Design of an Enhanced Target Tracking Strategy for the Human-Following Mobile Robot by Using Dual Ultra-Wideband Anchors = 듀얼 초광대역 앵커를 사용한 인간 추종 모바일 로봇을 위한 향상된 목표 추적 전략 설계

다국어 초록 (Multilingual Abstract)

Mobile robots, equipped with target localization and tracking functions, facilitate everyday tasks by assisting with item transportation or offering companion services. It is a challenging issue to identify, localize and track the target more accurately and quickly at a low cost. This study presents a novel approach for target localization and tracking in human-following mobile robots by using dual ultra-wideband (UWB) anchors. The accuracy of UWB sensors is enhanced through Kalman filtering and distance calibration, thus significantly reducing measurement errors. The proposed target tracking strategy integrates these sensors with a Mecanum wheeled mobile platform, optimizing motion control and target tracking. Based on the developed dual UWB anchors' geometric localization model, the horizontal relative distance and orientation between the target and the robot were estimated. In tracking scenarios, the robot demonstrates advanced adaptability: While the target at close-range, the robot rotates in place for orientation tracking to directly face the target, and the designed tracking algorithm allows the robot to dynamically adjust its rotation speed, resulting in smooth tracking movements. While the target at longer-range, the robot dynamically modifies its tracking speed and orientation according to relative positional data, to ensure effective and continuous target following. Through experimental validation, the average accuracy of the recognized error angles in orientation tracking reached 89.8%, and in long-distance tracking, the robot could always face the target and kept a distance from the target for tracking, in which the median lateral error of linear trajectory tracking was 0.03 m. Compared with the existing related studies, the tracking accuracy was improved by 50% and the tracking effect was more smooth.

국문 초록 (Abstract)

목표 위치 파악 및 추적 기능을 갖춘 모바일 로봇은 물품 운반 보조 및 작업자 동반 서비스 제공을 통해 일상적인 작업을 돕는다. 낮은 비용으로 더 정확하고 빠르게 목표위치를 식별하고 추적하는 것은 어려운 문제이다. 본 논문은 듀얼 초광대역 앵커를 사용하여 모바일 로봇에서의 인간 추적을 위한 목표물 위치 파악 및 추적에 대한 새로운 방법을 제시한다. 칼만 필터와 거리 보정을 통해 UWB 센서의 정확성을 향상시켜 측정 오류를 크게 줄일 수 있다. 제안된 목표물 추적 전략은 이 센서들을 메카넘 휠 모바일 플랫폼과 통합하여 동작 제어와 목표물 추적을 최적화한다. 개발된 듀얼 UWB 앵커의 기하학적 위치 파악 모델을 기반으로, 목표물과 로봇 사이의 수평 상대 거리와 방향이 추정된다. 추적 시나리오에서, 로봇은 고급 적응성을 보여준다: 목표물이 근거리에 있을 때, 로봇은 방향 추적을 위해 자리에서 회전하여 목표물을 직접 마주보고, 설계된 추적 알고리즘은 로봇이 회전 속도를 동적으로 조정할 수 있게 하여 부드러운 추적 움직임을 가능하게 한다. 장거리에서는 상대 위치 정보를 기반으로 추적 속도와 자세를 동적으로 조정하여 효과적이고 지속적으로 따라갈 수 있도록 한다. 실험적 검증을 통해 방향 추적에서 인식된 오류 각의 평균 정확도는 89.8%에 달했으며, 장거리 추적에서는 로봇이 항상 목표물을 마주보고 목표물과의 거리를 유지하면서 추적했으며, 선형 궤적 추적의 가로 오차의 중앙값은 0.03 m 였다. 기존 관련 연구와 비교했을 때, 추적 정확도는 50% 향상되었고 추적 효과는 더욱 안정적이었다.

목차 (Table of Contents)

• List of Figures iii
• List of Tables v
• List of Algorithms vi
• Abstract vii
• 1 Introduction 1
• 1.1 Research Background 1
• 1.2 Contributions 5
• 1.3 Outline 9
• 2 Human-Following Mobile Robot System 11
• 2.1 Framework of the Human-Following Mobile Robot System 11
• 2.2 Hardware Design of the Human-Following Mobile Robot System 14
• 2.3 Mecanum Wheeled Mobile Platform Control 18
• 2.3.1 Inverse Kinematics Analysis of the Mecanum Wheeled Mobile Platform 19
• 2.3.2 Realization of the Mobile Platform’s Desired Motion by Motor Control 22
• 2.3.3 Forward Kinematics Analysis of the Mecanum Wheeled Mobile Platform 25
• 3 Enhanced Target Tracking Strategy by Using Dual Ultra-Wideband Anchors 27
• 3.1 Target Localization Model Based on Dual UWB Anchors 27
• 3.1.1 Wireless Ranging Principle of the UWB Sensors 27
• 3.1.2 First-Order Kalman Filter-Based Ranging Optimization of the UWB Sensors 32
• 3.1.3 Measurement Error Calibration for the UWB Sensors 34
• 3.1.4 Target Localization Model Based on Mobile Robot’s Coordinate System 37
• 3.2 Enhanced Target Tracking Strategy for the Human-Following Mobile Robot 43
• 3.2.1 Mobile Robot’s Orientation Tracking Control for the Target in Close-Range Situations 45
• 3.2.2 Mobile Robot’s Position Tracking Control for the Target in Long-Range Situations 51
• 3.2.3 Handling of Emergency Situations: Obstacle Avoidance and Speed Limit 54
• 4 Experiments and Evaluations 57
• 4.1 Experimental Setup 57
• 4.2 Experiments and Results 62
• 4.2.1 Orientation Tracking Experiment 62
• 4.2.2 Long-Range Tracking Experiment (Room Environment) 65
• 4.2.3 Long-Range Tracking Experiment (Corridor Environment) 68
• 4.3 Evaluations 72
• 5 Discussion and Conclusion 74
• 5.1 Discussion 74
• 5.1.1 Accuracy of Different Wireless Ranging Methods 74
• 5.1.2 Human-Following Mobile Robots with Different Numbers of UWB Anchors 77
• 5.1.3 Tracking Performance of Different Methods 79
• 5.2 Conclusion 82
• References 85
• Appendix A 92
• Appendix B 93
• 국문요지 94
• Acknowledgments 95

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