency domain stacked and channel-weighted pooling structure is proposed to directly process raw time series. To realize high accuracy and high generalization ability, a ViT-based teacher model is pretrained to learn local and global information. To narrow model capacity gap and adapt to the limited resource of the edge node, a novel student model with a simplified self-attention mechanism is proposed to mimic the structure of the ViT and learn from the pretrained teacher model through knowledge distillation. An edge node with functions of signal acquisition, data preprocessing, and wear state recognition is designed and the distilled student model is deployed into it. Comparison with other state-of-the-art methods, ablation experiment, and online verification experiment demonstrate that the proposed method trades off wear state recognition performance and hardware limitations.
External contamination particles or wear particles corroded by a valve body are mixed into the fluid. As a result, when the fluid enters the fitting clearance of the valve core, it can cause an increase in resistance and lead to sticking failure of the valve core. This paper analyzes solid-liquid flow characteristics in fitting clearances and valve-core sticking based on the Euler-Euler model, using a typical hydraulic valve as an example. The impact of particle concentration and diameter on flow characteristics and valve-core sticking force was analyzed. The highest volume fraction of particles was in the pressure-equalizing groove (PEG), with peak values increasing as the particle diameter increased. The sticking force increased with increasing particle concentration. When the particle diameter was 12 µm, the sticking force was the largest, making this the sensitive particle diameter. Particle distribution and valve-core sticking force were compared for oval, rectangular, and triangular PEGs. The fluid-deflection angles in oval and rectangular PEGs were larger, and their values were 32.83° and 39.15°, respectively. The fluid-deflection angle in the triangular PEG was relatively small, less than 50
Colonoscopy is the gold standard for colon cancer detection, and early screening can greatly reduce the incidence of colon cancer. A design scheme of soft robot based on bionics is presented. It adopts soft material structure of three chambers, and controls the bending direction and angle of the robot by controlling the pressure of the chamber. The soft robot is installed at the end of the traditional colonoscopy to replace the traditional manual operation, and is used for guiding during the colonoscopy surgery, which can effectively avoid unnecessary contact between the colonoscopy and the intestine during the colonoscopy propulsion and extraction process. By means of finite element analysis, the shape and layout of the driving cavity and multi-stage structure of the soft robot are optimized and simulated, and the design parameters of the soft robot are optimized and a prototype of the robot is developed. Finally, the bending performance of soft robot is verified by experiments.
随着液压泵等液压元件的发展趋向高压、高功率、高转速,液压元件测试台的功率也在不断提高,造成更多的能量消耗,因此试验台的功率回收至关重要.分析了电功率、机械补偿和液压补偿的功率回收系统方案,确定出液压泵马达测试台较为理想的功率回收系统形式.对选用的电功率回收系统通过AMESim软件建立了功率回收系统模型,对不同工况下电功率回收系统的回收率进行分析.
