Tech Briefs Magazine - April 2022 - MD-11

ensure that all the required functionality
is delivered in the smallest package size.
The PCB control board sits at the top
of the pendulum, inside the handlebars,
and carries all the electronic circuitry
required, including a solid-state gyroscope,
microcontroller, DC motor drive,
and power management components.
In the wheeled platform, at the bottom,
there are two axles: A horizontal
axle linking the wheels and a vertical
axle driven by a compact DC motor.
Simple bevel gearing at the intersection
between the axles enables the motor to
drive the wheels in either direction.
For effective control, the system must
maintain orientation within a small
range of angles that are nearly vertical. If
the vehicle tilts by more than 30 degrees
in either direction, stability might be
lost. To maintain balance, the wheels
must be driven continuously with carefully
calculated acceleration and speed.
Magnetic Encoder Solution
After much consideration, the solution
came in the shape of the RM08 rotary
magnetic encoder from RLS. This
noncontact, frictionless rotary magnetic
encoder weighs just 2 g, including cabling,
and features an aluminum sensor
housing measuring 8 mm in diameter
with a thickness of only 3 mm.
The students designed a narrow nylon
collar, to act as a mechanical linkage
between the motor shaft and the magnetic
actuator of the RM08 encoder,
which added less than 0.5 g to the assembly.
The RM08 encoder produces a 12bit
resolution output (4,096 steps per
revolution), is suitable for high-speed
operation up to 30,000 rpm and delivers
an accuracy of ±0.3 º.
By using the RM08 high-speed rotary
magnetic encoder to measure angular
rotation at 12-bit resolution, the students
were able to design a motion control
scheme for a two-wheeled robotic
vehicle capable of self-balancing and
staying upright.
The RM08 encoder is IP68-rated and
designed for integration into a wide
range of high-reliability, high-volume
OEM applications. The rotary magnetic
encoder also addressed the vehicle's demanding
physical design constraints.
Being a compact and lightweight component,
it helped the students overcome
space and load-carrying limitations.
The success of this project has given
the students the confidence to explore
other advanced robotics projects.
This article was contributed by Renishaw
Inc. (West Dundee, IL). For more information,
visit http://info.hotims.com/82320-284.
Scalable Solutions for Precision
Motion Control and Automation.
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to subsystems and turnkey systems, we work with
you to solve your toughest precision motion and
automation challenges.
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The students designed a narrow nylon collar to act
as a mechanical linkage between the motor shaft
and the magnetic actuator. (Photo: Renishaw Inc.)
Motion Design, April 2022
Free Info at http://info.hotims.com/82320-705
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Tech Briefs Magazine - April 2022

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