Biorobotics 7 / Mbed 2 deprecated PID_example

PID controll for the robot motors.

Dependencies:   BioroboticsMotorControl MODSERIAL mbed

main.cpp@2:3be8cd780b3d, 2018-10-19 (annotated)

Committer:
brass_phoenix
Date:
Fri Oct 19 08:43:25 2018 +0000
Revision:
2:3be8cd780b3d
Parent:
1:28377623e8c9
Child:
3:689f3f2e78e8
+ Added threshold value for the motor to prevent jittering.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
brass_phoenix 0:7c204101adb0 1 #include "mbed.h"
brass_phoenix 0:7c204101adb0 2 #include "FastPWM.h"
brass_phoenix 0:7c204101adb0 3 #include "MODSERIAL.h"
brass_phoenix 0:7c204101adb0 4 #include "QEI.h"
brass_phoenix 0:7c204101adb0 5
brass_phoenix 1:28377623e8c9 6 #include "pid.h"
brass_phoenix 1:28377623e8c9 7
brass_phoenix 0:7c204101adb0 8 const float PI = 3.14159265359;
brass_phoenix 0:7c204101adb0 9 const int PULSES_PER_ROTATION = 6533; // Amount of motor encoder pulses per rotation. When using X4 encoding.
brass_phoenix 2:3be8cd780b3d 10 const float pid_period = 0.0001; // PID sample period in seconds.
brass_phoenix 0:7c204101adb0 11
brass_phoenix 2:3be8cd780b3d 12 const double Kp = 5.0;
brass_phoenix 2:3be8cd780b3d 13 const double Ki = 0.1;
brass_phoenix 2:3be8cd780b3d 14 const double Kd = 0.1;
brass_phoenix 2:3be8cd780b3d 15
brass_phoenix 2:3be8cd780b3d 16 const double motor_threshold_rps = 0.3; // Rad/s under which we send 0 to the motor, to prevent it from jittering around.
brass_phoenix 2:3be8cd780b3d 17 const double motor_stall_pwm = 0.5; // PWM fraction above which the motor starts to move.
brass_phoenix 2:3be8cd780b3d 18
brass_phoenix 2:3be8cd780b3d 19 int printcount = 0;
brass_phoenix 1:28377623e8c9 20
brass_phoenix 1:28377623e8c9 21 Ticker pidTicker; // Ticker function
brass_phoenix 0:7c204101adb0 22 FastPWM pwmpin1(D5); // SPECIFIC PIN (hoeft niet aangesloten te worden) Tells you how fast the motor has to go (later: pwmpin.write will tell you the duty cycle, aka how much voltage the motor gets)
brass_phoenix 0:7c204101adb0 23 FastPWM pwmpin2(D6); // SPECIFIC PIN (hoeft niet aangesloten te worden) Tells you how fast the motor has to go (later: pwmpin.write will tell you the duty cycle, aka how much voltage the motor gets)
brass_phoenix 0:7c204101adb0 24 DigitalOut directionpin1(D4); // SPECIFIC PIN (hoeft niet aangesloten te worden) Direction value (0-1) that the mbed will give the motor: in which direction the motor must rotate
brass_phoenix 0:7c204101adb0 25 DigitalOut directionpin2(D7); // SPECIFIC PIN (hoeft niet aangesloten te worden) Direction value (0-1) that the mbed will give the motor: in which direction the motor must rotate
brass_phoenix 0:7c204101adb0 26 AnalogIn potmeter1(A1); // Analoge input van potmeter 1 -> Motor 1
brass_phoenix 0:7c204101adb0 27 AnalogIn potmeter2(A2); // Analoge input van potmeter 2 -> Motor 2
brass_phoenix 0:7c204101adb0 28 QEI encoder1(D11, D10, NC, PULSES_PER_ROTATION, QEI::X4_ENCODING); // Reads encoder, connect pins of encoder 1 to D12 and D13; NC: not connected pin (for X4); 6533 prm (counts per rotation)
brass_phoenix 0:7c204101adb0 29 QEI encoder2(D13, D12, NC, PULSES_PER_ROTATION, QEI::X4_ENCODING); // Reads encoder, connect pins of encoder 2 to D12 and D13; NC: not connected pin (for X4); 6533 prm (counts per rotation)
brass_phoenix 0:7c204101adb0 30 Serial pc(USBTX, USBRX);
brass_phoenix 0:7c204101adb0 31
brass_phoenix 1:28377623e8c9 32 PID pid(pid_period);
brass_phoenix 1:28377623e8c9 33
brass_phoenix 0:7c204101adb0 34 // Updates a motor connected to the specified pins with the given speed.
brass_phoenix 1:28377623e8c9 35 // The speed can be both positive and negative, in the range [-1, 1].
brass_phoenix 1:28377623e8c9 36 void update_motor(DigitalOut* dir, FastPWM* pwm, double speed) {
brass_phoenix 1:28377623e8c9 37 if (speed < 1.0 && speed > 0) {
brass_phoenix 1:28377623e8c9 38 // Speed is in the range [0, 1] but the motor only moves
brass_phoenix 1:28377623e8c9 39 // in the range [0.5, 1]. Rescale for this.
brass_phoenix 2:3be8cd780b3d 40 speed = (speed * (1-motor_stall_pwm)) + motor_stall_pwm;
brass_phoenix 1:28377623e8c9 41 }
brass_phoenix 1:28377623e8c9 42 if (speed > -1.0 && speed < 0) {
brass_phoenix 1:28377623e8c9 43 // Speed is in the range [-1, 0] but the motor only moves
brass_phoenix 1:28377623e8c9 44 // in the range [-1, -0.5]. Rescale for this.
brass_phoenix 2:3be8cd780b3d 45 speed = (speed * (1-motor_stall_pwm)) - motor_stall_pwm;
brass_phoenix 1:28377623e8c9 46 }
brass_phoenix 1:28377623e8c9 47
brass_phoenix 0:7c204101adb0 48 // either true or false, determines direction (0 or 1)
brass_phoenix 1:28377623e8c9 49 *dir = speed > 0;
brass_phoenix 0:7c204101adb0 50 // pwm duty cycle can only be positive, floating point absolute value (if value is >0, the there still will be a positive value).
brass_phoenix 1:28377623e8c9 51 *pwm = fabs(speed);
brass_phoenix 0:7c204101adb0 52 }
brass_phoenix 0:7c204101adb0 53
brass_phoenix 1:28377623e8c9 54 double encoder_pulses_to_radians(int pulses) {
brass_phoenix 1:28377623e8c9 55 return (pulses/float(PULSES_PER_ROTATION)) * 2.0f*PI;
brass_phoenix 0:7c204101adb0 56 }
brass_phoenix 0:7c204101adb0 57
brass_phoenix 0:7c204101adb0 58 // Converts radians/s values into PWM values for motor controll.
brass_phoenix 0:7c204101adb0 59 // Both positive and negative values.
brass_phoenix 1:28377623e8c9 60 double radians_per_second_to_pwm(double rps) {
brass_phoenix 2:3be8cd780b3d 61 // If the rad/s is below the anti-jitter treshold, it is simply 0.
brass_phoenix 2:3be8cd780b3d 62 if (rps > 0 && rps < motor_threshold_rps) {
brass_phoenix 2:3be8cd780b3d 63 rps = 0;
brass_phoenix 2:3be8cd780b3d 64 }
brass_phoenix 2:3be8cd780b3d 65 if (rps < 0 && rps > motor_threshold_rps) {
brass_phoenix 2:3be8cd780b3d 66 rps = 0;
brass_phoenix 2:3be8cd780b3d 67 }
brass_phoenix 2:3be8cd780b3d 68
brass_phoenix 2:3be8cd780b3d 69
brass_phoenix 0:7c204101adb0 70 // With our specific motor, full PWM is equal to 1 round per second.
brass_phoenix 0:7c204101adb0 71 // Or 2PI radians per second.
brass_phoenix 1:28377623e8c9 72 double pwm_speed = rps / (2*PI);
brass_phoenix 1:28377623e8c9 73
brass_phoenix 2:3be8cd780b3d 74 // PWM speeds can only go between [-1, 1]
brass_phoenix 1:28377623e8c9 75 if (pwm_speed > 1) { pwm_speed = 1; }
brass_phoenix 1:28377623e8c9 76 if (pwm_speed < -1) { pwm_speed = -1; }
brass_phoenix 0:7c204101adb0 77 return pwm_speed;
brass_phoenix 0:7c204101adb0 78 }
brass_phoenix 0:7c204101adb0 79
brass_phoenix 0:7c204101adb0 80 // Normalizes a potmeter value from it's original range of [0, 1] to [-1, 1]
brass_phoenix 1:28377623e8c9 81 double normalize_pot(double pot_value) {
brass_phoenix 0:7c204101adb0 82 // scales value potmeter from 0-1 to -1 - 1.
brass_phoenix 0:7c204101adb0 83 return pot_value * 2 - 1;
brass_phoenix 0:7c204101adb0 84 };
brass_phoenix 0:7c204101adb0 85
brass_phoenix 0:7c204101adb0 86
brass_phoenix 0:7c204101adb0 87 void motorfunction() {
brass_phoenix 0:7c204101adb0 88 // reads out value potmeter 1 between 0-1
brass_phoenix 1:28377623e8c9 89 double pot = potmeter2.read();
brass_phoenix 1:28377623e8c9 90 double desired_angle = normalize_pot(pot) * PI; // Scale the potmeter to [-PI, PI]
brass_phoenix 0:7c204101adb0 91
brass_phoenix 0:7c204101adb0 92 int pulses = encoder2.getPulses();
brass_phoenix 1:28377623e8c9 93 double current_angle = encoder_pulses_to_radians(pulses);
brass_phoenix 0:7c204101adb0 94
brass_phoenix 1:28377623e8c9 95 double error = current_angle - desired_angle;
brass_phoenix 1:28377623e8c9 96 // PID controll.
brass_phoenix 1:28377623e8c9 97 double speed_rps = pid.update(error);
brass_phoenix 0:7c204101adb0 98
brass_phoenix 1:28377623e8c9 99 double speed_pwm = radians_per_second_to_pwm(speed_rps);
brass_phoenix 0:7c204101adb0 100
brass_phoenix 2:3be8cd780b3d 101 printcount++;
brass_phoenix 2:3be8cd780b3d 102 if (printcount >= 0.1L/pid_period) {
brass_phoenix 2:3be8cd780b3d 103 pc.printf("c_angle: %f, d_angle: %f, error: %f, rps: %f, speed: %f\n", current_angle, desired_angle, error, speed_rps, speed_pwm);
brass_phoenix 2:3be8cd780b3d 104 printcount = 0;
brass_phoenix 2:3be8cd780b3d 105 }
brass_phoenix 0:7c204101adb0 106
brass_phoenix 1:28377623e8c9 107 update_motor(&directionpin2, &pwmpin2, speed_pwm);
brass_phoenix 0:7c204101adb0 108 }
brass_phoenix 0:7c204101adb0 109
brass_phoenix 0:7c204101adb0 110
brass_phoenix 0:7c204101adb0 111 int main()
brass_phoenix 0:7c204101adb0 112 {
brass_phoenix 1:28377623e8c9 113 pc.baud(115200);
brass_phoenix 0:7c204101adb0 114 pc.printf("Starting.");
brass_phoenix 1:28377623e8c9 115 pid.set_k_values(Kp, Ki, Kd);
brass_phoenix 1:28377623e8c9 116 pidTicker.attach(motorfunction, pid_period);
brass_phoenix 0:7c204101adb0 117 pwmpin1.period_us(60.0); // 60 microseconds PWM period, 16.7 kHz, defines all PWM pins (only needs to be done once)
brass_phoenix 0:7c204101adb0 118 while(true){
brass_phoenix 0:7c204101adb0 119 } //Lege while loop zodat functie niet afloopt
brass_phoenix 0:7c204101adb0 120 }