Setting navigation goals in ROS - Performance & Optimization

Performance: Setting navigation goals

MEDIUM IMPACT

Setting navigation goals affects how quickly and smoothly a robot can plan and execute movement, impacting responsiveness and real-time interaction.

Sending navigation goals to a robot for path planning

ROS

goal = PoseStamped()
goal.header.frame_id = 'map'
goal.pose.position.x = 10
goal.pose.position.y = 10
move_base_client.send_goal(goal)
move_base_client.wait_for_result()

Sends a single goal and waits for the result before sending another, reducing unnecessary planning.

📈 Performance GainSingle planning cycle per goal, reducing CPU load and improving responsiveness

Sending navigation goals to a robot for path planning

ROS

goal = PoseStamped()
goal.header.frame_id = 'map'
goal.pose.position.x = 10
goal.pose.position.y = 10
# Sending goal repeatedly in a tight loop without checking status
while True:
    move_base_client.send_goal(goal)

Continuously sending goals without waiting for completion causes excessive planning requests and CPU load.

📉 Performance CostTriggers repeated planning cycles causing high CPU usage and delayed response

Performance Comparison

Pattern	Planning Requests	CPU Load	Responsiveness	Verdict
Repeated goal sending in loop	Many redundant requests	High CPU usage	Low responsiveness due to overload	[X] Bad
Single goal send with wait	One request per goal	Low CPU usage	High responsiveness	[OK] Good

Rendering Pipeline

Setting navigation goals triggers the robot's path planning and motion control pipeline, involving goal processing, path calculation, and actuator commands.

→Goal Processing

→Path Planning

→Motion Execution

⚠️ BottleneckPath Planning stage is most expensive due to complex calculations.

Core Web Vital Affected

INP

Setting navigation goals affects how quickly and smoothly a robot can plan and execute movement, impacting responsiveness and real-time interaction.

Optimization Tips

1Send navigation goals only when needed, not repeatedly in a loop.

2Wait for the current goal to complete before sending a new one.

3Monitor goal message frequency to avoid overloading the planner.

Performance Quiz - 3 Questions

What is the main performance issue when sending navigation goals in a tight loop without waiting?

A Robot moves faster than expected

B Excessive CPU load due to repeated planning

C Goals are ignored by the robot

D Memory leaks in the navigation stack

DevTools: rostopic echo /move_base/status and rostopic hz /move_base/goal

How to check: Monitor the frequency of goal messages and status updates to ensure goals are not sent too frequently.

What to look for: Look for excessive goal message frequency indicating redundant planning requests.

Practice

1. What is the main purpose of setting a navigation goal in ROS?

easy

A. To tell the robot where to move using coordinates and orientation

B. To change the robot's color

C. To update the robot's software version

D. To stop the robot immediately

Solution

1. Step 1: Understand navigation goals

   Navigation goals specify a target position and orientation for the robot to reach.

2. Step 2: Identify the purpose

   Setting a navigation goal directs the robot where to move in its environment.

3. Final Answer:

   To tell the robot where to move using coordinates and orientation -> Option A

4. Quick Check:

   Navigation goal = target position [OK]

Hint: Navigation goals set robot's target position and direction [OK]

Common Mistakes:

• Confusing navigation goals with software updates
• Thinking navigation goals change robot appearance
• Assuming navigation goals stop the robot

2. Which ROS frame is commonly used to set navigation goals relative to the environment?

easy

A. "base_link" frame

B. "odom" frame

C. "map" frame

D. "camera" frame

Solution

1. Step 1: Identify common frames in ROS navigation

   Frames like "base_link", "odom", and "map" represent different coordinate systems.

2. Step 2: Choose the frame for environment-relative goals

   The "map" frame is fixed to the environment and used for global navigation goals.

3. Final Answer:

   "map" frame -> Option C

4. Quick Check:

   Environment-relative goals use "map" frame [OK]

Hint: "map" frame is fixed to environment, perfect for goals [OK]

Common Mistakes:

• Using "base_link" which is robot-centered
• Choosing "odom" which drifts over time
• Selecting "camera" which is unrelated to navigation

3. Given this ROS Python snippet to send a navigation goal:

goal.target_pose.header.frame_id = "map"
goal.target_pose.pose.position.x = 2.0
goal.target_pose.pose.position.y = 3.0
goal.target_pose.pose.orientation.w = 1.0
client.send_goal(goal)
client.wait_for_result()

What will the robot do?

medium

A. Throw an error due to missing orientation x, y, z

B. Move to position (3.0, 2.0) on the map facing backward

C. Stay still because orientation is incomplete

D. Move to position (2.0, 3.0) on the map facing forward

Solution

1. Step 1: Analyze position and orientation values

   Position is set to x=2.0, y=3.0; orientation.w=1.0 means no rotation (facing forward).

2. Step 2: Understand client commands

   Sending goal and waiting for result commands the robot to move to the specified pose.

3. Final Answer:

   Move to position (2.0, 3.0) on the map facing forward -> Option D

4. Quick Check:

   Goal pose = (2.0,3.0), orientation forward [OK]

Hint: Orientation w=1 means facing forward, position sets location [OK]

Common Mistakes:

• Mixing up x and y coordinates
• Assuming missing orientation x,y,z causes error
• Thinking orientation.w=1 means backward

4. What is wrong with this ROS Python code snippet for setting a navigation goal?

goal.target_pose.header.frame_id = "map"
goal.target_pose.pose.position.x = 1.0
goal.target_pose.pose.position.y = 2.0
client.send_goal(goal)
client.wait_for_result()

medium

A. frame_id should be "odom" instead of "map"

B. Missing orientation in goal.pose causes navigation failure

C. Position values must be integers, not floats

D. client.wait_for_result() must come before send_goal()

Solution

1. Step 1: Check completeness of goal pose

   Orientation is not set, which is required for a valid navigation goal.

2. Step 2: Verify other parts

   frame_id "map" is correct; position floats are allowed; wait_for_result() must follow send_goal().

3. Final Answer:

   Missing orientation in goal.pose causes navigation failure -> Option B

4. Quick Check:

   Orientation required for goal [OK]

Hint: Always set orientation when sending navigation goals [OK]

Common Mistakes:

• Ignoring missing orientation
• Changing frame_id unnecessarily
• Misordering wait_for_result and send_goal

5. You want the robot to navigate to two different points sequentially using ROS move_base. Which approach correctly sets and sends these goals?

hard

A. Send first goal, wait for result, then send second goal and wait again

B. Send both goals at the same time without waiting

C. Send second goal first, then send first goal after completion

D. Only send the last goal; the robot will visit both automatically

Solution

1. Step 1: Understand sequential goal sending

   To visit points in order, send one goal and wait for it to finish before sending the next.

2. Step 2: Evaluate options

   Sending both simultaneously confuses the robot; sending second first breaks order; last goal alone ignores first.

3. Final Answer:

   Send first goal, wait for result, then send second goal and wait again -> Option A

4. Quick Check:

   Sequential goals need wait between sends [OK]

Hint: Wait for each goal to finish before sending next [OK]

Common Mistakes:

• Sending multiple goals simultaneously
• Assuming robot queues goals automatically
• Sending goals in wrong order