Asian Journal of Current Engineering and Maths 5:1 Janurary - February (2016) 4 – 8.
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ASIAN JOURNAL OF CURRENT ENGINEERING AND MATHS
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TERRAINABILITY OF MOBILE ROBOTS IN UNDERGROUND MINING
Anil kumar Saw #1, Atanu Maity #2
# Advanced Design and Optimization, Central Mechanical Engineering Research Institute, Durgapur, West Bengal, India
ARTICLE INFO ABSTRACT Corresponding Author Coal is conventional and cheapest source of energy and is being used as major P. Anbarsi Rodrigo energy resource in power plants, steel industries, cement industries and other Associate Professor, industries in India as well as in other coal rich countries of the world. To meet PG and Research Department of energy requirement of the industries, production of coal is increasing day by Mathematics, VOC College, day. For this reason the number of mine related accidents is also increasing. To Thoothukudi, TamilNadu increase production of coal with reduced risk, now-a-days mobile robots are India. being deployed to assist mining operations. Such robots are used for various [email protected] purposes, such as, exploration of geo-mining atmosphere, mine mapping, deployment of explosives, drilling and transportation of coal. While developing Key Words: Mobile Robot, a mobile robot for mine application, special attention has to be given to the Terrainability, Compliance, terrainability aspects as mine condition poses a serious challenge to the design Underground Coal Mine of such robot. Mobile robots cannot perform their works if they are not specially design to negotiate adverse condition of the mine floor. In this paper terrainability of mobile robots and their performance have been studied. This paper also describes one such mine robot developed by CSIR-CMERI for use in
DOI:http://dx.doi.org/10.15520/aj hostile condition of Indian coal mine environment. cem.2016.vol5.iss1.44.pp4-8. ©2015, AJCEM, All Right Reserved. INTRODUCTION India has long history and regular development in coal mining. Since 1774, the British East India Company had been commercially exploiting the underground coal reserve of Raniganj area [1]. Statistical review shows that India has fifth rank in coal production and third rank in consumption of coal in the world [2] which is further depicted in Fig. 1. Nearly fifty-five percent of the India’s total energy requirements are met from coal [3] and coal mines play an important role in the development of India. Working environment of coal mines are generally hazardous due to causes like flooding, subsidence, roof collapse, leakage of noxious gases, explosion etc. Many miners had lost their lives worldwide in coalmine related accidents. A statistical analysis of mine related casualties is shown in Fig. 2. Fig. 2. Death Tolls (World -wide) in Coal Mine Disasters A few major coal mine related accidents are listed below [4]: • Benxihu coal mine disaster (1942) of China • Courrieres coal mine disaster (1906) of France • Mitsubishi Hojyo coal-mine disaster (1914) Japan • Chasnala mine disaster (1975) of India • Bagdigi colliery accidient (2001) of India Accidents in coal mines are not only a problem for India but also for other coal rich countries. Now-a-days robots are being deployed in mines for rescue operation and to minimize such type of accidents by inspection of working environment, especially after blasting. However Fig. 1. Graph showing production of coal by top five mine environment is extremely challenging and mine countries in different year, robots are specially designed to overcome such challenges.
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There are various problems exist in coal mines which are with a passive two DOF link which make it flexible. The related to condition of floor like wet and dry floor, rocky robot is capable of navigating around tight corners due to floor, slope, step, bump, ditch, muddy and sandy land and its smaller size and compact design. Comparatively better flood etc. To overcome such mine floor hurdles thorough terrainability of Gemini-Scout is achieved due to its understanding of mine terrainability is essential and design segmented body design and tracked wheel configuration. of such robots need special attention. This paper discusses some mine robots and their terrainability, adaptive nature and performance in underground mine environment. I. UNDERGROUND MINE ROBOT
Fig. 5. Detection and Rescue Robot [7] C. Detection and Rescue Robot (DAR) It is a mine rescue robot with six-track system, which was developed by ‘School of Mecha-Electronic Engineering,’ Fig.3. Groundhog Robot in Florence Coal Mine near Beijing Institute of Technology [7]. Out of its six tracks two Pittsburgh [5] are drive tracks and two front and rear arms are used to Several mine robots have been developed so far for cross obstacles. It is designed adaptive to mine conditions various mine applications. Example of some underground by making it explosion proof, water and dust proof. The mine robots have been discussed here from the point of design claims to have better terrainability with shock view of their application and terrainability. absorption capability. It can climb slope up to 300 by A. Groundhog Mine Robot adjusting its arms and can move over rubbles. It is a mine mapping four-wheeled drive explosion- D. CMERI Subterranean Robot (SR) proof autonomous mobile robot which was developed by It is an amphibian subterranean exploring robot Carnegie Mellon University [5]. The design of its chassis developed by CSIR-CMERI and is capable of moving over and steering system is such that, it can work on very rough fairly rough terrain and also can swim as well as crawl over terrain of mine. Its chassis consists of the front halves of basin floor effortlessly due to its special system design [8], two all terrain vehicles, allowing all four of its wheels to be [9]. The Robot consists of two modular track-wheel both driven and steered. Two Ackerman steering columns arrangements and two thrusters on both of its sides. which are linked in opposition, reduces its turning radius Thrusters mounted on a single shaft make it capable of when it turns along a curve path. swimming against moderate current with 1 knot velocity. Two stabilizer fins are also mounted on same shaft to stabilize roll while in underwater operation. B. Gemini-Scout Robot Gemini-Scout is a remotely operated mine rescue robot, which was developed by Sandia robotics engineers at Sandia under National Institute for Occupational Safety and Health (NIOSH) sponsored program [6]. Fig. 4. Gemini-Scout Robot in different terrain
Fig. 6(a). The CMERI Subterranean Robot, Fig. 6(b). Deployment of SR for Exploring a submerged mine tunnel at Satgram Project under ECL (West Bengal), India [8] Thrusters can be tilted to pitch-up or pitch-down while swimming. Track wheel arrangement provides more bearing area which helps to move over loose soil, sand and gravel. It can also perform its work in very narrow passages due to its smaller size and light weight (nearly 41.5 Kg). Amphibian characteristic provides it better working ability in adverse condition of partially or fully flooded mine tunnels. E. CMERI Mine Robot It is a six wheel mine robot which is being developed by conditions [6] CSIR-CMERI [10]. This system will find application in the It is a tracked wheel robot having good mobility to enable it survey, data collection and monitoring of the environment to overcome stair-like obstacles, slopes, sand, gravel, pits and 3D mapping of the mine tunnels. Essentially this will which are commonly found in mines. The robot is have wireless data communication between the command constructed in two segments. Both segments are connected computer (host) and the onboard vehicle computer (client).
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This system will have capability of autonomous navigation, F. Comparison of studied robots obstacle free path planning and intelligence to combat From the study of the above mine application robots, it unforeseen situation together with fault tolerant is evident that terrainability is an important issue which architecture in system design. demands special attention and needs to be addressed while designing a mobile robot for such applications. Apart from this, study also shows that usage of track belt mechanism has both merits and demerits. Some advantage and disadvantage of track belt robot over wheel robot are discussed below: Advantages: 1. It provides more traction as compare to wheel robot. Due to more bearing area it is able to move on loose soil, sand and gravel. It can also ascend and descend Fig.7. The CMERI Mine Robot stairs/steps, surmount obstacles or cross ditches easily. The robot has six wheels, mounted on rocker arm 2. It exerts less pressure on ground due to distribution of mechanism (fig.7). Six wheels provide it better load, so they are more suitable to soft surfaces like terrainability and stability (static and dynamic) over four snow. wheeled robots. The front and middle wheels are mounted 3. It has better terrainability over wheeled mobile robot. on a Y-shaped rocker-arm. The configuration of the arms 4. It has more static and dynamic stability. can be adjusted in an active fashion with the help of linear Disadvantages: actuators connected to them. The rocker arm helps the 1. It has law manoeuvrability and speed due to generation robot to cross an obstacle and climb stairs. Three wheels of of more friction and its complex traction system. each side are driven by a single motor and steering is 2. More power/torque is required to drive it. Design achieved by differential drive mechanism. becomes bulky. This robot has better terrainability, flexibility, and shock 3. Loose Chips/flanks can easily jam the track belt. absorption capability on rough terrain due to its all-wheel 4. It requires regular care and maintenance. drive mechanism and simple suspension system. Table 1 summarizes a comparison of all terrain robots developed by different researchers. GROUNDHOG GEMINI-SCOUT DAR CMERI-SR CMERI-MR
WHEEL/TRACK WHEEL TRACK TRACK TRACK WHEEL BODY ARTICULATE NO YES NO NO NO STEERING STEERED DIFFERENTIAL DIFFERENTIAL DIFFERENTIAL DIFFERENTIAL MECHANISM WHEEL DRIVE DRIVE DRIVE DRIVE SUSPENSION SYSTEM YES NO NO NO YES MASS 725.75 86 65 41.54 78 ( Kg ) DIMENSIONS (LxWxH 1524x990x940 1200x600x600 - 550x250x270 914x610x610 mm3) MAX. SPEED 2.682 1.565 0.889 0.50 0.70 (m/s) CAPABILITY All terrain robot All terrain robot All terrain robot All terrain robot All terrain robot
II. TERRAINABILITY OF UNDERGROUND MINE ROBOT Besides such terrain conditions, various features of the Floor condition plays an important role for safe mine floor plays an important role on mobility of robots. operation of underground mine robots. Floor condition Some such terrain features are explained in Fig. 8. All such provides a foundation for the roof supporting pillars, rails terrain features may not be negotiable by a particular for carriages etc. However, generally no special attention is mobile robot considering its design limitations. A few given on floor conditions while digging a tunnel resulting in design features for application in underground mine rugged and undulated mine floor. For this reason terrain conditions a robot must possess: condition of mines are not always found to be favourable • Good mobility over various type of terrain profile for locomotion of mobile robots. • Portability A. Terrain conditions • Must have better terrain compliant and smooth Possible terrain conditions of mines that a robot may turning ability encounter are: • Approachability into tight corners • Dry or rough terrain condition • Explosion-proof design and be able to tolerate heat • Sandy terrain condition and moisture • Muddy terrain condition • Higher dynamic stability • Wet or water logged terrain condition • Better shocks absorbing capacity for safety of the • Flooded condition etc. interior systems of the robot. B. Terrain features C. Wheel-Terrain Interaction Wheel-terrain interaction plays a very important role in terrainability of a wheeled mobile robot and a good knowledge of Terramechanics (interaction of wheeled or tracked vehicles on various surfaces) is required for its efficient design. While designing a mobile robot for mine Fig. 8. Possible terrain features of mine
6 Anil kumar Saw et.al/Terrainability of Mobile Robots in Underground Mining application, the following four types of wheel-terrain Where c1 and c2 are constant coefficients and s is the slip interaction may be considered [11]. ratio of the wheel. Expression of slip ratio for smooth i. Rigid wheel travelling over rigid terrain (Fig. 9A) wheels can be expressed as [13]: ii. Deformable wheel travelling over rigid terrain (Fig. 9B) (r v) r , ( v, 0 s 1) s = (6) iii. Rigid wheel travelling over deformable terrain (Fig. 9C) (r v) v , ( < , 1 s < 0) ω − ⁄ ω 𝑟𝑟ω ≥ ≤ ≤ iv. Deformable wheel travelling over deformable terrain Where� v is the travelling speed of the robot and rω is the (Fig. 9D). circumferentialω − ⁄ velocity𝑟𝑟 ωof the𝑣𝑣 wheel.− ≤ In Eq. (6), first case represents slip or pure rolling motion of wheel and second case represents skidding of wheel. For the safety of the interior systems, mine robots are generally designed to work at low-speed, hence we can neglect second case. The drawbar pull or net traction force (i.e. the difference between the thrust force and resistance force) DP, vertical force W, and angular torque T, with which the soil resists the rotation of the wheel, can be computed as [12]: Fig. 9. Possible wheel-terrain inte- raction cases. DP = rb 1 ( ) cos d 1 ( ) sin d (7) 2 2 Wheel-terrain interaction of a rigid wheel over deformable θ θ 1 1 soil has been studied [12]. W = rb θ ( ) sin d + θ ( ) cos d (8) �∫ 2 τ θ θ θ − ∫2 σ θ θ θ� θ θ 2 1 T = r b θ ( ) d (9) θ �∫2 τ θ θ θ ∫ σ θ θ θ� 1) Tractiveθ efficiency of wheel: θ Tractive∫ efficiencyτ θ θ can be defined as ratio of output power (net traction force) to input power (torque required for wheel driving). . ( ) = = (10) 2) Total𝐃𝐃𝐃𝐃 𝐯𝐯 resistance:𝐃𝐃𝐃𝐃 𝟏𝟏−𝐬𝐬 𝐫𝐫 Total𝛈𝛈 𝐓𝐓𝐓𝐓resistive force𝐓𝐓 (FT) experienced by the mobile robot can be expressed as: Fig. 10. Free body diagram of a rigid wheel on FT = FR + FS + FO + FD + FA + a. M + FP (11) deformable terrain. Where FR and FS are rolling and slope resistance In Fig. 10, W is the vertical load on the wheel due to respectively, FO is the obstacle resistance (resistance due to robot’s mass, DP is the drawbar pull or horizontal pull step, bump, ditch etc.), FD is the steering resistance, FA is the force, is torque applied at the wheel rotation axis, is the T b air resistance, a. M is the inertial load and FP is the drawbar width of wheel, z is the sinkage of the wheel under the pull. terrain surface, θ1 is the angle at which the wheel first makes contact with the terrain, θ2 is the angle at which the III. CONCLUSIONS wheel loses the contact from the terrain, σ is the radial The application of robot in mine rescue/mapping stress normal to the wheel-terrain contact, τ is the shear operation is limited due to limitations of knowledge of stress tangent to the wheel-terrain contact, r is the wheel terrainability in a constrained mine environment. This radius, θm is the angle at which the maximum radial stress paper clearly shows that terrainability is an important occurs, σ1 is the radial stress profile between θ1 and θm, and issue which deserves much attention while designing a σ2 is the radial stress profile between θm and θ2. robot for the said purpose. A robot with inherent capability 1. Interaction Model: Fig.10 illustrates a normal and to comply different terrain features is highly desirable. shear stress distribution at lower part of driving Terrain compliance can be achieved either with active or wheel, which can be expressed as: with passive design features [14]. Passive Terrain z n Compliance of the vehicle signifies its ability to adjust the (z) = (k + k b) (1) 1 2 b wheel configuration automatically and passively with the j variation in terrain contour. Fig. 11 describes the passive σ (z) = (c + tan� )�(1 e k) (2) − where k1 and k2 are �pressure sinkage moduli, n is terrain compliance of both non-tracked and tracked mobile τ σ φ − robots. For certain situations non-tracked types are found friction angle of soil, j is shear displacement and k is the to have better terrain negotiation capability, however from shearthe sinkage deformation exponent, modulus. c is the The soil normal cohesion, stress φ is for internal front the point of view of ‘steering’ and ‘load compliance’ the and rear regions can be computed as a function of the angle second option is generally preferred.
r n ( ) = (k + k b) (cos cos )n (3) θ,1 as follows:1 2 b 1 r n ( ) = (k + k b) cos ( ) σ 2 θ 1 2 � b� θ −1 θ 1 m Fig. 11(a). Terrain negotiation sequence of Non- θm cos 1n (4) Tracked mobile robot σ θ � � � �θ − θ θ − θ � − θ The normal stress around the wheel rim starts from zero at the free surfaces, and increases toward a maximum value. The maximum normal stress occurs at m and can be expressed as: Fig. 11(b). Terrain negotiation sequence of Tracked m = (c1 + c2s) 1 (5) point θ mobile robot [14] θ θ 7 Anil kumar Saw et.al/Terrainability of Mobile Robots in Underground Mining
Steering of individual wheels introduce technology/article/2011-08/sandias-gemini-scout- unnecessary complicacy in mechanical design of non- rescue-robot-optimized-mining-disasters. tracked robots. On the other hand, steering of tracked [7] GAO junyao, GAO xueshan, ZHU jianguo, ZHU wei, WEI mobile robots can be easily achieved by application of boyu, WANG shilin, “Coal Mine Detect and Rescue differential drive on the tracks. Moreover, in case of a Robot Technique Research,” Proceedings of the 2009 tracked wheel configuration, only one motored wheel per IEEE International Conference on Information and track serves the purpose making the design much simpler. Automation June 22 -25, 2009, Zhuhai/Macau, China. [8] Atanu Maity and Somajyoti Majumder, “Design of an ACKNOWLEDGMENT Amphibian Exploring Robot,” 27th International The CMERI Subterranean Robot was developed Conference on CADCAM, Robotics and Factories of the with the grant from Ministry of Coal, Govt. of India and the Future 2014, IOP publishing, IOP Conf. Series: CMERI Mine Robot is being developed with 12th FYP Materials Science and Engineering 65(2014)012015, project grant. Authors are grateful to CMPDI, Ranchi and doi:10.1088/1757-899X/65/1/01201. Satgram Project, ECL for their valuable suggestions and [9] Atanu Maity, Somajyoti Majumder, Dip Narayan Ray; assistance during field trials. Authors are also thankful to “Amphibian Subterranean Robot for Mine all the project members for their constant support for Exploration,” In proc. of 2013 International successful completion/execution of the projects. Conference on Robotics, Biomimetics, Intelligent REFERENCES Computational Systems (ROBIONETICS), Yogyakarta, [1] Coal Mining in India, Ministry of Coal, Government of Indonesia, November 25-27, 2013, pp. 242-246. India. http://www.coal.nic.in/content/coal-mining- [10] Council of Scientific and Industrial Research, Central india, Retrieved 26 June 2015. Mechanical Engineering Research Institute (CSIR- [2] BP Statistical Review of World Energy, June 2015, CMERI), Durgapur, West-Bengal, India, http://www.bp.com/ content/dam/bp/pdf/Energy- http://www.cmeri.res.in. economics/statistical-review-2015/bp-statistical- [11] Iagnemma, K., Dubowsky, S. Mobile Robots in Rough review-of-world-energy-2015-full-report.pdf. Terrain. Springer-Verlag Berlin Heideberg, 2004. [3] Coal - Indian Energy Choice, Ministry of coal, [12] H. Shibly, K. Iagnemma, and S. Dubowsky, "An Government of India, equivalent soil mechanics formulation for rigid wheels http://www.coal.nic.in/content/coal-indian-energy- in deformable terrain, with application to planetary choice, Retrieved 26 June 2015. exploration rovers," Journal of Terramechanics, no. [4] Coal mine disasters, 42, pp. 1-13, 2005. http://www.survivalring.org/awareness/what-do- [13] Liang Ding, Haibo Gao, Zongquan Deng, Kazuya you-want-to-survive/accidents-disasters/, Retrieved Yoshida, and Keiji Nagatani, “Slip Ratio for Lugged 26 June 2015. Wheel of Planetary Rover in Deformable Soil: [5] S. Thrun, S. Thayer, W. Whittaker, C. Baker, W. Definition and Estimation,” IEEE/RSJ International Burgard, D. Ferguson, D. Hahnel, M. Montemerlo, A. Conference on Intelligent Robots and Systems (IROS Morris, Z. Omohundro, C. Reverte, and W. Whittaker, 2009). “Autonomous exploration and mapping of abandoned [14] Atanu Maity, DN Ray, S. Majumder, KK Mistry, "An All mines,” IEEE Robot. Autom. Mag., vol. 11, no. 1, pp. 79- Terrain Mobile Robot with Passive Compliance"; 91, Dec. 2004. Conference Proceedings of Factory Automation, [6] D. Clay. (2001, Aug. 18). Sandia's Gemini-Scout: A Robotics and Soft Computing, January 2007, pp. 73-78. Rescue Robot Optimized for Mining Disasters. [Online]. Available: http://www.popsci.com/
How to cite this article: SAW, ANIL KUMAR. Terrainability of Mobile Robots in Underground Mining. Asian Journal of Current Engineering and Maths, [S.l.], v. 5, n. 1, p. 4-8, feb. 2016. ISSN 2277-4920. Available at:
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