Hydraulic Servo Control Research Articles

Comparison Precision of Oil Film Thickness of a Hydrostatic Bearing by Using Different Controllers under External Load

This paper describes a hydrostatic bearing to maintain the oil film thickness, which integrates the hydraulic servo control technology. This study has designed the different intelligent nonlinear controllers by using a non-contact displacement sensor to feedback the oil film thickness of the bearing. This study proposes a fuzzy controller, a self-tuning fuzzy controller and a self-tuning fuzzy sliding mode mechanism to modify the output scaling factor and adds a dead zone compensator to achieve a constant oil film thickness. Finally, the experimental results are used to verify the feasibility and practical implementation success of this study.

Study on Bicycle Manufacturing Engineering with the Quality Detection Device for the Carbon Fiber Sports Bicycle

In order to realize light weight, high strength, anti-fatigue for sports bicycle, carbon fiber was used as a predominant material of high-grade sports bicycle. The manufacturing engineering with quality detection device was studied to ensure manufacturing quality and riding safety of carbon fiber sports bicycle.The hydraulic servo control system and modular fixtures were developed in this paper, the former can realize double close-loop control and improve testing accuracy of the device, the latter can realize that a variety of works can be tested on the same testing bench and improve testing efficiency of the device.

Study on Dynamic Characteristics of Hydraulic Pressure System of MPM Tube Rolling Mill

Now MPM mill is widely used in hydraulic servo control technology in the field of seamless steel pipe production. But the hydraulic control system has the defect of complex control, bigger load power, more disturbance factors, higher response speed requirement and so on, which are unfavorable for analyzing the impact of factors of steel rolling precision. The conclusions show that: the system model is conducive to the analysis of the factors that affect the rolling accuracy, and it provides a theoretical basis for study the dynamic characteristics of the system, the optimal design and so on.

Static and Dynamic Flexural Strength Anisotropy of Barre Granite

Granite exhibits anisotropy due to pre-existing microcracks under tectonic loadings; and the mechanical property anisotropy such as flexural/tensile strength is vital to many rock engineering applications. In this paper, Barre Granite is studied to understand the flexural strength anisotropy under a wide range of loading rates using newly proposed semi-circular bend tests. Static tests are conducted with a MTS hydraulic servo-control testing machine and dynamic tests with a split Hopkinson pressure bar (SHPB) system. Six samples groups are fabricated with respect to the three principle directions of Barre granite. Pulse shaping technique is used in all dynamic SHPB tests to facilitate dynamic stress equilibrium. Finite element method is utilized to build up equations calculating the flexural tensile strength. For samples in the same orientation group, a loading rate dependence of the flexural tensile strength is observed. The measured flexural tensile strength is higher than the tensile strength measured using Brazilian disc method at given loading rate and this scenario has been rationalized using a non-local failure theory. The flexural tensile strength anisotropy features obvious dependence on the loading rates, the higher the loading rate, the less the anisotropy and this phenomenon may be explained considering the interaction of the preferentially oriented microcracks.

Laboratory measurements of the rate dependence of the fracture toughness anisotropy of Barre granite

Barre granite exhibits strong anisotropy due to its pre-existing microcracks induced by long-term tectonic loading. The quantification of rock anisotropy in fracture properties such as mode-I fracture toughness under a wide range of loading rates is critical to a variety of rock engineering applications. To quantify fracture toughness of Barre granite, notched semi-circular bend (NSCB) fracture tests are conducted statically with an MTS hydraulic servo-control testing machine and dynamically with a split Hopkinson pressure bar (SHPB) system. Barre granite samples are prepared based on the three principal directions, resulting in six orientation sample groups. For dynamic tests, pulse shaping technique is used to achieve dynamic force balance. The finite element method is then implemented to formulate equations relating the failure load to the mode-I fracture toughness using an orthotropic elastic material model. For samples in the same orientation group, the fracture toughness shows clear loading rate dependence, with the fracture toughness increasing with the loading rate. The fracture toughness anisotropy is characterized by the ratio of the largest fracture toughness over the smallest one at a given loading rate. The mode-I fracture toughness anisotropy exhibits a pronounced rate dependence, being strong under static loading while diminishing as the loading rate increases. The mode-I fracture toughness anisotropy may be understood by considering the preferentially oriented microcracks, which will be fully explored in the future.

Adaptive Fuzzy Sliding Mode Control of Asymmetrical Hydraulic Cylinder Based on DSP

An adaptive fuzzy sliding mode control strategy is designed to solve the problem of nonlinear, disturbances and uncertain parameters in asymmetric hydraulic cylinder position servo control system. Variable parameters and external disturbances of the system are identified by adaptive function. Meanwhile fuzzy exponential velocity reaching law is introduced to reduce the chatting phenomenon. Simulation results show the system dynamic performance is improved, the chattering phenomenon which caused by traditional sliding mode variable structure is weakened and the proposed algorithm is feasible. The algorithm control experiment of asymmetric hydraulic cylinder was done on the DSP28335 hardware platform. The experiment proves the effectiveness of the algorithm and achieves a good control result.

Project calculation of the steering mechanism hydraulic servo control in motor vehicles

Hydraulic servo controls are designed to facilitate rotation in place without providing increased power to steering wheels. In the initial design phase, the dimensions required for control systems are usually obtained through the calculation of their load when wheels rotate in place, where the torque is calculated empirically. The starting point in the project calculation is thus to determine the hydraulic power steering torque torsional resistance which is then used to determine the maximum value of force i.e. the torque on the stering wheel. The calculation of the control system servo control consists of determining the basic parameters, the required pump capacity, the main dimensions of the hub and the pipeline and the conditions for the stability of the system control mechanism.

The Principle of Emergency Cut-off Valve Hydraulic Servo Control and Simulation and Analysis for Emergency Cut-Off

The system is under the control of electro-hydraulic servo loop, and makes it possible to automatically adjust the valve in real time. It uses the accumulator as a power source of emergency cut-off to achieve cut-off of the valve. Based on AMESim, we established a mathematical model of the Emergency Cut-off Valve that can make a simulation analysis about the data of displacement, velocity, acceleration when it shut down. This study provides a theoretical basis to the analysis and design of Emergency Cut-off Valve.

A Hydraulic Control System Design for Change-Wheel Garage of Light Rail Based on PLC

This paper introduces the hydraulic control system design for the change-wheel garage of Chongqing light rails through analysis of three-stage cylinder synchronization circuit for lifting bodies, and optimizing the design of the slewing mechanism with respect to the hydraulic servo control system of digital cylinder. The results improved the smoothness in the process of changing wheel lifting and the rotary accuracy of the rotary mechanism. Design on the PLC control system of the system is also included as part of this paper.

Study on the Speed Control System of Hydraulic Pump-Motor Based on PID Neural Network

Theoretical models of hydraulic pump-motor and electro-hydraulic servo control systems of hydraulic pumps were established and the system transfer function was derived In view of bad dynamic property, small damp, long transient time, low precision, nonlinearity and etc existing in the speed control system of Hydraulic Pump-Motor, a controller based on PID Neural Network was designed. The simulation results showed that the PID Neural Network controller has better dynamic property, load disturbance adaptability , robustness and cranking ability than traditional PID controller.

Simulation and Study on Non-Sinusoidal Oscillation Control System of Continuous Casting Mold

The paper describes the composition and working principle of the mold oscillation control system. The mathematical model of hydraulic servo control system is established. The total system transfer function is established by MATLAB program. By using the SIMULINK module, we determined various components’ parameter values. We got different simulation curves and Bode plots by inputting non- sinusoidal function and carrying out the dynamic simulation to the mold oscillation mathematical model, we also analyzed stability of the whole system to verify the accuracy of system design.

A Design of TRT Hydraulic Servo Controller Based on DSP

The composition and working principle of electric hydraulic servo control system are briefly described. A program is designed about digital servo controller based on DSP structure, and the servo system is achieved to control position by using TMS320LF2407A’s powerful digital processing capabilities, rich peripheral interfaces and optimal control algorithm of deviation, meanwhile it also has complete self-testing, setting parameters online and other functions. It is shown that the digital servo controller runs reliably, achieves real-time and precise control effect, and can meet the TRT and other systems’ control requirements with the experimental results.

Design of Automatic Assembly Tire Machine

This system realizes the function of automatic tire assembly which not only took PLC as control center but also synthetically applied with converter, servomotor and hydraulic. Firstly, it completes the carry of tire with converter by the way of different frequency. Secondly, PLC is used to control servomotor to finish assembling of tire. Thirdly, exact position control is designed through the use of the electro hydraulic servo control. Farther more, mathematics model is established. At the end of this paper, we compare machine efficiency with the manual operation and present the application foreground of this system.

A Combined Nonlinear PID Control and Cross-Coupled Pre-Compensation Control in Hydraulic Excavator

In position control system of hydraulic excavator, the uncoordinated speeds between joints make quite trajectory errors no matter how well each joint performs. In order to solve this problem, a cross-coupled pre-compensation method is introduced in and applied to hydraulic excavator servo control system to solve this problem. Furthermore, in order to compensate for the nonlinearities of excavator and friction resistance, a nonlinear controller with angle velocity error observer and acceleration feedback is designed. Experimental results show that the proposed control strategy is effective in improving tracking accuracy and response ability when subjected to external load.

Simulation investigation on fluid characteristics of jet pipe water hydraulic servo valve based on CFD

Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve (WHJPSV) is con- ducted through a commercial computational fluid dynamics (CFD) software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that: (i) Structural parameters have great influences on fluid characteristics of WHJPSV, when d1 = d2 = 0.3 mm, α =4 5 ◦ , b = 0.5 mm, and the simulation exhibits better fluid characteristics; (ii) The magnitude of the recovery pressure and flow velocity increase almost linearly with the deflection angle of jet pipe. The research work in this paper is important for deter- mining and optimizing the structural parameters of the jet pipe and jet receiver. The relevant conclusions could be extended to the study of other water hydraulic servo control components.

The velocity control of an electro-hydraulic displacement-controlled system using adaptive fuzzy controller with self-tuning fuzzy sliding mode compensation

Hydraulic servo control systems have been used widely in industry. Within the realm of hydraulic control systems, conventional hydraulic valve-controlled systems have higher response and lower energy efficiency, whereas hydraulic displacement-controlled servo systems have higher energy efficiency. This paper aims to investigate the velocity control performance of an electro-hydraulic displacement-controlled system (EHDCS), where the controlled hydraulic cylinder is altered by a variable displacement axial piston pump to achieve velocity control. For that, a novel adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC-STFSMC) is proposed for velocity control in EHDCS. The AFC-STFSMC approach combining adaptive fuzzy control and the self-tuning fuzzy sliding-mode control scheme, has the advantages of the capability of automatically adjusting the fuzzy rules and of reducing the fuzzy rules. The proposed AFC-STFSMC scheme can design the sliding-mode controller with no requirement on the system dynamic model, and it can be free of chattering, thereby providing stable tracking control performance and robustness against uncertainties. Moreover, the stability of the proposed scheme via the Lyapunov method is proven. Therefore, the velocity control of EHDCS controlled by AFC-STFSMC is implemented and verified experimentally in different velocity targets and loading conditions. The experimental results show that the proposed AFC-STFSMC method can achieve good velocity control performance and robustness in EHDCS with regard to parameter variations and external disturbance. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Nonlinear Self-Adaptive Compensation of Screw down System of Tandem Cold Mill

The Screw Down System (SDS) is a typical hydraulic servo control system. It is the key actuator of cold rolling mill. The dynamic performance of SDS has a significant effect on the accuracy of thickness. Hydraulic servo control system is not always optimal and stable due to highly nonlinear and parameter uncertainties. In this paper, the most important nonlinear relating flow and pressure is analyzed. A nonlinear self-adaptive compensation method is designed. Modeling and simulating the hydraulic servo control system of SDS using this method, the numerical simulation results show that the maximum overshoot and static error of the compensated system are more less than that of without nonlinear compensation. The overshoot of the compensated system is less than 10% when the cold strip is rolling. So the thickness tolerance of the cold strip can be guaranteed easily. This self- adaptive compensation method can be used to other hydraulic servo control systems.

A COMPARISON OF AN AC-SERVO MOTOR DRIVING VARIABLE ROTATIONAL SPEED AND A VARIABLE DISPLACEMENT PUMP-CONTROLLED SYSTEMS FOR VELOCITY CONTROL

In the hydraulic servo control applications, hydraulic valve-controlled systems, which have a problem of low energy efficiency, are used mostly because of the high response characteristics. Hydraulic pump-controlled servo systems have high energy-efficiency. However, the conventional pump-controlled systems, which are altered by displacement via variable displacement pumps, have lower response. This paper aims to investigate the servo performance of the high response and high energy efficiency electro-hydraulic pump-controlled system driven by a variable rotational speed AC servo motor in comparison with the conventional pump-controlled systems which are altered by displacement via variable displacement pumps. For that, the control strategy, adaptive fuzzy sliding-mode controller (AFSMC) is introduced. The AFSMC can not only simplify the fuzzy rule base but also estimate the equivalent control force and online self-tune the rule base through the adaptive strategy. The developed high response variable rotational speed electro-hydraulic pump-controlled system controlled by AFSMC and the conventional variable displacement pump-controlled system (VDPCS) are implemented and verified experimentally for velocity control with various velocity targets and external loading conditions. Furthermore, the energy efficiencies of different experiments are analyzed and compared precisely by the power quality recorder used to measure the electrical power consumed by the AC servo motor.

Application of Fuzzy Gain-Scheduling in Position Control of a Servo Hydraulic System with a Flexible Load

AbstractThe control of hydraulic servo-systems has been the focus of intense research over the past decades. Hydraulic position servos with an asymmetrical cylinder are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Changing system parameters using the same gains will cause overshoot or even loss of system stability. The highly non-linear behaviour of these devices makes them ideal subjects for applying different types of sophisticated controllers. The paper is concerned with a second order model reference to positioning control of a flexible load servo-hydraulic system using fuzzy gain-scheduling. In the present study, to compensate the lack of damping in a hydraulic system, an acceleration feedback was used. To compare the results, a p-controller with feedforward acceleration and different gains in extension and retraction is used. The design procedure for the controller and experimental results are discussed. The results suggest that using ...

VARIABLE RATE GRANULAR FERTILIZATION OF CITRUS GROVES: SPREADER PERFORMANCE WITH SINGLE-TREE PRESCRIPTION ZONES

Commercial variable rate technology (VRT) fertilizer spreaders for citrus are currently being implemented inFlorida groves to improve profitability and reduce nitrate contamination of groundwater. Although VRT spreadersincorporate proven embedded controllers and tree sensors which permit changing fertilizer rates according to tree size, thereis currently limited information on their performance characteristics in spatially variable groves. This study investigated theperformance characteristics of a split-chain, spinner-type VRT spreader during fertilization of a commercial citrus grove.Six nitrogen rates (0, 134, 168, 202, 236, and 270 kg ha-1 y-1) were varied according to a prescription map developed fromultrasonically measured tree size information. Missing trees and one-year-old reset trees were not fertilized with the spreader.Target fertilizer rates for 1490 trees in an 8.1-ha experimental area were compared with actual fertilizer rates calculated fromgeartooth speed sensors monitoring the conveyor chain speed. Through classification and regression analysis, spreaderperformance and response times during transitions from zero or low fertilizer rates to high rates and vice versa werecompared. In this grove, 73.1% of the fertilizer rate changes were required between a single-tree space of 5.3-m linear rowdistance, taking about 4 s to drive at 1.34 m s-1. The spreader had an average on-off response time of . 3 s, and an averagerate changing response time of 2 to 5 s. Based on these data, the spreader design is not suitable for rapid fertilizer rate changesbetween single tree spaces, but could be greatly improved by substituting its hydraulic servo control valves with faster devices.