My Advanced Realistic Humanoid Robots Project

Here's my completed V2 archimedes pulley system finally done! It is 16:1 downgearing and this pairs with my 2.77:1 downgearing on the turn in place pulley on the motor for a total of 44:1 downgearing.

Here's progress on a return spring for extension of the finger after pulley system has caused it to grasp.

Sorry, but you are on a dead-end approach.

You need to prove each separate joint for strength and repetitive loading without degradation.

I cannot see that your string system can ever match basic human strength and speed.

You have also claimed in the past that other robots cannot match human movements & fluidity of movement. See below.

This is the weight handling chart for routine workday loads a typical person can handle safely - so not near maximum capabilities, but safe for repetitive, eight-hours-a-day lifting as in a warehouse etc.



So eg. 10Kg at elbow height, lower arm straight out. If your mechanics cannot handle that from arms straight down (the 25Kg block position) at human speed and thousands of times without degradation, then you need a different approach.

And the hand/finger grip strength needs to take that weight loading and grip on the items being handled.


An athlete can exert far more force than that!

Existing robotics has already reached human-level fluidity of movement and athlete-grade strength in a human size body; and improvement are ongoing.

The electric version of Atlas has got to this level of movement in roughly a year since it's first release:

@rjenkinsgb All valid concerns. I have my doubts as well. I really don't know how well the string will hold up over time. That will be revealed in the testing. So far my focus is just on perfecting a single finger joint actuation, and testing that thoroughly. Validating my design and tweaking as needed until it is proven successful. If it doesn't work it's back to the drawing board.

On this point: "You have also claimed in the past that other robots cannot match human movements & fluidity of movement." --- some clarification is needed by me to clear up a misunderstanding here. I was referring to human passing robots when I said this, NOT mech style humanoid robots. We don't really have proper names to distinguish between these two types of humanoids so that is what I'm calling them: human passing humanoid robots vs mech humanoid robots. Mech humanoid robots like the ones being pushed by BD, Figure, and a dozen other companies are not at all what I was referring to when I made that statement. I don't think they are comparable, they are a totally different beast, entirely different design constraints and goals, will never pass for human in appearance, are apples and oranges. My project has almost zero overlap with them. Human passing robots cannot repurpose their design approach in any way. They are not at all close to human in appearance and never could be. Don't look real. Don't have to fit the space constraints human passing robot designers are challenged with.

Thanks for the thoughtful feedback I really appreciate it!

Ok so I did a big refactor of my pulleys and ran a test again and it still is not working. The first set of archimedes pulleys tops out and can't move anymore while the finger still hasn't moved. This is because of slack in the lines. I did not calculate slack in the lines into my calculations at all and am shocked by how much there is... Rather than do a major new overhaul with new math and new draw distances on every pulley AGAIN, I'm going to just drop the final pulley of the system so instead of 44:1 it will be 22:1 now. While we cut half the grip strength with this move, this might be okay after all. It still gives us 20lb of of burst grip strength I believe and 11lb of casual easy sustainable grip strength. Most common tasks should only require 8lb of grip strength anyways for a single joint tops. Because remember, I'm not doing a single motor for all 3 finger joints but one motor per joint which helps alot in the strength department and control department. So anyways, this hack I think is okay also because it hit me lately that I highly doubt I'd use the full beast mode burst strength of a 44:1 downgear anyways. I'd be too worried about the wear and tear on the fishing lines and pulleys and maintenance times getting too short between maintenance overhauls if the robot is using that level of grip strength for tasks. In reality, I am now imagining I will only let the robot do VERY minimal strength stuff to reduce the maintenance to a minimum. Like sewing, cutting, and delicately picking up small loads. I will treat it like it has the strength of my 4 year old just to baby it and make it last longer between repairs. Kind of like having a old beater car you don't trust and never throttling the engine hard but just gradually easing on the gas pedal to avoid blowing a gasket so to speak and avoid a trip to the mechanic. So that said I think 22:1 might actually be okay. And with that final pulley out of the way, I'll have WAY more than enough draw distance to bend the finger 90 degrees and account for string slack AND account for string stretch over time without any issues at all. Much better. Not to mention we do pick up speed this way and that might be a VERY nice feature when all is said and done. A faster moving finger can speed up its work I think. Like notice how 3d printers go way faster and that speeds up prints. So speed might be king over grip strength in the end perhaps. It's a tradeoff.

Another update is I realized I can wind a second very fine 0.08mm fishing line on the output portion of the winch in place pulley mounted next to the motor and this second line coming off that pulley will be attached to a tension spring consisting of a bracelet jewelery making cord for jewelry for kids. This line will maintain tension on that winch in place pulley and the motor output shaft at all times to prevent derailments. The metal tension spring that extends the finger will then have the help it needs to keep the whole system taught. That's the plan anyways. The runout of this line will need to be 12.48" of tensioned draw. To achieve that I need a length of this cord of about 15" I think which stretches to 27.48" at full extension. This would occur each time the motor causes the grasping actuation and it would be playing tug of war with the motor so that when motor relaxes or reverses direction, the winch in place is remaining tautly in opposition.

A note on fishing line durability. I think this was mentioned in passing quite a few times but at some point, a mention of durability concerns becomes that final mention that makes you really start to question it more and so I finally did some research on chatgpt and found out a human finger joint probably will actuate like 1-2k times per day which blew my mind since that would add up to like 10-30k times per month and so basically, once a month the main finger fishing lines will likely need replacement. I looked into alternative materials but didn't have much luck. So what to do?

Well after thinking about this a fair bit, my conclusion is to just shrug and move forward as it stands with the fishing line approach. I'll treat them as a consumable. My plan now is to just expect 1 hour of maintenance for every 20 hours of runtime. Or maybe to be more conservative, lets bump that to 1 hour of maintenance to every 10 hours of runtime? Maintenance will involve redoing pulley systems with fresh fishing line, or swapping in full new pulley systems to replace older ones every so often. It can have a pre-emptive maintenance schedule. My intention is that one robot will maintain his neighbor and the two will have a buddy system of maintaining eachother. Once I have expected time to failure of fishing lines established, they can swap in new ones automatically to prevent failures from happening during work times.

I don't think this is too bad of a deal or a deal breaker. Yes, hopefully materials advances will give me a better string one day, but for now, I'm okay with this maintenance scheduling thing. As long as its all automated, I think this is fine.

After all, our bodies muscles constantly need repairs and they grow from the repair process. So what do you expect for artificial muscles that can't self heal? Maintenance has to be a regular thing IMO.

Update: I bought several sizes of kevlar string to use to replace the PE fishing line particularly in the high tension areas that may face the highest durability challenges. I found it on amazon in many sizes. I just bought one of each size: 0.5mm diameter 50lb test, 0.8mm diameter 100lb test, 1.1mm diameter 200lb test and 1.3mm diameter 300lb test. This is probably a game changer for my project IMO.

After further consideration, I'm scrapping using the elastic cord for a bracelet idea (as a tension spring for the winch in place pulley). The point of that was to use as little space as possible but I just don't trust it. I am not sure what material it is made of and my experience with rubber bands has always been dry rot issues. I am going with 2mm OD tension spring instead. It has to stretch 12.5" and so I'm using a 12.7" strip of it to start. That feels like a snug stretch but does comfortably reach the 12.5" of stretch needed. This brings its stretched total length to 25.2". I bought 3mm ID 4mm OD TPFE tubing to be its guidance tube for this. That arrives tomorrow and then I can begin assembly.

This 4mm OD guidance tube is a bit bulky and long for the arm IMO so I will relocate it to the torso since if I use this method for other motors these 4mm OD tubes will add up in space taken up fast. The arm can't house them - it's just too much space taken at that point for these. But the torso can house them in the back or sides I think. For now, since the torso is not yet attached, I'm going to place this tube ON the string suspended from my ceiling and treat that string as though it were to torso for now.