Diff: main.cpp

Revision:

0:7440a03255a7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Sep 10 14:03:00 2010 +0000
@@ -0,0 +1,345 @@
+/**
+ * Includes.
+ */
+#include "Motor.h"
+#include "QEI.h"
+#include "PID.h"
+#include "IMU.h"
+
+/**
+ * Defines.
+ */
+#define BUFFER_SIZE 1024 //Used for data logging arrays
+#define RATE 0.01        //PID loop timing
+
+//PID tuning constants.
+#define L_KC 0.4312 //Forward left motor Kc
+#define L_TI 0.1    //Forward left motor Ti
+#define L_TD 0.0    //Forward left motor Td
+#define R_KC 0.4620 //Forward right motor Kc
+#define R_TI 0.1    //Forward right motor Ti
+#define R_TD 0.0    //Forward right motor Td
+
+//PID input/output limits.
+#define L_INPUT_MIN 0     //Forward left motor minimum input
+#define L_INPUT_MAX 3000  //Forward left motor maximum input
+#define L_OUTPUT_MIN 0.0  //Forward left motor minimum output
+#define L_OUTPUT_MAX 0.9  //Forward left motor maximum output
+
+#define R_INPUT_MIN 0     //Forward right motor input minimum
+#define R_INPUT_MAX 3200  //Forward right motor input maximum
+#define R_OUTPUT_MIN 0.0  //Forward right motor output minimum
+#define R_OUTPUT_MAX 0.9  //Forward right motor output maximum
+
+//Physical dimensions.
+#define PULSES_PER_REV        624
+#define WHEEL_DIAMETER        58.928 //mm
+#define ROTATION_DISTANCE     220.0  //mm
+#define REVS_PER_ROTATION     (ROTATION_DISTANCE / WHEEL_DIAMETER)
+#define PULSES_PER_ROTATION   (REVS_PER_ROTATION * PULSES_PER_REV)
+#define PULSES_PER_MM         (PULSES_PER_REV / WHEEL_DIAMETER)
+#define DISTANCE_PER_PULSE    (WHEEL_DIAMETER / PULSES_PER_REV)
+#define ENCODING              2 //Use X2 encoding
+#define WHEEL_DISTANCE        (ROTATION_DISTANCE / DISTANCE_PER_PULSE)
+
+/**
+ * Function Prototypes
+ */
+void initializeMotors(void);
+void initializePid(void);
+//cmd = "move", "turn"
+//direction = "forward", "backward", "left", "right"
+//length = distance in metres or angle in degrees
+void processCommand(char* cmd, char* direction, float length);
+
+/**
+ * Globals
+ */
+
+//Debug.
+Serial pc(USBTX, USBRX);
+
+//Motor control.
+Motor leftMotor(p21, p20, p19);  //pwm, inB, inA
+Motor rightMotor(p22, p17, p18); //pwm, inA, inB
+QEI leftQei(p29, p30, NC, 624);  //chanA, chanB, index, ppr
+QEI rightQei(p27, p28, NC, 624); //chanB, chanA, index, ppr
+PID leftPid(L_KC, L_TI, L_TD, RATE);  //Kc, Ti, Td
+PID rightPid(R_KC, R_TI, R_TD, RATE); //Kc, Ti, Td
+//IMU and peripherals run at a different rate to the main PID loop.
+IMU imu(IMU_RATE, GYRO_MEAS_ERROR, ACCELEROMETER_RATE, GYROSCOPE_RATE);
+
+//Filesystem.
+LocalFileSystem local("local");
+
+//Left motor working variables.
+int leftPulses     = 0;
+int leftPrevPulses = 0;
+float leftVelocity = 0.0;
+float leftVelocityBuffer[BUFFER_SIZE];
+
+//Right motor working variables.
+int rightPulses     = 0;
+int rightPrevPulses = 0;
+float rightVelocity = 0.0;
+float rightVelocityBuffer[BUFFER_SIZE];
+
+//General working variables.
+float heading       = 0.0;
+float prevHeading   = 0.0;
+float degreesTurned = 0.0;
+float positionSetPoint = 0.0;
+float headingSetPoint  = 0.0;
+
+//Store the initial and end heading during a straight line section
+//in order to be able to correct turns.
+float startHeading = 0.0;
+float endHeading   = 0.0;
+
+//Command Parser.
+char  cmd0[16]; //{"move", "turn"}
+char  cmd1[16]; //{{"forward", "backward"}, {"left", "right"}}
+float cmd2 = 0; //{distance in METRES, angle in DEGREES}
+
+void initializeMotors(void) {
+
+    //Set motor PWM periods to 20KHz.
+    leftMotor.period(0.00005);
+    leftMotor.speed(0.0);
+
+    rightMotor.period(0.00005);
+    rightMotor.speed(0.0);
+
+}
+
+void initializePid(void) {
+
+    //Input and output limits have been determined
+    //empirically with the specific motors being used.
+    //Change appropriately for different motors.
+    //Input  units: counts per second.
+    //Output units: PwmOut duty cycle as %.
+    //Default limits are for moving forward.
+    leftPid.setInputLimits(L_INPUT_MIN, L_INPUT_MAX);
+    leftPid.setOutputLimits(L_OUTPUT_MIN, L_OUTPUT_MAX);
+    leftPid.setMode(AUTO_MODE);
+    rightPid.setInputLimits(R_INPUT_MIN, R_INPUT_MAX);
+    rightPid.setOutputLimits(R_OUTPUT_MIN, R_OUTPUT_MAX);
+    rightPid.setMode(AUTO_MODE);
+
+}
+
+void processCommand(char* cmd, char* direction, float length) {
+
+    //move command.
+    if (strcmp(cmd, "move") == 0) {
+
+        int i = 0; //Data log array index.
+
+        //The PID controller works in the % (unsigned) domain, so we'll
+        //need to multiply the output by -1 if our motors need
+        //to go "backwards".
+        int leftDirection  = 1;
+        int rightDirection = 1;
+
+        //Convert from metres into millimetres.
+        length *= 1000;
+        //Work out how many pulses are required to go that many millimetres.
+        length *= PULSES_PER_MM;
+        //Make sure we scale the number of pulses according to our encoding method.
+        length /= ENCODING;
+
+        positionSetPoint = length;
+
+        if (strcmp(direction, "forward") == 0) {
+            //Leave left and rightDirection as +ve.
+        } else if (strcmp(cmd1, "backward") == 0) {
+            //Change left and rightDirection to -ve.
+            leftDirection  = -1;
+            rightDirection = -1;
+        }
+
+        startHeading = imu.getYaw();
+
+        //With left set point == right set point, the rover veers off to the
+        //right - by slowing the right motor down slightly it goes relatively
+        //straight.
+        leftPid.setSetPoint(1000);
+        rightPid.setSetPoint(975);
+
+        //Keep going until we've moved the correct distance defined by the
+        //position set point. Take the absolute value of the pulses as we might
+        //be moving backwards.
+        while ((abs(leftPulses) < positionSetPoint) &&
+                (abs(rightPulses) < positionSetPoint)) {
+
+            //Get the current pulse count and subtract the previous one to
+            //calculate the current velocity in counts per second.
+            leftPulses = leftQei.getPulses();
+            leftVelocity = (leftPulses - leftPrevPulses) / RATE;
+            leftPrevPulses = leftPulses;
+            //Use the absolute value of velocity as the PID controller works
+            //in the % (unsigned) domain and will get confused with -ve values.
+            leftPid.setProcessValue(fabs(leftVelocity));
+            leftMotor.speed(leftPid.compute() * leftDirection);
+
+            rightPulses = rightQei.getPulses();
+            rightVelocity = (rightPulses - rightPrevPulses) / RATE;
+            rightPrevPulses = rightPulses;
+            rightPid.setProcessValue(fabs(rightVelocity));
+            rightMotor.speed(rightPid.compute() * rightDirection);
+
+            i++;
+
+            wait(RATE);
+
+        }
+
+        leftMotor.brake();
+        rightMotor.brake();
+
+        endHeading = imu.getYaw();
+
+    }
+    //turn command.
+    else if (strcmp(cmd0, "turn") == 0) {
+
+        //The PID controller works in the % (unsigned) domain, so we'll
+        //need to multiply the output by -1 for the motor which needs
+        //to go "backwards".
+        int leftDirection  = 1;
+        int rightDirection = 1;
+        headingSetPoint = length + (endHeading - startHeading);
+
+        //In case the rover tries to [pointlessly] turn >360 degrees.
+        if (headingSetPoint > 359.8) {
+
+            headingSetPoint -= 359.8;
+
+        }
+        
+        //Set up the right previous heading for the initial degreesTurned
+        //calculation.
+        prevHeading = fabs(imu.getYaw());
+
+        if (strcmp(cmd1, "left") == 0) {
+
+            //When turning left, the left motor needs to go backwards
+            //while the right motor goes forwards.
+            leftDirection  = -1;
+
+        } else if (strcmp(cmd1, "right") == 0) {
+
+            //When turning right, the right motor needs to go backwards
+            //while the left motor goes forwards.
+            rightDirection = -1;
+
+        }
+
+        //Turn slowly to ensure we don't overshoot the angle by missing
+        //the relatively slow readings [in comparison to the PID loop speed]
+        //from the IMU.
+        leftPid.setSetPoint(500);
+        rightPid.setSetPoint(500);
+
+        //Keep turning until we've moved through the correct angle as defined
+        //by the heading set point.
+        while (degreesTurned < headingSetPoint) {
+
+            //Get the new heading and subtract the previous heading to
+            //determine how many more degrees we've moved through.
+            //As we're only interested in the relative angle (as opposed to
+            //absolute) we'll take the absolute value of the heading to avoid
+            //any nastiness when trying to calculate angles as they jump from
+            //179.9 to -179.9 degrees.
+            heading = fabs(imu.getYaw());
+            degreesTurned += fabs(heading - prevHeading);
+            prevHeading = heading;
+
+            //Get the current pulse count and subtract the previous one to
+            //calculate the current velocity in counts per second.
+            leftPulses = leftQei.getPulses();
+            leftVelocity = (leftPulses - leftPrevPulses) / RATE;
+            leftPrevPulses = leftPulses;
+            //Use the absolute value of velocity as the PID controller works
+            //in the % (unsigned) domain and will get confused with -ve values.
+            leftPid.setProcessValue(fabs(leftVelocity));
+            leftMotor.speed(leftPid.compute() * leftDirection);
+
+            rightPulses = rightQei.getPulses();
+            rightVelocity = (rightPulses - rightPrevPulses) / RATE;
+            rightPrevPulses = rightPulses;
+            rightPid.setProcessValue(fabs(rightVelocity));
+            rightMotor.speed(rightPid.compute() * rightDirection);
+
+            wait(RATE);
+
+        }
+
+        leftMotor.brake();
+        rightMotor.brake();
+
+    }
+
+    //Reset working variables.
+    leftQei.reset();
+    rightQei.reset();
+
+    leftPulses     = 0;
+    leftPrevPulses = 0;
+    leftVelocity   = 0.0;
+    leftMotor.speed(0.0);
+
+    rightPulses     = 0;
+    rightPrevPulses = 0;
+    rightVelocity   = 0.0;
+    rightMotor.speed(0.0);
+
+    leftPid.setSetPoint(0.0);
+    leftPid.setProcessValue(0.0);
+    rightPid.setSetPoint(0.0);
+    rightPid.setProcessValue(0.0);
+
+    positionSetPoint = 0.0;
+    headingSetPoint  = 0.0;
+    heading          = 0.0;
+    prevHeading      = 0.0;
+    degreesTurned    = 0.0;
+
+}
+
+int main() {
+
+    pc.printf("Starting mbed rover test...\n");
+
+    initializeMotors();
+    initializePid();
+
+    //Some delay before we start moving.
+    wait(5);
+
+    //Open the command script.
+    FILE* commands = fopen("/local/commands.txt", "r");
+
+    //Check if we were successful in opening the command script.
+    if (commands == NULL) {
+        pc.printf("Could not open command file...\n");
+        exit(EXIT_FAILURE);
+    } else {
+        pc.printf("Succesfully opened command file!\n");
+    }
+
+    //While there's another line to read from the command script.
+    while (fscanf(commands, "%s%s%f", cmd0, cmd1, &cmd2) >= 0) {
+
+        pc.printf("%s %s %f\n", cmd0, cmd1, cmd2);
+
+        processCommand(cmd0, cmd1, cmd2);
+
+        wait(1);
+
+    }
+
+    fclose(commands);
+
+}