2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Swiss engineers have developed an algorithm to control four-legged robots with wheels at the ends of their legs. Using it on a new modification of the ANYmal robot, they showed that a robot controlled by such an algorithm moves across terrain with different terrain better than similar developments. The article will be presented at the ICRA 2019 conference.
Engineers use a variety of propelling mechanisms in their robots, such as wheels, crawler drives, and legs. They differ not only in design, but also in driving characteristics that make them optimal for certain tasks. For example, wheels allow you to move quickly and simplify control algorithms, and legs allow you to overcome obstacles and move on difficult terrain. There are even robots that use both of these mechanisms, but almost all of them actively use only one of the mechanisms or use slow static movements.
Marco Hutter and his colleagues from the Swiss Higher Technical School of Zurich have created a new modification of the ANYmal four-legged robot, equipped with four legs with wheels at the ends, capable of actively using two types of movements. The ANYmal robot was previously developed by the same organization and used by this and other research groups to experiment with different control algorithms. For example, he was recently taught to dance rhythmically to music. The robot is driven by 12 electric motors, thanks to which it can move each leg in almost any direction.
For their new work, engineers modified ANYmal by attaching a wheel with an electric motor to the end of each leg. But the main achievement of the work lies in the algorithm that allows the robot to actively use its legs and wheels. The algorithm is based on the method of searching for points of zero moment, widespread in the field of walking robots, in which the robot calculates its movements in such a way that the sum of all external forces is directed towards the surface. In this case, the algorithm constantly calculates a triangle, bounded by three points of contact of the legs with the surface, inside which a point of zero moment can be located.
The robot can move forward on wheels, turn with steps, and also step forward if there is an obstacle in front of it that needs to be climbed. During movement, the robot constantly adjusts the position of each leg in such a way as to minimize the displacement of the center of mass in height.
Trajectory of the center of mass (red line) when driving on an uneven surface
In the future, engineers plan to continue improving the algorithm. In particular, they intend to teach him to use both walking and moving on wheels.
Recently, another group of European engineers unveiled the Centauro robot, which also has four legs with wheels at the ends, but also has two arms and can turn wheels. In early September, engineers demonstrated an unusual control system for this robot, which allows it to copy human movements based on images from the camera.