In the 10 and 15 Kg tests, the actuator actually lifts the weights (you can see the string sliding near the pulley at the endo of the pull). However, it was diffficult to arrange a 20 Kg weight so I removed the weights and just measured the elongation of the spring (previously calibrated with weights)
Assuming that motor is similar to the one I tried, you can replace the bottom 8x22mm bearing with 10x22mm and stick the machined end of the ballscrew up into the motor so it's turned directly instead of needing all that coupler business.
Super cool. Do you intend to post any plans, drawings, or parts lists? This would be fun to recreate. It seems like this actuator could be strong and fast. Also the design seems like could be adapted to bipedal robots as legs or arms. Seems like it would be fast enough to handle balancing operations.
That is the idea, next video will show a 3DOF leg for a quadruped based on this actuator. If you are interested yo can contact at hoxrobotics@gmail.com
It's a clean design. not how I would have designed it, but I'm curious to see how it works out. I suspect that you're going to have some difficulties when it comes to tuning the balancing over uneven terrain.
Maybe I'm missing something, but the way you used that axial bearing confuses me. At best it only takes up load in one direction, in the other the motor bearings take all the load. But I can't see what the axial bearing is transferring the load to even in it's working direction if that aluminium bearing block is not fixed to the tube rigidly. Other notes, steel ball bearings on aluminium tube will wear and marr up the aluminium quite quickly, especially since the ball bearing can't actually roll against both at the same time, it will slip against one of them.There are off the shelf POM coated rollers that play nice with aluminium though.
Yes you are right, the axial bearing only takes up load in one direction. If this actuator is used in the knee of a quadruped that is enough since the knee will only exert forces in one direction (leg extension). Note that the aluminum bearing block is fixed with four long bolts to a circular aluminum plate that also holds the motor. That bolts take all the load (tension). Sorry but I dont understand your comment on the steel ball bearings
Very nicely explained. Thank you for this video. I would like to learn more about this design. Is there a technical term for this actuator design? What terms can I use to search on Google? Thanks in advance!
@@DresdenFPV Not a bad idea, but finer threaded screw can slip more easyly, in the same diameter, because the screw profile is more thiner. It is good for pecision stuffs but if you need torque i gues thicker screw profile is key. I know gearboxes are a bit difficult to make, but if you use gearbox you only need to change motor speed and you get a fast and strong actuator. These days all 3 phase motor is expensive, but u can cheat a bit on price if u go for rpm instead of torque, if i remember it right.
The torque is enough for a quadruped, but it needs to be faster. For that reason I have replaced the motor with one three times faster (170KV) and more powerful and the actuator is now very fast (with similar torque). Check my next video to be uploaded soon!
While it could make the leg chunkier , there is a fully 3D printed actuator made by Rbotics labs that weights 1kg ,has a maximum torque of 44nm and a continuous torque of 28nm , you could put that actuator to either move the leg or put it as a replacement of the 6 NM brushless motor that you used
That motor is faulty and something is loose inside and makes that noise. I have replaced it with a faster and more powerful motor and it is now quite silent.
I have replaced the motor with one three times more fast (170KV) and more power and it is now very fast (with similar torque). Check my next video to be uploaded soon!
yes, especially because Sketchup is made for architects and so I highly advise to switch from it. But it is as you want and feel comfortable @@HOXrobotics
steppers are rarely a good choice for mobile robots. they consume power pretty much all the time. and for a compliant mechanism you'd need an encoder anyway.
I agree with @IronReign. Also, there are lots of very powerful and relatively cheap RC plane, drone and skateboard brushless motors that are a very good choice.
At the end of the video you can see how I calculated the torque: The leg pulls a spring and I measured the its elongation. The spring was calibrated previouslu hanging weights to it . I also used counterweights attached to the leg.
Thanks for a pleasant and interesting video 🙂 1. Normalize the audio. 2. Perhaps some of the most obvious pointing of e.g. sliders or cables from A to B is a bit superfluous i.e. video could be trimmed a bit. Subscribed! 😊
You are right, it needs to be faster. For that reason I have replaced the motor with one three times faster (170KV) and more powerful and the actuator is now very fast (with similar torque). Check my next video to be uploaded soon!
