external_cmd_converter#
external_cmd_converter is a node that converts desired mechanical input to acceleration and velocity by using accel/brake map.
Algorithm#
How to calculate reference acceleration and velocity#
A reference acceleration and velocity are derived from the throttle and brake values of external control commands.
Reference Acceleration#
A reference acceleration is calculated from accel_brake_map based on values of a desired_pedal and a current velocity;
\[
pedal_d = throttle_d - brake_d,
\]
\[
acc_{ref} = Acc(pedal_d, v_{x,current}).
\]
| Parameter | Description |
|---|---|
| \(throttle_d\) | throttle value of external control command (~/in/external_control_cmd.control.throttle) |
| \(brake_d\) | brake value of external control command (~/in/external_control_cmd.control.brake) |
| \(v_{x,current}\) | current longitudinal velocity (~/in/odometry.twist.twist.linear.x) |
| Acc | accel_brake_map |
Reference Velocity#
A reference velocity is calculated based on a current velocity and a reference acceleration:
\[
v_{ref} =
v_{x,current} + k_{v_{ref}} \cdot \text{sign}_{gear} \cdot acc_{ref}.
\]
| Parameter | Description |
|---|---|
| \(acc_{ref}\) | reference acceleration |
| \(k_{v_{ref}}\) | reference velocity gain |
| \(\text{sign}_{gear}\) | gear command (~/in/shift_cmd) (Drive/Low: 1, Reverse: -1, Other: 0) |
Input topics#
| Name | Type | Description |
|---|---|---|
~/in/external_control_cmd |
tier4_external_api_msgs::msg::ControlCommand | target throttle/brake/steering_angle/steering_angle_velocity is necessary to calculate desired control command. |
~/input/shift_cmd" |
autoware_vehicle_msgs::GearCommand | current command of gear. |
~/input/emergency_stop |
tier4_external_api_msgs::msg::Heartbeat | emergency heart beat for external command. |
~/input/current_gate_mode |
tier4_control_msgs::msg::GateMode | topic for gate mode. |
~/input/odometry |
navigation_msgs::Odometry | twist topic in odometry is used. |
Output topics#
| Name | Type | Description |
|---|---|---|
~/out/control_cmd |
autoware_control_msgs::msg::Control | ackermann control command converted from selected external command |
Parameters#
| Parameter | Type | Description |
|---|---|---|
ref_vel_gain_ |
double | reference velocity gain |
timer_rate |
double | timer's update rate |
wait_for_first_topic |
double | if time out check is done after receiving first topic |
control_command_timeout |
double | time out check for control command |
emergency_stop_timeout |
double | time out check for emergency stop command |
Limitation#
tbd.