wimblerobotics name: dwb-controller description: 'Configure Nav2 DWB (Dynamic Window Based) controller. Use when setting velocity samples, forward simulation, or trajectory scoring.'
DWB Controller — Dynamic Window-Based Local Planner
Algorithm Overview
DWB (Dynamic Window approach, B-variant in Nav2) samples discrete velocity commands within the robot's dynamic window — the set of velocities reachable given current velocity and acceleration limits within one control cycle. Each sampled velocity is forward-simulated to produce a trajectory, and all trajectories are scored by critic plugins.
Plugin: dwb_core::DWBLocalPlanner
How It Differs from MPPI
- DWB samples velocities (vx, vy, wz) and simulates forward. MPPI samples trajectory perturbations over the full horizon.
- DWB evaluates each trajectory independently. MPPI uses Boltzmann-weighted averaging.
- DWB is less computationally demanding but produces less-optimal trajectories in complex environments.
- DWB critic evaluation order can matter when
short_circuit_trajectory_evaluation: true.
Key Parameters
Velocity Limits
| Parameter | Type | Description | Example |
|---|---|---|---|
min_vel_x |
float | Minimum forward velocity (negative = reverse allowed) | -0.1 |
max_vel_x |
float | Maximum forward velocity (m/s) | 0.5 |
min_vel_y |
float | Minimum lateral velocity (0 for diff-drive) | 0.0 |
max_vel_y |
float | Maximum lateral velocity (0 for diff-drive) | 0.0 |
max_vel_theta |
float | Maximum angular velocity (rad/s) | 1.0 |
min_speed_xy |
float | Minimum translational speed to be considered moving | 0.0 |
max_speed_xy |
float | Maximum translational speed | 0.5 |
min_speed_theta |
float | Minimum rotational speed | 0.0 |
Acceleration Limits
| Parameter | Type | Description | Example |
|---|---|---|---|
acc_lim_x |
float | Forward acceleration limit (m/s²) | 2.5 |
acc_lim_y |
float | Lateral acceleration (0 for diff-drive) | 0.0 |
acc_lim_theta |
float | Angular acceleration limit (rad/s²) | 3.2 |
decel_lim_x |
float | Deceleration limit (negative, m/s²) | -2.5 |
decel_lim_y |
float | Lateral deceleration | 0.0 |
decel_lim_theta |
float | Angular deceleration (negative) | -3.2 |
Trajectory Generation
| Parameter | Type | Description | Typical |
|---|---|---|---|
sim_time |
float | Forward simulation time (seconds) | 1.7 |
vx_samples |
int | Number of linear velocity samples | 20 |
vy_samples |
int | Number of lateral velocity samples (1 for diff-drive) | 1 |
vtheta_samples |
int | Number of angular velocity samples | 20 |
transform_tolerance |
float | TF tolerance (seconds) | 0.1 |
short_circuit_trajectory_evaluation |
bool | Stop scoring a trajectory once it's clearly worse than best so far | true |
Total trajectory count = vx_samples × vy_samples × vtheta_samples. For 20×1×20 = 400 trajectories. More samples = better coverage of velocity space but more CPU. DWB typically evaluates 200–600 trajectories per cycle.
Trajectory Generators
The default generator is dwb_plugins::StandardTrajectoryGenerator. Alternative: dwb_plugins::LimitedAccelGenerator which strictly enforces acceleration constraints on samples.
trajectory_generator_name: "dwb_plugins::StandardTrajectoryGenerator"
Critics
Critics are specified as a list. Each critic scores all evaluated trajectories. The order matters when short_circuit_trajectory_evaluation: true — place collision-checking critics first to reject infeasible trajectories early.
critics: ["RotateToGoal", "Oscillation", "BaseObstacle", "GoalAlign", "PathAlign", "PathDist", "GoalDist"]
See dwb_critics.md for details on each critic plugin.
Complete YAML for Differential Drive
controller_server:
ros__parameters:
controller_frequency: 20.0
min_x_velocity_threshold: 0.001
min_y_velocity_threshold: 0.0
min_theta_velocity_threshold: 0.001
FollowPath:
plugin: "dwb_core::DWBLocalPlanner"
debug_trajectory_details: true
# Velocity limits
min_vel_x: 0.0
max_vel_x: 0.5
min_vel_y: 0.0
max_vel_y: 0.0
max_vel_theta: 1.0
min_speed_xy: 0.0
max_speed_xy: 0.5
min_speed_theta: 0.0
# Acceleration limits
acc_lim_x: 2.5
acc_lim_y: 0.0
acc_lim_theta: 3.2
decel_lim_x: -2.5
decel_lim_y: 0.0
decel_lim_theta: -3.2
# Trajectory generation
sim_time: 1.7
vx_samples: 20
vy_samples: 1
vtheta_samples: 20
transform_tolerance: 0.1
short_circuit_trajectory_evaluation: true
# Trajectory generator
trajectory_generator_name: "dwb_plugins::StandardTrajectoryGenerator"
# Critics
critics:
- "RotateToGoal"
- "Oscillation"
- "BaseObstacle"
- "GoalAlign"
- "PathAlign"
- "PathDist"
- "GoalDist"
BaseObstacle:
scale: 0.02
sum_scores: false
PathDist:
scale: 32.0
GoalDist:
scale: 24.0
PathAlign:
scale: 32.0
forward_point_distance: 0.325
GoalAlign:
scale: 24.0
forward_point_distance: 0.325
RotateToGoal:
scale: 32.0
slowing_factor: 5.0
lookahead_time: -1.0
Oscillation:
scale: 1.0
Tuning Tips
- Robot wobbles/oscillates: Increase
Oscillationscale, reducevtheta_samples, or loweracc_lim_theta. - Robot clips corners: Increase
PathDistscale orPathAlignscale. - Robot won't enter narrow spaces: Reduce
BaseObstaclescale; check inflation radius. - Robot is sluggish: Increase
vx_samples, increasemax_vel_x, or reducesim_time(shorter lookahead can be more agile). - CPU too high: Reduce
vx_samples × vtheta_samples, enableshort_circuit_trajectory_evaluation.
When to Use DWB
- Middle ground between MPPI (heavy, optimal) and RPP (light, simple).
- Good for environments that are moderately complex.
- Familiar to users of the ROS1
dwa_local_planner. - Easier to reason about than MPPI because trajectories correspond to single velocity commands.