Autonomous Solutions
The mustache on the Volvo FH Autonomous contains the sensor stack, the home of all the sensors which allow the truck to perceive the world around it. What started out as a fun nickname for the first design has evolved into the defining feature of our self-driving mining truck.
But behind that friendly nickname sits a lot of engineering work on vibration, dirt, maintenance and scalability.
Vinaya Kumar is Lead Engineer - Mechanical Integration Design at Volvo Autonomous Solutions.
What is it?
The mustache contains three LiDARs, one radar, two inertial measurement units (IMUs), and one camera. Together, these different sensors are what allows the trucks to see and provide the data of which the virtual driver makes its decisions. This requires processing large amounts of data per second and combining them into one image through sensor fusion.
While the software side of it is complex enough, designing the hardware around it also presents a challenging task. Mining and quarrying trucks live a tough life. They spend their days running heavily loaded over unpaved haul roads with rocks and blasting debris. As opposed to inner city driving or highway, these sensors need to withstand much harsher conditions but still operate with the same standard.
That is where the mustache comes in: an encasing that allows for optimal placements of sensors, while also protecting the sensors, allows for easy maintenance, and scalability.
Tough environment
The mustache is designed to handle the demanding requirements of mining and quarrying sites. The design has been validated through simulation and physical testing on track with potholes, steep inclines and challenging weather to make sure the sensors keep working even when the road is anything but smooth.
A key part of that robustness is how it is mounted. Although it looks like part of the cab, the mustache is bolted to the front cross-member of the chassis. The cab is suspended on the chassis and can tilt and roll, and it also has moving parts such as the hatch and the doors. The chassis, by contrast, provides sturdier interfaces and a stable reference point for mounting the sensors, which is why we chose to put the mustache there.
Mining environments are also dirty. The best positions for sensors are often where dust, mud and spray are at their worst. Rather than moving the sensors to cleaner but less useful locations, we bring the cleaning system to them. We are currently testing air and water nozzles that clear lenses and covers without damage, and these cleaning components are designed to survive the same demanding conditions as the sensors themselves.
Built to scale
From the start, we knew the mustache could not be a one-off prototype installation. It had to be something we could build again and again, on different trucks, and that service technicians could live with over many years. That meant designing not only for function, but for maintenance and scalability at the same time.
At Volvo we use CAST (Common Architecture & Shared Technology) as a way to standardize and reuse hardware across our different segments. CAST is our way of building, so every part fits with every other part. This allows us to share technology across products and upgrade as easily as snapping Lego bricks together.
The mustache is built with that mindset. We have divided the front sensor bar into three functional zones: a center zone that carries the LiDAR, radar, IMUs and camera, and two side zones that carry the side LiDARs. The same center stack is reused at the rear of the trailer. This gives us a common “building block” that behaves the same wherever we install it, which simplifies design, calibration, spare parts and training.
Just as important is how the mustache attaches to the truck. Instead of inventing new interfaces. We looked for what the base Volvo FH already offered.
At the front of a normal FH there are two footsteps that drivers use to climb up and clean or access components. We chose to remove one of these footsteps and reuse its mounting points for the mustache bracket. This way, we avoided drilling new holes in the cab, kept changes to the certified base vehicle to a minimum, and gave both the factory and the field a very familiar interface to work with. In practice, we built an advanced sensor module on top of an ordinary part of the truck.
Easy maintenance
Designing for scalability is only half of the story. The other half is designing for maintenance. We have always worked closely with our service colleagues. Every time we proposed a new position or update, we thought carefully about how a technician would work with it in practice: whether the component is realistically reachable, whether the working posture is sustainable when the job is repeated many times, and how much time it adds in a workshop where uptime always matters. We do not decide on a design change until they are satisfied.
The mustache is also a modular system. If a LiDAR fails, you can remove and replace that single unit without disturbing the others. If a bracket is bent, you can swap it for a new one without dismantling the full mustache. We keep spare modules available so that downtime is reduced and the truck can stay operational.
The combination of CAST building blocks and modular hardware means that the mustache can be scaled as well as kept running without major disruptions. That is what the right design achieves.
Growing the mustache
The mustache you see today is the result of many rounds of improvements, upgrades, and redesigns. That evolution is the result of tight collaboration between mechanical design, simulation, calibration, wiring, service teams and suppliers, all feeding their requirements and learnings into the final design.
The earlier installations worked, but they looked and behaved very differently. The sensor hardware was larger, heavier and less integrated, making the mustache look more experimental than the cleaner design you see today.
Since then, the autonomous sensor landscape has moved fast. Over the past six or seven years we have seen smaller LiDARs with better resolution and new suppliers with different geometries and mounting concepts.
We will continue to groom and style the mustache. As sites, sensors and cleaning systems evolve, we will keep refining the details, strengthening what needs to be stronger and simplifying what can be simpler. The goal is always the same: a mustache that quietly does its job in some of the toughest operating conditions you can put a truck in.
