• Journal of Institute of Control, Robotics and Systems
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• v.11 no.8
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• pp.696-703
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• 2005

Since most autonomous mobile robots are powered by a battery, it is important to increase the continuous operating time without recharging. This can be achieved by improving the energy efficiency of a mobile robot, but little research on energy efficiency has been performed. This paper proposes two methods for improving the energy efficiency of an omnidirectional mobile robot.. One method is to realize a continuously variable transmission (CVT) by adopting the mechanism of steerable omnidirectional wheels. The other is the proposed steering algorithm in which wheel arrangement of the mobile robot is continuously adjusted so as to obtain the maximum energy efficiency of the motors during navigation. In addition, new omnidirectional wheels which can be transformed to the conventional wheels depending on the driving conditions are proposed to compensate for less efficient omnidirectional drive mode. Various tests show that motion control of the OMR-SOW works satisfactorily and the proposed steering algorithm for CVT can provide higher energy efficiency than the algorithm using a fixed steering angle. In addition, it is shown that the differential drive mode can give better energy efficiency than the omnidirectional drive mode.

• The Journal of Korea Robotics Society
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• v.9 no.4
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• pp.250-257
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• 2014

In this paper, a new mobile robot, so called a rollerbot, is presented, which has single body and rugby-ball shaped roller wheel. A rollerbot has single point contact on ground and low energy consumption in motion because of the reduced friction. By changing center of mass using a balancing weight, a rollerbot is able to get steering force. The vertical position of mass center of the rollerbot in this paper is designed to lie inside radius of the roller wheel, so that to have stable equilibrium position. Thus, the posture and the steering control of the rollerbot can be easily done by changing the center of mass. Kinematics of the rollerbot is derived by transformation of differential motion in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.190-199
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• 1993

In this study a three-axes mobile robot which has two independently controlled driving wheels and a function of simultaneously steering the driving wheels has been developed. Two-motion modes of the mobile robot, the first is a differential velocity motion of two driving wheels and the second is a equal driving and steering motion, have been analyzed and the kinematic and dymanic analyses about the each motion mode have been carried out. As a result of dynamic analysis, the torque used on a motor control and acceleration have been derived explicitly. Hence, a computation time is saved effectively and a real time control of the mobile robot considering the dynamics has become possible. Through a simulation the results considering the dynamics have been compared with that no regarding the dynamics and the possibility of real-time control has been proved.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.142-147
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• 1988

Free-path-type guidance system does not need a hardwired path in the environment so that it gives a mobile robot a flexible path. ln this study to achieve the free-path-type guidance system for a mobile robot which is steered by the differential steering of both drive forewheels, position recognition systems are constructed using odometer system as an internal position sensor. Two odometer systems, a auxiliary wheel odometer and a 2-encoder odometer system are constructed and path following algorithms using these odometer systems are designed and experimented. PID control type is adopted in the path following algorithms.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1429-1436
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• 2013

This study presents an approach for designing a vehicle rollover prevention controller using differential game theory and multi-level programming. The rollover prevention problem can be modeled as a non-cooperative zero-sum two-player differential game. A controller as an equilibrium solution of the differential game guarantees the worst-case performance against every possible steering input. To obtain an equilibrium solution to the differential game with a small amount of computational effort, a multi-level programming approach with a relaxation procedure is used. To cope with the loss of maneuverability caused by the active suspension, an electronic stability program (ESP) is adopted. Through simulations, the proposed method is shown to be effective in obtaining an equilibrium solution of the differential game.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.261-266
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• 2002

Up to now a wide variety of researches on inpipe robots for inspection have been introduced, but it still seems to be difficult to construct a robot providing mobility sufficient to navigate inside the complicated configuration of underground pipelines. The robot for the inspection of pipelines should freely move along the basic configuration of pipelines such as along horizontal or vertical pipelines. Moreover it should be able to travel along reducers and elbows, and especially the capability for steering in branches is essential to it. In this report, citical points and technologies in the development of the inpipe inspection robots are introduced and inpipe robots developed for last several years are introduced.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.859-864
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• 2003

This paper presents a design for the novel suspension mechanism of a two-wheeled mobile robot having two casters which is used for indoor environment. Although the indoor environment is less rough than the outdoor one, the fixed caster mechanism has some problems such as causing the robot to be immovable because robot's driving wheels do not have contact with the ground. Therefore, we tried installing a spring-damper suspension mechanism to keep driving capability and to remove pitching phenomenon. However, this suspension mechanism also has the problem, which the robot body inclined by disturbances does not return to the initial position. To deal with above problems and to accomplish desired performances, we designed the Multilayered Suspension Mechanism, which has springs and dampers working partially according to the inclined angle and angular velocity of robot body concerned with pitching. To analyze design, the equations of motion describing their dynamics were developed. Using the equations, simulation results show the improved performance. We confirm the usefulness of the Multilayered Suspension Mechanism by construction and test of a actual prototype.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.69-70
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• 2013

By using differential force between left and right wheel, lateral motion can be controlled known as Direct Yaw-moment Control (DYC). In previous researches, DYC control is proposed to increase the stability of the vehicle, but maneuverability has not been discussed sufficiently. The car handling condition which is called the index parameter of maneuverability is dependent on the vehicle velocity and steering angle. To achieve the desired vehicle's cornering path, the car handling condition must be considered sufficiently. In this paper, the novel DYC method is proposed which gives the car handling condition regardless of the longitudinal speed. The proposed controller is based on the PI controller to feedback the curvature parameter. The controlled system shows the advantages of DYC regarding to the reference trajectory by the dual motor system. With respect to the uncontrolled model, the effectiveness of the proposed method is validated by numerical examples.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.225-231
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• 1997

This paper reports on the theoretical study of the delivery pressure ripples of a positive displacement vane pump which is widely used for automobile power steering. Pressure ripples occur due to the flow tipples which induced cam ring profiles and reverse flow from the delivery ports. In this paper, the mathematical model for analyzing the pressure ripples has been presented, and set of the differential equationshave been solved using the Runge-Kutta method. As the results of analysis, instant ideal flow ripples, internal pressure, delivery pressure ripples, and delivery flow ripples have been presented. Internal pressure was related to delivery pressure variations, and amplitude of pressure tipples was increased with rotational speed and delivery pressure.

• Journal of Auto-vehicle Safety Association
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• v.5 no.2
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• pp.32-38
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• 2013

This paper presents collision avoidance using model predictive control algorithm. A model predictive control algorithm determines lateral tire force and yaw moment and steering angle input and differential braking input is determined from lateral tire force and yaw moment. A constraint for model predictive control is designed for obstacle avoidance. A objective function is designed to minimize lateral tire force and yaw moment input and to follow changed lane after collision avoidance. The performance of proposed algorithm has been investigated via computer simulation conducted to vehicle dynamic software CARSIM and Matlab/Simulink.