Hyun Do Choi

Optimal Design of a New Wheeled Mobile Robot Based on a Kinetic Analysis of the Stair Climbing States

In this paper, we propose a new wheeled mobile robot (WMR) with a passive linkage-type locomotive mechanism that allows the WMR to adapt passively to rough terrain and climb up stairs, making it ideal for applications such as building inspection, building security, and military reconnaissance. A simple four-bar linkage mechanism and a limited pin joint are proposed after considering two design needs: adaptability and passivity. To improve the WMR’s ability to climb stairs, we divided the stair-climbing motion into several stages, taking into consideration the status of the points of contact between the driving wheels and the step. For each of the suggested stages, a kinetic analysis was accomplished and validated using the multi-body dynamic analysis software package ADAMS. The object functions are presented for the stages that influence the WMR’s ability to climb stairs. The optimization of the object functions is carried out using the multi-objective optimization method.

Obstacle negotiation for the rescue robot with variable single-tracked mechanism

The purpose of this paper is to provide a practical introduction to a mobile robot developed for rescue operations. The robot has a variable single-tracked mechanism for the driving part, making it inherently able to overcome indoor obstacles such as stairs. In this research, the robot is given the capacity of obstacle negotiation as a hardware attachment in order to realize autonomous navigation that is well matched to an original target, rescue operation. There are three driving modes to choose from, and the robot recognizes the forward environment once and estimates whether or not any obstacles are there. Experimental results show that the robot moves in opposition to several obstacles, reflecting the proposed algorithm ultimately.

Floor-types identification method for wheel robot using impedance variation

Wheel robots have been widely used in indoor. An indoor room consists of various floor-types such as wood, carpet, marble and so on. The various floor-types cause odometry error and energy loss due to slip. Floor-type identification which allows a robot to detect changing floor-types and to adapt control and motion planning has been needed to solve this problem. In this paper, we propose sensing method for wheel robot to identify floor-types by using impedance variation. The impedance variation measures a voltage variation of a side brush motor depending on floor-types. The original side brush function is to sweep the dust in the vacuum cleaning robot. This approach does not require any sensors and estimates floor-types from the impedance variation. We present and analyze experimental data collected on three different floor-types: wood, marble and carpet. As a result, we verify the fact that the floor-types can be identified by the proposed method.

Independent traction control for uneven terrain using stick-slip phenomenon: application to a stair climbing robot

Abstract Mobile robots are being developed for building inspection and security, military reconnaissance, and planetary exploration. In such applications, the robot is expected to encounter rough terrain. In rough terrain, it is important for mobile robots to maintain adequate traction as excessive wheel slip causes the robot to lose mobility or even be 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 algorithm estimates the stick-slip of the wheels based on estimation of angular acceleration. Thus, the traction force induced by torque of wheel converses between the maximum static friction and kinetic friction. Simulations and experiments are performed to validate the algorithm. The proposed traction control algorithm yielded a 40.5% reduction of total slip distance and 25.6% reduction of power consumption compared with the standard velocity control method. Furthermore, the algorithm does not require a complex wheel-soil interaction model or optimization of robot kinematics.

Development of the piezoelectric motor using momentum generated by bimorphs

Piezoelectric motors have been used in many applications where excellent controllability and fine position resolution are required and/or magnetic-field noise should be eliminated. However, the piezoelectric motor has two major drawbacks, difficulty in maintaining vibration amplitude constantly with temperature rise and wear and heat generation induced by dielectric and mechanical losses. In this article, a new piezoelectric motor that can overcome these problems is proposed. The proposed piezoelectric motor is operated using momentum exchange between four bimorphs and a rotor. In order to maximize the steady-state velocity and static torque of the proposed motor, a guideline is established using two bimorph models. The guideline is partially verified by comparison between simulations and experiments. There was no heat generation in a few hours of operation in experiments.

A new mobile robot with a passive mechanism and a stereo vision system for hazardous terrain exploration

The purpose of this project is to develop a mobile robot for hazardous terrain exploration. The exploration of hazardous terrain requires the development of a passive mechanism adaptable to such terrain and a sensing system for obstacle avoidance, as well as a remote control. We designed a new mobile robot, the Ronahz 6-wheel robot, which uses a passive mechanism that can adapt to hazardous terrains and building stairways without any active control. The suggested passive linkage mechanism consists of a simple four-bar linkage mechanism. In addition, we install a stereo vision system for obstacle avoidance, as well as a remote control. Wide dynamic range CCD cameras are used for outdoor navigation. A stereo vision system commonly requires high computational power. Therefore, we use a new high-speed stereo correspondence algorithm, triangulation, and iterative closest point (ICP) registration to reduce computation time. Disparity maps computed by a newly proposed, high-speed method are sent to the operator by a wireless LAN equipment. At the remote control site, a three-dimensional digital map around a mobile robot is built by ICP registration and reconstruction process, and this three-dimensional map is displayed for the operator. This process allows the operator to sense the environment around the robot and to give commands to the mobile robot when the robot is in a remote site.Copyright

Optimal Design of a New Wheeled Mobile Robot by Kinetic Analysis for the Stair-Climbing States

Many mobile robots have been developed in the various application fields, such as building inspection and security, military reconnaissance, space and undersea exploration, and warehouse services (Muir & Neuman, 1987). Mobile robots are designed with the specific locomotive mechanisms according to the environment of the application field. The various locomotive mechanisms used in mobile robots can be classified into three types: wheeled, tracked, and legged type (Kim, 1999) (Lee et al, 2000). Each locomotion type has its inherent advantages and disadvantages as described below. The wheeled mobile robots (WMRs) weigh less than robots of the other locomotive types and have other inherent advantages, such as high energy efficiency, low noise level, etc (Muir & Neuman, 1987). In comparison with legged mobile robots, the WMRs have a simpler driving part and a plain control strategy, but they have the poor adaptability to the terrain. Tracked mobile robots have the merit of easy off-road travelling. However, they usually have a heavier driving part and need more power for turning motions, in comparison with mobile robots with other locomotive types. Additionally, tracked mobile robots are usually too noisy to be utilized for in-door applications. Legged mobile robots can easily adapt to the unstructured environments, such as off-road environments, but require more actuators to stabilize themselves than mobile robots in the other two categories. As the locomotion mechanisms are complex and need more complicated control algorithms, legged mobile robots have poor mobility on the plane surfaces. Various types of mobile robots that are capable of climbing up stairs have been developed but, until now, most of the mobile robots developed have tracked-type locomotive mechanisms (Kohler et al., 1976) (Maeda et al., 1985) (Yoneda et al., 1997) (Iwamoto & Yamamoto, 1985) (Iwamoto & Yamamoto, 1990). For the purpose of developing a robot capable of traversing the stairs, Estier (Estier et al., 2000) proposed a WMR with three 4-bar linkage mechanisms, by applying the concept of the instantaneous centre of rotation. To explore Mars, Volpe (Volpe et al., 1997) developed a WMR named Rockey 7, which is capable of climbing up steps about 1.5 times as large as the wheel diameter. O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m

Self-adjustable docking mechanism with passive linkage for mobile robot

Autonomous mobile robot increasingly expands its functionality into various applications where the long-term autonomous capability is necessary. These applications, warehouse service, building inspection, exploration of unknown terrains and military reconnaissance, require the mobile robot to correspond with the command of remote operators or environments. To meet this requirement, automatic recharging station can be used for a robot not to be taken offline. However, the range of docking error is wide by various homing algorithms and kinds of sensors. This paper describes a new docking mechanism developed to compensate entry error of robot in homing and to maintain robust state in the process of recharging battery without actuators and sensors. The proposed mechanism is self-adjustable to position and orientation of robot and reconfigures its states by driving force of mobile robot without any active energy elements. The geometric parameters are determined to avoid mechanical interference in docking procedure and specifications of springs are obtained from optimization which maximizes the grip force with constraint induced at each docking process. The docking mechanism can compensate for ±5cm lateral offset error and ±30° orientation error of mobile robot and holds it over 20N load after docking is finished.Copyright

Development of piezoelectric motor using momentum generated by bimorph

Piezoelectric motors have been used in many applications where excellent controllability and fine position resolution are required or magnetic field noise should be eliminated. However, the piezoelectric motor has two major drawbacks. One is difficulty in maintaining constant vibration amplitude with temperature rise and wear, and the other is heat generation induced by dielectric and mechanical losses. A piezoelectric motor that can overcome these problems is proposed. It is operated using momentum exchange between a bimorph and a rotor. To maximize the motors steady state velocity and static torque, a guideline is established using two bimorph models. The guideline is then partially validated by comparison between simulation and experiment results. There was no heat generation in several hours of testing.