Spring 2014, ECE 4180 project, Georgia Institute of Technolgoy. This is the autonomous driver program for the Robotics Cat and Mouse program.
Dependencies: IMUfilter ADXL345_I2C mbed ITG3200 USBHost mbed-rtos
Diff: IMU_RPY.h
- Revision:
- 0:84d5aa80fd77
- Child:
- 1:dacf7db790f6
diff -r 000000000000 -r 84d5aa80fd77 IMU_RPY.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/IMU_RPY.h Sun Apr 27 04:31:07 2014 +0000 @@ -0,0 +1,281 @@ + + + /** + * IMU filter example. + * + * Calculate the roll, pitch and yaw angles. + */ + #include "IMUfilter.h" + #include "ADXL345_I2C.h" + #include "ITG3200.h" + + //Gravity at Earth's surface in m/s/s + #define g0 9.812865328 + //Number of samples to average. + #define SAMPLES 4 + //Number of samples to be averaged for a null bias calculation + //during calibration. + #define CALIBRATION_SAMPLES 128 + //Convert from radians to degrees. + #define toDegrees(x) (x * 57.2957795) + //Convert from degrees to radians. + #define toRadians(x) (x * 0.01745329252) + //ITG-3200 sensitivity is 14.375 LSB/(degrees/sec). + #define GYROSCOPE_GAIN (1 / 14.375) + //Full scale resolution on the ADXL345 is 4mg/LSB. + #define ACCELEROMETER_GAIN (0.004 * g0) + //Sampling gyroscope at 200Hz. + #define GYRO_RATE 0.005 + //Sampling accelerometer at 200Hz. + #define ACC_RATE 0.005 + //Updating filter at 40Hz. + #define FILTER_RATE 0.1 + + //At rest the gyroscope is centred around 0 and goes between about + //-5 and 5 counts. As 1 degrees/sec is ~15 LSB, error is roughly + //5/15 = 0.3 degrees/sec. + IMUfilter imuFilter(FILTER_RATE, 0.3); + ADXL345_I2C accelerometer(p28, p27); + ITG3200 gyroscope(p28, p27); + Ticker accelerometerTicker; + Ticker gyroscopeTicker; + Ticker filterTicker; + + //Offsets for the gyroscope. + //The readings we take when the gyroscope is stationary won't be 0, so we'll + //average a set of readings we do get when the gyroscope is stationary and + //take those away from subsequent readings to ensure the gyroscope is offset + //or "biased" to 0. + double w_xBias; + double w_yBias; + double w_zBias; + + //Offsets for the accelerometer. + //Same as with the gyroscope. + double a_xBias; + double a_yBias; + double a_zBias; + + //Accumulators used for oversampling and then averaging. + volatile double a_xAccumulator = 0; + volatile double a_yAccumulator = 0; + volatile double a_zAccumulator = 0; + volatile double w_xAccumulator = 0; + volatile double w_yAccumulator = 0; + volatile double w_zAccumulator = 0; + + //Accelerometer and gyroscope readings for x, y, z axes. + volatile double a_x; + volatile double a_y; + volatile double a_z; + volatile double w_x; + volatile double w_y; + volatile double w_z; + + //Buffer for accelerometer readings. + int readings[3]; + //Number of accelerometer samples we're on. + int accelerometerSamples = 0; + //Number of gyroscope samples we're on. + int gyroscopeSamples = 0; + + /** + * Prototypes + */ + //Set up the ADXL345 appropriately. + void initializeAcceleromter(void); + //Calculate the null bias. + void calibrateAccelerometer(void); + //Take a set of samples and average them. + void sampleAccelerometer(void); + //Set up the ITG3200 appropriately. + void initializeGyroscope(void); + //Calculate the null bias. + void calibrateGyroscope(void); + //Take a set of samples and average them. + void sampleGyroscope(void); + //Update the filter and calculate the Euler angles. + void filter(void); + + void initializeAccelerometer(void) + { + + //Go into standby mode to configure the device. + accelerometer.setPowerControl(0x00); + //Full resolution, +/-16g, 4mg/LSB. + accelerometer.setDataFormatControl(0x0B); + //200Hz data rate. + accelerometer.setDataRate(ADXL345_200HZ); + //Measurement mode. + accelerometer.setPowerControl(0x08); + //See http://www.analog.com/static/imported-files/application_notes/AN-1077.pdf + wait_ms(22); + + } + + void sampleAccelerometer(void) + { + + //Have we taken enough samples? + if (accelerometerSamples == SAMPLES) { + + //Average the samples, remove the bias, and calculate the acceleration + //in m/s/s. + a_x = ((a_xAccumulator / SAMPLES) - a_xBias) * ACCELEROMETER_GAIN; + a_y = ((a_yAccumulator / SAMPLES) - a_yBias) * ACCELEROMETER_GAIN; + a_z = ((a_zAccumulator / SAMPLES) - a_zBias) * ACCELEROMETER_GAIN; + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + accelerometerSamples = 0; + + } else { + //Take another sample. + accelerometer.getOutput(readings); + + a_xAccumulator += (int16_t) readings[0]; + a_yAccumulator += (int16_t) readings[1]; + a_zAccumulator += (int16_t) readings[2]; + + accelerometerSamples++; + + } + + } + + void calibrateAccelerometer(void) + { + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + + //Take a number of readings and average them + //to calculate the zero g offset. + for (int i = 0; i < CALIBRATION_SAMPLES; i++) { + + accelerometer.getOutput(readings); + + a_xAccumulator += (int16_t) readings[0]; + a_yAccumulator += (int16_t) readings[1]; + a_zAccumulator += (int16_t) readings[2]; + + wait(ACC_RATE); + + } + + a_xAccumulator /= CALIBRATION_SAMPLES; + a_yAccumulator /= CALIBRATION_SAMPLES; + a_zAccumulator /= CALIBRATION_SAMPLES; + + //At 4mg/LSB, 250 LSBs is 1g. + a_xBias = a_xAccumulator; + a_yBias = a_yAccumulator; + a_zBias = (a_zAccumulator - 250); + + a_xAccumulator = 0; + a_yAccumulator = 0; + a_zAccumulator = 0; + + } + + void initializeGyroscope(void) + { + + //Low pass filter bandwidth of 42Hz. + gyroscope.setLpBandwidth(LPFBW_42HZ); + //Internal sample rate of 200Hz. (1kHz / 5). + gyroscope.setSampleRateDivider(4); + + } + + void calibrateGyroscope(void) + { + + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + + //Take a number of readings and average them + //to calculate the gyroscope bias offset. + for (int i = 0; i < CALIBRATION_SAMPLES; i++) { + + w_xAccumulator += gyroscope.getGyroX(); + w_yAccumulator += gyroscope.getGyroY(); + w_zAccumulator += gyroscope.getGyroZ(); + wait(GYRO_RATE); + + } + + //Average the samples. + w_xAccumulator /= CALIBRATION_SAMPLES; + w_yAccumulator /= CALIBRATION_SAMPLES; + w_zAccumulator /= CALIBRATION_SAMPLES; + + w_xBias = w_xAccumulator; + w_yBias = w_yAccumulator; + w_zBias = w_zAccumulator; + + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + + } + + void sampleGyroscope(void) + { + + //Have we taken enough samples? + if (gyroscopeSamples == SAMPLES) { + + //Average the samples, remove the bias, and calculate the angular + //velocity in rad/s. + w_x = toRadians(((w_xAccumulator / SAMPLES) - w_xBias) * GYROSCOPE_GAIN); + w_y = toRadians(((w_yAccumulator / SAMPLES) - w_yBias) * GYROSCOPE_GAIN); + w_z = toRadians(((w_zAccumulator / SAMPLES) - w_zBias) * GYROSCOPE_GAIN); + + w_xAccumulator = 0; + w_yAccumulator = 0; + w_zAccumulator = 0; + gyroscopeSamples = 0; + + } else { + //Take another sample. + w_xAccumulator += gyroscope.getGyroX(); + w_yAccumulator += gyroscope.getGyroY(); + w_zAccumulator += gyroscope.getGyroZ(); + + gyroscopeSamples++; + + } + + } + + void filter(void) + { + + //Update the filter variables. + imuFilter.updateFilter(w_y, w_x, w_z, a_y, a_x, a_z); + //Calculate the new Euler angles. + imuFilter.computeEuler(); + + } + + void rpy_init() + { + //Initialize inertial sensors. + initializeAccelerometer(); + calibrateAccelerometer(); + initializeGyroscope(); + //calibrateGyroscope(); + + + /* //Set up timers. + //Accelerometer data rate is 200Hz, so we'll sample at this speed. + accelerometerTicker.attach(&sampleAccelerometer, 0.005); + //Gyroscope data rate is 200Hz, so we'll sample at this speed. + gyroscopeTicker.attach(&sampleGyroscope, 0.005); + //Update the filter variables at the correct rate. + filterTicker.attach(&filter, FILTER_RATE);*/ + }