hello,
I would like to create an object that can correct its balance.
The idea is to move a counterweight using a servomotor when the object starts to lose its balance. The servo corrects in real time the balance. For this, I am using an accelero/gyro to calculate the object orientation (using Jeff Rowberg library to have some good values). The accelero/gyro works very well.
That's what it looks like for now (it's just the first prototype..) :
Look at this vidéo. It is the same idea :
The counterweight moves as I was hoping but it doesn't work. The object oscillates and doesn't find its balance point. The servo/counterweight is too nervous and disturbs the object. It will never find the balance with a simple idea like i had.
The problem seems to be more complex.
Do you know if it's possible to correct the issue using some appropriate algorithms that can calculate how the servo should react ?
Do you know how it's possible to find the balance point in real time (like we can see in the video above) ?
Or do you know the principle of reaction wheel which seems to be a proper way to correct balance ?
Reaction wheels use gyroscopic effects to control orientation :
I didn't find some arduino detailed project using reaction wheel. And it seems really complicated to start to nothing...
I send you my little code. It's just a question of reading some good pitch values from accelero/gyro and sending the opposite value to the servo to correct the balance. The code does what it have to do but as i told you, it's not working. Too simple.
// try to move a counterweight using a servo to stabilize an object
// using Jeff Rowberg MPU6050 library, filter and quaternion algorithm
// I2Cdev and MPU6050 must be installed as libraries, or else the .cpp/.h files
// for both classes must be in the include path of your project
#include "I2Cdev.h"
#include "Servo.h"
#include "MPU6050_6Axis_MotionApps20.h"
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif
MPU6050 mpu;
Servo myservo;
// MPU control/status vars
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer
// orientation/motion vars
Quaternion q; // [w, x, y, z] quaternion container
VectorInt16 aa; // [x, y, z] accel sensor measurements
VectorInt16 aaReal; // [x, y, z] gravity-free accel sensor measurements
VectorInt16 aaWorld; // [x, y, z] world-frame accel sensor measurements
VectorFloat gravity; // [x, y, z] gravity vector
float euler[3]; // [psi, theta, phi] Euler angle container
float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector
// packet structure for InvenSense teapot demo
uint8_t teapotPacket[14] = { '
All ideas are welcom
thanks
, 0x02, 0,0, 0,0, 0,0, 0,0, 0x00, 0x00, '\r', '\n' };
const int buttonPin = 7; // button attach to pin 7
int etatbutton = 0; // trigger the button to have a reference value of balance, when the accelerometer/gyro is stabilized
int buttonState; // if the button is HIGH or LOW
int refvalue = 0; // the reference value of balance
int posservo = 0; // to stock pitch value each frame
int servominus = 0; // minimal value
int servoplus = 0; // maximal value
int valueOK = 0; // to stock the proper value i send in to the servo
// ================================================================
// === INTERRUPT DETECTION ROUTINE ===
// ================================================================
volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
void dmpDataReady() {
mpuInterrupt = true;
}
// ================================================================
// === INITIAL SETUP ===
// ================================================================
void setup() {
// join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
Wire.begin();
TWBR = 24; // 400kHz I2C clock (200kHz if CPU is 8MHz)
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
Fastwire::setup(400, true);
#endif
Serial.begin(115200);
while (!Serial); // wait for Leonardo enumeration, others continue immediately
// initialize device
Serial.println(F("Initializing I2C devices..."));
mpu.initialize();
// initialize button and servo
myservo.attach(11);
pinMode(buttonPin, INPUT);
myservo.write(90);
// verify connection
Serial.println(F("Testing device connections..."));
Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));
// wait for ready
Serial.println(F("\nSend any character to begin DMP programming and demo: "));
while (Serial.available() && Serial.read()); // empty buffer
while (!Serial.available()); // wait for data
while (Serial.available() && Serial.read()); // empty buffer again
// load and configure the DMP
Serial.println(F("Initializing DMP..."));
devStatus = mpu.dmpInitialize();
// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(220);
mpu.setYGyroOffset(76);
mpu.setZGyroOffset(-85);
mpu.setZAccelOffset(1788); // 1688 factory default for my test chip
// make sure it worked (returns 0 if so)
if (devStatus == 0) {
// turn on the DMP, now that it's ready
Serial.println(F("Enabling DMP..."));
mpu.setDMPEnabled(true);
// enable Arduino interrupt detection
Serial.println(F("Enabling interrupt detection (Arduino external interrupt 0)..."));
attachInterrupt(0, dmpDataReady, RISING);
mpuIntStatus = mpu.getIntStatus();
// set our DMP Ready flag so the main loop() function knows it's okay to use it
Serial.println(F("DMP ready! Waiting for first interrupt..."));
dmpReady = true;
// get expected DMP packet size for later comparison
packetSize = mpu.dmpGetFIFOPacketSize();
} else {
// ERROR!
// 1 = initial memory load failed
// 2 = DMP configuration updates failed
// (if it's going to break, usually the code will be 1)
Serial.print(F("DMP Initialization failed (code "));
Serial.print(devStatus);
Serial.println(F(")"));
}
}
// ================================================================
// === MAIN PROGRAM LOOP ===
// ================================================================
void loop() {
// if programming failed, don't try to do anything
if (!dmpReady) return;
// wait for MPU interrupt or extra packet(s) available
while (!mpuInterrupt && fifoCount < packetSize) {
// other program behavior stuff here
// .
// .
// .
// if you are really paranoid you can frequently test in between other
// stuff to see if mpuInterrupt is true, and if so, "break;" from the
// while() loop to immediately process the MPU data
// .
// .
// .
}
// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();
buttonState = digitalRead(buttonPin);
// get current FIFO count
fifoCount = mpu.getFIFOCount();
// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & 0x10) || fifoCount == 1024) {
// reset so we can continue cleanly
mpu.resetFIFO();
Serial.println(F("FIFO overflow!"));
// otherwise, check for DMP data ready interrupt (this should happen frequently)
} else if (mpuIntStatus & 0x02) {
// wait for correct available data length, should be a VERY short wait
while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();
// read a packet from FIFO
mpu.getFIFOBytes(fifoBuffer, packetSize);
// track FIFO count here in case there is > 1 packet available
// (this lets us immediately read more without waiting for an interrupt)
fifoCount -= packetSize;
// display Euler angles in degrees
if (buttonState == LOW && etatbutton == 0) { // waiting the accelero/gyro to be stabilize
mpu.dmpGetQuaternion(&q, fifoBuffer); // jeff rowberg job to have a good quat
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
Serial.println(ypr[2] * 180/M_PI); //print the pitch and waiting the accelero/gyro to be stabilize. Once it's ok, I trigger the button to have a reference value.
}
else if (buttonState == HIGH && etatbutton == 0) { // trigger the button
mpu.dmpGetQuaternion(&q, fifoBuffer); // jeff rowberg job to have a good quat
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
refvalue = ypr[1] * 180/M_PI; // stock a reference value of balance
servominus = (refvalue - 90); // determine minimal value
servoplus = (refvalue + 90); // determine maximal value
etatbutton = 1; // change state button to avoid to enter in this else if loop a second time
}
else {
mpu.dmpGetQuaternion(&q, fifoBuffer); // jeff rowberg job to have a good quat
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
posservo = ypr[1] * 180/M_PI; // stock pitch value
valueOK = map(posservo, servominus, servoplus, 0, 180); //map the pitch between servominus (reference value-90) and servoplus (reference value+90) to 0 and 180
if(valueOK>180) valueOK=180; // check if the value is not too high
if(valueOK<0) valueOK=0; // check if the value is not tt low
Serial.println(valueOK); // print the value
myservo.write(valueOK); // send to the servo
}
}
}
All ideas are welcom
thanks