Rowdy Runner II: An Independently Actuated Rimless Wheel Robot

Wheeled robots are energy efficient but cannot travel across uneven terrain. Legged robots, however, can traverse rough terrain, but are much more energy expensive. Rimless wheels are a wheel-leg hybrid that blends the benefits of both together. This thesis presents the design and control of a rimless wheel robot that achieves straight line walking and turning. The robot consists of a center body and two rimless wheels, each with 10 dampened spokes. Each wheel is axially connected to the body through a shaft. Each motor is connected to a shaft through two pulleys and a belt, resulting in a reduction of 5.4:1 from the motor to the wheel. The body houses the sensor, computer, microcontroller, motors and encoders, motor controller, and batteries. An inertial mea- surement unit is used to measure the angle of the body with respect to the vertical axis. The robot is controlled hierarchically; on the top is the Raspberry Pi, which reads sensor data, communicates with the microcontroller, and collects data. In the middle is the Teensy microcontroller, which collects the sensor data and calculates an output using a proportional-integral-derivative controller. On the bottom is the motor controller, which receives the output from the Teensy and moves the motors accordingly. The controller on microprocessor ensures the body maintains a steady pitch. The steady pitch angle propels the robot forward. To achieve turning, a differential current was applied, either added or subtracted, to each motor. The robot is able to achieve a steady state speed of 1 m/s with an energy usage (power per unit weight per unit velocity) of 0.13, about half the energy consumption of a human walking. The robot is also capable of sharp turns with a radius of approximately 0.5 meters.