Monday, September 6, 2021

Tilt! - A Self Balancing Robot (#9) - The Balancing Act


New Gearboxes are installed time to make the balancing happen. - with video!


Ugh, I spent a whole session trying to figure out why the M6050 was not communicating with the I2C bus.  It was clearly visible but no connection.  It seems that the circuit would prefer to have 3.3V in the Vcc, I was sending 5V.  Switching to 3.3V solved the problem. On to the next stage.

here are the first results:

First Test default:

double Kp = 40; // First adjustment
double Kd = 1.1; // Second adjustment
double Ki = 0; // Third adjustment

This seemed to be working, but the reaction of the motors was a bit off.  Some quick searches of LMotorController motorController() didn't reveal too much.  But I do see a factor in the code for the left and right speed factor.  These were set to 0.6.  IF these are associated to tune down the PWM signal sent to the motors, then it could mean that it is under powering.  I moved these to .8 and got a much more robust effect on the motors. On to Tuning the PID

Second Set  Test  default:
double Kp = 50; // First adjustment
double Kd = 1.0; // Second adjustment
double Ki = 0; // Third adjustment

I am getting some oscillation now, the Kd starts to tune this down.  Clearly from the video the robot has a tendency to lean in one direction.  I adjust the frame by putting hot glue between the sections, just squeezing it in and letting it harden.  I also suspect that the battery (weight inside) may be shifting forward. Using some cork, have wedged it in to prevent momentive shifting.

Third Set  Test  default:

double Kp = 55; // First adjustment
double Kd = 1.0; // Second adjustment
double Ki = 0; // Third adjustment

This was the most aggressive on the Proportional control constant that I used in the First Session. Certainly a little more 'attack' on the balance change. Starting to get some stable oscillations. 

Forth Set  Test  default:

double Kp = 55; // First adjustment
double Kd = 1.0; // Second adjustment
double Ki = 10; // Third adjustment

With this change, I added the Ki - Integral constant in to the PID. The result of Integral is to help smooth out the oscillations. There is a negative effect of controller 'Wind-up' as the integral values do not dissipate quickly. However I do not think I experienced this in this session. 

Overall the new settings in this set were not as desirable as the previous settings. Stability, subjectively, was reduced. Also, it seemed that I had a 'short' or disconnect in the power - OR - the PID was overwhelmed and stopped for about 1/2 second. Tilt! just fell over, and then everything started back up. 

Weight Adjustment 

Finally, I added a moderately heavy weight to the top of the robot. I used a Transformer that I had salvaged out of speaker. The additional weight seemed to slow the 'jitter' of the oscillations. However, the motors were unable to overcome the falling weight when it was tilted.

It seems that the robot has a tilt that needs to be identified and removed.  This is also leading to instability.  perhaps it is associated with the 'level-ness' of the sensor.

And - after repeated testing the blue wheel started to fall off. This was a temporary solution to start with.  It seems the repeated jerking started to effect the friction connection that was holding it in place. 

Tilt! A Balancing Robot - 3D Printed, Recycled Motors

Next Steps

1) identify the source of the lean/tilt

2) attach some weight to the top

3) investigate using the 12V battery and 5V power source

4) investigate easy remote control solutions

Friday, August 13, 2021

Gearboxes for Recycled Printer Motors (video)

 For those interested in making Gearboxes for Recycled Printer motors.  I have posted a video on my YouTube Channel that shows the asseymbly of the gearbox. Unfortunatly, it is not an instructional video, but it does show how to build it.

Monday, August 9, 2021

Tilt! - A Self Balancing Robot (#8) - New Gearbox for Motor and Wheels


A new gearbox for the self balancing robot.

The reuse of the pulley system is not working on the robot. Therefore, I started the whole gearbox design for recycled printer motors.  Now that there is a somewhat functional gearbox, it is time to return to Tilt! and see how the gearbox can be applied.

Here are the parts!  Now, just Engineer a new Motor mount and Wheel assembly!  

Engineer That!

New Motor Gearboxes layout with the old mounting brackets

Rough draft started - the concept of the new mounting system will be similar to the previous design iteration. Now, instead of using pulleys on a wheel with an axel, the axel will be directly part of the output shaft of the gearbox.  There will be a single 22mm bearing to take the load/weight of the robot instead of transmitting that to the gearbox/motor.

New Motor mount and gearbox

The New motor mount is wider than the original chassis and will fit 'around' the existing battery box. This frame will take use of the 1cm holes to allow for easy modular construction.  The gearbox, has new brackets so that it can be screwed to the new mount.  The old wheels are reusable, I will have a friction dependent plug that sets in the hub of the wheel and securely fits the output shaft of the gearbox.

Tilt with new 3D printed Gearbox - more Torque, less speed

NEXT:  Look for the new video showing the assembly of the gearbox. This is not a full instructional video, but does show how a simple gearbox can be 3D printed to allow for the use of recycled printer motors in robot construction.

Sunday, July 11, 2021

Gearboxes for Recycled Printer Motors (#2)

The final prototype build of the 3D printed gearbox for using recycled printer motors.  To see the initial development, see Part 1.

First version of Gear Design (above) vs. Current version (below)

Here are the versions changes from my initial gear design to the current one used.  The latest version has fewer teeth and is slightly wider on the smaller in-set gear.  This has required the housing box to be increased in size.  I used this extra design cycle to increase the distance between the axles in addition.

First version (right) vs. Current version (left) - output gear/shaft missing from picture

The Assembled Gearbox
unfortunately, you can not see the internal gears, because of the inclosing housing.  This design is working.  It seems to be good tork on the output shaft. The rotational speed is significantly less (~6:1) than the motor speed.  Even better, it will run without getting jammed. 

The next steps will be to design in a method for securing the gearbox to the robot. This may be dependent on the robot it is being applied to. The gearbox increases the space required for the motors.  My robots tend to be small, so this will have significant impact.

In addition, I would like to remove the load from the output shaft using 8mm skateboard bearings.  Finally, the drive shaft will need to be adjusted to provide a better attachment method for the output. 

Recycled Printer Motor 3D Printed Gearbox - First Complete Prototype Build

Robot Application
Since 3D printed gearboxes are not the focus of my robot building, this initial disign is good enough for now to move forward.

The Milli Robot will be fitted with the new gearbox. The connection between the motor and the helix shaft has been problematic. The rotational rate was too fast. Frequent jamming (due to a broken stabilizer) resulted in the drive shaft burning out the drive gear. A gearbox and new stabilizer should get the robot development back on track.

Broken-bot Millipead Robot with the WildWormDrive
The motor to Drive section will be re-designed with the 3D Printed Gearbox

Tilt!  A self-balancing robot will also be fitted with the new gearboxes. The original concept to use recycled motors, used the belts from the printers. The belt system is functional, but the fast movements required to provide balance created slippage in the belt. Typically slippage can be reduced or removed with a tensioner. However, I think in this caseitwoudl be best just to replace the belts with a gearbox system.  The drive mechanism is not the focus of this robot, therefore simpler is better.

Tilt! Robot - will be redesigned using the 3D Printed gearbox
The pulley-belt system had too much slippage

Monday, June 7, 2021

2021 Game of Shrooms


The Totally Not Evil Robot Army will be participating in the 2021 Game of Shroom - Art Seek -n- Keep.  If you are in Düsseldorf, Germany on June 12th 2021, you can find original Totally Not Evil Robot Army Shroom-Art!

for more details and the Clues - see the page:  2021 Game of Shrooms

you can learn more from the official site:  Game of Shrooms

Goto my Shroom Page for the details and CLUES

The Shrooms are Growing!

Shrooms are next to famous Düsseldorf painter Heinrich Ludwig Philippi

Shrooms in the Wild!

2021 Game of Shrooms - Totally Not Evil Robot Army

Goto my Shroom Page for the details and CLUES

#gameofshrooms #shroomdrop #düsseldorf