In this project, we construct micro tele-operation systems which enable human operators to performe micro tasks, such as assembly or manufacturing, without feeling a stress. We introduce haptic interfaces that give operators the impression as if he/she were touching the expanded micro objects with his/her fingers. We construct simulator systems modeled on remote environment. In this paper we give an outline and concept of this project. 
This research project can not only extend bilateral tele-operation to many other industries, it can also extend this human-friendly technique and thus help realize savings in resources, energy, costs and human support.Opisana je izvedba mikrosustava za rad na daljinu koji omogućava bez stresa obavljanje mikroradnji, kao što su montaža i proizvodnja. Prikazano je haptičko sučelje kojim se oponaša dodir uvećanog mikroobjekta prstima rukovatelja. Također je opisan koncept sustava i simulator sustava. Istraživanje izloženo u ovome radu, osim što može uvesti daljinsko upravljanje na mikro razini u mnogim granama industrije, otvara i mogućnosti primjene za štednju resursa, energije i troškova

Hideki Hashimoto

Noriaki Ando

Peter Korondi

Peter T. Szemes

English

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1. INTRODUCTIONMost of the small quantity production for trialmanufacture in laboratory when developing newproducts and works such as inspection or repairingof products have to be done by human manufactu-ring because it is difficult to hope dramatic deve-lopment in AI fields today.These works force human to suffer a lot of stressby using microscope and micro tools.Today products are evolving precise and complexmore and more, however, on the other hand, wor-kers are becoming older and older. Thus it is easyto forecast that precise works become more difficultin the near future.These stressful works are caused by the differen-ce of the scale between human and targets. Con-necting human and targets by teleoperation enablesfree scaling between human and targets, so it ispossible to solve these problem. Furthermore, sinceit also enables to separate workspaces from humanenvironment in the distance, we can reduce thescale of factories and save energy. As it is also pos-sible to work wherever by using network, it leads tosaving energy of human transportation.In this research we will construct the micro tele-operation systems which enable human operators tooperate micro tasks, such as assembly or manufac-turing of small components, without feeling stress.We introduce haptic interfaces, which give opera-tors the presence as if he/she touches the expandedmicro objects with his/her fingers.2. SYSTEM COMPOSITIONIn this research we developed micro teleopera-tion systems shown in Figure 1. We introduce notonly visual interfaces but also original haptic inter-faces which feedback force and offer the presenceto operators. For slave device, we developed a pa-rallel link manipulator [1, 2]. In general, parallellink structure has good features of precision andstiffness, although it has small workspace and manysingular points [3]. We adopted this structure be-cause we thought its characteristic is proper for pre-cise works.Peter T. Szemes, Peter Korondi, Noriaki Ando, Hideki HashimotoFriction Compensation for Micro Tele-Operation SystemsUDK 621.85-181.4IFAC IA 4.0.6Original scientific paperIn this project, we construct micro tele-operation systems which enable human operators to performe microtasks, such as assembly or manufacturing, without feeling a stress. We introduce haptic interfaces that give opera-tors the impression as if he/she were touching the expanded micro objects with his/her fingers. We construct simu-lator systems modeled on remote environment. In this paper we give an outline and concept of this project. This research project can not only extend bilateral tele-operation to many other industries, it can also extendthis human-friendly technique and thus help realize savings in resources, energy, costs and human support.Key words: tele-operation, haptic interfaces, parallel link, serial link, master-slave, bilateral, micro works, network,simulator, scaling AUTOMATIKA 42(2001) 1−2, 23−27              23ISSN 0005−1144ATKAAF 42(1−2), 23−27 (2001)Fig. 1 Overview of the Micro Tele-Operation System3. SLAVE DEVICEAs a slave device, we developed parallel link ma-nipulator what has 6 degrees of freedom. It has 3degrees of freedom for XYZ linear motion and 3degrees of freedom for rotation of each axis. Itsworkspace is almost 30 mm × 30 mm × 30 mm forlinear motion and 15 degrees for rotation. Differentfrom general Stewart Platform, it has novel struc-ture: Six links which sprouted verticality from basetable can expand and contract. Each two links ofsix links are combined into one by sublink. Ulti-mately, the end effector table is holded by total 3points. The structure is shown on Figure 2.By adopting this structure, we can save space al-though analysis of kinematics and dynamics be-comes difficult. Workspace and singular points, pe-culiar to this structure, need to be analyzed. Theappearance of the slave device is shown in Figure 3.4. SLIDING MODE BASED DISTURBANCE OBSERVERConsider the following model with external dis-turbances and uncertain parameters satisfying theso-called Drazenovic condition [4], written in theregular state equation form, (3)where and B−2 denote the nominal or desired (ideal) systemmatrices. The bar •− refers to the reference value inthis paper. ∆A2, j(j = 1, 2) and ∆B−2 are the respecti-ve uncertain perturbations and f(t) is an unknown,but bounded disturbance with bounded first timederivative with respect to time.Now η is defined as the uncertainties and thedisturbance of the system.(4)The second line of (3) can be rewritten by η.(5)According to [5], is estimated by a disconti-nuous observer:(6)where ν is the discontinuous feedback. The goal ofthe design to find a feedback signal, denoted ν,such that the motion of the system (3) is restrictedto belong the manifold S.(7)The simplest control law, which can lead to sli-ding mode, is the relay:(8)If η is in the range of B2 (η ⊂ range (B2)), theideal sliding mode occurs [6].v Mi i i= sign( ) .σS x x x Rm= = − = ∈2 2 2 0σ σ .n s where  ( )x A x A x B u2 21 1 22 2 20= + + + νx2x A x A x B u2 21 1 22 2 20= + + + ηη = + + +∆ ∆ ∆A x A x B u E f t21 1 22 2 202 ( )x R x R u R A i jn m m m ij1 2 1 2∈ ∈ ∈ =− , , , ( , , )( )xxA AA A A AxxB BuEf t1211 1221 21 22 22122 2020 0LNMMOQPP + +LNMMOQPPLNMMOQPP+++LNMMOQPP+LNMMOQPP∆ ∆∆24                                   AUTOMATIKA 42(2001) 1−2, 23−27P. T. Szemes et al.Friction Compensation for Micro ...Fig. 2 Structure of slave deviceFig. 3 The appearance of the slave deviceIf the system trajectory is on the sliding surfacethen there is a continuous control signal, so calledequivalent control signal, veq, which can hold thesystem on the sliding manifold, (but it does notguarantee the convergence to the sliding manifoldin general). If the system is in sliding mode (σ = 0and σ⋅ = 0),(9)(10)Clearly, veq contains information on the system'sparametric uncertainties and the external distur-bance, which can be used for feedback compensa-tion. Supposing for the time being that veq is knownand a modified control input signal is used.(11)According to (5) and (10), the system responsefor (11) coincides with the nominal or ideal, undis-turbed system response for the control u,(12)In the practice, there is no way to calculate theequivalent control veq precisely, but it can be esti-mated by a low pass filter for v as showed in Figu-re 4. In [7] an additional control parameter intro-duced, instead of low pass filter. There are twoloops on Figure 4. The observer – sliding modecontroller loop should be as fast as possible toachieve an ideal sliding mode. This is granted be-cause this loop is realized in a computation enginein the recent application. The real system – com-pensator (consisting of Sliding Mode Controller andLPF) loop should be faster than the change of thedisturbance. On the other hand, the smallest un-modeled resonant frequency of real system shouldbe out of the bandwith of that loop to avoid chat-tering. .x A x A x B u B veq2 21 1 22 2 2 20= + + − + η  u u veq0 = − .B v A x A x B u E feq2 21 1 22 2 202= + + + =∆ ∆ ∆ η .ση= + + + −∆ ∆ ∆A x A x B u E f B veq21 1 22 2 202 2  5. CHATTERING FREE IMPLEMENTATION OFSLIDING MODEThe robustness of continuous time sliding modecontrol is realized by the high-frequency switchingof the discontinuous observer feedback signal ν. Toadapt the sliding mode philosophy for a discretetime observer [7], the sampling frequency should beincreased compared to Lumberger observer. If theswitching frequency of the relay (8) is not enoughhigh, σ might chatter around the manifold σ = 0 asshown on Figure 5, where Tk denotes the time ofk-th sampling. In case of discrete-time observer, theobserver feedback signal ν may switch from +Mi and−Mi and vice versa resulting νkeq = 0 even if νeq ≠ 0.The bigger the Mi is, the bigger the chattering is. Inthe other hand, if Mi is smaller than the distur-bances, it cannot eliminate it.AUTOMATIKA 42(2001) 1−2, 23−27              25P. T. Szemes et al. Friction Compensation for Micro ...Fig. 4 Sliding mode based feedback compensationFig. 5 Discrete-time chattering phenomenonApplying the Lyapunov stability theory, let thepositive definite Lyaponov function candidate ischosen in the following form:(13)The observer feedback is chosen in such a way,that the derivation of the Lyaponov function meetthe following condition:(14)As it was proposed in [7, 8], the condition (14) issatisfied if(15)where D is a positive definite matrix. According to(5), (6) and (7)(16)Applying (10), the equivalent observer feedbackcan be expressed from (16)(17)ν ν σ σeq B A= + −−2122(  ) (  ) ( )σ ν ησ= − − +A x x B22 2 2 2   V D DT= − = −σ σ σ σin other words:  ,V T= <σ σ 0V T= σσ2.To meet the condition (15), the observer feed-back is chosen in the following way(18)The first term is responsible for the chatteringfree reaching of the sliding manifold, but it is 0, ifthe system in sliding mode. Since νeq is not known,it must be estimated. Supposing, that the equivalentobserver feedback is changing smoothly, (17) is es-timated at the k-th sampling period by(19)where T is the sampling period. Substituting (19) inthe discrete form of (18)(18)where 6. EXPERIMENTALRESULTS: DESIGN OFFRICTION COMPENSATION FOR A SINGLE JOINTThe method described in Section 4 was appliedfor a single joint. From the point of view of theoperator the whole dynamics of the mechanism(not only the friction) is disturbance. The whole dy-namics of the system cannot be eliminated (since itwould needed infinite input power) but the effectof the friction can be depressed. The aim of thecompensation is to make the system follow an idealmodel, which has small friction and with small dy-namics. In other words, because of the compensa-tion, the operator feels that it is very easy to movethe master device. The optimal force feedback forthe most comfortable telemanipulation can be asubject of another research. In this paper, the nomi-nal parameters of the corresponding motor areused to calculate the ideal model of the dynamic ofa joint. In other words, the effect of the mechanismare ignored. The control parameters were tuned′ = ′ = +B B T D TD I2 2 , .andν ν σ σk k k kB D= + ′ ′ −− − −1 21 1( ) ( ) ( )ν ν σ σ σeqk k k k kB T A= + − −− − −1 21 122e jν σ ν= + +−B D A eq2122( ) .Figure 7 shows the time functions of the refe-rence and the measured positions. It is well known,that the PD controller can not eliminate the steadystate error (see Figure 7) the motor is sticked be-fore reaching the reference value. The additional ex-ternal disturbance increases the error dramatically.The same PD controller with disturbance observerand compensator can eliminate these errors (seeFigure 7). The position signal can reach the refe-rence signal and the external disturbance is alsoeliminated. These results demonstrate the effective-ness of the sliding mode based disturbance obser-ver, when external disturbance occurs. The advan-tage of this method that it does not need model in-version, which was the main problem in case of theinverted model, based disturbance observer.26                                   AUTOMATIKA 42(2001) 1−2, 23−27P. T. Szemes et al.Friction Compensation for Micro ...Fig. 6 Overall control sheme for position controlFig. 7 PD type controller with and without disturbance observerand the effect of friction compensation was verifiedby a position control experiment. In this experimental two type of control patternwas introduced:– PD type controller without friction compensa-tion– PD type controller with friction compensation.REFERENCES[1] K. Cleary, T. Arai, A Prototype Parallel Manipulator: Kine-matics, Construction, Software, Workspace Results, andSingularity Analysis. Proceedings of the IEEE InternationalConference on Robotics and Automation, Vol. 1, pp 566–571, 1991.[2] E. F. Fichter, A Stewart Platform-Based Manipulator: Gene-ral Theory and Practical Construction. The InternationalJournal of Robotics Reseach, Vol. 5, No. 2, pp 157–182,1986. [3] K. Fujimoto, S. Tadokoro, T. Takamori, Development of a 6--D.O.F Direct-Drive Wrist Joint by Pneumatic Linear Actu-ator Drive. Proceedings of 16th Annual Conferece of IEEEIndustrial Electronics Society (IECON'90), Vol. 1, pp 427– 432, 1990. [4] B. Drazenovic, The Invariance Condition in Variable Struc-ture Systems. Automatica, Vol. 5, No. 3, pp. 287–295, 1969.[5] P. Korondi, K-K. D. Young, H. Hashimoto. Discrete-timeSliding Mode Based Feedback Compensation for MotionControl. Proc. of the 1996 IEEE Intl. Workshop on VariableStructure Systems, December 5–6, 1996, Tokyo, Japan.[6] V. I. Utkin, Sliding Modes in Control and Optimization.Spinger-Verlag, 1992.[7] O. S. Bogosyan, M. Gokasan, A. Sabanovic. A Sliding ModeBased Disturbance Observer for Motion Control Systems.VSS'99 Conference, Florida, 1999.[8] A. Sabanovic, N. Sabanovic, K. Jezernik, K. Wada, Chatte-ring Free Sliding Modes. The Third Worksop on Variable Structure Systems and Lyaponov Design Napoly, Italy, 1994.AUTOMATIKA 42(2001) 1−2, 23−27              27P. T. Szemes et al. Friction Compensation for Micro ...Kompenzacija trenja u mikrosustavima upravljanja na daljinu. Opisana je izvedba mikrosustava za rad nadaljinu koji omogu}ava bez stresa obavljanje mikroradnji, kao {to su monta`a i proizvodnja. Prikazano je hapti~kosu~elje kojim se opona{a dodir uve}anog mikroobjekta prstima rukovatelja. Tako|er je opisan koncept sustava i si-mulator sustava. Istra`ivanje izlo`eno u ovome radu, osim {to mo`e uvesti daljinsko upravljanje na mikro razini umnogim granama industrije, otvara i mogu}nosti primjene za {tednju resursa, energije i tro{kova.Klju~ne rije~i: upravljanje na daljinu, hapti~ko su~elje, paralelna veza, serijska veza, bilateralnost, mikrorad, mre`a,simulatorAUTHORS’ ADDRESSES:Peter T. Szemes, Peter KorondiDepartment of Automation, Technical University of Budapest1111 Budapest, Budafoki út 8, F.II., HungaryPhone: +36-1-463-1165, Fax: +36-1-463-3163{szemes, korondi}@elektro.get.bme.huHideki HashimotoInstitute of Industrial Science, University of TokyoDepartment of Electrical Engineering7-22-1, Roppongi, Minato Ku Tokyo 106 Japanhashimoto@vss.iis.u-tokyo.ac.jpReceived: 2001−10−05

Kompenzacija trenja u mikrosustavima upravljanja na daljinu

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