The variable displacement pump control system has greater energy-saving advantages and application prospects than the valve control system. However, the variable displacement pump control of differential cylinder is not concurrent with the existing technologies. The asymmetric pump-controlled cylinder is, therefore, used to balance the unequal volume flow through a single rod cylinder in closed-circuit system. This is considered to be an effective method. Nevertheless, the asymmetric axial piston pump (AAPP) is a constant displacement pump. In this study, variable-displacement asymmetric axial piston pump (VAPP) is investigated according to the same principle used in investigating AAPP. This study, therefore, aims at investigating the characteristics of VAPP. The variable-displacement output of VAPP is implemented by controlling the swash plate angle with angle feedback control circuit, which is composed of a servo proportional valve and an angular displacement sensor. The angular displacement sensor is connected to the swash plate. The simulation model of VAPP, which is set up through the ITI-SimulationX simulation platform, is used to predict VAPP’s characteristics. The purpose of implementing the experiment is to verify the theoretical results. Both the simulation and the experiment results demonstrated that the swash plate angle is controlled by a variable mechanism; when the swash plate angle increases, the flow of Port B and Port T increases while the response speed of Port B and Port T also accelerates. When the swash plate angle is constant, the flow of Port B and Port T increases along with the increase of pump speed, although the pressure-response speed of Port B is faster than that of Port T. Consequently, the flow pulsation of Port B and Port T tends to decrease gradually along with the increase of pump speed. When the pressure loaded on Port B equals to that of Port T, the flow ripple cycle of Port B is longer than that of Port T, whereas the peak flow of Port B is higher than that of Port T. Since the flow ripple of Port T is bigger than that of Port B, Port T should be connected to the low pressure sides or the oil tank so that it does not affect VAPP’s performance. Further, to avoid the backflow of VAPP from Port T to Port B, Port T cannot be loaded alone, and the loading pressure of Port T also cannot exceed that of Port B.

Aiming at the problems of complex operating conditions, large load disturbance, strong coupling of pressure and position control subsystems, and time-varying parameters of independent metering electro-hydraulic servo system (IMEHSS), an active disturbance rejection decoupling (ADRC) control method with online compensation information is proposed in this paper. In this study, the internal coupling of subsystems is treated as the part of total disturbances, and decoupling control is realized by estimating and compensating the total disturbance through extended state observer. In position control subsystem, the cylinder dynamic changes caused by the inlet chamber flow rate of cylinder and the deviation of the nominal calculated flow rate from actual calculated flow rate are calculated in real time. And these calculated values are compensated to the controller as online information to improve the control accuracy and the disturbance rejection ability of position control. By calculating the cylinder velocity in real time to obtain the effect of cylinder speed on the change of return chamber pressure and compensating it into the controller to improve the return chamber pressure control accuracy. The online information compensation method presented in this paper reduces the amount of total disturbance and thus reduces the burden of extended state observer. At the same time, this method can realize the proportional relationship between the regulation parameters and control signals in the passive pressure control subsystem, which simplifies the tuning process of parameters. Finally, to verify the effectiveness and rationality of the method, simulations and experiments are carried out.

To address significant pressure fluctuations in anchor drilling machine systems during the drilling and anchoring support of complex coal roadway surrounding rock, a variable universe fuzzy PID control strategy was proposed to regulate the speed of the servo motor. Additionally, a pump-controlled pressure approach was introduced to further reduce throttling losses and energy consumption. To validate the proposed algorithm, disturbances were simulated by adjusting the opening size of a three-position four-way proportional directional valve. A co-simulation model was first established using AMESIM 2020.1 and SIMULINK R2022a software, followed by experimental verification and comparison with conventional PID control. The experimental results demonstrated that when the system pressure signal was set to a constant value, the proposed algorithm reduced the pressure error by approximately 36.5% compared to PID control. For step pressure inputs, the algorithm decreased the response time and overshoot by 6.8–8.2% and 10.3–16.2%, respectively, under different valve openings. Furthermore, when the system pressure followed various sinusoidal signals, the proposed algorithm exhibited lower pressure error and faster response times than PID control. This study provides theoretical and experimental references for maintaining stable pressure during the operation of anchor drilling machines, offering an efficient and reliable control solution for complex drilling environments.

Hydraulic systems are widely used in construction machinery and equipment. However, the energy efficiency of hydraulic system is low. In many cases, hydraulic systems output energy to lift the working device. During the lowering process, the potential energy is commonly wasted through the throttling loss of the control valve. Recovering the potential energy is an efficient way to improve the hydraulic system efficiency. In this article, theoretical analysis, simulation calculation, and experimental verification were used to study the energy recovery efficiency of a differential cylinder system controlled by variable displacement asymmetric axial piston pump. Meanwhile, the influence of the load, motor speed, variable displacement asymmetric axial piston pump swashplate angle, accumulator pressure and capacity, and other key parameters on the potential energy recovery efficiency and system performance was analyzed. The results show that the system energy consumption can be reduced effectively by using the potential energy recovery system. When the load, motor speed, pre-charge pressure and capacity of the accumulator, and swashplate angle are 440 kg, 1000 r/min, 2.5 MPa, 1.6 L, and ±5°, respectively, the system’s energy-saving effect can be up to 39.25%. Considering that only the vertical motion of the differential cylinder controlled by variable displacement asymmetric axial piston pump was analyzed, in future work, the corresponding parameter optimization and control strategy will be carried out to obtain good energy recovery effect, and the influence of accumulator pre-charge pressure on the energy-saving effect will be conducted.

Aiming at the oscillation caused by the hydraulic cylinder of independent metering system (IMS) running between multiple working quadrants, a novel multiple quadrants switching displacement tracking control strategy is proposed in this paper. In this control strategy, both the cylinder chamber pressure under resistance and overrunning conditions are controlled by the inlet valve, and the outlet valve is utilized to control the displacement of cylinder. This method allows the hydraulic cylinder to always run in energy-efficient. When the working quadrant changes, the valve’s working modes are unchanged, which avoids oscillation caused by changes of valves working modes in principle. And a reduced-order active disturbance rejective displacement controller and an active disturbance rejective pressure controller are designed to get high-precision tracking of the displacement and pressure. Numerous experimental results show that the proposed method is reasonable and effective, hydraulic cylinder operates smoothly between multiple quadrants, the pressure and displacement controllers have good anti-interference ability and robustness, and the energy consumption can be reduced by more than 23% compared to the traditional constant pressure valve control system.