David Grayson / Mbed 2 deprecated DeadReckoning

David's dead reckoning code for the LVBots competition on March 6th. Uses the mbed LPC1768, DRV8835, QTR-3RC, and two DC motors with encoders.

Dependencies:   PololuEncoder Pacer mbed GeneralDebouncer

turn_sensor.cpp@41:3ead1dd2cc3a, 2019-07-25 (annotated)

Committer:
DavidEGrayson
Date:
Thu Jul 25 03:20:41 2019 +0000
Revision:
41:3ead1dd2cc3a
Parent:
40:6fa672be85ec
Child:
42:96671b71aac5
Gyro: Add a hacky offset of +6.5 in TurnSensor.cpp.  The turn sensor drifts much more slowly now, like maybe 1 degree per minute.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
DavidEGrayson 40:6fa672be85ec 1 #include "turn_sensor.h"
DavidEGrayson 40:6fa672be85ec 2 #include "l3g.h"
DavidEGrayson 40:6fa672be85ec 3
DavidEGrayson 40:6fa672be85ec 4 void TurnSensor::reset()
DavidEGrayson 40:6fa672be85ec 5 {
DavidEGrayson 40:6fa672be85ec 6 angleUnsigned = 0;
DavidEGrayson 40:6fa672be85ec 7 }
DavidEGrayson 40:6fa672be85ec 8
DavidEGrayson 40:6fa672be85ec 9 void TurnSensor::start()
DavidEGrayson 40:6fa672be85ec 10 {
DavidEGrayson 40:6fa672be85ec 11 timer.start();
DavidEGrayson 40:6fa672be85ec 12 rate = 0;
DavidEGrayson 40:6fa672be85ec 13 angleUnsigned = 0;
DavidEGrayson 40:6fa672be85ec 14 gyroLastUpdate = timer.read_us();
DavidEGrayson 40:6fa672be85ec 15 }
DavidEGrayson 40:6fa672be85ec 16
DavidEGrayson 40:6fa672be85ec 17 void TurnSensor::update()
DavidEGrayson 40:6fa672be85ec 18 {
DavidEGrayson 40:6fa672be85ec 19 if (l3gZAvailable() == 1)
DavidEGrayson 40:6fa672be85ec 20 {
DavidEGrayson 40:6fa672be85ec 21 int32_t gz = l3gZRead();
DavidEGrayson 40:6fa672be85ec 22 if (gz < -500000)
DavidEGrayson 40:6fa672be85ec 23 {
DavidEGrayson 40:6fa672be85ec 24 // error
DavidEGrayson 40:6fa672be85ec 25 return;
DavidEGrayson 40:6fa672be85ec 26 }
DavidEGrayson 40:6fa672be85ec 27
DavidEGrayson 41:3ead1dd2cc3a 28 // The gyro zero rate on my robot, measured by testL3gAndCalibrate() on
DavidEGrayson 41:3ead1dd2cc3a 29 // 2019-07-24 is about -6.5. So let's add 6 half the time and add 7
DavidEGrayson 41:3ead1dd2cc3a 30 // the other half of the time. This is a big hack.
DavidEGrayson 41:3ead1dd2cc3a 31 static uint8_t updateCount = 0;
DavidEGrayson 41:3ead1dd2cc3a 32 updateCount++;
DavidEGrayson 41:3ead1dd2cc3a 33 gz = gz + 6 + (updateCount & 1);
DavidEGrayson 41:3ead1dd2cc3a 34
DavidEGrayson 40:6fa672be85ec 35 // The gyro on this robot is mounted upside down; account for that here so that
DavidEGrayson 40:6fa672be85ec 36 // we can have counter-clockwise be a positive rotation.
DavidEGrayson 41:3ead1dd2cc3a 37 gz = -gz;
DavidEGrayson 41:3ead1dd2cc3a 38
DavidEGrayson 40:6fa672be85ec 39 rate = gz;
DavidEGrayson 40:6fa672be85ec 40
DavidEGrayson 40:6fa672be85ec 41 // First figure out how much time has passed since the last update (dt)
DavidEGrayson 40:6fa672be85ec 42 uint16_t m = timer.read_us();
DavidEGrayson 40:6fa672be85ec 43 uint16_t dt = m - gyroLastUpdate;
DavidEGrayson 40:6fa672be85ec 44 gyroLastUpdate = m;
DavidEGrayson 40:6fa672be85ec 45
DavidEGrayson 40:6fa672be85ec 46 // Multiply dt by turnRate in order to get an estimation of how
DavidEGrayson 40:6fa672be85ec 47 // much the robot has turned since the last update.
DavidEGrayson 40:6fa672be85ec 48 // (angular change = angular velocity * time)
DavidEGrayson 40:6fa672be85ec 49 int32_t d = (int32_t)rate * dt;
DavidEGrayson 40:6fa672be85ec 50
DavidEGrayson 40:6fa672be85ec 51 // The units of d are gyro digits times microseconds. We need
DavidEGrayson 40:6fa672be85ec 52 // to convert those to the units of turnAngle, where 2^29 units
DavidEGrayson 40:6fa672be85ec 53 // represents 45 degrees. The conversion from gyro digits to
DavidEGrayson 40:6fa672be85ec 54 // degrees per second (dps) is determined by the sensitivity of
DavidEGrayson 40:6fa672be85ec 55 // the gyro: 0.07 degrees per second per digit.
DavidEGrayson 40:6fa672be85ec 56 //
DavidEGrayson 40:6fa672be85ec 57 // (0.07 dps/digit) * (1/1000000 s/us) * (2^29/45 unit/degree)
DavidEGrayson 40:6fa672be85ec 58 // = 14680064/17578125 unit/(digit*us)
DavidEGrayson 40:6fa672be85ec 59
DavidEGrayson 40:6fa672be85ec 60 angleUnsigned += (int64_t)d * 14680064 / 17578125;
DavidEGrayson 40:6fa672be85ec 61 }
DavidEGrayson 40:6fa672be85ec 62 }