Model Updating Using the Closed-loop Natural Frequency

Parameter modification of a linear finite element model(FEM) based on modal sensitivity matrix is usually performed through an effort to match FEM modal data to experimental ones. However, there are cases where this method cant be applied successfully; lack of reliable modal data and ill-conditioning of the modal sensitivity matrix constitute such cases. In this research, a novel concept of introducing feedback loops to the conventional modal test setup is proposed. This method uses closed-loop natural frequency data for parameter modification to overcome the problems associated with the conventional method based on modal sensitivity matrix. We proposed the whole procedure of parameter modification using the closed-loop natural frequency data including the modal sensitivity modification and controller design method. Proposed controller design method is efficient in changing modes. Numerical simulation of parameter estimation based on time-domain input/output data is provided to demonstrate the estimation performance of the proposed method

A Study on the Controller Design of traction Control System

Excessive traction torque while starting on slippery roads and slopes causes the wheels to spin, consequently reducing the directional stability and the traction force. It may be a difficult task for normal dirvers to steer under these conditions. To solve this problem, researches on the traction control system (TCS) that controls the traction torque using various vehicle parts have been conducted. But these commercial TCSs use experimental methods such as lookup table and gain-scheduling to achieve proper performance under various road and vehicle conditions. This paper propopses a novel brake torque controller, which is insensitive to the variation of vehicle mass, brake gain and road conditions, and throttle angle controller using multiple sliding mode based on the engine model. Through the hybrid use of two controllers, the suggested controller could gain traction force and directional stability

System identification using the feedback loop

Identification of systems operating in closed loop has long been of prime interest in industrial applications. The fundamental problem with closed-loop data is the correlation between the unmeasurable noise and the input. This is the reason why several methods that work in open loop fail when applied to closed-loop data. The prediction error based approaches to the closed-loop system are divided to direct method and indirect method. Both of direct and indirect methods are known to be applied to the closed-loop data without critical modification. But the direct method induces the bias error in the experimental frequency response function and this bias error may deteriorates the parameter estimation performanc

Model updating using the feedback exciter : the decision of sensor location & feedback gain

The updating of FE model to match it with the experimental results needs the modal information. There are two cases where this methodology is ill-equip to deal with； under-determined and ill-conditioning problem. The feedback exciter that uses the summation of the white noise and the signals from the measurement sensors multiplied with feedback gains can deal with these problems as the new modal data from the closed loop system generate more constraints the updating parameters should obey. The new modal data from the closed loop system should be different to enhance the condition of the modal sensitivity matrix. In this research, a guide for the selection of the sensor locations and the decision of the corresponding output feedback gains is proposed. This method is based on the sensitivity of the modal data with respect to the feedback gains. Through the proper selection of the exciter and sensor locations and the feedback gain, the eigenvalue sensitivity of the updating parameters which cause the ill-conditioning of the modal sensitivity matrix can be modified and consequently the error contamination in updating parameters are reduced

Mode-decoupling controller for feedback model updating

A novel concept of feedback loop design for modal test and model updating is proposed. This method uses the closed -loop natural frequency information for parameter modification to overcome the problems associated with the conventional method employing the modal sensitivity matrix. To obtain new modal information from closed-loop system, controllers should be effective in changing modal data while guaranteeing the stability of closed-loop system. It is very hard to guarantee the stability of the closed-loop system with non-collocated sensor and actuator set. Ill this research, we proposed a controller called mode-decoupling controller that can change a target mode as much as the designer wants guaranteeing the stability of closed-loop system. This controller can be computed just using measured open-loop modeshape matrix. A simulation based on time domain input/output data is performed to check the feasibility of proposed control method

Feedback Model Updating: Application to Indeterminate Structure

The parameter modification of the initial FEM model to match it with the experimental results needs the modal information and the modal sensitivity matrix to the parameter change. There are two cases this methodology is ill-equip to deal with; the deficiency of the necessary modal information and the ill-conditioning of the sensitivity matrix. In this research, a novel concept of the feedback exciter that uses the summation of the white noise and the signals from the measurement sensors multiplied with feedback gains as the reference signal is proposed. There are 2 advantages using this external feedback excitation. First, we can use the change of the system response such as modal data by the active energy Path from the sensor to the exciter. This change of the system response can be additional clues to the system dynamics that we want to know. Secondly, the external energy Path alternates the offset of the Parameter change to the system response. That means the modal sensitivity of the parameters becomes different from the original sensitivities by the feedback excitation. Through the feedback loop, we can change the similar modal sensitivities of some updating parameters and consequently discriminate the parameters using the closed-loop modal data. To demonstrate the discrimination performance, the parameter estimation of an indeterminate structure by use of the feedback method is introduced

A study on the controller design of traction control system

학위논문(석사) - 한국과학기술원 : 기계공학전공, 2000.2, [ vi, 92 p. ]한국과학기술원 : 기계공학전공

매개 변수 추정을 위한 폐루프 제어 기반 시스템 변경법

학위논문(박사) - 한국과학기술원 : 기계공학전공, 2004.8, [ ix, 127 p. ]We deal with the multiple modal analysis that perturb the original system variously and use the modal data set of perturbed systems in applications such as parameter estimation or damage detection. Though many approaches about multiple modal analysis have been proposed, no systematic experiment guideline for modification is proposed. For this reason, the first research objective is the systematic development of system perturbation method. Among various approaches like point mass addition, boundary condition change or feed-back control, closed-loop control based perturbation is selected as the basic perturbation tool for its easiness and accuracy in experimental setup and ability of diverse perturbations. Plenty of sensors are assumed available and distributed over the system and a few actuators such as electro-magnetic exciter are assumed available as usually done in the conventional modal test. And static output feedback control scheme is chosen for simplicity. For the selected configuration of transducer and controller type, decision on the actuator``s and sensor``s locations and feedback gain is considered for systematic system perturbation. A criterion for the decision of actuator location based on control power requirement is proposed. For the chosen actuator locations, the feedback gain is obtained minimizing a performance index of a weighted modal power of each mode with the fulfillment of pre-defined modal change of the target mode. As sensors are distributed over the system and exciters are located in a selected few locations, this configuration results in non-collocated sensor and actuator case where diverse changes of system are possible but the instability problem of closed-loop system prevents its actual usage. The stability of closed-loop system can be guaranteed by adjusting the weighting to each mode on-line during the modal testing. However, the modification of feedback gain vector during the experiment is a little cumbersome. Therefore, it is ...한국과학기술원 : 기계공학전공

Fault diagnosis far vehicles with drive-by-wire systems using Kalman falter

Drive-by-wire systems will become popular in the near future, because of their compactness, lightweight and improved controllability. Since there would be no mechanical redundancy in the drive by wire subsystem, the reliability of the system needs to be improved by using fault diagnosis of sensors and actuators. In the paper, a Kalman filter based fault diagnosis method for the vehicle with the drive by wire system which includes steer by wire, brake by wire and throttle by wire systems, is proposed. It is shown that the proposed method is successful in fault detection and isolation for single sensor/actuator fault of the vehicle syste