AGRO robot always lands on its four wheels when thrown

Throwable Robots seem like a great idea for a bunch of applications, including exploration and search and rescue. But often, the robot does not land the way you want it to land.

To solve this problem, engineers have developed a robot known as AGRO (Agile Ground RObot) that can be thrown into an environment and always lands on all four wheels. Developed at the U.S. Military Academy at West Point, the prototype robot can control the tilt angle in flight to land in the correct position.

The AGRO robot has a Four-Wheel Independent Drive and Steering (4WIDS) architecture that enables it to maneuver omnidirectionally on the ground. This wheel architecture also allows AGRO the novel capability of controlling its orientation in the air and landing on its “feet” like a cat. Each wheel is independently driven and steerable and has its own electric hub motor.

The robot has independently driven and steerable wheels.
The robot has independently driven and steerable wheels.

When the robot is thrown, its onboard inertial measurement unit can detect the freefall in an instant. It then triggers an integrated proportional-derivative (PD) controller that sets each of the wheels spinning at different angles and speeds. The result of the wheels spinning at different angles and speeds delivers torque to control the pitch, roll, and yaw angles of the robot, allowing it to land squarely on all four wheels. This ensures that the robot lands upright on its wheels and helps distribute impact forces evenly, so the chances of damage are minimized.

An experiment comparing a controlled and noncontrolled fall was conducted in which AGRO was dropped from a height of 0.85 m with an initial roll and pitch angle of 16 degrees and -23 degrees, respectively. With the controller enabled, AGRO can use the reaction torque from its wheels to stabilize its orientation within 402 milliseconds.

This capability was developed to allow emergency response personnel to rapidly deploy AGRO by throwing it over walls and fences or through windows without the risk of it landing upside down. The team is planning to build a future version with bending legs with wheels on the ends. This would help absorb landing impact and allow it to step over obstacles.

The development will be presented later this month via the online 2020 IEEE/RSJ International Conference on Intelligent Robots and System Engineers developed AGRO (Agile Ground RObot) that features four steerable wheels with in-hub motors and always lands on its four wheels when throw Engineers developed AGRO (Agile Ground RObot) that features four steerable wheels with in-hub motors and always lands on its four wheels when thrown.

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