Electro-hydraulic Proportional System Research Articles

Nonlinear adaptive robust control with continuous error reduction mapping

Abstract Achieving high stability and high-precision control by traditional control algorithms is difficult due to the strong nonlinearity, parameter uncertainty, and random disturbance characteristics of electro-hydraulic proportional servo systems. Herein, we developed a nonlinear adaptive control algorithm based on Lyapunov functions. By estimating the parameters and converging their errors, this algorithm solved the parameter adaptation problem. Additionally, based on convergence inference from the nonnegativity of the derivative of Lyapunov functions, the algorithm designed a disturbance mapping through the derived function. The random disturbance was reduced through the mapping, improving the stability of the system under random disturbance. Finally, we carried out continuous derivation and moved the mapping relationship out of the intermediate temporary controller. This reduced the complexity of the calculation during controller design, prevented performance degradation of the error convergence algorithm after complex calculation, and enhanced the robustness of the algorithm. The algorithm was verified through the simulation model established by Simulink and experience. Results showed that the nonlinear adaptive control algorithm demonstrates fast response, high accuracy, and strong anti-interference ability compared with the high-gain robust control algorithm. It realizes the adaptation of unknown parameters and reduces the control error introduced by random disturbance.

Friction compensation control method for a typical excavator system based on the accurate friction model

Traditional identification methods make it difficult to accurately determine the parameters of the friction model. Based on the LuGre friction model, a hybrid optimization algorithm (HO) is presented to address such aspects. This algorithm combines the genetic algorithm (GA) and particle swarm optimization algorithm (PSO) to obtain the globally optimal solutions. It incorporates three main improvements: introducing selection and crossover operations into the PSO algorithm, utilizing a variable inertia weight coefficient, and applying variable learning coefficients for enhanced performance. Compared to the static optimal solutions of the GA and PSO algorithms, the HO algorithm can improve the optimal solution by 40.68 % and 35.89 % respectively. The HO algorithm can achieve the highest model accuracy: the maximum identified friction error with the HO algorithm is only 1.70 kN, compared to 3.69 kN with the GA method and 8.52 kN with the PSO algorithm. Furthermore, a novel adaptive friction compensation controller (AC) is introduced based on the identification results to improve the stability and accuracy of the electro-hydraulic proportional systems of a 23-ton robotic excavator. Comparisons with existing proportional integral differential (PID) and feedforward compensation controllers (FC) highlight the superiority of the proposed adaptive controller in terms of trajectory accuracy and robustness. In sinusoidal trajectory tracking experiments, the AC method can achieve the highest tracking performance among the three controllers, and the maximum tracking error is only 11.56 mm. Compared to the FC controller, the control accuracy with the AC controller can be improved by 43.38 %. Experiments and simulations have shown that the friction compensation controller can effectively mitigate friction and other disturbances. As a result, the phenomena of crawling and flat peak phenomena can be eliminated.

Electro-Hydraulic Proportional System Real Time Tracking Control Development Based on Pulse width Modulation Method

The presented work was directed to develop the dynamic performance of an electro-hydraulic proportional system (EHPS). A mathematical model of the EHPS is presented using electro- hydraulic proportional valve (EHPV) by Matlab-Simulink, which facilitates the simulation of the hydraulic behavior inside the main control unit. Experimental work is done and the closed loop system is designed using the linear variable displacement transducer sensor (LVDT). The controller of the system is an Arduino uno, which is considered as a processor of the system. The model is validated by the experimental system. The study also presents a real time tracking control method, based on pulse width modulation, by controlling the speed of the actuator to achieve the position tracking with minimum error and low transient time, by applying the constant input signal 50mm the transient time was 0.9 seconds and the error 1.8%.

Model‐free linear active disturbance rejection output feedback control for electro‐hydraulic proportional system with unknown dead‐zone

Here, a model-free linear active disturbance rejection controller (LADRC) integrating dead-zone inverse compensation for an electro-hydraulic proportional (EHP) system with an unknown dead-zone is proposed. Unlike the existing LADRC design idea, the presented method uses a new hydraulic system block diagram to select the order of LADRC instead of the highest degree of the system. Furthermore, the rationality of order selection is illustrated by the frequency domain analysis theory. To solve the dead-zone of the proportional valve, a novel structural transformation is proposed by constructing a new dead-zone, which has a definite physical meaning and can be obtained by the experimental measurement. Then, the dead-zone disturbance is reduced, and the burden of the observer is relieved. At the same time, the controller parameters are decreased from three to two equivalent PI controller. Besides, the stability of the closed-loop system is analysed by the describing function method. The performance of the proposed control solution has been investigated through extensive comparative experiments under different working conditions. The experimental results successfully demonstrate the effectiveness and practicality of the presented method.

Regulation Method for Torque\u2013Angle Characteristics of Rotary Electric\u2013Mechanical Converter Based on Hybrid Air Gap

The torque–angle characteristics of electric–mechanical converters are important determinants of the quality of electrohydraulic proportional control systems. It is far more difficult for a rotary electric–mechanical converter (REMC) to obtain flat torque–angle characteristics than traditional proportional solenoid, greatly influencing the promotion and application of rotary valves for electrohydraulic proportional control systems. A simple and feasible regulation method for the torque–angle characteristics of REMCs based on a hybrid air gap is proposed. The regulation is performed by paralleling an additional axial air gap with the original radial air gap to obtain a flat torque–angle characteristic and increase output torque. For comparison, prototypes of REMCs based on hybrid and radial air gaps were manufactured, and a special test rig was built. The torque–angle characteristics under different excitation currents and step responses were studied by magnetic circuit analysis, finite element simulation, and experimental research. The experimental results were consistent with the theoretical analysis. It was shown that REMCs based on a hybrid air gap can obtain a flat torque–angle characteristic with further optimizing of key structural parameters and also increase output torque. This regulation method provides a new approach for the design of proportional rotary electromechanical converters.

A multi-switching mode intelligent hybrid control of electro-hydraulic proportional systems

The electro-hydraulic proportional system is a highly non-linear system owing to the fact that the system is composed of components from different disciplines such as electric, hydraulic and mechanical disciplines. In general, a switching-based controller is suitable to the control of such a system. In this paper, a switching-based controller is proposed, which is called multi-switching mode intelligent hybrid control, for electro-hydraulic proportional systems. The novelty of the multi-switching mode intelligent hybrid control is that it integrates the PID control law, the neural-fuzzy control law, and the expert-based control law. To demonstrate the effectiveness of the proposed multi-switching mode intelligent hybrid control, both experiment and simulation were conducted. It is shown that the experimental result corresponds well with the simulation result. Further, the proposed control system was compared with the traditional ones such as PID and neural-fuzzy controller for a trajectory tracking task with an electro-hydraulic proportional, which shows that the proposed one is far superior to these traditional ones. Overall, there is evidence that the proposed multi-switching mode intelligent hybrid control is very effective. It is noted that though the idea of the switching-based control system to electro-hydraulic proportional systems may not be new, the specific integration of the member control laws along with specific control laws developed in this work to electro-hydraulic proportional systems is not reported in the literature and multi-switching mode intelligent hybrid control is potentially useful to other electro-hydraulic proportional systems.

Robotic excavator trajectory control using an improved GA based PID controller

Abstract In order to achieve excellent trajectory tracking performances, an improved genetic algorithm (IGA) is presented to search for the optimal proportional-integral-derivative (PID) controller parameters for the robotic excavator. Firstly, the mathematical model of kinematic and electro-hydraulic proportional control system of the excavator are analyzed based on the mechanism modeling method. On this basis, the actual model of the electro-hydraulic proportional system are established by the identification experiment. Furthermore, the population, the fitness function, the crossover probability and mutation probability of the SGA are improved: the initial PID parameters are calculated by the Ziegler-Nichols (Z-N) tuning method and the initial population is generated near it; the fitness function is transformed to maintain the diversity of the population; the probability of crossover and mutation are adjusted automatically to avoid premature convergence. Moreover, a simulation study is carried out to evaluate the time response performance of the proposed controller, i.e., IGA based PID against the SGA and Z-N based PID controllers with a step signal. It was shown from the simulation study that the proposed controller provides the least rise time and settling time of 1.23 s and 1.81 s, respectively against the other tested controllers. Finally, two types of trajectories are designed to validate the performances of the control algorithms, and experiments are performed on the excavator trajectory control experimental platform. It was demonstrated from the experimental work that the proposed IGA based PID controller improves the trajectory accuracy of the horizontal line and slope line trajectories by 23.98% and 23.64%, respectively in comparison to the SGA tuned PID controller. The results further indicate that the proposed IGA tuning based PID controller is effective for improving the tracking accuracy, which may be employed in the trajectory control of an actual excavator.

Fuzzy PID Control and SIMULINK Simulation of Electro Hydraulic Proportional Relief Valve Loading System

This paper mainly studys the open valve control hydraulic motor loading system.For the electro hydraulic proportional relief valve loading system, the electro hydraulic proportional relief valve and the quadratic component DS1 are modeled, then the mathematical model of the electro hydraulic proportional relief valve loading system is obtained. The dynamic and steady state characteristics of the loading system are stabilized by fuzzy PID control technique. Finally modeling and Simulating the electro-hydraulic proportional relief valve loading fuzzy PID control system by SIMULINK.

A dead-band model and its online detection for the pilot stage of a two-stage directional flow control valve

The dead-band in the electro-hydraulic proportional control valve is one of the main factors that affect its dynamic performance. Especially in the pilot stages of two-stage directional flow control valves, the insistent dead-band will result in a conservative valve controller design. In this paper, a detailed dead-band model describing the relationship between pilot valve spool and the flow rate of the pilot control valve is proposed. And an improved dead-band description involved with the housing clearance of the valve spool is developed to prove the dead-band uncertainty for a single valve system. Then a simple and effective method is proposed to detect the varying dead-band values in the pilot stage. This method is specially designed with a limited main spool displacement and short time interval so that it can be used for online detection without affecting the hydraulic system where the two-stage valve is involved. With the regular dead-band inverse function, comparative experimental results show that this method is effective to attenuate the large trajectory tracking error caused by the varying dead-band. This dead-band detection also can be applied to other electro-hydraulic proportional valve-controlled position control systems with unknown dead-bands.

Analysis of Hydraulic Press Servo System Based on Robust Controller

This paper researches and analyzes the modeling of electro-hydraulic proportional servo system to improve the characteristics of forging hydraulic servo control system and meet their requirements of forging a variety of materials. Based on robust compensator design, PID control strategy is proposed with uncertain disturbance of hydraulic press hydraulic servo system and the response characteristics of the system is simulated and analyzed. The results show that hydraulic press servo system which uses robust compensator has better performance than the traditional PID control and the chattering is eliminated. The test results and simulation results are compared by building simulation test system of 60MN hydraulic press electro-hydraulic proportional control system.

EXPERIMENTAL STUDY OF LEAKAGE COMPENSATION ON DYNAMIC CHARACTERISTICS OF HYDRAULIC POWER SYSTEMS

ABSTRACTLeakage compensation in constant load speed hydraulic systems is highly requiredto have a precise control of the job target. To achieve this two options are available,either pump control or flow control. In the present work, experimental investigationof a constant load speed system test rig equipped with proportional electro-hydraulicvalve and variable pump is studied. The leakage compensation has been achievedby controlling the proportional electro-hydraulic valve input volt or controlling thepump speed through frequency modulator. The study aims to highlight the differencebetween these two control options on the dynamic and steady state response of thesystem. The supply and return cylinder pressures, cylinder displacement and flowrate are recorded. Different external leakages have been intentionally introduced inthe connections to the flow control valve to simulate the external system leakage.Results showed that the dynamic and steady state system performance have beenaffected by the system leakage. The volt control signal for proportional DCV andfrequency control for pump control could be used for leakage compensation throughcontroller with a precise control algorithm to compensate leakage in electrohydraulicproportional systems.

Hydraulic Leveling Technology for Electro-Hydraulic Proportional Control Based on Fuzzy PID

In modern military and civil technologies, platforms with equipment on them are often needed to be adjusted to horizontal position rapidly and precisely and keep the platforms stable at the same time. Most leveling systems are implemented with hydraulic system, and they are time-variant nonlinear systems. To leveling both rapidly and steadily with required precision, a PID control strategy based on fuzzy theory was proposed. Electro-hydraulic proportional valve control hydraulic system model was created and analyzed, transfer function of hydraulic legs was obtained and fuzzy PID controller was created in this paper. The proposed method is simulated in Simulink. The simulation result shows that fuzzy PID controller can adjust the platform to horizontal position rapidly and steadily, and improve system performance.

PI Control of Proportional Valve-Cylinder Water Hydraulic System

Water hydraulic components have been developed rapidly in recent years. However many problems such as low lubricity and leakage limited the performance of them, especially water proportional valves. A proportional valve- hydraulic cylinder system with tap water as working medium is chosen as object to investigate the performance of water hydraulic system. With regarding to the weaknesses of the selected 4/3 proportional valve including lag, dead zone and nonlinearity, an integral separation PI arithmetic based close-loop controller is developed. Experiments results verified the electro-hydraulic proportional system of fast response speed and high accuracy.

Research on the Characteristics of Electro-hydraulic Proportional Steering System in Self-Propelled Modular Transporter

Research on the Characteristics of Electro-hydraulic Proportional Steering System in Self-Propelled Modular Transporter

Analysis and Optimization of Electro-Hydraulic Proportional Speed Synchronous System Based on AMESim

The system models for analysis and optimization of an electro-hydraulic proportional synchronous system is presented based on AMESim. This paper studies the control strategy for the improvements of the response time, steady-state accuracy, stability and synchronization of the system. The speed of a hydraulic motor can be controlled through regulation of the PID controller by the genetic algorithm. Simulation results show that performances of the system have been improved and expected results can also have been obtained.

Research on Electro-Hydraulic Proportional Self-Tuning Fuzzy-PID Control System Based on MATLAB

The bogie separated equipment for straddle type monorail vehicle was researched, and the mathematics model of proportional hydraulic valve cylinder lifting system was set up and simulated. Based on the PID controller theory and the principle of fuzzy control, the fuzzy self-turning fuzzy-PID controller was designed. According to the fuzzy logic tool box and simulink of MATLAB, the simulation study was carried out. The results indicate that, the self-tuning fuzzy-PID controller can satisfy the requirements of the control system well.

Hydraulic System Modeling and Motion Control of Demotion Robots Working Equipment

Based on the electro-hydraulic proportional system of a demolition robot working device, a simplified mathematical model was established by analyzing dynamic characteristics of the electro-hydraulic proportional valve, flow equation, the continuity equation and force equilibrium equations, and the fuzzy self-adaptive PID controller was designed to realize position control of working equipment. The simulations reveal that, compared with traditional PID, the fuzzy self-adaptive PID controller has these advantages such as smaller overshoot, good dynamic response and steady state performance.

BP-PID Control for Electro-hydraulic Proportional Position Servo System

The electro-hydraulic proportional position servo system is a kind of highly non-linear and time-varying system as well as parameter uncertainties. It is often difficult to achieve satisfactory control results with the traditional control methods. Considering that the adaptive neural network PID control method has the characteristics of online learning and adjustment PID control parameters adaptively, this paper puts forward to adopt BP-PID control method for the position servo control of electro-hydraulic proportional system. An online adaptive BP-PID controller is designed. The simulation model of the system is established based on Simulink platform. The step response and Sinusoidal tracking characteristics are researched for electro-hydraulic proportional position servo system by using traditional PID and BP-PID control algorithms through simulations and experiments. The results show that BP-PID has a strong ability of online learning and self-tuning PID parameters. Compared with the traditional PID control method, the BP-PID control has strong self-adaptability and robustness, and can significantly improve the step response speed and tracking control precision.

Fuzzy-PID Control in Electro-Hydraulic Proportional Valve Control System of Snow-Melting Agent Spreading Truck

According to the characteristic of the snow-melting agent spreading truck that the spreading measurement is maintaining unchanged when it's in the operation process. We designed the rotate speed system controlled by the method of electro-hydraulic proportional control. With the nonlinearity and time-varying of the controlled system, we applied the method of Fuzzy-PID control to conduct the study of electro-hydraulic proportional speed system. By the simulation of MATLAB/SIMULINK, the results shows the dynamic property of the system gets obviously improved with using the Fuzzy-PID controller and verifies the effectiveness and practical applicability of this design.

Design on Electro-hydraulic Proportional Controller

As the connection of micro-electronics and powerful engineering equipment, Electro-Hydraulic proportional controller has been important part of integration of mechanics and electrics. It’s the core of Electro-Hydraulic proportional controller system and has a tremendous impact on it. The prevalence of domestic proportional controller poor reliability, short life and other issues, therefore, this paper developed a new type of electro-hydraulic proportion controller with a graphics user interface based on Qt. After experiment, it shows the controller has some advantages as follows, low power consumption, high repeatability precision and low temperature drift. And the graphics user interface is friendly with stable performance