Jinghui Peng

In this paper, a double-mode self-calibration tension system is proposed, which adopts the conversion of hydraulic meter tension and the monitoring of standard force sensors. According to the material characteristics of the jack and the viscosity and temperature characteristics of the hydraulic oil, the differential model of heat conduction in the hydraulic cylinder and the mathematical model of oil film friction heat generation are established, and the internal thermodynamic characteristics of the jack are theoretically analyzed, which provides theoretical support for the temperature compensation of the hydraulic oil pressure gauge of the jack. A simulation analysis was conducted on the thermodynamic characteristics of the hydraulic jack, and the distribution patterns of the temperature field, thermal stress field, and thermal strain field inside the hydraulic cylinder during normal operation were determined by measuring the temperature changes in five different parts of the jack at different times (t = 200 s, 2600 s, 5000 s, 7400 s, and 10,000 s). For the issue of heat generation due to oil film friction in the hydraulic jack, a simulation calculation model is developed by integrating Computational Fluid Dynamics (CFD) techniques with dynamic grid and slip grid methods. By simulating and analyzing frictional heating under conditions where the inlet pressures are 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.7 MPa, and 0.9 MPa, respectively, we can obtain the temperature distribution on the jack, determine the frictional resistance, and subsequently conduct a theoretical analysis of the simulation results. Using the high-precision standard force sensor after data processing and the hydraulic oil gauge after temperature compensation, the online self-calibration of the tensioning system is carried out, and the regression equation of the tensioning system under different oil temperatures is obtained. The double-mode self-calibration tensioning system with temperature compensation is used to verify the compensation accuracy of the proposed double-mode self-calibration tensioning system.

Cooling channels are typically integrated into high temperature flow regulating valves to mitigate the adverse effects of elevated temperatures on the operation of digital valves and embedded sensors. However, conventional straight cooling channels often suffer from inefficient heat dissipation and excessive pressure losses. In this study, a novel high temperature flow regulating valve incorporating 12 Tesla cooling channels is proposed to simultaneously optimize heat transfer enhancement and flow resistance reduction. Three-dimensional steady-state numerical simulations, based on the Navier–Stokes equations (Laminar flow model), were conducted to analyze the pressure, temperature, Colburn factor (j), and friction factor (f). The Colburn factor (j) was determined from the relationship between heat absorption, surface temperature difference, heat transfer area, and mass velocity of the fluid, while the friction factor (f) was derived from the correlation between the inlet-outlet pressure difference, hydraulic diameter, and mass velocity of the fluid. Numerical results reveal that the mixed cooling capacity of the Tesla structure improves with increasing inlet pressure. Among the 12 schemes, Scheme 1 exhibited the highest heat transfer enhancement with the maximum Colburn factor (j) of 0.173, while Scheme 5 demonstrated the best flow performance with the lowest friction factor (f) of 1.357. Experimental validation confirmed close agreement between the experimental data and numerical results, with discrepancies within 8.83% for j and 6.39% for f. Through analysis of the JF impactor factor, which evaluates the combined performance of heat transfer and flow, the high temperature flow regulating valve with Scheme 11 Tesla cooling channels achieved optimal overall performance, enhancing heat transfer capacity by up to 28.7% and reducing maximum pressure losses by 17.9%. This study provides valuable insight for the design of the valve, enhancing their thermal management and operational efficiency.

The electro-hydraulic servo valve is a critical component that transforms electrical signals into hydraulic signals, thereby controlling the hydraulic system. It finds extensive application in precision control systems. The stability of the electro-hydraulic servo valve is primarily influenced by the armature assembly. Unlike integral armature assembly, the separated armature assembly, comprising the armature, spring tube, flapper, and feedback spring, is joined through an interference fit, which introduces prestress within the assembly. The existence of prestress may affect the operational mode of the armature assembly. Consequently, this paper investigates the vibration characteristics of the separated armature assembly under interference fit conditions. Comparative analysis reveals that interference fit indeed generates prestress, which cannot be overlooked. To further validate the reliability of the simulation results, the natural frequency of the separated armature assembly is determined by applying a sweeping frequency signal to the torque motor using an electric drive, thereby verifying the feasibility of the simulation analysis. Additionally, the impact of interference on the vibration characteristics of the separated armature assembly is examined, confirming the accuracy of the simulation analysis method based on the interference fit. The research on vibration characteristics of a separated armature assembly provides technical support for the structural optimization design of the electro-hydraulic servo valve, thereby enhancing its performance.

The self-excited oscillation of an electro-hydraulic servo valve is a crucial factor that affects the operational stability of both the servo valve and the entire servo system. As the intermediary for electromagnetic force, hydraulic force, and feedback force, the dynamic characteristics of the armature assembly play a pivotal role in the emergence of self-excited oscillations. In this article, a mathematical model of the armature assembly is developed using the finite element method (FEM), which establishes a connection between the input signal and the dynamic characteristics of the armature assembly. The structure of the parameter matrix and the recursive relationship of discrete time steps are derived, while the discrete method of the feedback rod and the discrete time format of the FEM model are also analyzed to enhance the prediction accuracy of the model. To validate the efficacy of the FEM model, a numerical simulation model, a classical mathematical model, and an experimental platform are constructed to simulate or measure the dynamic characteristics of the armature assembly. Through the comparison of the dynamic characteristics obtained by the abovementioned methods, it is confirmed that the FEM model effectively predicts both the static and dynamic characteristics of the armature assembly. To suppress the vibration magnitude within the natural frequency range of the armature assembly, the external load that can effectively mitigate the resonance amplitude is calculated based on the FEM model, and the aim of ensuring the stable functionality of the armature assembly throughout its operational range is achieved.

For the flapper-nozzle servo valve, the existence of the flow separation phenomenon in the pilot stage may lead to self-excited oscillation, which is a hidden danger to the stability of the servo valve. Aiming at improving the flow state and the stability of the flow field in the pilot stage, a new structure of flapper with vortex generators without disturbing the control performance of the pilot stage is designed. The flow separation phenomenon in the pilot stage is confirmed by analyzing the flow with traditional flapper under different inlet pressures. The flow field in the pilot stage is explored using vortex generators compared to traditional one, the results show that the flow state of the pilot stage flow field is changed by the novel flapper with vortex generators, the flow separation phenomenon is well controlled, the number of vortices in the flow field is significantly reduced, and the flow field is more stable. Therefore, the compact and effective vortex generators have a good effect on improving the stability of the flow field in the pilot stage of flapper-nozzle servovalve. The primary parameters of vortex generators, height and location, are also taken into account, it is found that when the height of vortex generators h=0.2 and the location size l=0.4, it is more suitable for the actual situation.

The high-frequency vibration and resonance of armature assembly in the hydraulic servo valve are the main reasons for instability and failure. Magnetic fluid (MF) operating in the squeeze mode can be taken as an effective damper for resonance suppression in the servo valve. Due to excitation difficulty and the low signal-to-noise ratio of high-frequency vibration signals, the capability of MF to modify multiple-order modal damping ratios in a multi-degree-of-freedom system is still unclear. To reveal the mechanism of magnetic fluid for improving modal damping ratios, an algorithm for modal damping ratio identification is proposed. The modal damping ratios of the armature assembly with and without magnetic fluid are identified based on the tested resonance free decay responses. Four resonance frequencies of armature assembly are observed, and the corresponding damping ratios are identified. The equivalent modal damping ratios due to squeeze flow of MF are obtained. The results show that the proposed algorithm can identify damping ratios with an accuracy of up to 98.79%. The damping ratios are improved by double or more due to the magnetic fluid, and the maximum resonance amplitudes are significantly reduced by 65.2% (from 916.5 μm to 318.6 μm).

High-temperature gas flow rate control valve (GFRCV) with Laval structure is the core component of gas control system. The influence of fluid-thermal-structure (FTS) coupling deformations on the characteristics of GFRCV is a noteworthy issue. In this work, numerical simulations by two-way FTS coupling method and single computational fluid dynamics (CFD) method are conducted to analyze the velocity distribution, pressure distribution, deformations and flow characteristics of GFRCV with Laval structure. Variation regularities of velocity, pressure, and flow characteristics calculated by two-way FTS coupling method are more in line with the actual working conditions in consideration of the influence of FTS coupling deformations on flow characteristics, which reveals that two-way FTS coupling numerical calculations are more meaningful in engineering application.

Much of ongoing robotic endoscope research is focused on locomotion, with only limited exploration into feedback control and autonomy in the unconventional and dynamic in vivo environment. This letter presents a modular endoscopy simulation apparatus (MESA) to quickly, affordably, and repeatedly test novel robotic endoscope control schemes in a synthetic colon at an accessible scale. The MESA allows for replication of many common physiologic barriers for current medical robotics, such as disturbances, patient positional changes, angulation of the colon, and a dynamic visual environment. The MESA will allow research teams to quickly and repeatedly validate new control strategies to minimize the effect of these physiological barriers before testing in costly in vivo procedures. The MESA platform and synthetic colon described in this letter have shown successful replication of colon geometry, visual appearance, peristaltic wave speeds and pressures, and disturbances from patient movement. The mold for the synthetic colon was built in sections to allow for geometry changes for future molds and has shown marked similarity to in vivo images from colonoscopies. The actuators chosen for the various controllable stages have proven ample power to produce maximum-case disturbances expected during procedures, and the stages are modular in structure to allow for a variety of testing scenarios. Inflatable rubber tubes and electronic solenoid valves are used to produce contractile forces, and have shown excess capability to reproduce physiological motility. The simulator presented here will aid in future feedback control, localization, and autonomy development for robotic endoscopes.