DESIGN OF A HAPTIC DEVICE FOR EXCAVATOR EQUIPPED WITH CRUSHER

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1 DESIGN OF A HAPTIC DEVICE FOR EXCAVATOR EQUIPPED WITH CRUSHER Kyeong Won Oh, Dongnam Km Korea Unversty, Graduate School 5Ga-1, Anam-Dong, Sungbuk-Gu, Seoul, Korea {locosk, smleast}@korea.ac.kr Jong-Hyup Park Naekyung Engneeng Co., Ltd. 5-1 Sewon buldng, Yangjae-Dong, Seocho-Gu, Seoul, Korea nk2900@empal.com Daehe Hong Korea Unversty, Dvson of Mech. Engneerng 5Ga-1, Anam-Dong, Sungbuk-Gu, Seoul, Korea dhhong@korea.ac.kr Sukhe Hong Naekyung Engneeng Co., Ltd. 5-1 Sewon buldng, Yangjae-Dong, Seocho-Gu, Seoul, Korea hongcon@korea.com ABSTRACT The dsmantlng processes are very dangerous and there have been many studes for utlzng a remote control system to ncrease operator s safety. Ths paper deals wth the remote control problem by developng a novel haptc devce to control an excavator equpped wth the crusher whch s one of the most frequently used attachments. Frstly, the newly desgned haptc devce s descrbed to explore the operablty to the excavator equpped wth the crusher. Not only the excavator body but also ts arm, boom, swng, and crusher are consdered n the desgn. Then, ts workspace s analyzed and the mappng between the haptc devce and the excavator s examned. Also, the performance ndex of haptc devce s used to dscuss the control effcency. Secondly, through the knematcs analyss about arm, boom, and swng motons of the excavator, the poston nformaton of each jont s analyzed n 3-dmensonal space. Lastly, both the haptc devce and the excavator are modeled usng OpenGL program and 3D graphcal smulatons are extensvely performed. The structure of ths new haptc devce s smple and can be easly manufactured. It can be used to operate the excavator wth crusher more convenently and transparently from a remote ste away from the dangerous stes. KEYWORDS Haptc Devce, Excavator, Crusher Attachment, Dsmantlng Process, Remote Control 1. INTRODUCTION Today, there are lots of remodelng and dsmantlng of buldngs to buld new skyscrapers n constructon stes. And to dsmantle the buldng, excavator equpped wth the crusher s the most frequently used. However, n ths case, operators have to rde on the excavator drectly, so they have had a lot of exposure to unexpected danger. 202

2 There have been some current studes about the teleoperaton of excavator to make up for ts defects. Frst, remote control of excavator usng Phantom, whch s commercal haptc, was studed by Frankel [1]. And knematcs analyss and smulaton of constructon devces were conducted by Frmpong [2]. Moreover Hrabayash [3] studed teleoperaton of excavator, whch was operated n underwater. And last, before ths research, a new desgned haptc devce for excavator s moton s proposed by Km [4]. In ths paper, a novel concept of tele-operated haptc devce s proposed, n order to make an offer more safe and effcent control to operator whle n dsmantlng processes. Ths new haptc devce s consdered not only drvng of excavator body but also controllng the basc moton of excavator such as swng, boom, arm and crusher. It has smlartes to exstng joystck of excavator and smple structure. So, operator can use haptc devce easly, even f they control for the frst tme. To explan operaton prncple of the haptc devce, frst of all, knematcs analyss of excavator and haptc devce has to be preceded through ts modelng. And then, connecton between excavator and haptc devce should be dscussed. Sometmes, t s mpossble to control, because of exceedngly generaton of reflecton force. For more effectve operaton, t s mportant that operator takes cognzance of reflecton force whch s exerted on excavator especally crusher. So, a new desgned haptc devce s consdered force feedback. Then, to ncrease performance and capablty of haptc devce, the performance ndex of haptc devce should be analyzed. On ths occason, mappng s based on performance ndex, through analyss of workspace between excavator and haptc devce. Lastly, both the haptc devce and the excavator are modeled usng OpenGL program and 3D graphcal smulatons are extensvely performed. 2. KINEMATICS OF EXCAVATOR EQUIPPED WITH CRUSHER 2.1. Modelng of Excavator In ths paper, the excavator whch has 4 basc motons, swng, boom, arm and bucket, among many knds of backhoes s used. And ths s equpped wth 203 crusher nstead of bucket. Bucket jont has an only 1DOF, rotaton of bucket, orgnally. But, n ths case, t has totally 5DOFs, because cuttng and rotatng moton are ncluded n crusher. Hence, based on ths moton, the coordnate system and moton of each lnk about modeled excavator equpped wth crusher are shown n Fg. 1. There s one more DOF of rotatonal crusher jonts about X e4 n large sze of excavator, however t s not consdered n ths paper. Fgure 1. Modelng of Excavator Equpped wth Crusher Axs of swng jont s represented by Z e1, and the rest of four jont axes, boom, arm, and crusher are also represented n sequence. Rotatonal axes of each lnk are perpendcular at Fg. 1 except for axs of swng Knematcs Analyss of Excavator After ths modelng process, forward and nverse knematcs analyss of excavator has to be studed. When the haptc devces are desgned, especally, nverse knematc s very mportant. When control moton of boom and arm are tred, these postons should be analyzed to understand whole of excavator status. Through, nverse knematcs analyss, the poston of each lnk, boom, arm, and crusher can be acqured. In order to acqure nformaton of poston more easly for operator, poston of crusher jont, arm s tp, s analyzed frst of all [4]. In actualty, for dsmantlng processes, swng moton and moton of crusher do not take part n poston of arm s dstal jont. So, knematcs analyss can be treated 2- dmentonal problem of 2DOFs, boom and arm. Ths can be obtaned by absolute poston of the haptc stylus. Then, usng ths, the poston of each lnk can be obtaned by analyss of nverse knematcs. Followng equatons are nverse knematcs

3 equatons to calculate the angles of boom and arm. ( ) + r ( ) r24 y 1 a2 24 a3 θ e2 = tan + cos r x 2a r (1) a2 a3 r13 θe3 = π + cos (2) a a 2 3 θ e : Rotatonal angle of excavator ( = 1, 2, 3, 4) r jk : Dstance between Z ej and Z ek ( j, k =1, 2, 3, 4) 3. THE NOVEL CONCEPT OF HAPTIC DEVICE 3.1. Desgn Concept and Knematcs A novel haptc devce s smlar to lever of excavator whch s currently used. Fg. 2 shows new desgned haptc devce. Coordnate assgnment s also shown n the fgure wth D-H coordnate system. The haptc devce has 3 rotatonal jonts, 1 prsmatc jont, and buttons for crusher and a sphercal jont for excavator drvng. And the used parameter values are defned, as shown n Table 1. Moton of swng and crusher s drectly connected to three jonts of haptc devce to provde convenence to operator. The swng moton s controlled by θ and moton of the crusher, rotaton and nppng moton are controlled by θ and buttons, drectly. And the h4 poston of arm s dstal jont s controlled by only θ, d of haptc devce and the angle of boom and arm can be calculated by analyss of nverse knematcs. It was ponted out n the prevous chapter. And to calculate the poston vector of endpont of haptc stylus relatve to base frame, transformaton matrx T s used lke followng equaton (3). It s necessary that haptc devce connect wth excavator to control dstal jont of arm. Fgure 2. Haptc Devce wth D-H Coordnates Table 1. D-H Parameters of Haptc Devce cosθ snθ cos sn cos cos α θ α a θ sn cos cos cos sn a snθ θ θ α θ α T = (3) 0 snα cosα d Jont θ h 2 / 2+ α h a h d h π θ π / d And there are 5 actuators, electrcal motors and 5 encoders nsde the haptc devce. The nternal mechansm of haptc devce appears n Fg. 3. The encoders read the angle of each lnk and the actuators offer force feedback to operator actng on excavator. In order to ncrease the effcency of operaton and the protecton of equpment, t s necessary to detect the reflecton forces. 204

Fgure 3. Internal Mechansm of Haptc Devce d. Fg. 4 (a) s a pcture of show the moton of θ and d. θ and Fg. 4 (b), (c) 3.2.

The nppng moton of crusher can be operated easly by fngers of operator. Whle pushng the buttons, operator makes fngers lke tweezers and takes the moton smlar to crusher.

Moton of Excavator Fg. 4 shows the moton of haptc devce to operateθ, θ and d. To provde smple functonal adaptaton, operaton method of haptc devce s desgned qute smlar to excavator.

So, the swng moton s represented by rght and left moton of haptc, θ, just lke excavator s controller.

4 Fgure 3. Internal Mechansm of Haptc Devce d. Fg. 4 (a) s a pcture of show the moton of θ and d. θ and Fg. 4 (b), (c) Movement of Haptc Devce for Crusher In order to operate more smply, shape and operatng prncple of crusher should be consdered. Fg. 5 s an extended pcture of crusher part of haptc. The nppng moton of crusher can be operated easly by fngers of operator. Whle pushng the buttons, operator makes fngers lke tweezers and takes the moton smlar to crusher. And rotatonal moton of crusher s operated by thumb wheel. The motons of crusher are controlled drectly lke swng. (a) θ (b) θ (c) d Fgure 4. Moton of Haptc Devce 3.2. Moton of Haptc Devce Moton of Excavator Fg. 4 shows the moton of haptc devce to operateθ, θ and d. To provde smple functonal adaptaton, operaton method of haptc devce s desgned qute smlar to excavator. When an actual condton, the swng of excavator s controlled by the rght and left movement of left sde lever. And operaton of boom and arm s controlled by front and rear motons of each sde joystck. So, the swng moton s represented by rght and left moton of haptc, θ, just lke excavator s controller. And operaton s progressed n actual, operator usually control moton of boom and arm at the same tme wth both hands, through movng the lever front and rear. The haptc devce s desgned smlarly. Usng the haptc devce, operator also can control boom and arm at once through the combnaton of θ wth 205 Fgure 5. Crusher Part of Haptc Devce Fgure. 6. Drvng Control Part of Haptc Devce Whle the work s progressed, operator should have a grasp of the problem about reflecton force actng on crusher to mprove effcency. For ths reason, the nsde of haptc devce that has torson sprngs, servo motor [5].

5 If the crusher takes a nppng moton wthout object, an assstant lnk whch s connected wth the servo motor can move up and down as torson sprngs hold ts shape. If the crusher dsmantles some objects, torson sprngs wll be changed by the movement of assstant lnk. Owng to the servo motor pushes up the assstant lnk that depends on the acton of reflecton force upon the crusher. At ths moment, operator can perceve the force that s exerted on crusher by ncreased moment of torson sprng. If there s an outbreak of great force over the lmt, the servo motor wll prevent the assstant lnk from movng and protect the crusher Drvng Control Usng Haptc Devce In ths study, one of the notable features of the new desgned haptc devce s that operator can control each lnk of excavator and drve body usng only one joystck, as shown n Fg. 6. For the drvng excavator, frst, the haptc stylus should be taken down. In ths case, another part of haptc devce holds the ntal poston of thers so as not to operate durng the drvng. The bottom of stylus equpped wth sphercal jont so that t can move freely. And sphercal jont pushes down the drecton button. Whle the drvng of excavator s controlled, the whole of upper body of haptc devce wll move to any drecton relatve to the base frame of haptc devce. And equpped sprngs make the stylus move to ntal poston. There are force-sensors under the button, so that veloctes of both caterpllars are controlled separately by the pressure. 4. WORKSPACE MAPPING AND PERFORMANCE INDEX 4.1. Workspace Analyss of Excavator Workspace of excavator should be analyzed to evaluate the performance ndex of haptc devce. Fg. 7 shows the workspace of excavator by boom and arm from the sde vew wthout swng moton. Parameters are based upon a small sze excavator, SOLAR 015, whch has 1.5 tons of receptve capacty. In the fgure, rotatonal axs of boom s the orgn. When the boom jont moves from -56 to 74 degrees, the cross ponts represent the trajectory ponts of dstal jont of boom. And dot ponts represent jont of arm when the range angle of arm s from 218 to 328 degrees. For the reason mentoned prevous chapter, end-pont of arm, the poston of crusher jont, s controlled ultmately. Now to conclude, ths area can be defned as workspace of excavator Workspace Mappng and Performance Index The dstal jont of arm s controlled by end-pont of haptc stylus. So, workspace of excavator should be covered by workspace of tp of stylus, completely. Fg. 8 shows workspace mappng between excavator and haptc devce. Workspace of haptc devce s concerned about only θ, d, because end-pont of stylus connected wth dstal jont of arm are the most needed. Although there s an angle dfference n workspace analyss, whch t s not concerned, operator can put to rghts t by ntuton durng the dsmantlng process. And performance ndex s defned, as shown n equaton (4). For the better performance ndex, θ, d should be as small as possble on mappng. (1 R) 100 P. I.( A, D, R) = A D and remanng area (4) When the performance ndex s bgger, the more effcent operaton can be advanced. In ths equaton, A s the range of θ, ths value s from 50 to 90 degrees. And D s the range of d, R s the rato of remanng area whch s calculated by AutoCAD. In ths paper, among all plausble cases, three of them whch have the best results were compared, and then, the best performance ndex s decded. Now, n order to adjust dfference dmenson between excavator and haptc, scalng factor s appled and same scalng factor s used, 30. The frst case, the functon s P. I.(82, 0.066, 63.0) and the value of functon s And the second case, P. I.(60, 0.070, 55.5), the performance ndex s evaluated by And then, n the last case, P. I.(57, 0.071, 59.5), s performance ndex. At ths moment, the most effcent operaton wll be progressed. As ths result, workspace of haptc devce can be defned. 206

Fgure 7. Workspace of Excavator Fgure 8.

Smulaton Results Usng OpenGL Program Swng Moton Control of Boom and Arm Nppng

SIMULATION RESULTS Table 2 summarzes smulaton results whch are modelng of

In the smulaton, ths program works n real tme.

poston of crusher jont, and thumb wheel s drectly used to control rotaton of

6 Fgure 7. Workspace of Excavator Fgure 8. Workspace Mappng between Excavator and Haptc Devce Table 2. Smulaton Results Usng OpenGL Program Swng Moton Control of Boom and Arm Nppng Moton Rotaton of Crusher 5. SIMULATION RESULTS Table 2 summarzes smulaton results whch are modelng of excavator equpped wth crusher usng OpenGL program and movements of excavator are shown. One excepton to ths s drvng moton, snce t s not easy to dsplay on fgure. In the smulaton, ths program works n real tme. So mouse s used to control haptc and poston of mouse cursor represents the 2D poston of crusher jont, and thumb wheel s drectly used to control rotaton of crusher. Swng and drvng of excavator s controlled by pushng the arrow key. 6. CONCLUSION In ths paper, the haptc devce s newly desgned to control excavator equpped wth crusher. Knematcs and workspace analyss are conducted and performance ndex s evaluated by workspace mappng. Then, usng OpenGL, graphcal smulaton 207

7 control of excavator s ncluded. As a result, ntutvely convenent haptc devce s desgned. 7. ACKNOWLEDGEMENTS Ths research was supported by a grant (code : 06 Constructon Core B04) from Constructon Core Technology Program funded by Mnstry of Constructon & Transportaton of Korean government and BK21. REFERENCES [1] Frmpong, S.; LI, Y. 2005, Vrtual prototype smulaton of hydraulc shovel knematcs for spatal characterzaton n surface mnng operatons, Internatonal Journal of Surface Mnng, Reclamaton and Envronment Vol. 19, No. 4, pp. 238~250. [2] Frankel, J. G. 2004, Development of a Haptc Backhoe Testbed, A Thess of Master of Scence, School of Mechancal Engneerng Georga Insttute of Technology. [3] Hrabayash, T.; Yamamoto, T. 2006, Experment of Teleoperaton of Underwater Backhoe wth Haptc Informaton, 23 rd Internatonal Symposum on Automaton and Robotcs n Constructon, pp. 36~41. [4] Km, D.; Hong, K.; Oh, D.; Park, J.; Hong, S. 2007, Desgn of Haptc Devce for Dsmantlng Process Usng Excavator, 24 th Internatonal Symposum on Automaton & Robotcs n Constructon, pp. 175~180. [5] Oh, K.; Km, D.; Hong, D.; Park, J. 2007, Desgn of a Haptc Devce for Crusher Attachment of Excavator, Korean Socety for Precson Engneerng 2007 Sprng Conference, pp. 381~

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