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Nabih Pico,Eui-Chan Kim,Sang-Hyeon Park,Meseret Abayebas Tadese,Huy Nguyen Tran,Beomjoon Lee,Hyungpil Moon 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
Wheeled robots are involved in different applications due to their adaptability to different terrains. The stability of the robot is related to the permanent contact of the wheels with the ground. This paper presents the method to recognize the geometry terrains in real-time when the wheel has contact at one or multiple contact points with the soil by using laser scanning sensors and measuring the contact angle between the wheel-ground. Furthermore, the robot can recognize when its wheel loses contact with the terrain. Thus, we can create a proper robot control by obtaining the Jacobian matrix and its inverse related to the terrain information. In consequence, the robot can overcome diverse terrains and move safely. The method is validated in experimental results when the six-wheeled robot recognizes a rocky terrain and a slope with a step.
Nabih Pico,Hong-ryul Jung,Juan Medrano,Meseret Abayebas,Dong Yeop Kim,황정훈,Hyungpil Moon 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2
The objective of this work is to control a delivery robot equipped with a passive bogie that can successfully climb up steps of various sizes and move on uneven terrain in outdoor environments. The kinematic model of a six-wheel mobile robot is described in detail. Jacobian matrices and inverse kinematics are obtained to get the velocity of each wheel based on the desired velocity of the robot center of mass in conjunction with the terrain information obtained by the onboard sensors according to the contact angle estimation between the wheel and ground. A slip control is implemented based on slip ratio to adjust the wheel velocity when the slip is detected. Simulation and experimental results verify the effectiveness of the approach that enables the robot autonomously climbing up on different steps and uneven terrain.
Meseret A. Tadese,Francisco Yumbla,Nabih Pico,Hyungpil Moon 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
A precise dynamic model is critical for collaborative robots to achieve satisfactory performance in modelbased control or other applications such as dynamic simulation and external torque estimation. However, due to nonlinear friction behavior in robot actuation, it is difficult to identify precise dynamic parameters. In this paper, a reliable dynamic friction model, which incorporates the influence of temperature fluctuation on joint friction, is utilized to increase the accuracy of identified dynamic parameters. First, the friction of the joint module is investigated. Extensive test series are performed in the full velocity operating range at temperatures ranging from 23 ℃ to 51 ℃ to investigate friction dependency on joint module temperature. Then, dynamic parameter identification is performed using the inverse dynamics identification model and weighted least squares method. Based on the friction model identified in the first step, friction toque is computed, and the effect is eliminated by subtracting it from experimental data for dynamic parameter identification. Finally, the proposed notion is verified experimentally, and the results demonstrate that using a precise dynamic friction model improves the accuracy of dynamic parameters identification.