• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.52-57
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• 2014

This paper presents an implementation of a smooth path planning method considering physical limits on a real time operating system for a two-wheel mobile robot. A Bezier curve is utilized to make a smooth path considering a robot's position and direction angle through the defined path. A convolution operator is used to generate the center velocity trajectory to travel the distance of the planned path while satisfying the physical limits. The joint space velocity is computed to drive the two-wheel mobile robot from the center velocity. Trajectory planning, velocity command according to the planned trajectory, and monitoring of encoder data are implemented with a multi-tasking system. And the synchronization of tasks is performed with a real-time mechanism of Event Flag. A real time system with multi-tasks is implemented and the result is compared with a non-real-time system in terms of path tracking to the designed path. The result shows the usefulness of a real-time multi-tasking system to the control system which requires real-time features.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.39-45
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• 2008

The most important elements in flexible pavement design criteria are stress and strain distributions. To obtain reasonable stress and strain distributions in pavements, moving wheel loads must be applied to analyze the pavement responses. In this study, finite element analysis was used to identify the three-dimensional states using the vehicle load into a constant-position / time-variable load (25, 50 and 80km/hr). In an elastic system, the strain is the same in both longitudinal and transverse directions under a single wheel. However, the same is not necessary in a viscoelastic system. Test results showed that the maximum values between transverse and longitudinal strains the bottom of asphalt concrete base layers under 25km/hr were were about 40 percent.

• Journal of Drive and Control
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• v.19 no.4
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• pp.19-28
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• 2022

This paper introduces an automatic steering system for straight traveling capable of being mounted on drivable agricultural machinery which user can handle it such as a tractor, a transplant, etc. The modular automatic steering device proposed in the paper is composed of RTK GNSS, IMU, HMI, hydraulic valve, and wheel sensor. The path generation method of the automatic steering system is obtained from two location information(latitude and longitude on each point) measured by GNSS in advance. From HMI, a straight path(AB line) can be created by connecting latitude and longitude on each point and the device makes the machine able to follow the path. During traveling along the reference path, it acquires the real time position data every sample time(0.1s), compares the reference with them and calculates the lateral deviation. The values of deviation are used to control the steering angle of the machine using hydraulic valve mounted on the axle of front wheel. In this paper, Pure Pursuit algorithm is applied used in autonomous vehicles frequently. For the analysis of traveling characteristics, field tests were executed about these conditions: velocity of 2, 3, 4km/h which is applied to general agricultural work and ground surface of solid(asphalt) and weak condition(soil) such as farmland. In the case of weak ground state, two experiments were executed about no-load(without work) and load(with work such as plowing). The maximum average deviations were presented 2.44cm, 7.32cm, and 11.34cm during traveling on three ground conditions : asphalt, soil without load and with load(plowing).

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.1
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• pp.30-37
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• 2003

In order to replace the manual ultrasonic testing(UT) with an automated UT(AUT), a scanner which enables us to control the positions of a transducer is essential. Encoders have been commonly used to obtain the position information from the conventional scanners controlled by motor. Encoders have various advantages in many aspects. However, if the slip of motor wheel occurs during scanning, various errors are involved in the position accuracy. Thus, the position information of encoders becomes meaningless in case of slip. The reliability of AUT results nay become serious problem. Hence, slip must be avoided, but it can not be completely avoided at present time. In this paper, a new idea that surface wave is used to solve this problem and replace encoders has been proposed. It is shown that this idea can be employed in AUT scanner without encoders. That is, one transducer transmitting surface wave is fixed and the other transducer attached to the scanner receives UT signal. Then, computer calculates the present position of scanner based on the information given by surface wave. Thus, the movement of a scanner can be controlled by the amount of input based on the information obtained.

• Science of Emotion and Sensibility
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• v.21 no.2
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• pp.29-42
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• 2018

As information technology is more actively incorporated into automobiles, the role of IVIS (In-Vehicle Infotainment System) is becoming increasingly important for providing convenience and entertainment for drivers. However, using the infotainment systems while driving requires task switching and attending to two visual resources simultaneously. We simulated a setting where participants have to drive while interacting with the infotainment system and examined how task difficulty and motor cues impact driver task-switching and driving performance, specifically whether the effects of motor cues differ depending on task difficulty. For the infotainment display, we used two types of number array depending on the congruency between the digit repetition and the chunking unit, while task difficulty was manipulated by the size of the touch-keys. Participants were instructed to dial two numbers on the screen while we recorded the dialing time, lateral position, inter-key press intervals, and steering wheel control. We found that dialing time and lateral position were affected by task difficulty, while the type of number array had no effect. However, the inter-key press intervals between chunked numbers and steering wheel movement both increased when participants had to use an incongruent number array, which indicates that, if number digits are repeated, chunking is ignored by the drivers. Our findings indicate that, in a dual-task condition, motor cues offset the effect of chunking and can effectively signal the timing for task switching.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.16-21
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• 2007

Various perturbations by the sun, the moon and the earth itself cause a continuous change in nominal position of a geostationary satellite. In order to maintain the satellite within a required window, north-south station keeping for controlling inclination and right ascension of ascending node, and east-west station keeping for controlling eccentricity and longitude are required. In this paper, station keeping maneuver simulation for Communication, Ocean and Meteorological Satellite (COMS) was performed using COMS Flight Dynamics Software(FDS) and the results were analyzed. COMS performs weekly based east-west/north-south station keeping to maintain satellite within ${\pm}0.05^{\circ}$ at the nominal longitude of $128.2^{\circ}E$. In addition, COMS performs wheel off-loading maneuver twice a day to eliminate attitude error caused by one-solar wing in the south panel of the satellite. In this paper, station keeping maneuver considering wheel off-loading maneuver was performed and the results showed that COMS can be maintained well within ${\pm}0.05^{\circ}$ window using COMS FDS.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.1
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• pp.21-27
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• 2022

Traditional automobile or 2-wheeled robot have limitations on mobility because of their mechanical structure. As traditional automobile is being replaced by electric cars, robot technology is applied to the car industry. In robotics, many researchers worked on omnidirectional mobile robot and produced lots of noticeable results. However in many of the results, specialized wheels such as Mecanum wheels are required. That imposes restrictions on robot speed and outdoor driving. We proposed a 2-wheeled modular robot that has omnidirectional mobility without using specialized wheels. In this paper, we propose a 4-wheeled omnidirectional mobile robot that consists of those two modular robots. The proposed robot adopts electric brakes to combine wheel housings and the robot body or to separate wheel housings from the robot body. Two absolute-type encoders and four incremental encoders are used to control the position of the wheel housing and velocities of the wheels. The proposed robot has omnidirectional mobility and can move fast and outdoor with normal tire wheels. We implemented the proposed robot and the feasibility and stability of the robot is verified by two separate experiments.

• Journal of IKEEE
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• v.25 no.1
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• pp.148-155
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• 2021

As robot technology advances, research on the driving system of mobile robots is actively being conducted. The driving system of a mobile robot configured based on two-wheels and four-wheels has an advantage in unidirectional driving such as a straight line, but has disadvantages in turning direction and rotating in place. A ball robot using a ball as a wheel has an advantage in omnidirectional movement, but due to its structurally unstable characteristics, balancing control to maintain attitude and driving control for movement are required. By estimating the position from an encoder attached to the motor, conventional ball robots have a limitation, which causes the accumulation of errors during driving control. In this study, a driving control system was proposed that estimates the position coordinates of a ball robot through image processing and uses it for driving control. A driving control system including an image processing unit, a communication unit, a display unit, and a control unit for estimating the position of the ball robot was designed and manufactured. Through the driving control experiment applying the driving control system of the ball robot, it was confirmed that the ball robot was controlled within the error range of ±50.3mm in the x-axis direction and ±53.9mm in the y-axis direction without accumulating errors.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.28-35
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• 2017

Recently, conventional hydraulic car lift systems face the technological limitations due to a lack of height control. The demand for height controllability is required in many tasks such as wheel alignment, and requires compensation for the structural deformation of the lift caused by irregular load distribution. In order to resolve this limitation of the conventional car lift, in this work, a new type of a hydraulic vehicle lift using a magneto-rheological (MR) valve system is proposed and analyzed. Firstly, the dynamic model of vehicle lift is formulated to evaluate control performance; subsequently, an MR valve is designed to obtain the desired pressure drop required in the car lift. Next, a proportional-integral-derivative (PID) controller is formulated to achieve accurate control of the lifting height and then computer simulations are undertaken to show accurate height control performances of the proposed new car lift system.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.19-23
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• 2009

This paper focuses on vehicle fuel economy improvement using D-Range neutral control of automatic transmission. The system objected to reducing of fuel consumption during idle. Usually, turbine of conventional auto transmission is mechanically linked to wheel during idling condition. Therefore speed ratio of torque converter is zero for that period. This causes needless power loss by the torque converter slip. To improve this inefficiency automobile makers develops electronically-controlled D-range neutral control system. The D-range neutral control system minimizes slip on the torque converter by shifting gear to a neutral position during vehicle stoped with D-range gear position. However there's insufficient study about the effect of D-range neutral control system on vehicle fuel economy. In this paper, researches are performed on effect of D-range neutral control system on vehicle fuel economy by experiment with two different vehicle. And it is also estimated the effect on vehicle fuel economy using computer simulation. As a result, 1.8% of LA-4 mode fuel economy improvement can be achieved in a vehicle by D-range neutral control system.