feat(pid_longitudinal_controller): improve FF gain constant calculation

[brkay54]

Description

In current implementation:

FF Gain Calculation --> min_gain <= current_vel_abs/target_vel_abs <= max_gain

I assume that FF Gain should increase if the velocity error increases. In the current implementation, The gain can decrease if the velocity error increases in the case current_vel_abs < target_vel_abs.

However, a better approach would be:
FF Gain Calculation --> min_gain <= 1.0 + (abs(current_target_vel_abs - current_vel_abs) / std::max(current_target_vel_abs, 0.1)) <= max_gain

It will increase or decrease the FF gain concerning the last velocity error.

Tests performed

Tested in Planning Simulator and worked well.

Effects on system behavior

There is no effect.

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[brkay54]

@TakaHoribe -san It is a very small change. The core idea is FF gain should increase if the velocity error increases. In the current implementation, it might not increase in some cases.

[takayuki5168]

@brkay54
The current implementation is based on #2729
Let me know if you still think this PR will be better than the current one.

[takayuki5168]

@brkay54
Please make this and related PRs draft so that we know that this PR is under the fix.

[stale]

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[stale]

This pull request has been automatically marked as stale because it has not had recent activity.