Umashankar Nagarajan

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Unlike statically stable wheeled mobile robots, dynamically stable mobile robots can have higher centers of gravity, smaller bases of support and can be tall and thin resembling the shape of an adult human. This paper concerns the ballbot mobile robot, which balances dynamically on a single spherical wheel. The ballbot is omni-directional and can also(More)
The ballbot is a dynamically stable mobile robot that moves on a single spherical wheel and is capable of omnidirectional movement. The ballbot is an underactuated system with nonholonomic dynamic constraints. The authors propose an offline trajectory planning algorithm that provides a class of parametric trajectories to the unactuated joint in order to(More)
This paper presents a hybrid control strategy for navigation of shape-accelerated underactuated balancing systems with dynamic constraints. It extends the concept of sequential composition to perform discrete state-based switching between asymptotically convergent control policies to produce a globally asymptotically convergent feedback policy. The(More)
The ballbot is a human-sized dynamically stable mobile robot that balances on a single ball. Unlike statically stable mobile robots, the ballbot is tall and narrow with a high center of gravity and a small footprint. Moreover, its dynamic stability enables it to be physically interactive. These characteristics make it better suited to navigate and interact(More)
Developed by Prof. Ralph Hollis in the Microdynamic Systems Laboratory at Carnegie Mellon University, Ballbot is a dynamically stable mobile robot moving on a single spherical wheel providing omni-directional motion. Unlike statically stable mobile robots, dynamically stable mobile robots can be tall and skinny with high center of gravity and small base.(More)
This paper introduces shape-accelerated balancing systems as a special class of underactuated systems wherein their shape configurations can be mapped to the accelerations in the position space. These systems are destabilized by gravitational forces and have non-integrable constraints on their dynamics. Balancing mobile robots, like the ballbot, are(More)
Humanoid robots are expected to share human environments in the future and it is important to ensure safety of their operation. A serious threat to safety is the fall of a humanoid robot, which can seriously damage both the robot and objects in its surrounding. This paper proposes a strategy for planning and control of fall. The controller's objective is to(More)
This paper presents an integrated motion planning and control framework that enables balancing mobile robots to gracefully navigate human environments. A palette of controllers called motion policies is designed such that balancing mobile robots can achieve fast, graceful motions in small, collision-free domains of the position space. The domains determine(More)
The ballbot with arms is an underactuated balancing mobile robot that moves on a single ball. Achieving desired motions in position space is a challenging task for such systems due to their unstable zero dynamics. This paper presents a novel approach that uses the dynamic constraint equations to plan shape trajectories, which when tracked will result in(More)