Whether you are developing your ADAS features on a small scale non-production platform like a golf buggy or an RC car, or you are designing and implementing your features on a production vehicle that will ultimately need type approval, then I suggest you read on, as this will affect you if the features you are working on, in any way affect the lateral motion of your vehicle.
UNITED NATIONS REGULATION ECE 79
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF: VEHICLES WITH REGARD TO STEERING EQUIPMENT
Regulation 79, known throughout the industry as simply Reg 79, was created with the intention of providing a common understanding and thus a definition of what a “steering system” fitted to a road vehicle is, from their layout to the performance of the overall system, and thus to provide a basis on which steering systems are to be evaluated for their suitability for the outside world.
However, things change, technology advances, and we have come along way since Fred and Barney took to the highway. In fact, if we take a look at just the last 10 years, the functions associated with how a vehicle’s direction is controlled, have changed dramatically. Features such as electric power steering, which replaced the traditional hydraulic assist power steering pump, (either of which would have made Fred’s day given the weight of his stone front roller), we now take for granted; and the list goes on. As well as amplifying the driver’s input at the steering wheel, in order to turn the road wheels, the majority of power steering systems also apply an additional level of steering input intended to compensate for the effects of side wind and the obvious effects of gravity on cambered roads.
Now let’s consider the lateral motion based Advanced Driver Assistance Systems (ADAS) and the world’s race to vehicle autonomy. If we take a look at the Lane Departure Avoidance (LDA) feature, (aka Lane Keeping Assistance (LKA)), and the more recent Lane Centring and Lane Change features, they are designed yet again, to correct the driver’s steering angle and thus the vehicle’s trajectory, this time in order to avoid a lane departure i.e. a line crossing, or indeed to instigate a lane departure un-aided by the driver. This is yet another major step forward in steering technology, philosophy and methods, and the United Nations Economic Commission for Europe has been watching.
UNITED NATIONS REGULATION ECE 79-02
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF: VEHICLES WITH REGARD TO STEERING EQUIPMENT
Regulation 79-02 came into force on the 10th October 2017 and from the 1st April 2018, all parties seeking UN type approval for their vehicle must meet these regulations. For those of you that aren’t seeking type approval, but are simply developing in-house on small platforms, it is still worth considering the regulation as the requirements that are held within it define what your features should and should not do, to the point of coming very close to being a system requirements specification.
If we take LDA for example, categorised by the regulation as a “Corrective Steering Function” (CSF), and defined in the regulation as:
“A control function within an electronic control system whereby, for a limited duration, changes to the steering angle of one or more wheels may result from the automatic evaluation of signals initiated on-board the vehicle, in order:
(a) To compensate a sudden, unexpected change in the side force of the vehicle, or;
(b) To improve the vehicle stability (e.g. side wind, differing adhesion road conditions “μ-split”), or;
(c) To correct lane departure. (e.g. to avoid crossing lane markings, leaving the road).”
the regulation goes on to demand, in section 5.1. General Provisions, a number of key components that should be present in your design. These requirements range from feature overrides to cluster graphics and audios, and for the first time the regulation calls for a driver disengagement detection and alert strategy for this feature type. This newly prescribed hands off detection system is designed to significantly annoy the driver into resuming a hands on position with the aim of ensuring that feature mis-use is minimised as much as possible. Interestingly it does not call for feature disablement.
Lane Centring and Lane Change based features are referred to as an “Automatically Commanded Steering Function” (ACSF) and are defined in the regulation as:
“A function within an electronic control system where actuation of the steering system can result from automatic evaluation of signals initiated on-board the vehicle, possibly in conjunction with passive infrastructure features, to generate control action in order to assist the driver.”
In this case, the regulation accounts for, in section 5.6. Provisions for ACSF, a range of features including fully automatic steering control systems and breaks them out into 6 categories, from low speed parking type features to high speed features that are able to determine when a manoeuvre is possible and is subsequently able to complete that manoeuvre. The regulation specifies for each, a range of requirements from maximum steering effort and maximum lateral acceleration, to what the driver alerts should look and sound like. The regulation once again outlines a driver disengagement detection and alert strategy, calling for a multiple stage alert and deactivation of the feature should the driver fail to re-engage, which as mentioned above, is not applicable to the CSF category.
Additionally to the system requirements mentioned above, the regulation also makes reference to 8 annexes which include requirements for a number of key areas. Annex 6 which covers the “Safety Aspects of Complex Electronic Vehicle Control systems” and Annex 8 which covers the “Test Requirements For Corrective And Automatically Commanded Steering Functions” are of particular importance and should be fully understood by any engineering team embarking upon the design of any of the above features.
In conclusion, UNECE 79-02 is a “MUST READ” document for any ADAS or Power Steering design team, and the sooner you read it and understand the constraints it imposes, the smoother your path to production will be. It is also worth bearing in mind that if your feature does something that isn’t covered in the regulation, then it isn’t regulated, and if it isn’t regulated and your feature directly affects the angle of the steering road wheels, then you may struggle to get it through type approval.
One final note, 79-03 is coming soon.
You have been warned.