• The Journal of Korea Robotics Society
• /
• v.6 no.4
• /
• pp.317-322
• /
• 2011

An augmented state feedback controller for a Wheeled Inverted Pendulum (WIP) is proposed in this research. The augmented state feedback controller is able to keep the WIP returning to the origin. Generally, the WIP has both stable and unstable equilibrium points. To keep the WIP over the unstable equilibrium point, the WIP consistently is being controlled. A simple state feedback controller is letting the WIP out of the origin when the center of gravity of the WIP locates out of the schematic center line. In some case of applications, it may not be desirable that the WIP is drifting out of the initial location. The proposed augmented state feedback controller is able to keep the WIP at the initial location whether its center of gravity lies out of the center line or not. Numerical simulations are carried out to show the validation of the augmented sated feedback controller.

• English Language & Literature Teaching
• /
• v.16 no.1
• /
• pp.171-188
• /
• 2009

The purpose of this study was to investigate the role of ongoing feedback from the professor in students' processes of learning and developing writing skills. Specifically, the researcher was concerned with how ongoing feedback affected students' attitudes towards writing because in EFL contexts, motivating students to write is a first step to engage them in a challenging journey of academic writing. 20 freshmen taking a writing course, "Paragraph & Essay Writing", at A university participated in this study and they were asked to complete the questionnaire at the end of the spring semester 2009. The results revealed that receiving ongoing feedback from the professor had a positive influence on affective domain, was helpful to develop learning strategies, and was valuable in learning outcomes. However, they also expressed negative opinions: feeling a burden, focusing on forms, and feeling confused. To reflect their opinions, the following four suggestions were made to create a more effective learning environment: promoting learner autonomy, facilitating individual writing conferences, giving balanced feedback in between form and content, and using judicious feedback through careful streaming.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.12
• /
• pp.1256-1263
• /
• 2004

Output feedback passivation problem is studied when the given system is not minimum-phase or does not have relative degree one. Using a parallel connection with an additional dynamics, the authors provide a dynamic output feedback control law which renders the composite system passive. Sufficient conditions are presented under which the composite system is output feedback passive. As an application of the dynamic passivation scheme, a point-to-point control law for a flexible joint robot is presented when only the position measurements are available. This provides an alternative way of replacing the role of the velocity measurements for the proportional-derivative (PD) feedback law. The performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1981-1986
• /
• 2004

In this study, the basic motor control system had been investigated. The controller for this study consists of two main parts, a feedforward controller part and a feedback controller part. Each part will deals with different control problems. The feedback controller deals with robustness and stability, while the feedforward controller deals with response speed. The feedforward controller, used to solve the tracking control problem, is adaptable. To make such a tracking perfect, an adaptive law based on Feedback Error Learning (FEL) is designed so that the feedforward controller becomes an inverse system of the controlled plant. The novelty of FEL method lies in its use of feedback error as a teaching signal for learning the inverse model. The theory in $H^{\infty}$-Control is selected to be applied in the feedback part to guarantee the stability and solve the robust stabilization problems. The simulation of each individual part and the integrated one are taken to clarify the study.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.898-902
• /
• 2003

For linear descriptor systems, we consider the $H_{INFTY}$ controller design problem via output feedback. Both static output feedback and dynamic one are discussed. First, in the case of static output feedback, we reduce our control problem to solving a bilinear matrix inequality (BMI) with respect to the controller coefficient matrix, a Lyapunov matrix and a matrix related to the descriptor matrix. Under a matching condition between the descriptor matrix and the measured output matrix (or the control input matrix), we propose setting the Lyapunov matrix in the BMI as being block diagonal appropriately so that the BMI is reduced to LMIs. For fixed-order dynamic $H_{INFTY}$ output feedback, we formulate the control problem equivalently as the one of static output feedback design, and thus the same approach can be applied.

• Journal of Educational Research in Mathematics
• /
• v.12 no.3
• /
• pp.313-329
• /
• 2002

The importance of professor's outline in a feedback instruction was examined through various documents and the way in which the evaluation was fulfilled in Korean educational environment and its reflection upon the evaluation result were investigated by means of research. Based upon the survey results in connection with the progress and basis of teachers' on the spot feedback mathematics instruction in schools, it was found that most of teachers who engaged in feedback mathematics instruction were going over the most frequently missed problems. I proposed that we should bring up the point at issue and grasp its tendency of a class and entire group's results by means of a relative comparative analysis method, and thereupon establish a fixed category and choose substantial feedback scholarship according to that category. From this basis, the sub-sequent research topics include the substantial feedback effects of the selected problems that should be given priority, a group analysed and classified by means of comparison of tendency as well as feedback outline depended on students' characteristic, and the determining factors of tendency(a condition of professors, a level of students, geographical difference(s), and gender difference(s), etc...).

• Journal of Korean Institute of Industrial Engineers
• /
• v.27 no.1
• /
• pp.11-17
• /
• 2001

We consider the M/G/1 with Bernoulli feedback, where the served customers wait in the feedback queue for rework with probability p. It is important to decide the moment of dispatching in feedback systems because of the dispatching cost for rework. Up to date, researches have analyzed for the instantaneous-dispatching model or the case that dispatching epoch is determined by the state of feedback queue. In this paper we deal with a dispatching model whose dispatching epoch depends on main queue. We adopt supplementary variable method for our model and a numerical example is given for clarity.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.38 no.1
• /
• pp.29-44
• /
• 2013

This study suggests that as receiving feedback is moved back, the effectiveness of problem-solving increases. Utilizing data from innovation contests in which a number of problem solvers compete with each other, we answer questions such as whether the order of receiving first feedback affects problem-solving effectiveness and how problem-solving experience moderates the relationship between the first feedback order and problem-solving effectiveness. Empirical results based on data collected from Kaggle, an online platform for innovation contests, showed that the order that contest participants receive the first feedback increases problem-solving effectiveness. Furthermore, the more prior experience of contest participants accentuates the suggested relationship between the order of receiving the first feedback and problem-solving effectiveness.

• Earthquakes and Structures
• /
• v.6 no.2
• /
• pp.217-235
• /
• 2014

In this paper, different feedback control strategies are presented for active seismic control using proportional-integral-derivative (PID) type controllers. The parameters of PID controller are found by using an numerical algorithm considering time delay, maximum allowed control force and time domain analyses of shear buildings under different earthquake excitations. The numerical algorithm scans combinations of different controller parameters such as proportional gain ($K_p$), integral time ($T_i$) and derivative time ($T_d$) in order to minimize a defined response of the structure. The controllers for displacement, velocity and acceleration feedback control strategies are tuned for structures with active control at the first story and all stories. The performance and robustness of different feedback controls on time and frequency responses of structures are evaluated. All feedback controls are generally robust for the changing properties of the structure, but acceleration feedback control is the best one for efficiency and stability of control system.

• English Language & Literature Teaching
• /
• v.15 no.3
• /
• pp.83-104
• /
• 2009

This study examined whether self-correction or metalinguistic explanation might make a difference in the ability to accurately write two English grammatical structures when learners received indirect teacher feedback in the form of underlining target errors in a Korean EFL college classroom. With the goal of helping low-proficiency students improve their ability to accurately write sentences including nonfinite present participial relative clauses and present participial constructions, four groups were formed: a group which received indirect feedback, a group which received indirect feedback and metalinguistic explanation, a group which received indirect feedback and self-corrected errors, and a group which received indirect feedback and self-corrected errors after receiving metalinguistic explanation. The results showed that the effects of either metalinguistic explanation or self-correction integrated with indirect feedback on learners' ability to accurately write the target structures were not meaningful, while the combined effects of metalinguistic explanation and self-correction were statistically significant.