• International Journal of Fuzzy Logic and Intelligent Systems
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• 제4권2호
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• pp.182-186
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• 2004

This paper describes an advanced compensation for non-linear functions designed to remove steering aberrations from phased array antennas. This system alters the steering command applied to the antenna in a way that the appropriate angle commands are given to the array steering software for the antenna to point to the desired position instead of squinting. Artificial neural networks are used to develop the inverse function necessary to correct the aberration. Also a straightforward antenna steering function is implemented with neural networks for the 9-term polynomials of forward steering function. In all cases the aberration is removed resulting in small RMS angular errors across the operational angle space when the actual antenna position is compared with the desired position. The use of neural network model provides a method of producing a non-linear system that can correct antenna performance and demonstrates the feasibility of generating an inverse steering algorithm.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.937-943
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• 2017

To design an automatic steering controller with high performance for autonomous vehicle, it is necessary to have a precise model of the lateral dynamics with respect to the steering command input. This paper presents an empirical modeling of the steering system for an autonomous vehicle. The steering system here is represented by three individual transfer function models: a steering wheel actuator model from the steering command input to the steering angle of the shaft, a dynamic model between the steering angle and the yaw rate of the vehicle, and a dynamic model between the steering command and the lateral deviation of vehicle. These models are identified using frequency response data. Experiments were performed using a real vehicle. It is shown that the resulting identified models have been well fitted to the experimental data.

• 한국자동차공학회논문집
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• 제8권4호
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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.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.138-147
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• 2000

Vehicle suspension systems are parts which effect performances of a vehicle such as ride quality, handing characteristics, straight performance and steering effort etc. Kinematic design is a decision of joints` position for straight performance and steering effort. But, when vehicle is rebounding and bumping, chang of joints` displacement is nonlinear and a surmise of straight performance and steering effort at that joints` position is difficult. So design of suspension systems is done through a inefficient method of tried-and-error depending on designer`s experience. In this paper, kinematic design of suspension systems was done through the optimal design using a genetic algorithm. For this optimal design, the function for quantification of straight performance and steering effort was made, and the kinematic design method of suspension systems having this function as the objective function was suggested.

• 컴퓨터교육학회논문지
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• 제6권3호
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• pp.47-56
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• 2003

We describe a new method for removing non-linear phased array antenna aberration called "squint" problem. To develop a compensation scheme. theoretical antenna and artificial neural networks were used. The purpose of using the artificial neural networks is to develop an antenna system model that represents the steering function of an actual array. The artificial neural networks are also used to implement an inverse model which when concatenated with the antenna or antenna model will correct the "squint" problem. Combining the actual steering function and the inverse model contained in the artificial neural network, alters the steering command to the antenna so that the antenna will point to the desired position instead of squinting. The use of an artificial neural network provides a method of producing a non-linear system that can correct antenna performance. This paper demonstrates the feasibility of generating an inverse steering algorithm with artificial neural networks.

• 한국군사과학기술학회지
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• 제11권4호
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• pp.92-98
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• 2008

A beam steering system of X-band 2-D phased array antenna for radar application is developed. The beam steering system consists of real-time command generator, beam steering unit, control PCB of array module and power supply. It plays a role of beam steering and on-line check of phased array antenna. The performance of beam steering system is verified with pulse timing of current control in phase shifters and measurement of far-field of phased array antenna. The developed beam steering system offers basic technology to develop full-scale beam steering system of multi-function radar.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.201-206
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• 2000

In this work transfer function synthesis method based on FRF data of each substructure is investigated for a complex structure composed of many substructures. Though the transfer function synthesis method has superiority to analyze the characteristics of interfaces among substructures effectively, many problems arise in the computation process, especially matrix inversion process. Due to computational problems, the error between the data obtained by test and the predictions through computations is inevitable. So in this paper, computational aspects in the transfer function synthesis method are examined through a steering system problem of passenger car. For the FBS method, frequency response functions of 3 substructures are measured experimentally. Effects of several parameters such as matrix inversion method, connection conditions between substructures and off-diagonal terms on system response are studied numerically.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.59-67
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• 2014

A numerical model and a controller of Active Front wheel Steer (AFS) system are designed in this study. The AFS model consists of four sub models, and the AFS controller uses sliding mode control and PID control methods. To test this model and controller an Integrated Dynamics Control with Steering (IDCS) system is also designed. The IDCS system integrates an AFS system and an ARS (Active Rear wheel Steering) system. The AFS controller and IDCS controller are compared under several driving and road conditions. An 8 degree of freedom vehicle model is also employed to test the controllers. The results show that the model of AFS system shows good kinematic steering assistance function. Steering ratio varies depends on vehicle velocity between 12 and 24. Kinematic stabilization function also shows good performance because yaw rate of AFS vehicle tracks the reference yaw rate. IDCS shows improved responses compared to AFS because body side slip angle is also reduced. This result also proves that AFS system shows satisfactory result when it is integrated with another chassis system. On a split-m road, two controllers forced the vehicle to proceed straight ahead.

• 수산해양기술연구
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• 제59권1호
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• pp.44-54
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• 2023

In this study, the second-order Nomoto's nonlinear expansion model was implemented as a Tagaki-Sugeno fuzzy model based on the heading angular velocity to design the automatic steering system of a ship considering nonlinear elements. A Tagaki-Sugeno fuzzy PID controller was designed using the applied fuzzy membership functions from the Tagaki-Sugeno fuzzy model. The linear models and fuzzy membership functions of each operating point of a given nonlinear expansion model were simultaneously tuned using a genetic algorithm. It was confirmed that the implemented Tagaki-Sugeno fuzzy model could accurately describe the given nonlinear expansion model through the Zig-Zag experiment. The optimal parameters of the sub-PID controller for each operating point of the Tagaki-Sugeno fuzzy model were searched using a genetic algorithm. The evaluation function for searching the optimal parameters considered the route extension due to course deviation and the resistance component of the ship by steering. By adding a penalty function to the evaluation function, the performance of the automatic steering system of the ship could be evaluated to track the set course without overshooting when changing the course. It was confirmed that the sub-PID controller for each operating point followed the set course to minimize the evaluation function without overshoot when changing the course. The outputs of the tuned sub-PID controllers were combined in a weighted average method using the membership functions of the Tagaki-Sugeno fuzzy model. The proposed Tagaki-Sugeno fuzzy PID controller was applied to the second-order Nomoto's nonlinear expansion model. As a result of examining the transient response characteristics for the set course change, it was confirmed that the set course tracking was satisfactorily performed.

• 산업기술연구
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• 제18권
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• pp.241-248
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• 1998

In this study, a modeling method of power-assisted steering systems and driver models for vehicle dynamic analysis using AUTODYN7 is presented. Pressure-flow relations of flow control valve are derived, and the equations of motion of a steering gear are obtained. Combining pressure-flow relations and equations of motion, the steering force can be represented as a function of steering wheel angle or torque. Driver model was modeled based on a PID controller and forward target method. With the steering systems and driver model, various driving tests are conducted using AUTODYN7.