Setting a goal
Since I’ve decided to build a robot, let’s think about what this little guy exists for.
The original goal was a robot with high mobility that jumps regardless of terrain, like that stuntman. But what’s the point of bouncing around everywhere — it just drains the battery. So I decided to give this not-yet-born child a purpose while keeping its mobility intact.
A medical-supply delivery robot for rough terrain
I designed it to carry a load of up to about 10 kg, then secured enough mobility for it to bound around a wooded hillside — giving it meaning as a robot that saves lives.
1. Crossing rough terrain
With only one leg, I think the ground condition won’t matter much unless the soil is boggy. To turn environments piled with fallen leaves or covered in nothing but rock into a reliable foothold, the robot’s foot should be like the tip of a trekking pole: a protruding spike, with a guard a few centimeters behind it, creating a setup that digs into the ground for grip while the guard lets it push off the ground stably.
2. When force doesn’t solve it, apply more force!
I gave some thought to building the leg that does the jumping.
The requirements for the leg are:
- When the trigger fires, a large load must be applied instantaneously
- Fast discharge (it must spring up quickly)
- Fast recharge (it must return to the ready state quickly)
- It must be able to absorb impact
So I considered three approaches in total:
- Spring
- Air
- Explosion
The spring approach, as everyone knows, compresses a spring and then releases a latch to launch. It’s the simplest, but without a high-output motor, the larger the load it must hold (the stiffer the spring), the harder fast recharging becomes. And unless you use a wire — that is, if you go with something like a screw drive — fast discharge is hard too.
Air is disappointing in efficiency per unit weight. You have to keep recharging the tank pressure, pneumatic cylinders are heavy and expensive, and cheap ones respond poorly; air tanks are also very heavy and carry an explosion risk if damaged.
If there’s an explosion risk anyway, why not just jump by causing an explosion! Hahahahaha Responsiveness? GOOD! Force? NICE! Efficiency per weight and sustained operation? The best! But running that experiment inside a high school is tough;; And safely containing an explosion requires reliable cylinder technology, and I don’t own a CNC! Buy me one and I’ll give it a shot!
Conclusion: I went with a spring, recharged by a motor at the same moment it lands!!