Robotics and Mechatronics
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Browsing Robotics and Mechatronics by Author "Do, Ton Duc"
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Item Open Access A Nonlinear Sliding Mode Controller for IPMSM Drives with an Adaptive Gain Tuning Rule(2015) Jung, Jin-Woo; Dang, Dong Quang; Vu, Nga Thi-Thuy; Justo, Jackson John; Do, Ton Duc; Choi, Han Ho; Kim, Tae HeoungThis paper presents a nonlinear sliding mode control (SMC) scheme with a variable damping ratio for interior permanent magnet synchronous motors (IPMSMs). First, a nonlinear sliding surface whose parameters change continuously with time is designed. Actually, the proposed SMC has the ability to reduce the settling time without an overshoot by giving a low damping ratio at the initial time and a high damping ratio as the output reaches the desired setpoint. At the same time, it enables a fast convergence in finite time and eliminates the singularity problem with the upper bound of an uncertain term, which cannot be measured in practice, by using a simple adaptation law. To improve the efficiency of a system in the constant torque region, the control system incorporates the maximum torque per ampere (MTPA) algorithm. The stability of the nonlinear sliding surface is guaranteed by Lyapunov stability theory. Moreover, a simple sliding mode observer is used to estimate the load torque and system uncertainties. The effectiveness of the proposed nonlinear SMC scheme is verified using comparative experimental results of the linear SMC scheme when the speed reference and load torque change under system uncertainties. From these experimental results, the proposed nonlinear SMC method reveals a faster transient response, smaller steady-state speed error, and less sensitivity to system uncertainties than the linear SMC methodItem Open Access Adaptive PID Speed Control Design for Permanent Magnet Synchronous Motor Drives(2014) Jung, Jin-Woo; Leu, Viet Quoc; Do, Ton Duc; Kim, Eun-Kyung; Choi, Han Ho; Leu, Viet QuocThis paper proposes an adaptive proportionalintegralderivative (PID) speed control scheme for permanent magnet synchronous motor (PMSM) drives. The proposed controller consists of three control terms: a decoupling term, a PID term, and a supervisory term. The first control term is employed to compensate for the nonlinear factors, the second term is made to automatically adjust the control gains, and the third one is designed to guarantee the system stability. Different from the offline-tuning PID controllers, the proposed adaptive controller includes adaptive tuning laws to online adjust the control gains based on the gradient descent method. Thus, it can adaptively deal with any system parameter uncertainties in reality. The proposed scheme is not only simple and easy to implement, but also it guarantees an accurate and fast speed tracking. It is proven that the control system is asymptotically stable. To confirm the effectiveness of the proposed algorithm, the comparative experiments between the proposed adaptive PID controller and the conventional PID controller are performed on the PMSM drive. Finally, it is validated that the proposed design scheme accomplishes the superior control performance (faster transient response and smaller steady-state error) compared to the conventional PID method in the presence of parameter uncertaintiesItem Open Access An Adaptive Voltage Control Strategy of Three- Phase Inverter for Standalone Distributed Generation Systems(2012) Do, Ton Duc; Leu, Viet Quoc; Choi, Young-Sik; Choi, Han Ho; Jung, Jin-WooThis paper proposes an adaptive control method of three-phase inverter for standalone distributed generation systems (DGSs). The proposed voltage controller includes two control terms: an adaptive compensating term and a stabilizing term. The adaptive compensating control term is constructed to avoid directly calculating the time derivatives of state variables. Meanwhile, the stabilizing control term is designed to asymptotically stabilize the error dynamics of the system. Also, a fourth-order optimal load current observer is proposed to reduce the number of current sensors and enhance the system reliability and cost effectiveness. Stability of the proposed voltage controller and the proposed load current observer is fully proven by using Lyapunov theory. The proposed control system can establish good voltage regulation such as fast dynamic response, small steady state error, and low total harmonic distortion (THD) under sudden load change, unbalanced load, and nonlinear load. Finally, the validity of the proposed control strategy is verified through simulations and experiments on a prototype DGS testbed with a TMS320F28335 DSP. For a comparative study, the feedback linearization for multi-input and multi-output (FLMIMO) control scheme is implemented and its results are presented in this paperItem Open Access An Electromagnetic Steering System for Magnetic Nanoparticle Drug Delivery(2015) Do, Ton Duc; Noh, Yeongil; Kim, Myeong Ok; Yoon, JungwonTargeted delivery of pharmaceutical agents to the brain using magnetic nanoparticles (MNPs) is an efficient technique to transport molecules to disease locations. MNPs can cross the blood–brain barrier (BBB) and can be concentrated at a specific location in the brain using non-invasive electromagnetic forces. The proposed EMA consists of two coil-core system. The cores are added in the center of each coil to concentrate the flux in the region of interest. The EMA can enhance the gradient field 10 times compared to only coil system and generate the maximum magnetic field of 160 mT and 5.6 T/m. A 12-kW direct-current power supply was used to generate sufficient magnetic forces on the MNPs by regulating the input currents of the coils. Effective guidance of MNPs is demonstrated via simulations and experiments using 800-nm-diameter MNPs in a Y-shaped channel. The developed EMA system has high potentials to increase BBB crossing of MNPs for efficient drug targeting to brain regionsItem Open Access An Optimized Field Function Scheme for Nanoparticle Guidance in Magnetic Drug Targeting systems(IEEE, 2015) Do, Ton Duc; Noh, Yeongil; Kim, Myeong Ok; Yoon, JungwonMagnetic drug targeting is an approach to guide and concentrate magnetic nanoparticles (MNPs) into the diseased target organ after being injected into blood vessels. Although many works for drug targeting have been conducted, there are few studies on delivering the nanoparticles to the target region. Drug delivery performance has not been addressed sufficiently or fully. In this paper, we investigate the effect of dominant factors to MNPs delivery performance. Then, an optimized field function scheme with a pulsed magnetic actuation is proposed to significantly improve the MNPs guidance performance. With a specific condition of blood vessel size, particle size, and applied magnetic field, the optimized parameters of the field function are selected through extensive simulation studies. We find out that the optimal negative and positive time for the magnetic pulsed field mainly depends on the exit time for particles to reach the bifurcation and the critical time as the maximum time for them to reach the vessels wall, respectively. With the chosen parameters, we show that ratios of correctly guided particles in a Y-channel are reached to 100%. In addition, to minimize the power consumption, a modified field function (MFF) scheme is introduced. The MFF includes a no-power time, called zero-time, between the positive and negative time. It is shown that with the proposed MFF, the energy consumption and the heating problem of the actuator system can be significantly reduced. Therefore, the proposed guidance scheme for MNPs can overcome the sticking issue and maximize the guidance performance as well as reducing the power consumption. It should be noted that the MFF can be easily implement by programmable DC power supplies connected to electromagnetic coilsItem Open Access Asymptotic Vision-Based Tracking Control of the Quadrotor Aerial Vehicle(2015) Asl, Hamed Jabbari; Do, Ton DucThis paper proposes an image-based visual servo (IBVS) controller for the 3D translational motion of the quadrotor unmanned aerial vehicle (UAV). The main purpose of this paper is to provide asymptotic stability for vision-based tracking control of the quadrotor in the presence of uncertainty in the dynamic model of the system. The aim of the paper also includes the use of ow of image features as the velocity information to compensate for the unreliable linear velocity data measured by accelerometers. For this purpose, the mathematical model of the quadrotor is presented based on the optic ow of image features which provides the possibility of designing a velocity-free IBVS controller with considering the dynamics of the robot. The image features are de ned from a suitable combination of perspective image moments without using the model of the object. This property allows the application of the proposed controller in unknown places. The controller is robust with respect to the uncertainties in the transla- tional dynamics of the system associated with the target motion, image depth and external disturbances. Simulation results and a comparison study are presented which demonstrate the e ectiveness of the proposed approach.Item Open Access Disturbance Observer-Based Fuzzy SMC of WECSs Without Wind Speed Measurement(IEEE Access, 2017-02-25) Do, Ton DucThe main role of control system for wind turbines is tracking the optimal power via regulating the rotor speed of the generator. A high performance controller, which can deal with unmodeled dynamics, uncertainties, and external disturbance, can effectively increase the captured power from the wind. This paper focuses on designing an advanced sliding mode control (SMC) scheme for wind energy conversion systems (WECSs). As the proposed SMC scheme includes a nonlinear disturbance observer (DOB) for estimating aerodynamic torque and wind speed, there is no requirement to measure aerodynamic torque or wind speed. The proposed control scheme considers not only the uncertainties and disturbance but also the random nature of wind speed and intrinsic nonlinear behavior of the WESCs. Via designing sliding surface based on estimated information, the proposed control system can avoid disadvantages associated with the robust control techniques. To totally remove chattering as well as improving other control criteria, a fuzzybased variable switching gain scheme is introduced. Comparative simulation results are shown to verify the effectiveness and superior performance of the proposed DOB-based fuzzy SMC scheme.Item Open Access Functionalized Magnetic Force Enhances Magnetic Nanoparticle Guidance: From Simulation to Crossing of the Blood-Brain Barrier in vivo(2016) Do, Ton Duc; Amin, Faiz Ul; Noh, Yeongil; Kim, Myeong Ok; Yoon, JungwonIn recent studies, we introduced the concept of functionalized magnetic force as a method to prevent nanoparticles from sticking to vessel walls caused by extensive simulation and in vitro experiments involving a Y-shaped channel. In this study, we further investigated the effectiveness of the functionalized magnetic force with a realistic 3D vessel through simulations. For the simulations, we considered a more realistic continuous injection of particles with different magnetic forces and frequencies. Based on the results from our simulation studies, we performed in vivo mice experiments to evaluate the effectiveness of using a functionalized magnetic force to aid magnetic nanoparticles (MNPs) in crossing the blood-brain barrier (BBB). To implement the functionalized magnetic force, we developed an electromagnetic actuator regulated by a programmable direct current (DC) power supply. Our results indicate that a functionalized magnetic field can effectively prevent MNPs from sticking, and also guide them across the BBB. We used 770-nm fluorescent carboxyl MNPs in this study. Following intravenous administration of MNPs into mice, we applied an external magnetic field (EMF) to mediate transport of the MNPs across the BBB and into the brain. Furthermore, we evaluated the differential effects of functionalized magnetic fields (0.25, 0.5, and 1 Hz) and constant magnetic fields on the transport of MNPs across the BBB. Our results showed that a functionalized magnetic field is more effective than a constant magnetic field in the transport and uptake of MNPs across the BBB in mice. Specifically, applying a functionalized magnetic field with a 3 A current and 0.5 Hz frequency mediated the greatest transport and uptake of MNPs across the BBB in miceItem Open Access Nonlinear Optimal DTC Design and Stability Analysis for Interior Permanent Magnet Synchronous Motor Drives(2015) Do, Ton Duc; Choi, Han Ho; Jung, Jin-WooThis paper presents a nonlinear optimal direct torque control (DTC) scheme of interior permanent magnet synchronous motors (IPMSMs) based on an offline approximation approach for electric vehicle (EV) applications. First, the DTC problem is reformulated in the stationary reference frame in order to avoid estimating the stator flux angle, which the previous DTC schemes in the rotating stator reference frame require. Thus, the proposed DTC method eliminates the Park’s transformation and consequently it reduces the computational efforts. Particularly, since the estimated stator flux angle is not accurate in low speed range, the proposed method that does not need this information can significantly improve the control performance. Moreover, a nonlinear optimal DTC algorithm is proposed to deal with the nonlinearity of the IPMSM drive system. In this paper, a simple offline θ-D approximation technique is utilized to appropriately determine the controller gains. Via an IPMSM test-bed with a TI TMS320F28335 DSP, the experimental results demonstrate the feasibility of the proposed DTC method by accomplishing better control performances (e.g., more stable in low speed region, much smaller speed and torque ripples, and faster dynamic responses) compared to the conventional proportionalintegral (PI) DTC scheme under various scenarios with the existence of parameter uncertaintiesItem Open Access SDRE-Based Near Optimal Control System Design for PM Synchronous Motor(IEEE, 2011) Do, Ton Duc; Choi, Han Ho; Jung, Jin-WooThis paper presents a nonlinear optimal speed controller based on a state-dependent Riccati equation (SDRE) for permanent magnet synchronous motor (PMSM). An SDREbased near optimal load torque observer is also proposed to provide the load torque information for the controller. In both designs, the stability is analytically proven and Taylor series method is used to find an approximate solution because the SDRE cannot be directly solved. The SDRE-based optimal controller and observer can ensure better control performance such as no overshoot and fast transient response in speed tracking than the linear conventional controllers such as LQ regulator and PI controller even under the variations of the model parameters and load torque. The proposed SDRE-based control strategy is implemented on a PMSM testbed using TMS320F28335 DSP. The simulation and experimental results are given to prove the feasibility of the proposed control schemeItem Open Access θ-D Approximation Technique for Nonlinear Optimal Speed Control Design of Surface-Mounted PMSM Drives(2015) Do, Ton Duc; Choi, Han Ho; Jung, Jin-WooThis paper proposes nonlinear optimal controller and observer schemes based on a θ-D approximation approach for surface-mounted permanent magnet synchronous motors (PMSMs). By applying the θ-D method in both the controller and observer designs, the unsolvable Hamilton–Jacobi–Bellman equations are switched to an algebraic Riccati equation and statedependent Lyapunov equations (SDLEs). Then, through selecting the suitable coefficient matrices, the SDLEs become algebraic, so the complex matrix operation technique, i.e., the Kronecker product applied in the previous papers to solve the SDLEs is eliminated. Moreover, the proposed technique not only solves the problem of controlling the large initial states, but also avoids the excessive online computations. By utilizing a more accurate approximation method, the proposed control system achieves superior control performance (e.g., faster transient response, more robustness under the parameter uncertainties and load torque variations) compared to the state-dependent Riccati equation-based control method and conventional PI controlmethod. The proposed observer-based control methodology is tested with an experimental setup of a PMSM servo drive using a Texas Instruments TMS320F28335 DSP. Finally, the experimental results are shown for proving the effectiveness of the proposed control approach