Apollo: Lat controller and Lon controller sequence

[wckorealsh]

Hi Apollo team,

How do these two controllers running in time, i.e. sequentially or in parallel?
If I want to run Longitudinal controller before the Lateral controller, how do I specify the sequence?
Thank you!

[Capri2014]

@wckorealsh you can change it via modifying the controller order in https://github.com/ApolloAuto/apollo/blob/master/modules/control/conf/lincoln.pb.txt

[wckorealsh]

Thanks @Capri2014, Does this mean that the one comes first in the config file actually runs first?

[jilinzhou]

The lateral controller controls the steering while the longitudinal controller controls throttle and braking. In fully auto mode, both commands are sent to canbus. In AUTO_STEER_ONLY mode, only steering cmd is sent to canbus. On the other hand, if in AUTO_SPEED_ONLY mode, only throttle and braking cmds are pushed to canbus.

Here is related code snippet:

  if (driving_mode_ == Chassis::COMPLETE_AUTO_DRIVE ||
      driving_mode_ == Chassis::AUTO_SPEED_ONLY) {
    Gear(control_command.gear_location());
    Throttle(control_command.throttle());
    Brake(control_command.brake());
    SetEpbBreak(control_command);
  }

  if (driving_mode_ == Chassis::COMPLETE_AUTO_DRIVE ||
      driving_mode_ == Chassis::AUTO_STEER_ONLY) {
    const double steering_rate_threshold = 1.0;
    if (control_command.steering_rate() > steering_rate_threshold) {
      Steer(control_command.steering_target(), control_command.steering_rate());
    } else {
      Steer(control_command.steering_target());
    }
  }

[wckorealsh]

@jilinzhou I understand both commands are sent to canbus. My question is if they are running sequentially or not i.e. two processes (A,B) are running in order: A->B->A->B->A->B.....

[Capri2014]

@wckorealsh yes the it is running sequentially, but not two "processes", but two "controllers".