GEERHEAD
Cleaning Algorithm
Based on readouts from rotary encoders, the robot’s
trolleys move sideways the width of the cleaning head, so
that no area of the panels is missed. Once the head has
cleaned the entire area it covers vertically, the trolleys
move again.
Inductive proximity sensors detect when the robot is
moving between panels or when it has reached the end
of a row, according to Dr. Constantinos Mavroidis, director
of the Biomedical Mechatronics Lab at Northeastern
University.
The cleaning motion of the head (with brushes and
sprayers) applies just the right pressure to insure a clean
surface without scratching the panels.
A rotary encoder on the pulley that drives the lift
belt records the distance the cleaning head has traveled.
“By setting the top and bottom limits during installation,
the robot knows where the cleaning head is in its Y axis
direction at all times. The X axis direction is read by
encoders on the trolley’s lateral drive motors,” says
Dr. Mavroidis.
The robot has enough sensor input to keep from
driving itself right off the solar panels. The rotary encoders
exist on all the drive motors, tracking the X and Y distances
that the cleaning head has moved across the plane. “Each
time the cleaning head moves sideways, it detects the edge
of the solar panel and resets the distance counter to
minimize errors that build up due to slippage of the
cleaning head,” explains Dr. Mavroidis. This makes the
robot’s calculations about where it is in the plane across
the solar panels very accurate.
The researchers plan to increase the robot’s intelligence
by introducing more sensors and combining them with
algorithms for checking panel functionality. By monitoring
the status of each panel surface before and after cleaning
it, the robot could vary the pressure applied to the panels,
vary the cleaning rate, adjust the water pressure, or clean
the panels that are really dirty, twice.
Design Challenges
As with most successful robotics designs, the solar
panel cleaner PV Cleaner Robot v1.0 began with a
problem that demanded a solution. Once several ideas for
approaching a solution were recorded, the team put them
into a decision matrix that required each idea to score
high based on how well the concept improved on existing
cleaning methods given a set of improvement priorities.
Remaining challenges include improved cleaning
efficiencies, decreased size for the apparatus, improving
sensors, and adding various kinds of inspection
equipment. Researchers will eventually replace the current
hardware with lighter materials to reduce the weight of
the device.
Considerations
Permanent installations of cleaning robots could
eliminate assembly time and associated risks and allow for
more automated cleaning schedules. “However, this device
was originally designed so that with only a handful of
Different views of the robotic cleaning system on solar panels, including trolleys at top and bottom.
SERVO 06.2009
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