Author name cluster

Kiyoung Choi

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4 papers

2 author rows

ICRA Conference 2025 Conference Paper

Robust Orientation Control of Robot Manipulator Using Orientation Disturbance Observer

Kiyoung Choi
Junho Song
Wonbum Yun
Sehoon Oh

This paper presents a robust control algorithm for precise orientation control of robot manipulators using a disturbance observer (DOB) specifically designed for orientation dynamics. Our approach addresses the challenges of 3D orientation control by incorporating various orientation representations, such as Euler angles, quaternions, and exponential coordinates, and analyzing their impact on DOB performance. Through theoretical analysis and experimental validation, we demonstrate the effectiveness of our method in achieving high-precision orientation control under uncertainties and disturbances. This work offers a comprehensive framework for robust orientation control, advancing the application of DOB in complex robotic tasks.

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IROS Conference 2024 Conference Paper

Identification of Flexible Joint Robot Inertia Matrix Using Frequency Response Analysis

Kiyoung Choi
Junho Song
Wonbum Yun
Deokjin Lee
Sehoon Oh

This paper presents a novel, nonlinearity robust identification method for deriving the inertia matrix of multi-DOF Flexible Joint Robots (FJR), utilizing resonance and anti-resonance frequencies in the Frequency Response Functions (FRF). Our proposed method overcomes the limitations of conventional approaches, which are susceptible to mechanical nonlinearities, leading to inaccurate models. By leveraging frequency domain techniques, our approach effectively mitigates the influence of nonlinear characteristics, providing a more accurate and reliable means of robot control. Furturmore, the paper highlights the benefits of frequency domain system identification, including nonlinear robustness and the ability to decompose the flexible joint into motor and load components. Finally, a novel sequential excitation algorithm is proposed to obtain the inertia matrix of a multi-DOF robot manipulator without relying on complex theories or optimizations. The effectiveness of the proposed algorithm is verified through simulation and experiment.

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AAAI Conference 2019 Conference Paper

Network Recasting: A Universal Method for Network Architecture Transformation

Joonsang Yu
Sungbum Kang
Kiyoung Choi

This paper proposes network recasting as a general method for network architecture transformation. The primary goal of this method is to accelerate the inference process through the transformation, but there can be many other practical applications. The method is based on block-wise recasting; it recasts each source block in a pre-trained teacher network to a target block in a student network. For the recasting, a target block is trained such that its output activation approximates that of the source block. Such a block-by-block recasting in a sequential manner transforms the network architecture while preserving the accuracy. This method can be used to transform an arbitrary teacher network type to an arbitrary student network type. It can even generate a mixed-architecture network that consists of two or more types of block. The network recasting can generate a network with fewer parameters and/or activations, which reduce the inference time significantly. Naturally, it can be used for network compression by recasting a trained network into a smaller network of the same type. Our experiments show that it outperforms previous compression approaches in terms of actual speedup on a GPU.

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ICRA Conference 2004 Conference Paper

A Mobility Analysis Method of Closed-chain Mechanisms with Over-constraints and Non-holonomic Constraints

Whee Kuk Kim
Kiyoung Choi
Byung-Ju Yi

Mobility for a great portion of robot mechanisms having over-constraint and non-holonomic constraints has not been clearly identified. This work us to introduce a method of mobility analysis for such systems using the concept of representative screws and pseudo-joint. The pseudo-joint is employed to effectively represent the real motion trajectory due to the rolling contact of the wheel. To show the validity and effectiveness of the proposed method, mobility of various types of planar mobile robots having over-constraint and non-holonomic constrains are examined.

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