MIT’s Small Robot Landed Its First Standing Backflip

1. Designing the Quadruped

Researchers in the MIT Department of Mechanical Engineering set out to build a nimble and resilient four-legged robot. The team focused on creating a machine that could handle high-impact maneuvers without sustaining permanent damage. Technical associate Benjamin Katz and undergraduate student Jared Di Carlo undertook the development process. Katz came up with the electric motor design by reconfiguring commercially available parts typically found in small drones and remote-controlled airplanes.

The resulting quadruped was constructed to weigh approximately twenty pounds.

2. Modular Actuators

Each of the robot's twelve joints was powered by an identical modular motor assembly. The compact actuators combined a stator, a rotor lined with magnets, a planetary gearbox, and a position sensor. This configuration allowed the limbs to generate high torque while maintaining low inertia. If a part failed, technicians could swap out the modular unit quickly.

The decentralized design simplified repairs and hardware modifications significantly.

3. Mobility Testing

Before attempting complex acrobatics, the team evaluated the quadruped across various uneven indoor and outdoor surfaces. The springy robot demonstrated the ability to trot over rough terrain at speeds surpassing normal human walking paces. When kicked or knocked to the ground, the machine used rapid arm swings to right itself. Its high-force impact tolerance allowed it to execute aggressive movements without breaking gearboxes.

The platform exhibited stability and agility during preliminary locomotion trials.

4. Programming the Flip

Inspired by a class taught by Professor Russ Tedrake, the developers explored whether the robot could perform a backflip. They wrote a comprehensive nonlinear offline trajectory optimization program that incorporated the machine's physical dynamics. The algorithm calculated the exact torques required for every individual motor throughout the entire aerial rotation. The objective was to start upright and land cleanly after a complete 360-degree revolution.

The trajectory calculations were compiled and loaded into the robot control system.

5. The Demonstration

The research team placed the mini cheetah on a flat floor inside the laboratory for its first live test. Operators initiated the pre-programmed sequence while recording the event with multiple cameras. The quadruped compressed its legs, launched upward into the air, and rotated backward precisely as calculated. It completed the full rotation and landed firmly on its feet without tipping over.

The successful maneuver marked the first time a four-legged robot performed a backflip.

6. Analyzing Results

The engineering team reviewed sensor data and high-speed footage to analyze the mechanics of the completed flip. The actuators absorbed the landing impact successfully without any mechanical failures occurring during the descent. Researchers noted that the high force rate capability of the motors made the dynamic maneuver possible. No structural damage was recorded on the chassis or the limbs.

The initial test confirmed the accuracy of the trajectory optimization software.

7. Expanding the Fleet

Following the successful demonstration, the MIT group began constructing additional units of the quadrupedal robot. The researchers aimed to manufacture a set of ten identical machines to distribute to other academic laboratories. By sharing the hardware, the team hoped to accelerate research into dynamic robotic locomotion. Presentations were scheduled for the upcoming International Conference on Robotics and Automation.

Assembly work continued in the laboratory to meet the production goals.

8. Project Conclusion

MIT’s 2019 report described the mini cheetah completing its programmed standing backflip on the first attempt. Katz and Di Carlo had worked on the maneuver within a team developing the machine’s hardware and controls. The report also described plans to build additional units and test other movements. Those proposed experiments were future work, separate from the backflip that had already been demonstrated.

The recorded backflip succeeded; the later plans remained plans.

Sources

• MIT News: The mini cheetah does a backflip