Japanese engineers have created a biped robot with a quadrocopter fixed to it. The drone in this system sets the motion, and the legs themselves adjust the gait to the speed of the drone, the developers told the publication IEEE Spectrum. The authors presented a report at the SIGGRAPH 2018 conference.
Because of their design, two-legged robots are unstable and engineers have to find a variety of ways to maintain balance. At the same time, even advanced robots that participate in the DARPA Robotics Challenge often fail to maintain balance in fairly simple situations. Some engineers simplify the task by adding a two-legged robot supporting structure that does not let it fall. For example, in the robot BALLU such a design is a balloon, and the bipedal robot ATRIAS is fixed on a rigid swivel beam. Although such designs do simplify the maintenance of balance, they also limit the movements of the robot.
Shunji Yamanaka and his colleagues from the University of Tokyo used a quadrocopter fixed to the body of a biped robot to maintain balance. They chose this scheme, because the drone allows not only to support the robot in an upright position, but also to direct it with the greatest precision to the right side.
Each robot leg consists of two segments, and a servomotor is installed in each of the two connections. The algorithm that controls the legs receives the velocity of the quadrocopter as the initial data, and plans the movements of the legs in such a way that, in contact with the ground, the speed of the foot is zero. Engineers used the machine learning algorithm, which receives a reward according to how much the speed of the foot is close to zero at the time of contact.
It is worth noting that for measurement of speed engineers use an external stationary tracking system, so while the robot can not be used outside of a specially equipped room. The authors told that they view the robot as a research project, which can be used in practice only for entertainment, for example, to create a realistic walking cartoon character.
Interestingly, in the field of biped robots, there is another direction – some engineers are developing systems that allow already falling robots to minimize the consequences of the fall. Recently, American engineers taught abiped robot to fall with their hands for nearby objects and, if possible, even return to their original position, and in 2016 another research team created analgorithm that allows the robot to mitigate the impact when falling to the floor.