autoware_raw_vehicle_cmd_converter

Overview

The raw_vehicle_command_converter is a crucial node in vehicle automation systems, responsible for translating desired steering and acceleration inputs into specific vehicle control commands. This process is achieved through a combination of a lookup table and an optional feedback control system.

Lookup Table

The core of the converter's functionality lies in its use of a CSV-formatted lookup table. This table encapsulates the relationship between the throttle/brake pedal (depending on your vehicle control interface) and the corresponding vehicle acceleration across various speeds. The converter utilizes this data to accurately translate target accelerations into appropriate throttle/brake values.

Creation of Reference Data

Reference data for the lookup table is generated through the following steps:

1. Data Collection: On a flat road, a constant value command (e.g., throttle/brake pedal) is applied to accelerate or decelerate the vehicle.
2. Recording Data: During this phase, both the IMU acceleration and vehicle velocity data are recorded.
3. CSV File Generation: A CSV file is created, detailing the relationship between command values, vehicle speed, and resulting acceleration.

Once the acceleration map is crafted, it should be loaded when the RawVehicleCmdConverter node is launched, with the file path defined in the launch file.

Auto-Calibration Tool

For ease of calibration and adjustments to the lookup table, an auto-calibration tool is available. More information and instructions for this tool can be found here.

Variable Gear Ratio (VGR)

This is a gear ratio for converting tire angle to steering angle. Generally, to improve operability, the gear ratio becomes dynamically larger as the speed increases or the steering angle becomes smaller. For a certain vehicle, data was acquired and the gear ratio was approximated by the following formula.

\[ a + b \times v^2 - c \times \lvert \delta \rvert \]

For that vehicle, the coefficients were as follows.

vgr_coef_a: 15.713
vgr_coef_b: 0.053
vgr_coef_c: 0.042

When convert_steer_cmd_method: "vgr" is selected, the node receives the control command from the controller as the desired tire angle and calculates the desired steering angle to output. Also, when convert_actuation_to_steering_status: true, this node receives the actuation_status topic and calculates the steer tire angle from the steer_wheel_angle and publishes it.

Input topics

Name	Type	Description
~/input/control_cmd	autoware_control_msgs::msg::Control	target velocity/acceleration/steering_angle/steering_angle_velocity is necessary to calculate actuation command.
~/input/steering"	autoware_vehicle_msgs::msg::SteeringReport	subscribe only when convert_actuation_to_steering_status: false. current status of steering used for steering feed back control
~/input/odometry	navigation_msgs::Odometry	twist topic in odometry is used.
~/input/actuation_status	tier4_vehicle_msgs::msg::ActuationStatus	actuation status is assumed to receive the same type of status as sent to the vehicle side. For example, if throttle/brake pedal/steer_wheel_angle is sent, the same type of status is received. In the case of steer_wheel_angle, it is used to calculate steer_tire_angle and VGR in this node.

Output topics

Name	Type	Description
~/output/actuation_cmd	tier4_vehicle_msgs::msg::ActuationCommandStamped	actuation command for vehicle to apply mechanical input
~/output/steering_status	autoware_vehicle_msgs::msg::SteeringReport	publish only when convert_actuation_to_steering_status: true. steer tire angle is calculated from steer wheel angle and published.

Parameters

Name	Type	Description	Default	Range
csv_path_accel_map	string	path for acceleration map csv file	$(find-pkg-share autoware_raw_vehicle_cmd_converter)/data/default/accel_map.csv	N/A
csv_path_brake_map	string	path for brake map csv file	$(find-pkg-share autoware_raw_vehicle_cmd_converter)/data/default/brake_map.csv	N/A
csv_path_steer_map	string	path for steer map csv file	$(find-pkg-share autoware_raw_vehicle_cmd_converter)/data/default/steer_map.csv	N/A
convert_accel_cmd	boolean	use accel or not	true	N/A
convert_brake_cmd	boolean	use brake or not	true	N/A
convert_steer_cmd	boolean	use steer or not	true	N/A
use_steer_ff	boolean	steering steer controller using steer feed forward or not	true	N/A
use_steer_fb	boolean	steering steer controller using steer feed back or not	true	N/A
is_debugging	boolean	debugging mode or not	false	N/A
max_throttle	float	maximum value of throttle	0.4	≥0.0
max_brake	float	maximum value of brake	0.8	≥0.0
max_steer	float	maximum value of steer	10.0	N/A
min_steer	float	minimum value of steer	-10.0	N/A
steer_pid.kp	float	proportional coefficient value in PID control	150.0	N/A
steer_pid.ki	float	integral coefficient value in PID control	15.0	>0.0
steer_pid.kd	float	derivative coefficient value in PID control	0.0	N/A
steer_pid.max	float	maximum value of PID	8.0	N/A
steer_pid.min	float	minimum value of PID	-8.0.	N/A
steer_pid.max_p	float	maximum value of Proportional in PID	8.0	N/A
steer_pid.min_p	float	minimum value of Proportional in PID	-8.0	N/A
steer_pid.max_i	float	maximum value of Integral in PID	8.0	N/A
steer_pid.min_i	float	minimum value of Integral in PID	-8.0	N/A
steer_pid.max_d	float	maximum value of Derivative in PID	0.0	N/A
steer_pid.min_d	float	minimum value of Derivative in PID	0.0	N/A
steer_pid.invalid_integration_decay	float	invalid integration decay value in PID control	0.97	>0.0
convert_steer_cmd_method	string	method for converting steer command	vgr	['vgr', 'steer_map']
vgr_coef_a	float	coefficient a for variable gear ratio	15.713	N/A
vgr_coef_b	float	coefficient b for variable gear ratio	0.053	N/A
vgr_coef_c	float	coefficient c for variable gear ratio	0.042	N/A
convert_actuation_to_steering_status	boolean	convert actuation to steering status or not. Whether to subscribe to actuation_status and calculate and publish steering_status For example, receive the steering wheel angle and calculate the steering wheel angle based on the gear ratio. If false, the vehicle interface must publish steering_status.	true	N/A

Limitation

The current feed back implementation is only applied to steering control.