Tech Briefs Magazine - June 2022 - MD-12

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EXPERT Insight
Optimizing Robot Design with Dual Encoders
The cost of producing a robot is strongly influenced by its design. One essential design component is the rotary encoder, which measures the
speed and position of each axis. An encoder's accuracy thus determines the final accuracy and repeatability at the tool center point. As a result,
special attention must be given to proper encoder mounting during production. In this interview Jonathan Dougherty, Business Development
Manager, Automation, at Heidenhain Corporation, discusses best practices to optimize robot design with encoders.
Motion Design: Encoders are needed to
achieve high-precision motion control. What
are some of the factors robot designers
must consider when selecting an encoder?
Jonathan Dougherty: There are three main
things that robot manufacturers consider
when selecting an encoder. The first is accuracy:
What are you trying to do, and how
accurately do you want to do it? If you are going for a dynamic
and precise application, you want to have a higher tool point accuracy.
If you are looking for more speed control, you can go with
lower accuracy. The second thing would be the interface option,
which is somewhat dependent on what the existing electronics
manufacturer might have, and what they can communicate with.
But if you are starting from scratch, you look at all the different
varying options that are out on the market. And especially currently,
where we have more and more data being provided, getting
into the IoT and Cloud, you want to make sure that you have the
correct interface for your sensor inputs to allow for fast communication.
Finally, it's cost and with encoder cost, the not only is the
purchase price of the encoder important, but also the total cost of
ownership. So, it's important to look at things like the maintenance
that needs to be done for the encoder, the type of technology that
supports longer lifetimes, as well as things like the mounting procedures
and ease of use.
Motion Design: Today, robotics has progressed from handling
heavy loads while substituting repetitive motion with more accurate
motion. How does a dual encoder robot design enhance
robot joint accuracy?
Dougherty: It's becoming common practice now to add secondary
encoders to specific robot joints to increase the tool point accuracy.
Whenever you have a robot joint, you'll have a servo motor driving
the actuation, and then typically you will have some sort of gearing.
You want to have the best positioning you can after that gearing, so
robot manufacturers are either adding a secondary encoder around
the joints or integrating it within itself. But having a dual encoder
allows you to basically have both of those feedback communications
- the motor speed and the positioning after the gearing
- consolidated into one and have that single encoder provide you
with that information, so that you can easily interpret and use it to
increase your two-point accuracy for the robot.
Motion Design: Can you provide a real-life example of an application
where the technology was used?
Dougherty: The dual encoder has been implemented into some
popular collaborative robot designs. Collaborative robots, or cobots,
are robots working in collaboration with human operators. Our dual
encoder is perfectly designed for integration into the joints
of these cobots, and allow for functionality with enough
accuracy and safety involved, so that you can have
the robot work in conjunction with the human next
to it, and know that the positioning of that robot is
exactly where it should be, and the level of safety
is where it should be to make sure that that human
operator is fine as well working with the robot.
Motion Design: The demand for industrial robots
due to factory automation and for labor-saving
is drastically increasing worldwide. Safety is
of utmost important for robots and humans to
work together. How can dual encoders help in
enhancing safety in collaborative robots?
Dougherty: Our dual encoder is integrated with a pre-certified
functional safety network. We have actually certified this encoder
up to SIL2/PLd certification. So, when manufacturers use this product,
they already have a pre-certified block, which helps to ease
their overall system certification process.
Watch the full interview with Jonathan Dougherty at https://
www.techbriefs.com/ei2206/video/heidenhain.
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Motion Design, June 2022
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Tech Briefs Magazine - June 2022

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