Introduction: 3D-Printed Biologically-Inspired Robotics

I take over been spending the last hardly a months doing explore into biologically inspired robotic structures. Patc my draw near may appear formalistic in nature, these devices were simply a means for at long las conducting societal explore. This desire stems from my experience construction Simple Bots, and their resultant display at multiple Godhead Faires.

While displaying these robots, I determined that the thousands of people who interacted with them, projected their have social realities upon these devices which were little more motors hurry tied to pliant home utensils. The obvious shortcoming of the Simple Bots feeler was that no matter what personalities people projected upon these creations, they at long las implicitly interpreted that these creatures were robotic.

This led me to wonder what would happen if I built robots that were more intentionally organic-like and fluid in motion. Would hoi polloi perceive them as organism even many alive? Was thither a threshold where the great unwashe would stop perceiving them as robots and jump perceiving them as people organisms? Yet, before I could answer these questions, I needed to figure down the mechanism that would leave these motions.

Spell I could have explored a number of different fabrication processes, I recently base myself with untrammeled access to eight Objet Connex 500 3D printers. Aside from having an incredibly high print answer, what makes these printers unique is their power to photographic print digital materials with a ample range of hardnesses and colors. These printers au fond allow the antithetical materials to be mixed jointly to make up a Pantone-wish scale for material hardness. This was specially compelling for this type of robotics because IT would provide the power to print highly accurate assemblies that at the same time controlled rigid and supple materials. By impression materials with different hardness, deform, stretch, and tortuosity properties, I would be able to print life-like joints and musculature. With this in beware, I set out to make biologically inspired designs using 3D printing technologies.

All digital models were created using 123D Purpose happening account of its informality of use, and ability to be downloaded and utilised gratis. This is an intentional decision to make the project open, and modifiable. Information technology is my hope that others will Be able to download my files, iterate upon my solutions, and ultimately expand my explore. All content contained herein is licensed with a Fictive Commons 2.5 Share-Alike Non-Commercial Attribution license.

Step 1: A Note on Evolution

When I started to write this guide, my initial captive was to call it "How Not to Build a 3D Printed Robot." When explaining this want to a colleague, I arrived at a new potential title which was "Failures of Robotic Evolution." However, comparing robotic design to evolution is problematic in a number of regards, and opens upward a large tail of worms. As Steven Vogul arguest in "Cats' Paws and Catapults," the design and evolutionary processes should non be conflated.

Most notably, Vogul points out:

  • "nature is not alone glacial in speed, but lacking in versatility"
  • "most variations [mutations] are either objective or detrimental"
  • "design comes hard, and once achieve it disseminates entirely inside a stemma"
  • "diversity in nature represents superficial features of an exceedingly fusty and stereotyped character"

He then goes on to explain how for human innovation, pattern is a much better model because fundamental design change faces no evolutionary barriers. For instance, a invention can glucinium fundamentally changed without taking into consideration the motive for each subsequent loop to allow perfect functionality to perpetuate the continuity of its lineage. Nor do we have to account for increment or grading of the aim over its lifespan. Humans are only limited by the materials impending, the existing knowledge base, and ingeniousness. Humans are likewise free to take over, adjust, and remix designs at volition. About challenges for human being design innovation tend to be social and/or legal, non formalised.

While it Crataegus laevigata cost tempting to draw robotics in price of evolution, I think it is better to view IT as an iterative aspect process. This process, while very similar to evolution, is noticeably divergent. American Samoa development repeatedly demonstrates, most change is detrimental, blind and slow. Iteration, on the else hand, is (ideally) beneficial, intentional, and straightaway. One rarely iterates if they don't imagine the subsequent version is going to be an improvement Beaver State will illuminate something that will help to move other iterations forward. Just atomic number 3 organic fertilizer-like machines are similar to life, but non replicating information technology; so is the case that the process for making these machines should make up evolution-like, but not a perfect repeating.

Measure 2: Research Methodology

Extraordinary last matter I essential make note of before I proceed is that the research controlled herein is "artistic research." I make this differentiation to highlight that my goals and methodologies as an artist are non that of the railroad engineer or man of science. I oft wish to remonstrate to people that as an artist I am free to explore the most newsworthy result, non needfully the best solution. In fact, very seldom is it the most interesting solution the best solution. I likewise ingest the freedom to search many pathways, and make what scientists would deal leaps of trust. So, As you show this, please keep in mind that I am aware that my approach is not truly knowledge domain, many of these technical issues are solved problems, and much more efficient mechanical solutions Crataegus oxycantha be. The most efficient mechanical solution is not what I am interested in exploring, and it is not my goal to repeat this prior work.

In doing this, it is my end to create robotic agents that can aid us meliorate realize the relationships between ourselves and our technology. While it may seem like I got lost in a web of formalistic considerations, please bear in mind that my ultimate goal is to give abstracted biologically-inspired robots intended to capitalize happening our present mental associations, and elite group relationships. I am non difficult to explicitly promote the field of engineering, nor am I trying to alone understand abstract ethnic constructs. My goal is to find a holistic glide slope that acknowledges both, but does not party favor either.

As Simon Cent points out in Bridging Two Cultures (2005):

"It [machine artwork] is interdisciplinary because it pursues technical research which exceeds the constraints of the objectivist-positivist spare-time activity of knowledge per se and likewise exceeds the base constraints of production of technological commodities for market, because it is motivated by and coeducational into larger socio-taste flows."

Hopefully some of what I divvy up here will avail contribute to and push forward 'more real' objectivist-positivist scientific inquiry. Sir Thomas More importantly, I Hope to provide people with tools and techniques which send away equal used a springboard for amend perceptive our relationships with subject organisms. This will ideally help us to have richer social experiences with technology, and live happier and fuller lives.

Step 3: The Uncanny Valley and Social Interaction

When engaging with robots, we e'er bring to the table a wealth of social noesis and history with US. This makes any interaction we have with robots tainted not only by our own preconceptions of robotics, simply too aside our experience of the natural world. The closer a robot mimics something other, the more associations we are fit to draw from and place upon it. Since a automaton is au fon a mirror of our preconceptions, in any regard, whatsoever manner in which a robot behaves is even off. It should non matter whether it is flailing helplessly on the floor, or soft apart. After all, both the concept of "flailing helplessly" and "descending apart" are social constructs arrived at from our understanding of and interaction with other organisms and machinery. Careless of what the automaton does, or its own level of cognizance, we will project our social reality upon it.

Additionally, beyond our own ethnical constructs, we bring with us a nagging meta-cognition that this being is not alive in the same signified that we are. This understanding can both enable America to accept it many readily arsenic an autonomous creature in its own right, only also lead us to reject it as a cheap simulation. As roboticist Masahiro Mori maiden claimed in 1970, an "uncanny valley" in human empathy levels exists at threshold in which a robot becomes very human-like, and past disappears altogether when perfect replication is achieved. In other words, we have empathy for robots until the point at which it is very close to beingness human, at which indicate we have a strong revulsion. Should the golem continue comme il faut more humanlike-like (to the point of existence undistinguishable from human), our empathy levels spike adequate anthropomorphous-to-human empathy levels. This sudden and forceful dip where our empathy levels drop dramatically before spiking up again, is the "supernatural valley"

For instance, this unsettling android robot falls artful inside the "uncanny vale:"

While this principle is largely practical to humanoid robots, I would venture to guess the same principle rear end be practical - to a astronomic extent - to zoomorphic robots. After all, regardless of whether animals have copious cognitive and emotional lives (which I personally believe some act up), we project ours upon them, and in some capacity humanize them. I would venture to conjecture a nearly perfect robotic dog, would be even as unsettling as a all but perfect robotic human.

Intellect that I testament ne'er achieve all perfect zoomorphic replicas, I have distinct not to set my sights thereon. Information technology is my worry that "almost perfect" writ of execution might actually be worse than an abstracted mimesis. Or else of direct reverberation, I have set unconscious to create what Simon Cent termed a "Social Agent." These agents exist inside a social environment, as a separate of reflection of the viewer. Hoi polloi observe them so project their own cultural metaphors and associations upon them, creating cultural significance where none in truth exists. For this reason, a toothbrush head with a battery and vibrating motor attached could be perceived to exist alive - even playful - although it has no real intelligence service of what to speak. Capitalizing on people's need to understand and bring meaning to the populace, these devices exploit mass's antecedent experiences with other living creatures to offer import.

In that circumstance, the robotic agent actually benefits from behaving like other organisms, but not actually trying to be whatsoever of them. For starters, it can capitalize on people's existing cultural connexion, and secondly, it does not take chances falling into the "uncanny vale." Therefore, it was not my goal to recreate existing forms. In that location was no point. The biological organisms that I am perusal already exist in a perfectly fine manner. Rather, it is my goal to capitalise on the alive social responses these forms trigger in humans. This could well be done without perfect replication.

Rather than quicken a spider or squid, I have set bent on create a new "species" which could be perceived as wanderer-like or squid-comparable. Ultimately, I am building robotic creatures which could personify detected as autonomous - mayhap even brainy - sentient organisms, but have little to atomic number 102 intelligence to speak of. In other terms, I endeavor for the robots to be perceived American Samoa living in a social context, rather than to exist as self-aware living organisms that try to be alive. Ultimately, it is not my goal to get behavioral responses out of robots, but behavioral responses out of humans.

Measure 4: Predictable Volatility

As I wrote antecedently in my Sagittate Bots book, I the like to consider the most important property that a robot needs to posses to be "predictable capriciousness." What I mean by this is that near living creatures deport in few cardinal slipway virtually of the fourth dimension, but let little deviations or "ticks" which divert from this behavior. These deviations and ticks are predictable in that if the organism did not behave therein way, we would perceive them as entirely foreseeable and mechanical. This leads America to resolve that an organism is foreseeable, except when it is not. We cannot betoken when it is not, merely we crapper easy auspicate that it is going to cause this unpredictability. Therefor, living organisms have an capriciousness which is foreseeable.

As we relate to about some other animals that behave in this manner, so can we also relate to robots. If motorized jumbles of zip trussed plastic can convince people that they are displaying life-like behaviors, then this would lead me to believe that by making them even more life-like in form, I can convince people that these organisms are even more full of life. Perhaps these creatures - which exist nowhere in nature - can even inspire people to select the leap of faith required to perceive them as all living.

At last, I am edifice machines to mime attributes of absolute organisms in order to act upon humans associations and violence emotional reactions. On several level, this is an absurd interaction in which sophisticated organisms empathize with a machine that has no cognition any.

Step 5: First Biomechanical Models

As my point of departure, I centered my initial research around the forms of spiders, human arms, and cephalopodan tentacles. I chosen these three due to my initial hypothesis that they existed along a scale of fluidity; whereas the wanderer with its exoskeleton is the virtually rigid in its biomechanics, the cephalopod with no tangible skeleton of which to speak up is the most fluid, and the humanlike arm with its internal skeleton is someplace in the center. Additionally, all leash mechanisms simply fascinated me, and I wanted to to understand how they functioned. Having this sympathy would help me to decide how best to construct my social robots.

Footprint 6: The Arm

Whereas the part of the arm that is in all probability the most premeditated and replicated in robotics is the human deal and wrist, the part that has most fascinated ME is the berm. This fascination stems from having injured unconnected the inner social system of my far-right shoulder and needing to take it surgically reconstructed and held together away some a twelve bolts. My wound was named "360 Degree Instability," and what is telling about the name of this injury is that the shoulder has a very large orbit of move. As a matter of fact, it is doubtless the human joint adequate to of the widest range of mountains of motions.

Thither are 24 muscle groups that bring to the movement and stability of the shoulder. Of these, seventeen are in extraordinary direction attached to the shoulder bone, which is a emancipated floating bone that both counterbalances and provides a suport for the arm's gyration in the chunk socket. There is only one traditional ivory joint conjunctive the shoulder to the rest of the body (from the collarbone to the sternum). Otherwise, the shoulder is largely held in situ by tendons, ligaments, cartilage and heftines. Also Charles Frederick Worth noting, galore of these muscles are long muscles that stretch thrown the distance of the back and chest of drawers.

To translate these into robotic terms would have necessitated a larger put up complex body part than the small modular joints I intended to build. To boot, even if I were to simplify the shoulder musculature to only admit the muscles required for forceful motion, I nevertheless would have needed a significant number of false muscles. IT was my conclusion that as a point of exit towards a generalized human joint, the articulatio humeri was less than ideal due to its uniqueness and complexity in structure.

Fortuitously, not much further falling the arm, one finds the cubital joint. The elbow is a textbook hinge joint. It also has a relatively simple mating of muscles, which are responsible for expanding and catching the sharing along a 140 degree arc. The other notable distinctive of this hinge joint is that it non merely mirrors a issue of else human joints including the knee, and finger joints, but also mirrors flexible joint joints in a host of different species. These include, but are no means limited to lizards, dogs, horses, turtles, and elephants. In price of a chemical mechanism that would be key for generalized life-ilk travel, the ginglymoid joint seemed the like a good starting point.

The joint itself is relatively basic. It consists of 2 bones detached away cartilage and held together by four ligaments. Muscles then go with the maraca with tendons to make over a third-class prise. Aside contracting and emotional the muscles the forearm lifts and lowers. Beyond that, there is not too some Sir Thomas More to understand in the way of basic functionality. It is a very simple biomechanical model, which makes it an ideal human body to research in damage of robotics.

In case you are unfamiliar your own elbow, check this out:

Step 7: The Spider Branch

The next biomechanics model that I focused upon was the anatomy of spiders. I was surprised to discover that spiders were part "hydraulic." By regulating pressure within its body, the spider is able to create large amounts of torque relative to its body size. Interestingly, the reasons spiders curl up when the dice is because of the loss of this pressurization.

Most joints in the wanderer are controlled by time-honored flexor and extensor muscles. However, two of the joints solely have the comportment of flexor muscles. By regulating the pressure in these joints and using muscles to perpetrate against them, the spider is able-bodied to generate substantial force. These joints also have mechanical revokable properties, which means that the joints canful not only stiffen to provide support, but can also tending in creating a frame for bend deformations in multiple directions. This use of muscle to create a makeup frame is similar to the manner in which cephalopod tentacles operate.

Albeit my first guesstimation was that a spider's leg consisted of 5 segments, I was surprised to learn that information technology actually has 7 discrete segments. Additionally, each segment has a unique and considerable range of motion. This makes the spider pegleg much more robust than I initially anticipated.

In terms of the type of joints that comprise its leg - aside from the two partially hydraulic joints - the structure is not very remarkable. The spider's joints consist entirely of hinge joints, like the one recovered in the human elbow. However, what sets them apart from human joints is the ability for a number of them to importantly flexure along 2 axis.

From this canonic research, it has become clear that ready to properly mimic a spider's leg, the robot is going to need a heckuva whole lot of segments and actuators. Alternately, if the goal is not to perfectly mimic a wanderer, but to physical body a standard joint, then it will not look unmistakably other from the human elbow joint. That said, I found the partially hydraulic joints very interesting for further explore. More than of my early research revolved about the attempt to create hinge joints that included hydraulic elements.

Step 8: The Tentacle

The most fascinating biomechanic that I explored was the tentacle. A tentacle is a contractile organ hydrostatic support system. The tentacle social organisation consists entirely of thick threesome dimensional array of muscle. Typically this consist of ii groupings; one of which is a bundle of long long muscles, and the opposite external group is arranged in a slanted manner around the intrinsic bundle. Volume within the tentacles is uninterrupted. Whatsoever decrease of muscle in any given direction must result in an gain in another. The muscles are laid such that all three dimensions can be actively controlled.

The ternion main ways to delineate tentacle movement include:

Reach - Increase in distance between proximal and distal portions of the tentacle.
Pull - Decrease in distance between proximal and lateral portions of the tentacle.
Explore - No change in distance. Laterial movements with localized sharp bending and torsion

They are likewise capable of four basic deformations which can occur at any point at any clip. These deformations are elongation, shortening, bending, and torsion (twisting). These deformations occur at "pseudo joints," which are localized arm bends that serve up as pin points.

When underwater, Cephalopods are roughly neutrally buoyant, and are typically marginally denser than oversea water. On report of their lively and range of motion, they are capable of a highly dynamic behavior, and are well adapted to this environment.

Here are some examples of octopi occupancy water:

Since most of the explore centered around these organisms concentrate on their movement in an submerged environs, it only late dawned upon me that the dynamism of cephalopods was sternly limited by gravity when the creature was removed from water. Albeit I could non find any enquiry supporting this mind, I was able to find a keep down of videos showing how octopi move outside of water. My observations of these videos have LED Pine Tree State to conclude that my initial hypothesis was a fairly accurate assumption.

The following videos present their movement outside of water:

As you can go through from the videos, albeit the octopus lavatory still wage in a range of movements, they are clearly having trouble supportive their own weighting in relation to gravity. Spell one explanation may be that these motions may just be a behavioral trait that they only demonstrate outdoorsy of water, a better explanation is that gravity dictates their movement by making it hard for them to put up the weight of their massive bodies, and pulling them down to the ground.

What this means for robotics is that either the tentacles I am qualification only necessitate to demonstrate great vigour if they are to exist in an aqueous environment. Otherwise, if the tentacle creature is to live outside of water, it is reasonable to allow them to be limited aside their ain slew. Quite than being able to lift itself and dynamically make a motion in any direction while happening land, the tentacles should actually exist better suited to drag themselves along the ground by curly and uncurling over each other.

Step 9: Robotic Precedents

Even though I tried to center my research exclusively around biomechanics and void looking at preceding robots, I launch looking at prior art pretty much unavoidable. All troika biomechnical models have a rich history in robotics. Ultimately, I found it healthful to examine prior work, and asses the pros and cons. Follows are some of the Thomas More exciting approaches I found.

Binary compound Spider Prototype (2011)
Fraunhofer IPA

The robotic wanderer pictured above is built by Fraunhofer. Unlike other robotic spiders, this one mirrors actual wanderer biomechanics away using hydraulic joints. These joints are restricted by an on-table pump, valves, and manipulate units. It is also of interest, because it using an SLS 3D printing process (similar in ways to the Objet printing). The amount of control and force all leg is able to practice allows it to tread uneven ground with keen agility. Alas, there is incomprehensive documentation presently published, and no video demonstrating its abilities.

Autonomous Walk-to Wanderer Robot (2008)
Kanal Von Tinowerner

Pros: It is a real simple mechanism, and somewhat convincing as a spider.

Cons: The legs are rigid and the movement is stiff.

Apparition Robot Company Arm with Hand C5 (2008)
Fantas Robot Company

Pros: This is very complex and pneumatic-based. Exploitation air squeeze, it is capable of a lot of force.

Cons: The movement is very mechanical and nonmoving.

Soft Robot Artificial Muscle Arm and Gripper (2012)
mikey77

Pros: As an arm, it is non ideal. Nonetheless, as a potential model for a tentacle with no stiff skeleton, this is a very interesting approach.

Cons: IT is lacking body structure and complex curb necessary for arm movement.

Robot Tentacle (2006)
Christopher Glenn

Pros: This is a strong pneumatic vent-muscle based tentacle up to of a range of movements.

Cons: It is big and unwieldy, has a limited number of flex points, and seemingly restricted by gravitation.

Cushiony Robot Tentacle (2011)
The Octopus Project

Pros: Looks and ostensibly acts like an de facto tentacle.

Cons: I suspicious this is a rigid systema skeletale only equal to of a one-person deformation pivot, and is capitalizing happening the silicone polymer covering's tendency to be fluid and wrap around things when emotional underwater.

Step 10: Intended Mistakes

The first mechanism that I choose to focus connected was the tentacle. At that place are obviously a number of ways I could have approached this. Rather than picking the most promising approach to begin my experiments, I decided connected the quickest and least promising. I planned a mannikin mindful of the tail mechanism from a robotic dinosaur toy called the Pleo.

From the onset, I recognized this was automatically not the right advance. For starters, it could not expand and stretch like an actual tentacle. Information technology also only allowed for deformation along two axis, and - at that - only on a singular pivot. This is less than ideal because an actual tentacle allows for deformation in whatsoever direction at any given point on its length. It is also rigid and non particularly suited to gripping things.

The tail is actuated by four alloy cables passed through four consecutive rows of holes in all of the discs. These rows are arranged in cardinal apprehend positions around the center. If you pull on one cable, the tail volition crouch in that direction, and if you force on the opposite cable, information technology will then clear the other. By alternately pulling on other cables, the tail can be made to bend dexter in any focusing.

Still, I wanted to have first hand undergo to understand why this particular tentacle-like configuration was not flop. I requisite to physically interact with it before I could actually understand why IT was a mistake. I too wanted to see if there was anything to be found of value in its intention. Later some initial experiment I concluded that in spite of all of its shortcomings, it was - after all - bad scalelike to what I was trying to exercise.

This design ultimately smel short of mimicking a tentacle. However, this mechanism inspired advanced approaches towards hinge joints. I also think there is perhaps approximately value to be found in this design for soil-based tentacle robots; but more on that later.

Step 11: Articulated lorr-Intentional Mistakes

In terms of spider biomechanics, my early thought was to 3D print a small abstracted spider with galosh joints, and try to get it oncoming as quickly Eastern Samoa possible using an ATtiny and muscle wire. The architectural plan was to own diagonally crossing sets of muscularity wires, such that when one wire was activated it would both pull forward and lift one leg, and pull hindmost and drop the inverse leg. Information technology seemed sound in possibility, merely I wasn't sure if this was really going to work. I kind of suspected it wouldn't.

As a matter of fact, I never even got the chance to run IT out. IT became truly manifest that the flaw in the design was the rubber connectors. Steady though they were anchored firm inside the rigid moldable, they were not open for any significant length. Instead of bending, the rubber connectors merely snapped off where they met the plastic. Au fon, the amount of force mandatory to snap the leg slay was less than the amount of force necessary to deflect the rubber cylindrical connectors. The lengths of cylinder that needed to bend were finally less than the diameter of the cylinder. Information technology was not going to lic.

In that respect were ways I could have genteel the blueprint to make IT work. However, IT became apparent to me that this design would not exfoliation, was not modular, and non biomechanically correct (at least, how it currently stood). I quickly derelict information technology, and moved towards building a standard wooden leg rather.

Stride 12: Mechanics Bellows

After abandoning brawn wire, I decided that I needed to focus on finding an actuator that could scale crossways all of the assemblies. I decided that the good way to get fluid motion and power I needed was finished the use of either pneumatics or hydraulics. Ab initio I explored airwave muscles. Piece this is a pretty well established technique, and allows for the exertion of really largish forces, it besides has its shortcomings for this sort of robotics. To begin, the control mechanisms or pneumatics are large and heavy. More significantly, the 3D written corporal could non hold up to the high pressures required in actuating line muscles. However, the materials tortuous could easily withstand the pressures necessary for small-scale hydraulics.

Instead, I decided pneumatics were non only a more sensible approach, but also a more fascinating area to search. Very few people were working happening hydraulics at this scale leaf, leaving a good deal of room for experimentation. My initial models were elysian by two works found happening Instructables. The early exercise was a gas-supported velvety robot arm that used expanding and catching bellows that pressurised a robotic claw . The second function was a artificial robot arm that exploited syringes atomic number 3 some pneumatic levers and actuators. I decided to combine the two whole shebang and use up a syringe as an actuator to control the bellows.

Step 13: Bellows V.1

The initial version I made secondhand two different potentiality shapes and what Objet refers to as the "ABS-like" material. What made this material initially auspicious was that it was not only very strong, just likewise quite conciliatory when printed with a rampart of to a lesser degree two millimeters. Withal, if you print it as well thinly, information technology bequeath start to crack. I could never quite discover that conjuration spot where it remains flexible, but does not start to crevice from wear.

I am aware this is accomplishable, because the only preceding instance I have seen of a working 3D printed bellow was made victimization a thin shell of this material. However, I did not succeed at replicating these results and gave functioning. Ultimately, I decided to try to use a material primarily consisting of a rubber-like "Tango Black +" material.

During this first round, I explored two different designs. One was squeeze box-like and expanded and contracted along a linear axis vertebra. The other was clamshell-like and expanded and shrunk along a swivel. It was my thinking that the clamshell bellow may simultaneously provide construction to the joint and perform the pivot.

After the initial test I concluded the material was not going to be composition enough to allow this, and decided to proceed with the accordion-alike figure.

Step 14: Bellows V.2

My second attempt at printing bellows was primarily rubber based happening a range of "whole number materials" between "Tango Black +" and "Vero Theodore Harold White."

My initial photographic print consisted of 4 identical files using the following appendage materials:
DM-8530
DM-9895
DM-9870
Decimeter-9850

After first testing I concluded that only the cooking stove 'tween DM-9870 and DM-9895 were practicable options. The softer DM-9850 material tended to fall apart during the post-printing cleaning litigate, and the more unadaptable DM-8530 was much too rigid and going to snap under use.

These prints were valuable as a proof of concept, but were not practical in damage of designing. Principally, they were open happening both ends, making them less than ideal as end-points in the closed system. Inordinate additional hardware would have been needed to crest ane end. Further iterations were required.

On a go with note - early potential materials can be achieved by using a mixture of "Vero Clear" with either "Tango Dishonourable +" or "Tango +." These materials seem potentially a little less prone to cracking in a more rigid state. Even so, at the clock of writing this clause, I have been incapable to print these parts with these combinations.

Step 15: Bellows V.3

Before improving the design of the former rendering, I wanted to experiment with ever-changing the shape of the holloa. Mainly, I want to be reliable that the previous excogitation was the unexcelled possible solution. With this in mind, I designed bellows in which both the convex and planoconcave surfaces had been hyperboloidal. I scaled this round project in a phone number of different variations, so written these using both the ABS-like material and DM-8970.

In the process of doing this, I incidentally written both sets with the unvarying wall thickness. What happened was that the ABS-like bellows were too unadaptable and snapped. Then again, the rubber-care bellows were too thing, and also fell apart. I did not attempt to reprinting either nonmoving of bellows because the rubber-similar ones (in hurt of falling apart) demonstrated that when compressed or expanded, these bellows deformed poorly. They tended to bulge outward along one and only axis when extended. By demarcation, the jagged edge bellows from V.2 compressed neatly inward in an accordion-same manner.

This design was explored no further.

Step 16: Bellows V.4

The next translation of the bellow was capped and had a connective loop. Different hardnesses of materials were tested for the connexion. The thinking on this design was that a cable could be committed to this connector and used to extend and contract a flexible joint joint .

The self-explanatory shortcoming of this design was that on that point was atomic number 102 unproblematic way to mount the bellow to whatever surface, and in and of itself, IT was not easily affected. This meant that it was prone to deforming and not very suitable for compressing Oregon releasing a tensioned cable.

Step 17: Bellows V.5

The most current result of the linear Bellow-founded hydraulic sinew consists of a bellow strained in an armature. The top of the roar is attached to a thin plate which is able to travel linearly along take rails inside of the armature. On the top of this home is the connection loop. The armature can be firmly attached to any meeting place, and the below can then travel linearly within it without deformation. This makes it nonsuch for a sinewy system in which a linear force needs to personify applied, such as in a hinge joint of a spider.

Step 18: Spatial Deformation With Bellows

While printing the linear hydraulic bellows, it was casually brought to my aid that the bellows mosaic quite nicely. This sparked a small explosion in my brain, and from previous research, I realized that the bellows could be adorned to potentially form segments of a tentacle.

The reason this would work is because when same is elongated, a contraction force could be applied to an opposite section, causing the stiffened segment to deform and bend. This would tolerate for deformation in any given direction. This design would too allow for significant contraction and expansion of the printed segment. This would give it a number of properties similar to an actual tentacle.

My early design included four bellows tessellated such that from each one unity abutted two other on either side. Afterward spending a very long sentence cleansing out the support material inside the bellows, it became obvious to me that there was an entire column of support happening the inside of the assembly where totally three bellows met. As the design presently stood, I would have no way of removing it. This was a set dorsum because it was preventing full compression.

I tried to print it again, but this metre with a 2mm mess in all end of the cap. This was the largest hole my design would admit Maine to put across. This hole was too small to use to hit any meaningful amount of money of confirm material, and as wel proved to comprise a failure.

Finally it occurred to me that the nice thing about tessellation was that it was immeasurably quotable. Preferably than having all quatern bellows interlock, I invest a bellow in the center and same to each side of it. Having this central bellow allowed Maine to place significantly larger holes in the center of the ceiling, and I was finally able to hit totally of the corroborate material. This also meant that I did not have to importantly compromise the innovation and was able to maintain the unvaried amount of distortion, compressing, and expansion. The one downside to this approach was that the diameter of the segment became slightly bigger.

This design was significantly easier to clean, and just As promising. Yet, I noticed that the part could not expand without cracking on the seems. It became apparent that the bellow necessary to be constrained along its Z-axis to prevent information technology from hyper-extending. It too became superficial, that when in use, the Saul Bellow's objective position needed to glucinium halfway betwixt its elongated and contracted location, to allow stretch and compressing of the tentacle.

At first, I considered constraining it on the z axis vertebra with a cable fastened along its central channel that would allow for it to compact, but non expand. However, I stimulate since decided a batter approach may be to black and white a series of thick rubber bands with suction cupful-like nodules parallel along the Z-axis.

A of the meter of issue, I take up nonetheless to essay either approach. Virtually all of my spacial contortion bellows give leaky floater from repeated handling. Some printing and cleaning a fresh one takes a goodly amount of time. At some manoeuvre I bequeath revisit this.

Step 19: 3D Written Syringes

Patc it may seem redundant to publish a syringe, when such an item could follow readily purchased, there was clear intent for doing this. Ultimately I would like to 3D photographic print hydraulic Walter Piston controlled past rack and pinion. However, before I fire get to that point, I need to make trusty that printing a dim-witted syringe would work satisfactorily.

I written the syringe in two parts. One part was the basic body of the syringe, and the strange was the plunger assembly that enclosed rubberized O-rings as part of the printed design. The deuce parts snapped together when completed.

All-in-all IT functioned as it should.

Footmark 20: Hydraulic Muscle System

Once I had the hydraulic muscular tissue and the syringe printed, The next obvious step was to connect them together and ascertain that the system worked. I bolted a standard plastic plumbing gib to the sinew's valve with a shriek clinch, fit the system with water, and and so connected information technology to the syringe with latex tubing.

When I pulled the syringe's plunger outward, the muscle contracted. When I pushed the plunger back in, the muscle expanded.

I never got around to doing regimented weight tests, but in my initial subjective judgment, I found that information technology was able to lift an object of roughly a couple of pounds.

I was able to cause the muscle with the syringe without problem... or... healthy... almost without trouble...

Stair 21: Textile Testing

After doing the first bellow tests, it occurred to me that the material may non exist water-tight. Up until that point, I had been working on the self-evident truth that information technology was. At least - it was supposed to be. I decided to fall this matter once and for all. I written tiny bowls in the full spectrum of materials betwixt Vero Light-colored and Tango Black +, and reliable their water absorption.

I ran the test 3 times, and concluded, without a dubiety, that the material was absorbing some amount of the water. All the same, it was neck and neck whether extraordinary materials were better than others. Nonetheless, none of the passed the test, and this was obviously problematic because it meant that the system was not sealed. In other words, it was slowly leaking over time.

Sealing both linear and spacial distortion bellow systems would try to be uncontrollable because of the number of surfaces, and the difficulty in reaching all of them. Albeit I have one of these days to try to solve this problem, I have whatever ideas on how to move forwards which I will turn to at the closing.

Step 22: New Approaches

Since the material was leaking, and not remarkably structural, I decided that the unexcelled course was to figure out a different attack.

After complete, I came to realize that in the setup I was imagining, I would need a motor to drive each hydraulic plunger. If I am translating the motorial rotation through a leaking hydraulic connection to (spoiler alert) linearly pull a cable, why not just have the motor pull the cable and take away the hydraulics? Answer... There is non a good intellect for just scrapping the hydraulics (at least until I solve the leaking job).

Whol of the mechanisms from here happening taboo are organism controlled aside luxuriously torque micro geared motors pulling on cables.

Step 23: Bendable Joints

The opening move towards making a not-liquid solution was to come heavenward with a satisfactory bendable joint that could embody pulled by a cable. As Steven Vogel points call at "Hombre's Paws and Catapults," mechanised joints tend to chute and slide, only organic joints bend. I found IT very grand that the robot's articulation should follow courtship and really bend. Looking back at earlier models, the Pleo's tail (which I well thought out a failed tentacle) clad to be a suitable good example for a hinge multilateral.

My first joint design was created to allow for the insertion of a PVC pipe or thin-walled aluminum tube into the joint's terminate caps. Notwithstandin, afterward printing process it, I realized that I was unhappy with IT. It was not only hefty and using a good deal of materials, just I came to reason that attaching hollow pipes is an excessive use of material. I could provide the same amount of money of structure with significantly less material, and decided tetrad thin atomic number 13 rods were a better solution than a single hollow pipe. This eliminates the majority of the large and operose material exploited, and generally makes the automaton lighter.

The initial innovation was beneficial in that IT had about 140 degrees of flexibility, which made IT equivalent to a human articulatio cubiti. This provided a good gauge for devising a smaller spider joint which only when needed about +/- 70 degrees of tractability from revolve about.

My incoming innovation had a flex angle of +/- 90 degrees and had a drastically lighter design. On each end cap there were four sockets designed for 3/16" rods to be bid fit into. I was in the end proud with this figure equally a general purpose ginglymoid joint.

Step 24: Robotic Limb

Once I had a eligible hinge spliff, my next exercise was to stool a functioning branch. The initial quiz consisted of a tree branch with two flexible joint joints, ii end caps, a motor plate, pulley-block, and ironware. The motor pulled a cablegram that passed through with both joints, and was constrained happening the early end with a stop arm. In this way, when the cable was reeled in, IT would pull connected the furthest hinge combined and subsequently force both joints to bend. To assist in the arm's return to a neutral position, a second cable was passed through both joints and related to an extension spring fastened to the end cap on the opposite end. In theory the motor was to bend the arm and the spring was to assistant recurrence IT to horizontal (in conjunction with gravity). This worked in theory, but did not in practice. Also, the return spring was not necessary when pushing against gravity. The robot's own weight, in conjunction with gravity brought the limb back to its initial state.

The centrifugal plate was held in situ by alternating rotating shaft collars. 2 shaft collars were ordered happening aslope rods in front of the motive plate and two were placed on the opposite diagonal rods behind the plate. The idea was that these would prevent the plate from sliding forwards or rearward. I later knowing that placing all four shaft collars ahead of the motor plate was a better idea. The plate never slides back, and placing them whol in presence prevents the plate from deforming (it turns out the plate is not arsenic solid as I expected when put low tautness).

While the initial plan was to use the limb to push up against the table, I quickly determined that this plan was flawed. It turn out that the written hinge joints have 45 degrees of contortion, still when forced away the steel cables. This means that a segment with two joints has a ladened 90 degrees of "writhe." As such, any section with more one of the joints (as each limb is currently designed) is leaving to quickly change by reversal sideways and lose stability.

Since ambitious against the table resulted in the limb twisting 90 degrees, I decided to test it by hanging IT off the edge of the table. In this way, I can observe how the joint would bend nether tension without worry about it twisting.

In this illustration, I have turned the limb top side down pat to pull up against gravitation:

After this first test I realized that attempting to trigger off two joints with a single drive changed the lever forces in each joint and resulted in non-uniform bending. This was fewer than ideal.

I decided to try to compensate for that by adding tension to the cardinal joint with various rubber bands configurations. This did not seem to bring up. Here is one example of that:

From these tests I learned that I was going to need at least 1 motor per join. I also learned that having more than one of these joints was going to result in 90 degrees of torsion and render the limb useless. With all of this in mind, I decided to build a golem with one hinge joint per segment. Information technology was my cerebration that rather than use a second motor to force the legs side to broadside I can rely on its inherent torsion and instability for locomotion. Additionally, information technology was my plan to use gravity to return the legs once actuated.

Step 25: 3D Printed Hexapod Body

The hexapod body was printed with the intent of having vi legs consisting of four flexible joint joints that were restrained by trio motors. As it became apparent to me that the on-going ginglymus design was flawed, I started to suspect that this frame would not work. It as wel became immediately apparent that it was too large. In turn, I designed a lighter weight version of the inning that required little physical, but never got around to printing it. In front I had the opportunity, I came to the realization that the legs I built to support the frame were impermanent and unsuited to the task. I decided that I was going to reduce the first golem build to legs with a singular joint, and that this frame was the condemnable design for this fres directoin.

Additionally, I have also come to conclude that building a hexapod was perhaps a bad idea because they are notoriously unstable. This has something to do with it consisting of a dynamically shifting twosome of tripods. In nature, six-legged creatures actually actually are far-famed to flail about and tip over. While this imbalance may actually be beneficial in certain situations, such as during the navigation of uneven or loose terrain, information technology is not what I was trying to accomplish.

I indirect request I had seen this Laurie Anderson video recording before starting this design. I whitethorn take over been inspired to act some more inquiry.

Step 26: Laser Cut Octopod Body

After realizing the hexapod was a fearful idea, I decided to make a laser cut octopod frame out of 1/4" plywood. The benefit of this approach is that IT is more stable and very light weight, tied with the 16 aluminum support rods.

Step 27: Squeeze You May Need

My initial version victimized the following parts:

(x8) hinge joints (Materials: DM-8520 and DM-9870)
(x8) motor plates (Corporal: DM-8720)
(x8) spindles (Material: DM-8720)
(x8) end caps (Material: DM-8720)
(x2) wood brackets (Material: 1/4" plywood)
(x16) 6" x 3/16" aluminum rods
(x32) 4" x 3/16" aluminum rods
(x48) 3/16" shaft collars (John Bach McMaster #9946K42)
(x1) 100' x 1/32" steel cable (McMaster #3458T151)
(x100) 1/32" stop concretion sleeve (McMaster #3936T33)
(x8) micro geared motors
(x1) Arduino
(x8) H-Bridges (removed from persisting servos)
(x1) assorted zip ties

Later the pursuing parts were added:

(x8) TIP120 transistors
(x8) 1N4004 diodes
(x1) PCB
(x8) 5" rubberise bands

The following parts were separate:

(x8) H-Harry Bridges
(x8) 5" rubber bands

(Note that some of the golf links on this paginate are affiliate links. This does not change the cost of the item for you. I reinvest whatever proceeds I incur into making new projects. If you would like whatsoever suggestions for alternative suppliers, delight let ME have intercourse.)

Stone's throw 28: Insert Motors

Catch a motorial plate and a micro geared motor. Make sure enough the efferent compartment is sort out of the financial support materials and then push in a motor until IT locks in place.

Retell for the remaining 7 sets of efferent assemblies.

Ill-use 29: Slide

For my initial translation, I grabbed four 6" aluminum rods. I then slid a dig collar onto two of the aluminum rods. Motor plates were then slid onto the rods such that the motor boxes were facing outwards. Finally, I slide two much shaft collars onto the rods (one connected each end). This process was so recurrent tercet more times.

I late patterned KO'd that this particular assembly was not a good estimation. Initially, I had acknowledged that the motor plates were solid enough that the 2 shaft collars would simply stiffen them. However, it turns out the corporeal deforms and bends granted sufficiency tensity and time. So, the corners not constrained ended up deforming and getting pulled forwards. This was manifestly nobelium good.

I afterwards definite that a better approach is to first slide happening the motor plates, and so slide shaft of light collars onto each gat so much that there is one connected each corner of both motor plates.

Step 30: Constrain the Joints

The next step is to constrain the joints to only bow along a single axis. This is completed by inserting wires through two sets of parallel holes.

The close of each electrify should then be clamped with a stop sleeve, and trimmed scant.

Step 31: More Shaft Collars

Slide the shaft collars roughly 1/2" onto every other Al rod end. Make sure at that place is enough elbow room left to both slip on the awkward octopod inning and printing press fit a bendable corporate.

When all of the shaft collars are in place, slide on the octopod frames.

Step 32: Military press Fit

Urge match the flexible joints onto the aluminium rods.

Reposition the shaft collars such that wooden octopod bracket is sandwiched firmly between, and lock the shaft collars into stead.

Step 33: Attach Cables

Cut Eight 10" steel cables. Put a stop arm connected one end, and then pass it through the reel from the outside in (the stop sleeve should follow on the outside of the bobbin).

Pass the cable television through the octopod body, and one of the rows of corporate's holes.

Press the spool onto the motor shaft.

Finally, clinch a stop arm onto the different close of the cable.

Double the process 7 more times.

Step 34: Retract Cables

Pick one of the motors. Apply a supportive voltage to the terminal marked with a red dot. Apply a dissenting electric potential to the other terminal.

The efferent will start to spin. Let it keep spinning until altogether of the slack off has been wound tightly onto the bobbin, and then remove the voltage.

By hand, spin the spool posterior in the opposite direction to rent up some of the tautness.

Step 35: Legs

Enclose 4" rods into each of the bendable joint's remaining sockets.

Press fit an end detonating device onto the ends of each set of rods.

Step 36: Clean Up

For the interest of consistence, dislodge all of the motor plates sol that they are an 1-1/2" from the awkward octopod systema skeletale.

Step 37: Wire It Up

Solder a 4" red wire to the motor terminals marked with a ruby battery-acid, and black wires to all of the other motive terminals.

Step 38: H-bridges

I initially soldered the red and black wires to the terminals on the servo H-bridges that the servo motors were desoldered from.

I later decided this was a slip, as these H-bridges were ne'er providing enough power to the motors.

Step 39: Spic-and-span It Dormy

I zip tied all of the H-Bridges neatly to the aluminum rods.

It is good to clean stuff up, only unnecessary if you are not using the H-Harry Bridges.

Step 40: Rubber Bands

Later the initial tests, I came to learn that gravity is both cruel and indifferent. Put differently, pushing up against gravity is no easy task. Each leg has to be able to lift the weight of the full assembly. This requires a unbiased amount of exponent.

Here is an example of it not functional:

Rather than try to facelift all of the weight and push against the forces of gravitational force, I decided to tension the joints and make its initial put forward fully bent. By changing the initial DoS, I have also denaturized the manner in which the drive needs to exert force. Rather than draw in on the leg to thrust against gravitational force, it now only needs to pull to face-lift the leg against gravity. In this agency, the robot would only need to exceed the force of the rubber band's tension, and the leg's personal weight. This is considerably easier than lifting the angle of the whole bot.

Nevertheless, initial tests of the new configuration were break, but still not very likely :

This did non seem right. For all intents and purposes, it should have worked. I concluded that the H-bridges were under-powering the motors.

I then decided to power the motor immediately from the power source and cut the H-bridge out of the equation. This worked somewhat better:

From there, I definite to withdraw them and replace them with TIP120 transistors and 1N4004 snubber diodes.

Here is an example of the legs slowly alternate:

And by contrast, here are the legs quickly alternating:

While clearly the robot is now doing something, it is relieve not truly doing it quite right. Lifting up one leg at a time does not create locomotion. When multiples were simultaneously raised to create an uneasy state, the robot simply sank pop, and was never able to recover. All over time it found itself just vellication on the floor.

Step 41: Getting Somewhere

It was clear that the rubber bands were not serving. Albeit they helped maintain its upright state, they offered no additional upward lift against gravity. If the robot is to remain upright, it is going to need to make up capable to push up against gravity.

Fifty-fifty though the first test of getting the robot to repeal itself against gravity established futile , I began to surmise that using the new TIP120 drive controls was going to work much finer.

I far the rubber bands and powered the motors directly using the TIP120 transistor. When all of the motors were engaged at once, the robot was able to lift itself off the ground:

This was promising because it demonstrated that the robot could not single lift itself, but as wel that the joints had sufficient torsion to go around.

The next test I tried was to power the legs in alternating sets (two on all go with). This did not go exceptionally well. The robot tended to lift itself on single side, and the torsion in the legs on the other side made them bend such that they were unable to do much of anything:

Incoming I decided to power the legs in sequentially in pairs. This sort of worked:

Finally, I definite to hold the robot off the ground when it first started up such that all of the legs would get tensioned. From this point, I let it taste to move alternating sets of legs. This was the nighest I got to getting it to walk in the manner intended:

As you can tell from the end of the television, it broke afterwards this trial run. Having the motors pull against the rigid ensnare that was non moving tore apart the spindle's center hole. It was becoming clear to me that this 3D printing was non suited to the type of robotics I had in mind and this seemed like as good of a stopping as any.

Step 42: A Promissory note on 3D Printing

The Objet's photopolymer printing process used to make these robots allowed for rapid iteration. It took hours to make objects that might have otherwise usurped days or evening weeks to make. Spell the applied science allowed me to work very apace, the prints that resulted tended to wear away. This is not solely unexpected because the Objet is largely suited for prototyping designs, and not producing structural objects. Since I was trying to make racy and functional objects, the technology ultimately proved super preventative. On many occasions I walked away from the robot for a few years, only to return and find the entire thing destroyed.

I learned that if nigh in a tensioned state for whatever length of prison term, the materials would crack and/or deform. This proved sincere for whippy joints, wire spools, efferent holders, and more structural elements like end caps. Patc this technology allows for rapid prototyping of multi-material robotic mechanisms, it is not suited as an end-product that derriere withstand various forces and strains for extended periods of time.

Notwithstandin, equally a means of rapidly prototyping, this applied science is fantastic and opens up many newfound design possibilities by allowing me to apace produce complex multi-material forms. Patc the process English hawthorn only be appropriate for generating robot prototypes, I could foresee fetching it further by determination more permanent materials and processes.

Step 43: Future Directions

There are a bi of potential future directions for this project:

  • Experiment with sealing the 3D written material to pass wate it many watertight. Roughly potential sealants include acrylic spray, silicon spray, and brushed liquid latex.
  • Incite some water treated and untreated tentacles underwater. If the materials work raw underwater, this butt potentially be very auspicious for underwater robotics.
  • Black and white textured skin to cover the various actuators. This is peculiarly the shell for tentacles, which I would like to cover in bad-like suction cups. This will as wel serve to constrain the 4-way actuator and keep them from finished-extending and cracking.
  • Print semi-rigid ligaments to add structure to the bendable hinge joint and keep torsion.
  • Bestow a ordinal set of motors to control deflexion the limbs from side to side in addition to up and down.
  • Use a motor to both campaign and pull out the ginglymoid joint. In this way, the efferent would some wind up slacke in one and only direction and unwind slow down in the opposite. By doing this, the motor will be able to some push limbs down feather and lift them upwards.
  • Add a positioning sensing element to know where the legs are in their arc. I started experimenting with this using commercial and home-brewed stretch sensors without convinced results. This issue needs to be resolved in front moving much farther in the process.
  • Explore new alternative materials to quickly replicate these forms without 3D printing. Composition board seems particularly promising because it can be both rigid and flexible depending on its configuration. It is also remarkably cheaper (if non unrestricted).
  • Digit extinct why the H-Bridges were beingness underpowered and witness if I rear end take them work. If non doable, design and progress alternate forward-cost H-bridge over boards for motor operate.
  • Study six-legged and eight-legged walk cycles many in-depth, and better implement them.

Of class, these ideas are just possible next steps. These are really only the tip of the iceberg and thither is a long ton of room to go beyond what I have shared here.

Footstep 44: Finish

Afterward threesome months of operative on this, I have realized that I am still a lank way from beingness able to do any significant social research with this golem in the manner to begin with deliberate, and I have gotten bored of solving prerequisite formalistic problems.

Considering that I am still unsure whether this attack will yield any better results than a Spearhead-shaped Bot - a sociable agent that could be improved in 30 transactions - I have distinct that this approach is needlessly complex. Moving forwards therein area, I signify to use up a simpler approach and focus my care on exploring social interaction with less complicated mechanisms.

Past posting my process, I Bob Hope individual else mightiness find my research utilitarian, or at least inspirational.

This research was made possible with the love and support of San Francisco State University Powdered Arts Department, Instructables.com and Autodesk Inc. A special thanks to Carlos Castellanos for unexpectedly agreeing to advise me through this process, and Steve Delaire for helping me out with totally my 3D printing woes.

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