Vodenje redundantnega neholonomičnega mobilnega manipulatorja

Baumgartner, Jakob (author), Klančar, Gregor (mentor), Petrič, Tadej (co-mentor)

V številnih panogah si industrije brez podpore robotizacije v obliki manipulatorjev ne moremo več predstavljati. Manipulatorji so večinoma fiksno vpeti, saj lahko z delovnim dosegom učinkovito opravijo zahtevana opravila. V primeru zahtev po večjem dosegu pa je potrebno uporabiti mobilne manipulatorje, kjer je manipulator pritrjen na mobilno platformo. Slednje zahteva naprednejše algoritme za lokalizacijo in vodenje. V magistrskem delu smo rešili problem vodenja redundantnega neholonomičnega mobilnega manipulatorja. Uporabljali smo robotski sistem sestavljen iz mobilne platforme Pal Tiago Base, na kateri je bil nameščen robotski manipulator Panda Emika Franka. Za robotski sistem smo izdelali dva različna modela kinematike. Pri prvem modelu smo za vodenje sklepov mobilne platforme uporabili enačbe kinematike diferencialnega pogona. Pri drugem modelu pa smo mobilno platformo modelirali kot kombinacijo navideznega rotacijskega in navideznega translacijskega sklepa. Izdelali in preizkusili smo različne optimizacije za reševanje problema redundantnosti sestavljenega robotskega sistema. Za odpravo problema neholonomičnih omejitev pogona smo s pomočjo optimizacije kota med platformo in točko, mobilno platformo med vodenjem orientirali proti ciljni točki. Izdelali smo algoritem vodenja, ki smo ga preizkusili v simulacijskem in realnem okolju. Pri vodenju robota v realnem okolju smo meritve lege platforme in manipulatorja zajemali s pomočjo sistema OptiTrack. Za preizkus smo si zamislili dve različni poti točk, po katerih smo (v simulaciji) vodili našega robota. Ugotovili smo, da optimizacija manipulabilnosti vrha robota izboljša sledenje trajektoriji, vendar pa robot zahaja v limitne lege sklepnih vrednosti, ter posledično ne more nadaljevati svoje naloge. Z uporabo optimizacije za doseg želene lege sklepov smo rešili problem zahajanja sklepov v končne lege, poslabšali pa smo kakovost sledenja trajektoriji.

• Language: Slovenian
• Keywords: redundantni robot, direktna kinematika, inverzna kinematika, optimizacija, manipulabilnost, robotski manipulator, diferencialni pogon, neholonomične omejitve
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2022
• PID: 20.500.12556/RUL-140534
• COBISS.SI-ID: 121648387
• Publication date in RUL: 15.09.2022

Secondary language

• Language: English
• Title: Control of redundant nonholonomic mobile manipulator

Abstract

In many industries, it is no longer possible to imagine factories without the support of robotization in the form of robotic manipulators. The manipulators are mostly fixed, as they can efficiently perform the required tasks within their working reach. In the case of requirements for greater reach, it is necessary to use mobile manipulators, where the manipulator is attached to a mobile platform. The latter requires a more advanced localization and guidance algorithms. In the master’s thesis, we solved the problem of controlling a redundant non-holonomic mobile manipulator. We used a robotic system consisting of a Pal Tiago Base mobile platform, on which Emiko Frank's Panda robotic manipulator was installed. We created two different kinematics models for the robot system. In the first model, we used differential drive kinematics equations to guide the joints of the mobile platform. In the second model, we modelled the mobile platform as a combination of virtual rotational and virtual translational joints. We developed and tested various optimizations to solve the redundancy problem of the composite robot system. We oriented the mobile platform towards the target point while guiding the robot to solve the problem of non-holonomic limitations of the drive, by optimizing the angle between the platform and the point. We developed a guidance algorithm which we tested in a simulation and real environment. Measurements of the position of the platform and the manipulator were captured using the OptiTrack system, when guiding the robot in a real environment. For the test, we imagined two different paths of points along which we (in the simulation) guided our robot. We found that optimizing the manipulability of the top of the robot improves trajectory tracking but the robot enters the limit positions of the joint values, and as a result cannot continue its task. By using optimization to reach the desired position of the joints, we solved the problem of the joints moving into their final positions but worsened the quality of trajectory tracking.

• Keywords: redundant robot, kinematics, direct kinematics, inverse kinematics, optimization, manipulability, robotic manipulator, differential drive, nonholonomic constraints