Papers on Low-Cost Full-Scale Mobile Manipulation

[Tony Pratkanis]

Hello All,

I have been reading up on papers on low-cost full scale mobile manipulation. There's a lot of smaller experiments such as the LeRobot and the LeKiwi, but these don't have a lot of range or height they can grasp at. I found several interesting papers.

XLeRobot - this is a mobile base by placing a Lekiwi base under an IKEA cart, then mounting LeRobot arms on top of the cart. See https://github.com/Vector-Wangel/XLeRobot. I think this is an interesting idea, but it has low payload (400 g per arm).

AhaRobot - this is move complex to build but it features elevators and a SCARA-like arm design. See: https://arxiv.org/abs/2503.10070. This layout of SCARA + elevators means that joints are not under high torque at the base of the arms. It also has a higher payload (1.5 kg per arm).

There's also Nori Bot which appears to be a hybrid of these two approaches. https://arxiv.org/html/2605.16537v1. Also payload of 400 g per arm.

For payload, I have looked into average objects that people carry on a daily basis. One of the heaviest objects appears to be a milk jug at around 4-6 kg, so I think 6 kg total payload would be a good goal to achieve.

Anyway, has anyone else seen or built anything similar to one of these?

Thanks,

Tony

[Chris Albertson]

I worked on this problem before. Buying a system will be expensive, tens of thousands of dollars, since you’re outside the hobby range. 

For this project, buy a 3D printer that prints in high-end plastic and learn to use a free 3D CAD system like Fusion360.

It’s not rocket science. Start with a flange that hands can bolt to and decide on the payload and reaching distance. Design a wrist system that can do that. The elbow must lift the wrist system, payload, and elbow. Calculate the required torques at each joint them do a detailed design from shoulder outward.

Use high-quality bearings and avoid radial loads on the motor shaft.  I can’t say it enough: “bearings matter”. if you have poor ones you get machanical slop and flex.

Below is a low-cost human scale shoulder design using off-the-shelf motors and six identical 3D printed parts. But a full gallon of milk might be too much.

Arms are easy because they don’t need the speed legs need. Legs need speed for balance or “control bandwidth” for micro-level movements. Arms don’t need that, so you can use cheap geared steppers like in my design. You can iterate and improve it. It’s human-scale and low-cost, but only the shoulders are done.

Of course, the hardware is the easy part.   Motion planning is far harder.

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[James H Phelan]

Chris,

Nice work! Would like more details about the stepper motors and bearings you used, source, cost.  Any wisdom you can impart re selection.

James H Phelan
"Nihil est sine ratione cur potius sit quam non sit"
Leibniz

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[Dave Everett]

Great links Tony.

I use a linear lift to get my robot arm to the ground and up to a workbench height.

Dave

--

[Ken Gregson]

In the LeRobot "line" there's also the AlohaMini

https://github.com/liyiteng/AlohaMini. It uses a SO-ARM track axis for vertical linear motion/lift

https://github.com/avenhaus/SO-ARM100-Track-Axis

I'm building a couple variants of it AlohaMini "LeDomo" to keep my LeKiwi "Midori" company. Open question on how robust a PLA gear and toothed rack will be.

The SO-ARM-200 of the AlohaMini is more capable than the -10X  Arms.

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[Wayne Gramlich]

Greg:

That is really neat.  It is wonderful that the Aloha robot stuff has started
to migrate into robot hobbyist's robots.

I worked on the Aloha robots at Google as a contractor (OLogic) shortly before
my retirement.  Alas, my NDA is still in place, so I can only point a paper:

* ALOHA2: An Enhanced Low-Cost Hardware for Bimanual Teleoperation:
  * https://aloha-2.github.io/

Have fun,

-Wayne

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[Ken Gregson]

Wayne,

Thanks, I'm familiar with some of that work.

I think we are at an inflection point in the availability of more generally useful robots and their accessibility to hobbyist and DIY developers. 

We're hoping to build a group project around the AlohaMini in our local robotics club and develop that into a STEM course for high-school students. 

Best, 

-Ken 

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[Chris Albertson]

On Jun 13, 2026, at 4:05 AM, 'James H Phelan' via HomeBrew Robotics Club <hbrob...@googlegroups.com> wrote:

Nice work! Would like more details about the stepper motors and bearings you used, source, cost.  Any wisdom you can impart re selection.

This was intened for teleoperation and handing of small objects.     Only the easy part is done.     You need to select a hand.  I say “select” because there are many pretty good ones.   I like the “Yale OpenHand."  But it looks very “robot-like’.  THere are also open source prosthetic hands that look human-like and work well.   The Yale hands are far easier to control and do “grasp planning” and human hands need to be teleoperate by the human with gloves.

The link I posted goes to a model browser it s kind of clunky to use compared to a full CAD system but it will allow you to see bearing and motor details.    Try this…

Click the “flow chart” thing at the bottom now you can see a tree structure of assemblies and sub assemblies and parts.  The “eyeball” makes the visible or not.    make only one of the six link blocks visible.      Zoom in.    Next make all the 3D printed part invisible and what is left is the motor and ball bearings.   These are standard parts and the part number is the object’s title.    The bearing come out is “AST’s catalog and the Motoers are from “Stepper OnLine” and I used their part numbers.        

What is not shown in the model are detrital like threads in the holes or fasteners.  The bolt circles are generic holes not sized for clearance or threads tapping.   I think the blocks could be printed in ASA, ABS or even carbon-filled version of that.  And the other parts could be aluminum or in a prototype plastic.        The same Fusion360 design files can drive either a printer of a CNC machine.

About plastic.  I find I can use it except where there is consetraited stress.  For example a pulley that has to fit a motor D-shaft with a gib screw. The D and screw will scrip LONG before the timing belt slips a cog. SO I make metal pully hubs and press fit them into plastic timming pulleys.  They last “forever”.  Just press them in with a hammer and CA glue.    Details like this are not shown.  The moters would likey strip a plastic keyway.   That explains the stupid design where the bearing areas of the bolts is 5X larger then the key slot,   One is plastic the other is metal and metal is 5X stronger, at least.

The 3D models of the bearings and motor are from the manufacturer.   Almost everyone who sells machanical parts has links to CAD files.  Even McMaster Carr has models of every screw and nut they sell and you really have to use those models when you do a design so you are 100% sure the parts will fit.

The shoulder uses 6 identical sub assemblies for one good reason, I can build one and test it, make changes and then test it for weaks with a dummy weight attached and then after it work build five more and be pretty sure it will work.   

I am very slowly now working on a “dog-robot” that has 4 legs each made of three identical assemblies. so 12 total.  The hang-up is a moter with enough power that is light and inexpensive.  Drone moters are the way to go here.

Geared stepper moters are very heavy but for this one use case here the weaight is in the sholders and not the hands and the shoulder weight goes to wheels, weight does not matter.   I would not use stepper in a walking humanoid robot.    This robot was going to be a humanoid in a wheel chair, literally, using a moterized wheelchair as the base.  It could work in any ADA complaint wheelchair accessable space.   Then I decided I did not want such a large robot in my house and workspace. and moved to a small dog bot.   That worked well enough but because I went for cheap moters the prefromance is poor, it will never jump or run.

You will 100% need a 3D CAD system,   Eyeball-engineering does not work wit a system this complex and you have to think about things like wire routing and if a hex screwdriver can actualy reach each screw.  All before you print the first part.

Arms are easy because they don’t need the speed legs need. Legs need speed for balance or “control bandwidth” for micro-level movements. Arms don’t need that, so you can use cheap geared steppers like in my design. You can iterate and improve it. It’s human-scale and low-cost, but only the shoulders are done.

Of course, the hardware is the easy part.   Motion planning is far harder.

On Jun 13, 2026, at 12:17 AM, Tony Pratkanis <a...@pratkanis.co> wrote:

Hello All,

I have been reading up on papers on low-cost full scale mobile manipulation. There's a lot of smaller experiments such as the LeRobot and the LeKiwi, but these don't have a lot of range or height they can grasp at. I found several interesting papers.

XLeRobot - this is a mobile base by placing a Lekiwi base under an IKEA cart, then mounting LeRobot arms on top of the cart. See https://github.com/Vector-Wangel/XLeRobot. I think this is an interesting idea, but it has low payload (400 g per arm).

AhaRobot - this is move complex to build but it features elevators and a SCARA-like arm design. See: https://arxiv.org/abs/2503.10070. This layout of SCARA + elevators means that joints are not under high torque at the base of the arms. It also has a higher payload (1.5 kg per arm).

There's also Nori Bot which appears to be a hybrid of these two approaches. https://arxiv.org/html/2605.16537v1. Also payload of 400 g per arm.

For payload, I have looked into average objects that people carry on a daily basis. One of the heaviest objects appears to be a milk jug at around 4-6 kg, so I think 6 kg total payload would be a good goal to achieve.

Anyway, has anyone else seen or built anything similar to one of these?

Thanks,

Tony

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[Chris Albertson]

On Jun 13, 2026, at 7:45 AM, Ken Gregson <ken.g...@gmail.com> wrote:

Wayne,

Thanks, I'm familiar with some of that work.

I think we are at an inflection point in the availability of more generally useful robots and their accessibility to hobbyist and DIY developers. 

We can build nice puppets that must be teleoperated, and we can build what are basically CNC machine tools that run scripts for prerecorded motions.   Look at Elon Musk's robot demo at Universal Studios a while back.     The guy has nearly unlimited funds and an army of robotics engineers, and he literally had to bolt the robot’s feet to the floor so that robot dancers did not fall over.   Yes, fixed-feet screwed to the floor.      His other robots could walk on flat surfaces but not step up or down a curb and still needed full remote control.     And THAT is with a billion-dollar budget.

Even Boston Dynamics’ “Atlas” that can run up a ramp and do a backflip while jumping off a platform.     That was all programmed using motion capture for a human performer.   If you were to move the ramp two feet, Atlas would run into a wall and fall down.   

I’m not saying it was not hard; Atlas had to do a ton of computation to reach the motion targets that were recorded.  It was MPC done in a server room; it was a huge optimization and search problem.   But in the end, it was a dancer who invented the performance.  The robot was a puppet.   This is the best that the best organizations can do in 2026.

We are genetically programmed to be fooled.  As social animals, we use our own brains to predict what others might do.  When we see a human, we assume they are like we are and operate the same way.  Our brains place us in their shoes and predict what we would do.    We use this without thinking about it.      We even use this to place ourselves in different situations and figure out what we would do if things were different.         This is not uniquely human; monkeys and chimpanzees and dolphins all do that some thing.

So when we build a robot that looks human, we trick people into thinking that the robot walked across the room because it wanted to be on the other side.  Or with CPT-chat, we think it “figured out” a problem like we would.   Some research showed that simply placing a happy face sticker on a robot enhanced this instinctive social animal trick.    This effect makes us think robots are dramatically more advanced than they really are.  We can’t be “un-fooled” 20 million years of evolution burn this into our DNA.

I don’t think we are very far along; we can make animated mannequins that are as smart as a toaster oven.   I’m not saying that as a criticism, but rather a challenge. The future is wide open, and one smart guy can still make a revolutionary discovery.   AI researchers in 2026 are like physics was before Isaac Newton.   The basics are still to be discovered.   It is good to work in this field.

But robots do make a good subject in a classroom.  Students need to learn how to solve problems like “How many M4 screws, in single shear,are needed to transmit 700 cm kg torque using a 75mm bolt circle?”   Or what rotation sensor accuracy is needed to give 1mm precision at the end effector or 100 other simple robotics engineering problems.   Those are both good high school level problems covering static cases.        Movement quickly gets harder mathematically and gets you into 2nd year university level math.   Motion planning is a bit harder, and the AI to generate the motion planning target is not yet possible.

I think that is what makes robots interesting is that you can work at any level.

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[Stephen Williams]

On 6/13/26 10:17 AM, Chris Albertson wrote:

On Jun 13, 2026, at 7:45 AM, Ken Gregson <ken.g...@gmail.com> wrote:

Wayne,

Thanks, I'm familiar with some of that work.

I think we are at an inflection point in the availability of more generally useful robots and their accessibility to hobbyist and DIY developers. 

We can build nice puppets that must be teleoperated, and we can build what are basically CNC machine tools that run scripts for prerecorded motions.   Look at Elon Musk's robot demo at Universal Studios a while back.     The guy has nearly unlimited funds and an army of robotics engineers, and he literally had to bolt the robot’s feet to the floor so that robot dancers did not fall over.   Yes, fixed-feet screwed to the floor.      His other robots could walk on flat surfaces but not step up or down a curb and still needed full remote control.     And THAT is with a billion-dollar budget.

...

I don’t think we are very far along; we can make animated mannequins that are as smart as a toaster oven.   I’m not saying that as a criticism, but rather a challenge. The future is wide open, and one smart guy can still make a revolutionary discovery.   AI researchers in 2026 are like physics was before Isaac Newton.   The basics are still to be discovered.   It is good to work in this field.

We need good hardware widely available that is very inexpensive.  And to be working on the AI/ML/etc. in parallel as that hardware develops.

I'm working on the hardware side.  I can't wait to graduate to focusing on the software.

Stephen

But robots do make a good subject in a classroom.  Students need to learn how to solve problems like “How many M4 screws, in single shear,are needed to transmit 700 cm kg torque using a 75mm bolt circle?”   Or what rotation sensor accuracy is needed to give 1mm precision at the end effector or 100 other simple robotics engineering problems.   Those are both good high school level problems covering static cases.        Movement quickly gets harder mathematically and gets you into 2nd year university level math.   Motion planning is a bit harder, and the AI to generate the motion planning target is not yet possible.

I think that is what makes robots interesting is that you can work at any level.

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[Steve " 'dillo" Okay]

On Saturday, June 13, 2026 at 12:17:36 AM UTC-7 Tony Pratkanis wrote:

Hello All,

I have been reading up on papers on low-cost full scale mobile manipulation. There's a lot of smaller experiments such as the LeRobot and the LeKiwi, but these don't have a lot of range or height they can grasp at. I found several interesting papers.

XLeRobot - this is a mobile base by placing a Lekiwi base under an IKEA cart, then mounting LeRobot arms on top of the cart. See https://github.com/Vector-Wangel/XLeRobot. I think this is an interesting idea, but it has low payload (400 g per arm).

I have a stalled project that is using a Hackerbot base, some 8020 and one of these:
https://www.instacart.com/products/24770773-polder-undersink-storage-caddy-grey-17-x-10-1-2-x-16-1-2-each

as a similar system. 

Stalled only because I've either had work or work-related things to attend to. 

I like the idea of the dual arms, but really, I just need a mobile base with a tool-caddy to follow me around and hand me things when I need them. 

I've got a set of LeRobot arms, the base, the cameras, a scattering of RPi's . 
I just finished a short-but-intense 3-week contract(which involved LLaMa & VLA/VLM training & testing)  

Maybe I'll have time to get back to it for a bit now(?)  

'dillo

[Steve " 'dillo" Okay]

On Saturday, June 13, 2026 at 6:34:45 AM UTC-7 Ken Gregson wrote:

In the LeRobot "line" there's also the AlohaMini

https://github.com/liyiteng/AlohaMini. It uses a SO-ARM track axis for vertical linear motion/lift

https://github.com/avenhaus/SO-ARM100-Track-Axis

I'm building a couple variants of it AlohaMini "LeDomo" to keep my LeKiwi "Midori" company. Open question on how robust a PLA gear and toothed rack will be.

There are a growing number of "Tough" PLA blends out there, along w/ some other interesting materials like PCTG(not PETG) that are ballpark-ish cost to traditional PLA but

are significantly stronger. My point being: The "PLA" available in 2026 is not the PLA of 10 or even 5 years ago. 

'dillo

[Chris Albertson]

What you need to do is print some stuff then break it.

I was also curious and set up. motor and tsome gears and a dummy load made with a string wrapped around a drup with a weight in the drum.    I used a stepper motor to raise and lower the weight.

Firt off are the obvious results you wouild =knpow going in.

1. 3D prints are not are precision made as metal gears so you hhave to price a minimum gear tooth size such that the defacts are vert small compared to the size of the geat tooth.   You end up with a fairly large minimum size

2. Plastic is not nerly are strong as metal.  Lets say it is 5 times less strong.  So for the same strength you need to mke the plastic geat 5X larger thn a metal gear.   #1 and #2 actaul work toto gather, the ger need to be 5 or 6 times larger to large teeth “work”.

Next is a fast  that should have been obvious.  Gears have friction when they mesh, friction produces heat and this is the main caise of failure.   If you heat PLA even a tiny bit it becomes soft and then is VERY weak and deform and then you have run-awayf riction heating and soon teeth shear off

So you REALY, Absolutly want a kind of plastic that can take heat.  At the very least use ABS.      I think the effect is at the micro scale.  The entire gear did not heat up.  I think only at the small area what contact is made.

Het resistance plastic helped a whole bunch

“Eyeball engineering” does not work.  Our experiance with metal gear makes us think “these gear look rel stong” but we are wrong.  Do the math and yes they will be “fricking huge” and then use white grease and heat resistance plastic and they work well.

When the teeth are problely size as above, the failur pint is ALWAYS the hubs wher the connect to the motor shaft.  You wil strip out D-holes, splines and grub screws.   The only solution is to make metal hubs and press-fit them into the plastic gears.  You can make a metal hub by slicing a 3/4” metal rod (mild steel is hbest) drilling a center hoe and dilling an tapping from grub screws and th force it into a platic hole on the get, maybe use CA glue.     I’ve been using these for a couple years now.

One more thing:   Plastic timing belt pulleys seem to work MUCH better then plastic gears.   

Bittom line, PLA fails quickly.  The first thing is “spalling” and then shear off the teeth.   But of couse you can scale it up and go to Module 6 teach and 25mm face widths but then it can’t fit inside the robot.   Metal is MUCH more space effecent.

I built a CNC machine by. modifying a Harbor Freight manual mill.    The harder part was the vertical rack to move the milling head up and down.   The best solution was a ball screw.  They are nearly frictionless, don’t cost so much and can move hundreds of pound of weights.      SOmething like this might work. This is NOT a lead screw.  The nut is made of balls the recirculate.   The ball screw suported the vertical load but the two rails and four slider blocks contrain the motion to only one vertical.    You might even use four rails wit ht eball screw in the center.     You are basically building an elevator. that rides on ball bering.     You can easy get 1/100th inch accuracy wit this Amazon parts and a good closed-loop stepper motor.   I picked the sizes at random because I don’t know what you robot weighs or how far it needs to move.

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[Ken Gregson]

"There are a growing number of "Tough" PLA blends out there, along w/ some other interesting materials like PCTG(not PETG) that are ballpark-ish cost to traditional PLA but

are significantly stronger. My point being: The "PLA" available in 2026 is not the PLA of 10 or even 5 years ago. 

'dillo"

Good point, haven't experimented with PCTG yet. I've been pleased so far (except maybe with picking all that support material from the teeth in the track ;-). But -just in case- have printed a version with a flat instead of the track to which I could imagine affixing any number of things including a more robust CNC milled toothed rack. It's also perfect for working on the base without the "distraction" of the arms.

So many possibilities!
- Ken

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[Chris Albertson]

If you are talking about gears, heat tolerance is the primary consideration.    Strength is not nearly as important because if it needs to be stronger, just make it bigger with a wider face width.   

About a rack, just use a lead screw.   A rack used to lift means you are constantly needing to supply torque,  Lead screws are not back drivable

Belt drive work better then gears if you are printing, they last forever and have the same torque and power requirements as racks.  Bit they are back drivable so the load falls if power is lost.    

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