1 m hexapod (autonomous insect)

Quote:

In order to suppress unwanted rapid servo motions during EZ-B initialising, a switchable power distributor was added for each side (servos 1.1 through 3.3 and servos 4.1 through 6.3, respectively).

And a great build too, are you located in Germany?

Yepp, close to Munich.

Wow that's so simple and elegant hexapod. I really like it! Look forward to seeing him wandering through your garden

Oh wow that is going to be such a great bot to see for sure! Reminds me of the Stargate Replicator, will follow this closely. Be careful to keep a close  watch if outside. I once made a robot that would turn on every 30 minutes to move explore,take a photo so I could leave it all night in this old abandoned house. Owner said paranormal stuff going on possibly. Of course when I went back ,beer bottles all over, seems only thing paranormal was teenagers breaking in to party and steel my robot camera.xD

I am from northern Germany!!

I think the empty spot on the head is a perfect location for a guinea pig command chair.

Haha i pictured far too vividly after I read your post. But he had a little helmet on and was holding a staff for some reason. King of the guinea pig revolution

Nice build, love the design, elegant and simple.  The sensor deck is a good idea, that fellow can get in a lot of trouble so have some insight into his surroundings will be helpful.

Your living the dream we all have when we retire, just sit around and build robots.

Good news,

the insect learned walking !

I will need to provide it with a set of software versions, since in grass it needs to lift up its feet more than walking on concrete.

By the end of the week I will have generated a short movie, publish it on Youtube and distribute the corresponding link.

Cheers

Volker

VIDEO !

Hi guys,

here the promised first steps of the large insect:

I have to apologise for the low video quality; still struggling with a new version of my video S/W and had to use a quite old version to get the video off the shelf.

Nevertheless, this thing is able to crawl and turn around.

It is fully understood that leg motions need to be optimised.

For the rest: See the video !

Oh my God, you are too close to it! Run away from the Replicator before it eats your face!xD

Nice work, put a cover on it, paint it silver then film it on a rocky terrain. Send the video to Elon Musk and tell him it is a prototype for the new Mars explorer and you need 100M in funding to complete the project.

Nink,

in fact I am not going to use it as an "artificial insect" anymore; this hexaod is now going to serve another application.

Reason: As physicist, phd I was working in the space industry for 30+ years and my last activity was a Mars mission study for our national space agency DLR-RFM about a swarm of autonomously operating platforms (to be launched within an international effort in the 2040ies or so).

Now, being retired, I am about building all these swarm members by my own on a small scale, just to see and learn how far one can get in realising such an ensemble by limited own funding.

The current hexapod is going to act as the crawler within such a swarm.

Goal: Terrestrial test campaigns in 2022 (details see below). -   Low and high flying relay stations. -   UAV (aerial reconnaissance) will generate images of potentially interesting spots (Points of Interest --> PoI) on the ground (later on Mars: spots with humid soil (search for life). -   UAV will transmit PoI coordinates to the swarm ground members (rover, humanoid and crawler). -   These units will drive to these PoI (humanoids and crawlers pickyback on a rover). -   On site, these units will perform a detailed optical PoI analysis.

Swarm members:

"Lander"; a central station, represented by a Panasonic CF-D1 Toughbook. Status: Existing.

Rover (currently in the design phase). Status: To be finished in Winter 2021 / 2022.

High flying relay platform as substitude for a satellite (new version of a solar powered RC model); I built this one in the 1990ies; now on permanent display in the National Aerospace Museum Oberschleissheim. Status: To be finished in March 2021.

Low flying relay platform. Status: Existing.

UAV with autopilot, GPS waypoint navigation, cameras, real time video link, HUD, etc. Status: Existing.

During field campaigns in 2022 all these units shall perform realtime data exchange for simulating a small-scale Mars mission on Earth. Location: MFC Dillingen airfield.

I know, such a project is quite challenging, but extremely interesting and I will still learn a lot with my 69 years !

So, stay tuned

interesting stuff to come over the next months.

Nice collection

Nink,

sorry to say: They will work; not these conventional multicopters, but other designs.

The current NASA mission to Mars is actally carrying a small coaxial helicopter for short flights around the lander --> JPL Ingenuity.

This little device has extensively been tested inside thermal-vaccum chambers under real Mars conditions - and it hovered and flew reliably !

In fact, the density of the martian atmosphere is corresponding to some 27 km altitude on Earth; about 10 mbar. By far enough density for normal flying. One simply needs to fly fast, in order to create sufficient aerodynamic lift.

Lift = (air density/2) * speed ^2 * cl * wing area                                                  (cl = wing profile lift coefficient)

Speed for a fixed-wing UAV on Mars would be some 70 - 80 m/s.

During my study I had developed a complete aerodynamical simulator, proving these assumptions, including VTOL procedures.

I am in aerodynamics for decades now, including flying since 1973.

Wow - you're living the dream Building robots all day!

I went back and edited my post, I don't know if mars thinner atmosphere is offset by the lower gravitational force enough to fly a traditional earth drone  so I will trust your expertise.

Nink, you are sooo right !

I forgot to mention that gravity on Mars is helping by a factor of 3 ! !

By the way ... celestial objects with a more dense atmosphere are welcome targets for conventional multicopters.

NASA JPL is working on a copter for Saturn's moon Titan --> NASA JPL Dragonfly

A totally autonomous flying robot; a dream to come true ! !

@ DJ: Corrrrrrrrect; you as a man of business and myself as an independent gentleman.

Hi DJ,

is there any chance to reduce the EZ-B loudspeker volume ?

It is always screaming so loudly that it "successfully connected to the net".

Reduced volume would really be appreciated;

thanks in advance !

Are you referring to the ezrobot ezb v4 default voice acknowledgments? I don’t think the volume can be adjusted for default phrases. Maybe contact ezrobot, who is the manufacturer, and see if that’s something they’d consider as a feature upgrade in a new version.

I took the ez-b out of the developer kit doc and soldered on a power cable and fuse and external speaker. This way it uses less space and you can do what you want with the audio.

this may have voided my warranty though

Since my EZ-B is now semi-permanently fixed (double sticker), I will take it as it is.

Thanks anyhow and

have a COMFORTABLE and ENJOYABLE Christmas time - like imagined !!

Hi guys,

some news from my large insect / autonomous sensor platform.

In order to be able to get enough equipment on board, a second deck was added to the structure, mounted on top of the inner servo mounts:

Material: Aluminium-foam-aluminium sandwich (10 mm thick), since it needs to be lightweight AND sturdy. Current sensors: Three ultrasonics, covering about 180 in front of the vehicle. One common trigger pulse (from DIO0) is simultaneously activating the pings of all transmitters, while the three echoes are detectd independently (fed to ADC1 through ADC3). All cables are fed through a central hatch down to the EZ-B V4. The rear of this deck is still avaliable for further equipment.

Well, that it's for today ...

... next activities: Mechanical front sensors (whiskers or tentacles, respectively) plus the above mentioned remote control.

So long ...

... cheers

Volker

Sehr gut Volker. Why are you connecting the echo pins to adc ports? They should go to normal IO ports.

I am running out of IO ports . 18 of those are occupied by the servos, 1 by the common ultrasonics trigger and the rest (5) will be occupied by the upcoming remote control.

I hope that daisy-chaining with a second EZ-B will provide me more DIOs.

BUT: This has to work under BLOCKLY, since I am not using the standard Synthiam programming surface.

By the way: Do you know how daisy-chaning will work, since DIO addresses in BLOCKLY are limited from 0 through 23 and not higher.

I think that if you add another controller you get more ports. You just need to select it with controlcommand.

Thanks - I will try, once my second EZ-B has arrived.

Here a link to something really amazing (concerning handling with complex terrain) that I discovered a minute ago:

https://www.youtube.com/watch?v=MwHHErfX9hI&t=2s

This video is really worth ! !

This update allows using Blockly to use servos from multiple ezb's rather than just the first one: https://synthiam.com/Products/ARC/Releases/ARC-2021-01-05-00-Early-Access-20174

Hi DJ,

thanks very much for this hint; my programming world is now approaching infinity ! !

Awesome - excitement like that keeps me going

Not sure there is a lot of value in buying multiple EZ-B (Kind of expensive when you pay shipping etc) if you just adding ports a $4 ESP32 works well.  For your set up you could just use 3 or 4 ESPs and also the audio "I have successfully connected to your network" will magically go away as well.

That actually gets me thinking.  I wonder if you could make a fully redundant Highly Availabile robot.  With your design any servo  could fail and it could still limp along ok and if you had 2 controllers running the servo's and 2 running the sensors and monitoring each other so if one fails the other one takes over and 2 Lipo's and 2 banks of sensors and ...

I don't think there is a lot of people building highly available robots without a single point of failure. hmmm

It’s the wiring that sucks for using the arduino products. But the esp is so affordable. It took me a long time to get their tcp stack to work with arc. It’s got a bunch of problems natively .... but you get what you pay for

the ezb firmware for it works pretty good though. Check it here: https://synthiam.com/Support/Hardware/DOIT-Esp32-DevKit-v1

Looking at Klaatu build photos he puts separate header blocks for all his servos so I get the feeling wiring for him would be immaculate. (Where as I would have a hundred wires all the same colour, held together with solder and some duct tape)

Hi Nink,

if you have a closer look at my video (sorry for its miserable quality) you may see, that it actually can limp along (front left servo had wrong address at that day). This leg was only moving up and down; nothing more. It was marching quite good; just a remarkable drift to the left .

https://www.desmos.com/calculator/rpnk0wnpvj?lang=de

Just wanted to share this over here too...

Wow, that looks great, thanks Mickey ! !

Would be interesting to find out, whether it is also calculating servo force as a function of torque, arm length and angle.

During my work on the insect I found out that this can be quite critical, because load is distributed on just three feet during walking.

17 kp*cm torque (for my servos) sounds pretty good - in the beginning - but with some 20 cm effective arm length (vertical projection), only 0,85 kp are remaining. With three feet on the ground just 2,6 kp. The robot is now approaching this value: No weight reserves.

In a nutshell: Servos cannnot be too strong; is however is often limited by their price.

So true...there is a thread over here with the title "Servos For Robot Dog" you might want to suscribe to it. There are more and more available options for Brushless Motor Control, that might give you the amount of torgue and speed you are looking for!

If you would like to calculate the torque of any brushless motor, you can do so by calculating the torque constant from its KV value...

https://www.fxsolver.com/solve/

So my Tarot S 4108 should have a torque constant of 0.02512 Nm/A

Also you can calculate the revolutions per volt applied... The Tarot S 4108 has 380 rpm/volt or 39.79(rad/sec)/volt There is an online converter for this! https://lucidar.me/en/unit-converter/rad-per-second-to-revolution-per-minute/

I am using a 1:40 gearbox on top of that BLDC motor... So with the gearbox is working I will need to measure the amps the motor draws under load, but lets consider 2.5Amps... 0.029 * 2.5 = 0.0628Nm

By multiplying a gear ratio of 40, the ideal torque on the output is 0.0628*40 = 2.512Nm

This will give you a good starting point when choosing a motor which will be offering enough torque for your specific setup!

...I had asked in another thread this exact question, about your set up, torque etc, but all the answers are here! Good info!

Sweet...nice we are getting the BLDCs back to the table, more and more interesting options are popping up!!

POSSIBLY OF GENERAL INTEREST

Hi guys,

the remote for my hexapod has arrived today; a really well designed tool, indeed !

Background and need for this device: Preventing the hexapod from doing forbidden things while not in autonomous mode, e.g. crawling towards an obstacle despite its installed sensors.

The pack includes an eight-channel digital transmitter; nearly waterproof; at least fulfilling IP 64 plus a tiny quartz-stabilised receiver.

Tough case; ideal for outdoor use. Little white item at the bottom: Magnet for the internal solenoid ON / OFF switch. Little dark items on the lower right: Needles from our Christmas tree . Buttons need to be re-labled

Operating wavelength: 315 MHz (classical superhet receiver). Transmitter ON / OFF switch: Removable magnet plus solenoid switch inside housing. Transmitter power : 4 AA batteries (not included). Receiver power: Main 2S-lipo battery through a 5 volt regulator (L7805). Receiver antenna: Straight lambda/4 wire (26cm length). Receiver sensitivity: -112 dBm (very good value). Range: Up to 500 m (far enough for any robot). Price: Around 25 Euros (price may vary slightly).

Supply source (example): https://www.banggood.com/315MHz-8CH-Channel-Superheterodyne-Receiver-Module-with-Decoding-Output-Module-With-Remote-Control-Transmitter-p-1573292.html?cur_warehouse=CN&rmmds=search

Delivery time to Europe: About two weeks.

Next activities: Re-lableling of the buttons on the transmitter (STOP, FORWARD, BACKWARD, LEFT, RIGHT, RESUME). Functions of further channels: TBD Connection between receiver outputs (TTL level) and EZ-B and 2S-Lipo via 10-lead ribbon cable.

In a nutshell: A really useful item with a very friendly price tag.

I actually like that chinky stuff on the transmitter...makes it look pretty Cyberpunk!!

Hi guys,

just added a few audio text outputs to one of my test routines for acoustical support during sensor calibration.

Result was really astonishing: Using English text, my insect was speaking with a really bad German accent. In addition, numbers are called in German and not in English.

Sounds really terrible ; like a 5th grade (in maximum) ! !

What is the reason for this ? Is it caused by the region setting of my computer (where probably these acoustic data are being created) ?

Setting the PC completely to English makes no sense, since all other formats would be altered as well.

Question: Is there a chance to only set AUDIO output from a PC to a different language ?

I like to hear British English, despite the fact that the insect is residing in southern Germany .

Thanks a lot for any hint !

Cheers

Volker

Hexapod during a recent Yoga session:

Lots of options for speech synthesis. There are several text to speech solutions and there are also speech settings (male female) but you may want to poke around in the skills section to find a voice / language  you like. There is Bing text to speech and Watson as well as others.

Project -  add - audio

Hi guys,

the 1 m insect has received some major modifications:

(1) Previous power distributors incl. switches, fuses and sockets for the servos have been replaced by a kind of fuse banks, each equipped with an individual fuse for each servo.

Background: During a recent test, one of the servos ran into a hard stop (unnoticed). After a minute or so, Amperes were smelled, but it was too late, the servo was already dead (overheated electronics). The 2 common fuses (serving 9 servos per side) did not react, since their values had been defined to withstand currents for 9 servos under load and therefore could no protect a single unit in a hard stop. As a result a new concept with individual fuses.

New version (1 individual fuse per servo plus common switch) I am aware of this one missing fuse .

This concept (one unit per side) works very well and will surely save nerves (Fuses: Cheap and Servos: Expensive) !

(2) Work on the upper deck was also progressing as planned.

The receiver for the digital 8-channel remote control as well as the second EZ-B have been installed on the upper deck.

Upper deck with receiver of the remote control and the second EZ-B.    OK, cables still need to be arranged. Tentacles (here at the left) not attached; only their microswitches visible.

Latter unit will control all present and future sensors; avoiding signal lines running from the upper deck down to the lower deck (other EZ-B; now only responsible for the drive servos and some housekeeping stuff). Just a single power line is running from the upper deck down to the 2S2P5000 LiPo battery, making future disassembling and inspection much easier.

The insect is currently equipped with the following sensor suite: -    Three ultrasonics (middle deck), covering 180 of the front section. -    Two tentacles (upper deck), acting as final obstacle warning at zero distance. -    Camera (upper deck), function still t.b.d.   .

For future long range outdoor navigation (primarily for autonomous location of the battery charging station) an optical solution is currently under test.

Due to the fact that homing-in towards e.g. the charging station has to work during bright sunshine as well as during dusk or dawn.

Classic optical concepts, based on lamps or LEDs in the VIS or NIR spectral range will hardly work, sincethe SNR at the detector outputs will be too low, even when using extreme narrowband optical filters <-- damned expensive !

VIS = Visible section of the electromagnetic spectrum (380 nm to 750 nm).

NIR = Near infrared section of the electromagnetic spectrum (800 nm to 2500 nm).

A way out could be, using Mid-IR signals (wavelength about 10 m). This is the regime of thermal signatures.

Mid-IR = Middle infrared section of the electromagnetic spectrum (3 m to 50 m).

Important: Keep in mind that the sun is not emitting any thermal radiation or heat. Maximum intensity of solar radiation is at about 500 nm (green); therefore leaves, etc. are green for optimised plants’ metabolism !

Heat in sunlight is exclusively created on / in illuminated surfaces (conversion of solar radiation with short wavelength (VIS and NIR) into thermal radiation with longer wavelength (Mid-IR).

The following diagram (spectral intensities of sun light (VIS and NIR) and Mid-IR radiation) is illustration this effect:

The sun is about invisible in the Mid-IR !

As a matter of fact, garden environment in the Mid-IR is pretty dark, only the small warming effect of sunlight on leaves, grass or other objects may generate thermal signatures of lower intensity or contrast.

Principle of Mid-IR outdoor navigation: An object with a hot surface (about 100C), aka Black Body in the centre of the charging station is acting as an optical transmitter and heat sensitive detectors on the insect are delivering information for the navigation towards this station. Due to its high SNR relative to the environment, this thermally bright object will easily be detected by suitable sensors.

Realising such a hot surface is not a big deal. It was more interesting, whether suitable detectors were available.

Answer: YESSS ! !

PIR sensors, typically in use for activating the light at the entrance of a house are commonly available at low cost (small versions including electronics below 2 Euros).

Typical example: HC-SR501.

Dedicated subroutines in the main control software will transform their information into corresponding signals for the motion servos.

More details about this hopefully working - concept in the near future during / after outdoor tests.

Well, that’s it for today !

Cheers

Volker

Wow that is so neat to see progress on this! Specially the wave length filters. I’m excited to witness the succsss!

Hi DJ,

sorry to say, but there are no filters around.

It is just mother nature that cares for the separation of these spectral ranges (VIS + NIR vs. Mid-IR).

In fact it is one of the advantages of such an approach that no filters at all are required.

Hi guys,

the large insect is about receiving its heat-sensitive sensors for later locating the charging station for its battery, once strolling around in the garden.

A hot black body source (T appr. 100C) will be installed at this station (size of a flat iron) so that the hexapod will be able to home in from any point; just picking up the heading to this target and start following this thermal signal.

As mentioned in a previous contribution, HC-SR501 boards, comprising a small PIR sensor element, will be used. These are normally delivered with a wide-angle lens that needs to be removed for the current usage.

Six of these sensors mounted at the upper deck - are covering the complete 360 azimuth around the insect.

Unfortunately, operation of these PIR sensors is jointed with a major disadvantage: They only react on changes of thermal signatures, meaning that they are only generating a single HI output pulse if a warm object is entering or leaving their field of view (fov), respectively. Pulse duration is adjustable within a few seconds.

If such a warm object would quietly stay within their fov, no further HI pulses would be generated (no intrinsic re-triggering).

Required: Modulated thermal signal.

Potential solutions: -    Modulation of the warm transmitter (black body) itself is not possible due to its high thermal inertia. -    Modulation of the thermal signal at the receiver is quite easy: A small cardboard pendulum with a central aperture is mounted immediately in front of the sensor aperture.

Due to the hexapod’s rumbling motions, this pendulum will swing; periodically covering the sensor aperture.

By this neat mechanical device, the received black body’s thermal signal is amplitude-modulated: ON-OFF-ON-OFF-ON-OFF .., meaning that the HC-SR501 sensor is periodically re-triggered; thus generating a continuous HI signal as long as the black body will stay within its fov.

Basic requirement: Pendulum periodicity needs to be shorter than a single sensor HI pulse.

The following figure is illustrating the principle of this pendulum (here simulated by tilting the sensor housings):

Problem solved !

The little sensor units with their pendulums are mechanically sensitive and do require sturdy bodies (figure below). A white coat will ensure that their interior will stay cool (thermal sensors inside !), even during hexapod operation in bright sunlight.

In order to minimise payload mass, these bodies as well as the insect's mid deck and upper deck had been made from 10 mm sandwich foam plates (both sides covered with 0,2 mm aluminum.

Next steps need to concentrate on suitable Blockly software routines so that the hexapod will reliably pick up the heading towards the black body (charging station) to commence homing in towards the charging station.

So, that’s it for today

cheers

Volker

Wow!! I’m thoroughly impressed. Can’t wait to see it in action! Thanks for sharing the details. I find your build interesting

Hi DJ,

do you see a change that camera commands in Blockly could also be indexed ?

The "large insect" is currently undergoing a kind of "metamorphosis" towards an autonomous instrument carrier.

I am currently thinking about an onboard digging device in the rear for autonomous capturing of soil samples that had been identified as "interesting" by the front camera.

A second camera (mounted in the rear) would be very useful for monitoring these sampling activities.

Thanks for a brief comment !

Cheers

Volker

Hi DJ,

just installed ARC 2021.02.02.00 on another PC (Panasonic Toughbook) and noticed that an important BLOCKLY feature is missing:

The file managment line "Load Workspace      Save Worspace",

normally located between the lines "Create Variable" and "Camera Preview".

OS of this device is WIN10 Pro.

On my other PCs (desktops and laptops), everything is OK.

Any idea, why I cannot handle BLOCKLY files on that machine ?

Many thanks in advance !

Cheers

Volker

Ensure you're viewing the Blockly interface and here are the load and save workspace buttons..

Unless by chance you are viewing scripts of a robot skill, in which case there is no "workspace" in robot skills.. Robot skills may be imported using the Merge option which allows selecting skills from other projects to merge.

Hi,

of course I had selected the correct window; I am working with Blockly for many months now.

My fault: I had forgotten to add a figure, showing what I meant.

here is this Blockly window without load and save workspace buttons:

It seems that also the camera preview window in the lower left is not being loaded (compared with your example).

I will now remove ARC via Windows system tool and will re-install it; maybe this will help.

After ARC re-installation: 50 % success  -  this PC (Panasonic Toughbook) is operated by touchscreen and pen.

Hitting the potential location for one of the BLOCKLY save or load buttons with the pen, one of them will appear (see below).

A bit strange behaviour, but this is OK for me, since these functions are now available.

However, the section with the Camera Preview (normally immediately below these save and load buttons) is still missing

I dont have that problem. Must be that laptop of yours... Try other resolutions perhaps?

Have no problems with all my other desktops or laptops; it' s most probably related to this particular machine ...

... will dig deeper over the WE.

Now that is the strangest behavior I’ve seen. I cannot think of how that can even happen. There’s nothing different about those buttons and layout than any other buttons in arc.

It is a good idea to use a recent version of the ARC software. Difficult to diagnose with an older version.

make sure the tablet has the latest windows updates as well.

I use ARC 2021-02-02-00.

The Toughbook has a WIN 10 Pro version from summer 2020 (younger than all my other PCs).

But I will check for its WIN updates.

Same result upon installation of WIN updates.

Must be the machine itself.

No tragic, since these buttons can be brought to life via tipping the pen.

Hi guys,

here the latest and final images for the large hexapod (formally the "large insect"):

AND at least virtually ...

... it made it to Mars   !

Due to other projects that need to be finished within March, further field testing of the hexapod's autonomous  outdoor navigation, etc. have been shifted to early April.

Cheers

Volker

Hi DJ,

the hexapod is currently equipped with 2 (two) EZ-B.

How should the second one be connected to the PC ?

As client as the first one ?

The EZ-B manual is not covering operation of more than one unit.

I think you want this: https://synthiam.com/Support/Install/Multiple%20EZ-B%20over%20WiFi

Looks good at a first glance - THX !