Search and rescue missions, along with other scenarios in which obstacles or high walls would pose problems for humans and robots, could greatly benefit from throwable robots. Unfortunately, they often don’t land like they are supposed to. A research team at West Point’s Robotics Research Center is eliminating that challenge with its Agile Ground RObot (AGRO), which always lands on its four wheels.
The West Point team’s goal was to develop a robot that could achieve zero pitch or roll before ground impact. Their work led to the creation of AGRO, a four-wheeled independent drive and steering robot. Since the robot is designed with independent wheels and steering, it has the capability for omnidirectional maneuvering on the ground. Each wheel has its own electric hub motor that controls the yaw, pitch and roll of the wheel, enabling the robot to self-stabilize and reorient itself in the air for a perfect landing.
Once AGRO is dropped or tossed, an onboard inertial measurement unit instantly detects that a freefall is happening. An integrated proportional-derivative (PD) controller is then activated, which sets each wheel in motion. The angle and speed at which the wheels spin provide the torque needed to control the robot’s landing, as well as evenly distribute the force of impact. For example, if a pair of wheels spin together, the robot’s body counteracts that by twisting in an opposite direction to control the pitch and roll.
As part of its research, the team compared a controlled and noncontrolled freefall. With the controller enabled, AGRO was dropped from 0.85 m with a roll angle of 16 degrees and pitch of ˗23 degrees. The robot was able to self-stabilize in 402 milliseconds. The researchers believe it has the capability to achieve stabilization in 250 milliseconds with 22.5 degrees pitch and roll. The robot doesn’t have a suspension system, so testing was conducted on a foam pad. Even so, the research indicated that the impact force was reduced by 20 percent, and there was a 100 percent reduction in improper positioning, such as upside down.
Although the team presented its research at the online 2020 IEEE/RSJ International Conference on Intelligent Robots and System Engineers, it continues to forge ahead with AGRO 2. A hybrid wheel-leg and a non-pneumatic tire are being incorporated into the robot’s design in the hopes of allowing it to maneuver up and down stairs and curbs. This research has the potential to bring about capabilities for full-sized vehicles to be airdropped or driven off ramps without mishaps or entanglement in parachute lines.
Interested in more robotic innovations? Check out Researchers Take Inspiration from Origami to Build Flexible Microbots and See Spot Scan. Dog-like Robot with a Scanner for a Head.