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Institut für Regelungs- und Automatisierungstechnik
1
Michael Hofbaur Modular Machines
Modular Machines-
reconfigurable mobile robots for research and education
Michael Hofbaur
Institut für Regelungs- und AutomatisierungstechnikTechnische Universität Graz
Institut für Regelungs- und Automatisierungstechnik
2
Michael Hofbaur Modular Machines
Motivation
Robot drives with diverse wheel-geometry and drive-functionality
Teaching• Hands-on experience with diverse drives• Verify and understand robot kinematics
Research• Investment costs / re-usable hardware• Novel, but still generic drive concepts
Industrial Application• Easy configuration • Fault tolerance
Institut für Regelungs- und Automatisierungstechnik
3
Michael Hofbaur Modular Machines
Motivation
Robot drives with diverse wheel-geometry and drive-functionality
Institut für Regelungs- und Automatisierungstechnik
4
Michael Hofbaur Modular Machines
Motivation
Robot drives with diverse wheel-geometry and drive-functionality
Institut für Regelungs- und Automatisierungstechnik
5
Michael Hofbaur Modular Machines
Motivation
Robot drives with diverse wheel-geometry and drive-functionality
Institut für Regelungs- und Automatisierungstechnik
6
Michael Hofbaur Modular Machines
Modular Mobile Robot
Goal: quickly build/configure diverse wheeled robot drives
Innovative Design: – 6-edge honey-comb prism– Module-in-Module design
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Application: Teaching & Research
Toolbox for diverse robots/applications
• cost-effective starter-kit• expandable• re-usable• versatile configurations for
research & education• new perspectives & coole ideas
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Robot Control
How do we operate / control robots with diverse wheel configurations and geometries?
Keyword: kinematics / inverse kinematics
RxRy
R 1 1
2 2
3 3
,R
R R
R
x
y
Drive Command Wheel Setpoints
Institut für Regelungs- und Automatisierungstechnik
9
Michael Hofbaur Modular Machines
Robot Control
How do we operate / control robots with diverse wheel configurations and geometries?
Keyword: kinematics / inverse kinematics
1 1
2 2
3 3
,R
R R
R
x
y
Drive Command Wheel Setpoints
VIDEOwheel_view_of_gamepad_drive_short.avi
Institut für Regelungs- und Automatisierungstechnik
10
Michael Hofbaur Modular Machines
Model-programmed Robot Drive Control
instead of using the (manually) derived inverse-kinematics for a drive we:
• specify a model that captures the drive‘s geometry and functionality • analyze the kinematics and deduce the inverse-kinematics
on-line during operation of the robot
Institut für Regelungs- und Automatisierungstechnik
11
Michael Hofbaur Modular Machines
Model-programmed Robot Drive Control
instead of using the (manually) derived inverse-kinematics for a drive we:
• specify a model that captures the drive‘s geometry and functionality • analyze the kinematics and deduce the inverse-kinematics
on-line during operation of the robot
Complete Architecture
• Kinematics Reasoning
• Monitoring & Diagnosis
• Coordinated Control
• Model / autom. Modelling
higher-level Robot Control - Path and Task Planning & Execution OR Robot Cluster Control
Coordinated Control Unit
Kinematics Reasoning Unit
Hybrid Monitoring& Estimaton Unit
AutomatedHybrid
ModellingUnit
Drive UnitHandler
Drive UnitHandler
Drive UnitHandler
.......... Drive FrameHandler
Drive Unit1
Drive Unit2
Drive Unitn
RobotSensors
Drive Unit Network
higher-level Robot Network
Institut für Regelungs- und Automatisierungstechnik
12
Michael Hofbaur Modular Machines
Model-programmed Robot Drive Control
instead of using the (manually) derived inverse-kinematics for a drive we:
• specify a model that captures the drive‘s geometry and functionality • analyze the kinematics and deduce the inverse-kinematics
on-line during operation of the robot
Complete Architecture
• Kinematics Reasoning
• Monitoring & Diagnosis
• Coordinated Control
• Model / autom. Modelling
higher-level Robot Control - Path and Task Planning & Execution OR Robot Cluster Control
Coordinated Control Unit
Kinematics Reasoning Unit
Hybrid Monitoring& Estimaton Unit
AutomatedHybrid
ModellingUnit
Drive UnitHandler
Drive UnitHandler
Drive UnitHandler
.......... Drive FrameHandler
Drive Unit1
Drive Unit2
Drive Unitn
RobotSensors
Drive Unit Network
higher-level Robot Network
Institut für Regelungs- und Automatisierungstechnik
13
Michael Hofbaur Modular Machines
Model-programmed Robot Drive Control
MODEL:• specifies the drive‘s geometry and functionality
Institut für Regelungs- und Automatisierungstechnik
14
Michael Hofbaur Modular Machines
Kinematics Analysis
Wheel geometry & functionality constrains the possible movements of the robot: it defines its Kinematics
3
R
R R
R
x
y B
Example 1: omnidirectional 3-wheel robot
admissible & controllable movements B
Institut für Regelungs- und Automatisierungstechnik
15
Michael Hofbaur Modular Machines
Kinematics Analysis
3
R
R R
R
x
y B
Example 2: differential-drive robot with steered front wheel
admissible & controllable movements B
Wheel geometry & functionality constrains the possible movements of the robot: it defines its Kinematics
Institut für Regelungs- und Automatisierungstechnik
16
Michael Hofbaur Modular Machines
Kinematics Analysis
Wheel geometry & functionality constrains the possible movements of the robot: it defines its Kinematics
3R
R R
R
x
y B
Example 2: differential-drive robot with steered front wheel
admissible & controllable movements B
Institut für Regelungs- und Automatisierungstechnik
17
Michael Hofbaur Modular Machines
Kinematics Analysis
Wheel geometry & functionality constrains the possible movements of the robot: it defines its Kinematics
Example 2: differential-drive robot with steered front wheel
admissible & controllable movements B
Institut für Regelungs- und Automatisierungstechnik
18
Michael Hofbaur Modular Machines
Kinematics Analysis
Wheel geometry & functionality constrains the possible movements of the robot: it defines its Kinematics
Example 3: robot with two standard wheels and a steered front wheel
admissible & controllable movements B
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Kinematics Reasoning Unit
on-line kinematics solver that computes B and allows:
• variable robot geometry– geometry & number of wheels can change during operation
• variable drive functionality– operational- and fault modes
• self-awareness– drive explicitely knows the space of
possible movements for the drive (B)
– validate a drive command from higher level control
– reconfiguration
?R B
*R R
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Kinematics Reasoning Unit
on-line solver for robot kinematics:assumption: drive with unsteered wheels
[sin( ) cos( ) cos( )] 0
[cos( ) sin( ) sin( )] 0
i i i i i i R i i R i i
i i
Ti
i i i RT
i R i
l r r
l
j
c
rolling constraint for wheel i:
sliding constraint for wheel i:
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Kinematics Reasoning Unit
1 2
1
roll : 0
slide: 0
R
R
J
C
J
Combination of the constraints for all wheels:
on-line solver for robot kinematics:assumption: drive with unsteered wheels
Institut für Regelungs- und Automatisierungstechnik
22
Michael Hofbaur Modular Machines
admissible movements:
controllable movements:
admissible & controllable movements:
Kinematics Reasoning Unit
1( )Z Kern C
1( ), ( )T
S Kern S Kern JS
B Z S
Z
SB
Z S
on-line solver for robot kinematics:assumption: drive with unsteered wheels
1 2
1
roll : 0
slide: 0
R
R
J
C
J
Combination of the constraints for all wheels:
Institut für Regelungs- und Automatisierungstechnik
23
Michael Hofbaur Modular Machines
admissible movements:
controllable movements:
admissible & controllable movements:
Kinematics Reasoning Unit
1( )Z Kern C
1( ), ( )T
S Kern S Kern JS
B Z S
Z
SB
Z S
on-line solver for robot kinematics:assumption: drive with unsteered wheels
1 2
1
roll : 0
slide: 0
R
R
J
C
J
Combination of the constraints for all wheels:
How can we apply this line of reasoning to steered wheels, faults, etc.
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
admissible movements:
controllable movements:
admissible & controllable movements:
Kinematics Reasoning Unit
Qualitative rolling & sliding constraints for steered wheels
B Z S
1 1Mode
sin( ) sin( / 2)
OK cos( ) cos( / 2) 0 0 0
cos(0) cos( / 2)
cos( ) cos( / 2)
rot. stuck 0 0 0 sin( ) sin( / 2)
sin(0) sin( / 2)
free spinning 0 0 0 0 0 0
T Tq
T
T
q
l l
l l
j c
1q( )Z Kern C
1q( ), ( )T
S Kern S Kern JS
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
(Re)Configuration & Control
Example: Eye-Catcher Task
desired behaviour
Fault-szenario (blocked steering in one wheel)with reconfiguration
VIDEOeye-catcher_wo_fault.avi
VIDEOeye-cather_w_cool_reconf.avi
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Virtual rekonfiguration of the drive geometry
Coordinated control of Multi-Robot Systems
Basis for control is a model ofthe drive geometry that can changeduring operation of the robot
(Re)Configuration & Control
VIDEOdrivemovie1.avi
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Drive modules as wheel-units for an automated guided vehicle:
• flexible – easy configuration of mechanics & control
• costs - standard-units
• robust - modules replaceable
• new perspectives– multi-robot transport
– direkt objekt transport
Application: Automated Guided Vehicles
Institut für Regelungs- und Automatisierungstechnik
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Michael Hofbaur Modular Machines
Modular Machines - Summary
Hardware
• Patent-pending modular robot design to realize wheeled robots with diverse drive geometries
• Module-in-module design – extend your robots with additional modules to meet demanding research requirements
• Multi-robot (re)configuration
Software / Control
• Model-programmed self-configuring kinematics control • Real-time kinematics analysis• Health monitoring/diagnosis for fault tolerant operation
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