Coupled linear/angular reversals violate acceleration limits despite `preserve_turning_radius`

[147258369ymc]

Robot Model

Turtlebot4 Standard

ROS distro

Jazzy

Networking Configuration

Simple Discovery

OS

Ubuntu 24.04

Built from source or installed?

Installed

Package version

ros-jazzy-turtlebot4-simulator: 2.0.2-1noble.20260616.091643
ros-jazzy-turtlebot4-gz-bringup: 2.0.2-1noble.20260616.085653
ros-jazzy-irobot-create-control: 3.0.4-1noble.20260616.082318
ros-jazzy-irobot-create-gz-bringup: 3.0.4-1noble.20260616.083553
ros-jazzy-irobot-create-nodes: 3.0.4-1noble.20260615.161556
ros-jazzy-ros-gz: 1.0.22-1noble.20260616.074726
Gazebo: Harmonic / gz

Expected behaviour

When `linear.x` and `angular.z` change together, TurtleBot4/Create3 simulation should preserve turning-radius semantics while still respecting acceleration limits:

```yaml
preserve_turning_radius: true
linear.x.max_acceleration: 0.9
angular.z.max_acceleration: 7.725

If both constraints cannot be satisfied while preserving turning radius exactly, the safer behavior is to slow/ramp the command rather than exceed acceleration limits.

### Actual behaviour

```markdown
Coupled linear/angular reversals repeatedly violate both linear and angular acceleration envelopes.

The strongest repeated trigger in a previous 1000-round campaign was:

```text
(+0.130,+0.450)x4 -> (-0.130,-0.450)x4

It appeared in 156 error rows. After schedule de-duplication, it still appeared 17 times in the latest run.

Representative latest-run frame 1782637031.1374679:

TB4 linear acceleration envelope violated:
  accel = 2.462 m/s^2
  ratio = 2.74x
  limit = 0.900 m/s^2

TB4 angular acceleration envelope violated:
  accel = 14.843 rad/s^2
  ratio = 1.92x
  limit = [-7.725, 7.725] rad/s^2

Supporting /diffdrive_controller/cmd_vel ratios:
  linear = 6.87x
  angular = 3.52x

Latest run aggregate:

• combined acceleration with command-path support: 429
• combined odom-only acceleration: 3

### Error messages

```bash
TB4 linear acceleration envelope violated: accel=2.462 m/s^2 ratio=2.74 limit=0.900
TB4 angular acceleration envelope violated: accel=14.843 rad/s^2 ratio=1.92 limit=[-7.725, 7.725]

To Reproduce

1. Start TurtleBot4 Standard simulation on ROS 2 Jazzy.
2. Record `/cmd_vel`, `/diffdrive_controller/cmd_vel`, `/odom`, `/wheel_vels`, and `/clock`.
3. Publish a coupled reversal sequence:

```text
(+0.130,+0.450)x4 -> (-0.130,-0.450)x4

or:

(+0.100,-0.500)x8

4. Compute adjacent-sample acceleration for both linear.x and angular.z.
5. Observe both channels exceeding configured acceleration limits.

### Other notes

```markdown
This case is not just a duplicate of pure linear or pure angular motion. It stresses:

- `preserve_turning_radius: true`
- simultaneous linear and angular acceleration limiting
- Cartesian-to-wheel command conversion
- wheel differential response under turning reversal

Please include coupled reversal cases in any regression tests for acceleration limiting.