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@10:d50c4957a193, 2018-10-31 (annotated)

Committer:
brass_phoenix
Date:
Wed Oct 31 10:38:38 2018 +0000
Revision:
10:d50c4957a193
Parent:
9:48a0b4a67283
Child:
11:34bd7f42c9db
+ UNTESTED: Added a way to set the motor reference angle.

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 9:48a0b4a67283 29 extra_reduction_ratio = 1.0;
brass_phoenix 0:009e84d7af32 30
brass_phoenix 0:009e84d7af32 31 printcount = 0;
brass_phoenix 0:009e84d7af32 32 pid_period = 0;
brass_phoenix 0:009e84d7af32 33 this->pc = pc;
brass_phoenix 2:b30a467e90d3 34 serial_debugging = true;
brass_phoenix 0:009e84d7af32 35
brass_phoenix 0:009e84d7af32 36 // 60 microseconds PWM period, 16.7 kHz, defines all PWM pins (only needs to be done once)
brass_phoenix 0:009e84d7af32 37 pwm_out.period_us(60.0);
brass_phoenix 0:009e84d7af32 38 }
brass_phoenix 0:009e84d7af32 39
brass_phoenix 0:009e84d7af32 40 void Motor::start(float period) {
brass_phoenix 0:009e84d7af32 41 pid_period = period;
brass_phoenix 0:009e84d7af32 42 pid.set_period(period);
brass_phoenix 4:5353c5d0d2ed 43 motor_ticker.attach(callback(this, &Motor::update), period);
brass_phoenix 4:5353c5d0d2ed 44 }
brass_phoenix 4:5353c5d0d2ed 45
brass_phoenix 4:5353c5d0d2ed 46 void Motor::stop() {
brass_phoenix 4:5353c5d0d2ed 47 motor_ticker.detach();
brass_phoenix 6:d83c79716ea1 48 target_angle = get_current_angle();
brass_phoenix 4:5353c5d0d2ed 49 // Stop the actual motor.
brass_phoenix 4:5353c5d0d2ed 50 pwm_out = 0.0;
brass_phoenix 4:5353c5d0d2ed 51 dir_out = 0;
brass_phoenix 4:5353c5d0d2ed 52
brass_phoenix 4:5353c5d0d2ed 53 pid.clear_state();
brass_phoenix 4:5353c5d0d2ed 54
brass_phoenix 4:5353c5d0d2ed 55 printcount = 0;
brass_phoenix 0:009e84d7af32 56 }
brass_phoenix 0:009e84d7af32 57
brass_phoenix 10:d50c4957a193 58 void Motor::define_current_angle_as_x_radians(double radians)() {
brass_phoenix 5:5537072b0e2e 59 encoder.reset();
brass_phoenix 5:5537072b0e2e 60 target_angle = 0;
brass_phoenix 10:d50c4957a193 61 rotation_frame_offset = radians;
brass_phoenix 5:5537072b0e2e 62 }
brass_phoenix 5:5537072b0e2e 63
brass_phoenix 0:009e84d7af32 64 void Motor::set_pid_k_values(double k_p, double k_i, double k_d) {
brass_phoenix 0:009e84d7af32 65 pid.set_k_values(k_p, k_i, k_d);
brass_phoenix 0:009e84d7af32 66 }
brass_phoenix 0:009e84d7af32 67
brass_phoenix 7:eb8787e7a5f5 68 void Motor::set_extra_reduction_ratio(double ratio) {
brass_phoenix 7:eb8787e7a5f5 69 extra_reduction_ratio = ratio;
brass_phoenix 7:eb8787e7a5f5 70 }
brass_phoenix 7:eb8787e7a5f5 71
brass_phoenix 0:009e84d7af32 72 void Motor::set_target_angle(double angle) {
brass_phoenix 10:d50c4957a193 73 // Preform calculation between motor angles and robot angles.
brass_phoenix 10:d50c4957a193 74 target_angle = (angle - rotation_frame_offset) / extra_reduction_ratio;
brass_phoenix 0:009e84d7af32 75 }
brass_phoenix 0:009e84d7af32 76
brass_phoenix 0:009e84d7af32 77 double Motor::get_current_angle() {
brass_phoenix 10:d50c4957a193 78 // Preform calculation between motor angles and robot angles.
brass_phoenix 10:d50c4957a193 79 return (encoder_pulses_to_radians(encoder.getPulses()) * extra_reduction_ratio) + rotation_frame_offset;
brass_phoenix 0:009e84d7af32 80 }
brass_phoenix 0:009e84d7af32 81
brass_phoenix 0:009e84d7af32 82 void Motor::update() {
brass_phoenix 0:009e84d7af32 83 int pulses = encoder.getPulses();
brass_phoenix 0:009e84d7af32 84 double current_angle = encoder_pulses_to_radians(pulses);
brass_phoenix 0:009e84d7af32 85
brass_phoenix 0:009e84d7af32 86 double error = current_angle - target_angle;
brass_phoenix 0:009e84d7af32 87 // PID controll.
brass_phoenix 0:009e84d7af32 88 double speed_rps = pid.update(error);
brass_phoenix 0:009e84d7af32 89
brass_phoenix 0:009e84d7af32 90 double speed_pwm = radians_per_second_to_pwm(speed_rps);
brass_phoenix 0:009e84d7af32 91
brass_phoenix 2:b30a467e90d3 92 if (serial_debugging) {
brass_phoenix 2:b30a467e90d3 93
brass_phoenix 2:b30a467e90d3 94 printcount++;
brass_phoenix 2:b30a467e90d3 95 if (printcount >= 0.1L/pid_period) {
brass_phoenix 2:b30a467e90d3 96 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 97 printcount = 0;
brass_phoenix 2:b30a467e90d3 98 }
brass_phoenix 0:009e84d7af32 99 }
brass_phoenix 0:009e84d7af32 100
brass_phoenix 0:009e84d7af32 101 update_motor_speed(speed_pwm);
brass_phoenix 0:009e84d7af32 102 }
brass_phoenix 0:009e84d7af32 103
brass_phoenix 0:009e84d7af32 104
brass_phoenix 0:009e84d7af32 105 void Motor::update_motor_speed(double speed) {
brass_phoenix 0:009e84d7af32 106 if (speed < 1.0 && speed > 0) {
brass_phoenix 0:009e84d7af32 107 // Speed is in the range [0, 1] but the motor only moves
brass_phoenix 0:009e84d7af32 108 // in the range [0.5, 1]. Rescale for this.
brass_phoenix 0:009e84d7af32 109 speed = (speed * (1-MOTOR_STALL_PWM)) + MOTOR_STALL_PWM;
brass_phoenix 0:009e84d7af32 110 }
brass_phoenix 0:009e84d7af32 111 if (speed > -1.0 && speed < 0) {
brass_phoenix 0:009e84d7af32 112 // Speed is in the range [-1, 0] but the motor only moves
brass_phoenix 0:009e84d7af32 113 // in the range [-1, -0.5]. Rescale for this.
brass_phoenix 0:009e84d7af32 114 speed = (speed * (1-MOTOR_STALL_PWM)) - MOTOR_STALL_PWM;
brass_phoenix 0:009e84d7af32 115 }
brass_phoenix 0:009e84d7af32 116
brass_phoenix 0:009e84d7af32 117 // either true or false, determines direction (0 or 1)
brass_phoenix 0:009e84d7af32 118 dir_out = speed > 0;
brass_phoenix 0:009e84d7af32 119 // 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 120 pwm_out = fabs(speed);
brass_phoenix 0:009e84d7af32 121 }
brass_phoenix 0:009e84d7af32 122
brass_phoenix 0:009e84d7af32 123 double Motor::encoder_pulses_to_radians(int pulses) {
brass_phoenix 0:009e84d7af32 124 return (pulses/float(PULSES_PER_ROTATION)) * 2.0f*PI;
brass_phoenix 0:009e84d7af32 125 }
brass_phoenix 0:009e84d7af32 126
brass_phoenix 0:009e84d7af32 127
brass_phoenix 0:009e84d7af32 128 // Converts radians/s values into PWM values for motor controll.
brass_phoenix 0:009e84d7af32 129 // Both positive and negative values.
brass_phoenix 0:009e84d7af32 130 double Motor::radians_per_second_to_pwm(double rps) {
brass_phoenix 0:009e84d7af32 131 // If the rad/s is below the anti-jitter treshold, it is simply 0.
brass_phoenix 0:009e84d7af32 132 if (rps > 0 && rps < MOTOR_THRESHOLD_RPS) {
brass_phoenix 0:009e84d7af32 133 rps = 0;
brass_phoenix 0:009e84d7af32 134 }
brass_phoenix 0:009e84d7af32 135 if (rps < 0 && rps > -MOTOR_THRESHOLD_RPS) {
brass_phoenix 0:009e84d7af32 136 rps = 0;
brass_phoenix 0:009e84d7af32 137 }
brass_phoenix 0:009e84d7af32 138
brass_phoenix 0:009e84d7af32 139
brass_phoenix 0:009e84d7af32 140 // With our specific motor, full PWM is equal to 1 round per second.
brass_phoenix 0:009e84d7af32 141 // Or 2PI radians per second.
brass_phoenix 0:009e84d7af32 142 double pwm_speed = rps / (2*PI);
brass_phoenix 0:009e84d7af32 143
brass_phoenix 0:009e84d7af32 144 // PWM speeds can only go between [-1, 1]
brass_phoenix 0:009e84d7af32 145 if (pwm_speed > 1) { pwm_speed = 1; }
brass_phoenix 0:009e84d7af32 146 if (pwm_speed < -1) { pwm_speed = -1; }
brass_phoenix 0:009e84d7af32 147 return pwm_speed;
brass_phoenix 0:009e84d7af32 148 }