Electro-hydraulic control valve (EHCV) with integrated controller commonly utilizes a linear variable displacement transformer (LVDT) to measure spool displacement and achieve closed-loop control. However, the switching power drive circuit controlled by pulsewidth modulation (PWM) within the controller introduces ripple interference to the electrical signal. In addition, as an inductive component, the LVDT exhibits hysteresis in its inductive signal, making the design of a high-precision conditioning circuit complicated and limiting the precision of spool displacement measurement. Based on the LVDT signal-conditioning hardware architecture, this study enables efficient and precise signal phase adjustments, achieving adaptive sampling (AS) to mitigate ripple interference. Noise-suppressing high-precision demodulation is further achieved through sampling position optimization (SPO), forming a novel digital conditioning method for spool displacement measurement in EHCVs. The experimental results of signal demodulation indicate that the proposed high-precision digital conditioning method effectively reduces the noise level of the standard spool displacement signal (SSDS). The SSDS's mean precision is improved to 0.21%, and its mean maximum error is limited to 0.12%. The dynamic and static experimental results of the EHCV further validate that the high-precision digital conditioning method significantly enhances the valve performance.

Pilot-operated directional valves usually used for flow capacities spanning 100-1000 L per minute (L/min) which widely used in specific hydraulic systems. To reduce the deadzone caused by pilot valve overlap, improve the pilot valve response speed, and mitigate directional switching hysteresis and zero-crossing hysteresis of the MVS, this paper investigates an active damping control method for a proposed pilot-operated proportional directional valve with an independent metering pilot stage. This method employs independent metering technology, calibrates and analyzes the flow characteristic of the novel pilot valve via the pilot-stage flow characteristic calibration approach, and implements a MVS displacement control strategy that is based on pilot-stage flow characteristic compensation. The method is adjusted by two independent pilot valve spools, one pilot valve spool is controlled to drive the main spool and the other pilot valve spool is controlled to adjust the damping effect. Additionally, pre-matched solenoid currents are applied to generate an active damping effect on the flow characteristics. The experimental results demonstrate that the active damping control method enhances steadystate position tracking accuracy to 0.23%, particularly reducing the small-amplitude sinusoidal position tracking errors to 0.6%. This approach provides a novel solution for the precise control of pilot-operated directional valves.

The advent of the industry 4.0 concept has led to the integration of online measurement functions in valves, which provides the system with more status information and enables the realization of intelligent functions. To improve functions, such as condition monitoring and fault diagnosis, in highly reliable hydraulic systems, this article proposes a virtual estimation method of pressure drop at valve ports without additional sensors, which avoid introducing pressure loss and potential failure points. This article presents an online pressure drop estimation method to address this problem by analyzing dynamics in valves. First, flow force is found the most significant term related to pressure drop. Both flow force and unmodelled term are obtained using a disturbance observer to build an accurate pressure-dependent integrated flow force model. Based on this model, the pressure drop is then estimated using a parameter estimation algorithm using the principle of immersion and invariance. The effectiveness of the proposed estimation method is finally validated through experimental setups under different working conditions, concluding with a performance analysis and insightful discussions.

Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque (more than 100 kN m). A multi-row cam roller bearing (MCRB) is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor. However, compact geometry and complex loads render MCRB susceptible to fatigue failure, highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability. Therefore, this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life. In this method, a quasi-static model was developed to calculate the load distribution, with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution. Subsequently, a genetic algorithm was used to obtain the optimized geometry parameters, which significantly improved the fatigue life of the MCRB. Finally, a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method. This study provides a theoretical guideline for optimizing the design of MCRB, thereby increasing the fatigue life of hydraulic motors.

High-end equipment always operate in low-speed and heavy-load working environments, highlighting the need for cam-lobe hydraulic motors with excellent speed stability (< 1 r/min) and ultrahigh-power rotary output (> 1 MW). The successful operation of cam-lobe hydraulic motors relies on the circulation supply of high- and low-pressure oil. However, the switching between high-/low-pressure oil controlled by the oil distributor inevitably causes an obvious pressure impact and speed pulsation, which directly reduces the speed stability of hydraulic motors. Therefore, an optimization design approach for the oil distributor port is proposed to minimize the speed pulsation of cam-lobe hydraulic motors. In the proposed approach, a simulation model that links the oil distributor port structural parameters with the hydraulic motor speed pulsation was developed to clarify the effect of the oil distributor structural parameters on speed pulsation. Then, an orthogonal analysis method was used to identify the optimized oil distributor port structural parameters while minimizing the hydraulic motor's speed pulsation as much as possible. Finally, several experiments were conducted to validate the effectiveness and accuracy of the proposed optimization design approach. The experimental results indicate that the pulsation rate of the hydraulic motor equipped with the optimized oil distributor was 62.5% lower than that of the original motor at a working pressure of 25 MPa, which is consistent with the simulation results using the proposed optimization design approach. The findings of this study offer a feasible and effective approach to guide the design optimization of the oil distributor port for low-pulsation hydraulic motors.

Hydraulic actuated quadruped robots have bright application prospects and significant research values in unmanned area investigation, disaster rescue and other scenarios, due to the advantages of high payload and high power to weight ratio. Among these fields, inevitable collision of robots may occur when contact with unknown objects, step on empty objects, or collapse, all of which have an impact on the working hydraulic system. To overcome the unknown external disturbances, this paper proposes an active disturbance rejection control (ADRC) strategy of double vane hydraulic rotary actuators for the hip joints of the quadruped robots. Considering the order of the valve-controlled actuator model, a three-stage tracking differentiator, a four-stage extended state observer, and a state error feedback controller are designed relatively, and the extended state observer is adopted to observe and compensate the uncertainty of external load torque of the system. The effectiveness of the ADRC method is verified in simulation environment and a single joint experimental platform. Moreover, the impact experiments of the limb leg unit are carried out after introducing the proposed ADRC strategy into hip joint, the limb leg unit of quadruped robots presents better impact resistance ability.

Servo-proportional valves are gradually being introduced into aircraft electro-hydraulic systems as performance improves. Reducing the flow force of the valves is beneficial in improving the rapidity and stability of valve operation. Meanwhile, maintaining the flow linearity of the valves in the structural design can prevent the reduction of the stability margin of the load system flow control. Therefore, a non-throttling port spool guide bevel is designed to reduce the flow force based on the relationship between the jet angle and the flow force. A step structure is designed to maintain the flow linearity and alleviate the flow force reversal problem. To obtain the best parameters of the structure, a joint optimization simulation platform is built by combining the CFD (Computational Fluid Dynamics) technique and a multi-objective genetic algorithm. Finally, the simulations show that the optimized spool structure can reduce the overall flow force by 37.3% and the maximum flow force by 28.5%, while the flow linearity is basically unchanged.

Due to the wide working range of the proportional servo valve (PSV), the flow force changes greatly with the load pressure drop, which significantly affects the precise control of the valve spool position of the PSV. An adaptive sliding mode control based on the immersion and invariance principle (ASMCII) is designed in this paper to solve this problem. The load pressure drop is adaptive to the pressure senseless PSV, and then the ASMCII is used to achieve high precision control. Firstly, the dynamic model of PSV system under unknown large flow force disturbances is established, and the sliding mode control strategy based on reaching law is designed and applied. Secondly, in the design of disturbance estimation error manifold, the immersion and invariance principle (I&I) are applied to ensure the estimation error of load pressure drop converges to 0, for the sake of the accurate estimation of flow force. Finally, the stability analysis and simulation of the system are carried out. The results show that under the simulation conditions of 0–35 MPa, ASMCII converges uncertain pressure drops quickly to compensate flow force completely, which promotes both static and dynamical performance significantly contrast to PID and the sliding mode control.

Increasing the rotating speed is considered as an efficient approach to upgrade the power-to-weight ratio in an axial piston pump, but penalized by more leakage and more severe wear resulting from the adverse cylinder block tilt. Previous studies mainly focused on the bearing characteristic of the valve plate/cylinder block pair, but the spline coupling also plays a key role in the undesired cylinder block tilt, which has been little studied. A theoretical model for the rotating assembly is presented to investigate the effect of the spline coupling length on the cylinder block tilt and the performance of the valve plate/cylinder block pair. A typical high-speed axial piston pump with the displacement of 5.2 mL/r at 10,000 r/min was studied by simulation and experiment. It shows that the optimal spline coupling length is one value increased by 2 mm from the original, bringing a remarkable leakage reduction under the high-speed condition by decreasing the cylinder block tilting angle. The experiment result matches well with the simulation. The influences of the spline coupling on the cylinder block tilt and the leakage were demonstrated.

重载冗余机械臂具有动作灵活,载重大等特点,非常适合消防、地震救援等复杂现场.然而,现有机械臂控制方式存在控制难度大、硬件要求高、控制效果差等问题.目前,针对这些问题的有效控制方式是末端控制,对此,分析了两种面向机械臂末端进行速度控制的算法——梯度投影法和分解速率法.针对重载冗余机械臂进行数学建模,运用MATLAB对两种控制算法进行了仿真验证,并比较了两种算法的可操作性.分析结果表明,梯度投影法和分解速率法总体上都能较好实现重载冗余机械臂的控制,分解速率法在误差控制方面更好,而梯度投影法在可操作性方面更强.这两种末端控制算法为下一步建立双臂重载救援机器人的操控策略和实际的应用末端控制提供了理论基础.

Increasing the rotating speed of the axial piston pump is effective in improving the power-to-weight ratio. However, the cylinder block tilts severely at high speed, which causes significant leakage. In this paper, a dynamic model of the rotating assembly in a high-speed axial piston pump is established to investigate the tilt behavior of the cylinder block when fully considering the relevant factors within the whole rotating assembly, such as the tilt moments due to the inertia of piston-slipper assemblies and the periodic pressure in piston chambers, the elastic deformation of the shaft, and the nonlinear bearing characteristics of the oil film. Furthermore, the cylinder block tilt behavior is measured to validate the established dynamic model. The theoretical and experimental results show that the tilt angle of the cylinder block increases with the increasing rotating speed. And at high rotating speed, the cylinder block tilts much more severely under low outlet pressure. Finally, the bearing capacities of the oil film and the spline coupling are analyzed to find out the dominant factors affecting the tilt behavior of the cylinder block.

灾难救援机器人能够在危险环境下代替人类实施救援任务,由于灾害现场复杂多变,空间紧张,救援机器人往往需要在重载条件下进行工作.大型液压机械臂末端夹持装置,存在阻尼低、刚度弱、易振荡等固有缺陷,且夹持装置直接与环境接触,其耦合规律复杂,阻尼/刚度性能难以精细调控,夹持装置不能实现柔顺控制,极大限制了机械臂与环境的交互,甚至会造成人员伤亡和财产损失.采用阻抗控制中的导纳控制,对救援机器人的末端液压夹持装置进行柔顺控制,通过AMESim-Simulink联合仿真平台,搭建夹持装置模型进行仿真验证.仿真结果表明,采用导纳控制器的夹持装置与环境柔顺交互,取得了较好的控制效果.

研究了比例伺服阀的阀芯结构对液动力的影响,提出了一种阀芯导流壁面优化设计方案.采用计算流体力学(CFD)的方法建立滑动网格模型,分别对阀芯传统导流结构和优化设计后的导流结构进行数值模拟分析,并验证了网格无关性.对阀芯所受稳态液动力进行数值求解,并分析了不同优化设计方案对阀口处流体流动状态的影响.结果表明,优化设计后的阀腔内部流场分布更均匀,流动状态更平稳;阀芯内流道导流结构会改变阀口处的介质流向,进而改变进出口流体水平方向上的动量差,以补偿部分液动力;与传统方案相比,液动力最大补偿效果可达60％,显著降低了阀芯所受液动力干扰,有利于提升比例伺服阀的静动态控制性能.

Well-designed surface textures can improve the tribological properties and the efficiency of the electro-hydrostatic actuator(EHA)pump under high-speed and high-pressure conditions.This study proposes a multi-objective optimization model to obtain the arbitrarily surface textures design of the slipper/swash plate interface for improving the mechanical and volumetric efficiency of the EHA pump.The model is composed of the lubrication film model,the component dynamic model considering the spinning motion,and the multi-objective optimization model.In this way,the arbitrary-shaped surface texture with the best comprehensive effect in the EHA pump is achieved and its positive effects in the EHA pump prototype are verified.Experimental results show a reduction in wear and an improvement in mechanical and volumetric efficiency by 1.4％and 0.8％,respectively,with the textured swash plate compared with the untextured one.

在电液比例伺服阀中,液动力具有较强的非线性,开环控制下驱动电流与阀芯位移的线性度较差,使用传统PID控制算法难以达到良好的控制效果.针对该现象,在分析阀芯液动力特性的基础上,提出了一种位置负反馈式的控制方法.通过搭建比例伺服阀的控制器模型和阀芯受力模型,开展实验验证.结果表明,该方法能够有效地解决控制中电流—阀芯位移的非线性问题,控制稳定性有明显提升.

As a type of hydraulic rotary actuator, a helical hydraulic rotary actuator exhibits a large angle, high torque, and compact structure; hence, it has been widely used in various fields. However, its core technology is proprietary to several companies and thus has not been disclosed. Furthermore, the relevant reports are primarily limited to the component level. The dynamic characteristics of the output when a helical rotary actuator is applied to a closed-loop system are investigated from the perspective of driving system design. Two main aspects are considered: one is to establish a reliable mathematical model and the other is to consider the effect of system parameter perturbation on the output. In this study, a detailed mechanical analysis of a helical rotary hydraulic cylinder is first performed, factors such as friction and load are considered, and an accurate dynamic model of the actuator is established. Subsequently, considering the nonlinear characteristics of pressure flow and the dynamic characteristics of the valve, a dynamic model of a valve-controlled helical rotary actuator angle closed-loop system is described based on sixth-order nonlinear state equations, which has never been reported previously. After deriving the system model, a sensitivity analysis of 23 main parameters in the model with a perturbation of 10% is performed under nine operating conditions. Finally, the system dynamics model and sensitivity analysis results are verified via a prototype experiment and co-simulation, which demonstrate the reliability of the theoretical results obtained in this study. The results provide an accurate mathematical model and analysis basis for the structural optimization or control compensation of similar systems.

A microfluidic passive valve (MPV) is important for precise flow control, and it determines the reliability of the microfluidic system. In this paper, a novel MPV capable of delivering a constant flow rate independently of inlet pressure changes is proposed. The flow rate of the MPV is adjusted by the difference between the fluid force on the upper surface of the valve core and the spring force. The constant flow rate of the MPV is maintained by automatically changing the size of the gap channel formed by the groove on the valve core and the baffle on the valve body. The nearly constant flow rate of the MPV is 6.26 mL/min, with a variation of 6.5% under the inlet pressure varied from 1.25 kPa to 3.5 kPa. In addition, the flow characteristics of the MPV are analyzed by numerical simulation. With the increase in the inlet pressure, the maximum velocity gradually increases, while the increment of the maximum velocity decreases. In the movement process of the valve core, the region of pressure drop becomes larger. This work has a certain reference value for the design and research of the MPVs with high throughput liquid delivery.

混凝土布料机的控制现状多为人工牵引及单关节遥控,工人工作条件艰苦,具有安全隐患.为实现混凝土布料机械臂的末端轨迹控制,即全自动布料,提出一种基于姿态枚举算法的机械臂轨迹控制方法.该方法适用于具有多自由度的布料机械臂,首先将目标轨迹离散化为各个离散点,利用运动学逆解模型,通过给定初始布料倾角,并按一定步长对该倾角进行枚举求解,得到各关节角度值,实现轨迹跟踪.针对某13m-3Z型混凝土布料机械臂,建立了多自由度混凝土布料臂架的运动学模型,并采用该方法控制其末端轨迹.通过联合仿真分析,得到臂架末端轨迹曲线图以及布料倾角变化曲线图.结果证明,该方法下布料倾角变化量减少了30.8％,较好的解决了末端软管径向甩动的问题.

The cylinder block is the main rotating part in axial piston pump, and its dynamic characteristics can reflect the health condition of the pump more directly than the external characteristics. In this paper, a less modification measurement scheme is proposed to acquire the dynamic characteristics of the cylinder block accurately. The less modified pump minimizes the influence of the test equipment on the cylinder block motion. The radial displacements of the cylinder block surface in two cross-sections along the perpendicular directions are measured under different operating conditions. Moreover, the translational motion and the tilt behavior of the cylinder block are calculated when the run-out signals of the cylinder block surface are removed from the measurement signals. The vibration signals are measured synchronously and compared with the movement of the cylinder block. Finally, the dynamic characteristics of the cylinder block under different operating pressure are presented and analyzed in detail.

The technology for stepper drive that can achieve accurate motion in the hydraulic field has always been urgently needed in the industry. This paper proposes a hydraulic stepper drive based on five high speed on/off valves and two miniature plunger cylinders. The stepper drive discretizes the continuous flow medium into fixed small steps through the miniature plunger cylinder and realizes the state control of the drive through the logic action of the high speed on/off valve. This paper improves the current stepper drive and establishes a mathematical model to analyze the error of the drive and calculate the position of the actuator. In addition, through simulation research, the performance parameters such as the single-step step characteristic and pressure characteristic of the stepper drive are studied. The results show that, compared with the technology of current stepper drive, this stepper drive can effectively remove the “post step” phenomenon, greatly improve the stepper accuracy of the stepper drive, and have a more excellent performance.