Diff: motor.cpp

Revision:

0:009e84d7af32

Child:

2:b30a467e90d3

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/motor.cpp	Fri Oct 19 10:57:39 2018 +0000
@@ -0,0 +1,101 @@
+#include "motor.h"
+
+Motor::Motor(PinName pwm_pin, PinName dir_pin, PinName encoder_a, PinName encoder_b, Serial* pc):
+    pwm_out(pwm_pin),
+    dir_out(dir_pin),
+    encoder(encoder_a, encoder_b, NC, PULSES_PER_ROTATION, QEI::X4_ENCODING)
+    {
+    pid = PID();
+    
+    target_angle = 0;
+    
+    printcount = 0;
+    pid_period = 0;
+    this->pc = pc;
+    
+    // 60 microseconds PWM period, 16.7 kHz, defines all PWM pins (only needs to be done once)
+    pwm_out.period_us(60.0);
+}
+
+void Motor::start(float period) {
+    pid_period = period;
+    pid.set_period(period);
+    motor_ticker.attach(this, &Motor::update, period);
+}
+
+void Motor::set_pid_k_values(double k_p, double k_i, double k_d) {
+    pid.set_k_values(k_p, k_i, k_d);
+}
+
+void Motor::set_target_angle(double angle) {
+    target_angle = angle;
+}
+
+double Motor::get_current_angle() {
+    return encoder_pulses_to_radians(encoder.getPulses());
+}
+
+void Motor::update() {
+    int pulses = encoder.getPulses();
+    double current_angle = encoder_pulses_to_radians(pulses);
+    
+    double error = current_angle - target_angle;
+    // PID controll.
+    double speed_rps = pid.update(error);
+    
+    double speed_pwm = radians_per_second_to_pwm(speed_rps);
+    
+    printcount++;
+    if (printcount >= 0.1L/pid_period) {
+        pc->printf("c_angle: %f, d_angle: %f, error: %f, rps: %f, speed: %f\n", current_angle, target_angle, error, speed_rps, speed_pwm);
+        printcount = 0;
+    }
+    
+    update_motor_speed(speed_pwm);
+}
+
+
+void Motor::update_motor_speed(double speed) {
+    if (speed < 1.0 && speed > 0) {
+        // Speed is in the range [0, 1] but the motor only moves
+        // in the range [0.5, 1]. Rescale for this.
+        speed = (speed * (1-MOTOR_STALL_PWM)) + MOTOR_STALL_PWM;
+    }
+    if (speed > -1.0 && speed < 0) {
+        // Speed is in the range [-1, 0] but the motor only moves
+        // in the range [-1, -0.5]. Rescale for this.
+        speed = (speed * (1-MOTOR_STALL_PWM)) - MOTOR_STALL_PWM;
+    }
+    
+    // either true or false, determines direction (0 or 1)
+    dir_out = speed > 0;
+    // pwm duty cycle can only be positive, floating point absolute value (if value is >0, the there still will be a positive value).
+    pwm_out = fabs(speed);
+}
+
+double Motor::encoder_pulses_to_radians(int pulses) {
+    return (pulses/float(PULSES_PER_ROTATION)) * 2.0f*PI;
+}
+
+
+// Converts radians/s values into PWM values for motor controll.
+// Both positive and negative values.
+double Motor::radians_per_second_to_pwm(double rps) {
+    // If the rad/s is below the anti-jitter treshold, it is simply 0.
+    if (rps > 0 && rps < MOTOR_THRESHOLD_RPS) {
+        rps = 0;
+    }
+    if (rps < 0 && rps > -MOTOR_THRESHOLD_RPS) {
+        rps = 0;
+    }
+    
+    
+    // With our specific motor, full PWM is equal to 1 round per second.
+    // Or 2PI radians per second.
+    double pwm_speed = rps / (2*PI);
+    
+    // PWM speeds can only go between [-1, 1]
+    if (pwm_speed > 1) { pwm_speed = 1; }
+    if (pwm_speed < -1) { pwm_speed = -1; }
+    return pwm_speed;
+}
\ No newline at end of file