Setting minimum_turning_radius to 0 for SmacPlannerHybrid causes error

[tonynajjar]

Bug report

Required Info:

• Operating System:
  • Ubuntu 24
• ROS2 Version:
  • Jazzy

Steps to reproduce issue

planner_server:
  ros__parameters:
    expected_planner_frequency: 20.0
    planner_plugins: ["GridBased"]
    GridBased:
      plugin: "nav2_smac_planner::SmacPlannerHybrid"
      tolerance: 0.2
      downsample_costmap: false
      downsampling_factor: 1
      allow_unknown: true
      max_iterations: 1000000
      max_on_approach_iterations: 1000 
      max_planning_time: 1.5 
      motion_model_for_search: "REEDS_SHEPP" 
      angle_quantization_bins: 64 
      analytic_expansion_ratio: 3.5
      minimum_turning_radius: 0.0
      reverse_penalty: 10.0 
      change_penalty: 0.15 
      non_straight_penalty: 1.50
      cost_penalty: 0.1
      lookup_table_size: 10.0
      cache_obstacle_heuristic: False
      debug_visualizations: false
      smoother:
        max_iterations: 1000
        w_smooth: 0.3
        w_data: 0.2
        tolerance: 1.0e-10

Expected behavior

Actual behavior

I get GridBased plugin failed to plan from (10.38, 0.41) to (10.35, -3.65): "Start occupied". when calling ComputePathThroughPoses (although it's really not occupied). Setting it dynamically to e.g. 0.1 fixes the issue

Additional information

---

[SteveMacenski]

That is not a valid configuration, there must be a non-zero value for the minimum turning radius. The motion model requires a turning radius to compute the minimum turning arcs. It does not support point changes, as that would be discontinuous and therefore infeasible kinematically by the motion model's formulation. If you didn't need a feasible planner, you could use Smac 2D, NavFn, or Theta* as potential other options that don't rely on feasibility constraints.

Otherwise, you could also use the State Lattice planner, which can be configured with a minimum control set with in-place rotations that would be virtually allowing stop and rotate maneuvers (in conjunction with some minimum turning radius turning moves as well). That is just with the generator we provide that you can configure easily. If you want something more bespoke, that is part of the value of the State Lattice planner; you can create your own minimum control set / generator and we provide the file format that they're read into the planner to use by. The generator we provide is good for many types of robots and situations, but bespoke situations or 'abnormal' robot configurations would need to create their own

[SteveMacenski]

I just updated the docs to mention that as well

[SteveMacenski]

I think this can be closed?