RoboCut Us version
An automated, selfcharging lawnmover.
Welcome to see what you can get from this "amateur-fast-translation", OK.

mailing-list RoboCut/BASIC Stamp.

Whats BASIC Stamp, Check the startguide!
RoboCut FAQ,
RoboCut Presscenter. Higheresimages, Pressrelease etc.
RoboClean, Thoughts regarding autonomous cleaningbot

Feel free to mail me your queries! info@robotshop.nu

The article is written like an project diary, updated "in reverse" i.e. the most current news will be on top of the document. Schematics of circuitry will be added real soon now...
To Swedish version please!

2002-11-20 RoboCut 5 Experiences from the summer Our RC5 prototypes have been working hard during the season. We have now replaced the driver motors with a set of italian motors with gearbox, they are more compact and the design allow us to make the RC5 "box" design "closed". Theese motors have higher effect and can handle even more rough gardens with hills and slopes...on the other hand, powerconsumption increases and we'll lose an hour or so in "running-time" The cuttermotor is now a german "Dunker 42*25" which works very well, you can see the techspec down this page
RoboCut now has integrated electronics which gives the STAMP access to the accupack voltage. This means that RC5 can determine when a charging cycle is finished. A way of "semiautomated" charging we have been using is, plugging a DC-plug into the back of th RC when it's standing close to the BWF-cable, then let the software decide when charging is complete, and quite simply drive away and strectching tha cable and DC plug out of the RC, and start another 3-4 hour session of moving... Yeas, we have an early version of a "charging station, that the RC5 can find and "dock into", in the 3D-CAD system already, but right now focus is on getting the RC5-Kit available The BWF-transmitter has been improved and now contains electronics that makes it a RC5 charger as well. A simple constant current circuitry in combination with the charging techniques describe above works quite nice. The BWF-circuitry is based on a 555-timer, but the PCB is also prepared for a PIC-processor...By using a PIC instead of the 555 we can do nice tricks with the BWF and RC5...i mean really cool stuff and new ideas keeps popping up all the time ;-) The PCB in the front of the RC5 has all sensors and drivers "onboard" which makes assembly of the PCB into the RC5 very simpel. However, anyone who wants to use the PCB with selfmade mechanics can easily remove sensors, attach suitable cabling and mount the sensors where they like. Drive motors is now controlled by an drivercircuit from ALLEGRO, max 0.75 A per motor, cuttermotor is controlled by an MOS-FET solution. The PCB also has an prototyparea, right now there are 3 free I/O:s	exempel på "laddkurvor" som STAMPEN i RoboCut analyserar.
The accumulators is 10 very compact, and expensive, 1.2V 4.1 Ah NiMh cells, this forms a very compact powersource, giving us approx 3.5 hours of "normal daily moving" I have been quity "careless" with batteries ever since my parent encouraged me to experiment with lamps, motors, cables etc as a kid. "Don't connect to anything exept you batteries dear" they told me, and i caused only minor accidents and damage in our home and surroundings ;-) However, this was a long time ago, and when i had something of the same attitude with a fully charged 4.1 Ah 1.2 V cell, nature and fundamental "electricity laws" gave me a lesson. The little shortcut cell instantly got very hot and danced around my workshop floor with a scary Hzzzzz, while it "dressed off its shrink tubing clothes", finally i managed kicking it out through the door...a colleague made the same mistake with a 7.5 Ah cell... indoors...a the diningtable...he's still a little shaky...
Among other mistakes during the summer i can mention the colleague who finally got on speaking terms with his 7.5 Ah accupack, put the RC on charging in that same dining room, and took his doughter for a day-long shopping-tour. In Gothenburg, after two hours driving, he realized that his current software in the RC would start working automatically, as soon as the charging was finished, as described above on this page...fortunaltely, the RC had got trapped in its charging cables which "jammed" the cutter as well as the drive-wheel...puuuhhh. Right now the most frequent question is pricing, but we still cant supply you with this. Real soon now... While translating this, it's real close to the 24:th of december ( 24:th is the big day overe here, not the 25:th), so i would like to wish all our international web-guests a Very Merry Christmas and a Happy New Year Hans Forsberg MUX/robotshop.nu
Preview of the RoboCut 3 KIT!
Front and top view of the first prototypet! You see the IROD-modules and the IR-detector for navigating, protected by a film-container". The container is needed since the IR-detector is "drowning" in direct sun-light. Schematics PDF-file 3 pages 760Kb Now includes "radio-fence" Mechanical drawing / Wheelsl. (Download jpg-file and print from photoshop to get correct scaling
Schematics IR-Beaco (Now includes "radio-fence")
Experimenting with a small bot? Try the BOE-BOT We used experiences from this little BOT while building Robocut, besides, the included BS2 can be used in your own mover-projects. Also checkout the GrowBot GrowBot / BOE-BOT

30:e Augusti Long time, no hear! Well, i'm back. Been traveling for 7 weeks this summer, but, there has been some time to crawl around on the lawn too. As you can see on the image we have laser-cut a first version of the Robocut-Kit. RoboCut 3 BYGGSATS!.
Many of you ara asking for formulas to calculate resonance frequency for the detector coils. All coils has benefit of an parallel tuning capacitor. You will get a giant swing at the right freq. and the capacitor will cut-off a lot of noise and errors. Hard to type the formula on the web, this it what it looks like in an excel spreadsheet. Frekres. =1/((ROT(C1*L1))*2*3,14) C1 = kapacitansen L1 = coil "indctance". ROT the same as "Square-root" see what your excel calls it Often hard to determine the valu of an home made coil. We have good experiences from small PCB-coils with "iron-kernel". Then capacitors is only available in specific "series" so it can be rather tricky to find a match that ends up with 38.5 Khz. Of course you could adjust the frequency of the buried cable instead, but since we are using the 38,5 oscillator for the IR-beacon as well, we won't give up that easy.
I have found NiMh 1.2 V accus in the R20 size with 7 Ahours capacity, 8 months ago they where at 5 Ahours, well...thank you! With this amount of power onboard i will get about 6-7 hours working-time...who needs the charging station? Two ore thre loads a week and the work is done.	Typ: D Kapacitet: 7000 mAh Mått: 33,5x61,0 Vikt: 89g Standardladdning mAh / tid(h) / Max Volt 700/14/1,5 1 tim laddström: 7000 mA Nom. Spänning: 1,2V
Other experiences from this summer. Eg. an outgoing shaft at diam 3 mm on the cutter-motor is not enough. My cutter on the "dunker-motor" found a perfect hit on the leg of a "teak-gardenchair" and tchack, the shaft broke right off. Originally the shaft is 5mm which must be enough, but on my motor the shaft had been adjusted to fit some planetary-gear...
---------- Dont place the "buried cable" in down-hill/uo-hill position! "hills like this" can be tricky for the robot when the accus are running out, and the bot has'nt moved the distance your software "thinks" In worse case the bot "slips" over the cable and you are in trouble. Of course it should be possible to prevent ths in your software...well, now you know that you have to do it...do it! ------- Still hard to find driving motors at good value, we have killed several types already, the original "japan-servo" is still the best, but to expensive. Come on out there and gime me a tip! ------------
21: Mars We have run the RoboCut with a VideCamera and radiotransfer of sound and image to an indoor monitor, very cool. Now, we are going to remotecontrol the whole setup via an RF-link...Details herer

15: Februari Long time, no news...its been more theory than practice for a while during winter, however, lots of people out there are looking forward to the grass-season. Many questions are about the "cutter-motor" we are using. So far, we,v been using a "Dunker-motoren" GR 42*40, 12 Volt. Take a look at the tech spec (klick on image to se larger pics), and you have a "starting-point" for your searches and experiments. We'll be happy to hear about your experiences and tips. The DUNKER-motor is working fantastic with the sharp knives. Think it will work even with nylon-wire as cutter, but probably the ideal rpm for nylonwire is i little higher.

There is a smaller version of the DUNKER-motor, guess this will work as well "42x25", i'll guess this will work as well. I don't have any price on the motor, but...it has high finish and quality...expensive is a good guess. But, as i have said earlier, look at the specs, and you know what to searc for. Another "builder" has reported that he is using a simpler "johnson" motor, he has also designed a "cutter-disk" with a free rotating disk hanging under the cutter to protect the cutter and save energi if the cutter "duffs" inte the ground. On the otehr hand, another friend who is using a "readymade" mover with a similar arrangement, has had to remove the "frespinning plate" to get proper result...So...lets Keep It Simple Stupid......

27:e november Still working with prototype 2. (klick on image for larger view) The bodywork is vacuumformed lexan/ABS, and the framework is "water-cut" aluminum.
27:e november Wheelcenters...! This is an ide of making wheel-centers from standard device used as "stopper" on rotating shafts...image from a swedish catalogue, guess you can find something similar in your hardwarestore...
2:a oktober The lawnmover-season are over up here. Most "Briggs&Stratton users are happy, "Robot-Hasse" ...is not... Well, my fingers are still there, and i'm taking a deep breath. Now i have made an arrangement with 1.6 mm nylon-wire, instead of the sharp knives, no more danger...but protection glasses is still recommended if something flies away.This arrangement doesnt cut with the same elegance as the knives, and the ideal rpm should be a little higher, but it works.
2:a oktober Yet another experimental cutter-arrangement as you can see, i have modified an old 12-volt PC-fan. The idea is very interesting. Very low current, no noise, brushless--longlife, but, i'll think i'll need a bigger model You could easily find a fan in any "surplus-box" The one i've tried is of die-cast aluminium, PAPST 80*80
I'll think that 120*120 or 150*150 would be great. -Try it out, and let me know...
12:e september New cutter-motor...WOW! You have heard my coplaints about my "dustbuster, 6V motor" ...well, no more.I've found a german highquality motor, "DUNKER MOTOREN GR 42*40, 12 V This in combination with a new cutterdisk, made by my cool neighbour and friend Stig, gives a fantastic result. I can now cut a width of 20 cm, even thick grass is flying out like a tornado, there is no noise AND...over 2 hours of continous work.
But! Keep hands away, fallen apples are cut up in perfect, thin slices. Even thick sticks and parts of our raspberries are cut off...no mercy. The rpm of the cutterdisk is approx 4000.
.The cutterdisk has a diameter of 90 mm and with the current arrangement of knives the cutting-diameter is approx 195 mm. The blades are attached with M4 bolts, holes with tread in the cutter disk, and a "lock-bolt" on "backside" of the disk.
28:e augusti At last, a first proto-version of the buried wire fence is working People in the neighbourhood could ses a complete nerd, me, sitting in a dark, cold, swedish garden, eating popcorn, and watching four LED:s driving around
The technique for the Buried Wire Fence (BWF) is simple. The same signal is sent to both the IR-diode and the BWF. 38Khz with an on/off modulated serial message, at the moment, 12 V via an 22 ohm resistor.
As you can see, the two recieving-coils are extremely ugly, but a way to get a fairly known iductance, diam 10 cm, 100 turns, we will add an capacitor for resonane at 38 khz later.
"Radio-Fence" The system uses 38 khz as carrierfrequency, if you have followed this projectdiary you are now supposed to shout out "yahoooo!", Why ??? well...the the oscillator based on a 555-timer that powers th IR-beacon is using this frequency. So far, we have quite simply connected a long buried simple wire in serie with an resistor, konnected to the same signal as the iR-diode, serial message included...however, power is generated via an ULN-driver circuit. Maybe, we will increase the potential on the wire to increase "detecting range. The arrangement of today makes it possibel to detect from about 50 cm.
So...the transmitter is already build! (of course i was satisfied when i came up with this integrated solution ;-)). The reciever, one for left resp. right, took a little more work. Suddenly, we have to fight amalogue tech, and a "tradtionaly" difficult area...induce current, reonancefrequency, coils, inductance etc. But. since i have a masters degree, i had to dig into my brain and bookshelf....So, coil picks upp the elektro-magnetic field that is generated around the buried cable. Amplifi the induced potential, and give it a "sving " that kan be detected as on/off logic levels...This signal is connected to the STAMP and with a count or frequency count command will sort the signal out from other mor low-freq nois...Later on, even trying to detect the modulated serial message. Hope thata software in the STAMP helps me get rid of PLL-lock circuitry.		RoboCut in the autum darkness of Gothenburg. The Robocut works good even in the night, keep the noise low, and take care of the often wet grass during nights...which makes the "grass-cut" mor sticky...

29:e Augusti RoboCut on demo outside our little store. Welcome to our store to look at RoboCut, but kontakt us first, RoboCuit is only on display special days. Kjellbergsgatan 5

24:e Augusti Några frågor
Som vi sagt tidigare, har detta projekt väckt stor uppmärksamhet, många har börjat/planerar att bygga... Vi får många frågor, här är några. RoboCut FAQ

11:e augusti Now, a schematics for the IR-beacon. this is a design we are experimentng with for navigation to the charging station. There is also in image showing the design on an ordinary "vero-board" klick for high res images. RoboCut will navigate to its charging station with the help of an IR-Beacon. The IR-light forms a shape looking like the image.
By using several IR-diodes, and giving them individual "serial-messages", and then giving each diode a specific direction, we could help the RoboCut find it's way. By giving RoboCuts software routines that check for the IR-beacon even when it's NOT searching for the charger, and having theese routines "counting" the times it "sees" the charger in an array with variables for each IR-diode, you should be able to give RoboCut a weak idea about which parts of the lawn it has been covering... When a segment has got significally less coverage compared to the others, a routine could send the RoboCut in the desired direction ocassionally. By orienting RoboCut towards the IR-beacon, it could turn up in the "right way"....it's all in the CODEfolks...
This is RoboCut at the moment RoboCuts ovansidaClick the image for high res. The radio-fence !!! Still not solved...any tips regarding tech. frequencies, coils etc...Anyone who ownes a radio-fence for their dog. Theese seems very common in USA, most certainly forbidden here, the tech. is just what i need.

:8e Aug.
look at the schematics for the RoboCut

4:e Augusti
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During monday the 7:th of August, RoboCut i will be demonstrated in the store . Welcome to have a look. More demo:s and late-hour openings later on

3:e Augusti
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Now we have a plan for the charger electronics. Why not let the RoboCut on Board BS2 check the voltage over the NiMh cells, and also check the temp with eg a dallas 1620...Now RoboCut can charge on "all three parameters" voltage, temperature and time.

1:a Augusti
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Great with all the feedback from you readers. Now, i "dare" recommend a project like mine since it semms like the robot actually CAN move the lawn! Right now i't hard to tell which areas it can cope with but that of course has a lot to do with the cutter, the knives and the accumulators, parametrers which you can experiment with on your own. The Mechanics with the two big driving wheels and a thir small support is anyway a "bulls-eye" The whhels has an excellent grip and in manouvers great.

31:juli
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A very effective IR-beacon is now designed from a: BS2, a 555-timer, a Driver ULN2003 and two IR-diodes in serie. The IR-diodes are limited with a 27 ohm resistor at 9 Volts. The Beacon reaches my whole garden and with more diodes i guess i can create an circular array of IR-beams all over the garden, by using separate drivers from the ULN 2003 for each IR-diode i can give each "ir-beam" an individual message. Good for the RoboCut to find t correct way int to the station also a possibility to give RoboCut an idea about where it is, and maybe even help it plan its work slightly...

30:juli
------------ Last day of the holiday
From the images you can see that there has been some progress. Made a new chassies fron red plexi ! Has also started to "dress" the machine with skirts of foam-rubber. The skirts are supposed to protect from "flying parts, stones knives etc" Also intended to keep the noise level at a minimum, also, look at the rubber suspension ot the cutter-motor. There is also a IR-detector in the front-center. This detector is monted in a film cannister, this arrangement is necessary since the IR-sensor is "drowning" in the IR-light at direct sunlight.

.Just about to start experiment with the IR-beacon, self-charging and the Navigation. RoboCut is working surprisingly good, now i'll start to think that it can keep the lawn in shape..


------------- I's mowing and MOVING!
Yesterday, 25:e Juli i had RoboCut on the loose. The Cutter of designe described earlier. I was really cool to see the little maschine run away through pretty high grass. Grass was flying in all directions and the machine hade a nice, well-cut trace after it.

The cutter -motor is mounted in M5 bolts. At the "chassie" end i have created a simple rubber suspension with rubber details used cable-protection.

I have earlier talked about rpm-control of the cutter-motor and of course, such an arrangement would make it all even better. There is an module available with an separate PIC-processor controlling DC-motots very elegant, but i would of course be even cooler to manage getting the STAMP do the job...but that takes some very well written stamp-code, and the whole program has to be "timed" Another alternative would be to check the current through the motor an quite simple, stop the driving wheels for a short while when the current exceeds a specifik value, this way the cutter can work more carefully in thick grass, by having the RoboCut moving slowly or step by step.

"Radio fence", Keep RoboCut away from your neighbours"
I've been searching day and night for applications on the net, that can guide me to a good starting point for this fence...but, without success. Most interesting so far is an american product to keep your dog at your property. A buried wire, and a collar with a reciever for your dog. When the dog gets to close to the buried fence, he recieves a electric shock from the collar. Looks like theese system uses rather low-freq. signals, maybe in the audio-spectra

Have just got in contact with an american engineer who has an earlier creer at on of the manufactorers of buried wire dog fences. Hope i'll can get some advices from him.

00-06-24 Experimenting with the cutter..
WARNING! This is very dangerous and thoose experiments can easily cut your fingers of!!! Or even hurt you worse. DONT TRY ON YOUR OWN, We , MUX-Elektronik/ Robotshop are not responsible for any damage or injury caused by experiments like the ones we describe here

- Found an old recargable vacuum cleaner of the type we gave each other for X-mas some 10-15 years ago. This machine had two DC-motors, one for the "vacuum and one for a rotary brush. Unfortunately, it had a 6V power system based on a 6v Lead acumulator. The Fan-motor got absolutely crazy av 12 V, but, the other DC motor had the same measures but a much more reasonable power. I took the "FAN" and mounted it on the "brush-motor" Three holes where drille symetrically and i mounted blades for a hobby-knife of the type where you "breake off" the most outer part when you need an new sharp edge, we calle them "break-blade-knifes".

Then i dressed me in "covering clothes, protection glasses, a pair of thich rubber boots, and very thich leather protective gloves...then...POWER ON

00-06-14 Background :
We have initiated a project, based upon the BASIC Stamp 2, where we are trying to design a small robot, with the main task...to move the lawn.
The main idea is to make it small and lightweight, and having it workinh hour after hour, day after day. This way the robot will only have to "sip" the top of the grass, which will not demand to much power. Important is, that the bot can navigate and connect to its recarging-station.

The mover will have "razor-sharp" knifes" on a small rotating disk, and it will start its work on a "new-moved" lawn. We have already made a small selfcharging bot (se the GrowBot page) and it's thoose experiences that makes me believe that the project might workJag hoppas att de erfarenheter vi har sedan tidigare, bla med vår "självladdande Growbot" (se separat avdelning på vår web-site) skall ge oss vägledning och att flera befintliga lösningar skall kunna användas.

Size:
I'm planning a cutter width of approx 200 mm, RoboCut is planned to be about 270 mm wide and the weight is planned to be below 5 Kg


Electrical system:
12 Volt system, 10 R14 Ni Mh accus will give about 2.5 Ah. Thes will be reduced to 5 Volt for the controllert. Varför? Why?, well 12 Volts is a classic, and eg car industri maybe makes it easier to find electromechanical parts. Then, 12V in enough to create a reliable 5 V supply for the controller even when the accus are almost empty, i want the controller to be alive even when the system is almost empty, this way i can turn all powerconsuming stuff off and have RoboCut waiting for "rescue" with its sensors and communication awake.

Mechanics:
RoboCut has two large driving wheels and a third support wheel, driving with the large wheels first, it all looks like a bog GrowBot. the cutter will be a horuisontally monted rotary-disk, with three razor sharp knives, of a standar "hobby-tye" mounted symmetrically. The knives will be approx 2 cm outside of the cutterdisk, approx cutting diam 200 mm. this is of course a new area for us and there will be some testing and evaluting. Först we will build the "rolling platform" and see if we can have it avoiding obstacles, manouver etc...and see if its size and design will make it possible to take the project further and add cutter etc. Experiences regarding cutter-design, rpm etc are of course welcome!

Material:
The first proto well be build upon a board called "expo". This is a type of foam-board with very good stability and lightweigt...often used to build stands and displays at fairs and exhibition. Further on i might build in a red plexi/acryl-board that i have in my workshop.

Method

As i have told you before, i'm a "handy-man", but, as with many of you, i dont have daily acces to machines like a "bench-lathe" or a mill-machine. Well, during the years i have found ways of building machines anyway, specially with a technique based on "flat-boards" and a laser-printer. The main idea is to design in a CAD-system and then print the parts out in 1:1 scale, on Transparent, selfadhesive film, and attach the film direct on the board. This way i will have all measuers very accurate and no "built-up-errors" during the process. The film will also protect the board during the work.

Wheels:

I made the wheels with the tech from above. They have been sawn out of 6mm black "expo-board" The holes both the inner and the ones forming the "teeth" has been made with a simple "hole-saw", this is done BEFORE the outher-diameter is sawn. even the third support wheel will be made in a similar way, but right now, i'll use a standard (heavey and overdesigned, can take a load of 40 kg) The whhel-centers that attaches th the gearbox-shaft is a job for the lathe, but right now i think i kan solve it with a few parts from my old meccano-kit.

DC-Motors:

Of Course a major topic. We need a good driving speed and a reasonable torque, at an optimum power-consumption. Speed, well, i have to take a chance here. Some time ago, sitting in a "sunchair" in my garden, i tried to visualize the machine mowing around between the appletrees. Think that a speed of 0,25-0,3 m/s will do fine, hard to tell how much it will be able to "Cut" at this speed, but time will tell.
The driving wheels have a diameter of 170 mm, which tells us that somewhere around 33 rpm will give the specified speed. Readers old enough, remenbers the old LP-record, which had this speed, so you can "see" it in your imagination first experiments where made with "Micro motor HL 149 12 V 90:1" Lets forget them instantly...they hardly had time to shoew that the speed is correct before thry where vaporized...

Much more sloid are theese two motors from Japan Servo Ltd, have just tested them briefly, but it looks very good! The specs are for 24 V but im running them on 12 Volt, will check the current soon, but they sound very power-effektive, no heat is produced and they have a good torque.

The Controller:

The brain will of course be a BASIC STAMP 2, hope the 16 I/O:s will be enough. Motor Interface, of course this should be solved with some nice MOS-FET solution, but right now im irritatde on the "losses" i see when i use classic drivers like ULN2003, and MOS-FET requiers hig-gate-voltages, charge-pumps or similar..So...at this moment i will use old-fashioned, reliable relays. GThe relays will be powered by a ULN 2003, a few led:s tells me which relays are "active...!

Navigating:
Initially, RoboCut will have the following setup of sensors:
- Two IROD-modules for obstacle detectioni fronten gör att RoboCut väjer för hinder.
- Two sensors , right rep left to detect the buried wire fence.e.
- One IR-sensor for navigation back to the charger-station

The Irod-modulerna are very good, but expensive, further on i will replace them with discrete IR-components, similar to the setup we have been experimenting with on the BOE-BOT

The IR-solution for finding the charger-station has partly been developed already in our "take-me-home" project with a self-charging GrowBot.Den infraröda lösningen för att hitta till laddstationen har vi redan implementerat med vår "GrowBot".

Hans Forsberg / MUX info@robotshop.nu http://www.robotshop.nu

Butik: Kjellbergsgatan 5