101 lines
3.7 KiB
Python
101 lines
3.7 KiB
Python
import gc
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import time
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from motor import Motor, motor2040
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from encoder import Encoder, MMME_CPR
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from pimoroni import Button, PID, NORMAL_DIR # , REVERSED_DIR
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"""
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A program to aid in the discovery and tuning of motor PID
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values for position control. It does this by commanding the
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motor to move repeatedly between two setpoint angles and
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plots the measured response.
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Press "Boot" to exit the program.
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"""
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MOTOR_PINS = motor2040.MOTOR_A # The pins of the motor being profiled
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ENCODER_PINS = motor2040.ENCODER_A # The pins of the encoder attached to the profiled motor
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GEAR_RATIO = 50 # The gear ratio of the motor
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COUNTS_PER_REV = MMME_CPR * GEAR_RATIO # The counts per revolution of the motor's output shaft
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DIRECTION = NORMAL_DIR # The direction to spin the motor in. NORMAL_DIR (0), REVERSED_DIR (1)
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SPEED_SCALE = 5.4 # The scaling to apply to the motor's speed to match its real-world speed
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UPDATES = 100 # How many times to update the motor per second
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UPDATE_RATE = 1 / UPDATES
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PRINT_WINDOW = 0.25 # The time (in seconds) after a new setpoint, to display print out motor values
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MOVEMENT_WINDOW = 2.0 # The time (in seconds) between each new setpoint being set
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PRINT_DIVIDER = 1 # How many of the updates should be printed (i.e. 2 would be every other update)
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# Multipliers for the different printed values, so they appear nicely on the Thonny plotter
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SPD_PRINT_SCALE = 10 # Driving Speed multipler
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POSITION_EXTENT = 90 # How far from zero to move the motor, in degrees
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# PID values
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POS_KP = 0.14 # Position proportional (P) gain
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POS_KI = 0.0 # Position integral (I) gain
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POS_KD = 0.0022 # Position derivative (D) gain
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# Free up hardware resources ahead of creating a new Encoder
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gc.collect()
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# Create a motor and set its speed scale
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m = Motor(MOTOR_PINS, direction=DIRECTION, speed_scale=SPEED_SCALE, deadzone=0.0)
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# Create an encoder, using PIO 0 and State Machine 0
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enc = Encoder(0, 0, ENCODER_PINS, direction=DIRECTION, counts_per_rev=COUNTS_PER_REV, count_microsteps=True)
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# Create the user button
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user_sw = Button(motor2040.USER_SW)
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# Create PID object for position control
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pos_pid = PID(POS_KP, POS_KI, POS_KD, UPDATE_RATE)
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# Enable the motor to get started
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m.enable()
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# Set the initial setpoint position
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pos_pid.setpoint = POSITION_EXTENT
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update = 0
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print_count = 0
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# Continually move the motor until the user button is pressed
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while user_sw.raw() is not True:
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# Capture the state of the encoder
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capture = enc.capture()
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# Calculate the velocity to move the motor closer to the position setpoint
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vel = pos_pid.calculate(capture.degrees, capture.degrees_per_second)
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# Set the new motor driving speed
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m.speed(vel)
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# Print out the current motor values and their setpoints,
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# but only for the first few updates and only every multiple
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if update < (PRINT_WINDOW * UPDATES) and print_count == 0:
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print("Pos =", capture.degrees, end=", ")
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print("Pos SP =", pos_pid.setpoint, end=", ")
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print("Speed = ", m.speed() * SPD_PRINT_SCALE)
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# Increment the print count, and wrap it
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print_count = (print_count + 1) % PRINT_DIVIDER
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update += 1 # Move along in time
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# Have we reached the end of this time window?
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if update >= (MOVEMENT_WINDOW * UPDATES):
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update = 0 # Reset the counter
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# Set the new position setpoint to be the inverse of the current setpoint
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pos_pid.setpoint = 0.0 - pos_pid.setpoint
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time.sleep(UPDATE_RATE)
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# Disable the servo
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m.disable()
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