Sylvie 2021 - Complete Bipedal Robot Lower Body

thingiverse

**Current status: Ready to balance on one foot with ease, boasting impressive bending and stretching torque. Accelerometers are next in line to unlock walking capabilities!** Parts for Sylvie 2021 Bipedal Robot Lower Body are now available. Most parts need to be printed flat/horizontally before being glued together for maximum strength. The only exceptions are the Tops and Bottoms of major Leg and Thigh pieces where stepper motors should slide in. Gluing these together will prevent proper installation, so use clips provided and a cover to secure them. Check out other gearboxes available for purchase. Update: A crucial piece that connects Gearbox B to Gearbox A (leg to foot) has been added. Demo: https://www.youtube.com/watch?v=uaK3g2s6rHQ https://www.youtube.com/watch?v=i33-BABMq98 **To-do-list:** - Experiment with placing gyroscopes/accelerometers in various locations to optimize performance. - Utilize the waist Size C gearbox (Nema 23) and thigh gearboxes to balance the robot on X and Y axis using gyroscope data. The current hip parts' M3 hole arrangement is incompatible with the new version of Size B gearboxes. Remix the model or drill new screw holes manually until the updated design is released this Christmas. Don't forget that you'll need 50mm M3 screws with nuts to secure Size B gearboxes and their bearings in place, as omitting this will lead to delamination when lifting one leg. **A bit of speculation:** Once the Y-axis gearboxes are reintegrated, they should be positioned close to the center of gravity. This means not being parallel to the leg but slightly skewed towards the center, almost touching each other. The reason for this is that those y-axis gearboxes will act like a crane supporting the upper body's weight. The farther away from the center of gravity these gearboxes are, the more torque they'll require to prevent collapse. Imagine trying to walk with legs 1m apart! Try holding a broom in your hand and see how hard it is to lift when held at the tip versus right by the brush cap. Theoretically, the closer together the hip gearboxes are, the less torque output we can get away with. Check out the 2nd photo of HRP-2 to see what I mean. Notice how those joints are even smaller than the ones on the shoulders? Impossible! **Aren't these gearboxes too slow for a bipedal robot?** No, they're only slowed down for safety reasons. And yeah, it's even slower if you only get a few steps every time you press a keyboard key. The code will need to be rewritten so that stepper motors can move as long as the keyboard key is pressed and stop upon release. This means moving 5-6-7-8-9-10-11-12-20 degrees, releasing the key, and stopping (only for manual control). With gyroscope control, they'll move constantly. Using STM32F103 modules instead of Arduino Nanos will also speed these up due to their faster microprocessors. This is especially important when operating multiple stepper motors with one Arduino, which was the reason I used one Nano per motor!