Ahn Kyoung Kwan

A study on force control of electric-hydraulic load simulator using an online tuning Quantitative Feedback Theory

Nowadays, hydraulic actuators play an important role in a modern industry where controlled force or position with high accuracy is the most significant demand. This paper presents a new kind of electric-hydraulic load simulator (HLS) for conducting performance and stability test in the bench system where force control is important. The system model consists of a hybrid hydro-electric actuator and another hydraulic circuit generating disturbances. For the purpose of improving force control performance of hydraulic hybrid systems, an online tuning force controller based quantitative feedback theory (QFT) technique is applied to the load simulator and also proposed in this paper. The controller is firstly designed to satisfy the robust performance requirement, tracking performance specification, and disturbance attenuation despite uncertainties of the load simulator system. Secondly, by using gradient descent method it becomes an online tuning QFT controller during the system operation process to adapt with a wide range of working conditions including perturbations. Experiments are carried out to evaluate the effectiveness of the proposed control method applied for the electric-hydraulic load simulator systems.

New approach to design MR brake using a small steel roller as a large size magnetic particle

Nowadays, conventional Magneto-Rheological (MR) fluid has been commonly used in many types of device operating within three its modes that have widely known as valve, shear and squeeze film modes. Except valve mode, shear and squeeze film modes just can generate the weak resistance force. Therefore, this paper proposes a new approach with the purpose that it can help to increase the weak force in shear mode by the application of a large size magnetic particle which is a small steel roller. This kind of particle with its hydrodynamic form helps the new MR brake device which can generate the higher braking torque than the conventional one. The theory of this proposed approach is based on the deformation theory with the support of the improved magnetic field. The practical application of this approach has been examined by experimental results.

A study on the position control of hydraulic cylinder driven by hydraulic transformer using disturbance observer

A hydraulic cylinder drive using a hydraulic transformer, which is considered as secondary controlled unit, is studied here. Using hydraulic transformer for driving a hydraulic cylinder should avoid energy loss via controlled valves and get benefit from recovery of the load potential. Position control, an important issue of the cylinder control is investigated in this paper. To obtain robust position control in spite of external load disturbance and variation of parameters in the system, a two degree of freedom robust controller based on disturbance observer is designed. The controller includes a mixed - sensitivity Hinfinin controller and a high order disturbance observer. Weights for controller synthesis and filter in the disturbance observer are fixed in their structure but vary in values of the coefficients. Genetic algorithm is used to tune parameters of the weights and time constants of the filter. In this manner, a controller with its structure based on robust analysis and parameters depended on performance of nominal plant is design. Simulation results indicate that the system guarantees the robustness with external load disturbance, variation in parameters and sensor noise.

An Application of the Novel Linear Magnetic Actuator to Controllable Squeeze Film Damper

An enhancement of the dynamic behavior of the rotating shaft work at high operating speed by using Squeeze film dampers (SFDs) has been becoming an important part in changing the dynamic characteristics of machinery. In this paper, a new type Controllable Squeeze Film Damper (CSFD) is proposed, designed and fabricated by changing the clearance of the thin-film fluid. Both of the critical speed and critical amplitude are reduced with the suitable damping coefficient. A novel Linear Magnetic Actuator (LMA) is investigated and used to move the outer damper of the CSFD. The experiment results illustrate basically the concept of electromagnetic effect as well as the interaction force between electromagnet and permanent magnet. Furthermore, the PID and advanced (a self-tuning fuzzy PID) controllers are subsequently applied to controlling exactly the position of a novel LMA. The experimental results reveal that the vibration behavior of rotor dynamic response is affected effectively by changes of the clearance.

A study on the energy regeneration system of boom for hybrid hydraulic excavator

Nowadays, energy crisis and pollution have become a serious problem in the world. Saving energy of construction machinery, especially the hydraulic excavator is very essential. Potential gravitational energy regeneration is an effective solution to reduce the energy consumption of the hydraulic excavator. This paper proposes a new hybrid hydraulic excavator boom system and designs a new control strategy. In this system have three modes for boom down. The proposed energy regeneration system is verified through simulation result which is done in the AMESim software. By analyzing simulation result, the proposed system can perform very efficiently. Meanwhile, the proposed system is also compared with conventional one. By comparing and analyzing the simulation results, it seen that the new system has a better efficiency and decrease the energy consumption significantly. All parameters are taken from the real system.

A study on hydraulic load simulator using self tuning grey predictor – fuzzy PID

Abstract Nowadays, considering the development of the industry, hydraulic actuator has a wide range of application fields. This paper presents a kind of hydraulic load simulator for conducting performance and stability test for control force of hydraulic hybrid systems. A grey prediction model GM(1,1) combined with a fuzzy PID controller is suggested to apply for this system. Furthermore, fuzzy controllers and a tuning algorithm are used to change the Grey step size to improve the control quality. The grey prediction compensator can improve the system settle time and overshoot problems. Simulations and experiments are carried out to evaluate the effectiveness of the proposed control method applied for hydraulic systems with varied external disturbance as in real working conditions.

Study on energy regeneration system for hybrid hydraulic excavator

Nowadays, with the development of global energy crisiss compression and high fuel expenditure, the demands for energy saving and green emission of construction machineries, especially hydraulic excavators, have been rapidly increased. Meanwhile, the power efficiency of the conventional hydraulic excavators is very low. This study deals with the method to regenerate potential energy on the boom system of the hybrid hydraulic excavator. The novel hydraulic circuit as well as the control strategy are introduced to make sure that the performance of the system is satisfied and maximize the energy regeneration capability. The model of the proposed system and the control strategy are built and simulated by AMEsim and Matlab software while the system parameters are taken from a real system. The results show that the proposed energy recovery system and control strategy can improve energy recovery efficiency and optimize working performance of the system.

Mathematical modeling of a variable displacement vane pump for engine lubrication

This paper developed a complete and accurate mathematical model for a typical variable displacement vane-type oil pump to investigate the working performance of the pump. Firstly, the detailed theoretical model was built based on pumps geometric design and dynamic analyses. Next, numerical simulations with the constructed model and experiments on the real pump system were carried out to analyze the main power loss factors in order to develop the complete model with high accuracy. The estimated pump performance using the complete pump model was finally verified by numerical simulations in comparison with the practical tests.

A nonlinear control system using a fuzzy self tuning Grey predictor based on a PID controller

In this paper, a nonlinear control system using a fuzzy self tuning Grey predictor based on a PID controller is proposed. Firstly, the PID controller is designed according to the Zieger-Nichos 2 method with fast response and high robustness. Secondly, the grey predictor is suggested to use to estimate the system response in a near future in order to improve the control performance. In addition, the step of Grey predictor is adjusted by using the fuzzy control to satisfy the control requirement. Consequently, the control system fastens rising time, shortens settling time, reduces steady state error to zero, oppresses overshoot of transient response, and also prevents disturbance. A detailed specification of the control structure and its design process as well as simulation results achieved from Matlab/Simulink program are also presented. The simulation results show that the proposed control method has the ability to apply for nonlinear systems with higher control performance.

Precision control for ionic polymer metal composite actuator based on quantitative feedback theory

An ion polymer metal composite (IPMC) is an Electro-Active Polymer (EAP) that bends in response to a small applied electrical field as a result of mobility of cations in the polymer network and vice versa. Recently, IPMC is widely applied in many fields such as biometric, biomedical and micro manipulator fields. This paper proposes a robust position controller for IPMCs which is based on the quantitative feedback theory (QFT). Firstly, the IPMC actuation was investigated. The PRBS input voltage signals were applied to the IPMC in order to identify the system characteristic. Consequently, the QFT controller for the IPMC was designed from the identified IPMC model. Experiments were carried out to validate the effectiveness of proposed controller applied to the IPMC.