Test & measurement
Magnetic encoders support the stabilisation control of a self-balancing two-wheeled robotic vehicle
balancing act
In the design of a self-balancing two-wheeled robotic vehicle, accurate high- speed measurement of angular rotation is a key requirement. Furthermore, the minimisation of component weight and size is an equally vital consideration. Engineering students at Tokyo Denki University found the answer in the RM08 rotary magnetic encoder, from Renishaw's associate company, RLS.
Seiichi Hirota and Shinkichi Ogimoto. Their founding principle was to promote engineering education as a basis for national economic development. Working in the University's Robotics and
D
Mechatronics Department, Jun Ishikawa is a pioneering researcher in several technological fields including robot control system development. He challenged his engineering students to create a two-wheeled, self- balancing robotic vehicle. For this project, his students chose the RM08 rotary magnetic position feedback encoder from RLS, a Renishaw associate company.
BackgRoUnD Ishikawa challenged his university students to solve a classic control theory problem - the inverted pendulum. The basis for the well-known Segway personal transporter, the inverted pendulum has its centre of mass located above the pivot point. Unlike a suspended pendulum, which will naturally
return to a stable equilibrium position after being displaced, the inverted pendulum is inherently unstable. Imagine holding a pool cue or a broom handle upright on the palm of your hand - it would tend to fall over without continuous adjustments to the position of your hand. A shorter inverted pendulum accelerates away from
the vertical position faster than a longer one, requiring more frequent position adjustments and presenting a more challenging control problem - balancing a pen on your hand is trickier than balancing a pool cue. One solution to the problem, as implemented by
Segway, is to mount the pivot point on a wheeled platform. This type of vehicle takes inertial inputs from an IMU (inertial measurement unit) which comprises two sensors: an accelerometer and a gyroscope.
30 September 2021 Instrumentation Monthly
edicated to the teaching of science and technology, Tokyo Denki University was established in 1907 by two young engineers,
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