Qiang Gao

With the growth of the global population and the increasing scarcity of arable land, traditional agricultural production is confronted with multiple challenges, such as efficiency improvement, precision operation, and sustainable development. The progressive advancement of artificial intelligence (AI) technology has created a transformative opportunity for the intelligent upgrade of agricultural equipment. This article systematically presents recent progress in computer vision, machine learning (ML), and intelligent sensing. The key innovations are highlighted in areas such as object detection and recognition (e.g., a K-nearest neighbor (KNN) achieved 98% accuracy in distinguishing vibration signals across operation stages); autonomous navigation and path planning (e.g., a deep reinforcement learning (DRL)-optimized task planner for multi-arm harvesting robots reduced execution time by 10.7%); state perception (e.g., a multilayer perceptron (MLP) yielded 96.9% accuracy in plug seedling health classification); and precision control (e.g., an intelligent multi-module coordinated control system achieved a transplanting efficiency of 5000 plants/h). The findings reveal a deep integration of AI models with multimodal perception technologies, significantly improving the operational efficiency, resource utilization, and environmental adaptability of agricultural equipment. This integration is catalyzing the transition toward intelligent, automated, and sustainable agricultural systems. Nevertheless, intelligent agricultural equipment still faces technical challenges regarding data sample acquisition, adaptation to complex field environments, and the coordination between algorithms and hardware. Looking ahead, the convergence of digital twin (DT) technology, edge computing, and big data-driven collaborative optimization is expected to become the core of next-generation intelligent agricultural systems. These technologies have the potential to overcome current limitations in perception and decision-making, ultimately enabling intelligent management and autonomous decision-making across the entire agricultural production chain. This article aims to provide a comprehensive foundation for advancing agricultural modernization and supporting green, sustainable development.

With the frequent occurrence of global floods, the demand for emergency rescue equipment has grown rapidly. The development and technological innovation of digital hydraulic drive systems (DHDSs) for emergency drainage pumps (EDPs) have become key to improving rescue efficiency. However, EDPs are prone to being affected by random and uncertain loads during operation. To achieve intelligent and efficient rescue operations, a DHDS suitable for EDPs was proposed. Firstly, the configuration and operation mode of the DHDS for EDPs were analyzed. Based on this, a multi-field coupling dynamic simulation platform for the DHDS was constructed. Secondly, the output characteristics of the system under alternating loads were simulated and analyzed. Finally, a test platform for the EDP DHDS was established, and the dynamic characteristics of the system under alternating loads were explored. The results show that as the load torque of the alternating loads increases, the amplitude of the pressure of the motor also increases, the output flow of the hydraulic-controlled proportional reversing valve (HCPRV) changes slightly, and the fluctuation range of the rotational speed of the motor increases. The fluctuation range of the pressure and the rotational speed of the motor are basically not affected by the frequency of alternating loads, but the fluctuation amplitude of the output flow of the HCPRV reduces with the increase in the frequency of alternating loads. This system can respond to changes in load relatively quickly under alternating loads and can return to a stable state in a short time. It has laudable anti-interference ability and output stability.

High-speed on/off valves (HSVs) play an important role in digital hydraulic systems, and their dynamic performance directly affects the control accuracy of actuators. However, because of the inherent lag caused by a coil with many turns, a conventional HSV driven by a single coil does not achieve the best dynamic performance. In this study, an HSV driven by multiple coils discretized in the axial dimension (HSV-MCDAD) is proposed. A multifield-coupled dynamic model was developed, and its dynamic characteristics were determined. Moreover, an acoustic-vibration fusion-based measurement method was developed to detect the switching behavior of the HSV-MCDAD, which was shown to have the same accuracy as the coil current test method. The influence of the enabled state combinations of different coils on the dynamic performance was analyzed. Accordingly, a combination drive strategy is proposed to optimize the selection of multiple coils during different moving stages. Experiments indicated that the total opening and closing times of the HSV-MCDAD were reduced by 10.3% and 59.5%, respectively, compared to those of an HSV driven by a single coil. The proposed combination-drive strategy results in a higher and more stable dynamic performance of the HSV-MCDAD for different frequencies.

Two-stage proportional valves (TSPV) have been used extensively for electro-hydraulic control systems with large-flow applications. Due to the inherent characteristics of the pilot spool, such as hysteresis, motion quality, and dead zone, the dynamic performance of the traditional TSPV cannot be further improved. To solve this issue, this paper proposes a high-frequency two-stage proportional valve (HFTSPV) piloted by two high-speed on/off valve arrays, which integrates the advantages of dual nozzle flapper mechanism and parallel-connected valve technology. First, an entire mathematical model is established, in which some key parameters are estimated by experiments, such as the actual diameters and flow coefficients of orifices, and flow coefficient of pilot valve. Then, the influences of fixed orifices with different diameters on the dynamic characteristics of main spool are explored. Subsequently, the optimal diameter of fixed orifice is calculated theoretically by using the maximum pressure sensitivity and flow linearity, aiming to realize the high dynamic and small displacement fluctuation. Finally, step and sinusoidal tracking experiments show that the delay time of the HFTSPV is close to 3.3 ms, and the displacement fluctuation decreases with the increase of tracking frequency. Amplitude–frequency results indicate that −3 dB frequency of the HFTSPV reaches 16 Hz under ±50% full scale and 30 Hz under 0% –50% full scale.

High speed solenoid valves (HSVs) have often been used in the pilot stage of a two-stage proportional valve to control the main spool's position, in which the vibration and dynamic performance of the pilot HSV need to be optimized, such as low vibration, low noise, and fast response. In this paper, an improved PWM controller for landing velocity reduction in a HSV during the excitation stage is proposed to reduce the vibration and maintain the dynamic performance under different supply pressures. First, the working principle of the proposed PWM signal is presented and the dynamic behavior of the HSV is analyzed during the excitation stage. Secondly, the influences of the two timing parameters (the time when the negative voltage begins and ends) and the hydraulic supply pressures on the performance of the HSV are analyzed. Moreover, two design criteria of the timing parameters are proposed and a direct searching algorithm is proposed to find an optimal solution set. The optimization results not only show that a good compromise between the landing velocity and the total opening time can be achieved but also proves that the reverse motion of the ball valve is effectively eliminated. Finally, comparative results indicate that with the proposed PWM control, the maximum impact acceleration is reduced by at least 44.7% and the delay of total opening time is always less than 0.3 ms under different supply pressures except 1 MPa, compared to the compound PWM control (full positive voltage in the excitation stage). The proposed PWM is simple and can be used in the HSV-controlled system to reduce the vibration and improve the accuracy of the actuator.

The reliability and control precision of the engagement and disengagement of wet friction clutch are crucial to the transmission of high-speed helicopters. In contrast to the traditional proportional hydraulic system, the digital hydraulic system provides a viable solution due to the use of several fast switching valves (FSVs). In this research, a digital hydraulic pressure tracking system using two fast switching valve arrays (DHPTS-FSVA) is proposed and its nonlinear model is established. First, the static and dynamic characteristics of the DHPTS-FSVA are deeply analyzed by virtue of the half-bridge resistance theory. Moreover, a novel pressure control strategy is proposed, which consists of nonlinear adaptive control method, differential pulse width modulation (PWM) with pressure compensation, and logic allocation strategy of PWM duty ratio. Finally, comparative simulation and experimental results indicate that the maximum, average, and standard deviation of the errors are reduced by at least 16.1%, 45.1%, and 39.5%, respectively, at the tracking frequencies of 1 and 2 Hz, which proves that the proposed controller exhibits better tracking performance at low frequencies.

Fluid components and systems are major components of modern mechanical equipment and have been widely used in various fields such as engineering machinery, rotating machinery, and hydraulic machinery

The effective way to improve the reliability of the fuel metering system in an aero-engine is to use a high-speed on/off valve (HSV) instead of a servo valve as the pilot stage of the fuel metering valve. However, the dynamic performance of the fuel metering valve is easily affected by the HSV, so a novel two-stage high-speed on/off valve with adjustable maximum opening (AMOHSV) is proposed in which the maximum stroke of the main valve is regulated with an adjustable rod. Firstly, the structure and working principle of the proposed valve are presented. Then, an entire mathematical model is established and verified based on a multi-physical field coupling mechanism. Finally, simulations and experiments prove that when the maximum opening is 0.2 mm, the total opening time and total closing time of the AMOHSV are within 5 ms. In addition, an upward inflection point and a downward inflection point on the pressure curve of the control chamber can be used to identify the total opening time and total closing time, respectively. The research results also prove that the proposed structure solves the conflict between the maximum flow rate and the dynamic performance of the traditional HSV.