Arduino Segway

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Introduction: Arduino Segway

Hello!

More than 3 years ago I started to tinker a homemade segway. Though it's still not really finished (I have to replace the 250W Motors by 500W-models) my children are able to drive around.

If you're going to build one you will Need the following parts:

* wheelset: In my case I use 12 1/2 x 2.75 tires usually taken for dirt bikes (f.e. www.amazon.de/HMParts-REIFEN-MIT-SCHLAUCH-12/dp/B0038X9ODA; http://www.ebay.com/itm/Tire-Rear-Wheel-Mini-Pocket-Dirt-Bike-47cc-49cc-50cc-COOLSTER-QG-50-RX1-Traxxis-/182346539856?hash=item2a74b36350:g:BxUAAOSwh6xTtmwX&vxp=mtr)

* batteries: I use two 12V/12Ah lead accumulators to get 24V for the Motors

* Motors: At the moment two 24V/250W models but the 500W-motors are already waiting for their use

* for the axle I asked a local welder and some of my bicycle-parts (bar, stem) fit perfect too.

Step 1: The Motor Driver

First I tried a homemade full-bridge. To control it I used the analog-out (pwm) of the arduino. But with this variant I didn't succeed. Therefore I bought a commercial product, a 2x60A Motor Driver from sabertooth (www.dimensionengineering.com/products/sabertooth2x60).

The arduino is able to communicate with the sabertooth via a simplified serial code.

Step 2: The Angle Determination

To determinate the current angle I first used a separate accelerometer (ADXL335) and gyroscope (LY530AL). Last week I changed this Setup and the two boards have been replaced by the MPU6050.sensor, which combines the two elements.

The advantage of the gyroscope is, that accelerations don't influence the measurements. The disadvantage is, that the gyro has a drift and after a while the angle goes higher and higher.

The Advantage of the accelerometer is, that it doesn't show any drift like the gyro. But it's being influenced by accelerations, which change the Output.

A filter combines both pro's so the calculated angle is near the real value. This filter can be a simple complementary-filter (like in the Picture) or the more complicated kalman-filter. The Input of the kalman-filter is the actual angle measured by the accelerometer, the angular Speed measured by the gyroscope and the time-step between two measurements. With these Parameters the kalman-filter is able to calculate an angle, which follows the gyro in times of high accelerations and in times of less accelerations it approaches the value of the accelerometer. In the Picture you can see the drift of the gyro and the good Job of the filter.

Step 3: The PID-controller

The segway tries to get the angle down to 0°. If the angle is positive, the segway brakes or accelerates backwards. If it's negative the segway accelerates forward.

But which signal get the motors? This is exactly the task of the pid-Controller.

The proportional-part: The angle should be 0°. So the greater the angle, the higher the speed of the motors.

Mathematically you can write:

angle_error = angle_should - angle_is

p-Motor-value = k_p * angle_error

The integral-part: When the current angle isn't zero, the Controller tries to get the segway horizontally again. But this approach shouldn't be slow and the smaller the angle-values, the slower the changes. Therefore the Controller allows a faster approach with the disadvantage, that the movement doesn't stop at 0° and goes a bit to the other side. This behaviour is guaranteed by the integral-part. All the angles are added (integrated) and this integral over time should be Zero. So if the angle is f.e. positive for a while, the Controller tries to get the seqway into the negative area. This guaranteeds faster approaches...

Mathematically you can write:

error_sum_new = error_sum_old + error

i-motor-value = k_i * (error_sum_new)

error_sum_old = error_sum_new

The derivative-part: Not just the current angle is important but also the changes of the angle. Let me explain: If the angle is f.e. 10° and it doesn't Change a lot, the Motors don't need to correct this shift very fast. But if the angle is 10° and it changes very fast (high derivative), than the motors have to correct this also very fast.

Mathematically you can write:

d-motor-value = k_d * angular Speed

Finally you get: motor-value = p-motor-value + i-motor-value + d-motor-value

Step 4: The Complete Setup

Now it's time to start the segway. To drive not only straight ahead you have to mount two buttons. When you push f.e. the right one, the left Motor increases Speed and the right Motor slows down. To ensure smooth transitions the added and deducted value starts at zero and increases step by step (+0.5 every loop) until he reaches the maximum value (f.e. 30).

To try out your own segway I 've attached the simple program for you. Good luck and don't follow the segway-inventor James Heselden down a cliff ;-)

Maybe you want to take a look at my YouTube-channel: www.youtube.com/user/stopperl16/Videos

more physics projects: https://stoppi-homemade-physics.de/

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    40 Comments

    0
    SamM292
    SamM292

    4 months ago on Step 4

    Arduino and Motor Controls are my bread & butter stuffs. I have built a Car Racing simulator and a Go-Kart. This is what I was looking for. Thanks you Sir and Pinterest to send this to me. I already have a geared 500W 24V dc brushed motor, Arduino etc. Only other part that I need to buy is the Sabertooth 2x60. Will order it today.

    0
    quanhung19876
    quanhung19876

    7 months ago

    Why is MPU 6050 not getting result, not showing value and motor not running?

    0
    darthfader64
    darthfader64

    8 months ago

    Thanks for your post!!

    0
    drlexluthor
    drlexluthor

    Question 10 months ago

    I am having trouble downloading the .ino code, it show up as a broken link. If you have it and don't mind sending it to me, it would be greatly appreciated. Thx, Dean the_real_dean@yahoo.com

    0
    drlexluthor
    drlexluthor

    Answer 10 months ago

    i found one on ebay, $11.00 but the heat sink and fan are not included, another $10.00. it is just a generic h bridge with dual motor control.

    0
    Coskunkodr
    Coskunkodr

    Tip 2 years ago on Introduction

    hello, we are making a thesis, we use your segway software one to one, we have very little time left, we had problems about saberthoot, can we help you if we give you the fee?
    Coskunkodr@gmail.com

    0
    stoppi71
    stoppi71

    4 years ago

    Yes, you'll need a second button (voltage-divider with the 10 kOhm-resistor)... Pin 12 and 13 are low, if the button isn't pushed. If you push the button for steering, the signal goes high...

    Therefore I ask in the program: if (steering-button-right or left) = high then ...

    I've changed the Picture of the circuit, because in the first version the status was low if the button was pressed ;-)

    0
    Jinu Jogy
    Jinu Jogy

    Reply 2 years ago

    can u explain briefly about it. Also can we use potentiometer for steering the direction?

    0
    meghabhosale1503
    meghabhosale1503

    3 years ago

    Can i get full pdf of segways construction

    0
    YashS142
    YashS142

    Question 3 years ago on Introduction

    i m using 2 350 watt motors for segway.i have two 12 volt batteries that connect in series giving 24 volts.i want 14 amps current for each motor. how can i get that? what possible combination capacity of battery (voltage and current) should i use? i m using sebertooth motor driver 30*2 channels.please guide me for motor driver function and how i couple motors with wheels

    0
    YOSHIMINE
    YOSHIMINE

    Question 3 years ago

    Nice to meet you
    Your research is very good
    I am a teacher of an industrial high school in Japan.
    I have a request
    I referred to ”Step 4: The Complete Setup”, but the motor does not work.
    ”FXLSYHKIW6PNEU6.ino” could also be compiled.

    I'm sorry.I still need to study more.
    It would be greatly appreciated if you could explain the details.

    0
    AirraB
    AirraB

    3 years ago

    Can i use another motor driver? i would like to use your project as reference in my project but the driver that you used is not available in our country and the cost was too high heheh... can you give me some advice about the motor driver? thanks ^_^

    0
    sonasec
    sonasec

    4 years ago

    thank you for sharing, you have making the best project for me ..you're actually a professional engineer.!

    0
    pachanoid
    pachanoid

    4 years ago

    very good, am making a robot with that code, and its working!

    0
    HippieC
    HippieC

    4 years ago

    Way too advanced for me but i know some people in stockholm that made one at maker space. Was very impressed!

    0
    KonstantinL8
    KonstantinL8

    4 years ago

    Cool project and nicely documented!

    How much weight does the current setup (250W motors) carry around?
    and do you have some kind of encoders or odometry for the wheels?

    0
    SherylinRM
    SherylinRM

    4 years ago

    You definately have my vote.

    Thanks for this :)

    0
    stoppi71
    stoppi71

    Reply 4 years ago

    I've to thank ;-)

    0
    clothier_bruce
    clothier_bruce

    4 years ago

    My question, too: why did the Arduino PWM O/P and a bridge cct not work? What does the commercial controller do that a basic DIY set-up not do?