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The reliable way to test a rover that must navigate and avoid obstacles is to debug the complete navigation pipeline in layers: verify sensor data and time stamps, confirm the map–odom–base_link transform chain, validate odometry and localization, inspect maps and costmaps, then separate path-planning faults from controller and actuator faults. After those checks pass in a repeatable simulation scenario, repeat the same cases on the physical rover under supervision. Lidar is not mandatory; Nav2 can use vision, depth, or other correctly integrated collision-avoidance sensors.
What you are actually testing
Navigation is not one algorithm. It is a chain of time-dependent components that turns a goal pose into safe wheel motion:
- Perception: lidar, depth, cameras, bump sensors, or another source produces observations.
- State estimation: wheel encoders, inertial data, visual estimates, or other sources estimate motion.
- Transforms: TF2 relates the map, odometry, robot body, and sensor frames.
- Environmental representation: a static map and local or global costmaps represent free, occupied, and restricted space.
- Localization: the rover estimates where it is in the map.
- Planning: a planner creates a route or path to the goal.
- Control: a controller converts the path into velocity commands.
- Actuation and recovery: the base executes commands, stops when necessary, and the behavior tree chooses replanning or recovery actions.
Nav2 describes behavior trees as the coordinator for planning, control, and recovery, while state estimation, transformations, and costmaps provide the information those behaviors need. A failure at an earlier stage can look like a planner or obstacle-avoidance failure later, so changing planner parameters first is often the wrong diagnosis.
Establish a reproducible baseline
Before changing a parameter, record the exact configuration that produced the problem. Create one baseline record for every test run:
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- Rover model, wheelbase, track width, wheel radius, mass, and the physical footprint used by the navigation stack.
- ROS 2 distribution, Nav2 branch or release, simulator version, and operating-system image.
- Sensor models, mounting positions, driver packages, configured topics, frame IDs, and update rates.
- Map file, map resolution, localization configuration, planner and controller plugins, costmap settings, velocity limits, and goal tolerances.
- Launch files, parameter files, environment variables, and the date and time of the run.
- Test surface, battery state, payload, lighting, and whether the run was simulated or physical.
The current Nav2 first-time setup documentation uses Gazebo Harmonic or newer with ROS 2 Jazzy or newer for its examples. That is version context, not a universal requirement. If your rover uses another ROS 2 distribution, simulator, or Nav2 branch, use the matching documentation and record the differences rather than assuming parameter names or defaults are identical.
Verify the robot description, frames, and timing first
Many apparent navigation failures are transform failures. Nav2’s minimum frame chain is:
map → odom → base_link → sensor frames
The names can be changed by configuration, but the relationships must be coherent. The map-to-odometry transform describes global localization; odometry-to-base describes local motion; each sensor transform places measurements on the robot.
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- Confirm that the URDF or equivalent robot description puts every sensor at its real height, angle, and lateral offset.
- Measure the rover’s outer dimensions, including attachments that can hit an obstacle, and ensure the configured footprint or robot radius covers them.
- Check wheel radius, wheel separation, encoder signs, and joint axes against the physical rover.
- Ensure the collision geometry used by simulation is not smaller than the physical body.
Inspect the TF tree
Use the ROS 2 command-line tools while the complete stack is running. For example:
ros2 run tf2_tools view_frames
ros2 run tf2_ros tf2_echo odom base_link
ros2 run tf2_ros tf2_echo base_link laser_frameThe exact sensor frame may be camera_link, depth_frame, imu_link, or another configured name. A missing edge, an unexpected parent, a reversed axis, or a transform that is several seconds old can invalidate an otherwise good plan.
Check message frame IDs and timestamps
Inspect representative messages:
ros2 topic list
ros2 topic echo /scan --once
ros2 topic echo /odom --once
ros2 topic hz /scan
ros2 topic hz /odomReplace topic names with those used by your rover. Confirm that each message’s header.frame_id is the frame whose transform you inspected, that timestamps use the same clock source as the rest of the system, and that data arrives often enough for the rover’s speed. A sensor that publishes valid-looking ranges with a stale timestamp can be placed in the wrong location when the rover is moving.
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Project-specific map and transform example
One documented Rover Robotics workflow obtains base_link → odom from robot localization and odom → map from Slam Toolbox. That assignment is specific to that project, not a universal Nav2 rule. The same project’s Nav2 map configuration expects an absolute map path without a file extension and the map-related files saved by Slam Toolbox. If you follow that workflow, verify those path and file conventions exactly; do not apply them automatically to a different rover.
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Validate sensors, odometry, and localization independently
Sensor sanity checks
Visualize the live sensor data together with the robot model and map in RViz. A wall that is physically straight should not appear to bend, duplicate, or move with the robot. Check these common causes of shifted or missing obstacles:
- Incorrect sensor mounting transform or a sensor installed differently from the URDF.
- Wrong message frame ID or a frame name that differs only by spelling or namespace.
- Clock mismatch, delayed transport, or simulated time enabled in only part of the system.
- Minimum and maximum range filters that discard nearby or distant obstacles.
- Point-cloud projection or scan angle settings that remove the sector in front of the rover.
- A footprint or inflation radius that is smaller than the real rover.
Do not tune obstacle-inflation distances until the raw observation is in the correct place. Inflation can make a correctly placed obstacle safer; it cannot repair a wrong transform.
Odometry direction and scale
Lift the drive wheels or use a safe stand, then command a small forward and reverse movement. The odometry pose should change in the expected direction and by a plausible amount. Repeat with a slow in-place rotation and compare the sign and approximate angle. On the floor, mark a short distance and compare commanded travel with measured travel. A scale error in wheel radius or wheel separation produces localization drift and causes the controller to appear unstable even when its gains are reasonable.
Localization behavior
With the rover stationary, localization should not jump between distant poses. During a slow loop, it should follow the rover without unexplained discontinuities. Compare the estimated pose, odometry trail, scan or depth data, and map in RViz. If the estimate jumps, investigate frame ownership, map alignment, sensor timing, and ambiguous geometry before changing planner settings.
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Separate planning faults from control faults
Use a clear, simple environment and a reachable goal before testing complex avoidance. Observe both the planned path and the rover’s actual motion.
| Observed behavior | First checks | Why this order helps |
|---|---|---|
| No path or no plan is published | Goal frame and pose, map and costmap topics, transform availability, planner plugin, lethal or unknown cells around the start and goal | The controller cannot follow a path that was never produced. |
| Path exists but crosses a visible obstacle | Sensor frame, timestamps, obstacle-layer source, range limits, footprint, costmap update rate | The planner may be operating on an incomplete environmental representation. |
| Path is reasonable but the rover oscillates | Odometry scale, controller configuration, velocity limits, footprint, command latency, wheel-slip behavior | Oscillation is often an execution or state-estimation problem rather than a global-planning problem. |
| Rover stops short of the goal | Goal tolerance, localization error, controller progress checks, final orientation requirement | A valid path can still fail its configured completion condition. |
| Rover reaches the area but turns incorrectly | Yaw convention, base frame orientation, odometry rotation sign, final-heading tolerance | A frame-axis error can produce a consistent heading error. |
| Rover repeatedly reports “stuck” | Local costmap freshness, obstacle inflation, progress checker, wheel commands, motor limits, recovery behavior | The recovery trigger may be correct even though the underlying cause is mechanical or perceptual. |
This division reflects Nav2’s separation of planners, controllers, environmental representation, and execution. A symptom can have more than one cause, so confirm it with logs and visualization rather than treating the table as a one-to-one diagnosis.
Run a layered test plan
Nav2 system tests illustrate three useful levels: component, subsystem, and full-system integration. Use the same progression on a rover so that a failure has a small search area.
1. Component tests
- Publish a known sensor message and verify that the driver produces the expected frame, timestamp, and range or depth values.
- Send wheel commands on a stand and verify encoder direction, odometry sign, and stop behavior.
- Broadcast or inspect each static and dynamic transform.
- Load a map and verify its resolution, origin, occupancy values, and coordinate orientation.
- Start and stop lifecycle-managed nodes and confirm that they reach the intended states.
2. Subsystem tests
- Run localization with the rover stationary and then moving slowly while checking pose continuity.
- Run the local costmap with a single known obstacle and confirm that the obstacle appears at the measured location.
- Run a planner in a simple map and verify that a path is produced around a static obstacle.
- Run the controller against a generated path without introducing new obstacles.
- Exercise recovery actions in a deliberately blocked, supervised setup.
3. Full-system tests
Nav2’s documented examples include pose navigation, waypoint following, generated path planning, lifecycle transitions, and keepout or speed-restricted zones. Adapt those patterns to your rover. A full-system test should start from the same launch configuration used in operation, accept a goal or waypoint sequence, update localization and costmaps, plan, control the base, and report a clear success or recovery result.
Use repeatable obstacle-avoidance scenarios
Build a small course whose geometry can be measured and reset. Run each scenario multiple times with the same initial pose before changing one parameter.
Empty route
Place the rover in a clear area and command a short goal. Confirm that it publishes a path, accelerates within configured limits, follows the path without oscillation, stops inside the goal tolerance, and reports success. This establishes a control and localization baseline without obstacle decisions.
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Static obstacle blocking the direct route
Place a box or barrier between the start and goal. Confirm that the obstacle appears in the appropriate costmap, the global or local path changes, and the rover maintains clearance while passing. If the direct path remains unchanged, inspect perception and costmap integration before planner tuning.
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Use a passage whose width is known relative to the configured footprint and inflation radius. The rover should enter only when the represented free space is wide enough. If it refuses a physically safe passage, compare the actual width, footprint, inflation, and map resolution. If it attempts a passage that is too narrow, treat that as a safety failure rather than simply reducing inflation.
Unroutable blockage
Block every route to the goal. A safe system should stop, declare that no valid route is available, or execute a configured recovery behavior; it should not force its way through an occupied region. Record whether velocity commands go to zero, how long that takes, and whether the recovery behavior eventually returns the system to a safe state.
Obstacle introduced during motion
If the rover and sensor are designed for dynamic obstacles, introduce an object from a safe distance while the rover is moving slowly. Verify that the local representation updates, the controller brakes or replans, and the rover keeps the required clearance. Nav2 requirements include avoiding moving objects that intercept the path, but the requirement itself is not proof that a particular implementation meets it. Define your own acceptance limits for speed, stopping distance, clearance, and detection latency.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Simulation first, physical rover second
Gazebo and RViz provide a repeatable way to exercise launch files, transforms, maps, planners, controllers, lifecycle transitions, and obstacle scenarios. Simulation is especially useful when you need the same initial pose, obstacle geometry, and goal on every run.
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Simulation does not establish that the physical rover will behave identically. Real wheels slip, motors saturate, sensors have blind spots and latency, floors are uneven, and cable or compute load can change timing. After a simulated case passes, repeat the important cases on the physical rover in a controlled area with a human ready to stop power or issue an emergency stop.
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- Run the empty-route and blocked-route cases in simulation.
- Save the launch configuration, maps, goals, obstacle geometry, and logs.
- Repeat at low speed on the physical rover with a clear emergency-stop procedure.
- Increase speed, payload, and environmental complexity one variable at a time.
- Keep separate pass/fail records for simulated and physical runs; do not merge them into one performance claim.
Choose a sensor approach deliberately
| Approach | Useful strengths | Integration checks | Limits to test |
|---|---|---|---|
| Lidar | Direct range measurements for mapping and obstacle layers | Driver compatibility with the ROS 2 distribution, scan frame, angular coverage, range limits, mounting height, and update timing | Transparent, highly reflective, very low, or out-of-plane objects; mounting occlusion |
| Depth camera | Depth plus imagery and a potentially wide field of view | Depth frame, point-cloud or scan conversion, valid-depth rate, synchronization, and processing load | Lighting, sunlight, reflective surfaces, minimum range, and missing depth |
| Vision-based positioning or avoidance | Can provide localization or scene information without a lidar | Camera calibration, frame transforms, time synchronization, feature availability, and algorithm health reporting | Textureless scenes, lighting changes, motion blur, and occlusion |
| Other collision sensors | Simple close-range protection or a supplement to a primary sensor | Message semantics, placement, fail-safe behavior, and how readings enter the costmap or safety controller | Limited range, sparse coverage, and inability to describe a complete route alone |
Nav2 does not require lidar. Select a sensor according to the rover’s environment and required behavior, then prove that its driver, frame, timing, and obstacle-layer integration work under those conditions. A two-dimensional lidar is one possible hardware category, not a prerequisite or a universal recommendation.
Define acceptance criteria instead of copying a universal benchmark
The cited Nav2 documentation and test examples do not provide a universal rover success rate, localization accuracy, stopping distance, or obstacle-clearance threshold. Set criteria for the specific platform and operating area. A useful test record includes:
- Goal position and orientation, initial pose, route length, and obstacle layout.
- Whether a valid path was produced and whether it stayed inside allowed space.
- Final position and heading error, measured with a stated method.
- Minimum obstacle clearance and whether any obstacle entered the footprint or safety zone.
- Time to detect a new obstacle, time to stop, and peak speed during the test.
- Number and type of replans, recoveries, oscillations, controller timeouts, and dropped sensor messages.
- Battery state, payload, floor, lighting, weather if outdoors, and operator interventions.
For safety-critical operation, define a hard stop condition that is independent of the navigation planner. Test loss of sensor data, stale transforms, localization loss, communications interruption, and an emergency-stop command. The safe result is a controlled stop or a separately designed fail-safe response, not an assumption that Nav2 will infer every hardware fault.
Debug with logs and one-variable changes
Record rosbag data for the relevant sensor, odometry, TF, map, costmap, planned path, velocity command, goal, and diagnostic topics. Capture the exact parameter files and node logs with each run. Replay a failing run when possible so that you can inspect the same input repeatedly instead of trying to reproduce a moving obstacle by memory.
Change one category at a time:
- Correct frame names, parent-child relationships, and timestamps.
- Correct sensor ranges, topic wiring, and costmap observation sources.
- Correct robot dimensions, footprint, and collision geometry.
- Correct odometry scale, signs, and localization configuration.
- Only then tune planner, controller, inflation, velocity, and recovery parameters.
After every change, rerun the baseline empty route and at least one blocked-route case. A parameter that makes one scene look better but causes the baseline to fail is not a fix; it is a trade-off that needs an explicit decision.
Safety checklist for physical trials
- Use a test area free of people, pets, loose cables, stairs, and unprotected drop-offs.
- Keep a reachable emergency stop and a person with authority to cut motor power.
- Start with low speed and conservative acceleration and deceleration limits.
- Use physical barriers or a tether where appropriate, and never stand in the expected path.
- Verify that a lost command stream, stale sensor stream, or localization failure produces a safe response.
- Do not treat a simulator pass, a green lifecycle state, or a successful goal message as proof of physical safety.
- Stop immediately when the rover’s pose, obstacle display, or command response disagrees with reality.
A concise fault-isolation decision path
- Does every required node start and remain active? If not, fix lifecycle, parameters, topic names, or dependencies before navigation testing.
- Is the transform chain complete and current? If not, repair TF ownership, frame IDs, timestamps, or clock configuration.
- Do raw sensors and odometry describe reality? If not, fix drivers, calibration, mounting, encoder signs, or scale.
- Does localization remain stable? If not, resolve map alignment, sensor quality, timing, and estimator configuration.
- Do costmaps show obstacles where they physically are? If not, inspect observation sources, filters, footprint, and update timing.
- Can a planner produce a valid route in a clear map? If not, inspect map validity, goal reachability, planner configuration, and lethal cells.
- Can the controller follow that route? If not, inspect odometry, command latency, velocity limits, wheel behavior, and controller settings.
- Does a newly blocked route stop or recover safely? If not, test local costmap updates, progress checks, recovery behavior, and the independent safety stop.
This order prevents a misleading cycle in which planner and controller parameters are repeatedly changed to compensate for a bad transform, stale sensor data, or incorrect footprint.
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