File content as of revision 0:da791f233257:

/*
 * Controller.cpp
 * Copyright (c) 2018, ZHAW
 * All rights reserved.
 */

#include <cmath>
#include "Controller.h"

using namespace std;

const float Controller::PERIOD = 0.001f;                    // period of control task, given in [s]
const float Controller::PI = 3.14159265f;                   // the constant PI
const float Controller::WHEEL_DISTANCE = 0.170f;            // distance between wheels, given in [m]
const float Controller::WHEEL_RADIUS = 0.0375f;             // radius of wheels, given in [m]
const float Controller::COUNTS_PER_TURN = 1200.0f;          // resolution of encoder counter
const float Controller::LOWPASS_FILTER_FREQUENCY = 300.0f;  // frequency of lowpass filter for actual speed values, given in [rad/s]
const float Controller::KN = 40.0f;                         // speed constant of motor, given in [rpm/V]
const float Controller::KP = 0.2f;                          // speed controller gain, given in [V/rpm]
const float Controller::MAX_VOLTAGE = 12.0f;                // supply voltage for power stage in [V]
const float Controller::MIN_DUTY_CYCLE = 0.02f;             // minimum allowed value for duty cycle (2%)
const float Controller::MAX_DUTY_CYCLE = 0.98f;             // maximum allowed value for duty cycle (98%)

/**
 * Creates and initializes a Controller object.
 * @param pwmLeft a pwm output object to set the duty cycle for the left motor.
 * @param pwmRight a pwm output object to set the duty cycle for the right motor.
 * @param counterLeft an encoder counter object to read the position of the left motor.
 * @param counterRight an encoder counter object to read the position of the right motor.
 */
Controller::Controller(PwmOut& pwmLeft, PwmOut& pwmRight, EncoderCounter& counterLeft, EncoderCounter& counterRight) : pwmLeft(pwmLeft), pwmRight(pwmRight), counterLeft(counterLeft), counterRight(counterRight) {
    
    // initialize periphery drivers
    
    pwmLeft.period(0.00005f);
    pwmLeft.write(0.5f);
    
    pwmRight.period(0.00005f);
    pwmRight.write(0.5f);
    
    // initialize local variables
    
    translationalMotion.setProfileVelocity(1.5f);
    translationalMotion.setProfileAcceleration(1.5f);
    translationalMotion.setProfileDeceleration(3.0f);
    
    rotationalMotion.setProfileVelocity(3.0f);
    rotationalMotion.setProfileAcceleration(15.0f);
    rotationalMotion.setProfileDeceleration(15.0f);
    
    translationalVelocity = 0.0f;
    rotationalVelocity = 0.0f;
    actualTranslationalVelocity = 0.0f;
    actualRotationalVelocity = 0.0f;
    
    previousValueCounterLeft = counterLeft.read();
    previousValueCounterRight = counterRight.read();
    
    speedLeftFilter.setPeriod(PERIOD);
    speedLeftFilter.setFrequency(LOWPASS_FILTER_FREQUENCY);
    
    speedRightFilter.setPeriod(PERIOD);
    speedRightFilter.setFrequency(LOWPASS_FILTER_FREQUENCY);
    
    desiredSpeedLeft = 0.0f;
    desiredSpeedRight = 0.0f;
    
    actualSpeedLeft = 0.0f;
    actualSpeedRight = 0.0f;
    
    x = 0.0f;
    y = 0.0f;
    alpha = 0.0f;
    
    // start periodic task
    
    ticker.attach(callback(this, &Controller::run), PERIOD);
}

/**
 * Deletes the Controller object and releases all allocated resources.
 */
Controller::~Controller() {
    
    ticker.detach();
}

/**
 * Sets the desired translational velocity of the robot.
 * @param velocity the desired translational velocity, given in [m/s].
 */
void Controller::setTranslationalVelocity(float velocity) {
    
    this->translationalVelocity = velocity;
}

/**
 * Sets the desired rotational velocity of the robot.
 * @param velocity the desired rotational velocity, given in [rad/s].
 */
void Controller::setRotationalVelocity(float velocity) {
    
    this->rotationalVelocity = velocity;
}

/**
 * Gets the actual translational velocity of the robot.
 * @return the actual translational velocity, given in [m/s].
 */
float Controller::getActualTranslationalVelocity() {
    
    return actualTranslationalVelocity;
}

/**
 * Gets the actual rotational velocity of the robot.
 * @return the actual rotational velocity, given in [rad/s].
 */
float Controller::getActualRotationalVelocity() {
    
    return actualRotationalVelocity;
}

/**
 * Sets the actual x coordinate of the robots position.
 * @param x the x coordinate of the position, given in [m].
 */
void Controller::setX(float x) {
    
    this->x = x;
}

/**
 * Gets the actual x coordinate of the robots position.
 * @return the x coordinate of the position, given in [m].
 */
float Controller::getX() {
    
    return x;
}

/**
 * Sets the actual y coordinate of the robots position.
 * @param y the y coordinate of the position, given in [m].
 */
void Controller::setY(float y) {
    
    this->y = y;
}

/**
 * Gets the actual y coordinate of the robots position.
 * @return the y coordinate of the position, given in [m].
 */
float Controller::getY() {
    
    return y;
}

/**
 * Sets the actual orientation of the robot.
 * @param alpha the orientation, given in [rad].
 */
void Controller::setAlpha(float alpha) {
    
    this->alpha = alpha;
}

/**
 * Gets the actual orientation of the robot.
 * @return the orientation, given in [rad].
 */
float Controller::getAlpha() {
    
    return alpha;
}

/**
 * This method is called periodically by the ticker object and contains the
 * algorithm of the speed controller.
 */
void Controller::run() {
    
    // calculate the planned velocities using the motion planner
    
    translationalMotion.incrementToVelocity(translationalVelocity, PERIOD);
    rotationalMotion.incrementToVelocity(rotationalVelocity, PERIOD);
    
    // calculate the values 'desiredSpeedLeft' and 'desiredSpeedRight' using the kinematic model
    
    desiredSpeedLeft = (translationalMotion.velocity-WHEEL_DISTANCE/2.0f*rotationalMotion.velocity)/WHEEL_RADIUS*60.0f/2.0f/PI;
    desiredSpeedRight = -(translationalMotion.velocity+WHEEL_DISTANCE/2.0f*rotationalMotion.velocity)/WHEEL_RADIUS*60.0f/2.0f/PI;
    
    // calculate actual speed of motors in [rpm]
    
    short valueCounterLeft = counterLeft.read();
    short valueCounterRight = counterRight.read();
    
    short countsInPastPeriodLeft = valueCounterLeft-previousValueCounterLeft;
    short countsInPastPeriodRight = valueCounterRight-previousValueCounterRight;
    
    previousValueCounterLeft = valueCounterLeft;
    previousValueCounterRight = valueCounterRight;
    
    actualSpeedLeft = speedLeftFilter.filter((float)countsInPastPeriodLeft/COUNTS_PER_TURN/PERIOD*60.0f);
    actualSpeedRight = speedRightFilter.filter((float)countsInPastPeriodRight/COUNTS_PER_TURN/PERIOD*60.0f);
    
    // calculate motor phase voltages
    
    float voltageLeft = KP*(desiredSpeedLeft-actualSpeedLeft)+desiredSpeedLeft/KN;
    float voltageRight = KP*(desiredSpeedRight-actualSpeedRight)+desiredSpeedRight/KN;
    
    // calculate, limit and set duty cycles
    
    float dutyCycleLeft = 0.5f+0.5f*voltageLeft/MAX_VOLTAGE;
    if (dutyCycleLeft < MIN_DUTY_CYCLE) dutyCycleLeft = MIN_DUTY_CYCLE;
    else if (dutyCycleLeft > MAX_DUTY_CYCLE) dutyCycleLeft = MAX_DUTY_CYCLE;
    pwmLeft.write(dutyCycleLeft);
    
    float dutyCycleRight = 0.5f+0.5f*voltageRight/MAX_VOLTAGE;
    if (dutyCycleRight < MIN_DUTY_CYCLE) dutyCycleRight = MIN_DUTY_CYCLE;
    else if (dutyCycleRight > MAX_DUTY_CYCLE) dutyCycleRight = MAX_DUTY_CYCLE;
    pwmRight.write(dutyCycleRight);
    
    // calculate the values 'actualTranslationalVelocity' and 'actualRotationalVelocity' using the kinematic model
    
    actualTranslationalVelocity = (actualSpeedLeft-actualSpeedRight)*2.0f*PI/60.0f*WHEEL_RADIUS/2.0f;
    actualRotationalVelocity = (-actualSpeedRight-actualSpeedLeft)*2.0f*PI/60.0f*WHEEL_RADIUS/WHEEL_DISTANCE;
    
    // calculate the actual robot pose
    
    float deltaTranslation = actualTranslationalVelocity*PERIOD;
    float deltaOrientation = actualRotationalVelocity*PERIOD;
    
    x += cos(alpha+deltaOrientation)*deltaTranslation;
    y += sin(alpha+deltaOrientation)*deltaTranslation;
    float alpha = this->alpha+deltaOrientation;
    
    while (alpha > PI) alpha -= 2.0f*PI;
    while (alpha < -PI) alpha += 2.0f*PI;
    
    this->alpha = alpha;
}