Category: Social Robot Design&Build

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am ordering materials for the artificial muscle I’m going to be working with for a while. Let’s get started!

The McKibben Artificial Muscle

In my research this week, I learned the pneumatic muscle I’ve chosen to start prototyping with is in fact called a McKibben Muscle. An inner sleeve is typically made out of rubber. A fluid –usually air– is pumped in through an endcap. The sleeve expands radially, a woven outer casing translates that outwards expansion to a lengthwise contraction.

I’ve seen several tutorials on how to make these muscles online. The greatest design freedom is in the endcaps. They can be as simple as a clamp or complex enough to need a 3D printer. Their functions are to hold the inner sleeve and outer casing together, seal them off while still allowing air in and out within the greater pneumatic system, and provide mounting points to work on.

Materials Shopping

The most important part is the outer casing. I will be using cable management sleeving like what protects the cords coming off the power supply in my main computer tower. Squish them, and they expand: same principle in reverse of the muscle. I remember at least a couple sources saying to use nylon, but a little shopping yielded a selection of tubes made from polyethylene terephthalate (PET).

Tubing is almost as important as the casing. As long as it keeps air inside the muscle, it should work for all I know right now. I talked about it with my father while walking the dogs, and we figure longer-term durability will be best served by a rubber tube a bit thicker than a balloon, but not so thick it’s near difficult to inflate.

We’ve talked about an air source. Compressors are loud and bulky. Lower end models lack a tank for storing pressure, which I will need for anything resembling a decent response time. We also briefly considered getting a SCUBA tank, but those run more than a compressor and most certainly cost to refill. Whichever option we end up buying, this will be the most expensive part.

We’ve only baerly started brainstorming endcaps. My father proposed using a nut and a pipe clamp for one end, but I’m having trouble imagining how that will look while trying to attach a mount point. Perhaps some PVC piping will be involved after a trip to a hardware store. I can have a T pipe with a plug for a mount point across from the muscle and an adapter to the air supply coming off the tail.

Takeaway

The main consideration for buying parts at my stage is matching size. It won’t do to have an inner tube that barely fits in the expanded profile of the sleeve.

As noted above, it would seem everyone showing off their air-powered muscles has a slightly different design depending on his or her available tools. I don’t have access to a machine shop, so I won’t be modifying any metal parts. Neither is my 3D printer working right now: printed parts will need to wait.

I’m excited to start testing.

Final Question

What variables do you expect will affect the quality of my McKibben muscle design?

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am following up on last week’s post, covering my brief corrispondance with Artimus Robotics. Let’s get started!

I first approached Artimus through their site’s Contact Us page [1], where I provided some details about my project – a quadrupedal robot system aimed at hobbyists.

Sticker Shock

The next day, I received an email from Andrew Morton representing Artimus. “Our actuators start at $2,995 and it is another $1,995 for the rest of the kit (kit total starts at $4,990) [2].” He then directed me to the Application Assistant where I could provide more details about my application.

Ouch. I thought HASEL actuators were supposed to be made from relatively low-cost materials. But yeah, I understand: they have the research to pay for, they’re making everything to order, and it’s going to be more durable than something I assemble at home; and that’s just the costs I know about.

Lower Speccs

HASEL actuators reportedly compare relatively well to human skeletal muscle on several metrics [3]. I don’t need that level of performance. I’m also looking at potentially several dozen tiny muscles that only need a few pounds of pulling force. While it would be nice to see my robot galloping, jumping, and dancing, I’ll settle for standing up and walking around obsticles. Getting up and down stairs will be a luxury to strive for.

In all reality, I won’t need my eventual full strength actuators (I’m just going to call them muscles or artificial muscles for the remainder of this post) the moment I have my first fully assembled prototype – certanly not until I have the kinematics worked out. On the other hand, it’s not a bad idea to buy what you’ll need near the end with the idea that you’re not blowing money on as much intermediary equipment.

I went ahead and went through the Application Assistant. The form asked several important questions. What motion does my proposed actuator make? How much, hard, and fast does it move? How long should it last? What kind of space will it be installed in? How presicely controlled does it need to be? Will it need to be self-sensing? What are the most important characteristics you’re controlling for [1]? I answered as best I could, but I found myself leaving the form mostly blank or full of “TBD.”

I came to the last page where it asks for an overall description. I will also take this moment to note that I did not retain a copy of my exact wording, and none was ever echoed back to me. (If there’s one complaint I have with my experience, that would be it). I found myself weaving in most of the information I had put in different note fields, so I compiled it here and tidyed up on the other pages. I also expressed my concern at the up front cost, asking if they offered something like a junior developer’s kit for small scale projects.

Important Questions Without Answers

Hi [Shadow],

Thank you for providing the application details. Do you have a force or stroke specification for the actuators? These are the primary specs used to size an actuator. No problem if you don't have those yet as you're welcome to purchase a standard actuator development kit for preliminary testing to better understand the technology and your needs. I think that is the best path given the complexity of your project. 

We don't have any lower-budget actuators, just our standard actuators that start at $2995 or $4990 for the development kit. Please let me know if you would like a formal quote.

Thank you,

Andrew Morton [1]

At this point, I was coming to terms with the realization that Artimus will be out of my price range until I’m much deeper into prototyping. Even then, I may have a tough time keeping my unnofficial $5,000 goal unless the price comes down.

My reply ballparked my figures: a 20 inch robot, muscles ranging 1-4 inches long, 5-10 pounds of pulling force each, and the whole unit anywhere between 5-20 pounds [4]. Total guesswork on my part. But the focus was more on how my pockets weren’t that deep. I thanked Andrew for his time.

I still hope to work with Artimus in the future, even if it’s for my scaled up version.

Andrew got back to me in a third and final email, probably saving face as much as I was. As I suspected, they’re oriented around industrial clients right now, and smaller clients will be served well once economy of scale kicks in [1].

Takeaway

Going forward, it looks like homemade muscles will dominate my development process until I’m ready for something professionally assembled; my first prototypes may very well end up being powered by pneumatics. They won’t be untethered, but at least I can find the figures I need and get back in touch with Artimus when I’m ready.

Final Question

What artificial muscle technology would you recommend as an analogue for HASEL?

Works Cited

[1] Artimus Robotics. Accessed: June 29, 2021. Available: https://www.artimusrobotics.com.

[2] A. Morton. “Artimus Robotics Actuators” Personal emails (June 30-July 2, 2021).

[3] P. Rothemund, N. Kellaris, S. Mitchell, E. Acome, and C. Keplinger “HASEL Artificial Muscles for a New Generation of Lifelike Robots—Recent Progress and Future Opportunities” Nov. 2020 Advanced Materials vol. 33, issue 19, May 13, 2021 Available: https://onlinelibrary.wiley.com/doi/10.1002/adma.202003375. [Accessed: June 6, 2021]

[4] S. 8472. “Re: Artimus Robotics Actuators” Personal email (July 1, 2021)

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am writing in to the authors of the paper on HASEL artificial muscles (hereby referred to as the “HASEL paper” in this post)[1] I covered recently. Let’s get started!

How to Present Myself?

The HASEL paper was dense. I probably understood around 80-90% of it if I’m being generous. It’s an exciting, new technology, but I’m left with questions – questions that might send me looking elsewhere for parts if things don’t work out. I’m writing in.

But how do I present myself? I’m not representing some big company with a finished design; I’m a computer blogger with a dream at best and a wannabe entrepreneur at worst. I have a negligible following, I’ve never bothered to make sure my comments section works, and the default potted cactus theme from 2017 is still staring anyone down who visits.

At the same time, I’m more serious than a random Joe trying to look a little deeper into a novel idea before moving on. I dare say I’m more serious than the average hobbyist looking for a challenging project because I’m already thinking past the “it’s done, that was fun” stage. I want to see my robot out in the world, helping people.

The Letter

To the authors of HASEL Artificial Muscles for a New Generation of Lifelike Robots—Recent Progress and Future Opportunities or whomever it may concern:

I am a computer blogger with three and a half years experience working with Linux. I am presently conceptualizing an untethered robotic system primarily aimed at adept to expert hobbyists. I’ve read your paper, and I believe HASEL actuators show enough promise to warrant serious consideration for my project.

My goal for a version 1.0 is to produce an 18-20 inch tall quadrupedal social robot that doesn’t reach out to the Internet for its basic functions, like speech. By open sourcing the design, users can more easily service their robots and customize them to add character. Adventurous users could assemble their own units from kits containing pre-made artificial muscles, custom circuit boards, and –optionally– 3D printed bones or other parts they can otherwise manufacture at home.

If successful, I dream of the platform being upscaled as large as a miniature horse and serving in a similar capacity to service animals for people with disabilities. If the price can be kept in check, it may even be competitive against the cost of training a new companion animal every number of years. Where an animal might carry a general information card, a robot with an onboard conversation engine could communicate pertinent information in the case of a personal crisis: “My handler is fine. Please leave him alone until he sits up,” “Help! My handler requires XYZ assistance, but is unable to speak.”

A strong point of HASEL actuators I was drawn towards was the possibility of rapid prototyping techniques, but a notable part of the draw vanishes if I cannot prototype shell shapes out of my home lab – even if I expect to need professionally manufactured muscles as I move out of early testing and eventually into release/production. Do you have or plan to make any instructional material on how to develop a schematic which Artimus Robotics can manufacture?

My biggest concern is the operational voltage reported in the paper. Some strategies were proposed to mitigate risk, but are recent developments enough to lower the voltage for a product as described above? If not, do you expect the next 5-10 years will bring sufficient progress?

Shadow_8472
letsbuildroboticswithshadow8472.com

As of writing, I have not sent this letter in e-mail form or otherwise. Only when I sat down to start my write up did I think to instead contact Artimus Robotics (I just realized it’s spelled different than the Greek goddess so no help from spell check). Their site [2] even has a contact page I only laid eyes on last minute as I went to dig up an e-mail address I remember seeing in the HASEL paper.

Takeaway

While attending university, I tried contacting the man behind another exciting robotics technology for a research paper. No response. I don’t want a repeat, and they’ve presented a better method to facilitate first contact. It’s just the information in my now open letter will need to be spread out for the different format. I’ll do a follow up soon if things work out.

Final Question

Have you ever tried writing in to a company?

Works Cited/Mentioned

[1] P. Rothemund, N. Kellaris, S. Mitchell, E. Acome, and C. Keplinger “HASEL Artificial Muscles for a New Generation of Lifelike Robots—Recent Progress and Future Opportunities” Nov. 2020 Advanced Materials vol. 33, issue 19, May 13, 2021 Available: https://onlinelibrary.wiley.com/doi/10.1002/adma.202003375. [Accessed: June 6, 2021]

[2] Artimus Robotics. Accessed: June 28, 2021. Available: https://www.artimusrobotics.com.

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am continuing my research on my design for a personal robot. Let’s get started!

Situation Overview

In my last post on this subject, I introduced my overarching vision for an open source social robot aimed primarily at hobbyists at or around my skill level as of when I first got serious about this project: familiarity with Linux, a little experience with 3D printing, and the perseverance to see it through. This will not a beginner’s project. But that doesn’t mean I can’t plan on lowering the barrier to entry.

When all is said and done and I have my completed plans, any master level hobbyist is more than welcome to assemble one resistor by capacitor by electrode should he see fit. That doesn’t mean I won’t be able to arrange already cut or assembled circuit boards for those who need it. I might also arrange kits for people who just want to assemble their own robot from parts, and I can even possibly open up orders for fully assembled units.

HASEL Actuators

A major concern I’m designing around is cost. Motors are loud, bulky, and as expensive as they can be precise. Artificial muscles can typically be made for pennies on the dollar while offering a lot more design flexibility. They are, however, an overall younger technology.

While there are multiple possible designs floating around, I’ve been reading up on Hydraulically Amplified Self-healing ELastomeric actuators (HASEL), a relatively new technology within the relatively new field of artificial muscles. Imagine a baggie partially filled with oil. Paint or otherwise affix some flexible electrodes to magnetically squish together when a high voltage is applied, and you get the basic idea. The oil pushes out the sides of the baggie, causing the whole thing to contract lengthwise. There have been multiple generations of designs, each with its own improvements, drawbacks, and studies [1]. It makes for some very dense reading when authors use big words to talk about all of them at once.

My goal for right now is to start prototyping this month. Even if I don’t have a high voltage power supply to work with by then, I’m bound to learn something.

Citation Needed

To date, when I’ve needed to credit a work, I’ve listed a name in my text and thrown in a link. Citation was often my least favorite part of writing a paper, but I’ve decided that if I’m looking to be a little more serious about this blog, I really should start using appropriate citations when referencing things.

As I was finishing up this post, I looked up the format. School will teach MLA and APA as a given and Chicago if they’re up for some variety. It’s all a matter of what standard is being used in the field you’re writing for. From now on, I shall be using the IEEE standard as I am writing for the field(s) of technology and computer science.

Of note, the work cited in this post is actually one I’ve been digesting since at least early March, before it’s inclusion in a journal last month. I’ve accessed it multiple times, but I haven’t kept track of it. My father finally made a hard copy this week, so I’m “accessing” it from there in terms of citation.

In all reality, I don’t have a teacher marking me down for imperfect citations. The real goal is to let you guys know enough so it should be easy(TM) find whoever I’m talking about, even if a link dies. I’m also limited by what I can coax WordPress into doing, so proper indentation is not happening any time soon. I tried it. It broke the brackets.

Final Question

My post lengths vary quite a bit. About how long do you think I should aim for in terms of word count?

Work Cited

[1] P. Rothemund, N. Kellaris, S. Mitchell, E. Acome, and C. Keplinger “HASEL Artificial Muscles for a New Generation of Lifelike Robots—Recent Progress and Future Opportunities” Nov. 2020 Advanced Materials vol. 33, issue 19, May 13, 2021 Available: https://onlinelibrary.wiley.com/doi/10.1002/adma.202003375. [Accessed: June 6, 2021]

Good Morning from my Robotics Lab! This is Shadow_8472, and today, I have a very exciting project announcement, one I’ve been looking forward to working on since I started this blog. Let’s get started!

Introduction

I’ve always dreamed of having my own social robot, and while I’ve spent the past few months researching the subject in my spare time, I still feel like I don’t know the second thing about actually building one. Way back when, I heard Linux was the operating system of choice for the craft, and I’ve been here ever since, and I’d like to move on.

I want to make an open-source, ambulatory social robot that can hold on a conversation, operate independent of a host computer, and be buildable/affordable by an avid robotics hobbyist. I know I don’t have the skills, and technology may need to march on before all my goals are feasible at once, but I fully expect this project to take over ten years. I respect the open source community, and I want to start giving back.

Background

The field of robotics is about as developed as computers were in the 50 to 60 years ago: large, clunky models confined by their price tags to businesses or universities; commercial applications cultivate a public awareness in the commercial sector leading up to early adoption in the home with the number of use cases blossoming as the technology develops.

One future of robotics under development has robots built for socialization. Where robots of today may feel like little more than computers personified, social robots can bring a character to life in the real world. Imagine: an automated service may benefit from a relatable face. One robotic puppy now on the market is aimed at forgetful seniors who might be at risk of neglecting a living therapy animal.

Who says a robot must have a riged frame, run on servos, or use other parts that boost their cost? A number of artificial muscle designs are cheaper, lighter, and simpler to make. I’ll go into more detail in future posts, but the kind I’ve been studying offers a world of design possibilities motors struggle to replicate.

Finishing Thoughts

It is my hope that I can work on this mega project as I can, and post video updates every three months or whenever I reach a major milestone. I will still have other topics as projects come up, and I may even do side projects directly intended to practice/develop skills for this project. For this reason, I won’t be using my usual numbering system. The parts for this robot are mostly out there. I just need to assemble them and make up the difference.

Final Question

What would you do with a personality robot you could take anywhere?