Stationary Environment 3D Scanning - Efficient and Portable Mid-40 sol

Livox Pioneer

Stationary Environment 3D Scanning - Efficient and Portable Mid-40 solution on a Tripod

2019/07/05  In this case, we use one Mid-40 and the motor mounted on top of a tripod to rotate around the z axis to scan different parts of the room, and integrate the point cloud data to give an overall 3D image.
  Livox has brought new solutions to the industry with our high-performing, cost-effective, highly-reliable and mass-produced LiDAR sensors. To showcase the capabilities of our LiDAR sensors, we used a Livox MID-40, priced at USD 599, to capture a 3D interior point cloud image of a room.
  Livox MID-40 key specs can be found here: https://www.livoxtech.com/mid-40-and-mid-100/specs.
  Setup
  The 3D scanning solution mainly consists of a MID-40, a DJI Manifold 2, and a GM6020 motor with an encoder. Main components of this setup are shown in Figure 1. The LiDAR and the motor are mounted on top of a tripod and the MID-40 rotates around the z axis to scan different parts of the room. The point cloud data is then integrated to give an overall 3D image.
   
  

  

Figure 1. MID-40 and other main components of this setup

  

  To make the scanner more portable, a 24V battery, together with a 24V-to-12V step-down converter, is used to provide the input voltage for the MID-40 (12V), the DJI Manifold 2 (24V) and the GM6020 motor (24V). In fact, we have even integrated everything that is not on the tripod in a box as shown in Figure 2 to maximize the portability.
  

  

Figure 2. Integrated solution with most components assembled inside a box

  

  

  Communication & Data Integration
  The MID-40 is set to static IP mode and connected directly to Manifold 2’s Ethernet port for point cloud data transmission. The Manifold 2’s CAN port is used to control the motor and read its angle information. Cable connections are shown in Figure 3.
  

  

  

Figure 3. Schematic of cable connections

   
  

  The GM6020 motor’s angular resolution is 360/8192 degree, which is enough for this application. To maintain a constant rotating speed during scanning, the control voltage is regulated by a PID controller using the motor speed and encoder information as feedback.
  Angular data are transmitted to the Manifold 2 at a frequency of 1 kHz through the CAN bus. The MID-40 also transmits point cloud data package containing 100 samples at a frequency of 1 kHz. Therefore, we simply correlate the angular data sent by the motor and the data package together for the overall point cloud integration.
  Since the encoder provides absolute position, the angular information should stay consistent among multiple repeated scans. Therefore, we move the motor back to zero position when powered up, and then scan back and forth for a pre-defined angle around this position while integrating the acquired point cloud data together.
  

  

  

Figure 4. Scanning method during operation

  

  

  Scanning Pattern and Result
  Livox LiDAR sensors adopt unique non-repeating scanning patterns which can be beneficial for many applications that require high FOV coverage, and stationary environment 3D scanning is one of such applications. The detailed information regarding scanning patterns can be found in the ‘Point cloud characteristics’ at https://www.livoxtech.com/mid-40-and-mid-100/downloads.
  When the integration time is 0.1 second, the MID-40 has an FOV coverage that is equivalent to 32-line mechanical scanning LiDARs. And as the scan time increases, the FOV coverage also increases significantly - with an integration time of 0.5 second, the coverage performance is equivalent to 64-line LiDARs.
  With this setup, we scanned a room for 30 seconds. The result is shown in Figure 5.
  

  

  

  

Figure 5. 3D point cloud image of a room after scanning for 30 seconds

  

   
  As shown in the scanned image above, the MID-40 has scanned most areas of the room with rich details. Being a simple test case, there are still many aspects that could be further optimized. Nevertheless, the result shows that the performance of this solution is comparable with multi-line mechanical scanning LiDARs, while being much more cost-effective.
  With their powerful performance, low cost and high reliability, we believe Livox LiDARs will be used in an exceptional wide range of applications in the near future.