• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.10a
• /
• pp.293-298
• /
• 1993

In ground vehicles, the increasing demand for safety and ride comfort which are trade-off relation, especially at high speeds, has led to the development od actively controlled suspensions. The LQG/LTR controller can be used to design a robust feedback control system that deals with disturbance rejection properties as well as insensitivity to modelling errors and sensor noise. And when the disturbance can not be measured but is limited within a certain frequency range, a bandpass feedback to eliminate the disturbance response can be used. In this paper, hybrid controller cosisted of bandpass feedback controller and LQG/LTR controller is applied to a quarter-car model moving on a randomly profiled road. The random road profile considered as colored noise is shaped from white noise by use of shaping filter. The performance of the hybrid control system is compared with that of an LQG/LTR controlled system.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.1
• /
• pp.76-85
• /
• 2008

Motivated by the fact that in many industrial robots the joint velocity is estimated from position measurements, the trajectory tracking of robot manipulators with output feedback is addressed in this paper. The fact that robot actuators have limited power is also taken into account. Let us notice that few solutions for the torque-bounded output feedback tracking control problem have been proposed. In this paper we contribute to this subject by presenting a theoretical reexamination of a known controller, by using the theory of singularly perturbed systems. Motivated by this analysis, a redesign of that controller is introduced. As another contribution, we present an experimental evaluation in a two degrees-of-freedom revolute-joint direct-drive robot, confirming the practical feasibility of the proposed approach.

• Journal of KSNVE
• /
• v.4 no.4
• /
• pp.497-505
• /
• 1994

This paper presents a design scheme of the active noise absorber that consists of the feedforward and feedback controller. The feedback controller aims to increase damping for the specific acoustic mode. The feedforward controller synthesizes the input signal coherent with the primary noise source in order to attenuate the noise field in the broad frequency range. The feedforward controller is adapted to the variation of acoustic plants using the proposed algorithm which compensates the effect of feedback link. Experimental results demonstrate that the proposed method is effective for the active control of band-limited noise fields in the enclosure.

• Journal of Auto-vehicle Safety Association
• /
• v.15 no.3
• /
• pp.17-26
• /
• 2023

This paper presents extended state feedback control based on impulse response for lane change of autonomous driving vehicle. The triple characteristic root of path tracking system and longitudinal velocity determine feedback gains. We suggest a resemblance of impulse response curve of the system and lane change trajectory of the vehicle. The root affects the duration of lane change and lateral acceleration. The effect of limited lateral acceleration and saturation of steering angle will be analyzed and discussed. Finally, simulation results will show the trajectory of lane change based on impulse response under limitation of lateral acceleration.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.4
• /
• pp.1292-1306
• /
• 2014

This paper proposes a space-polarization division multiple access (SPDMA) system that has limited feedback channels. The system simultaneously serves data streams to multiple mobile users through dual-polarized antenna arrays, by using pre-determined sets of precoding vectors that are orthogonal in both space and polarization domains. To this end, a codebook whose elements are sets of the precoding vectors is systematically designed based on the discrete Fourier transform (DFT) matrix and considering the power imbalance of polarized channels. Throughput of the SPDMA system is evaluated and compared to that of space division multiple access (SDMA) system, according to the various parameters including cross polarization discrimination (XPD). The results show that the throughput of SPDMA system outperforms that of SDMA in the environments of high XPD with many mobile users.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.11
• /
• pp.1082-1088
• /
• 2004

This paer presents a feedback-controlled, MEMS-fabricated microaccelerometer($\mu$XL). The $\mu$XL has received much commercial attraction, but its performance is generally limited. To improve the open-loop performance, a feedback controller is designed and experimentally evaluated. The feedback controller is applied to the x/y-axis $\mu$XL fabricated by sacrificial bulk micromachining(SBM) process. Even though the resolution of the closed-loop system is slightly worse than open-loop system, the bandwidth, linearity, and bias stability are stability are significantly improved. The noise equivalent resolution of open-loop system is 0.615 mg and that of closed-loop system is 0.864 mg. The bandwidths of open-loop and closed-loop system are over 100Hz. The input range, non-linearity and bias stability are improved from $\pm10\;g\;to\;\pm18g$, from 11.1%FSO to 0.86%FSO, and from 0.221 mg to 0.128 mg by feedback control, respectively.

• The Journal of Korea Robotics Society
• /
• v.17 no.3
• /
• pp.264-272
• /
• 2022

Human-robot cooperative tasks are increasingly required in our daily life with the development of robotics and artificial intelligence technology. Interactive reinforcement learning strategies suggest that robots learn task by receiving feedback from an experienced human trainer during a training process. However, most of the previous studies on Interactive reinforcement learning have required an extra feedback input device such as a mouse or keyboard in addition to robot itself, and the scenario where a robot can interactively learn a task with human have been also limited to virtual environment. To solve these limitations, this paper studies training strategies of robot that learn table balancing tasks interactively using deep reinforcement learning with human's facial expression feedback. In the proposed system, the robot learns a cooperative table balancing task using Deep Q-Network (DQN), which is a deep reinforcement learning technique, with human facial emotion expression feedback. As a result of the experiment, the proposed system achieved a high optimal policy convergence rate of up to 83.3% in training and successful assumption rate of up to 91.6% in testing, showing improved performance compared to the model without human facial expression feedback.

• Journal of Broadcast Engineering
• /
• v.12 no.5
• /
• pp.516-524
• /
• 2007

In order to use limited frequency resources efficiently, a single frequency network using digital on-channel repeater(DOCR) has been studied and would be implemented. The DOCR generates strong pre-ghosts to ATSC DTV receivers. The forward filter of equalizer in ATSC DTV receivers compensates the distortion made by pre-ghosts. This process induces noise enhancement and colored noise, thereby results in the performance degradation. In this paper we propose to use a dual-feedback equalizer to combat strong pre-ghosts. The proposed equalizer has two feedback filters. One is the decision feedback filter and the other is non-decision feedback filter. The additional non-decision feedback filter decreases the noise by whitening the noise and preventing the generation of colored noise in pre-ghost channel. Thus the equalization technique of dual-feedback structure has performance enhancement in pre-ghost channel in comparison with conventional decision feedback equalizer(DFE). By simulation we analyzed the performance enhancements of DTV receiver using dual-feedback equalization structure.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.2
• /
• pp.25-33
• /
• 2010

Introducing the quantized channel state information (CSI), space division multiple access (SDMA) can extract the multiplexing gain with the limited feedback burden. However, huge signaling burden of feedback can still suffer SDMA system because the total feedback data of SDMA is linearly dependent on the number of users. Hence, we propose a new feedback scheme to control the feedback load decided by the number of users. In this scheme, the cut-off level, which restricts the feedbacks of poor conditioned users, is suggested for the reduction of the feedback burden without the performance loss. From simulation results, then, we show that the proposed feedback scheme can achieve not only the sum-rate gain but also the reasonable feedback reduction.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.3A
• /
• pp.327-334
• /
• 2008

Conventional on-channel-repeaters (OCRs) have a crucial problem that the power of a re-transmitted signal is highly limited by a feedback signal due to antenna coupling. The power limitation problem in OCRs has been solved by incorporating a demodulation-type feedback canceller which eliminates unwanted feedback signals by estimating a feedback channel. In applying the demodulation-type feedback canceller to T-DMB repeaters, there is a troublesome problem of unfrequent known pilot symbols, resulting in poor convergence performance of channel estimation. To solve this problem and enhance the accuracy of estimation, we propose a partitioning method of the Phase Reference Symbol (PRS) transformed in time domain. Since filter coefficients are updated every one partitioned subgroup, the number of updates is increased by the number of partitioned subgroups and thus the convergence speed is enhanced. The improved performance of feedback-channel estimation is directly connected with the feedback-cancellation performance. Simulation result shows that the feedback canceller incorporating the proposed partitioning method has a good performance in terms of residual feedback power.