Tech Briefs Magazine - June 2023 - MD-15

in offering their advice. In the beginning,
we were not even sure what requirements
we actually had of the sensors.
We worked all this out and defined
it together. "
First, potential sensors must be extremely
robust and resilient in the face
of tough outdoor conditions (mud,
dust, rain, strong sunshine, unevenness
in the ground). Components in the
PURE.MOBILE range of sensor modules
from SIKO are particularly suitable
for use in mobile machines under
harsh
environmental
conditions. A
double wheel is fitted to the back of the
vehicle, which can rotate and thus control
the steering. The steering angle is
recorded, processed, and sent to the
controller by the WV5800M magnetic
rotary encoder.
This is a multiturn rotary encoder by
means of which even multiple rotations
can be detected absolutely. If the power
supply is interrupted, because the batteries
are flat for example, the steering
angle previously set
is
still present.
Without an absolute encoder, this
would incorrectly be set as the zero degrees
angle when the vehicle is started
up again.
The magnetic measurement principle
meets the requirements of robustness
and resilience. The high precision and
reliability of the rotary encoder also impressed
the team, meaning that the vehicle
always adjusts its steering angle so
that it keeps to its defined path - without
failures or unacceptable deviation
from tolerances. In order to increase
safety in interaction with the people
working in the orchard still further, the
WV58MR safety variant of the rotary encoder
with redundant position detection
will be used for future vehicles to reliably
prevent failures.
In the development phase, the focus
was initially on technical feasibility, so
that the rotary encoder without the
safety standard was adequate. The plus
point of the SIKO models: the two rotary
encoders are identical in design, so
that no mechanical adjustments need
to be made to the application when
swapping them.
The second SIKO rotary encoder, the
AH25S, is even smaller and more compact,
but no less robust. It is a single turn
rotary encoder which monitors the position
of the box holders, the so-called
flippers. The filled fruit box is picked up
Motion Design, June 2023
The position of the box holders, the so-called flippers, is detected by the robust AH25S miniature rotary encoder
(the rotary encoder is located at the top of the structure). (Image: hochschule 21)
at four points by one flipper for each.
When the robot moves over the box and
the spring-loaded holders touch it, the
flippers swivel to the side, then open automatically
and are then located under
the four corners of the box for pick-up.
In order to be able to transport the
box safely, the position of each flipper
must be known: Has it really swiveled
back or has it jammed? Are all four flippers
under the box to ensure that it is
picked up correctly? The space is very
restricted, so a miniature rotary encoder
was required which could be used directly
without a special holder. An analog
encoder is adequate here, as the data
is less critical than that provided by the
steering angle sensor.
Many little cogs must interlock in a
development project of this sort to
turn a vague idea into a technically
perfect product, which in future can
be used with a balanced cost-benefit
ratio in numerous orchards. To offer
farms genuine added value, the intention
is to use " AurOrA " for other
maintenance work, too, such as mulching
and mowing or as support for
planting new trees. Effective use virtually
throughout the year, is therefore,
possible and is not just restricted to
harvest time.
This article was contributed by SIKO
GmbH. For more information, visit
www.siko-global.com.
15

http://www.siko-global.com

Tech Briefs Magazine - June 2023

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