First of all, I think walking robots are great! And since I made quite a few driving robots and only one (6 legged) walking robot, it’s time do dedicate a project on a more advanced walking robot.
The next step is to decide on the type of walking robot. The most obvious way is a servo-based humanoid robot like RoboNova. This does however require a large initial investment (in servo’s) and – from my experience with my previous walker – I expect the major effort will be the definition of the movement patterns and corresponding servo signals. Or – to put it in other words – little chalange, mainly just work.
So I decide to take the alternative route and try to build a 2d (passive) dynamic walker.
Mechanics
The robot is a 2x2 legged robot. The legs consist of 15-mm aluminum with MDF feet. The legs are interconnected with a 5-mm axis. The robot walks on a floor with a 3-degree slope. Stepping stones are used to create the necessary free space of the feet on the swing leg.
Electronics
None, this robot is fully passive.
Results
At first, the robot consisted of two U-frames, connected by an axis. It
turned out this version of the robot did not walk properly.
Martijn Wisse of the Delft Biorobotics Laboratory of the Delft University of Technology advised the following improvements:
· Increase the weight on the hip and shift this weight slightly to the back.
· Reduce friction on the hip axis.
· Add feet with a radius of 1/3 of the leg length and keep those feet light.
· Add a provision to limit the step size.
And
· Make the robot frame more rigid.
· Add a motor to speed up the forward swing of the leg.
Take a look at the result, with the first four improvements implemented:
Future work
Although the robot walks, the repeatability of the runs is low. An
important cause is the frame of the outer legs, which is not rigid
enough. This makes it virtually impossible to put the stepping stones at the right
location. And this is required since the robot can’t lift its feet...
So first priority is to build a more rigid robot that is able to lift
it’s feet. A next step is to add a motor to speed up the
forward swing, which should make the gait more stable and adds energy required by the robot to walk on a
flat floor.
Links:
My Robots