École de technologie supérieure (ÉTS)
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- The Control and Robotics
Laboratory at the École de technologie supérieure (ÉTS) in Montreal regroups
more than 30 members, four of which are professors. Working jointly with
industry and various research centers, CoRo concentrates its activities on
applied research. The laboratory is equipped with the state-of-the-art
infrastructure, including several industrial robots, a robot arm, a laser
cutting machine, various parallel robot prototypes, microscopes, and a wide
range of metrology instruments.
- The CoRo laboratory’s research efforts are focused on
the following areas:
- Precision robotics
- Parallel robotics
- Mechatronics and haptics
- Most users of robot manipulators in an industrial
setting are content with the excellent repeatability of their movements.
Today, an industrial robot’s effector can reach a previously taught pose
(position and orientation) with a position error below 0.1 mm. However, in
some applications, the poses to be attained are computed rather than taught,
in which case absolute accuracy is also required.
The most cost-effective way of improving the absolute accuracy of robots is
through calibration. While various commercial solutions are indeed available
for calibrating robots using metrology devices, the fact is that even the
least expensive of them still cost several thousand dollars. Furthermore,
for various reasons, these solutions do not meet the needs of all users
(lack of space in a robotic cell, lack of budget to buy a three-dimensional
measurement device, etc.).
While the aerospace sector is probably the most demanding in terms of
precision robotics, it is paradoxically also the least well served. This
sector has a particularly pronounced and active presence in the Montreal
region, where several international companies, including Pratt & Whitney, GE
Aviation, Messier-Dowty, L-3 MAS and Bombardier Aerospace, use industrial
robots for precision tasks.
Development of robot calibration methods
The CoRo laboratory is equipped with a wide range of metrology devices:
The laboratory is also equipped with two serial as well as several parallel robots. Robot calibration projects consist essentially in using measurement devices and mechanical artefacts to optimize the absolute accuracy of a robot. This type of research work requires a very strong mathematical background, and knowledge of robot kinematics and optimization methods.
three-dimensional measuring machine (Mitutoyo)
- laser interferometer system (Renishaw)
- laser tracker (Faro)
- measuring arm (Faro)
- ballbar (Renishaw)
- probe (Renishaw)
The first method developed at the CoRo laboratory is based on the use of a laser tracker to calibrate a classical six-degrees-of-freedom serial robot. Experimental work was carried out on an ABB IRB 1600 robot, and its maximum positioning error in its entire workspace was reduced to below 0.850 mm. Measurements were conducted automatically by controlling the laser tracker and the robot through a local Ethernet network, from Matlab.
A second method has been developed to calibrate one of the parallel robots designed at the laboratory, PreXYT, using a measuring arm (or any 3D coordinate measuring machine). This robot’s maximum positioning error has been reduced to below 0.050 mm.
Other calibration approaches have also been explored, including the calibration of serial robots using a probe, and the calibration of a Moog hexapod using a laser tracker.
The CoRo laboratory is currently exploring the use of C-Track, a dual-camera measurement device by the Quebec manufacturer, Creaform. This optical device allows the real-time measurement of the robot's effector pose, and can thus possibly be used not only to calibrate robots, but also to guide them dynamically.
Calibration of a serial robot with a laser tracker
Calibration of a parallel robot with a measurement arm
- In addition to the ubiquitous serial industrial
robots, other types of manipulators are also available, called parallel
robots. A serial robot is basically a series of links connected by motorized
joints, while a parallel robot is comprised of several series of links, with
most of their joints not motorized.
Parallel robots can be faster, more rigid and/or accurate than serial
robots. Like almost all motion simulators, most rapid pick-and-place robots
are parallel robots. Many precise positioning devices are also parallel
Through his website ParalleMIC and his research on the kinematic analysis
and design of parallel mechanisms, Professor Ilian Bonev is renowned in the
area of parallel robotics. He leads most of the R&D work involving parallel
robots conducted at the CoRo laboratory, where the work breaks down into
three categories: theoretical work, mechanical design and simulation
The following are the main theoretical areas Professor Bonev is interested
- study of the singularities and workspace of parallel robots;
- geometric design of new parallel mechanisms with large workspace and few
At the practical level, Professor Bonev is mainly interested in the mechanical design of new parallel robots with large workspace and high absolute accuracy (see Precision Robotics section) or for very specific applications. In both cases, industrial grade prototypes are designed and produced at the ÉTS. The controllers for these prototypes are generally developed by Professor Pascal Bigras (see Control section).
The robots are designed using CATIA, SolidWorks and ADAMS software. Parts are machined at the Laboratoire institutionnel de fabrication de l’ÉTS (ÉTS’ Institutional Manufacture Laboratory) which houses 21 machines, including seven NC machining centres. Following proper training, CoRo members are able to use most of these machine-tools independently.
The fourth prototype is a cable-actuated robot, which is driven by
eight motors. This project is currently under development.
Development of simulation software
Professor Bonev is also interested in the design of simulation software for
parallel robots. He has designed a series of Java applets, and will be
designing a software application for the simulation of Delta robots. This
type of work is intended primarily for students registered in the Projet de
fin d’études course, foreign interns, or anyone wishing to work on an
as-needed contract basis. Candidates must be highly skilled in C++ and well
versed in the OpenGL library and the Qt GUI toolkit.
PreXYT, XY-Theta parallel robot
- The first prototype developed at the CoRo
laboratory is an XY-Theta precision positioning table, called PreXYT (for
Precision XY-Theta table). This is a new singularity-free
three-degrees-of-freedom parallel robot with very simple kinematics. The
robot was designed for the precision positioning of silicon wafers, and its
effector can cover a circular zone 170 mm in diameter, with any orientation
between -17° and 17°, and an absolute positioning error under 0.050 mm.
DexTAR, XYZ parallel robot
- The second prototype, called DexTAR (for Dextrous
Twin-Arm Robot), is a rapid pick-and-place XYZ robot, based on a 5-bar
mechanism. Its originality lies in the fact that the robot can reconfigure
itself dynamically to maximize its workspace (by crossing serial
MedRUE, six-degrees-of-freedom parallel robot
- The third prototype is a six-degrees-of-freedom
robot called MedRUE (for Medical Robot for vascular Ultrasound Examination),
which is used to analyze the arteries of the lower limbs. The robot will
perform diagnoses of the stenosis using an ultrasound probe. This project,
which is currently under development, is being carried out in collaboration
with the Hôpital Notre-Dame, a part of the Centre hospitalier de
l’Université de Montréal (CHUM) network.
MicARH, rotary hexapod for micropositioning
- The fifth prototype is a rotary hexapod called
MicARH (for Micropositioning Agile Rotary Hexapod). This project is
currently under development.
- R&D control activities at the CoRo laboratory are led
by Professors Pascal Bigras, Vincent Duchaine and Guy Gauthier, and are
focused on several areas.
One of the projects in this area was carried out at the NSERC’s
Aerospace Manufacturing Technology Centre, and covers the modeling, design
and implementation of control algorithms for industrial robots whose tool is
in contact with the environment. A model that takes into account the robot’s
geometry, the elasticity of its joints as well as its position controller
response has been proposed in order to optimize the design of force and
A medical robotics project is being carried out in collaboration with the
Hôpital Notre-Dame, a part of the Centre hospitalier de l’Université de
Montréal (CHUM) network. Diagnosing arterial diseases often requires precise
three-dimensional images. The echography technique, which is non-invasive
and inexpensive, provides precise cuts of sections of the arteries where the
probe is located. A three-dimensional model can thus be obtained from a set
of ultrasonic scanners, which together allow enough cuts along the artery to
allow a three-dimensional reconstruction. In this project, a secure robotic
controller is currently under development with a view to automating the
capture of 3D ultrasound images of the lower limbs.
Several projects are currently under development, in collaboration with
Hydro-Québec's research institute. These projects are aimed mainly at the
robotic reconstruction of hydro-electric dams, which should bring in
substantial savings, considering that manual reconstruction would require
the draining of the dam in order to ensure workers' safety.
A project for the development of a non-linear ergometer is underway thanks
to a collaboration with Professor Rachid Aissaoui of the LIO and the
Institut de réadaptation de Montréal. This ergometer, which is based on
impedance control applied to direct drive motors combined with instrumented
wheelsets, allows a faithful reproduction of the sensation of a wheelchair
for the user, not only for linear pathways, but also during curvilinear
movements. The control law will soon be extended to allow users to learn to
better propel their chairs in a way that prevents pain in their shoulders.
Control of positioning systems with friction
In this research area, new dynamic friction models are studied with a
view to improving the precision of the control of positioning systems with
friction. The identification of these models, as well as the design of
control laws based on the passivity and the formalism of matrix inequalities
constitute the core of these studies.
Several robust control and identification algorithms have already been
proposed and successfully implemented for various positioning systems, such
as constrained robots and pneumatic actuators.
Iterative learning control (applied to thermoforming process)
This control approach applies to repetitive processes, such as chemical
vapour deposition processes. Because this process is repetitive, the
measures carried out on the preceding batch can be used to correct the next
batch to be produced, and thereby optimize the production quality. This
control is applied on a thermoforming oven in order to allow the automatic
adjustment of the temperature setpoints for heating elements, allowing the
thermoformed plastic sheet surface temperature to match that of a desired
Designing a control algorithm by iterative learning is complicated by the
fact that a thermoforming oven is a non-linear system equipped with many
inputs and outputs. Steps must also be taken to ensure that the convergence
of the temperature setpoints to their ideal values is monotone, and that the
control remains robust even in the presence of variations in the process
parameters and in the environment parameters. A mathematical thermoforming
oven model is used to test these control algorithms.
To try to facilitate the design of a robust design algorithm, Professor
Gauthier combines mixed sensitivity methods (based on H-infinity) and the
Mu-analysis method with the internal control and genetic algorithms. Some
methods, including the Mu-synthesis method, provide robust control
algorithms from iterative learning, but implementing the algorithms will be
a complex endeavour. However, since the controller structure is determined
from the get-go, it is easier to analyze the robustness. The controller can
thus be synthesized using optimization algorithms such as those that are
genetically-based. Professor Gauthier anticipates adapting this design
method to non-iterative robust controls.
Finally, Professor Gauthier has developed a control design approach
involving an internal model and using fuzzy logic. A fuzzy model of the
process can be obtained from the measures carried out on the process, and
the reverse of this fuzzy model can be integrated into the iterative
learning control algorithm.
KUKA robot with force control unit
Echography robot under development
Underwater grinding robot
Mechatronics and haptics
- The CoRo laboratory has expertise in the areas of
mechatronics and haptics. Research on this branch of robotics is carried out
mainly by Professor Vincent Duchaine and his team. This broad category
comprises work in the areas of physical interaction between humans and
robots, the development of sensor technologies and the design of haptic
Physical interaction between humans and robots
Physical interaction between humans and robots is a relatively new area of
robotics, and is aimed at bringing humans and robots to share the synergy of
a common workspace. This evolution would seem to be a natural step towards
more advanced robotics, and lies halfway between today's industrial robots
and the versatile humanoid robots of tomorrow. This possible future
coexistence has the potential of having a significant impact on several
areas associated with everyday life, such as rehabilitation, robot-assisted
devices or assisted surgery. In addition to these three fields of
application, the greatest impact of such an implementation should likely be
in manufacturing. An effective synergy between humans and robots can be
contemplated by marrying the remarkable capacities of humans to reason and
to adapt to unstructured environments with the inexhaustible strength of
Professor Vincent Duchaine is particularly interested in the challenge posed
by fitting these robots with the capacity to intuitively interact with
humans through the creation of the appropriate control algorithms. This
involves work carried out on variable impedance control and on the
development of collision reaction strategies.
Professor Duchaine’s team is also interested in creating new sensor
technologies for various robotics applications. It is working actively to
create low-cost multi-axis load transducers, to design touch sensors, and
develop a touch layer for use as an artificial skin for robots. These
technological developments are attributable to the emergence of new robotics
applications in which robots get to perform more complex tasks and evolve in
less structured environments.
Professor Vincent Duchaine and his team are currently working to create
portable haptic interfaces allowing hand amputees to regain their sense of
touch. Beyond the simplified mechanics which restricts the gripping ability
of current prosthetic devices, the inability of such devices to perceive and
transmit exteroceptive and proprioceptive information makes them that much
more difficult to control. This lack of information has a negative impact on
amputees’ ability to perform certain daily tasks, and requires constant
monitoring of prosthetic devices.
Multi-axis load sensor mounted on Willow Garage PR2
Artificial skin for robot
- The Control and Robotics Laboratory (CoRo) is situated
on the third floor of Pav. A of the ÉTS. The main room, A-3566, is equipped
with 16 workstations. The adjoining room, A-3569, houses a robotic system
and metrology equipment.
The following are the main pieces of equipment available
at the CoRo
IRB 1600 industrial robot, ABB
- The robot’s cell is equipped with a 60,000 rpm spindle (SLF
HF), an electric gripper (Schunk PG 70), an electric actuator (IAI), and a
probe (Renishaw LP2). Four other robots of the same model are used in
Professor Ilian Bonev’s teaching laboratory
Universal gripper, Robotiq
- The Robotiq arm is a smart gripper that can automatically
adapt to the shape of an object. This arm was donated by the manufacturer,
IRB 360 industrial robot (FlexPicker), ABB
- The robot is built into a cell with three conveyors and a
Visualeyez VZ 4000 motion capture unit, PhoeniX
Faro laser tracker ION, Faro Technologies
FaroArm Platinum, Faro Technologies
XL-80 laser interferometer system, Renishaw
QC20-W ballbar system, Renishaw