• The Journal of Korea Robotics Society
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• v.17 no.4
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• pp.438-446
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• 2022

In this paper, we propose an intelligent three-legged landing system that can maintain stability and level even on rough terrain than conventional four-legged landing systems. Conventional landing gear has the limitation that it requires flat terrain for landing. The 3-leg landing system proposed in this paper extends the usable range of the legs and reduces the weight, allowing the quadcopter to operate in various environments. To do this, kinematics determine the joint angles and coordinates of the legs of the two-link structure. Based on the angle value of the quadcopter detected via the IMU sensor, the leg control method that corrects the posture is determined. A force sensor attached to the end of the leg is used to detect contact with the ground. At the moment of contact with the ground, landing control starts according to the value of the IMU sensor. The proposed system verifies its reliability in various environments through an indoor landing test stand. Finally, in an outdoor environment, the quadcopter lands on a 20 degree incline and 20 cm rough terrain after flight. This demonstrates the stability and effectiveness of the 3-leg landing system even on rough terrain compared to the 4-leg landing system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.425-426
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• 2011

• Journal of the Korean Society of Systems Engineering
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• v.15 no.2
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• pp.1-8
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• 2019

Autonomous vehicles operated in the rough terrain environment must satisfy various technical requirements in order to improve the speed. Therefore, in order to design and implement a technical architecture that satisfies the requirements for speed improvement of autonomous vehicles, it is necessary to consider the overall technology of hardware and software to be mounted. In this study, the technical architecture of the autonomous vehicle operating in the rough terrain environment is presented. In order to realize high speed driving in pavement driving environment and other environment, it should be designed to improve the fast and accurate recognition performance and collect high quality database. and it should be determined the correct running speed from the running ability analysis and the frictional force estimation on the running road. We also improved synchronization performance by providing precise navigation information(time) to each hardware and software.

• The Journal of Korea Robotics Society
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• v.9 no.2
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• pp.124-131
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• 2014

The robot mechanisms that were previously researched had only been conducted for the purpose of overcoming the obstacles stably at low speed driving and enhancing the stability against high speed circuitous driving, and yet, the mechanism satisfying two purposes. However, in order to stably drive with high speed on rough terrain, there is a need for satisfying both of these purposes, as well as testing the efficiency of the mechanisms at high speed driving. There, this paper simulated some of the passive mechanisms and focused on checking the performances of passive mechanisms through simulations and analyzing each mechanism on the basis of an evaluation index. The simulation was conducted by Adams (The Multi-body Dynamics Simulation Solution) and used various types of passive mechanisms which were introduced in the robotics field. As a result, the study confirmed that passive mechanisms have a number of situations that affect the driving stability on each direction of roll and pitch. Further study is needed about active mechanism.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.2
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• pp.184-191
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• 2009

The common requirements of rough terrain mobile robots are long-term operation and high mobility in rough terrain to perform difficult tasks. In rough terrain, excessive wheel slip could cause an increase in the amount of dissipated energy at the contact point between the wheel and ground or, even more seriously, the robot could lose all mobility and become trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The proposed traction algorithm is analogous to the stick-slip friction mechanism. The algorithm estimates the slippage of wheels by angular acceleration change, and controls the increase or decrease state of torque applied to wheels Simulations are performed to validate the algorithm. The proposed traction control algorithm yielded a 65.4% reduction of total slip distance and 70.6% reduction of power consumption compared with the standard velocity control method.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.1
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• pp.58-69
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• 2014

This paper proposes a method for predicting maximum friction coefficients and optimal slip ratios as optimal control parameters for traction control or slip control of autonomous mobile robots on rough terrain. This paper focuses on strength of ground surface which indicates different characteristics depending on material types on surface. Strength of various material types can be estimated by Willoughby sinkage model and by a developed testbed which can measure forces, velocities, and displacements generated by wheel-terrain interaction. Estimated strength is collaborated on building improved Brixius model with friction-slip data from experiments with the testbed over sand and grass material. Improved Brixius model covers widespread material types in outdoor environments on predicting friction-slip characteristics depending on strength of ground surface. Thus, a prediction model for obtaining optimal control parameters is derived by partial differentiation of the improved Brixius model with respect to slip. This prediction model can be applied to autonomous mobile robots and finally gives secure maneuverability on rough terrain. Proposed method is verified by various experiments under similar conditions with the ones for real outdoor robots.

• Wind and Structures
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• v.3 no.3
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• pp.143-158
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• 2000

This report presents the findings of a one-year monitoring effort to empirically characterize and evaluate the nature of near-ground winds for structural engineering purposes. The current wind engineering practice in the United States does not explicitly consider certain important near-ground wind characteristics in typical rough terrain conditions and the possible effect on efficient design of low-rise structures, such as homes and other light-frame buildings that comprise most of the building population. Therefore, near ground wind data was collected for the purpose of comparing actual near-ground wind characteristics to the current U.S. wind engineering practice. The study provides data depicting variability of wind speeds, wind velocity profiles for a major thunderstorm event and a northeaster, and the influence of thunderstorms on annual extreme wind speeds at various heights above ground in a typical rough environment. Data showing the decrease in the power law exponent with increasing wind speed is also presented. It is demonstrated that near-ground wind speeds (i.e., less than 10 m above ground) are likely to be over-estimated in the current design practice by as much as 20 percent which may result in wind load over-estimate of about 50% for low-rise buildings in typical rough terrain. The importance of thunderstorm wind profiles on determination of design wind speeds and building loads (particularly for buildings substantially taller than 10 m) is also discussed. Recommendations are given for possible improvements to the current design practice in the United States with respect to low-rise buildings in rough terrain and for the need to study the impact of thunderstorm gust profile shapes on extreme value wind speed estimates and building loads.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.449-455
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• 2014

This paper presents a method for developing a TM (Traversability Map) from a DTM (Digital Terrain Model) collected by remote sensors of autonomous mobile robots. Such a map can be used to plan traversable paths and estimate navigation speed quantitatively in real time for robots capable of performing autonomous tasks over rough terrain environments. The proposed method consists of three parts: a DTM partition module which divides the DTM into equally spaced patches, a terrain information module which extracts the slope and roughness of the partitioned patches using the curve fitting and the fractal-based triangular prism method, and a traversability analysis module which assesses traversability incorporating with extracted terrain information and fuzzy inference to construct a TM. The potential of the proposed method is validated via simulation works over a set of fractal DTMs.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.697-703
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• 2011

This article describes a snake robot with 2-DOF actuator modules. The 2-DOF actuator modules make the snake robot move in the 3D space so that the snake robot can cross obstacles and rough terrain. Each 2-DOF actuator module is designed to have high torque output and an embedded controller. A cross bracket connecting the modules is designed be able to support the weight of two actuator modules. The developed snake robot shows 3-D motions such as side winding, standing/monitoring, and can climb in a narrow pipe with high torque modules. The snake robot moves fast with passive wheels in a plane while crossing obstacles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.146-154
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• 1991

As the application of robotic systems expand its scope, more research efforts are given in providing mobility to the robotic systems so that they can travel across various paths including those with formidable obstacles such as stairways or rough terrains. Legged locomotion is mainly concerned because the walking motion, like that of animal behavior, has many advantages over wheel type or track type locomotion especially in rough terrain. Walking robot, in general, having a discrete number of legs, have inherently low static stability. Static stability can be increased to a certain degree, by improving walking method, but it has many limitations such as reduced travel speed. A very promising possibility lies in the use of balancing weight, nevertheless its actual implementation is very rare. In this study, a 4-legged walking machine is developed and the static stability margin is increased with the balancing weight. In the future, this robot will be used to take an experiment on the walking in mush terrain.