• Journal of Institute of Control, Robotics and Systems
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• v.17 no.6
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• pp.513-520
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• 2011

This paper presents the motion planning of robotic vehicles for the path tracking and the obstacle avoidance. To follow the given path, the vehicle moves through the turning radius obtained through the pure pursuit method, which is a geometric path tracking method. In this paper, we assume that the vehicle is equipped with a 2D laser scanner, allowing it to avoid obstacles within its sensing range. The turning radius for avoiding the obstacle, which is inversely proportional to the virtual force, is then calculated. Therefore, these two kinds of the turning radius are used to generate the steering angle for the front wheel of the vehicle. And the vehicle reduces the velocity when it meets the obstacle or the large steering angle using the potentials of obstacle points and the steering angle. Thus the motion planning of the vehicle is done by planning the steering angle for the front wheels and the velocity. Finally, the performance of the proposed method is tested through simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.3
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• pp.199-209
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• 2015

This paper presents a model predictive control (MPC) approach to control the steering angle in an autonomous vehicle. In designing a highly automated driving control algorithm, one of the research issues is to cope with probable risky situations for enhancement of safety. While human drivers maneuver the vehicle, they determine the appropriate steering angle and acceleration based on the predictable trajectories of surrounding vehicles. Likewise, it is required that the automated driving control algorithm should determine the desired steering angle and acceleration with the consideration of not only the current states of surrounding vehicles but also their predictable behaviors. Then, in order to guarantee safety to the possible change of traffic situation surrounding the subject vehicle during a finite time-horizon, we define a safe driving envelope with the consideration of probable risky behaviors among the predicted probable behaviors of surrounding vehicles over a finite prediction horizon. For the control of the vehicle while satisfying the safe driving envelope and system constraints over a finite prediction horizon, a MPC approach is used in this research. At each time step, MPC based controller computes the desired steering angle to keep the subject vehicle in the safe driving envelope over a finite prediction horizon. Simulation and experimental tests show the effectiveness of the proposed algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.101-109
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• 1994

Recently, four-wheel steering systems have been developed and studied as one of the latest automotive technologies for improving the handling characteristics of a vehicle. In much of the proposed four-wheel steering systems, the side slip angle at the vehicle's center of gravity is maintained at zero. This approach allows the greater maneuverability at low speed by means of counter-phase rear steering and the improved stability at high speed through same-phase rear steering. In this paper, the effects of several four-wheel steering systems are studied and discussed on the responsiveness and stability of the vehicle by using the linear analysis. Especially, the effects of the cornering stiffnesses of both front and rear wheels are investigated on the yaw velocity gain and critical speed of the vehicle.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.87-92
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• 2022

In this paper, a study was conducted on the design of an array element that can be applied to the AESA radar for seeker. An antenna for application to AESA radar should choose an optimal radiation element to be applied to an array antenna in order to secure electronical beam steering characteristics, and consider beam steering characteristics when designing. In particular, in order to satisfy the wide-angle beam steering characteristics, the wide-angle impedance matching technique should be used to minimize the scan blindness region that may occur during wide-angle steering. As such, securing the stability of system operation is becoming an important design consideration for AESA radar. In this paper, WAIM is applied to the end of the radiation element to improve the characteristics of the radiation element applied to the AESA radar antenna device, and the change in the performance of the active reflection coefficient, which is a stable operation index of the system, is reviewed. The final performance result verified the validity of the proposed method by mathematically synthesizing the simulation data.

• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.251-259
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• 2023

In the path traveling of differential-drive robots, the steering controller plays an important role in determining the path-following performance. When a robot with a pure-pursuit algorithm is used to continuously drive a right-angled driving path in an unstructured environment without turning in place, the robot cannot accurately follow the right-angled path and stops driving due to the ground and motor load caused by turning. In the case of pure-pursuit, only the current robot position and the steering angle to the current target path point are generated, and the steering component does not reflect the speed plan, which requires improvement for precise path following. In this study, we propose a driving algorithm for differentially driven robots that enables precise path following by planning the driving speed using the radius of curvature and fusing the planned speed with the steering angle of the existing pure-pursuit controller, similar to the Model Predict Control control that reflects speed planning. When speed planning is applied, the robot slows down before entering a right-angle path and returns to the input speed when leaving the right-angle path. The pure-pursuit controller then fuses the steering angle calculated at each path point with the accelerated and decelerated velocity to achieve more precise following of the orthogonal path.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.1
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• pp.23-30
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• 2024

This paper dedcribes the design. verification, and analysis techniques for an advanced phased array antenna. When applying an active phased array antenna to an aircraft or missile, miniaturization of the array antenna and wide-angle beam steering characteristics can be unavoidable antenna design considerations. In particular, the active reflection coefficient characteristics when electronically steering a wide-angle beam is a design parameter that must be minimized in terms of system survival and system performance. As a radiator suitable for broadband characteristics and wide-angle beam steering, this paper designed an array structure using SFN and minimized the active reflection coefficient according to beam steering of up to 40° based on the spherical coordivate system angle. The bandwidth of the radiator was confirmed to be 3GHz based on active reflection in the Ka-band. In addition, the performance of the actually manufactured 8by8 array antenna wsa analyzed by measuring the single pattern of the radiator through a near-field test, mathematically synthesizing it, and predicting the Tx/TRx beam used in the seeker system.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.186-193
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• 2000

EPS(Electric Power Steering) systems have many advantages over traditional hydraulic power steering systems in space efficiency engine efficiency and environmental compatibility. In this paper an EPS system control logic using a torque map is proposed. The main function of the EPS system is to reduce the steering torque exerted by a driver by assist of an electric motor. Vehcile speed steering torque and steering wheel angle are measured and fed back to the EPS control system where appropriate assist torque is generated to assist the operator's steering effort. Another capability of the EPS system for easy adaptation to different steering feels via simple tuning is demonstrated by the experiments. It will be also verified that the EPS system can also improve damping and return performance of the steering wheel by control of the assist motor.

• Journal of Drive and Control
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• v.13 no.1
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• pp.18-26
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• 2016

This research is conducted to develop an automatic steering system for parallel parking, and the performance of the system was evaluated by parallel parking a conventional vehicle. The automatic steering system consisted of MDPS (motor driven power steering) to control steering, ESC (electronic stability control) to acquire wheel speed, ultrasonic sensors to recognize the parking space, and a controller to communicate and handle data. The parallel parking process using the automatic steering control consisted of parking space recognition, parking path generation, and parking path tracking. The path for parallel parking was generated based on a kinematic model of a conventional vehicle, and a PI controller was used to control the steering angle for path tracking. Parallel parking using the automatic steering control was conducted according to vehicle speed conditions. The results show that the errors on the x-axis and y-axis were below 0.54 m and 0.14 m, respectively, and the error on the steering angle was less than $1^{\circ}$. Therefore, it is possible to implement parallel parking using an automatic steering control system for conventional vehicles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.931-942
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• 1999

This paper develops a 3 DOF vehicle model which includes lateral, roll and yaw motion to study a 4WS vehicle. The model is used for the simulation of a 4WS vehicle behavior, and to derive a control algorithm for rear wheel steering. This paper uses a feedforward plus feedback control scheme to compute a rear wheel steering angle. The feedforward control scheme for computing the first rear wheel steering angle uses a gain which is acquired by multiplying a proper value on a gain to maintain a zero sideslip angle. The feedback control scheme for computing the second rear wheel steering angle uses fuzzy logic and model following control scheme. A linear 2 DOF model is used as a reference model for model following control, and is derived from the developed 3 DOF model by neglecting sprung mass roll motion. A reference state variable is yaw rate, and is computed using the linear 2 DOF model. J-turn and lane change maneuver simulation are performed to show the effectiveness of the developed control scheme. The simulation results show that the 4WS vehicle with the developed control scheme has much better performance in yaw rate, lateral acceleration, roll angle, and sideslip angle than the 2WS vehicle. Also, the results show that the performance of the developed control is close to the one of an optimal control which assumes all states are perfect.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.5
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• pp.349-359
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• 2022

The aim of this study is to analyze the dynamic characteristics of proportional control valves according to various working conditions as a basic study for developing proportional control valves for auto-steering tractors. The dynamic characteristics of proportional valves were measured using hydraulic characteristics measurement system, and the power was analyzed using measured flow rate and pressure data. As the experimental conditions, the tractor engine speed and steering angle was selected as the main variables, and the experiment was performed on urethane road conditions. As a result, it was found that the flow rate, pressure, and power of the proportional control valve increased as the tractor engine speed and steering angle increased. In particular, as the steering angle increased at the same engine speed, the flow rate, pressure, and power tended to increase by up to 190%, 172%, and 273%, respectively. Similarly, as the engine speed increased at the same steering angle, the flow rate, pressure, and power tended to increase up to 161%, 122%, and 168%, respectively. Therefore, it can be seen that the steering angle has a higher influence on the dynamic characteristics of the proportional control valve than the engine speed.