• 제어로봇시스템학회논문지
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• 제21권4호
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• pp.372-377
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• 2015

In this paper, the consideration factors that affect the actual driving of a rover wheel was examined based on the wheel-terrain model. For the evaluation of driving performance in a real environment, the test bed of the rover wheel consists of the driving part of the wheel and sensing part of the various parameters was designed and assembled. Using the test bed, the preliminary driving experiment concerning the slip ratio, sinkage, and friction force according to the rotational velocity and the shape of the wheel were carried out and evaluated. The wheel test bed and the experiment results are expected to contribute to finding the optimal result in the designing of the wheel shape and the planning of the driving conditions through further study.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1801-1812
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• 2006

In this paper, a 4-wheel vehicle model including the effects of tire slip was considered, along with variable parameter sliding control, pushrod force as the end control parameter, and an antilock sliding control, in order to improve the performance of the vehicle longitudinal response. The variable sliding parameter is made to be proportional to the square root of the pressure derivative at the wheel, in order to compensate for large pressure changes in the brake cylinder. A typical tire force-relative slip curve for dry road conditions was used to generate an analytical tire force-relative slip function, and an antilock sliding control process based on the analytical tire force-relative slip function was used. A retrofitted brake system, with the pushrod force as the end control parameter, was employed, and an average decay function was used to suppress the simulation oscillations. Simulation results indicate that the velocity and spacing errors were slightly larger than the results that without considering wheel slip effect, the spacing errors of the lead and follower were insensitive to the adhesion coefficient up to the critical wheel slip value, and the limit for the antilock control on non-constant adhesion road condition was determined by the minimum of the equivalent adhesion coefficient.

• 한국자동차공학회논문집
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• 제14권5호
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• pp.17-24
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• 2006

Anti-lock brake system(ABS) are designed to prevent wheel lock on all wheels of the vehicle by sensing wheel angular speed, processing the speed sensor signals in suitable digital electronic control circuits and comanding electrohydraulic actuators to control brake pressure. This study considers a control of ABS using wheel circumferential acceleration thresholds which avoids dangerous wheel locking due to excessive brake pressure during the vehicle braking and discusses the 3-channels, 3-sensors ABS system that employs "independent control" technique for the front wheels and "select low" technique for the rear wheels. The validities of the ABS such as vehicle stability, steerability and stopping distance during braking are assured through the vehicle tests on uniform asphalt straight roads.

• 제어로봇시스템학회논문지
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• 제14권10호
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• pp.1062-1072
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• 2008

When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the traversabilities, wheel-terrain maximum friction coefficient can indicate the index to control wheel-terrain traction force or whether mobile robots to go or not. This paper proposes estimating wheel-terrain maximum friction coefficient. The existing method to estimate the maximum friction coefficient is limited in flat terrain or relatively easy driving knowing wheel absolute velocity. But this algorithm is applicable in rough terrain where a lot of slip occurred not knowing wheel absolute velocity. This algorithm applies the tire-friction model to each wheel to express the behavior of wheel friction and classifies slip-friction characteristic into 3 major cases. In each case, the specific algorithm to estimate the maximum friction coefficient is applied. To test the proposed algorithm's feasibility, test bed(ROBHAZ-6WHEEL) simulations are performed. And then the experiment to estimate the maximum friction coefficient of the test bed is performed. To compare the estimated value with the real, we measure the real maximum friction coefficient. As a result of the experiment, the proposed algorithm has high accuracy in estimating the maximum friction coefficient.

• 한국철도학회논문집
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• 제11권2호
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• pp.203-210
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• 2008

바퀴와 BLDC전동기 일체형으로 구성되는 Hub Wheel 전동기는 감속기가 없는 직접 구동방식으로서 저소음 고효율의 운전이 가능하여 경전철의 구동부로 활용이 가능하다. 하지만 Hub Wheel 전동기는 속도계측을 위한 센서의 장착이 용이하지 않다. 전동기의 원활한 속도 제어를 위해서는 별도의 속도 계측을 위한 방법이 요구된다. 본 논문에서 입력이 적극 반영된 간단한 수학적 시스템 모델을 가지고 이산 칼만 필터를 사용하여 전동기 속도를 추정하고 이를 이용하여 속도제어를 하는 방법을 제시한다.

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.3-6
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• 2008

Electrolytic in-process dressing (ELID) grinding is a new technique for achieving a nanoscale surface finish on hard and brittle materials such as optical glass and ceramics. This process applies an electrochemical dressing on the metal-bonded diamond wheels to ensure constant protrusion of sharp cutting grits throughout the grinding cycle. In conventional ELID grinding, a constant source of pulsed DC power is supplied to the ELID cell, but a feedback mechanism is necessary to control the dressing power and obtain better performance. In this study, we propose a new closed-loop wheel dressing technique for grinding wheel truing that addresses the efficient correction of eccentric wheel rotation and the nonuniformity in the grinding wheel profile. The technique relies on an iterative control algorithm for the ELID power supply. An inductive sensor is used to measure the wheel profile based on the gap between the sensor head and wheel edge, and this is used as the feedback signal to control the pulse width of the power supply. We discuss the detailed mathematical design of the control algorithm and provide simulation results that were confirmed experimentally.

• 제어로봇시스템학회논문지
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• 제17권4호
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• pp.313-320
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• 2011

Multi-axle driving vehicles that are used in special environments require high driving performance, steering performance, and stability. Among these vehicles, 6WS/6WD vehicles with middle wheels have structural safety by distributing the load and reducing the pitch angle during rapid acceleration and braking. 6WS/6WD vehicles are favored for military use in off road operations because of their high maneuverability and mobility on extreme terrains and obstacles. 6WD vehicles that using in-wheel motor can generate the independent wheel torque without other mechanical parts. Conventional vehicles, however, cannot generate an opposite driving force at each side wheel. Using an independent steering and driving system, six-wheel vehicles can show better performance than conventional vehicles. Using of independent steering and driving system, the 6 wheel vehicle can improve a performance better than conventional vehicle. This vehicle enhances the maneuverability under low speed and the stability at high speed. This paper describes an independent 6WS/6WD vehicle, consists of three parts; Vehicle Model, Control Algorithm for 6WS/6WD and Simulation. First, vehicle model is application of TruckSim software for 6WS and 6WD. Second, control algorithm describes the optimum tire force distribution method in view of energy saving. Last is simulation and verification.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.11-17
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• 2015

Recently, the in-wheel motor vehicle is rapidly developed to solve energy exhaustion and environmental problems. Especially, it has the advantage of independently driving the torque control of each wheel in the vehicle. However, due to the weight increase of wheel, the comfort of vehicle riding and performance of road holding become worse. In this paper, to compensate the poor performance, a simultaneous control of the driving torque and semi-active suspension system is investigated. A vehicle model is generated using CarSim Software and validated by field tests. Co-simulation of CarSim and MATLAB/Simulink with control logics is carried out, and it is found that simultaneous control of the driving torque and semi-active suspension system can improve driving stability and durability of the in-wheel motor system.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.102-109
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• 2005

Wheel-slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS systems. But, in order to achieve the superior braking performance through the wheel-slip control, real-time information such as the tire braking force is required. For example, in the case of EHB (Electro-Hydraulic Brake) systems, the tire braking force cannot be measured directly, but can be approximated based on the characteristics of the brake disk-pad friction. The friction characteristics can change significantly depending on aging of the brake, moisture on the contact area, heat etc. In this paper, a wheel slip The proposed wheel slip control system is composed of two subsystems: braking force monitor and robust slip controller In the brake force monitor subsystem, the tire braking forces as well as the brake disk-pad friction coefficient are estimated considering the friction variation between the brake pad and disk. The robust wheel slip control subsystem is designed based on sliding mode control methods and follows the target wheel-slip using the estimated tire braking forces. The proposed sliding mode controller is robust to the uncertainties in estimating the braking force and brake disk-pad friction. The performance of the proposed wheel-slip control system is evaluated in various simulations.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.357-360
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• 1997

This paper presents a new anti-lock brake system(ABS) using electro-rheological(ER) valve actuators for the wheel slip control. The hydraulic dynamic model of the automotive brake system is formulated by incorporating electric field-dependent Bingham properties of ER fluid obtained experimentally. The brake system designed by this hydraulic model is able to control wheel slip by controlling the intensity of electric field which tunes the braking torque. The control fields of the ER valve to command desired wheel slip are determined by a sliding mode controller. A comparison between the proposed brake system and the conventional brake system is made by providing with computer simulations of vehicle motions under ABS performance requirement condition.