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서진호(Jin-Ho Suh),Tring Hieu Bui,Tan Tien Nguyen,김상봉(Sang-Bong Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
This paper proposes an adaptive control algorithm for nonholonomic mobile robots with unknown<br/> parameters and the proposed control method is used in numerical simulations for applying to a practical twowheeled<br/> welding mobile robot(WMR). The proposed adaptive controller to track an arbitrary given welding<br/> path is designed by using back-stepping technique and is derived for a nonlinear model under the assumption<br/> such that the system parameters are partially known. Moreover, the proposed adaptive control system is stable<br/> in the sense of Lyapunov stability. Inertia moments of system are considered to be unknown parameters and<br/> their values can be estimated simply by using update laws proposed in an adaptive control scheme of this<br/> research. The simulation results are provided to show the effectiveness of the accurate tracking capability of<br/> the proposed controller for two-wheeled welding mobile robot with a smooth curved reference welding path.
Trong Hieu Bui,Jin Ho Suh,Sang Bong Kim,Tan Tien Nguyen 대한기계학회 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.12
This paper presents hybrid control of an active suspension system with a full-car model by using H_∞ and nonlinear adaptive control methods. The full-car model has seven degrees of freedom including heaving, pitching and rolling motions. In the active suspension system, the controller shows good performance: small gains from the road disturbances to the heaving, pitching and rolling accelerations of the car body. Also the controlled system must be robust to system parameter variations. As the control method, H∞ controller is designed so as to guarantee the robustness of a closed-loop system in the presence of uncertainties and disturbances. The system parameter variations are taken into account by multiplicative uncertainty model and the system robustness is guaranteed by small gain theorem. The active system with H∞ controller can reduce the accelerations of the car body in the heaving, pitching and rolling directions. The nonlinearity of a hydraulic actuator is handled by nonlinear adaptive control based on the back -stepping method. The effectiveness of the controllers is verified through simulation results in both frequency and time domains.
Bui, Trong-Hieu,Suh, Jin-Ho,Kim, Sang-Bong,Nguyen, Tan-Tien The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.12
This paper presents hybrid control of an active suspension system with a full-car model by using H$\sub$$\infty$/ and nonlinear adaptive control methods. The full-car model has seven degrees of freedom including heaving, pitching and rolling motions. In the active suspension system, the controller shows good performance: small gains from the road disturbances to the heaving, pitching and rolling accelerations of the car body. Also the controlled system must be robust to system parameter variations. As the control method, H$\sub$$\infty$/ controller is designed so as to guarantee the robustness of a closed-loop system in the presence of uncertainties and disturbances. The system parameter variations are taken into account by multiplicative uncertainty model and the system robustness is guaranteed by small gain theorem. The active system with H$\sub$$\infty$/ controller can reduce the accelerations of the car body in the heaving, pitching and rolling directions. The nonlinearity of a hydraulic actuator is handled by nonlinear adaptive control based on the back-stepping method. The effectiveness of the controllers is verified through simulation results in both frequency and time domains.
Han Audrey Xinyun,Tan Tien Jin,Nguyen Tiep,Lee Dave Yee Han 대한슬관절학회 2020 대한슬관절학회지 Vol.32 No.-
We aimed to identify the anterolateral ligament (ALL) tears in anterior cruciate ligament (ACL)-deficient knees using standard 1.5-Tesla magnetic resonance imaging (MRI). We included all patients who underwent primary ACL reconstruction at our center between 2012 and 2015. Exclusion criteria included patients with multiple ligament injuries, lateral collateral ligament, posterolateral corner, and infections, and patients who underwent MRI more than 2 months after their injury. All patients ( n = 148) had ACL tears that were subsequently arthroscopically reconstructed. The magnetic resonance (MR) images of the injured knees performed within 2 months of injury were reviewed by a musculoskeletal radiologist and an orthopedic surgeon. The patients were divided into two groups. The first group of patients had MRI performed within 1 month of injury. The second group of patients had MRI performed 1–2 months after the index injury. Both assessors were blinded and the MR mages were read separately to assess the presence of ALL, presence of a tear and the location of the tear. Based on their readings, interobserver agreement (kappa statistic (K)), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were compared. The ALL was identified in 100% of the patients. However, there was a discrepancy of up to 15% in the identification of tear of the ALL. In the first group in which MRI scans were performed within 1 month of injury, the ALL tear was identified by the radiologist in 92% of patients and by the surgeon in 90% of patients (Κ = 0.86). In the second group in which MRI scans were performed within 1–2 months of the injury, the ALL tear was identified by the radiologist in 78% of patients and by the surgeon in 93% of patients (K = 0.62).The ALL can be accurately identified on MRI, but the presence and location of ALL tear and its location cannot be reliably identified on MRI. The accuracy in identification and characterization of a tear was affected by the interval between the time of injury and the time when the MRI was performed.Diagnostic, level IIIb, retrospective.