Legged robot

Walking robots are special robots that can move with the help of " legs ". This is already possible with only one "leg" ( hopping ). In general, however, four-legged, six-legged or two-legged machines also can be used. There are machines that still have more legs, but these can be traced back to the six-legged variant.

• 3.1 Two-legged walking robot static
• 3.2 six-legged walking robot

• 4.1 Passive dynamic runners

History and background information

An early study subject were the various horse gaits. The photographer Eadweard Muybridge took the gallop of a horse on a specially designed recording technique and was able to prove so photographically, that in this gait, the horse at different times with only one foot touches the ground and other times not at all. Although the horse is at any single moment in a non- steady state, it is still stable.

This walking robot can fulfill its task, the sequence of movements and the response to interference must be precisely defined. When wheels are the axial rotations and occasional steering movements, while a machine with " legs " several components matched in space and time coordinates moves.

For machines which have at least six legs ( Sechsfüßer, millipedes, arachnids with eight legs at least ) always be located at least three legs on the ground, so that the machine is stable in every moment.

Even with quadrupeds may be a reasonably stable state can only be achieved if three legs standing on the ground. The example of the animals can be seen, however, that prevent high speed can be achieved.

Walking and running behavior

Static Go

Static walking is when the center of gravity of the robot is located at any point on the feet, so that it can not fall over without the action of an external force.

Dynamic walking and running

Dynamic walking is when the center of gravity of a robot may also be located outside the area of the feet, without the robot falls down. Indeed, one could speak of a "controlled fall ", because the robot would fall during a sudden stop its movement.

From the dynamic running is when the need to maintain the speed of movement will cause temporarily no leg of the robot touches the ground more.

Static walking robot

The classic running robot consists of actuators, sensors and computer control. The "legs" are usually of servo motors to move so that a predetermined movement program is being unwound.

Static two-legged walking robot

The robot ASIMO moves at a maximum speed of 6 km / h, with a size of 1.30 m and a weight of 52 kg, and he needs it very much electrical energy. A special ability of him is that he can climb stairs.

Six-legged walking robot

Six-legged structures are an ideal basis for statically stable walking robots. They are therefore suitable for the movement in rough terrain. There are two different gaits (sequence of leg movements ):

• Tripod gait
• Tetrapod -course

In the tripod gait are at any given time three legs on the ground (Example: Indian stick insect, with 3 stand and 3 vibrating legs).

When Tetrapod transition are always four legs on the ground ( 4 legs, 2 swing legs).

When walking machines with six orthogonal legs is distinguished except by the order of leg movements even after the basic movement of the legs:

• Consequence runners ( follow the leader ) (eg tripod gait, Tetrapod -course )
• Circle runner ( walker circulation )
• Webläufer (weaving walker )

Six-legged creatures occur as a sequence runners. A leg follows (in whatever order ) to the other. Machines can do more. At Circle runner, the three legs of the right-hand side have a common axis of rotation - like the hands on a clock (corresponding to the left legs). The rearmost leg is swung in front of the front leg. But how is now the rearmost leg to get past the other two legs? It just swings through under the belly ( the robot platform).

Also the Webläufer performs a biologically impossible motion. When Webläufer sit all six legs on a common vertical axis at the center of the platform. Each leg can completely walk around the whole body ( a horizontal telescopic movement makes it possible). The legs move from its rearward position to the forward position by being rumgeführt to the other two legs outside.

When walking on uneven ground, it is crucial that the robot within his increment ( potential Aufsetzgebiet of the leg - foothold selection area) finds a safe touchdown without having to stray too far from his main line of approach.

Dynamic Walking Robot

Passive dynamic runners

Walking robot, which can move without power source, based on a fictional 150 years ago a toy. It just had to be initiated and was then able to run down a small slope alone. These rocks the toy from right to left and swings that just lifted leg forward slightly. It swings from left to right and the other leg swings before.

With this construction, the toy can move energy efficient and serve as a starting model for technically more sophisticated walking robot. Tad McGeer had used the 'realized in this toy principle of the pendulum to stabilize the movements in the 80s. No longer a complex and slow control system in an entrained computer should bring the robot to run, but the structure of the musculoskeletal system should stabilize the walking robot without additional actions. If the construction of the simple toy supplemented with a " hip " or " moving feet", then this kind require walking robot only energy during acceleration of the moving masses and not, as in previous walking robots even when braking.