Several sensors are required when the target object is larger than what a single sensor is able to scan. The interconnection of sensors, called networking, is an important capability for robust 3D quality inspection.
Distributed Power, Synchronization and Laser Safety
The ability to create a network requires a considerable amount of forethought in a sensor’s design. The main challenge here is implementing a simple method for distribution of power, synchronization and laser safety throughout the network. LMI solves this challenge with its Master Hub and 65m CAT5e cabling designs.
The LMI Master Hub is a dedicated solution for distributing power, data synchronization and laser safety in a multi-sensor network. Masters allow users to easily scale from a single sensor up to a 24-sensor system, are synchronized within 1 μs accuracy, and feature all-in-one cabling to carry data directly between sensors and a network switch. Synchronization data is broadcast to all sensors includes a timestamp, encoder stamp, and the status of direct inputs wired to the Hub.
Sensor Network Calibration
All sensors in a network have to be aligned in order to take accurate measurements on a final 3D point cloud. To do this, alignment software is required to position multiple sensors to a common coordinate system (i.e., world coordinates).
The process requires a known artifact with precise dimensions of a particular shape that all sensors can scan. These scans need to contain one or more unique artifact features that can be used to determine the position of the sensor in world coordinates.
Sensor coordinates are then transformed into world coordinates to form a final 3D point cloud consisting of all sensor data representing the object.
Dual (Main/Buddy) Sensor Networking
Dual sensor networks are made up of two sensors that LMI calls a main and a buddy.
In Gocator, the main/buddy configuration is a built-in feature. In this setup, the first sensor (main) is paired with a second sensor (buddy). The main sensor is able to automatically “recognize” the buddy sensor when each is connected to the same network.
After pairing is complete, the buddy sensor sends its data to the main sensor. Both datasets are then merged into a common coordinate system and used for measurements. For ease-of-use, Gocator dual sensor systems use a single GUI to configure, measure, make decisions and display results.
Sensor Layout Based on Application
Main/buddy systems can be set up in 3 different orientations depending on the application:
Wide Layout for Scanning Large Objects - Main (left) and buddy (right) are used to measure large objects that are wider than a single sensor’s field of view, such as automotive parts.
- Reverse Layout - A variation of wide layout used in order to minimize occlusions. Watch this video of a Gocator buddy sensor network in reverse layout.
- Opposite Layout for Determining Object Thickness - The main and buddy perform top and bottom differential measurements to calculate true thickness when the object cannot be referenced to a known surface like a conveyor.
- Angled or Ring Layout for Measuring Entire Object Circumference - The main and buddy are set up at an angle or in a ring to eliminate occlusions and scan the entire circumference of an object, as in log scanning applications.
The Future: Scalable Buddy Networking
In some cases, more than one buddy is needed. For example, imagine a case where 20 sensors (10 top, 10 bottom) are required to scan a very long object, from which a large 3D point cloud is generated in order to calculate the object’s volume. In the future, Gocator will offer built-in support for N number of buddies to solve these types of applications.