File content as of revision 1:864a5f8bb886:

/*
* Parts of the code copied from PES lecture slides
*/

// include all necessary libraries
#include "mbed.h"
#include "QEI.h"
#include "math.h"

//intialize all pins
PwmOut motor1(D5);
PwmOut motor2(D6);
DigitalOut motor1Dir(D4); // direction of motor 1 (1 is ccw 0 is cw (looking at the shaft from the front))
DigitalOut motor2Dir(D7); // direction of motor 2 (1 is ccw 0 is cw (looking at the shaft from the front))
QEI motor1Encoder (D10,D11, NC, 624,QEI::X4_ENCODING);
QEI motor2Encoder (D12,D13, NC, 624,QEI::X4_ENCODING);
DigitalIn button1(D8); //button to move cw
DigitalIn button2(D9); //button to move ccw

//initialize variables
const float pi = 3.14159265358979323846; //value for pi
double positionIncrement = 30; // increment of angle when button pressed (1 is a whole rotation (360 degrees))

const double motor1KP=1.3; //Proportional gain of motor1 PI control
const double motor1KI=0.5; //Integral gain of motor1 PI control
const double motor1KD=0.5; // Differential gain of motor1 PID control

const double motor2KP=1.3; //Proportional gain of motor1 PI control
const double motor2KI=0.5; //Integral gain of motor1 PI control
const double motor2KD=0.5; // Differential gain of motor1 PID control

const double N=100; //LP filter coefficient
const double encoderToMotor= 0.000119047619047619; //proportion of the rotation of the motor to the rotation of the encoder
const double controllerTickerTime=0.01; //ticker frequency

double motor1ErrorInt=0; //error of motor1 for the integrating part of PI controller
double motor1ErrorDif=0; //error of motor1 for the integrating part of PI controller
double desiredAngle1 =0; //desired position of motor1

double motor2ErrorInt=0; //error of motor1 for the integrating part of PI controller
double motor2ErrorDif=0; //error of motor1 for the integrating part of PI controller
double desiredAngle2 =0; //desired position of motor1
//initialize ticker for checking and correcting the angle
Ticker myControllerTicker;

const float l1 = 460; //Length of the arm from base to joint 1 (arm1)   ENTER MANUALLY [mm]
const float l2 = 450; //length of the arm from joint 1 to the end-effector.(arm2)   ENTER MANUALLY [mm]
float x_des = 0; //(initial)desired x location of the end-effector (ee)
float y_des = l1+l2; //(initial) desired y location of the end-effector (ee)
float xe, ye, D, phi, q2, beta, alpha, q1; //other variables used in calculating the angle for the motors
//q1 is the angle for the base motor, q2 is the angle for the elbow motor, both in [rad]

double PIDController(double error, const double Kp, const double Ki, const double Kd, double Ts, const double N,double &intError, double &DifError){
    const double a1 = -4/(N*Ts+2);
    const double a2 = -(N*Ts-2)/(N*Ts+2);
    const double b0 = (4*Kp + 4*Kd*N + 2*Ki*Ts + 2*Kp*N*Ts + Ki*N*pow(Ts,2))/(2*N*Ts + 4);
    const double b1 = (Ki*N*pow(Ts,2) - 4*Kp - 4*Kd*N)/(N*Ts + 2);
    const double b2 = (4*Kp + 4*Kd*N - 2*Ki*Ts - 2*Kp*N*Ts + Ki*N*pow(Ts,2))/(2*N*Ts + 4);

    double v = error - a1*intError - a2*DifError;
    double u = b0*v + b1*intError + b2*DifError;
    DifError = intError;
    intError = v;
    return u;
}

//Code for motor angles as a function of the length and positions of the arms, for a double revolutional joint arm in 2D plane
void motorAngle(){
//Function for making sure the arm does not exceed its maximum reach
//if it tries to go beyond its max. reach
//it will try to reach a point within reach in the same direction as desired.
    xe = x_des;
    ye = y_des;
    while(pow(xe, 2)+pow(ye,2) > pow(l1+l2, 2)) {
        if (y_des == 0) {   //make sure you do not divide by 0 if ye == 0
            xe = x_des - 1;
        } else {
            xe = x_des - (x_des/y_des)/10;    //go to a smaller xe point on the same line
        }
        if (x_des == 0) {   //make sure you do not divide by 0 if xe == 0
            ye = y_des - 1;
        } else {
            ye = y_des - (y_des/x_des)/10;   //go to a smaller ye point on the same line
        }
        x_des = xe;
        y_des = ye;
    }

//from here on is the code for setting the angles for the motors
    D = ((pow(l1,2)+pow(l2,2))-pow(xe,2)-pow(ye,2))/(2*l1*l2); //D = cos(phi)
    phi = atan2(sqrt(1 - pow(D, 2)), D); //angle between arm1 and arm2, from arm1 to arm2 [rad]
    //Use atan2(sqrt(1 - pow(D, 2)),D) for "elbow down" position (like your right arm)
    q2 = pi - phi; //angle of arm2 with respect to the orientation of arm1, motor2 [rad]
    if (-pi/2 > q2) {       //Make sure the angle of motor2 doesn’t wreck our setup (max -90 or 90 degrees w.r.t. arm1)
        q2 = -pi/2;
    } else if ( q2 > pi/2) {
        q2 = pi/2;
    }
    beta = atan2(ye, xe); //angle between "line from origin to ee" and x-axis [rad]
    alpha = atan2(l2*sin(q2), l1+l2*cos(q2)); //angle between "line from origin to ee" and arm1 [rad]
    q1 = beta - alpha; //angle of arm 1 with respect to the x-axis, motor1 [rad]
    float 1radDeg = 180/pi; //amount of degrees in 1 radian
    float rad2rot = 1radDeg/360;
    desiredAngle1 = q1 * rad2rot;
    desiredAngle2 = q2 * rad2rot;
}

void motorButtonController(){
    double position1= encoderToMotor*motor1Encoder.getPulses();
    double posError1 = desiredAngle1 - position1;

    //change direction based on error sign
    if(PIDController( posError1, motor1KP, motor1KI,motor1KD, controllerTickerTime, N, motor1ErrorInt ,motor1ErrorDif)>0) {
        motor1Dir=0;
    } else {
        motor1Dir =1;
    }
    //set motor speed based on PI controller error
    motor1 = fabs(PIDController( posError1, motor1KP, motor1KI,motor1KD, controllerTickerTime, N, motor1ErrorInt ,motor1ErrorDif));

    double position2= encoderToMotor*motor2Encoder.getPulses();
    double posError2 = desiredAngle2 - position2;

    //change direction based on error sign
    if(PIDController( posError2, motor2KP, motor2KI,motor2KD, controllerTickerTime, N, motor2ErrorInt ,motor2ErrorDif)>0) {
        motor2Dir=0;
    } else {
        motor2Dir =1;
    }
    //set motor speed based on PI controller error
    motor2 = fabs(PIDController( posError2, motor2KP, motor2KI,motor2KD, controllerTickerTime, N, motor2ErrorInt ,motor2ErrorDif));

}

int main()
{
    wait(2);
    myControllerTicker.attach(&motorButtonController, controllerTickerTime);
    while(1) {
        if(!button1) {
            y_des+=positionIncrement;
            wait(0.5f);
        }

        if(!button2) {
            y_des-=positionIncrement;
            wait(0.5f);
        }
    }
}