Simulation of electro-hydraulic servo actuator

Hydraulic actuators are used in many applications like aircraft flight control, machinery and automobiles etc. This actuator when coupled with a feedback system is called a Servo Actuator. The response of the hydraulic actuator with time is significant particularly when the actuator is used for flight control operations. So finding the time response operation will be very helpful for the designer for analyzing the performance of the system. This also helps the designer to arrive at optimum design parameters of the hydraulic actuator. In this thesis a position control electro-hydraulic linear actuator is selected. This actuator is used for controlling the movements of the helicopter. Mathematical modelling of the hydraulic actuator and its components is done and based on the mathematical equations Matlab/Simulink models of the actuator and its components were made and the time response of the linear actuator is obtained by using Matlab/Simulink Software. The time response graphs which are obtained in this simulation are found to be in good compromise with the time response graphs of Moog experimental time response graphs

Volume 3 – Conference

We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics Group 9 | 11: Mobile applications Group 10: Special domains Group 12: Novel system architectures Group 13 | 15: Actuators & sensors Group 14: Safety & reliabilit

Development of Motion Control Systems for Hydraulically Actuated Cranes with Hanging Loads

Automation has been used in industrial processes for several decades to increase efficiency and safety. Tasks that are either dull, dangerous, or dirty can often be performed by machines in a reliable manner. This may provide a reduced risk to human life, and will typically give a lower economic cost. Industrial robots are a prime example of this, and have seen extensive use in the automotive industry and manufacturing plants. While these machines have been employed in a wide variety of industries, heavy duty lifting and handling equipment such as hydraulic cranes have typically been manually operated. This provides an opportunity to investigate and develop control systems to push lifting equipment towards the same level of automation found in the aforementioned industries. The use of winches and hanging loads on cranes give a set of challenges not typically found on robots, which requires careful consideration of both the safety aspect and precision of the pendulum-like motion. Another difference from industrial robots is the type of actuation systems used. While robots use electric motors, the cranes discussed in this thesis use hydraulic cylinders. As such, the dynamics of the machines and the control system designmay differ significantly. In addition, hydraulic cranes may experience significant deflection when lifting heavy loads, arising from both structural flexibility and the compressibility of the hydraulic fluid. The work presented in this thesis focuses on motion control of hydraulically actuated cranes. Motion control is an important topic when developing automation systems, as moving from one position to another is a common requirement for automated lifting operations. A novel path controller operating in actuator space is developed, which takes advantage of the load-independent flow control valves typically found on hydraulically actuated cranes. By operating in actuator space the motion of each cylinder is inherently minimized. To counteract the pendulum-like motion of the hanging payload, a novel anti-swing controller is developed and experimentally verified. The anti-swing controller is able to suppress the motion from the hanging load to increase safety and precision. To tackle the challenges associated with the flexibility of the crane, a deflection compensator is developed and experimentally verified. The deflection compensator is able to counteract both the static deflection due to gravity and dynamic de ection due to motion. Further, the topic of adaptive feedforward control of pressure compensated cylinders has been investigated. A novel adaptive differential controller has been developed and experimentally verified, which adapts to system uncertainties in both directions of motion. Finally, the use of electro-hydrostatic actuators for motion control of cranes has been investigated using numerical time domain simulations. A novel concept is proposed and investigated using simulations.publishedVersio

Nonlinear Control Strategies for Advanced Vehicle Thermal Management Systems

Advanced thermal management systems for internal combustion engines can improve coolant temperature regulation and servo-motor power consumption to positively impact the tailpipe emissions, fuel economy, and parasitic losses by better regulating the combustion process with multiple computer controlled components. The traditional thermostat valve, coolant pump, and clutch-driven radiator fan are upgraded with servo-motor actuators. When the system components function harmoniously, desired thermal conditions can be accomplished in a power efficient manner. Although the vehicle\u27s mechanical loads can be driven by electric servo-motors, the power demands often require large actuator sizes and electrical currents. Integrating hydraulically-driven actuators in the cooling circuit offers higher torques in a smaller package space. Hydraulics are widely applied in transportation and manufacturing systems due to their high power density, design flexibility for power transmission, and ease of computer control. In this dissertation, several comprehensive nonlinear control architectures are proposed for transient temperature tracking in automotive cooling circuits. First, a single loop experimental cooling system has been fabricated and assembled which features a variable position smart valve, variable speed electric coolant pump, variable speed electric radiator fan, engine block, radiator, steam-based heat exchanger, and various sensors. Second, a multiple loop experimental cooling system has been assembled which features a variable position smart thermostat valve, two variable speed electric pumps, variable speed electric radiator fan, engine block, transmission, radiator, steam-based heat exchanger, and sensors. Third, a single loop experimental hydraulic-based thermal system has been assembled which features a variable speed hydraulic coolant pump and radiator fan, radiator, and immersion heaters. In the first and second configured systems, the steam-based heat exchanger emulates the engine\u27s combustion process and transmission heat. For the third test platform, immersion heating coils emulate the combustion heat. For the first configured system, representative numerical and experimental results are discussed to demonstrate the thermal management system operation in precisely tracking desired temperature profiles and minimizing electrical power consumption. The experimental results show that less than 0.2°K temperature tracking error can be achieved with a 14% improvement in the system component power consumption. In the second configured system, representative experimental results are discussed to investigate the functionality of the multi-loop thermal management system under normal and elevated ambient temperatures. The presented results clearly show that the proposed robust controller-based thermal management system can accurately track prescribed engine and transmission temperature profiles within 0.13°K and 0.65°K, respectively, and minimize electrical power consumption by 92% when compared to the traditional factory control method. Finally, representative numerical and experimental results are discussed to demonstrate the performance of the hydraulic actuators-based advance thermal management system in tracking prescribed temperature profiles (e.g., 42% improvement in the temperature tracking error) and minimizing satisfactorily hydraulic power consumption when compared to other common control method

Improving performance of an energy efficient hydraulic circuit

Hydraulic circuits with fast dynamic response are often characterized by low power efficiency; on the other hand, energy-efficient circuits under certain circumstances, can demonstrate slow transient responses. Continuously rising energy costs combined with the demand on high performance has necessitated that hydraulic circuits become more efficient yet still demonstrate superior dynamic response. This thesis introduces a new hydraulic circuit configuration which demonstrates high dynamic performance and high efficiency. A pump-controlled hydraulic motor system was used as the basis of the study because of its high circuit efficiency. This is primarily because there is no power loss between the pump and motor. To improve the dynamic response of the pump, a DC motor was designed to control the pump swashplate (and hence flow rate) directly. The pump and DC motor were mathematically modeled and their parameters were experimentally identified. Based on the model and experimental results, a nonlinear PID controller was designed for the DC motor. By means of the DC motor’s quick dynamic response (in the order of 10 ms), the DC motor controlled pump demonstrated a fast dynamic response with a rise time of 15 to 35 ms depending on the pump pressure. As the dynamic response speed of the pump flow rate was increased, overshoot of the hydraulic motor output also increased. To reduce this overshoot, a bypass flow control circuit was designed to bypass part of the flow during the transient. Due to the unique operating requirements of the bypass flow control system, a PID controller with a resetable integral gain was designed for the valve to reduce the rise time of the bypass control valve. The feasibility ("proof of concept") of the bypass flow control concept was first established using simulation techniques. The simulation results showed that the bypass flow control system could significantly reduced the overshoot of the hydraulic motor rotational speed. The bypass controller was applied to the experimental test circuit. The transient results for the pump-controlled motor system with the bypass flow control are presented under a constant resistive and an inertial load. The test results showed that the bypass flow control could reduce the overshoot of the hydraulic motor rotational speed by about 50%. The relative efficiency of the circuit with the bypass flow control system was 1% to 5% lower for the particular pump-controlled system that was used in this study. For a pump/motor that does not demonstrate significant flow ripple of the magnitude experienced in this study, the relative efficiency would be the same as the pump/motor system without bypass. It was concluded that the proposed bypass control system, combined with the DC motor-swashplate driven pump, could be used to create an energy efficient circuit with excellent dynamic transient responses

Automotive suspension system modelling and controlling

In both academic and industrial fields, suspension system modelling and associated control design influence vehicle response. Ideal hydraulic force models have been used in active suspension studies for decades, but few studies have investigated hydraulic effects, which are the core of system force generation. Accurate mathematical subsystem modelling is essential in representing physical subsystems and enhancing design estimation control. This thesis details the mathematical modelling of both passive and active suspension and controller design for a quarter-car test rig. When using a conventional passive model, a significant difference between the experimental and simulation results was found for improved modelling of body movements. This led to an investigation in how to resolve this issue, accordingly, the consideration of a new term (friction force) was researched. Establishing a nonlinear friction force became a vital aspect of this work. In addition, emphasis was placed on hydraulic modelling and unknown model parameters that were experimentally identified. This experimental work is unique and helpful for advancing knowledge of any system. A new approach to implementing the friction force was used to identify the system through the transformation of a ¼ car model to one Degree of Freedom (DOF) and two-DOF models. This reduced the model complexity and allowed the parameters to be identified from a series of transfer functions linking vehicle parts and the hydraulic models. Simulation and experimental results were then compared. The hydraulic component model is crucial to the formulation of accurate active control schemes. Full-state feedback controls were realised by Pole-Assignment (PA) and Linear Quadratic (LQ) optimal method. Simulation results suggest that even though the performance of active suspension designed by the PA method is superior to that of passive suspension, it still possesses a design constraint, similar to a passive system, as the design is a compromise between the effects of natural frequency and transmissibility. With a different design concept, the LQ method provided a better solution as it reduced energy consumption by 65% and effectively shifts the dominant natural frequency to a very low-frequency range. Thus, allowing the damping rate to be increased to its critical value with the smallest effect on transmissibility. iv It was estimated for experimental work that the identified model with the LQ controller might be used to predict the dynamic responses of the actual system within a certain range of the design parameters due to the considerable difference between the initial condition of the test rig and the linearised operating design. The servovalve produced issues that did not allow validation of the controller. Both simulation and experimental results, with several conditions, showed consistent agreement, between experimental and simulation output, consequently confirming the feasibility of the newly approved model for passive and active suspension systems that accounted for the actual configuration of the test rig system. These models, that subsequently implemented the nonlinear friction forces that affect the linear supported body bearings, are entirely accurate and useful. The nonlinear friction model captures most of the friction behaviours that have been observed experimentally. Additionally, the models of the nonlinear hydraulic actuators, covered by the dynamic equation for the servovalve, are moderately precise and practical. The suggested Proportional Integral (PI) control successfully guided the road hydraulic actuator and validated the control strategy. The suggested PA and LQ controllers for active systems successfully guided the system to achieve the targets. Ride comfort and handling response are close to that expected for the passive suspension system with road disturbances, whereas there were clear response enhancements for the active system