Autonomous Vehicles Will Change Brake Systems


Deaglán Ó Meachair established to improve the efficiency of the planet’s electric vehicle fleet, by offering the automotive industry the insight and support required to move from legacy systems and grasp the vast potential available through electrification. The following is a section of his latest commentary on this matter, concentrating on autonomous vehicles. The entire piece can be read by clicking on this sentence.

In this installment, I will examine the topic of automated driving, and look at how the rise of autonomous vehicles will change the demands placed on brake systems.

The first thing we need to establish is what constitutes an autonomous car, then look at where we are today, what can we expect in the next decade, and a look further into the future. We will discuss how driving habits will adapt, and how transport solutions that we have known for a long time may start to change.

Then we will examine some of the technical demands that will change what brakes are built into vehicles (especially autonomous ones), talk about how brakes in the future will be used and maintained, and what current technical demands will cease to have significant relevance, and come up with a forward looking view of the braking requirements of our (bright and shiny) autonomous future.

Level Up

Let’s start with what is an autonomous vehicle. The most useful and widely understood reference is the SAE Autonomous Vehicle scale (J3016), which looks at the driver’s tasks (and related vehicle ability), and categorizes these in five levels.

Level Name Comment Controls Driver Fallback
0 No Automation Human Human Human
1 Driver Assistance “hands on” Combo Human Human
2 Partial Automation “hands off” System Human Human
3 Conditional Automation “eyes off” System System Human
4 High Automation “mind off” System System System
5 Full Automation “no driver” System System System

Autonomous Level 0 is the default for today’s vehicles – and incorporates systems which may monitor road conditions and warn a driver, but don’t directly intervene in vehicle controls.

Level 1 and L2 require a driver to oversee the actions of the system and intervene if the system makes a poor decision. Such systems are becoming commonplace in new vehicles and are gaining widespread acceptance due to the improvements in vehicle safety they provide. L3 systems promise to handle more tasks more often and should allow the driver to engage in other tasks.

L3 systems can require human intervention, but with a small buffer (typically 30s).

The primary difference between L4 and L5 is that L4 is expected to be fully autonomous, but within limited road conditions – for example on motorways and national roads and requiring some human assistance at more complex environments. L5 systems are vehicles which drive themselves, with no provision needed for human drivers.

Since 2018, a fully autonomous taxi service has been operating in Arizona, and many more are planned. Meanwhile, in Sweden, fully autonomous trucks are entering public testing.

Brakes for robots

Now that we have a handle on what constitutes an autonomous vehicle, and a view of where such vehicles are in development, it gives context to discuss what sort of brakes might be required. The first significant change (to enable even L1 abilities) is on the actuation side – the ability to engage the braking system without driver input. While this problem was originally addressed in the vacuum booster, it is now more common to use the ESC system to generate brake pressure as required. In such a system, while the “robot” can generate braking force via the brake assistance, if there is a failure of the robot or the assistance mechanism, the fall back is the driver’s unassisted foot. In this scenario, the addition of autonomous braking doesn’t necessarily create extra redundancy complexity – the sizing of the hydraulic components will be as before, and the driver is required to deploy a similar amount of force to achieve the braking power.

The remainder of this post can be read by clicking on this sentence.

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