• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.100-111
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• 1999

This paper resents a discrete-time model of an edge-following with accommodation force control. Since an irregular workpiece shape causes disturbances to the system while following an edge, the use of preview control is proposed to improve the system performance. The preview control employs future information of the workpiece contour shape, and it can be developed by LQ-optimal control principles. This study provides a general method how to utilize the local future information obtained by the finite preview to minimize an optimality criterion evaluated over a problem duration. The force controller is designed based on the preview control scheme, and then implemented on a VME-based computer. Experimental results using an industrial robot show that the preview control system achieves faster tracking speed and better force regulation than the conventional nonpreview control system.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.892-895
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• 1996

An unknown input observer is proposed that can be used in wheelbase preview control of commercial vehicles. The preview and state information, required to calculate actuator force, are reconstructed from the measurement variables such as heave and pitch acceleration. Gain matrix of observer is optimally selected so that influence of system and measurement noises on the estimation error can be minimized. Estimated preview information requires low pass filtering to eliminate high frequency components resulting from differentiation of noisy output signals. Effectiveness of the proposed method is demonstrated by numerical simulation of half car model.

• Journal of the Korean Society of Safety
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• v.32 no.1
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• pp.1-8
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• 2017

In industry AGV's(automated guided vehicles) that can detect and follow guidelines drawn on the factory floor using magnetic or optical sensors are widely used. However, such AGV's without preview capability cannot effectively avoid collision with obstacles that may occasionally pass through the guideline. Furthermore, without preview information, they consume much energy at the right angle corners as they have to make sudden directional change. Also, the risk of dropping payloads increases in such situations. In this study, infrared preview sensors were adopted to a mobile robot for detecting not only the current position but also the forward position of the guideline and the preview control technique was applied to optimally control the mobile robot's motion using the information from the infrared preview sensors. Then the effectiveness of this approach was investigated through a series of experiments. The experimental result shows that the proposed approach is effective for safety enhancement as well as for better efficiency.

• International Journal of Automotive Technology
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• v.7 no.4
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• pp.469-475
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• 2006

In this paper, an optimal suspension system with preview of the road input is synthesized for a half tracked vehicle. The main goal of this research is to improve the ride comfort characteristics of a fast moving tracked vehicle in order to maintain the driver's driving capability. Several different kinds of preview control algorithms are evaluated with active or semi-active suspension systems. The road information estimated from the motion of the 1st road-wheel is adequate to make the best use of the preview control algorithm for tracked vehicles. The ride-comfort characteristics of the tracked vehicle are more dependent on pitching angular acceleration than heaving acceleration. The pitching motion is reduced by the suspension system with hard outer suspensions and soft inner suspensions. Simulation results show that the performance of sky-hook algorithms for ride comfort nearly follow that of full state feedback algorithms.

• Journal of the Ergonomics Society of Korea
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• v.3 no.2
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• pp.3-8
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• 1984

An experimental study was made to compare digital display with analogue-digital display during a digital pursuit tracking task under the preview information. The effect of preview on performance during the tracking task was analyzed for the different preview spans and the different characteristics of the information input. The data from ten subjects revealed that the RMS error performance was improved substantially in the case of one preview point than in that of no preview. It was obtained from the result of the experiments that the improvement ratio of analogue digital to digital display increased to 48%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.115-119
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• 2007

In this paper, practical problems will be covered in applying preview control to real tracked vehicle systems. Previous researches about the preview control assume that the vehicle speed is constant and the actuators have full frequency bandwidth. However, in order to apply it to real systems, those should be taken into account. Therefore this paper show the algorithm to apply the preview control to speed changing vehicles and performance variation according to a restricted frequency bandwidth.

• Korean Journal of Cognitive Science
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• v.31 no.4
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• pp.103-136
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• 2020

This study compares the parafovea preview effect of adolescent group and adult group with different ages using eye tracking experiment. Also, this study confirms that the starting point parameter of the one boundary diffusion model can explain the data obtained through eye tracking experiments. In two experiments, parafoveal information processing was examined using the boundary technique. In Experiment 1, reading times were compared between the conditions given high frequency words preview versus masking preview. In Experiment 2, the condition in which low frequency words were given to parafovea preview information and the condition in which parafovea preview was masked were compared. We found that both the adolescent group and the adult group showed a parafovea preview effect. Also, first fixation, single fixation, and gaze duration of the two groups were different based on the word property shown in the parafovea. The first fixation data obtained in the two experiments were divided into quantiles and fitted into one boundary diffusion model. From the results, we argue that the parafovea preview information processing in the reading was described as the starting point parameter of the one boundary diffusion model.

• Korean Journal of Cognitive Science
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• v.31 no.2
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• pp.25-54
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• 2020

While there is no evidence for parafoveal processing in alphabetic languages such as English and Finnish, there is some evidence that morphological information is processed in syllabic languages like Chinese. Korean writing system, Hangul, would be able to provide morphological preview benefit effects since it is an "alphabetic syllabary" which contains both alphabetic and syllabic features. This study explored morphological parafoveal preview benefit effects during reading Korean using irregular verbs, which have phonological and orthographical differences between fundamental and conjugated forms. In the Experiment, the target word was irregular conjugated form, and there were four preview conditions: identical (e.g. 구워), fundamental form (e.g. 굽다), orthographically related (e.g. 굼다), and unrelated control (e.g. 죨어). In the result of study, identical was shortest and morphological, orthographical, unrelated preview were followed. Moreover, measures of first-pass reading of morphological preview were significantly shorter than those of unrelated control preview. This results support the hypothesis of morphological preview benefit effects in Korean. The implications of the results are discussed.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.243-249
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• 2005

To improve the ride comfort and handling characteristics of a vehicle, an active suspension which is controlled by external actuators can be used. An active suspension can control the vertical acceleration of a vehicle and the tire deflection to achieve the desired suspension goal. For this purpose, Model Predictive Control (MPC) scheme is applied with the assumption that the preview information of the oncoming road disturbance is available. The predictive control approach uses the output prediction to forecast the output over a time horizon and determines the future control over the horizon by minimizing the performance index. The developed method is applied to a half car model of four degrees-of-freedom and numerical simulations show that the MPC controller improves noticeably the ride qualities and handling performance of a vehicle.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.547-554
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• 2006

This paper is concerned with an optimal control suspension system using the preview information of road input based on a quarter car model. The main purpose of the control is to combine good vibration isolation characteristics with improved attitude control. The optimal control law is derived with the use of calculus of variation, consisting of three parts. The first part is a full state feedback term that includes integral control acting on the suspension deflection to ensure zero steady-state deflection in response to static body forces and ramp road inputs. The second part is a feed-forward term which compensates for the body forces when they can be detected, and the third part depends on previewed road input. The performance of the suspension is evaluated in terms of frequency domain characteristics and time responses to ramp road input and cornering forces. The effects of each part of the suspension controller on the system behavior are examined.