주행로봇 제어를 위한 험지의 최대마찰계수 추정

강현석(Hyun-Suk Kang),곽윤근(Yoon Keun Kwak),최현도(Hyun-Do Choi),정해관(Hae-Kwan Jeong),김수현(Soo-Hyun Kim) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.10

When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the travers abilities, 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.

Tribology Characteristics in 300 μm of Hexagonal Array Dimple Pattern

H. J. Choi,A. S. Hermanto,S. H. Kwon,S. G. Kwon,J. M. Park,J. S. Kim,S. W. Chung,Y. H. Chae,W. S. Choi 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.6

In the tribological performance of materials, a textured surface reduces the friction coefficient and wear. This study investigates the effects of a pattern of 300 μm dimples in a hexagonal array on the tribological characteristics. Previous studies investigated 200 μm dimples by using a similar material and method. There are three frictional conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction. In this experiment, we investigated the frictional characteristics by conducting frictional tests at sliding speeds ranging from 9.6 rpm to 143.3 rpm and a normal load ranging from 13.6 N to 92 N. We used a photolithography method to create dimples for surface texturing. We used five specimens with different dimple densities 10%, 15%, 20%, 25%, and 30% in this study. The dimple density on the surface area is one of the important factors affecting the friction characteristics. The duty number graph indicates a fully developed fluid friction regime. Fluid friction occurs at a velocity of 28.7-143.3 rpm. We observed the best performance at a dimple density of 10% and a dimple diameter of 300 μm in the hexagonal array, the lowest friction coefficient at 0.0037 with 9.6 rpm 9.6N load, and the maximum friction coefficient at 0.0267 with 143.3 rpm 92N load.

Real-Time In Situ Microscopic Observation of Dynamic Contact and Friction Between a Wire Rope and Friction Lining

Yongbo Guo,Zheyingzi Zhu,Dekun Zhang,Kai Chen,Songquan Wang 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.3

An experiment was conducted using a microslip friction test machine to measure reciprocating sliding friction between a K25 friction lining and a 6 × 19 steel wire rope under dynamic loading. Real-time in situ microscopic observation of the interfacial friction in the contact were performed by using a high-speed micro camera. The results showed that during the loading and unloading stages of friction, adhesion, partial adhesion and slip states were observed. The friction coefficient decreases with increasing dynamic load. In the lightly loaded area (3kN-10kN), the variation of the friction coefficient in the sliding stage was stable. In the heavily loaded area (3kN-14kN), the friction coefficient in the slip stage decreased with increasing load, and the proportion of the slip stage in the loading time increased. The wear debris generated at the interface of the contact increased gradually with increasing dynamic load. Then, a dense third body formed, which reduced the friction coefficient. The wear rate of the lining under these experimental conditions was 3.23 × 10–4 after 18 h.

Estimation of the Road Friction Coefficient Using a Particle Filter

Do Ui Hong,ChanHo Park,GiSung Gwak,Sung-Ho Hwang 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-

In vehicle driving safety, the friction coefficient is the important factor in deciding braking distance. The road friction coefficient manifests non-Gaussian states. In this paper, we use a particle filter, which is a simulation-based approach and which approximates the posterior Probability Density Function (PDF), to estimate the road friction coefficient. We derive the equation of the friction coefficient from the Free Body Diagram (FBD) of the vehicle. Using this equation, we find the μ-slip curve for each different road condition. Through the μ-slip curve, we can determine the road friction coefficient by interpolation. We perform the simulation by Carsim, and the result shows that the particle filter tracks the friction coefficient more accurately than before.

마찰계수의 비접촉 추정을 위한 영상정보 활용방법

김두규(Doo-gyu Kim),김자영(Ja-young Kim),이지홍(Jihong Lee),최동걸(Dong-Geol Choi),권인소(In-So Kweon) 大韓電子工學會 2010 電子工學會論文誌-SP (Signal processing) Vol.47 No.4

본 논문에서는 마찰계수의 비접촉 추정을 위한 영상정보 활용방법을 제안한다. 마찰계수는 이동체의 도로주행 또는 장애물 극복에 있어 매우 중요한 요소이다. 이동체가 이동경로의 마찰계수를 미리 알 수 있다면 이동성향상을 기대할 수 있다. 본 논문의 마찰계수 추정방법은 영상정보를 활용하기 때문에 이동체가 지면과 접촉하기 전에 마찰계수를 추정 할 수 있다는 장점이 있다. 마찰계수의 비접촉 추정을 위한 영상정보 활용방법은 마찰계수측정실험과 물질그룹생성을 포함한 학습단계와 물질그룹 분류과정과 마찰계수 함수 활용을 포함한 마찰계수 추정단계로 구성되어 있으며 물질 조성비를 생성하는 영상처리는 두 단계에 모두 포함된다. 이 과정을 통해 얻은 마찰계수는 무인이동로봇이 이동경로 진입 전에 미끄러움을 판단하여 미끄럼지역을 회피 할 수 있도록 하며, 저속으로 이동이 가능한 경우 미끄럼이 발생하지 않는 적정속도를 계산하는데 확용 가능하다. 본 논문에서 사용한 지형의 마찰계수와 영상정보는 마찰계수 측정실험을 통해 취득하였다. 마찰계수 추정방법을 평가하기 위해 실험지형의 실제 마찰계수와 추정 마찰계수의 차이를 비교하였다. In this paper, we proposed an algorithm for utilizing visual information for non-contact predicting method of friction coefficient. Coefficient of friction is very important in driving on road and traversing over obstacle. Our algorithm is based on terrain classification for visual image. The proposed method, non-contacting approach, has advantage over other methods that extract material characteristic of road by sensors contacting road surface. This method is composed of learning group(experiment, grouping material) and predicting friction coefficient group(Bayesian classification .prediction function). Every group include previous work of vision. Advantage of our algorithm before entering such terrain can be very useful for avoiding slippery areas. We make experiment on measurement of friction coefficient of terrain. This result is utilized real friction coefficient as prediction method. We show error between real friction coefficient and predicted friction coefficient for performance evaluation of our algorithm.

Tribology Characteristics in 300 μm of Hexagonal Array Dimple Pattern

최혜진,권순홍,권순구,박종민,김종순,정성원,채영훈,최원식 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.6

In the tribological performance of materials, a textured surface reduces the friction coefficient and wear. This study investigates the effects of a pattern of 300 μm dimples in a hexagonal array on the tribological characteristics. Previous studies investigated 200 μm dimples by using a similar material and method. There are three frictional conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction. In this experiment, we investigated the frictional characteristics by conducting frictional tests at sliding speeds ranging from 9.6 rpm to 143.3 rpm and a normal load ranging from 13.6 N to 92 N. We used a photolithography method to create dimples for surface texturing. We used five specimens with different dimple densities 10%, 15%, 20%, 25%, and 30% in this study. The dimple density on the surface area is one of the important factors affecting the friction characteristics. The duty number graph indicates a fully developed fluid friction regime. Fluid friction occurs at a velocity of 28.7-143.3 rpm. We observed the best performance at a dimple density of 10% and a dimple diameter of 300 μm in the hexagonal array, the lowest friction coefficient at 0.0037 with 9.6 rpm 9.6N load, and the maximum friction coefficient at 0.0267 with 143.3 rpm 92N load.

Tribology Characteristics in 300 μm of Hexagonal Array Dimple Pattern

Choi, H. J.,Hermanto, A. S.,Kwon, S. H.,Kwon, S. G.,Park, J. M.,Kim, J. S.,Chung, S. W.,Chae, Y. H.,Choi, W. S. Korean Tribology Society 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.4 No.1

In the tribological performance of materials, a textured surface reduces the friction coefficient and wear. This study investigates the effects of a pattern of 300 µm dimples in a hexagonal array on the tribological characteristics. Previous studies investigated 200 µm dimples by using a similar material and method. There are three frictional conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction. In this experiment, we investigated the frictional characteristics by conducting frictional tests at sliding speeds ranging from 9.6 rpm to 143.3 rpm and a normal load ranging from 13.6 N to 92 N. We used a photolithography method to create dimples for surface texturing. We used five specimens with different dimple densities 10%, 15%, 20%, 25%, and 30% in this study. The dimple density on the surface area is one of the important factors affecting the friction characteristics. The duty number graph indicates a fully developed fluid friction regime. Fluid friction occurs at a velocity of 28.7-143.3 rpm. We observed the best performance at a dimple density of 10% and a dimple diameter of 300 µm in the hexagonal array, the lowest friction coefficient at 0.0037 with 9.6 rpm 9.6N load, and the maximum friction coefficient at 0.0267 with 143.3 rpm 92N load.

클러치용 Friction Bushing 마찰재의 미끄럼마찰특성에 관한 연구

이한영(Han-Young Lee),조범래(Bum-Rae Cho),허대홍(Dae-Hong Hur),김태준(Tae-Jun Kim),조용재(Yong-Jae Cho),허만대(Man-Dae Hur) 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.6

In order to investigate the wear properties of the friction bushing materials for clutch system of automobile. plate-on-disc type wear test have been conducted for three different types of composites reinforced by grass fiber. mineral fiber and mullite at several test conditions. In this paper. the friction properties of three different types of composites have been analyzed. Grass fiber reinforced composite exhibits lower friction coefficient, even though it maintains the friction coefficient stably under all test condition. It aseems to be due to the lubricity of grass fiber. On the contrary, the friction coefficient of mineral fiber reinforced composite exhibits unstable even though it shows high friction coefficient. The friction coefficient of mullite reinforced composite lies between these of grass fiber and mineral fiber reinforced composite. However deviation and amplitude of friction coefficient at a high temperature of 100℃ increases due to the formation of composite film transferred on counter surface.

MEASUREMENT OF THE DISC-PAD FRICTION COEFFICIENT FOR MECHANICAL BRAKES USING DIRECT AND INDIRECT METHODS

김영국,김석원,박찬경,박태원,김영모 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.1

It is necessary to guarantee the proper brake force to stop a train safely in a limited distance and o adjust its speed. Currently, most trains are run by electrical power and have a combined electrical and mechanical (friction) braking system. The mechanical brake force is determined by many parameters, such as the friction coefficient of the brake disc and pad, the pressure in the brake cylinder, the brake cylinder’s cross sectional area and the brake linkage ratio. In general, the friction coefficient data of the brake disc and pad have been taken through a dynamo-test in a laboratory, but these data might not be well matched with real data under operating conditions because of the difference in data acquisition conditions. The present study examined two methodologies that can measure the friction coefficient of the brake pad and disc based on a train’s real operating conditions. The first method was the direct method, which measured the brake force and clamping force applied on the mechanical brake by using strain gauges installed on the brake to calculate the friction coefficient. The second was an indirect method that obtained the friction coefficient by using the weight of the train and the equivalent brake force. Those variables were calculated from the longitudinal dynamic characteristics, such as resistance to motion, gradient resistance and curved resistance. These two methodologies were used to obtain the disc-pad friction coefficient for the mechanical brakes of a Korean high-speed train (HSR350x).

디스크 브레이크의 제동마찰 및 마멸특성에 관한 실험적 연구

김청균(Chung Kyun Kim),이병관(Boung Kwan Lee),김한구(Han Goo Kim) 한국트라이볼로지학회 2006 한국윤활학회지(윤활학회지) Vol.22 No.3

This paper presents the braking friction and wears on the rubbing surfaces of a friction pad-disk brake. In this study, four friction disk specimens are sampled from unused and used disks in which are taken from the disk brake system when the friction induced vibration and noise problems have been occurred during a braking period at a running period of 10,000 ㎞, 20,000 ㎞, and 30,000 ㎞ in random. The experimental results indicate that the tribological characteristics of an unused disk brake shows equal and stable as a friction coefficient and temperature distributions during a braking friction/wear test period including a total friction mode from the start to running periods. But the used disk brake shows unstable and uneven friction modes between an outside and inside rubbing surfaces of a disk brake in terms of a friction coefficient and wears. This may lead to a friction induced friction vibration and noise problems of a used disk brake.