• Safety and Health at Work
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• 제9권1호
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• pp.17-24
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• 2018

Background: Increasing the slip resistance of floor surfaces would be desirable, but there is a lack of evidence on whether traction properties are linearly correlated with the topographic features of the floor surfaces or what scales of surface roughness are required to effectively control the slipperiness of floors. Objective: This study expands on earlier findings on the effects of floor surface finishes against slip resistance performance and determines the operative ranges of floor surface roughness for optimal slip resistance controls under different risk levels of walking environments. Methods: Dynamic friction tests were conducted among three shoes and nine floor specimens under wet and oily environments and compared with a soapy environment. Results: The test results showed the significant effects of floor surface roughness on slip resistance performance against all the lubricated environments. Compared with the floor-type effect, the shoe-type effect on slip resistance performance was insignificant against the highly polluted environments. The study outcomes also indicated that the oily environment required rougher surface finishes than the wet and soapy ones in their lower boundary ranges of floor surface roughness. Conclusion: The results of this study with previous findings confirm that floor surface finishes require different levels of surface coarseness for different types of environmental conditions to effectively manage slippery walking environments. Collected data on operative ranges of floor surface roughness seem to be a valuable tool to develop practical design information and standards for floor surface finishes to efficiently prevent pedestrian fall incidents.

• Korea-Australia Rheology Journal
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• 제20권2호
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• pp.51-58
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• 2008

This paper describes a two-step Tikhonov regularization procedure for converting the steady shear data generated by parallel-disk viscometers, in the presence of wall slip, into a shear stress-shear rate function and a wall shear stress-slip velocity functions. If the material under test has a yield stress or a critical wall shear stress below which no slip is observed the method will also provide an estimate of these stresses. Amplification of measurement noise is kept under control by the introduction of two separate regularization parameters and Generalized Cross Validation is used to guide the selection of these parameters. The performance of this procedure is demonstrated by applying it to the parallel disk data of an oil-in-water emulsion, of a foam and of a mayonnaise.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.133-138
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• 1993

This paper presents neural network based position estimation method in slippery environment as an approach to solve one of problems which are engaged in dead reckoning method. Position estimator is composed of slip detector and linear velocity estimator. Both of them are based on the fact that dynamic characteristic of mobile robot in slippery environment is different from the case without slip. To find out the dynamic relation among driving torque, angular acceleration of driving wheel and linear acceleration of mobile robot, accelerometer is used for measuring acceleration of mobile robot and neural network is used for dynamic system identifier in slippery environment.

• 한국산학기술학회논문지
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• 제7권6호
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• pp.1064-1071
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• 2006

본 논문에서는 최대 견인력 제어를 위해서 부하토크외란관측기와 속도센서리스 벡터제어를 이용하여 점착력 계수를 추정하고 추정한 점착력 계수의 미분치를 PI 토크 제어하는 Anti-slip제어를 제안한다. 점착력 계수를 추정하기 위해서는 전압, 전류값 뿐만 아니라 자속이나 속도정보가 필요하다. 따라서 전동기의 회전속도를 정확하게 검출할 수 있는 속도센서가 필요하게 된다. 그러나 속도검출을 위해 속도센서를 부착하는 것은 여러 가지 면에서 단점을 가지고 있다. 이러한 문제점을 해결하기 위하여 속도센서 없는 센서리스 구동방식에 의한 부하토크외란관측기를 설계하여, 점착력 계수를 추정한다. 이와 같은 제어 알고리즘을 구현하기 위하여 1C1M 철도모의장치를 이용하여 제안된 알고리즘을 실험을 통하여 확인하였다.

• 한국정밀공학회지
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• 제20권7호
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• pp.84-90
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• 2003

This paper develops a control method that is composed of the proportional control algorithm and the learning algorithm based on the recurrent neural networks (RNN) for the position control of a pneumatic rodless cylinder. The proportional control algorithm is suggested for the modeled pneumatic system, which is obtained easily simplifying the system, and the RNN is suggested for the compensation of the modeling errors and uncertainties of the pneumatic system. In the proportional control, two zones are suggested in the phase plane. One is the transient zone for the smooth tracking and the other is the small movement zone for the accurate position control with eliminating the stick-slip phenomenon. The RNN is connected in parallel with the proportional control for the compensation of modeling errors and frictions, compressibilities, and parameter uncertainties in the pneumatic control system. This paper experimentally verifies the feasibility of the proposed control algorithm for such pneumatic systems.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.19-27
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• 2017

In this paper, a simulator hardware and control design for an electronic parking brake (EPB) are proposed for emergency vehicle braking when the hydraulic break and anti-lock brake systems (ABS) fail to function. EPB systems are designed specifically for park braking and are usually installed on the rear wheels. However, in an emergency situation when all vehicle brake systems fail, the EPB can be utilized to stop the vehicle and track the target slip ratio as the ABS. This paper analyzed the non-linear EBP of the type of motor on caliper (MoC) based on experiments. A simulator hardware is also designed to validate the performance of the designed EPB controller in terms of braking distance and performance in tracking the target slip ratio. Through the experimental analysis, it is confirmed that a sliding mode controller can be applied on a non-linear EPB to track the target slip ratio.

• 대한기계학회논문집A
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• 제28권8호
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• pp.1203-1211
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• 2004

A traction control systems (TCSs) composed of either a wheel slip controller or a throttle valve controller or an integrated controller of both systems are proposed in this study. To validatethe dynamic characteristics of a vehicle and TCS, a full car model that can simulate the responses of both front wheel drive (2WD) and four wheel drive (4WD) vehicle is also developed. The wheel slip controller uses a sliding mode control scheme and the throttle valve is controlled by a PID controller. The results shows that tHe brake TCS and the engine TCS achieve rapid acceleration, and reduce slip angle on slippery road. When a vehicle is cornering and accelerating maneuver with the brake or engine TCS, understeer or oversteer occur, depending on the driving conditions. The integrated TCS prevents most of these problems and improves the stability and controllability of the vehicle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.285-287
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• 1995

In the case of driving the SLIM(Single-sided Linear Induction Motor) as the VVVF inverter, the performance of SLIM, which is a thrust, normal force and so on, varies according to a slip frequency as a function of the external load. It is impossible that the open-loop control method control the speed of a SLIM accurately. So that, this paper is proposed the speed control method of a SLIM for a automatic conveyor system with the slip frequency vector control method. To analyze the dynamic characteristics of a SLIM, the state equation is derived from the equivalent circuit of the SLIM, ignored the end effect. The slip frequency and the normal force of SLIM are constantly controlled at the steady state. The simulated results is compared with the experimental values.

• 한국정밀공학회지
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• 제18권7호
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• pp.40-45
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• 2001

This paper proposes a methodology for the small-displacement-movement of a piston and develops a hybrid control algorithm for the precision position control of a pneumatic rodless cylinder. The pneumatic system uses the voltage-proportional solenoid valves to minimum valve switching since the on/off type valves are create diffculties for accurate position control and induce a lot of valve switching. For the accurate position control a methodology for the small-displacement-movement of the piston is developed and identified experimentally. The main consideration on the development of the hybrid control law is to eliminate a stick-slip phenomenon in the pneumatic control system. This paper addresses these critical issues and presents experimental results for the pneumatic control system.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.195-201
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• 2005

In conventional Vehicle Stability Control (VSC) System, a control threshold is designed by average driver characteristics. Despite the stabilizing effort, VSC causes redundancy to an expert driver. An advanced VSC which has flexibility on its control property is proposed in this study. By using lateral velocity estimator, a control threshold is determined on side slip angle and angular velocity phase plane. Vehicle planar motion model based sliding controller is modified with respect to various control thresholds. The performance of the proposed VSC algorithm has been investigated by human-in-the-loop simulation using a vehicle simulator. The simulation results show that the control threshold has to be determined with respect to the driver steering characteristics. A VSC with variable control thresholds would provide an improvement compared to a VSC with a constant threshold.