Title Upravljanje četveronožnim robotom Dynarobin po neravnom terenu Title (english) Control of Quadruped Robot Dynarobin on Uneven Terrain Author Alexandar Arambašić Mentor Zdenko Kovačić (mentor)Committee member Zdenko Kovačić (predsjednik povjerenstva)Committee member Stjepan Bogdan (član povjerenstva)Committee member Matko Orsag (član povjerenstva)Granter University of Zagreb Defense date and country 2016-09-29, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Cilj ovog rada je izrada upravljačkih algoritama za gibanje četveronožnog hodača Dynarobin po različitim vrstama neravnina, odnosno prepreka. Na početku je dan opis robota Dynarobin. Robot je pogonjen motorima Dynamixel, a na svakoj nozi ima senzor sile. Na tijelu robota nalazi se upravljački sustav koji se sastoji od \textit{Odroid} računala ("On-board computer-OBC"), upravljačke ploče za motore („Motor controler board - MCB“) te IMU jedinicu \textit{AHRS} („IMU – Inertial measurement unit“).
Nadalje je opisan koncept upravljanja robotom pomoću simulatora unutar Matlab/Simulink okruženja. Robotom se upravlja koristeći upravljačke algoritme razvijene pomoću Stateflow alata za izradu automata stanja. Unutar upravljačkog algoritma pozivaju se razne funkcije napisane u Matlabu, kao na primjer funkcija za izvođenje trajektorija ili pak funkcija za određivanje kuta trajektorija. Prilikom nailaska na prepreku koriste se tri izvedbe regulatora kako bi se upravljalo pozom robota. Upravljanje pozom robota bitno je zbog korekcije kuteva poniranja i valjanja tijela robota, odnosno cilj je dovesti te kuteve blizu nule prilikom penjanja na prepreku. Upravljački algoritam 1 bazira se na korekciji kuta poniranja, dok se upravljački algoritam 2 bazira na korekciji kuta valjanja.
Prve dvije inačice regulatora su P regulatori koji se primjenjuju na blok "Inverzna kinematika tijela robota" definiran na Jakobijanu. Blok inverzne kinematike ostvaruje upravljanje pozom robota na način da se zadaju referentne brzine tijela robota na ulaz bloka, translacijske i rotacijske brzine. Treća inačica regulatora je P regulator koji je spojen direktno na Stateflow upravljački algoritam i služi korekciji z koordinate određenih nogu te se na taj način direktno upravlja pozom robota bez posredstva bloka inverzne kinematike.
Upravljanje modelom robota u simulaciji izvedeno je pomoću sve tri inačice regulatora, dok je na stvarnom robotu izvedeno upravljanje samo pomoću treće inačice regulatora, s obzirom da su se odzivi inverzne kinematike pokazali nezadovoljavajućima pri korištenju na stvarnom robotu. U svim simulacijama odzivi kuta poniranja i kuta valjanja osciliraju blizu nule što pokazuje efikasnost algoritama upravljanja u simulaciji. U pokusima na stvarnom robotu odzivi kuteva poniranja i valjanja tijela robota pokazali su se zadovoljavajućima, međutim zbog mnoštva praktičnih problema(centar mase nije idealno pozicioniran, česti su trzaji prilikom gibanja itd.), gibanje nije idealno te tu postoje mogućnosti unaprijeđenja algoritama kako bi gibanje bilo glađe i kontinuiranije.
Abstract (english) The goal of this paper is to create control algorithms for locomotion of the quadrapedal robot Dynarobin on different uneven terrains, that is obstacles. In the beginning the description of the Dynarobin robot is given. The robot is actuated with Dynamixel motors and there is a force sensor on each foot. Control system consisting of an \textit{Odroid} computer ("On-board computer-OBC"), motor controler board („MCB“) and IMU unit called \textit{AHRS} („IMU – Inertial measurement unit“) is placed on the robot body.
Further more, the concept of controlling robot using simulator in Matlab/Simulink environment is described. Robot is controlled with control algorithms developed using Stateflow tool for creating state machine. Inside control algorithm, different functions created in Matlab are called, for example function for trajectory execution or function for calculating trajectory angle. Three different controller versions are used when facing obstacles, used for control of a robot pose. Controlling a robot pose is important because pitch and roll angles need to be corrected when climbing on an obstacle, the goal is for pitch and roll angle to be as close to zero as possible. Control algorithm 1 is based on correcting pitch angle, while control algorithm 2 is based on correcting roll angle.
First two types of controllers are P controllers which are applied to the "Inverse kinematics of the robot body" block defined on Jacobian. The inverse kinematics block controls robot pose by giving speed references of the robot body on the input of the block, translational and rotational speeds. The third type of controller is P controller connected directly onto Stateflow control algorithm and is used to correct z coordinate of the specific legs and in that way the pose of the robot is controlled directly without the use of the inverse kinematics block.
Control of the robot model in simulation is done using all three types of controller, but on a real robot only the third type of controller is applied because the inverse kinematics block responses on a real robot are unsatisfying. In all simulations pitch and roll angle responses are oscillating close to zero which shows the efficiency of the algorithms in simulations. In the real robot tests, pitch and roll responses are satisfying, but due to lots of practical issues(the center of mass is not ideally positioned, twitches are common during movement, etc.), the motion is not ideal and there is room for improvement of the algorithms so that the motion is smoother and more continuous.
Keywords
Četveronožni hodač
Dynarobin
Matlab/Simulink
Stateflow
pitch kut
roll kut
automat stanja
upravljački algoritam
prepreka
kosina
stanje
prijelaz
P regulator
ROS
detekcija prepreke
Catmull-Rom
Keywords (english)
Quadruped robot
Dynarobin
Matlab/Simulink
Stateflow
pitch angle
roll angle
state machine
control algorithm
obstacle
slope
state
transition
P controller
ROS
obstacle detection
Catmull-Rom
Language croatian URN:NBN urn:nbn:hr:168:706027 Study programme Title: Electrical Engineering and Information Technology Type of resource Text File origin Born digital Access conditions Closed access Terms of use Public note Created on 2018-02-06 07:38:07
