  This paper introduces HOPPY, an open-source, low-cost, robust, and modular
kit for robotics education. The robot dynamically hops around a rotating gantry
with a fixed base. The kit is intended to lower the entry barrier for studying
dynamic robots and legged locomotion with real systems. It bridges the
theoretical content of fundamental robotic courses with real dynamic robots by
facilitating and guiding the software and hardware integration. This paper
describes the topics which can be studied using the kit, lists its components,
discusses preferred practices for implementation, presents results from
experiments with the simulator and the real system, and suggests further
improvements. A simple heuristic-based controller is described to achieve
velocities up to 1.7m/s, navigate small objects, and mitigate external
disturbances when the robot is aided by a counterweight. HOPPY was utilized as
the subject of a semester-long project for the Robot Dynamics and Control
course at the University of Illinois at Urbana-Champaign. The positive feedback
from the students and instructors about the hands-on activities during the
course motivates us to share this kit and continue improving in the future.
