2018

Possible Final Examination Questions

Robotics CSCE 574

1) Describethethreemainrobotarchitecturesprovidingforeachofthemanexample.

2) Definewhatmiddlewareis.

3) Showhowtwonodes(onepublisherandonesubscriber)interactwitheachotherinROS.

4) DescribethecoreelementsinROS.

5) DefineROStopics,services,andactions,andwhenismoreappropriatetouse

eachofthem.

6) Definethetermsexteroceptiveandproprioceptivesensors.Providetwoexamplesforeach.

7) Listandcomparethreedifferentrangesensorsintermsofeaseofuse,accuracy,computationalcost,andenergycost.

8) WhatarethedifferencesbetweenHydraulicdriveandShapeMemoryAlloydrive?Nameoneapplicationinwhicheachoneofthemisappropriate.

9) WhatarethedifferencesbetweenHydraulicdriveandPneumaticdrive?Nameoneapplicationinwhicheachoneofthemisappropriate.

10) WhatarethedifferencesbetweenHydraulicdriveandElectricaldrive?Name

oneapplicationinwhicheachoneofthemisappropriate.

11) WhatarethedifferencesbetweenPneumaticdriveandShapeMemoryAlloy

drive?Nameoneapplicationinwhicheachoneofthemisappropriate.

12) WhatarethedifferencesbetweenElectricaldriveandShapeMemoryAlloy

drive?Nameoneapplicationinwhicheachoneofthemisappropriate.

13) WhatarethedifferencesbetweenPneumaticdriveandElectricaldrive?Nameoneapplicationinwhicheachoneofthemisappropriate.

14) Defineforwardkinematicsandinversekinematics.

15) Foradifferentialdriverobot,wherethewheelsaredistancedapartandthe

wheelvelocitiesareVlandVr.EstimatethelinearvelocityVandtheangularvelocityω .

16) InaPIDcontrollerwithgainsKp,KiandKd:describewhichquantityeachone

ofthemiscontrolling.Describealsotheeffectsofchangingeachgain.

17) Whenaproportionalcontrollertriestofollowthestepfunction(y=1:x<0.5;

y=1.5:x>0.5)describethepossiblecausesfortheresponseshownhere:

18) Whenaproportionalcontrollertriestofollowthestepfunction(y=1:x<0.5;y=1.5:x>0.5)describethepossiblecausesfortheresponseshownhere:

19) DescribetwoproblemswithEuleranglesforrepresentingrotationsin3D:

20) Pleaseperformthefollowingmatrixmultiplication:

𝐴𝐵 = 𝑎 𝑏 𝑐𝑑 𝑒 𝑓

𝑘 𝑙𝑚 𝑛𝑜 𝑝

=

21) DefineSimultaneousLocalizationandMapping(SLAM)andexplainwhatarethemainchallenges:

22) Whatarethedifferencesbetweentopologicalandgridbasedmaps?Namean

applicationforeachone.

23) Whatarethedifferencesbetweentopologicalandfeaturebasedmaps?Name

anapplicationforeachone.

24) Whatarethedifferencesbetweenfeatureandgridbasedmaps?Nameanapplicationforeachone.

25) Describetwodifferenttypesofinaccuracythatcanresultfromusingthesonarsensor.

26) Defineandcompare“GlobalLocalization”and“Tracking”.

27) Defineandcompare“GlobalLocalization”and“KidnappedRobotProblem”.

28) Defineandcompare“KidnappedRobotProblem”and“Tracking”.

29) ForaBayesianFilter:

SimplifytheequationusingtheMarkovproperty,thetheoremoftotalprobabilityandBayesruletogetto:

30) Onemajorcomponentofthe“ParticleFilter”algorithmisresampling.Provideabriefdescription.Whatisthemaingoaloftheresamplingstep?

31) ProvideabriefdescriptionoftheParticleFilterstateestimationalgorithm.Explainhowthe:Propagate,Update,andResamplingstepswork.

i at time actions are and i at time nsobservatio are where),...,,,,|()( 0211

ii

tttttt

aooaoaoxpxBel −−−=

Bel(xt ) =ηp(ot | xt ) p(xt | xt−1,at−1)∫ Bel(xt−1)dxt−1

where:

Bayes Rule : p(a | b) = p(b | a)p(a)p(b)

you can assume :η =1/ p(oi | at−1,…,o0 )

32) Inthefollowingaparticlefilterisusedtotrackthepositionoftherobotinatwodimensionalenvironment,withnoiseintranslation(xaxis)andinlateraldrift(yaxis).Thetwopicturesidentifytwodifferentinstancesofusingsuchaparticlefilterforarobotthatgoesforwardof100cmalongthexaxis.Whyisthereadifferencebetweenthetwoinstances?

33) Assumethatthestateoftherobotisthepositionxandy.Inthefollowingpicture,depictingaparticlefilteronanenvironmentforlocalizingarobotdenotedwithanasterisk,pleasedrawtheareaswhereaftertheupdateparticleswillhavetheweightincreased.Therobotcansensethedistancefromthewallsasshowninthepicture.

34) WhatisCooperativeLocalization?

35) ForaKalmanfilterestimatorprovideasmallexplanationaboutthefollowing

equations:S=H*P*HT+R

WhereHisthemeasurementfunctionmatrixPthecovariancematrixbeforetheupdateandRisthesensorserrorcovariancematrix.

36) Foramobilerobotwhoseestimatedmotionisdescribedby:

. anditsrealmotionisdefinedas:

Derivetheerror:

usingsmallangleapproximation.

37) WhenusinganindirectEKFtheerrorinthestateofamobilerobotisdescribedbythefollowingequation:.

.

whereWiszeromeanGaussiannoise,andthecovariancePisdefinedas:

DerivetheequationofthecovarianceasafunctionofFtandGt

38) Consideravehicletravellingwithlinearvelocityvandangularvelocityωaffectedbynoisewvandwωrespectively.Therefore,themeasuredvelocitiesare:𝑣!𝜔!

=𝑣! + 𝑤!𝜔! + 𝑤!

Therealposeofthevehicleisxt=[xt,yt,θt ]T;andtheestimatedposeis𝒙𝒕 = 𝑥𝒕 𝑦𝒕 𝜃𝒕 𝑻

Providetheequationsfortimet+1fortherealpose:

tw

twVyy

twVxx

t

t

t

ttt

tVttt

tVttt

δωφφ

φδ

φδ

ω )(ˆˆ

ˆsin)(ˆˆ

ˆcos)(ˆˆ

1

1

1

++=

++=

++=

+

+

+

111 ˆ~+++ −= ttt xxx

ttVyytVxx

ttt

tttt

tttt

δωφφ

φδ

φδ

+=

+=

+=

+

+

+

1

1

1

sincos

ttttt WGXFX +=+

~~1

]~~[ 11/1Ttttt XXEP +++ =

𝒙!!! =𝑥!!!𝑦!!!𝜃!!!

=

andtheestimatedpose:

𝒙!!! =𝑥!!!𝑦!!!𝜃!!!

=

asafunctionofthepreviouspose,therealvelocities,andthenoise.

39) WhatistheiterativeKalmanFilter?

40) IntheSLAMexperimentshowninthefollowingimagedescribethereason

forthedifferenceinthelocationuncertaintybetweentheAandBlandmark

A

B

41) DefineOpticalFlow

42) Definetheapertureproblem

43) Whatisthebaselineinastereocamera?

44) Whatisthedifferencebetween“OpticalFlow”and“SceneMotion”?

45) DescribetheGeneralizedVoronoiGraph(GVG)explorationalgorithm.

Outlinethemajorsteps:

46) Foranoutdoorrobot,describeatleast3costparametersaffectingpath

planning.

47) Foranindoorrobot,describeatleast3costparametersaffectingpath

planning.

48) DefinethetermsC-Space(configuration),FreeSpace,Semi-FreeSpace,andC-Obstaclespace.Whenaretwopathshomotopic?

49) Describethedifferencesbetweenthe“ProbabilisticRoadmap”(PRM)andthe“RapidlyExploringRandomTree”(RRT)pathplanners:

50) Whatistheguidingprinciplesbehind:a)visibilitygraphandb)generalizedVoronoigraphpathplanningalgorithms?Whatisthemajordifferencebetweenthetwoalgorithms?

51) FortheBug2algorithmwhatistheminimumsetofsensorsneeded.

52) Definethemainideabehindpotentialfieldpathplanning.Whatisitsmaindisadvantage?Describethemostcommontechniquetoovercomeit:

53) Foratwo-linkmanipulator,withtworevolutejoints,eachrotating[0,360]degrees,whatistheconfigurationspace.Drawarepresentation.

54) Whataretheadvantages/disadvantagesofmulti-robotsystems?

55) Describetwodifferentstrategiesformulti-robotformation.

56) DefineMarsupialRobots.

57) DescribetheAuctionmechanismfortaskdistributioninmulti-robotsystems.

58) DrawtheReebgraphandaplausibleoptimalorderofcellcoverageforthefollowingenvironment.Hint:Remembertodoublecertainedges.Startposition:topleftcorner.

59) UsetheWavefrontplanneronthefollowingworld,startingat“0”:

0

60) Usingthepinholecameramodelderivetherelationshipbetween(x,y)and(X,Y,Z).

x=

y=

61) DrawthepathusedbytheBug1algorithmfromStarttoGoal.

Start

Goal

62) DrawthetrajectoryfortheBug2pathplanningalgorithm,startingposition

therobotgoalthestar.Consideraleftturningrobot.

63) Drawthevisibilitygraphinthefollowingenvironment.Drawalsothe

shortestpaththroughthevisibilitygraphfromStarttoGoal.

Start

Goal

64) DescribetheFrontierbasedexplorationalgorithm.

65) Discussthedilemmabetweenexploitation(localization)andexplorationof

newterritoryinanyexplorationandmappingalgorithm.Inparticular,consideraccuracyandefficiency.

66) Whatisthedifferencebetweendeterministicandrandomcoveragealgorithms?Giveanexampleofanapplicationwhicheachtypeismoresuitedforandjustifyyourselection.

67) Usethegrassfiretransformtocreatetheconfigurationspaceonthefollowingworld,dilatingtheobstaclesby2pixel.Istheresultingspaceconnected?