The Navigator

A navigation skill for path planning based on receiving external location and obstacle data

+ How To Add This Control To Your Project (Click to Expand)
  1. Make sure you have the latest version of ARC installed.
  2. Select the Get button in this page to download the archive file.
  3. Double click the downloaded archive file to execute installer.
  4. The installer will add this control to ARC.
  5. Load ARC and press the Project -> Add Control button from the menu.
  6. Choose the Navigation category tab.
  7. Press the The Navigator icon to add the control to your project.


A navigation skill for path planning based on receiving NMS location/positioning and obstacle data. This skill is used in combination with other skills that contribute navigation data to ARC's Navigation Messaging System (NMS).

This screenshot is using an Intel RealSense T265 with 3 low-cost HC-SR04 ultrasonic distance sensors. The robot was instructed to drive around the way-points at various speeds. Ideally, you would want to use this robot skill with a 360-degree lidar or other high-resolution obstacle detection.
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Here is a video of The Navigator working in conjunction with the Intel RealSense T265 tracking camera skill, which operates at NMS Level #3 Group #2 by providing position/location data into the NMS

ARC Navigation Messaging System
This skill is part of the ARC navigation messaging system. It is encouraged to read more about the Navigation Messaging System and learn about compatible skills. This particular skill (The Navigator) operates on Level #1 of the NMS overview. This skill (The Navigator) requires a Level #3 Group #2 location/position sensor for operation. The location/positioning system will feed position data into the NMS which this skill will use for navigation. See the NMS for compatible skills that provide location/position data.
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While your robot is driving around and navigating, this skill will log the trajectory. By manually driving your robot to various locations (waypoints), you define the waypoint and path points. Once multiple path points are defined for a waypoint, you can instruct your robot to autonomously navigate to that exact waypoint (or back again) at any time.

Map Size
The map is currently hardcoded for 20x20 meters.

Main Screen
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1) Map control buttons for clearing trajectory and clearing the map.

2) Current cartesian coordinates of the robot as reported by an NMS Level #3 Group #2 sensor (i.e. Intel T265, wheel encoders).

3) Saved waypoints. Here you can add, remove and select waypoints.

4) The path points within a waypoint. A waypoint will consist of many path points for navigating throughout the environment. You may right-click on path points to edit the coordinate for fine-tuning. You may also re-order the path points by right-clicking and selecting Move Up or Move Down.

5) Current heading of the robot relative to the cartesian starting position as reported by an NMS Level #3 Group #2 sensor.

6) The yellow dot marks the robot's current cartesian position as reported by an NMS Level #3 Group #2 position/location sensor.

7) Path points are connected with a straight line that demonstrates where the robot would drive. To add path points, right-click on the map view and select Add Path Point. It is best to drive the robot which creates a trajectory. Then, simply right-click on some points of the tractory to add new path points to the selected waypoint.

8) Log messages are displayed about navigation and sensor activity.

Main Screen - Navigation Controls
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There are three buttons for manually starting navigating. You may also start navigating by using ControlCommands from other skills. The three buttons each have different behavior.

Start (Forward Order) - This will instruct the robot to start following the specified paths within the waypoint from the first to last in that order. If your robot is close to the starting (first path point), then it will be convenient and head right there. However, if your robot is far away from the first path point, you may wish to use the Reverse or Auto button.

Start (Reverse Order) - This will instruct the robot to start following the specified paths within the waypoint in reverse order from last to first. If your robot is closest to the last path point, this will be convenient to get your robot back to the first path point in the waypoint. 

Start (Auto) - This will automatically calculate which order to execute the path direction based on the robot's distance from either the first or last path point. This is the most convenient operation because it will allow a waypoint to be navigated to and from. For example, if your robot drives to a location use this button to also get your robot back to the starting location. This will happen automatically.

Config - Scripts
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1) Script that will execute when the navigation to a waypoint is started. Navigation can start by either manually pressing the Start button or using a ControlCommand().

2) Script will execute when the navigation is canceled or successfully ended.

3) If the navigation is paused by either a JavaScript/Python command from the Navigation namespace. Or if the paused is triggered by the NMS Level #3 Group #1 distance sensor returning a value less than the specified range. This is configured in the Settings tab.

Config - Variables
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There are many global variables that are set for The Navigator. There is a question mark next to each variable which explains in greater detail. The variable contents can be viewed using the Variable Watcher skill found in the Scripts category.

Config - Settings
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1) Ignore distance values that are less than this specified distance in CM. The distance values are provided by any NMS Level #3 Group #1 sensor.

2) Ignore distance values that are further than this specified distance in CM. The distance values are provided by any NMS Level #3 Group #1 sensor.

3) Filter false positives by removing obstacles that are detected and then later not detected within the same area.

4) If the NMS distance sensor provides a value that is greater than the "lower than" but lower than this, any navigation will be paused. This will also execute the PAUSE script from the Scripts tab. Your program may use this opportunity to navigate through the obstacle and continue navigating again. To continue navigating, use the Javascript or Python command in the Navigation namespace. That command is Navigation.setNavigationStatusToNavigating();

5) This value complements the pause navigation distance value. This value will determine the degree range of when to pause navigation. If you wish for the entire range to be paused, enter 360 degrees. If you only want objects in front of the robot paused, enter 90. The degree number entered is divided by two and used from the left and right of the center of the robot.
- If 90 degrees is entered, then 45 degrees to the left of the center of the robot and 45 degrees to the right of the center of the robot are detected.
- If 180 degrees is entered, then 90 degrees to the left of the center of the robot and 90 degrees to the right of the center of the robot are detected.
- If 360 degrees are entered, then the full range will be detected.

Starting Position
This navigation skill uses cartesian coordinates in CM from the starting position (0, 0). This means that any saved maps will be referenced from the same starting position and heading angle. When you re-load a project to have the robot navigate the same course, the robot must be positioned in the same starting position and heading angle. We recommend using painter/masking tape as the starting reference point for the robot. If your robot has an auto dock for charging, secure the charger to a fixed position on the floor and that can be used as a reference point. 

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In the photo above, we're using an iRobot Roomba as the robot with an Intel T265 positioning sensor. The painter's tape on the floor is marking the starting position of the robot. The outline allows us to position the robot into the square, and the marking on the front of the robot aligns with the specified heading.

Cartesian Coordinate System
This robot skill uses cartesian coordinates to reference the robot's position from the starting position. The starting position is always 0,0 and is defined at startup. As the robot navigates, the skill measures the distance from the starting position. The unit of measurement is in CM (centimeters). Read more about the cartesian coordinate system on Wikipedia.
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How Do You Use This
This skill is a navigation renderer and movement planner. This means it can build a map from participating sensor data and control the robot by navigating it to specified locations. In order to get sensor data, other skills must be loaded that are compatible. In this quick example, we'll simply use the Intel Realsense T265 in combination with this skill...
1) Connect your Intel RealSense T265 to the computer's USB port

2) Load ARC (version must be >= 2020.12.25.00)

3) Add the Intel RealSense skill to your workspace

4) Now add this skill (The Navigator) to your workspace

5) Press START on the Intel RealSense skill

6) You should now begin to see localization path data from the Intel RealSense sensor being displayed in The Navigator window. This robot skill will be displaying and rendering the data.

*Optionally, you may now add a supporting NMS Level #3 Group #1 sensor for detecting distance of obstacles and environment.

To Do
This skill is under development and a number of items are left to be completed...
- Create custom paths based on pre-programmed paths when navigating between waypoints
- Automatically navigate obstacle avoidance

#63   — Edited
Did you try yours today?

here is a pic:
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as you can see nothing on the screen
#65   — Edited
Ezang has no NMS level #3 group #2 sensor. Some form of positioning sensor is required and documented in the manuals.

an NMS level #3 group #2 sensor provides positioning or pose information. An example sensor would be an iRobot movement panel, t265 intel realsense, or wheel encoders, etc.. Check the NMS page for more info. 

here’s a screenshot from the manual for The Navigator
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#67   — Edited
Does that sensor work at level 3 group 1 or level 3 group 2?

what does the manual say for that sensor? Also, in the NMS diagram, check out where that sensor sits in the group list...
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#68   — Edited
I am using the ultrasonic sensor  - 3 wire -  - ez robot

and a

ultrasonic sensor  4 wire  - look like lever 3

on an IoTiny

strange, this all worked when you first did this
The Navigator with NMS would never have worked for anyone, including myself, without a Level #3 Group #2 location/pose input. 

You require an NMS Level #3 Group #2 input, here's the image again - which can be seen in the NMS manual as well.

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#70   — Edited
Level #3 - Sensor Groups
Skills you require are sensors that feed data into the messaging system that maps are made from. The Navigation Messaging System collects data by supporting two sensor input groups...

Supported skills are...
Ultrasonic Distance

take a look
strange, today it shows:

level 3  - ultrasonic sensor is showing today:

Navigation Messaging System

send ping results to NMS

however I still don't see the the red on the screen like you with the ultrasonic sensors
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I will watch video again, thanks
#71   — Edited
You need an encoder or a T265. How could the Navigator know the position of your robot without them?
Level 3 group 2 sensors!
#72   — Edited
ok I understand thanks

I almost bought the camera 69.00
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Added variables for nearest and furthest degree and distance.

Question about the TODO items:
- Automatically navigate obstacle avoidance
- Load and save maps

Do you have an estimated timeframe for the first one?  My experience now that I have my Lidar working (mostly) is that the Navigator is not looking a the direction of movement and the direction of near obstacle, so if it passes close to a wall but nothing is obstructing the direction of travel, it is still pausing.  If you are a week or two away from building in the functionality, I will wait.  If it is further down your list, or you don't know, I can write some scripts to handle the situation, but they will be pretty complex since I'll want to compare distances to each side in a range of degrees to determine which way to turn before attempting to continue.

For the second item, I just wanted to say I am glad you are planning it.  For now, my plan is to just save different versions of hte project for different maps (or really, starting points) but as I make changes in projects, that could become a real hassle.  Would rather just pull up the map for a particular starting point in the same project.

I don’t have a time frame. But you can just disable the pausing feature in the navigator.


I don’t have a time frame. But you can just disable the pausing feature in the navigator.
Well yeah, but if I do that, then it runs into the walls going straight:)

I'll start with some scripts and see how fancy I can get using the navigator variables available.  (I seriously need to learn Javascript though.  I think it would be way less complex to script this in Javascript than EZ-Script).

#78   — Edited

- allow specifying a limit to the number of degrees that will trigger the NMS pause event.
- nearest & furthest variables are only set when there is scan data (no longer displaying strange numbers)
- a performance improvement that lowered 3% cpu usage on my test computer

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Awesome, thanks for the update.

I can't test tonight, but I will try it out tomorrow.
#80   — Edited
- Updated object renderer

- Performance improvement

- Saves map with project


- Saves map with project
Also YES!!!!
- new option for enabling/disabling map building. If unchecked, the map will stay static and not be updated

- new option in config for how many trajectory points to remember (Avoid clutter of UI)