ABB_Giving robots a brake
Giving robots a brake
At ABB, automation safety does not take a backseat to performance. The
company's introduction of Active Safety based on advanced software is a
case in point. By being able to predict what lies around the corner,
even heavy robots ca
n make split-second adjustments that ensure the
safest, most efficient production possible.

Brake too hard or too
soft, Thomas goes on, and youre off the track. Youd know what
youre doing when racing side by side with an opponent whos doing
200km/h. says Thomas Gunnarsson, Product Manager at ABB Robotics."
ABS on ABB robots
Thomas Gunnarsson, Product Manager at ABB Robotics, knows what kind of
damage big machines with heavy payloads can do. Hes currently working
closely with clients in the automotive industry. The job involves press
automation of the various parts that make up a carbody, as well as the
numerous processes behind the assembly. The main processes are spot
welding and material handling including a heavy involvement of
powerful robots.
Safety first
ABB decided to equip its robots with an Active Brake System, which lies
at the heart of the companys safety and perform-ance philosophy. As
Thomas points out: Even though youve hit the emergency stop, a big,
powerful robot will still brake along its programmed path. Which is
vital since most tools and fixtures in this indus-try are very
expensive and, on occasion, even unique.
For ABB customers, the downtime involved in the event of a damaging collision doesnt even bear contemplating.
Braking at the raceway
Heres where Thomas, who has a passion for American muscle cars,
compares ABB robots to drag racing. The racing car has to take off
immediately when the light turns green, but equally important is to
handle the braking energy required to halt it at the end of the drag
strip.
Brake too hard or too soft, Thomas goes on, and youre off the
track. Youd better know what youre doing when racing side by side
with an opponent whos doing over 200km/h. Naturally, the same applies
to a robot, which operates in an environment where everything around it
is costly and cant
afford to be damaged.
The knowledge
According to Thomas Gunnarsson, the key to ABS is knowledge. Knowledge
of the load parameters of the part and gripper being handled which
the IRC5 controller receives via Load Identifi-cation. Knowledge of the
load data for the manipulator arm, which for the controller system
becomes dynamic and varies depending on the position in the working
envelope. This input is received via ABBs Mechanical Supervision
feature. Knowledge of the friction in bearings, gearboxes and motors,
and the fact that gravity some-times assists the braking procedure
and sometimes doesnt.
Knowledge of the centrifugal forces, along with complete data about the
manipulator with its payload, while also factoring in the specific
programmed path. In short, by keeping an eye on the horizon the
route where the robot is headed the very best path following is
ensured.
Insurance all the way
A closer look at the technology reveals that the ABS is active during
all stop modes, braking the robot to a stop with the power of the servo
drive system along the programmed path. After a given time, the
mechanical brakes are activated, thereby ensuring a safe static holding
brake.
The stopping process is in accordance with a so-called class 1 stop,
which means maximum torque on the axis with the heaviest load
determining stopping distance. While operating in teach mode, however,
only the mechanical brakes are applied. In this case, the robot would
need to be jogged manually back onto the path. This is time-consuming
and requires trained personnel on site. Since the servo drive and
motors are active during the complete braking sequence, the motors can
either push or pull to ensure that braking time is optimised while also
maintaining the programmed path at all times. Another obvious benefit
of ABS is that, following a brake operation, the Power Robots always
remain on the programmed path. This enhances re-starting speed.
Clients who are better safe than sorry
Thomas reveals that ABB has demonstrated the new solution to a number
of European, Asian and American automotive manufacturers. To all of
them, ABBs Active Brake System is an indispensable feature when it
comes to keeping production on track.
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