Biorobotics 7 / BioroboticsMotorControl

PID motor controll for the biorobotics project.

Dependencies:   FastPWM QEI

Dependents:   PID_example Motor_calibration Demo_mode Demo_mode ... more

motor.cpp@8:bff5193c7d74, 2018-10-31 (annotated)

Committer:
brass_phoenix
Date:
Wed Oct 31 08:52:56 2018 +0000
Revision:
8:bff5193c7d74
Parent:
7:eb8787e7a5f5
Child:
9:48a0b4a67283
* fixed bug in reduction ratio.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
brass_phoenix 0:009e84d7af32 1 #include "motor.h"
brass_phoenix 0:009e84d7af32 2
brass_phoenix 2:b30a467e90d3 3 Motor::Motor(PinName pwm_pin, PinName dir_pin, PinName encoder_a, PinName encoder_b):
brass_phoenix 2:b30a467e90d3 4 pwm_out(pwm_pin),
brass_phoenix 2:b30a467e90d3 5 dir_out(dir_pin),
brass_phoenix 2:b30a467e90d3 6 encoder(encoder_a, encoder_b, NC, PULSES_PER_ROTATION, QEI::X4_ENCODING)
brass_phoenix 2:b30a467e90d3 7 {
brass_phoenix 2:b30a467e90d3 8 pid = PID();
brass_phoenix 2:b30a467e90d3 9
brass_phoenix 2:b30a467e90d3 10 target_angle = 0;
brass_phoenix 7:eb8787e7a5f5 11 extra_reduction_ratio = 1.0;
brass_phoenix 2:b30a467e90d3 12
brass_phoenix 2:b30a467e90d3 13 printcount = 0;
brass_phoenix 2:b30a467e90d3 14 pid_period = 0;
brass_phoenix 2:b30a467e90d3 15 serial_debugging = false;
brass_phoenix 2:b30a467e90d3 16
brass_phoenix 2:b30a467e90d3 17 // 60 microseconds PWM period, 16.7 kHz, defines all PWM pins (only needs to be done once)
brass_phoenix 2:b30a467e90d3 18 pwm_out.period_us(60.0);
brass_phoenix 2:b30a467e90d3 19 }
brass_phoenix 2:b30a467e90d3 20
brass_phoenix 0:009e84d7af32 21 Motor::Motor(PinName pwm_pin, PinName dir_pin, PinName encoder_a, PinName encoder_b, Serial* pc):
brass_phoenix 0:009e84d7af32 22 pwm_out(pwm_pin),
brass_phoenix 0:009e84d7af32 23 dir_out(dir_pin),
brass_phoenix 0:009e84d7af32 24 encoder(encoder_a, encoder_b, NC, PULSES_PER_ROTATION, QEI::X4_ENCODING)
brass_phoenix 0:009e84d7af32 25 {
brass_phoenix 0:009e84d7af32 26 pid = PID();
brass_phoenix 0:009e84d7af32 27
brass_phoenix 0:009e84d7af32 28 target_angle = 0;
brass_phoenix 0:009e84d7af32 29
brass_phoenix 0:009e84d7af32 30 printcount = 0;
brass_phoenix 0:009e84d7af32 31 pid_period = 0;
brass_phoenix 0:009e84d7af32 32 this->pc = pc;
brass_phoenix 2:b30a467e90d3 33 serial_debugging = true;
brass_phoenix 0:009e84d7af32 34
brass_phoenix 0:009e84d7af32 35 // 60 microseconds PWM period, 16.7 kHz, defines all PWM pins (only needs to be done once)
brass_phoenix 0:009e84d7af32 36 pwm_out.period_us(60.0);
brass_phoenix 0:009e84d7af32 37 }
brass_phoenix 0:009e84d7af32 38
brass_phoenix 0:009e84d7af32 39 void Motor::start(float period) {
brass_phoenix 0:009e84d7af32 40 pid_period = period;
brass_phoenix 0:009e84d7af32 41 pid.set_period(period);
brass_phoenix 4:5353c5d0d2ed 42 motor_ticker.attach(callback(this, &Motor::update), period);
brass_phoenix 4:5353c5d0d2ed 43 }
brass_phoenix 4:5353c5d0d2ed 44
brass_phoenix 4:5353c5d0d2ed 45 void Motor::stop() {
brass_phoenix 4:5353c5d0d2ed 46 motor_ticker.detach();
brass_phoenix 6:d83c79716ea1 47 target_angle = get_current_angle();
brass_phoenix 4:5353c5d0d2ed 48 // Stop the actual motor.
brass_phoenix 4:5353c5d0d2ed 49 pwm_out = 0.0;
brass_phoenix 4:5353c5d0d2ed 50 dir_out = 0;
brass_phoenix 4:5353c5d0d2ed 51
brass_phoenix 4:5353c5d0d2ed 52 pid.clear_state();
brass_phoenix 4:5353c5d0d2ed 53
brass_phoenix 4:5353c5d0d2ed 54 printcount = 0;
brass_phoenix 0:009e84d7af32 55 }
brass_phoenix 0:009e84d7af32 56
brass_phoenix 5:5537072b0e2e 57 void Motor::set_current_angle_as_zero() {
brass_phoenix 5:5537072b0e2e 58 encoder.reset();
brass_phoenix 5:5537072b0e2e 59 target_angle = 0;
brass_phoenix 5:5537072b0e2e 60 }
brass_phoenix 5:5537072b0e2e 61
brass_phoenix 0:009e84d7af32 62 void Motor::set_pid_k_values(double k_p, double k_i, double k_d) {
brass_phoenix 0:009e84d7af32 63 pid.set_k_values(k_p, k_i, k_d);
brass_phoenix 0:009e84d7af32 64 }
brass_phoenix 0:009e84d7af32 65
brass_phoenix 7:eb8787e7a5f5 66 void Motor::set_extra_reduction_ratio(double ratio) {
brass_phoenix 7:eb8787e7a5f5 67 extra_reduction_ratio = ratio;
brass_phoenix 7:eb8787e7a5f5 68 }
brass_phoenix 7:eb8787e7a5f5 69
brass_phoenix 0:009e84d7af32 70 void Motor::set_target_angle(double angle) {
brass_phoenix 8:bff5193c7d74 71 target_angle = angle / extra_reduction_ratio;
brass_phoenix 0:009e84d7af32 72 }
brass_phoenix 0:009e84d7af32 73
brass_phoenix 0:009e84d7af32 74 double Motor::get_current_angle() {
brass_phoenix 7:eb8787e7a5f5 75 return encoder_pulses_to_radians(encoder.getPulses()) * extra_reduction_ratio;
brass_phoenix 0:009e84d7af32 76 }
brass_phoenix 0:009e84d7af32 77
brass_phoenix 0:009e84d7af32 78 void Motor::update() {
brass_phoenix 0:009e84d7af32 79 int pulses = encoder.getPulses();
brass_phoenix 0:009e84d7af32 80 double current_angle = encoder_pulses_to_radians(pulses);
brass_phoenix 0:009e84d7af32 81
brass_phoenix 0:009e84d7af32 82 double error = current_angle - target_angle;
brass_phoenix 0:009e84d7af32 83 // PID controll.
brass_phoenix 0:009e84d7af32 84 double speed_rps = pid.update(error);
brass_phoenix 0:009e84d7af32 85
brass_phoenix 0:009e84d7af32 86 double speed_pwm = radians_per_second_to_pwm(speed_rps);
brass_phoenix 0:009e84d7af32 87
brass_phoenix 2:b30a467e90d3 88 if (serial_debugging) {
brass_phoenix 2:b30a467e90d3 89
brass_phoenix 2:b30a467e90d3 90 printcount++;
brass_phoenix 2:b30a467e90d3 91 if (printcount >= 0.1L/pid_period) {
brass_phoenix 2:b30a467e90d3 92 pc->printf("c_angle: %f, d_angle: %f, error: %f, rps: %f, speed: %f\n", current_angle, target_angle, error, speed_rps, speed_pwm);
brass_phoenix 2:b30a467e90d3 93 printcount = 0;
brass_phoenix 2:b30a467e90d3 94 }
brass_phoenix 0:009e84d7af32 95 }
brass_phoenix 0:009e84d7af32 96
brass_phoenix 0:009e84d7af32 97 update_motor_speed(speed_pwm);
brass_phoenix 0:009e84d7af32 98 }
brass_phoenix 0:009e84d7af32 99
brass_phoenix 0:009e84d7af32 100
brass_phoenix 0:009e84d7af32 101 void Motor::update_motor_speed(double speed) {
brass_phoenix 0:009e84d7af32 102 if (speed < 1.0 && speed > 0) {
brass_phoenix 0:009e84d7af32 103 // Speed is in the range [0, 1] but the motor only moves
brass_phoenix 0:009e84d7af32 104 // in the range [0.5, 1]. Rescale for this.
brass_phoenix 0:009e84d7af32 105 speed = (speed * (1-MOTOR_STALL_PWM)) + MOTOR_STALL_PWM;
brass_phoenix 0:009e84d7af32 106 }
brass_phoenix 0:009e84d7af32 107 if (speed > -1.0 && speed < 0) {
brass_phoenix 0:009e84d7af32 108 // Speed is in the range [-1, 0] but the motor only moves
brass_phoenix 0:009e84d7af32 109 // in the range [-1, -0.5]. Rescale for this.
brass_phoenix 0:009e84d7af32 110 speed = (speed * (1-MOTOR_STALL_PWM)) - MOTOR_STALL_PWM;
brass_phoenix 0:009e84d7af32 111 }
brass_phoenix 0:009e84d7af32 112
brass_phoenix 0:009e84d7af32 113 // either true or false, determines direction (0 or 1)
brass_phoenix 0:009e84d7af32 114 dir_out = speed > 0;
brass_phoenix 0:009e84d7af32 115 // 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 0:009e84d7af32 116 pwm_out = fabs(speed);
brass_phoenix 0:009e84d7af32 117 }
brass_phoenix 0:009e84d7af32 118
brass_phoenix 0:009e84d7af32 119 double Motor::encoder_pulses_to_radians(int pulses) {
brass_phoenix 0:009e84d7af32 120 return (pulses/float(PULSES_PER_ROTATION)) * 2.0f*PI;
brass_phoenix 0:009e84d7af32 121 }
brass_phoenix 0:009e84d7af32 122
brass_phoenix 0:009e84d7af32 123
brass_phoenix 0:009e84d7af32 124 // Converts radians/s values into PWM values for motor controll.
brass_phoenix 0:009e84d7af32 125 // Both positive and negative values.
brass_phoenix 0:009e84d7af32 126 double Motor::radians_per_second_to_pwm(double rps) {
brass_phoenix 0:009e84d7af32 127 // If the rad/s is below the anti-jitter treshold, it is simply 0.
brass_phoenix 0:009e84d7af32 128 if (rps > 0 && rps < MOTOR_THRESHOLD_RPS) {
brass_phoenix 0:009e84d7af32 129 rps = 0;
brass_phoenix 0:009e84d7af32 130 }
brass_phoenix 0:009e84d7af32 131 if (rps < 0 && rps > -MOTOR_THRESHOLD_RPS) {
brass_phoenix 0:009e84d7af32 132 rps = 0;
brass_phoenix 0:009e84d7af32 133 }
brass_phoenix 0:009e84d7af32 134
brass_phoenix 0:009e84d7af32 135
brass_phoenix 0:009e84d7af32 136 // With our specific motor, full PWM is equal to 1 round per second.
brass_phoenix 0:009e84d7af32 137 // Or 2PI radians per second.
brass_phoenix 0:009e84d7af32 138 double pwm_speed = rps / (2*PI);
brass_phoenix 0:009e84d7af32 139
brass_phoenix 0:009e84d7af32 140 // PWM speeds can only go between [-1, 1]
brass_phoenix 0:009e84d7af32 141 if (pwm_speed > 1) { pwm_speed = 1; }
brass_phoenix 0:009e84d7af32 142 if (pwm_speed < -1) { pwm_speed = -1; }
brass_phoenix 0:009e84d7af32 143 return pwm_speed;
brass_phoenix 0:009e84d7af32 144 }