Design and control of a micro ball-balancing robot (MBBR) with orthogonal midlatitude omniwheel placement

• Published in: 2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) pp. 4098 - 4104
• Main Authors: Yang, Daniel, Sihite, Eric, Friesen, Jeffrey M., Bewley, Thomas
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.09.2015
• Subjects: Force; Friction; Manufacturing; Robots; Sockets; Torque; Vehicle dynamics
• DOI: 10.1109/IROS.2015.7353956

Ball-balancing robots (BBRs) are endowed with rich dynamics. When properly designed and stabilized via feedback to eliminate jitter, and intuitively coordinated with a well-designed smartphone interface, BBRs exhibit a uniquely fluid and organic motion. Unlike mobile inverted pendulums (MIPs, akin to unmanned Segways), BBRs stabilize both fore/aft and left/right motions with feedback, and bank when turning. Previous research on BBRs focused on vehicles from 50cm to 2m in height; the present work is the first to build significantly smaller BBRs, with heights under 25cm. We consider the unique issues arising when miniaturizing a BBR to such a scale, which are characterized by faster time scales and reduced weight (and, thus, reduced normal force and stiction between the omniwheels and the ball). Two key patent-pending aspects of our design are (a) moving the omniwheels to contact the ball down to around 20 to 30 deg N latitude, which increases the normal force between the omniwheels and the ball, and (b) orienting the omniwheels into mutually-orthogonal planes, which improves efficiency. Design iterations were facilitated by rapid prototyping and leveraged low-cost manufacturing principles and inexpensive components. Classical successive loop closure control strategies are implemented, which prove to be remarkably effective when the BBR isn't spinning quickly, and thus the left/right and fore/aft stabilization problems decompose into two decoupled MIP problems.