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The output feedback signal of the electro-hydraulic valve system (EHVS) affects the activation of its right or left envelope function; thus, even weak measurement noise can cause high-frequency switching between the two envelope functions, leading to chattering in the control input. Consequently, feedforward and feedback controllers in a cascaded configuration generate undesirable chattering in the output signal. We propose a practical and reliable control approach for an EHVS actuated by a proportional control valve. The proposed controller has a parallel structure comprising an inverse generalized Prandtl–Ishlinskii (P–I) model-based feedforward controller, with both hydraulic dead-zone and flow saturation limits, for compensating asymmetric hysteretic behavior. Further, the proposed controller comprises a robust proportional-integral-derivative (PID) feedback controller for achieving robustness against disturbances and noises. The proposed parallel structure is independent of the output feedback of the EHVS. Moreover, the proposed robust PID feedback controller guarantees EHVS stability by precisely selecting the cutoff frequency for the sensitivity and complementary sensitivity functions based on the amplitude spectrum of the inverse-model-based feedforward compensation error. The results verify the high reliability of the proposed EHVS control scheme for the precise control of an EHVS actuated by a proportional control valve in practice.

In the field of fully mechanized coal mining equipment, the hydraulic valve used in the hydraulic support is an on/off directional valve. There are many problems caused by the valve such as large pressure shock and discontinuous flow control. Therefore, a novel two-position three-way hydraulic proportional valve suitable for high-pressure and large-flow conditions is proposed to overcome the above problems. The novel valve utilizes a two-stage structure and the displacement follow-up principle is adopted between the pilot stage and the main stage to meet proportional control. In this paper, a simulation model of the novel proportional valve was established after a simplified analysis of the structural principle. Its reliability and the feasibility of the design were verified by the test results under different working conditions. Then, the step response characteristics of the proportional valve under different strokes were predicted and analyzed. Nonlinear characteristics were presented, and the closing time was shorter than the opening time because of the influence of nonlinear flow force. Under different ramp signals, the displacement of the main inlet spool was always approximately equal to the displacement of the pilot stage. Then, the motion relationship between the pilot stage and the main stage was studied, and the influence of the structural parameters on the stability was analyzed.

The motion axis of a computer numerical control (CNC) machine tool is mainly composed of a permanent-magnet synchronous motor (PMSM), ball screw, and moving table so that the motion axis can be practically modeled as a two-mass mechanical system. However, the proportional (P)–proportional integral (PI) (P–PI) control design, which is extensively used in commercial PMSM drivers, generally considers the motion axis as a single-mass mechanical system, thereby limiting the cornering motion performance of the CNC machine tool. In this study, the motion axis is modeled as a two-mass mechanical system, and the P–PI control parameters are designed and adjusted to reduce cornering errors during linear cornering motions. The two-mass equivalent system is first derived from the motion axis model, and the pole assignment method is used to design the proportional and integral control parameters such that the PMSM velocity responses have short rise times and small overshoots. Thereafter, particle swarm optimization is applied to adjust the proportional control parameter to further reduce the cornering errors using an objective function with weighted errors. The results of experiments performed with a CNC lathe show that the cornering errors of the test path could be reduced by 30%, thus validating the feasibility and performance of the P–PI control parameter design and adjustment method developed herein.

To address the alignment difficulties in precision assembly, this paper designs an adaptive position correction system. The system integrates electromagnetic proportional control technology to optimize the alignment mechanism, making its floating range linearly adjustable. This solution overcomes the issue of incompatible alignment mechanisms for workpieces of different sizes, providing a new approach to solving position deviation problems in precision assembly.

Available hydropneumatic suspension simulation test benches have insufficient loading accuracy and limited functionality rendering them unsuitable for performance testing of heavy vehicles with this type of suspension. Therefore, a multi-functional compound simulation test bench was designed that used an electro-hydraulic proportional control technique. A mathematical model was established to describe the hydraulic loading system, and the transfer function of the system was derived. The gain and phase margins confirmed the stability of the system. A simulation model was established in the Simulink environment and step and sine signals of different frequencies were applied separately to analyze the dynamic characteristics of the system. The results showed that the system responded slowly and exhibited phase lag and signal distortion. The dynamic characteristics of the system were improved by incorporating an adaptive fuzzy PID controller. Simulation results showed that the response of the system to the step signal stabilized at the preset value within 0.3 s with no oscillation or overshoot. The improved system performed well in replicating the random vibrations of heavy vehicles operating on Class B and C roads. This confirmed that the system can satisfy the loading requirements of heavy vehicle hydropneumatic suspensions and can be used as a simulation test bench for such suspensions.

This paper presents mathematical models of flow through electropneumatic valve, it is an analysis of existing publications by various authors. The presented models are discussed and described in detail and the conditions for their application to different types of electropneumatic valve designs are presented. Graphical relationships showing the flow through the valves are presented.

This paper investigates the proportional‐integral‐derivative (PID) control of positive systems in the discrete‐time case. First, a tuning parameter is introduced to construct the proportional‐integral‐derivative control framework of positive systems. The proportional‐integral‐derivative control problem is thus transformed into the control synthesis of positive systems with time‐delay. By virtue of a matrix decomposition approach, the gain matrices of proportional‐integral‐derivative controller are designed. Using co‐positive Lyapunov functions and linear programming, the positivity and stability of positive systems are achieved under the designed proportional‐integral‐derivative controller. Then, the proportional‐integral‐derivative control of positive systems with reference signal is solved. The main contribution of this paper lies in that linear programming associated to the matrix decomposition approach is first presented to handle the proportional‐integral‐derivative control of positive systems. Finally, two illustrative examples are provided to verify the effectiveness of the proposed design. A linear programming‐based proportional‐integral‐derivative control framework is constructed for positive systems. A matrix decomposition approach is presented for describing the controller gains.

Considering the complexity and difficulty of obtaining certain parameters in the electro-hydraulic proportional control system, a precise transfer function of the system was derived through parameter identification using experimental data obtained from an Amesim simulation model after establishing a basic mathematical model. This approach reduces the reliance on accurate parameters of individual components. A feedforward-feedback composite controller was designed, and its effectiveness was validated in Simulink using the system’s transfer function. Subsequently, the dead zone range of the proportional valve was determined through experiments, and a dead zone compensation strategy was designed, which reduced the time required for the proportional valve to traverse the dead zone by 89.4%. Based on the dead zone compensation, trajectory tracking experiments were conducted to validate the effectiveness of the feedforward-feedback composite controller. Under fixed disturbances, the trajectory tracking error was reduced by 53.8% compared to feedback control. Under time-varying load disturbances, the trajectory tracking error was reduced by 51.2% compared to feedback control.

A battery charger for solid-state lithium battery packs was developed and implemented. The power stage used a phase-shifted full-bridge converter integrated with a current-doubler rectifier and synchronous rectification. Dual voltage and current control loops were employed to enable constant-voltage and constant-current charging modes. To improve the lifespan of the output filter capacitor, the current-doubler rectifier was adopted to effectively reduce output current ripple. During the initial start-up phase, as the charger transitions from constant-voltage to constant-current output mode, the use of proportional–integral control in the voltage and current loop error amplifiers may cause current overshoot during the step-rising phase, primarily due to the integral action. Therefore, this study incorporated fuzzy control, proportional control, and proportional–integral control strategies into the current-loop error amplifier. This approach effectively reduced the current overshoot during the step-rising phase, preventing the charger from mistakenly triggering the overcurrent protection mode. The analysis and design considerations of the proposed circuit topology and control loop are presented. Experimental results agree with theoretical predictions, thereby confirming the validity of the proposed approach.

Electromyographic (EMG) signals from muscles in the body torso are often contaminated by electrocardiography (ECG) interferences, which consequently compromise EMG intensity estimation. The ECG interference has become a barrier to proportional control of myoelectric prosthesis using a neural machine interface called targeted muscle reinnervation (TMR), which involves transferring the residual amputated nerves to nonfunctional muscles (typically pectoralis muscles for high level amputations). This study investigates a novel approach toward implementation of proportional myoelectric control by applying sample entropy (SampEn) analysis of surface EMG signals for robust intensity estimation in the presence of significant ECG interference. Surface EMG data from able-bodied and TMR amputee subjects with different degrees of ECG interference were used for performance evaluation. The results showed that the SampEn analysis had high correlation with surface EMG amplitude measurement but low sensitivity to different degrees of ECG interference. Taking this advantage, SampEn analysis of surface EMG signal can be used to facilitate implementation of proportional myoelectric control against ECG interference. This is particularly important for TMR prosthesis users.