Arduino PID seesaw: A ball balancing machine

prusaprinters

A take on norwegiancreation's PID ball balancing seesaw using an Arduino.Video of this working: <a href="https://gyazo.com/a7e7b8c4ef73c828a3449bddea8c76b7">https://gyazo.com/a7e7b8c4ef73c828a3449bddea8c76b7</a><a href="https://gyazo.com/194d471b278426e594c36b10ec67122b">https://gyazo.com/194d471b278426e594c36b10ec67122b</a><a href="https://gyazo.com/78c361639dc5b48876ff313b620b8ae2">https://gyazo.com/78c361639dc5b48876ff313b620b8ae2</a>  Parts:<ul><li>Arduino UNO</li><li>Mopei MG 996R or Hitec HS-422 Servo (most similar RC servos are fine)</li><li>Sharp GP2Y0A41SK0F IR sensor (8-30cm) (analog output)</li><li>2x Samsung 30Q 18650 batteries (anything that can power the servo is fine)</li><li>Standard 9v battery</li><li>10k potentiometer</li><li>Perforated electrical board</li><li>Ball bearing to balance or 3d print your own ball</li><li>2s 18650 battery case</li><li>9v → power barrel connector</li><li>x14 3mm bolts/screws for attaching the parts</li><li>x14 3mm nuts for attaching the parts</li><li>x14 washers for attaching the parts</li><li>Male XT30 plug (XT 60 or 90 would be better but I used XT30)</li><li>Female XT30 plug (XT 60 or 90 would be better but I used XT30)</li><li>6x Jumper pins</li><li>Spare wire for perf board</li><li>4x 3mm threaded hex standoff spacers</li><li>Aluminium servo arm (or print your own)</li><li>x5 rubber feet (these are not needed)</li></ul>This is pretty simple to put together. This can be done with a breadboard to avoid soldering; using the perf board.Here is the Arduino Code.<figure class="table" style="height:auto !important;width:1278.69px;"><table style="border-color:!important;border-width:0px;"><tbody><tr><td style="border-color:!important;border-width:0px;height:auto !important;padding:0px !important;width:auto !important;">123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128</td><td style="border-color:!important;border-width:0px;height:auto !important;padding:0px !important;width:1231.59px;"><code>#include <Servo.h></code><code> </code> <code>/*SERVO POSITION CONSTANTS*/</code><code>#define SERVO_OFFSET 1425   //center position</code><code>#define SERVO_MIN 1000</code><code>#define SERVO_MAX 1900</code><code> </code> <code>/*REFERENCE RANGE*/</code><code>#define REFERENCE_MIN 4.5</code><code>#define REFERENCE_MAX 7.0</code><code> </code> <code>/*DELTA T*/</code><code>#define DT 0.001  //seconds</code><code> </code> <code>/*PID PARAMETERS*/</code><code>#define Kp 0.7    //proportional coefficient</code><code>#define Ki 0.2    //integral coefficient</code><code>#define Kd 0.2    //derivative coefficient</code><code> </code> <code>/*UPSCALING TO Servo.writeMilliseconds*/</code><code>#define OUTPUT_UPSCALE_FACTOR 10</code><code> </code> <code>/*EMA ALPHAS*/</code><code>#define SENSOR_EMA_a 0.05</code><code>#define SETPOINT_EMA_a 0.01</code><code> </code> <code>/*SENSOR SPIKE NOISE HANDLING*/</code><code>#define SENSOR_NOISE_SPIKE_THRESHOLD 15</code><code>#define SENSOR_NOISE_LP_THRESHOLD 300</code><code> </code> <code>float</code> <code>mapfloat(float</code> <code>x, float</code> <code>in_min, float</code> <code>in_max, float</code> <code>out_min, float</code> <code>out_max);</code><code> </code> <code>Servo myservo;</code><code> </code> <code>/*ARDUINO PINS*/</code><code>int</code> <code>sensor_pin = 0;</code><code>int</code> <code>pot_pin = 1;</code><code>int</code> <code>servo_pin = 3;</code><code> </code> <code>/*EMA VARIABLE INITIALIZATIONS*/</code><code>float</code> <code>sensor_filtered = 0.0;</code><code>int</code> <code>pot_filtered = 0;</code><code> </code> <code>/*GLOBAL SENSOR SPIKE NOISE HANDLING VARIABLES*/</code><code>int</code> <code>last_sensor_value = analogRead(sensor_pin);</code><code>int</code> <code>old_sensor_value = analogRead(sensor_pin);</code><code> </code> <code>/*GLOBAL PID VARIABLES*/</code><code>float</code> <code>previous_error = 0;</code><code>float</code> <code>integral = 0;</code><code> </code> <code>void</code> <code>setup() {</code><code>  Serial.begin(115200);</code><code>  myservo.attach(servo_pin);</code><code>}</code><code> </code> <code>void</code> <code>loop() {</code><code>  /*START DELTA T TIMING*/</code><code>  unsigned long</code> <code>my_time = millis();</code><code> </code> <code>  /*READ POT AND RUN POT EMA*/</code><code>  int</code> <code>pot_value = analogRead(pot_pin);</code><code>  pot_filtered = (SETPOINT_EMA_a*pot_value) + ((1-SETPOINT_EMA_a)*pot_filtered);</code><code>   </code> <code>  /*MAP POT POSITION TO CM SETPOINT RANGE*/</code><code>  float</code> <code>setpoint = mapfloat((float)pot_filtered, 0.0, 1024.0, REFERENCE_MIN, REFERENCE_MAX);</code><code> </code> <code>  /*READ SENSOR DATA*/</code><code>  int</code> <code>sensor_value = analogRead(sensor_pin);</code><code> </code> <code>  /*REMOVE SENSOR NOISE SPIKES*/</code><code>  if(abs(sensor_value-old_sensor_value) > SENSOR_NOISE_LP_THRESHOLD || sensor_value-last_sensor_value < SENSOR_NOISE_SPIKE_THRESHOLD){  //everything is in order</code><code>    old_sensor_value = last_sensor_value;</code><code>    last_sensor_value = sensor_value;</code><code>  }</code><code>  else{                               //spike detected - set sample equal to last</code><code>    sensor_value = last_sensor_value;</code><code>  }</code><code>   </code> <code>  /*LINEARIZE SENSOR OUTPUT TO CENTIMETERS*/</code><code>  sensor_value = max(1,sensor_value);         //avoid dividing by zero</code><code>  float</code> <code>cm = (2598.42/sensor_value) - 0.42;</code><code>   </code> <code>  /*RUN SENSOR EMA*/</code><code>  sensor_filtered = (SENSOR_EMA_a*cm) + ((1-SENSOR_EMA_a)*sensor_filtered);</code><code> </code> <code>  /*PID CONTROLLER*/</code><code>  float</code> <code>error = setpoint - sensor_filtered;</code><code>  integral = integral + error*DT;</code><code>  float</code> <code>derivative = (error - previous_error)/DT;</code><code>  float</code> <code>output = (Kp*error + Ki*integral + Kd*derivative)*OUTPUT_UPSCALE_FACTOR;</code><code>  previous_error = error;</code><code> </code> <code>  /*PRINT TO SERIAL THE TERM CONTRIBUTIONS*/</code><code>  //Serial.print(Kp*error);</code><code>  //Serial.print(' ');</code><code>  //Serial.print(Ki*integral);</code><code>  //Serial.print(' ');</code><code>  //Serial.println(Kd*derivative);</code><code> </code> <code>  /*PRINT TO SERIAL FILTERED VS UNFILTERED SENSOR DATA*/</code><code>  //Serial.print(sensor_filtered);</code><code>  //Serial.print(' ');</code><code>  //Serial.println(cm);</code><code> </code> <code>  /*PREPARE AND WRITE SERVO OUTPUT*/</code><code>  int</code> <code>servo_output = round(output) + SERVO_OFFSET;</code><code>   </code> <code>  if(servo_output < SERVO_MIN){ //saturate servo output at min/max range servo_output = SERVO_MIN; } else if(servo_output > SERVO_MAX){</code><code>    servo_output = SERVO_MAX;</code><code>  }</code><code>   </code> <code>  myservo.writeMicroseconds(servo_output);  //write to servo</code><code> </code> <code>  /*PRINT TO SERIAL SETPOINT VS POSITION*/</code><code>  //Serial.print(sensor_filtered);</code><code>  //Serial.print(' ');</code><code>  //Serial.println(setpoint);</code><code> </code> <code>  /*WAIT FOR DELTA T*/</code><code>  //Serial.println(millis() - my_time);</code><code>  while(millis() - my_time < DT*1000);</code><code>}</code><code> </code> <code>float</code> <code>mapfloat(float</code> <code>x, float</code> <code>in_min, float</code> <code>in_max, float</code> <code>out_min, float</code> <code>out_max)</code><code>{</code><code> return</code> <code>(x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;</code><code>}</code></td></tr></tbody></table></figure>Original design I modified: <a href="https://www.norwegiancreations.com/2016/08/pid-seesaw-part-1-the-design/">https://www.norwegiancreations.com/2016/08/pid-seesaw-part-1-the-design/</a><a href="https://www.norwegiancreations.com/2016/08/the-seesaw-part-2-basic-pid-theory-and-arduino-implementation/">https://www.norwegiancreations.com/2016/08/the-seesaw-part-2-basic-pid-theory-and-arduino-implementation/</a> <h4> </h4>

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