Documentation Index
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Actuator parts control motors and servos to translate pilot commands into physical motion.
PWM Controllers
PulseController
Generic PWM pulse controller using pin providers.
Constructor:
PulseController(pwm_pin, pwm_scale=1.0, pwm_inverted=False)
PWM pin provider (see donkeycar.parts.pins)
Scaling factor for 12-bit pulse values to compensate for non-standard PWM frequencies
Set PWM pulse width using 12-bit value (0-4095)
Donkeycar part interface - sets pulse width
from donkeycar.parts.pins import PCA9685PwmPin
from donkeycar.parts.actuator import PulseController
# Create PWM pin
pwm_pin = PCA9685PwmPin(channel=1, frequency=60)
# Create pulse controller
controller = PulseController(pwm_pin)
# Set pulse
controller.set_pulse(370) # neutral position
PCA9685 (Deprecated)
Legacy PCA9685 PWM controller. Use PulseController instead.
Constructor:
PCA9685(channel, address=0x40, frequency=60, busnum=None, init_delay=0.1)
Steering Controllers
PWMSteering
Converts steering angles to PWM pulses.
Constructor:
PWMSteering(controller, left_pulse, right_pulse)
Pulse controller with set_pulse() method
PWM pulse for full left steering
PWM pulse for full right steering
Convert angle (-1 to 1) to PWM pulse and apply
Set pulse for threaded operation
from donkeycar.parts.actuator import PWMSteering, PulseController
steering_controller = PulseController(pwm_pin)
steering = PWMSteering(controller=steering_controller,
left_pulse=cfg.STEERING_LEFT_PWM,
right_pulse=cfg.STEERING_RIGHT_PWM)
V.add(steering, inputs=['pilot/angle'])
Throttle Controllers
PWMThrottle
Converts throttle values to PWM pulses for ESC control.
Constructor:
PWMThrottle(controller, max_pulse, min_pulse, zero_pulse)
Pulse controller with set_pulse() method
PWM pulse for full forward throttle
PWM pulse for full reverse throttle
PWM pulse for stopped/neutral
run
(throttle: float) -> None
Convert throttle (-1 to 1) to PWM pulse and apply
run_threaded
(throttle: float) -> None
Set pulse for threaded operation
Stop throttle and release
from donkeycar.parts.actuator import PWMThrottle, PulseController
throttle_controller = PulseController(pwm_pin)
throttle = PWMThrottle(controller=throttle_controller,
max_pulse=cfg.THROTTLE_FORWARD_PWM,
min_pulse=cfg.THROTTLE_REVERSE_PWM,
zero_pulse=cfg.THROTTLE_STOPPED_PWM)
V.add(throttle, inputs=['pilot/throttle'])
Differential Drive
TwoWheelSteeringThrottle
Converts steering and throttle to individual wheel motor speeds.
Methods:
run
(throttle: float, steering: float) -> (float, float)
Returns (left_motor_speed, right_motor_speed) tuple
from donkeycar.parts.actuator import TwoWheelSteeringThrottle
mixer = TwoWheelSteeringThrottle()
V.add(mixer,
inputs=['pilot/throttle', 'pilot/angle'],
outputs=['left_motor_speed', 'right_motor_speed'])
L298N_HBridge_3pin
DC motor controller using L298N H-bridge with 3-pin configuration.
Constructor:
L298N_HBridge_3pin(pin_forward, pin_backward, pwm_pin, zero_throttle=0, max_duty=0.9)
GPIO pin for forward direction
GPIO pin for backward direction
PWM pin for motor speed control
Throttle deadzone threshold
Maximum duty cycle (0 to 1)
run
(throttle: float) -> None
Set motor speed and direction from throttle (-1 to 1)
L298N_HBridge_2pin
DC motor controller using L298N H-bridge with 2-pin PWM configuration.
Constructor:
L298N_HBridge_2pin(pin_forward, pin_backward, zero_throttle=0, max_duty=0.9)
PWM pin for forward control
PWM pin for backward control
Throttle deadzone threshold
Maximum duty cycle (0 to 1)
run
(throttle: float) -> None
Set motor speed and direction from throttle (-1 to 1)
Specialized Controllers
VESC
VESC motor controller for electric skateboards.
Constructor:
VESC(serial_port, percent=0.2, has_sensor=False, start_heartbeat=True,
baudrate=115200, timeout=0.05, steering_scale=1.0, steering_offset=0.0)
Serial port path (e.g., /dev/ttyACM1)
Maximum duty cycle percentage (-1 to 1)
Steering servo scaling factor
pip install git+https://github.com/LiamBindle/PyVESC.git@master
run
(angle: float, throttle: float) -> None
Set servo angle and motor duty cycle
Configuration
Typical actuator configuration in myconfig.py:
# PWM Configuration
STEERING_CHANNEL = 1
STEERING_LEFT_PWM = 460
STEERING_RIGHT_PWM = 290
THROTTLE_CHANNEL = 0
THROTTLE_FORWARD_PWM = 500
THROTTLE_STOPPED_PWM = 370
THROTTLE_REVERSE_PWM = 220
# PCA9685
PCA9685_I2C_ADDR = 0x40
PCA9685_I2C_BUSNUM = 1
Integration Example
From templates like complete.py:
from donkeycar.parts.actuator import PulseController, PWMSteering, PWMThrottle
from donkeycar.parts.pins import PCA9685PwmPin
# Create PWM pins
steering_pin = PCA9685PwmPin(channel=cfg.STEERING_CHANNEL, frequency=60)
throttle_pin = PCA9685PwmPin(channel=cfg.THROTTLE_CHANNEL, frequency=60)
# Create controllers
steering_controller = PulseController(steering_pin)
throttle_controller = PulseController(throttle_pin)
# Create steering and throttle parts
steering = PWMSteering(controller=steering_controller,
left_pulse=cfg.STEERING_LEFT_PWM,
right_pulse=cfg.STEERING_RIGHT_PWM)
throttle = PWMThrottle(controller=throttle_controller,
max_pulse=cfg.THROTTLE_FORWARD_PWM,
min_pulse=cfg.THROTTLE_REVERSE_PWM,
zero_pulse=cfg.THROTTLE_STOPPED_PWM)
V.add(steering, inputs=['pilot/angle'])
V.add(throttle, inputs=['pilot/throttle'])
