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Robotics 2nd edition 2019 Tadej Bajd and Jadran

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Robotics 2nd edition 2019 Tadej Bajd and Jadran
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Preface

It is perhaps difficult to agree on what a robot is, but most people working in
robotics would probably quote the “Father of Robotics”, Joseph F. Engelberger
(1925–2015), a pioneer in industrial robotics, stating “I can’t define a robot, but I
know one when I see one”.
The word robot does not originate from a scientific or engineering vocabulary,
but was first used in the Czech drama “R.U.R.” (Rossum’s Universal Robots) by
Karel Čapek, that was first played in Prague in 1921. The word itself was invented
by his brother Josef. In the drama the robot is an artificial human being which is a
brilliant worker, deprived of all “unnecessary qualities”, such as emotions, creativity,
and the capacity for feeling pain. In the prologue of the drama the following
definition of robots is given: “Robots are not people (Roboti nejsou lidé). They are
mechanically more perfect than we are, they have an astounding intellectual
capacity, but they have no soul. The creation of an engineer is technically more
refined than the product of nature”.
The book Robotics evolved through decades of teaching robotics at the Faculty
of Electrical Engineering, University of Ljubljana, Slovenia, where the first textbook
on industrial robotics was published in 1980 (A. Kralj and T. Bajd,
“Industrijska robotika”). The way of presenting this rather demanding subject was
successfully tested with several generations of undergraduate students.
The second edition of the book continues the legacy of the first edition that won
the Outstanding Academic Title distinction from the library magazine CHOICE in
2011. The major feature of the book remains its simplicity. The introductory
chapter now comprehensively covers different robot classes with the main focus on
industrial robots. The position, orientation, and displacement of an object are
described by homogenous transformation matrices. These matrices, which are the
basis for any analysis of robot mechanisms, are introduced through simple geometrical
reasoning. Geometrical models of the robot mechanism are explained with
the help of an original, user-friendly vector description. With the world of the
roboticist being six-dimensional, orientation of robot end effectors received more
attention in this edition.
Robot kinematics and dynamics are introduced via a mechanism with only two
rotational degrees of freedom, which is however an important part of the most
popular industrial robot structures. The presentation of robot dynamics is based on
only the knowledge of Newton’s law and was additionally simplified for easier
understanding of this relatively complex matter. The workspace plays an important
role in selecting a robot appropriate for the planned task. The kinematics of parallel
robots is significantly different from the kinematics of serial manipulators and
merits additional attention.
Robot sensors presented in this edition are relevant not only for industrial
manipulators, but also for complex systems such as humanoid robots. Robot vision
has an increasingly important role in industrial applications and robot trajectory
planning is a prerequisite for successful robot control. Basic control schemes,
resulting in either the desired end-point trajectory or in the force between the robot
and its environment, are explained. Robot environments are illustrated by product
assembly processes, where robots are a part of a production line or operate as
completely independent units. Robot grippers, tools, and feeding devices are also
described.
With the factory floor becoming ever more complex, interaction between
humans and robots will be inevitable. Collaborative robots are designed for safe
human-robot interaction. Flexibility of production can be further increased with the
use of wheeled mobile robots. A glimpse into the future, when humans and robots
will be companions, is presented in the chapter on humanoid robotics, the complexity
of which requires more advanced knowledge of mathematics. The chapter
on standardization and measurement of accuracy and repeatability is of interest for
users of industrial robots.
The book requires a minimal advanced knowledge of mathematics and physics.
It is therefore appropriate for introductory courses in robotics at engineering faculties
(electrical, mechanical, computer, civil). It could also be of interest for
engineers who had not studied robotics, but who have encountered robots in the
working environment and wish to acquire some basic knowledge in a simple and
fast manner.

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Robot Manipulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Industrial Robotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Homogenous Transformation Matrices . . . . . . . . . . . . . . . . . . . . . . 11
2.1 Translational Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Rotational Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 Pose and Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 Geometrical Robot Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3 Geometric Description of the Robot Mechanism . . . . . . . . . . . . . . . 27
3.1 Vector Parameters of a Kinematic Pair . . . . . . . . . . . . . . . . . . . 27
3.2 Vector Parameters of the Mechanism . . . . . . . . . . . . . . . . . . . . 31
4 Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5 Two-Segment Robot Manipulator . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.1 Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.2 Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
5.3 Workspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.4 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6 Parallel Robots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.1 Characteristics of Parallel Robots . . . . . . . . . . . . . . . . . . . . . . . 69
6.2 Kinematic Arrangements of Parallel Robots . . . . . . . . . . . . . . . 73
6.3 Modelling and Design of Parallel Robots . . . . . . . . . . . . . . . . . 78
7 Robot Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
7.1 Principles of Sensing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
7.2 Sensors of Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
7.2.1 Placing of Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
7.2.2 Potentiometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
7.2.3 Optical Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
7.2.4 Magnetic Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.2.5 Tachometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.2.6 Inertial Measurement Unit. . . . . . . . . . . . . . . . . . . . . . 94
7.3 Contact Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.3.1 Tactile Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.3.2 Limit Switch and Bumper . . . . . . . . . . . . . . . . . . . . . . 98
7.3.3 Force and Torque Sensor . . . . . . . . . . . . . . . . . . . . . . 98
7.3.4 Joint Torque Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . 101
7.4 Proximity and Ranging Sensors . . . . . . . . . . . . . . . . . . . . . . . . 102
7.4.1 Ultrasonic Rangefinder . . . . . . . . . . . . . . . . . . . . . . . . 102
7.4.2 Laser Rangefinder and Laser Scanner . . . . . . . . . . . . . 103
8 Robot Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
8.1 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
8.2 Forward Projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
8.3 Backward Projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
8.3.1 Single Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
8.3.2 Stereo Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
8.4 Image Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
8.5 Object Pose from Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
8.5.1 Camera Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
8.5.2 Object Pose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
9 Trajectory Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
9.1 Interpolation of the Trajectory Between Two Points . . . . . . . . . 123
9.2 Interpolation by Use of via Points . . . . . . . . . . . . . . . . . . . . . . 126
10 Robot Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
10.1 Control of the Robot in Internal Coordinates . . . . . . . . . . . . . . 134
10.1.1 PD Control of Position . . . . . . . . . . . . . . . . . . . . . . . . 135
10.1.2 PD Control of Position with Gravity Compensation . . . 136
10.1.3 Control of the Robot Based on Inverse Dynamics . . . . 137
10.2 Control of the Robot in External Coordinates . . . . . . . . . . . . . . 141
10.2.1 Control Based on the Transposed Jacobian Matrix . . . . 142
10.2.2 Control Based on the Inverse Jacobian Matrix . . . . . . . 143
10.2.3 PD Control of Position with Gravity Compensation . . . 144
10.2.4 Control of the Robot Based on Inverse Dynamics . . . . 144
10.3 Control of the Contact Force . . . . . . . . . . . . . . . . . . . . . . . . . . 147
10.3.1 Linearization of a Robot System Through Inverse
Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
10.3.2 Force Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
11 Robot Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
11.1 Robot Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
11.2 Robot Peripherals in Assembly Processes . . . . . . . . . . . . . . . . . 158
11.2.1 Assembly Production Line Configurations . . . . . . . . . . 158
11.3 Feeding Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
11.4 Conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
11.5 Robot Grippers and Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
12 Collaborative Robots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
12.1 Collaborative Industrial Robot System . . . . . . . . . . . . . . . . . . . 173
12.2 Collaborative Robot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
12.3 Collaborative Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
12.3.1 Safety-Rated Monitored Stop . . . . . . . . . . . . . . . . . . . 178
12.3.2 Hand Guiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
12.3.3 Speed and Separation Monitoring . . . . . . . . . . . . . . . . 180
12.3.4 Power and Force Limiting . . . . . . . . . . . . . . . . . . . . . 181
12.4 Collaborative Robot Grippers . . . . . . . . . . . . . . . . . . . . . . . . . 184
12.5 Applications of Collaborative Robotic System . . . . . . . . . . . . . 185
13 Mobile Robots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
13.1 Mobile Robot Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
13.2 Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
13.2.1 Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
13.2.2 Path Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
13.2.3 Path Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
14 Humanoid Robotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
14.1 Biped Locomotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
14.1.1 Zero-Moment Point . . . . . . . . . . . . . . . . . . . . . . . . . . 211
14.1.2 Generation of Walking Patterns . . . . . . . . . . . . . . . . . . 213
14.2 Imitation Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
14.2.1 Observation of Human Motion and Its Transfer
to Humanoid Robot Motion . . . . . . . . . . . . . . . . . . . . 217
14.2.2 Dynamic Movement Primitives . . . . . . . . . . . . . . . . . . 221
14.2.3 Convergence Properties of Linear Dynamic
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
14.2.4 Dynamic Movement Primitives for Point-to-Point
Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
14.2.5 Estimation of DMP Parameters from a Single
Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
14.2.6 Modulation of DMPs . . . . . . . . . . . . . . . . . . . . . . . . . 227
15 Accuracy and Repeatability of Industrial Manipulators . . . . . . . . . 231
Derivation of the Acceleration in Circular Motion . . . . . . . . . . . . . . . . . . 243
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247