pimoroni-pico/micropython/examples/motor2040/position_tuning.py

import gc
import time
from pimoroni import Button, PID
from motor import Motor, motor2040
from encoder import Encoder, MMME_CPR

"""
A program to aid in the discovery and tuning of motor PID
values for position control. It does this by commanding the
motor to move repeatedly between two target angles and
plots the measured response.

Press "Boot" to exit the program.
"""

MOTOR_PINS = motor2040.MOTOR_A          # The pins of the motor being profiled
ENCODER_PINS = motor2040.ENCODER_A      # The pins of the encoder attached to the profiled motor
GEAR_RATIO = 50                         # The gear ratio of the motor
COUNTS_PER_REV = MMME_CPR * GEAR_RATIO  # The counts per revolution of the motor's output shaft

DIRECTION = 0                           # The direction to spin the motor in. NORMAL (0), REVERSED (1)
SPEED_SCALE = 5.4                       # The scaling to apply to the motor's speed to match its real-world speed

UPDATES = 100                           # How many times to update the motor per second
UPDATE_RATE = 1 / UPDATES
PRINT_WINDOW = 0.25                     # The time (in seconds) after a new target, to display print out motor values
MOVEMENT_WINDOW = 2.0                   # The time (in seconds) between each new target being set
PRINT_DIVIDER = 1                       # How many of the updates should be printed (i.e. 2 would be every other update)

# Multipliers for the different printed values, so they appear nicely on the Thonny plotter
SPD_PRINT_SCALE = 10                    # Driving Speed multipler

POSITION_EXTENT = 90                    # How far from zero to move the motor, in degrees

# PID values
POS_KP = 0.14                           # Position proportional (P) gain
POS_KI = 0.0                            # Position integral (I) gain
POS_KD = 0.0022                         # Position derivative (D) gain


# Free up hardware resources ahead of creating a new Encoder
gc.collect()

# Create a motor and set its speed scale
m = Motor(MOTOR_PINS, direction=DIRECTION, speed_scale=SPEED_SCALE, deadzone=0.0)

# Create an encoder, using PIO 0 and State Machine 0
enc = Encoder(0, 0, ENCODER_PINS, direction=DIRECTION, counts_per_rev=COUNTS_PER_REV, count_microsteps=True)

# Create the user button
user_sw = Button(motor2040.USER_SW)

# Create PID object for position control
pos_pid = PID(POS_KP, POS_KI, POS_KD, UPDATE_RATE)

# Enable the motor to get started
m.enable()

# Set the initial target position
pos_pid.target = POSITION_EXTENT


update = 0
print_count = 0

# Continually move the motor until the user button is pressed
while user_sw.raw() is not True:

    # Capture the state of the encoder
    capture = enc.capture()

    # Calculate the velocity to move the motor closer to the position target
    vel = pos_pid.calculate(capture.degrees, capture.degrees_per_second)

    # Set the new motor driving speed
    m.speed(vel)

    # Print out the current motor values and their targets,
    # but only for the first few updates and only every multiple
    if update < (PRINT_WINDOW * UPDATES) and print_count == 0:
        print("Pos =", capture.degrees, end=", ")
        print("Targ Pos =", pos_pid.target, end=", ")
        print("Speed = ", m.speed() * SPD_PRINT_SCALE)

    # Increment the print count, and wrap it
    print_count = (print_count + 1) % PRINT_DIVIDER

    update += 1     # Move along in time

    # Have we reached the end of this time window?
    if update >= (MOVEMENT_WINDOW * UPDATES):
        update = 0  # Reset the counter

        # Set the new position target to be the inverse of the current target
        pos_pid.target = 0.0 - pos_pid.target

    time.sleep(UPDATE_RATE)

# Disable the servo
m.disable()