• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.174-185
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• 2006

This paper describes a DR construction for land navigation and the sigma point based receding horizon Kalman FIR (SPRHKF) filter for DR/GPS hybrid navigation system. A simple DR construction is adopted to improve the performance both of the pure DR navigation and the DR/GSP hybrid navigation system. In order to overcome the flaws of the EKF, the SPKF is merged with the receding horizon strategy. This filter has several advantages over the EKF, the SPKF, and the RHKF filter. The advantages include the robustness to the system model uncertainty, the initial estimation error, temporary unknown bias, and etc. The computational burden is reduced. Especially, the proposed filter works well even in the case of exiting the unmodeled random walk of the inertial sensors, which can be occurred in the MEMS inertial sensors by temperature variation. Therefore, the SPRHKF filter can provide the navigation information with good quality in the DR/GPS hybrid navigation system for land navigation seamlessly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.3-6
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• 2000

The magnetic bearing system are intrinsically unstable, and need the feedback control of electromagnetic forces with measured displacements. So the controller design plays an important role in constructing high performance magnetic bearing system. In case of magnetic bearing system, the order of identified model is high because of unknown dynamics included in closed loop systems - such as sensor dynamics, actuator dynamics - and non-linearity of magnetic bearings itself. In this paper the identification and robust control of flexible rotor supported by magnetic bearing are discussed. We measure and identify overall system that contains not only flexible rotor model but also magnetic bearing and time delay. The structured and unstructured uncertainties are modeled that cover variations of natural frequencies, uncertainties in sensor and actuator gains and unmodeled dynamics. And desired performances are specified with several weighting function. Using augmented system that includes identified model, uncertainties, and weighting functions, μ-synthesis is applied to flexible rotor supported with magnetic bearing. The flexible rotor was spin up over the first flexible critical speed.

• International Journal of Control, Automation, and Systems
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• v.2 no.3
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• pp.374-383
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• 2004

This paper presents a neural network adaptive controller for autonomous diving control of an autonomous underwater vehicle (AUV) using adaptive backstepping method. In general, the dynamics of underwater robotics vehicles (URVs) are highly nonlinear and the hydrodynamic coefficients of vehicles are difficult to be accurately determined a priori because of variations of these coefficients with different operating conditions. In this paper, the smooth unknown dynamics of a vehicle is approximated by a neural network, and the remaining unstructured uncertainties, such as disturbances and unmodeled dynamics, are assumed to be unbounded, although they still satisfy certain growth conditions characterized by 'bounding functions' composed of known functions multiplied by unknown constants. Under certain relaxed assumptions pertaining to the control gain functions, the proposed control scheme can guarantee that all the signals in the closed-loop system satisfy to be uniformly ultimately bounded (UUB). Simulation studies are included to illustrate the effectiveness of the proposed control scheme, and some practical features of the control laws are also discussed.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.52-54
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• 1996

A number of algorithm using the VSS(Variable Structure System) for uncertain dynamic system are developed. But, in these algorithms, the assumption that the uncertainties are bounded and their bounds are available to the designer is involved. And bounds on the uncertainties are an important clue to guarantee the stability of the closed loop system. However, sometimes bounds on the uncertainties may not be easily obtained because of the complexity of the structure of the uncertainties. Therefore, a methodology by which the boundary values on the uncertainties can be easily obtained is required. The VSS proposed in this proposal employ the new adaptive VSS scheme for uncertain dynamic system being estimated on line. The resulting control law is simple and easy to apply to on line computer control. It can also suppress chattering and maintain good tracking precision even if unmodeled dynamics are considered. And, a new method using nonlinear switching surface is introduced so that the speed response is improved and the good transient response can be obtained. Simulation results are presented and show the advantage of the proposed adaptive VSS with nonlinear switching surfaces.

• International Journal of Control, Automation, and Systems
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• v.2 no.1
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• pp.1-14
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• 2004

This paper surveys some existing direct adaptive feedback control schemes for linear time-invariant systems with actuator failures characterized by the failure pattern that some inputs are stuck at some unknown fixed or varying values at unknown time instants, and applications of those schemes to aircraft flight control system models. Controller structures, plant-model matching conditions, and adaptive laws to update controller parameters are investigated for the following cases for continuous-time systems: state tracking using state feed-back, output tracking using state feedback, and output tracking using output feedback. In addition, a discrete-time output tracking design using output feedback is presented. Robustness of this design with respect to unmodeled dynamics and disturbances is addressed using a modified robust adaptive law.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.5
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• pp.76-82
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• 1999

During operating given working a robot manipulator makes some problems such as the accumulation of the error or the deviation from the command trajectory. These problems are mainly due to the disturbance noise or unmodeled system parameters. To solve these problems most of robot manipulators equip the controller. But if exact controller gains are not seleced we can't decrease the working efficiency(such as compensation about error or deviation) of the robot manipulator. So in this paper we present the controller gain tuning law by which we can find the controller gain which satisfies the per-formance specification of the robot manipulator during working of the robot. The proposed algorithm is derived from the Laypunov direct method. And by the simulation on the 4-axis SCARA type robot(SAMSUNG SM5 Robot) we guarantee the performance of this algorithm.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.95-104
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• 1997

We consider controller design problem to enhance shift quality for automatic transmission. A dynamic modeling related to shifting (mainly 2-3 up-shift) is constructed and nonlinear robust controllers are designed to reduce output torque during shifting. Suggesting a new hydraulic circuit enabling the direct clutch drive, the control activity is extended and more implementable than the conventional design. The designed robust controllers overcome the unmodeled dynamics and the uncertainty embending in the system. Moreover, the dynamic effect between the clutch pressure and the PWM valve duty is considered via singular perturbation technique.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.68-75
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• 2000

The flexibility of a manipulator inevitably yields vibration at the end effector. In this work, position and vibration control for a flexible robot arm was studied using a separate voice coil type actuator to raise the accuracy and speed of end tip. A flexible robot arm with a tip mass is modeled as an Euler-Bernoulli beam. An $H_$\infty$$ controller is adapted to get a robust control against unmodeled higher-order mode vibration, output sensor noise, and etc. Simulations and experiments show that the modeling of the system is acceptable and robust vibration control is also achieved.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.651-658
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• 2009

Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters (MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.5
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• pp.177-184
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• 1986

An effective cartesian coordinate model is presented to control a robot motion along a prescribed timebased hand trajectory in cartesian coordinates and to provide an adaptive feedback design approach utilizing self-tuning control methods without requiring a detailed mathematical description of the system dynamics. Assuming that each of the hybrid variable set of velocities and forces at the cartesian coordinate level is mutually independent, the dynamic model for the cartesian coordinate control is reduced to first-order SISO models for each degree of freedom of robot hand, including a term to represent all unmodeled effects, by which the number of parameters to be identified is minimized. The self-tuners are designde to minimize a chosen performance criterion, and the computed control forces are resolved into applied joint torques by the Jacobian matrix. The robustness of the model and controller is demonstrated by comparing with the other catesian coordinate controllers.