FlyPod is a compact hybrid robot designed to operate in air and land. It has twelve angular actuators to control the angles of each joint thus being able to perform a walking gait. But how can it maintain stability during flight using the same actuators?
The shape of the quadruped robot is symmetrical and thus the Center Of Gravity (COG) is roughly located in the middle. By assuming that the platform’s mass is equally distributed, the following two hypothetical aerial steering methods can be utilized:
- By actuating the trajectory points of the legs in a common direction, the mass of the linkages could cause the robot’s COG to shift. As shown in the image, a rotational force is generated when one leg is shifted towards the pivot point (middle of the robot) and the opposite leg is extended from the pivot point.
- Another similar control technique is shown in the image bellow. In contrast to the first concept, the four legs are now all spread out. By closing one of the legs, a turning moment is produced from the mass of the opposite extended leg.
For these concepts to generate the necessary moment, a large portion of the robot’s mass is required to be located in the Tibia links. Heavy components such as the robot’s onboard battery can unbalance the system. This problem was resolved by dividing the battery into four identical cells, to obtain a more symmetrical weight distribution. These batteries were placed in the Tibia link of each leg to provide a larger moment and improve the robot’s flight maneuverability.
This innovative COG steering concept reduces additional weight, costs and power consumption related with the flaps or swashplate mechanism, making the hybrid system more efficient. A similar steering technique was also investigated by the US Army in the 1950s when developing the Hiller VZ-1 Pawnee flying platform. This small hovering aircraft was steered using the pilot’s reflexes to manipulate the vehicle’s COG by shifting his body mass.
Stay tuned for FlyPod’s first flight stability test video!