Omnidirectional tripedal robots navigate effortlessly by scooting, shuffling, and climbing.

Researchers at the University of Michigan have designed a novel, three-legged robotic system called SKOOTR that combines walking and rolling motions to enable agile movement and obstacle navigation.

The concept behind the SKOOTR – a Skating, Omni-Oriented, Tripedal Robotic venture – originated with Assistant Professor Talia Y. What’s driving innovation at the University of Michigan’s EMBiR Lab? Dr. Moore shares insights into the lab’s research evolution and movement in biology and robotics.

When developing the idea for his innovative product, Moore revealed that he drew inspiration from a serendipitous moment in his own life: “I was once casually rolling around my office chair between groups of students,” he shared with us. As I sit comfortably in the effortlessly revolving office chair, I can effortlessly pivot in any direction, leveraging my legs to perform a wide range of movements while maintaining remarkable stability. I noticed that this exceptional agility in omnidirectional movement bears a striking resemblance to the remarkable adaptability displayed by brittle stars as they dynamically adjust their trajectory while propelling themselves through the water.

Adam Hung, a motivated college student, collaborated with Challen Enninful Adu and Moore to develop a cutting-edge robot, inspired by its potential applications. Researchers have developed three-legged robots that can successfully activate dimes, but they face a significant limitation when it comes to navigating their environment – “inefficient and dynamically unstable locomotion” can result from elevating these limbs. To overcome this drawback, Hung introduced a freely rotating sphere to the design.

University of Michigan, Hung, Adu, and Moore.

Skooter features a central control module, which operates as the command centre, comprising an Arduino Uno microcontroller, an inertial measurement unit (IMU), and a rechargeable lithium-ion polymer (Li-Po) battery. The robot also features a subframe-mounted bearing system, comprising four spherical bearings that make direct contact with the ball at precise points.

Each leg attached to this hub is equipped with two parallel rotary joints, powered by standard servo motors. At each leg’s terminal, a hybrid finish effector is situated, comprising a small servo that deploys a spherical bearing for rolling interaction, or retracts it to enable a rubber cap to make contact with the ground and propel or retrieve the robot laterally.

The large central sphere provides the robot with another point of contact, enhancing its stability during transfers. Despite its ability to grasp the ball, lift it above the ground, and enable the legs to navigate hurdles akin to stairs or rough terrain before releasing it again and propelling forward.

According to Moore, the unique combination of the central sphere and multiple legs makes SKOOTR exceptionally stable. We’ve conducted numerous tests with Skooter and surprisingly found that it’s virtually impossible to tip it over while in operation. While initially seeming to excel solely at the distinctive ‘skooting’ gait, this ability belies a capacity for even greater feats. With the ability to lift its spherical body using its leg-like appendages, SKOOTR effectively navigates hurdles that would pose significant challenges for traditional rolling robots. SKOOTR may even climb stairs.”

The University of Michigan, Hung, Adu, and Moore?

The open-source nature of the design files, including CAD information and code, facilitates collaboration and modification. The majority of the robotic components can be produced using 3D printing with PLA filament or sourced from online retailers for readily available parts. The estimated venture price is approximately $500.

The EMBiR team identifies opportunities for mapping and exploring challenging indoor spaces, complemented by payload delivery capabilities and serving as an affordable research tool. Subsequent steps involve incorporating sensors to enable autonomous self-localization, develop movement plans, and create detailed maps of the environment.

Details about the venture can be found at and the accompanying video provides further information.

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