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Prof. Kyoung Kwan Ahn
University of Ulsan, South Korea

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Research Keywords & Expertise

0 Energy Harvesting
0 flow battery
0 Triboelectric Nano generator
0 Fluid Power Control
0 Hydraulic Robot

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Energy Harvesting
Triboelectric Nano generator

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Journal article
Published: 03 August 2021 in Automation in Construction
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In construction, motion control is primary for excavators to complete earth-moving tasks. However, the position tracking performance is strongly affected by system nonlinearity, external disturbances, and model uncertainties during operation. In this paper, a task coordinate frame approach is firstly adopted for an excavator to separate the tracking error into contouring error, tangential error, and orientation error. Based on this transformation, each error component is treated independently according to their priorities. Furthermore, an extended state observer is designed to cope with not only unmeasurable velocities but also lumped disturbances and uncertainties. Finally, these advanced techniques are integrated into the proposed controller by using the backstepping control with the barrier Lyapunov function which is developed to achieve a prescribed performance of the contouring error. The proposed control algorithm guarantees system stability and provides high accuracy contouring performance and acceptable tangential and orientation performances regardless of the presence of lumped disturbances/uncertainties and nonlinearities in the system. Simulation results verify the control effectiveness of the proposed control algorithm in surface flattening tasks compared to previous works. Practitioners can apply the results of the research to not only semi-autonomous operations with unskilled operators but also fully autonomous operations. Future research is necessary to consider the contouring control of excavators with other earth-moving tasks and relating problems in real operating conditions.

ACS Style

Hoang Vu Dao; Seonjun Na; Duc Giap Nguyen; Kyoung Kwan Ahn. High accuracy contouring control of an excavator for surface flattening tasks based on extended state observer and task coordinate frame approach. Automation in Construction 2021, 130, 103845 .

AMA Style

Hoang Vu Dao, Seonjun Na, Duc Giap Nguyen, Kyoung Kwan Ahn. High accuracy contouring control of an excavator for surface flattening tasks based on extended state observer and task coordinate frame approach. Automation in Construction. 2021; 130 ():103845.

Chicago/Turabian Style

Hoang Vu Dao; Seonjun Na; Duc Giap Nguyen; Kyoung Kwan Ahn. 2021. "High accuracy contouring control of an excavator for surface flattening tasks based on extended state observer and task coordinate frame approach." Automation in Construction 130, no. : 103845.

Journal article
Published: 02 August 2021 in IEEE Access
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This article proposes a novel fault-tolerant controller for a double-rod electro-hydraulic actuator whilst the motion control system faces with system disturbances/uncertainties and internal leakage fault. Firstly, taking the advantage of the coordinate transformation, the nonlinear system is converted to a linear system to apply the control design tools in linear control theory. Besides, the matched, mismatched disturbances, and internal leakage fault are integrated into a new lumped uncertainty based on this transformation. Inspired by the great capability of time delay estimation technique, the suggested controller is developed to effectively detect and compensate for the internal leakage fault. To enhance the performance of the control system, an adaptive integral sliding mode control approach is deployed to effectively suppress the lump estimated error, and the effects of fault. The perfect combination of input-output feedback linearization, adaptive integral sliding mode, and time delay estimation is investigated to achieve high-precision tracking control and strong robustness in the presence of matched, mismatched disturbances, and faults, simultaneously. Moreover, the global stability of the suggested control algorithm is demonstrated by the Lyapunov theory. Finally, several tracking performance comparisons of the proposed approach with the existing controllers to demonstrate the efficiency are exhibited through simulation analyses and experiment results.

ACS Style

Van Du Phan; Cong Phat Vo; Hoang Vu Dao; Kyoung Kwan Ahn. Actuator Fault-Tolerant Control for an Electro-Hydraulic Actuator Using Time Delay Estimation and Feedback Linearization. IEEE Access 2021, 9, 107111 -107123.

AMA Style

Van Du Phan, Cong Phat Vo, Hoang Vu Dao, Kyoung Kwan Ahn. Actuator Fault-Tolerant Control for an Electro-Hydraulic Actuator Using Time Delay Estimation and Feedback Linearization. IEEE Access. 2021; 9 ():107111-107123.

Chicago/Turabian Style

Van Du Phan; Cong Phat Vo; Hoang Vu Dao; Kyoung Kwan Ahn. 2021. "Actuator Fault-Tolerant Control for an Electro-Hydraulic Actuator Using Time Delay Estimation and Feedback Linearization." IEEE Access 9, no. : 107111-107123.

Regular paper
Published: 14 July 2021 in International Journal of Precision Engineering and Manufacturing-Green Technology
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Wave energy is known to be a promising energy source for the goal of environmental protection and reducing dependence on fossil fuel sources. Hydraulic power-take-off (HPTO) is a key technology of wave energy converters which determines the energy recovery efficiency of the whole system. This paper presents a novel control strategy for HPTO to enhance the regenerated power and energy efficiency by using a suitable configuration of a variable displacement hydraulic motor and a generator. A control management strategy was designed to adjust the tilt angle of the hydraulic motor and the generator resistance load to maintain them working in the highest performance area under variable wave conditions. To verify the proposed system, a simulation model was built in AMESim software based on the previous experiment test bench configuration. Simulation results showed that by applying the proposed strategy, the generated energy increased during the working process. Compared with other control methods, the improvement of energy generation efficiency of the proposed control management method was approximately 10% higher in the low and medium wave conditions.

ACS Style

Tri Cuong Do; Tri Dung Dang; Kyoung Kwan Ahn. Efficiency Improvement of a Hydraulic Power Take-off of Wave Energy Converter Using Variable Displacement Motor. International Journal of Precision Engineering and Manufacturing-Green Technology 2021, 1 -13.

AMA Style

Tri Cuong Do, Tri Dung Dang, Kyoung Kwan Ahn. Efficiency Improvement of a Hydraulic Power Take-off of Wave Energy Converter Using Variable Displacement Motor. International Journal of Precision Engineering and Manufacturing-Green Technology. 2021; ():1-13.

Chicago/Turabian Style

Tri Cuong Do; Tri Dung Dang; Kyoung Kwan Ahn. 2021. "Efficiency Improvement of a Hydraulic Power Take-off of Wave Energy Converter Using Variable Displacement Motor." International Journal of Precision Engineering and Manufacturing-Green Technology , no. : 1-13.

Journal article
Published: 13 July 2021 in Composites Part B: Engineering
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Although liquid-solid triboelectric nanogenerator (LS-TENG) has been taken into consideration as a remarkable promising renewable clean energy source for electronic devices, their performances are still limited to be practically utilized owing to the weak polarity and inadequate functional groups of triboelectric materials. In this work, we propose a high-performance LS-TENG reached from surface polarity tuning through epitaxial growth on polyvinylidene fluoride (PVDF) membrane. The PVDF surface functional is treated with silica nanoparticles (SiNPs) through chemical bonding and then grafted with negatively charged 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (FOTS) to forming the FOTS/SiNPs/PVDF (FSiP) membrane. The proposed membrane can induce fluorine-bearing silane chains and increase the interfacial polarization, leading to the outstanding hydrophobic property and dielectric constant. In consequence, the output power of FSiP-TENG demonstrates superior triboelectric performance with a current of 5.79 μA, a voltage of 28.3 V, and the highest power density of 420 mW/m2, a 10.8 times improvement compared to the PVDF-TENG. Considering the excellent durability, stability, and water-resistant, the FSiP-TENG can develop into a water energy harvesting device and a liquid self-powered sensor to be used in our daily life.

ACS Style

Duy Linh Vu; Chau Duy Le; Cong Phat Vo; Kyoung Kwan Ahn. Surface polarity tuning through epitaxial growth on polyvinylidene fluoride membranes for enhanced performance of liquid-solid triboelectric nanogenerator. Composites Part B: Engineering 2021, 223, 109135 .

AMA Style

Duy Linh Vu, Chau Duy Le, Cong Phat Vo, Kyoung Kwan Ahn. Surface polarity tuning through epitaxial growth on polyvinylidene fluoride membranes for enhanced performance of liquid-solid triboelectric nanogenerator. Composites Part B: Engineering. 2021; 223 ():109135.

Chicago/Turabian Style

Duy Linh Vu; Chau Duy Le; Cong Phat Vo; Kyoung Kwan Ahn. 2021. "Surface polarity tuning through epitaxial growth on polyvinylidene fluoride membranes for enhanced performance of liquid-solid triboelectric nanogenerator." Composites Part B: Engineering 223, no. : 109135.

Journal article
Published: 02 July 2021 in Energy Conversion and Management
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An innovative hydraulic hybrid excavator is proposed in this paper to save energy. An electrical hydraulic continually variable powertrain is proposed to drive the main pump, in which both the speed and torque of the engine can be controlled to ensure that the engine working points lie in the high efficiency range with the proposed energy management strategy. An energy regeneration system is adopted to regenerate the potential energy. In addition, an innovative equivalent consumption minimization strategy is formulated to calculate the control commands of the engine, motor/generator, and hydraulic pump to reduce the energy consumption of the system. A test bench is established, and experiments are conducted to verify the energy saving efficiency of the proposed system. As a result, the energy saving efficiency ranges from 36.69% to 45.16%. The fuel consumption and emission of hydraulic excavator are reduced effectively with the proposed system.

ACS Style

Yingxiao Yu; Tri Cuong Do; Yongsoo Park; Kyoung Kwan Ahn. Energy saving of hybrid hydraulic excavator with innovative powertrain. Energy Conversion and Management 2021, 244, 114447 .

AMA Style

Yingxiao Yu, Tri Cuong Do, Yongsoo Park, Kyoung Kwan Ahn. Energy saving of hybrid hydraulic excavator with innovative powertrain. Energy Conversion and Management. 2021; 244 ():114447.

Chicago/Turabian Style

Yingxiao Yu; Tri Cuong Do; Yongsoo Park; Kyoung Kwan Ahn. 2021. "Energy saving of hybrid hydraulic excavator with innovative powertrain." Energy Conversion and Management 244, no. : 114447.

Journal article
Published: 08 June 2021 in IEEE Access
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This paper presents a fault-tolerant control (FTC) based on impedance control and full state feedback backstepping sliding mode control (FBSMC) algorithm for an n degree of freedoms (n-DOF) serial hydraulic manipulator under the presence of matched and mismatched uncertainties and sensor faults in the constrained framework. These faulty signals, generated from unknown constant or time-variant offset values, happen on both manipulator joint angles and force sensors; thereby degrading the system performance. Therefore, to address both matched and mismatched uncertainties and signal faults, the system dynamics subjects to the sensor faults is mathematically modeled. Then, the robust fault estimation algorithm based on extended state observer (ESO) is proposed to estimate the system state and faulty signals for the FTC design to achieve the force and position tracking performance. System stability of the proposed control scheme is theoretically proven by performing Lyapunov theorems. Finally, comparative simulation results are given on a 3-DOF serial hydraulic manipulator to evaluate the effectiveness of the proposed fault estimation and FTC methodology.

ACS Style

Hoai Vu Anh Truong; Hoai An Trinh; Duc Thien Tran; Kyoung Kwan Ahn. A Robust Observer for Sensor Faults Estimation on n-DOF Manipulator in Constrained Framework Environment. IEEE Access 2021, 9, 88439 -88451.

AMA Style

Hoai Vu Anh Truong, Hoai An Trinh, Duc Thien Tran, Kyoung Kwan Ahn. A Robust Observer for Sensor Faults Estimation on n-DOF Manipulator in Constrained Framework Environment. IEEE Access. 2021; 9 ():88439-88451.

Chicago/Turabian Style

Hoai Vu Anh Truong; Hoai An Trinh; Duc Thien Tran; Kyoung Kwan Ahn. 2021. "A Robust Observer for Sensor Faults Estimation on n-DOF Manipulator in Constrained Framework Environment." IEEE Access 9, no. : 88439-88451.

Journal article
Published: 29 May 2021 in Journal of Sound and Vibration
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Pneumatic springs have been used for the automotive suspension to induce a flexible stiffness and create the control forces according to various uncertain masses of passengers and exogenous inputs. However, the control of the vehicle suspension system using the pneumatic spring is a very complicated task because it involves parametric uncertainties, external disturbances, and system nonlinearities. In this paper, an adaptive sliding mode control (SMC) based on nonlinear disturbance observer (NDOB) is designed to obtain passenger comfort and keep the driving safety of the pneumatic active suspension. The nonlinear disturbance observer is proposed to asymptotically reject the external disturbances and overcome parametric uncertainties which exist in the suspension system such as road profiles, different passenger masses, and actuator dynamics. Finally, comparative simulations and experimental results are given and compared by the pneumatic vehicle suspension test bench to demonstrate the efficiency of the proposed SMC - NDOB scheme for different road conditions. Results show that the RMS acceleration value is decreased by 41.5% when the proposed control is used for the experiment with the bump road profile.

ACS Style

Cong Minh Ho; Duc Thien Tran; Kyoung Kwan Ahn. Adaptive sliding mode control based nonlinear disturbance observer for active suspension with pneumatic spring. Journal of Sound and Vibration 2021, 509, 116241 .

AMA Style

Cong Minh Ho, Duc Thien Tran, Kyoung Kwan Ahn. Adaptive sliding mode control based nonlinear disturbance observer for active suspension with pneumatic spring. Journal of Sound and Vibration. 2021; 509 ():116241.

Chicago/Turabian Style

Cong Minh Ho; Duc Thien Tran; Kyoung Kwan Ahn. 2021. "Adaptive sliding mode control based nonlinear disturbance observer for active suspension with pneumatic spring." Journal of Sound and Vibration 509, no. : 116241.

Review
Published: 12 April 2021 in Renewable and Sustainable Energy Reviews
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Construction machinery, especially hydraulic excavators, plays an important role in building and other industries. However, they often consume a lot of energy and emit large amounts of harmful emissions into the environment. This study focuses on energy regeneration technologies which can help reduce energy consumption and pollution in hydraulic excavators. First, potential recoverable energy sources in excavator mechanisms are analyzed. Next, energy regeneration systems are classified according to energy storage devices and their development is comprehensively reviewed through the state-of-art. The research gaps, market opportunities and future development directions of energy regeneration systems are discussed to underpin future development opportunities. A new conceptual design of ERS has been proposed to improve the energy regeneration efficiency whilst minimising the power consumption of hydraulic excavators.

ACS Style

Tri Cuong Do; Tri Dung Dang; Truong Quang Dinh; Kyoung Kwan Ahn. Developments in energy regeneration technologies for hydraulic excavators: A review. Renewable and Sustainable Energy Reviews 2021, 145, 111076 .

AMA Style

Tri Cuong Do, Tri Dung Dang, Truong Quang Dinh, Kyoung Kwan Ahn. Developments in energy regeneration technologies for hydraulic excavators: A review. Renewable and Sustainable Energy Reviews. 2021; 145 ():111076.

Chicago/Turabian Style

Tri Cuong Do; Tri Dung Dang; Truong Quang Dinh; Kyoung Kwan Ahn. 2021. "Developments in energy regeneration technologies for hydraulic excavators: A review." Renewable and Sustainable Energy Reviews 145, no. : 111076.

Journal article
Published: 06 April 2021 in IEEE Access
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In this paper, an adaptive neural command filtered backstepping scheme is proposed for the pneumatic active suspension with the vertical displacement constraint of sprung mass and actuator saturation. A quarter car model with a pneumatic spring is first fabricated on the basis of thermodynamic theory to describe the dynamic characteristics. To overcome the lumped unknown nonlinearities and enhance the requirement of modeling precision, the radial basis function neural networks (RBFNNs) are proposed to approximate unknown continuous functions caused by the uncertain body mass and other factors of pneumatic spring. To solve the explosion of complexity problem in the traditional backstepping designs, a proposed command filter control is applied by using the Levant differentiators which approach the derivative of the virtual control signals. Nussbaum gain technique is then incorporated into the controller to avoid the problem of the completely unknown control gain and control directions of a pneumatic actuator. In addition, the prescribed performance function (PPF) is suggested to guarantee that the tracking error of the sprung mass displacement does not violate the constraint boundaries. Based on the command filtered backstepping control with PPF, the Lyapunov theorem is then applied to indicate the system stability analysis. Finally, the comparative simulation examples for the pneumatic suspension are given to verify the effectiveness and reliability of the proposed control.

ACS Style

Cong Minh Ho; Duc Thien Tran; Cong Hung Nguyen; Kyoung Kwan Ahn. Adaptive Neural Command Filtered Control for Pneumatic Active Suspension With Prescribed Performance and Input Saturation. IEEE Access 2021, 9, 56855 -56868.

AMA Style

Cong Minh Ho, Duc Thien Tran, Cong Hung Nguyen, Kyoung Kwan Ahn. Adaptive Neural Command Filtered Control for Pneumatic Active Suspension With Prescribed Performance and Input Saturation. IEEE Access. 2021; 9 (99):56855-56868.

Chicago/Turabian Style

Cong Minh Ho; Duc Thien Tran; Cong Hung Nguyen; Kyoung Kwan Ahn. 2021. "Adaptive Neural Command Filtered Control for Pneumatic Active Suspension With Prescribed Performance and Input Saturation." IEEE Access 9, no. 99: 56855-56868.

Journal article
Published: 16 February 2021 in IEEE Access
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In this paper, a novel adaptive fault-tolerant controller is proposed for a typical electro-hydraulic rotary actuator in the presence of disturbances, internal leakage fault, and sensor fault simultaneously. To construct the suggested controller, a nonlinear unknown input observer is developed to effectively identify the sensor fault, which is unaffected by not only internal leakage fault but also mismatched disturbances/uncertainties. Furthermore, a radial basis function neural network is designed to compensate for the mismatched disturbances/uncertainties caused by payload variation and unknown friction nonlinearities. Besides, an adaptive law based on the projection mapping function is applied to tackle the effect of the internal leakage fault. The integration of the above-mentioned techniques into the adaptive backstepping terminal sliding mode is investigated to obtain high tracking performance, robustness as well as fast convergence. The stability of the closed-loop system is proven by the Lyapunov theory. Finally, the capability and effectiveness of the proposed approach are validated via simulation results under various faulty scenarios.

ACS Style

Van Du Phan; Cong Phat Vo; Hoang Vu Dao; Kyoung Kwan Ahn. Robust Fault-Tolerant Control of an Electro-Hydraulic Actuator With a Novel Nonlinear Unknown Input Observer. IEEE Access 2021, 9, 30750 -30760.

AMA Style

Van Du Phan, Cong Phat Vo, Hoang Vu Dao, Kyoung Kwan Ahn. Robust Fault-Tolerant Control of an Electro-Hydraulic Actuator With a Novel Nonlinear Unknown Input Observer. IEEE Access. 2021; 9 (99):30750-30760.

Chicago/Turabian Style

Van Du Phan; Cong Phat Vo; Hoang Vu Dao; Kyoung Kwan Ahn. 2021. "Robust Fault-Tolerant Control of an Electro-Hydraulic Actuator With a Novel Nonlinear Unknown Input Observer." IEEE Access 9, no. 99: 30750-30760.

Regular paper
Published: 08 February 2021 in International Journal of Precision Engineering and Manufacturing
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The paper addresses an adaptive robust position control for tracking control of a manipulator under the presence of the uncertainties, such as variant payload, modeling error, friction, and external disturbance. The proposed control uses radial basis function neural networks (RBFNN)s to approximate and cancel the uncertainties. The nonsingular fast terminal sliding mode control (NFTSMC) of the proposed control is developed to guarantees a finite-time convergence and to solve the singular issue of the terminal sliding mode control. Moreover, the learning laws are derived from the Lyapunov approach to ensure the stability and robustness of the whole system. The proposed control is compared with other controllers through both simulations and experiments on a 3-DOF manipulator to exhibit its efficiency with the variant payload and the uncertainties.

ACS Style

Duc-Thien Tran; Hoai-Vu-Anh Truong; Kyoung Kwan Ahn. Adaptive Nonsingular Fast Terminal Sliding mode Control of Robotic Manipulator Based Neural Network Approach. International Journal of Precision Engineering and Manufacturing 2021, 22, 417 -429.

AMA Style

Duc-Thien Tran, Hoai-Vu-Anh Truong, Kyoung Kwan Ahn. Adaptive Nonsingular Fast Terminal Sliding mode Control of Robotic Manipulator Based Neural Network Approach. International Journal of Precision Engineering and Manufacturing. 2021; 22 (3):417-429.

Chicago/Turabian Style

Duc-Thien Tran; Hoai-Vu-Anh Truong; Kyoung Kwan Ahn. 2021. "Adaptive Nonsingular Fast Terminal Sliding mode Control of Robotic Manipulator Based Neural Network Approach." International Journal of Precision Engineering and Manufacturing 22, no. 3: 417-429.

Journal article
Published: 22 January 2021 in Actuators
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In this paper, an active disturbance rejection control is designed to improve the position tracking performance of an electro-hydraulic actuation system in the presence of parametric uncertainties, non-parametric uncertainties, and external disturbances as well. The disturbance observers (Dos) are proposed to estimate not only the matched lumped uncertainties but also mismatched disturbance. Without the velocity measurement, the unmeasurable angular velocity is robustly calculated based on the high-order Levant’s exact differentiator. These disturbances and angular velocity are integrated into the control design system based on the backstepping framework which guarantees high-accuracy tracking performance. The system stability analysis is analyzed by using the Lyapunov theory. Simulations based on an electro-hydraulic rotary actuator are conducted to verify the effectiveness of the proposed control method.

ACS Style

Manh Nguyen; Hoang Dao; Kyoung Ahn. Active Disturbance Rejection Control for Position Tracking of Electro-Hydraulic Servo Systems under Modeling Uncertainty and External Load. Actuators 2021, 10, 20 .

AMA Style

Manh Nguyen, Hoang Dao, Kyoung Ahn. Active Disturbance Rejection Control for Position Tracking of Electro-Hydraulic Servo Systems under Modeling Uncertainty and External Load. Actuators. 2021; 10 (2):20.

Chicago/Turabian Style

Manh Nguyen; Hoang Dao; Kyoung Ahn. 2021. "Active Disturbance Rejection Control for Position Tracking of Electro-Hydraulic Servo Systems under Modeling Uncertainty and External Load." Actuators 10, no. 2: 20.

Journal article
Published: 22 January 2021 in IEEE Access
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In this paper, an active fault-tolerant control (FTC) system design is proposed for an n-degree-of-freedom (n-DOF) hydraulic manipulator with internal leakage faults and mismatched/matched lumped disturbances. A pair of matched and mismatched disturbance observers (DOBs) is proposed to simultaneously estimate and compensate for the effects of matched/mismatched disturbances on the control system in healthy conditions. The fault detection is achieved when the estimated matched disturbance is larger than a threshold. After that, a novel control reconfiguration law is designed to switch from a normal controller to a fault-tolerant controller with an online identification algorithm based on an adaptive mechanism. The proposed active FTC guarantees the position tracking performance in not only single-fault but also simultaneous-faults conditions. Moreover, the problem of uniting disturbance-observer-based control for external disturbance and adaptive control for parametric uncertainty is solved in a novel approach. Simulation results are conducted in a two-degree-of-freedom hydraulic leg prototype, which verifies the effectiveness of the proposed method.

ACS Style

Hoang Vu Dao; Duc Thien Tran; Kyoung Kwan Ahn. Active Fault Tolerant Control System Design for Hydraulic Manipulator With Internal Leakage Faults Based on Disturbance Observer and Online Adaptive Identification. IEEE Access 2021, 9, 23850 -23862.

AMA Style

Hoang Vu Dao, Duc Thien Tran, Kyoung Kwan Ahn. Active Fault Tolerant Control System Design for Hydraulic Manipulator With Internal Leakage Faults Based on Disturbance Observer and Online Adaptive Identification. IEEE Access. 2021; 9 ():23850-23862.

Chicago/Turabian Style

Hoang Vu Dao; Duc Thien Tran; Kyoung Kwan Ahn. 2021. "Active Fault Tolerant Control System Design for Hydraulic Manipulator With Internal Leakage Faults Based on Disturbance Observer and Online Adaptive Identification." IEEE Access 9, no. : 23850-23862.

Research article
Published: 18 January 2021 in International Journal of Energy Research
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Over the past few years, triboelectric nanogenerators (TENGs) have emerged as promising devices for energy harvesting and self‐powered sensing owing to their miniaturized structural design, lack of material limitation, high stability, and eco‐friendly nature. In this study, the membrane consisting of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) and ionic liquid (PIL) is fabricated as triboelectric material, namely PIL membrane. To further improve the hydrophobicity of the membrane and the output performance of the TENG, different PIL membranes are prepared using various IL concentrations and their structures are modified using the evaporation phase inversion technique. The PIL membranes with nanoporous structures and strong hydrophobicity are synthesized by blade coating and bent to generate circular tube shapes for use in PIL‐TENG cells. Therefore, the PIL‐TENG has a high output performance owing to the availability of more ions through the establishment of an electrical double layer and an increase in electronegativity properties by doping with more fluoride atoms. Under optimal conditions, a nanoporous PIL‐TENG of 10 wt.% ionic liquid exhibited the maximum peak‐to‐peak with an output voltage of 16.95 V and current of 2.56 μA. Especially, the instantaneous peak power density of the PIL‐TENG reached the highest value of 26.1 mW/m2, which was 212% higher than that of the pristine PVDF‐HFP TENG (P‐TENG). In this manner, a new material for the triboelectric layer is presented to effectively improve the output performance, stability, and durability of TENGs, which are promising for use in practical applications related to harvesting hydrokinetic energy, self‐powered sensors, and other applications.

ACS Style

Duy Linh Vu; Cong Phat Vo; Chau Duy Le; Kyoung Kwan Ahn. Enhancing the output performance of fluid‐based triboelectric nanogenerator by using poly(vinylidene fluoride‐co‐hexafluoropropylene)/ionic liquid nanoporous membrane. International Journal of Energy Research 2021, 45, 8960 -8970.

AMA Style

Duy Linh Vu, Cong Phat Vo, Chau Duy Le, Kyoung Kwan Ahn. Enhancing the output performance of fluid‐based triboelectric nanogenerator by using poly(vinylidene fluoride‐co‐hexafluoropropylene)/ionic liquid nanoporous membrane. International Journal of Energy Research. 2021; 45 (6):8960-8970.

Chicago/Turabian Style

Duy Linh Vu; Cong Phat Vo; Chau Duy Le; Kyoung Kwan Ahn. 2021. "Enhancing the output performance of fluid‐based triboelectric nanogenerator by using poly(vinylidene fluoride‐co‐hexafluoropropylene)/ionic liquid nanoporous membrane." International Journal of Energy Research 45, no. 6: 8960-8970.

Journal article
Published: 22 December 2020 in Actuators
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In this paper, a novel design of an energy regeneration system was proposed for recovering as well as reusing potential energy in a boom cylinder. The proposed system included a hydraulic pump/motor and an electrical motor/generator. When the boom moved down, the energy regeneration components converted the hydraulic energy to electrical energy and stored in a battery. Then, the regenerated energy was reused at subsequent cycles. In addition, an energy management strategy has been designed based on discrete time-optimal control to guarantee position tracking performance and ensure component safety during the operation. To verify the effectiveness of the proposed system, a co-simulation (using MATLAB and AMESim) was carried out. Through the simulation results, the maximum energy regeneration efficiency could achieve up to 44%. Besides, the velocity and position of the boom cylinder achieved good performance with the proposed control strategy.

ACS Style

Tri Cuong Do; Duc Giap Nguyen; Tri Dung Dang; Kyoung Kwan Ahn. A Boom Energy Regeneration System of Hybrid Hydraulic Excavator Using Energy Conversion Components. Actuators 2020, 10, 1 .

AMA Style

Tri Cuong Do, Duc Giap Nguyen, Tri Dung Dang, Kyoung Kwan Ahn. A Boom Energy Regeneration System of Hybrid Hydraulic Excavator Using Energy Conversion Components. Actuators. 2020; 10 (1):1.

Chicago/Turabian Style

Tri Cuong Do; Duc Giap Nguyen; Tri Dung Dang; Kyoung Kwan Ahn. 2020. "A Boom Energy Regeneration System of Hybrid Hydraulic Excavator Using Energy Conversion Components." Actuators 10, no. 1: 1.

Journal article
Published: 18 December 2020 in Actuators
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Inspired by improving the adaptive capability of the robot to external impacts or shocks, the adjustable stiffness behavior in joints is investigated to ensure conformity with the safety index. This paper proposes a new soft actuation unit, namely Adjustable Stiffness Rotary Actuator (ASRA), induced by a novel optimization of the elastic energy in an adjusting stiffness mechanism. Specifically, a stiffness transmission is configured by three pairs of antagonistically linear springs with linkage bars. The rotational disk and link bars assist the simplified stiffness control based on a linear transmission. To enhance the elastic energy efficiency, the force compressions of the linear springs are set to be perpendicular to the three-spoke output element, i.e., the output link direction. Besides, the ASRA model is also formed to investigate the theoretical capabilities of the stiffness output and passive energy. As a simulated result, a high passive energy storage ability can be achieved. Then, several experimental scenarios are performed with integral sliding mode controllers to verify the physical characteristics of the ASRA. As trial results, the fast transient response and high accuracy of both the position and stiffness tracking tests are expressed, in turn, independent and simultaneous control cases. Moreover, the real output torque is measured to investigate its reflecting stiffness.

ACS Style

Cong Phat Vo; Van Du Phan; Thanh Ha Nguyen; Kyoung Kwan Ahn. A Compact Adjustable Stiffness Rotary Actuator Based on Linear Springs: Working Principle, Design, and Experimental Verification. Actuators 2020, 9, 141 .

AMA Style

Cong Phat Vo, Van Du Phan, Thanh Ha Nguyen, Kyoung Kwan Ahn. A Compact Adjustable Stiffness Rotary Actuator Based on Linear Springs: Working Principle, Design, and Experimental Verification. Actuators. 2020; 9 (4):141.

Chicago/Turabian Style

Cong Phat Vo; Van Du Phan; Thanh Ha Nguyen; Kyoung Kwan Ahn. 2020. "A Compact Adjustable Stiffness Rotary Actuator Based on Linear Springs: Working Principle, Design, and Experimental Verification." Actuators 9, no. 4: 141.

Journal article
Published: 05 December 2020 in Actuators
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This paper proposes a fault estimation and fault-tolerant control strategy with two observers for a pump-controlled electro-hydraulic system (PCEHS) under the presence of internal leakage faults and an external loading force. The mathematical model of the PCEHS is dedicatedly derived in the state-space form for developing control methodology. Two different observers are developed in which an extended state observer is applied to estimate the internal leakage flow rate, and a disturbance observer is used to deal with the external loading force. Then, the proposed control is designed based on the backstepping sliding mode technique in which estimated information from the observers is taken into consideration to guarantee the working performance of the system. With the proposed methodology, the robustness and stability of the controlled system are theoretically analyzed and proven by the Lyapunov theorem. Comparative simulation results are given to demonstrate the effectiveness of the proposed methodology through different testing conditions.

ACS Style

Hoai-An Trinh; Hoai Vu Anh Truong; Kyoung Kwan Ahn. Fault Estimation and Fault-Tolerant Control for the Pump-Controlled Electrohydraulic System. Actuators 2020, 9, 132 .

AMA Style

Hoai-An Trinh, Hoai Vu Anh Truong, Kyoung Kwan Ahn. Fault Estimation and Fault-Tolerant Control for the Pump-Controlled Electrohydraulic System. Actuators. 2020; 9 (4):132.

Chicago/Turabian Style

Hoai-An Trinh; Hoai Vu Anh Truong; Kyoung Kwan Ahn. 2020. "Fault Estimation and Fault-Tolerant Control for the Pump-Controlled Electrohydraulic System." Actuators 9, no. 4: 132.

Journal article
Published: 16 November 2020 in Applied Sciences
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In consideration of accidental contact-loss due to step-change or accidentally moving out of a constrained framework, this paper focuses on solving this problem during working processes of an n-degree-of-freedom hydraulic manipulator (n-DOF manipulator). In order to overcome this phenomenon, a fault detection methodology-based virtual energy tank is employed with a shaping function to prevent the end-effector from damage or unexpected motion. This technique helps to detect when the contact-loss happens by a virtual energy variable; thus, decoupling a force control regulation. Moreover, a new trajectory for smooth motion after contact-loss detection is also discussed to increase system robustness. Additionally, to enhance tracking performance, adaptive laws are designed to compensate for system uncertainties. Comparative simulations are given on the n-DOF hydraulic manipulator to evaluate effectiveness of the impedance-based energy tank methodology under the sudden step-changed environment. Moreover, influences of control gains and setup energy parameters to the system behaviors when contact-loss happens are remarkably discussed as indispensable criteria for further development. The simulated results certified the superior effectiveness and reliability of the suggested methodology over the conventional impedance control for safe operation.

ACS Style

Hoai Vu Anh Truong; Hoai-An Trinh; Kyoung Kwan Ahn. Safety Operation of n-DOF Serial Hydraulic Manipulator in Constrained Motion with Consideration of Contact-Loss Fault. Applied Sciences 2020, 10, 8107 .

AMA Style

Hoai Vu Anh Truong, Hoai-An Trinh, Kyoung Kwan Ahn. Safety Operation of n-DOF Serial Hydraulic Manipulator in Constrained Motion with Consideration of Contact-Loss Fault. Applied Sciences. 2020; 10 (22):8107.

Chicago/Turabian Style

Hoai Vu Anh Truong; Hoai-An Trinh; Kyoung Kwan Ahn. 2020. "Safety Operation of n-DOF Serial Hydraulic Manipulator in Constrained Motion with Consideration of Contact-Loss Fault." Applied Sciences 10, no. 22: 8107.

Journal article
Published: 04 November 2020 in Nano Energy
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Triboelectric nanogenerators (TENGs) for scavenging mechanical energy has been conducted over the past decade with respectable successes. Up to now, the solid-solid TENG has been the dominant side but themselves still have their own drawbacks; thus, the liquid-solid TENG has got attention instead. Here we developed a discontinuous-conduction-based rotary triboelectric nanogenerator based on the liquid-solid electrification. By using the motion-activated switch structure, the induced charges can accumulate on one electrode and then release to another electrode at a specifically designated position. Taking advantage of this process, we can maximize the charge transfer per cycle which also improves the output performance of the developed TENG.

ACS Style

Chau-Duy Le; Cong-Phat Vo; Thanh-Ha Nguyen; Duy-Linh Vu; Kyoung Kwan Ahn. Liquid-solid contact electrification based on discontinuous-conduction triboelectric nanogenerator induced by radially symmetrical structure. Nano Energy 2020, 80, 105571 .

AMA Style

Chau-Duy Le, Cong-Phat Vo, Thanh-Ha Nguyen, Duy-Linh Vu, Kyoung Kwan Ahn. Liquid-solid contact electrification based on discontinuous-conduction triboelectric nanogenerator induced by radially symmetrical structure. Nano Energy. 2020; 80 ():105571.

Chicago/Turabian Style

Chau-Duy Le; Cong-Phat Vo; Thanh-Ha Nguyen; Duy-Linh Vu; Kyoung Kwan Ahn. 2020. "Liquid-solid contact electrification based on discontinuous-conduction triboelectric nanogenerator induced by radially symmetrical structure." Nano Energy 80, no. : 105571.

Regular paper
Published: 29 October 2020 in International Journal of Precision Engineering and Manufacturing-Green Technology
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The hydraulic power take-off (HPTO) is considered as the most promising method to convert wave power to electrical power. This paper presents an experimental assessment of the power conversion of a wave energy converter using HPTO. Based on the experimental results, a modification of accumulator pre-charged pressure and a control strategy were proposed to improve the system performance. System design, the working principle and mathematical model of all components were described. The proposed method was verified based on both simulation and experimental tests. The results showed that the system always works at an optimal condition under different input wave conditions.

ACS Style

Tri Dung Dang; Tri Cuong Do; Kyoung Kwan Ahn. Experimental Assessment of the Power Conversion of a Wave Energy Converter Using Hydraulic Power Take-Off Mechanism. International Journal of Precision Engineering and Manufacturing-Green Technology 2020, 1 -13.

AMA Style

Tri Dung Dang, Tri Cuong Do, Kyoung Kwan Ahn. Experimental Assessment of the Power Conversion of a Wave Energy Converter Using Hydraulic Power Take-Off Mechanism. International Journal of Precision Engineering and Manufacturing-Green Technology. 2020; ():1-13.

Chicago/Turabian Style

Tri Dung Dang; Tri Cuong Do; Kyoung Kwan Ahn. 2020. "Experimental Assessment of the Power Conversion of a Wave Energy Converter Using Hydraulic Power Take-Off Mechanism." International Journal of Precision Engineering and Manufacturing-Green Technology , no. : 1-13.