LiDAR Mechanical Design – Managing the Heart

By Luc Tremblay
Mechanical Designer

 

With this blog, I want to give you a glimpse into the mechanical design aspect of LiDAR development, specifically, an overview of Mechanical Scanning LiDAR VS Solid-State LiDAR and the importance of thermal management.

 

How it’s Made

Let’s begin by talking about Mechanical Scanning LiDARs. From a mechanical point of view, Mechanical LiDARs detect objects via the rotating assembly of collimated lasers and through focused optics which return the collected light to the detectors. This rotating assembly creates a wide field of view (up to 360 degrees).

Solid-state LiDARs (SSL) have no moving parts and do not have motorized mechanical scanning. They have a slightly reduced field of view (FOV) but are significantly less expensive to produce. SSLs use arrays of emitters and receivers, as well as imaging optics, to provide range, as well as vertical FOV and angular resolution, that are comparable or better than those of mechanical scanning lidars. You can also easily convert data into 3D maps to interpret the environment, allowing for greater perception capabilities.  Mechanical scanning LiDARs are not as rugged as the Solid-state lidars. Due to the rotating nature of their assembly, you will likely have to replace them more often depending on the application.

For more information, see Why LiDAR

One of the most critical differentiating factors between Mechanical scanning LiDARs and SSL, is that of safety.  Typical Mechanical scanning LiDARs cannot see the immediate vicinity of the vehicle – known as the dead zone.  With SSLs however, you can create a safety cocoon around the vehicle.

For more information, read about the Leddar Pixell

 

SSL = Mini Component + Big Heat

A major consideration in the mechanical design process for Solid-state LiDAR is given to thermal management.

When it comes to electronics, small is best!  With the miniaturisation of electronic components, the ultimate goal is to package your components in the “smallest” enclosure possible. A smaller form factor is always easier to integrate, especially in automotive applications. However, Smaller electronic components equate to a higher heat density. In LiDAR design, heat management is always front of mind.

The first challenge is to pull most of the heat away from components such as the CPU, the SoC the lasers etc.

We have a few different options:

• Using different materials – aluminum VS copper
• Using more sophisticated parts – heat pipe VS thermoelectric effect
• Pulling all the heat out of the enclosure by designing a heat sink to which you can also adapt fins for added dissipation

 

We also have thermal modelling software to help us verify and assess heat transfer.

Thermodynamic and mechanical heat transfer is calculated with the heat transfer coefficient, the proportionality between the heat flux and the thermodynamic driving force for the flow of heat.  Heat flux is a quantitative, vectorial representation of heat flow through a surface.

Now, you might be thinking: “it’s easy, just put holes in the enclosure!”  

If only it were that easy!

This specific casing will have to sit on the exterior of a vehicle as it needs visibility of the outside world in order to detect potential obstacles, meaning, it will have to deal with the weather and its many elements. In the case of LiDAR, the casing is sealed from dust and water and must meet certain standards. There is also the ambient climate/temperature to consider as in some environments the temperature can fluctuate between very hot and very cold and we must ensure functionality across a given range.  This is one of the greatest challenges to LiDAR mechanical design.

It’s always challenging to accommodate electronics, optics and integrators but when done correctly, you end up with a remarkable and dependable product!