Older blog entries for cschur (starting at number 101)

HI all,

Well, we have finished the first five chapters and are on the last one on our Docking Logic article. Weve covered all the theory and graphics, and now the final chapter - actual lab experiments testing the different technologies.

I hope to get the majority of the last chapter done by this time next week.

Write me.

Chris comets133@yahoo.com

Well, its been a whole month since I last posted, so here is our progress on the Docking Logic Project. The illustration graphics have been really killing me! So many of them, in such detail. Anyway I only have about ten more to go and ALL of the photos, movies, CAD graphics and yes schematics for the giant article will be DONE.

Maybe after this weekend. Then I have to start writing the mega article for you guys. we will cover beacons arrays, beacon sources, charging teqniques, docking tricks and methods, charging contacts and yes, even some of the pitfalls of the commonly used teqniques.

Im looking at getting this whole thing done in about a month I hope. But you know how that goes! ;)

Chris Schur Sr. Robotics Engineer Image Cam, Inc. Scottsdale, Az.

Hi all, Here is an update for the "Docking Logic" research.

We are on the last configuration to evaluate. So far, we have fully tested the pros and cons of these types:

1. Dual hoops contacts 2. cylinder contacts 3. Flat plate on wall

The final configuration is a bit uncertain at this point, but we are going to evaluate the method of simply driving the robot onto a flat charge plate to replenish. Its not as easy at it sounds! Using some sort conductive wheels is not a good choice, you dont want to know what metal wheels do to our wood floors in the house. Contacts that drag or drop to the ground may be one solution. I dont like dragging a set of contact brushes around the wood floor either. Once we have fully evaluated this technique, all the primary research is complete, and we will start the huge write up on the "Docking Logic" subject.

If you have some novel way your robot docks to charge, write us, we'd love to hear from you!



HI all,

The programming, and hardware on the robot is finished for our "Docking Logic" program, with the PICbot 5. We have a huge amount of writing up to do on what has been learned so far, a very in depth knowledge base for building a self charging robot.

We are now left with evaluation of three different contact configurations on the charging base:

Dual brass hoops

Antenna Post

Antenna flat plate

Here is the latest images, two new ones and a mpg movie of the PIC bot V with the charging base we are now evaluating:

http://www.schursastrophotography.com/robotics/picbot5main.h tml

Let me know what you think!

Chris comets133@yahoo.com

HI all,

We are about halfway through the "Docking Logic" research project after this weekend. It appears to be quite clear at this point, it requires four sensors to successfully dock your robot to a beacon localized charger, with a high percentage of success. These sensors are:

1. An omni directional "system" which detects proximity to the charger.

2. A precise becon homing sensor for final homing.

3. A frontal contact switch (could be bumper) to determine physical contact with the charger. Could also be a photocell.

4. A distance sensing device, such as IR ranging or sonar that allows the robot to slow to a fractional speed when very close to the charger to prevent it from "ramming" it at full speed. (you wont beleive how important this is!)

We have finished the omni cone prox sensor docking, and we are now replacing it with a multiple sensor ring around the robot to give it a rough idea which direction the beacon is when in the prox mode. The cone was fun, but this may be a better solution. (?)

The design of the shape and technique of electrical contacts is next, the two best contenders at this point are frontal contact plates which contact a pair of hoops at any angle, or whiskers that V into a post with contacts.

It must be remembered here that while any one can make a robot dock with its charger, doing it successfully and in a totally repeatalbe manner is lacking in the home robot world at this point. (and Im not talking about the horrendous helter skelter way robot vacs dock)

Write me about your docking experiences!



Hi all,

Our Docking Logic program is proceedng smoothly, and Ive posted a few intermediate images of the project in progress for you to see. The Picbot 5 robot has many faces during this program, sometimes a huge omni sensor on its back, other times a brass bladed beacon homing seonsor. Take a look:

http://www.schursastrophotography.com/robotics/picbot5main.h tml


Hi all,

we made great progress this weekend on our Docking Logic program. After determining the range and current requirements for detection with a PNA4602 last week, we next constructed an "Omni Cone" sensor. This is a reflective cone which directs the light from all directions to a single sensor below, and indicates the proximity to the charging base, but not its direction.

It took five pages of hand written mathematics to define how to make such a cone, and how to make one from a flat piece of reflective material starting with a circle with a pie shaped cutout.

Once the cone was made, we place the sensor under it at the calculated distance, and confirmed its optical properties by shining a laser horizontally at the inverted cone, and the beam hit square on to the center of the sensor, from all angles around the cone! Ill of coarse be posting this set of calculations so you can make an omni sensor for your robot as well in the final write up.

Next, we are working with directional sensors, and how to home in with perfect accuracy on the charging beacon.

Write me,



Hi all,

We are proceeding well with the first tests of the huge Docking Logic program. The sensitivity of the PNA4602 is startling to say the least! First we constructed an wave form generator by programming a PIC 12F629 chip to go high 12uS, and low 12us. We used a 20mhz xtal for accuracy. WE got 38.46mhz on the counter. That drives a 2n3904 which drives the IR Led. The range was tested with various in line current limiting resistors.

I first started with a standard 270 ohm, and had a range of over 20 feet to make the PNA device active! So powerful was the beam that the whole room lit up in IR and specular sources were everywhere. Next we put a 50k pot in line, and adjusted to set the distance the device would activate. Much to our suprise, even at 50k, the PNA device would slam on at about a foot. Phenomenal. For our testing, we will now vary the power level to simulate the effect of the beacon and how the robot will react to it at its limits as well as when it is strong.

Happy robots.

PS: did you get your wowee robots from macdonalds yet???


24 Feb 2007 (updated 24 Feb 2007 at 16:48 UTC) »

Hi all,

First of all, I want to key you in on what I found in Phoenix where I work yesterday - the Mcdonalds Robosapien Adventure meal! If your thing is those crazy humanoid bipeds, the minuature one at Mcdonalds will surely excite you.

Now, onto our project. We got our parts in the mail last night for our PicBot 5 program, Docking Logic. This will be the most extensive, lavishly illustrated project yet in this series, which have been recieved very well so far in the world wide robotics community Im happy to say. HEre is the outline for what we will be researching in "Docking Logic":

1. The Beacon sensor will be the venerable but getting obsolete Panasonic PNA4602, which runs at 38.5 khz. This will not interfere with the IR Prox sensors, which are the IS471 which run at a very different 8 khz. First we will determine the range for various IR LED combinations at the beacon source.

2. Next, we will evaluate using a omni cone reflector on the reciever and determine range and cone configuration.

3. Directional sensor design for homing on the beacon.

4. Robot path tracking from current position to beacon docking. I assume it will be some sort of zig zag S curve.

5. Beacon beam path aquisition. In other words, what to do when we encounter the docking beacon beam.

6. Charging base docking envelope. How accurately can we stop at the beacon in a position ready to charge?

7. STopping at the beacon/charging base in the exact spot without hitting it.

8. Electrical contacts for the determined docking postion envelope.

9. Error correction if docking is unsuccessful. In other words, adding some AI to the docking proceedure so the robot can react more intelligently to mis docking issues.

10. Spin Nav docking. (looking for the beacon with a photocell at the bottom of a tube)

11. Maybe docking with an omni sensor. (the Roomba uses this rather dubious method)

Note that I wont be covering the actual chargin proceedure yet, thats the Picbot 6 project!

Anyway, its going to be the most exciting project yet, and should fill a huge gap in the knowledge base for online tutorials on a subject that is often considered way too difficult to implement in a home robot - self charging.

Write me.



Just got back from a 3week vacation in southern arizona, we were fossil collecting with our friend that flew in from Australia. Anyway, thanks Steve for posting my article.

We are officially kicking off the next project now. The PicBot 5 program, will extensively detail one of the most important aspects of a household robots existance - Docking. This could be for battery charging, reseting wheel encoders to a known reference point, or simpy navigation of a complex area. Needless to say, if your robot cant dock, it cant "feed" and will cease to do its assigned task.

I will be using a new PIC for this project, the 16F876. It has many powerful features, and enable the docking proceedure to be successful.




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