A constraint-based approach for multi-modal robot control

Transcription

1 A cnstraint-based apprach fr multi-mdal rbt cntrl Jris De Schutter KU Leuven Department f Mechanical Engineering Divisin f Prductin Engineering, Machine Design and Autmatin (PMA) See and Tuch: 1st Wrkshp n multimdal sensr-based rbt cntrl fr HRI and sft manipulatin, IROS 2015, Hamburg, September 28 th, 2015

2 Outline Brief verview f previus Leuven Cnstraint-based apprach Task mdeling and cnstraint specificatin Cntrl and estimatin Recent applicatins Discussin J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 2

3 Brief verview previus Leuven These vides and many yutube channel: kuleuven rbtics and mechatrnics rbtics research grup: my hme page: Overview f relevant papers at these webpages. J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 3

4 Brief verview previus Leuven 1978: (Js Simns) first frce cntrl results clse-tlerance peg-in-hle assembly custm-built 5-axis rbt frce/trque measurements based n mtr currents ~ 1984 several experiments (peg-in-hle, 2D/3D cntur fllwing, pallletizing, pening/clsing a dr) bulky hydraulic Cincinnati-T3 rbt custm-built 6 axis frce/trque sensr (Rik (Henri) Beliën) task frame at rbt end effectr velcity-reslved cntrl J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 4

5 Brief verview previus Leuven Early nineties add mdel-based feedfrward (Herman Bruyninckx) 2D cntur tracking peg-n-hle extend t cperating rbts ~ 2000 cmbinatin f frce cntrl with visin multiple task frames identificatin f cntact gemetry (Tine Lefebvre) 2005 human-rbt interactin multi-mdal sensing multiple task frames J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 5

6 Brief verview previus Leuven Lessns learnt similarities between different types f gemetric sensrs sft cntacts can be mdeled as gemetric defrmatins using cmpliance mdel (hard cntacts are mdeled by hard cnstraints) task defined by varius cnstraints, specified in different spaces ( frames ) feedback is always t late: (task executin speed) ~ (cntrl bandwidth) x (gemetric task executin errr) fr cntact: (gemetric errr) = (frce errr) x (cmpliance) prprtinality in this eq. depends n errr in gemetric mdel: task executin speed and accuracy are imprved by feedfrward cntrl based n gemetric mdels cntact gemetry can be identified by bserving mtin (and cntact frces) during task executin r active sensing mtins J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 6

7 Cnstraint-based cntrl Cnsider every rbt system as a set f degrees f freedm Frmulate every rbt task as an ptimizatin prblem Optimizatin variables velcity, acceleratin r trque fr each actuated df at every time instant Objective functin cnflicting cnstraints: minimize cnstraint vilatins task redundancy: e.g. minimize kinetic energy lcal (instantaneus) vs. glbal (ver time), e.g. minimum time, minimum energy J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 7

8 Cnstraint-based cntrl Cnstraints (nt exhaustive...) task-related fllw predefined trajectry in sme directin track bject in sme directin based n sensr infrmatin (e.g. visin, frce, distance) apply frce r trque in sme directin impse impedance r admittance in sme directin rbt system-related avid jint limits: psitin, velcity, acceleratin, trque avid self-cllisin envirnment-related avid cllisins, define frbidden regins human interactin-related impse impedance r admittance in sme directin prvide haptic feedback fr teleperatin J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 8

9 Cnstraint-based cntrl Rts Ambler, Ppplestne (Artificial Intelligence 75)... specifying the gal psitin in assembly tasks using gemetric relatins between bjects O. Khatib (IJRR87) peratinal space frmulatin Y. Nakamura (IJRR86, Bk91) ptimizatin and redundancy reslutin Samsn, Le Brgne, Espiau (Bk91) task functin apprach J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 9

10 Cnstraint-based cntrl Other, parallel develpments: Stack-f-Tasks Inspired by/applied t whle-bdy manipulatin fr humanid rbts CNRS-LAAS, CNRS-LIRMM, CNRS-AIST JRL Mansard, Lamiraux, Stasse, Kheddar, Khatib, Chaumette et al. Architecture fr whle-bdy manipulatin fr humanid rbts Khatib, Sentis, Park (Stanfrd University), e.g. ICRA2006 J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 10

11 Cnstraint-based cntrl basic apprach (De Schutter et al. IJRR2007) P: plant : rbt + envirnment; C: cntrller; M+E: mdel update + estimatr cntrl input u: may als be desired acceleratins r trques J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 11

12 Task mdeling and cnstraint specificatin systematic apprach fr deriving expressins fr the task cnstraints lw-level cnstraint cntrllers are derived autmatically lcatin f frames is updated autmatically w: wrld : bject f: feature q: rbt crdinates Χ f : feature crdinates J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 12

13 Task mdeling and cnstraint specificatin J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 13

14 Task mdeling and cnstraint specificatin systematic apprach fr mdelling gemetric uncertainty estimatrs fr ff-line calibratin r n-line adaptatin are derived autmatically w: wrld : bject f: feature q: rbt crdinates Χ f : feature crdinates Χ u : uncertainty crdinates (e.g. calibratin values) J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 14

15 Cntrl and estimatin lwel-level cntrl: velcity-reslved (IJRR2007) cnstraint cntrller: y d = y d + K p y d y where y is measured r estimated and d refers t desired task cntrller ( generalized inverse kinematics ): Aq d= y d + BΧ u where A(q,Χ f,χ u ), B(q,Χ f,χ u ), and Χ u is estimated generalized inverse yields desired jint velcities: cnflicting cnstraints are handled by cnstraint pririties r cnstraint weights kinematic redundancy is slved by using weights in jint space J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 15

16 Cntrl and estimatin lwel-level cntrl: acceleratin-reslved (De Laet et al., KU Leuven internal reprt as addendum t IJRR2007) cnstraint cntrller: y d =y d + K v y d y + K p y d y task cntrller: generalized inverse kinematics is nw slved at acceleratin level yielding desired jint acceleratins using the desired jint acceleratins and the dynamic mdel f the rbt platfrm cntrl inputs u are btained at trque level slutin bth fr sft cntact and hard cntact J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 16

17 Cntrl and estimatin extensin: dealing with inequality cnstraints (... example slutin...) define safety zne befre the true cnstraint if the safety zne is entered, start a cnstraint cntrller with y d equal t the brder f the safety zne increase the weight f the cnstraint (e.g. expnentially) if the distance t the true cnstraint becmes smaller J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 17

18 Cntrl and estimatin medium-level task cntrller finite state machine activates/deactivates cnstraints assigns cnstraint pririties and/r cnstraint weights sets desired cnstraint values mnitrs the task executin based n the sensr readings and the measured r estimated task crdinates J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 18

19 Cntrl and estimatin estimatr updates all feature crdinates Χ f and estimates all cnstraint values y and uncertainty crdinates Χ u (+ time derivatives) prcess mdel fr the estimatr fllws frm the task mdeling, e.g. fr the velcity-reslved case and fr gemetric uncertainties at psitin/velcity/acceleratin level: J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 19

20 Recent applicatins 2007 simultaneus visual serving f multiple bjects adding rbt and cllisin cnstraints 2008 multi-mdal sensr-based cntrl: frce sensr, laser sensr, camera, laser scanner 2011 human-rbt cmanipulatin using PR2 > 30 cnstraints frce cntrller withut frce sensr J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 20

21 Recent applicatins 2015 quadrtr with shared cntrl: remtely cntrlled (frward/backward) with visual feedback t peratr lcal cllisin cntrl (US and infrared sensrs) additin f lcal yaw cntrl t pint camera t target 2015 exskeletn with cmpliant actuatrs bilateral-lwer limb exskeletn t assist sit-t-stand J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 21

22 Recent applicatins Cnstraint-based apprach is applied in several prjects: ROBOHOW.COG. EU-FP Factry-in-a-Day EU-FP MIRAD, spnsred by IWT (Flanders) J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 22

23 Discussin limitatins f the apprach in IJRR2007 cnstraint specificatin is uniquely based n (full 6D) kinematic lp equatins crdinate singularities if minimal crdinates are used mre general task mdeling apprach allwing general expressins and based n expressin graphs and autmatic differentiatin is presented in Aertbeliën et al. (IROS2014) lw-level task cntrller is velcity-reslved acceleratin-reslved and trque-based apprach was presented in De Laet et al. (internal reprt) limitatins f existing sftware implementatins see e.g. Aertbeliën et al. (IROS2014) fr a cmparisn J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 23

24 Discussin challenges fr (general-purpse) sftware implementatins large variety f systems and tasks ( skills ) rbt platfrms (tplgy, #dfs, kinematics, dynamics) sensr systems envirnments (e.g. sft/hard cntact) tasks (cnstraints, bjectives, pririties, etc.) lw-level cntrl appraches need fr flexible sftware envirnments t frmulate (different types f) cnstrained ptimizatin prblems chse apprpriate slvers: numerical + symblic (reasning) mnitr task executin using finite state machine cmpse cmplex systems (incl. skills ) frm subsystems make Dmain Specific Languages with well-defined and simple semantics fr cherent sets f applicatins t avid the need fr (re)writing cde fr every applicatin J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 24

25 Thanks... KU Leuven GOA/10/11-prject: Glbal real-time ptimal cntrl f rbts and mechatrnic systems Many clleagues and cllabratrs: Herman Bruyninckx, Erwin Aertbeliën, Wilm Decré, Nick Vanthienen, Gianni Brghesan, Enea Scini, Tine Lefebvre, Ruben Smits, Tinne De Laet, Jhan Rutgeerts, Rik Beliën, et al. J. De Schutter, A cnstraint-based apprach fr multi-mdal rbt cntrl 25