Tech Briefs Magazine - April 2024 - MD-16

into joint torque commands, yielding
much swifter response times to force
changes. This method replaces the
indirect force control often used by
collaborative robots, where force is
converted into joint velocity commands
and subsequently into joint torque or
current commands.
By skipping these intermediate steps,
an adaptive robot can significantly diminish
stiffness in the force direction,
thereby greatly enhancing force control
accuracy. This improvement is pivotal in
fine sanding and polishing tasks, where
maintaining meticulous force control
is imperative for achieving a superior
surface finish.
With direct force control, there is
no need to install additional passive or
active compliance devices between the
robot's flange and the sanders/grinders.
This makes the entire sanding solution
lighter, more reliable, more compact,
and cost-efficient.
The Advantage of
Omnidirectional Compliance
Omnidirectional compliance equips
adaptive robots with the ability to control
forces in all directions within Cartesian
space. This represents an enhancement
over traditional solutions that could only
manage force in axial or radial directions.
Traditional robotic solutions are limited
in this regard due to their reliance
on compliance devices. Their inherent
design limitations confine them to producing
linear or rotational movements
along or around specific axes. Although
this traditional technology can still be
used for basic abrasive tasks, multi-directional
force control is often necessary in
real-world manufacturing.
Omnidirectional compliance is vital
for intricate material abrasion tasks requiring
simultaneous force control in
multiple directions. If we imagine a
robot sanding an object with complex
curves and uneven surfaces, there must
be more than merely axial or radial
force control. Complex shapes require
dexterity in force control across all directions
in three-dimensional Cartesian
space.
Robots equipped with this omnidirectional
compliance can precisely define
force adaptivity in any Tool Center
Point (TCP) frame. This capability allows
Omnidirectional
compliance is also
crucial, especially with equipment like
belt sanders where the robot holds
the workpiece to it. To maintain continuous
contact between the workpiece
and belt sander, the robot must
constantly shift its direction of force
during the abrasive process. To accomplish
this, an external TCP can be set
with respect to the sander, resulting in
consistent compliance direction, even
as the robot's pose changes during
operation.
Omnidirectional compliance is a
powerful tool that broadens the range
of material abrasion tasks that a robot
can undertake. The integration of advanced
force control with omnidirectional
compliance not only enhances
flexibility but also streamlines the
calibration and fine-tuning process,
reducing the time and effort taken
during deployment and finetuning.
Contact Angle and Contour
Following
for dynamic adjustment of the
force exerted, relative to the robot's
end-effector, enhancing versatility in
complex tasks.
Programmable contact angles let operators
define the average force exerted
on a surface directly, an improvement
over conventional methods where the
contact angle affects the force. This has
Vibration reduction is essential for material abrasion tasks. Excess vibrations can damage workpieces and significantly shorten the operational lifespan of mechanical
systems, especially in high-vibration applications like grinding. (Image: Flexiv)
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Motion Design, April 2024

Tech Briefs Magazine - April 2024

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