Applications
ASG for autonomous vehicles
Why the layer between the autopilot and the vehicle is the part that has to be synchronous.
In one sentence A Level 4 or 5 autopilot can generate a correct motion vector and still be let down by asynchronous communication to the vehicle. ASG is the synchronous control layer that carries the vector out.
What a Level 4 or 5 autopilot is
The autopilot heading for mass production is, in essence, two things: vision devices, cameras, lidar, radar and similar sensors, and a centralised high-speed computing system with the features of a learning neural network. That component set is interfaced to the vehicle’s motion components, steering, accelerator, brakes and the rest, through standard asynchronous communication channels: CAN and its successors, Automotive Ethernet, LIN.
It works by processing and synchronising the sensor data, generating a motion vector for the car, and issuing commands to the actuating mechanisms to hold that vector, while continuously comparing the assigned position with the actual one.
Where it breaks: the fuzzy motion vector
The motion-control systems are mass-produced electromechanical units reached over asynchronous channels. Because those channels carry data referring to different time points, the realised motion vector is fuzzy relative to the synchronisation grid on which the autopilot formed it. The faster the car goes, the wider that dispersion, until the vehicle deviates from the planned trajectory. Asynchronous communication disrupts the time grid of the vehicle’s systems, which, by control theory, makes the control loop unstable: this is the primary cause of a car skidding on a quick change of commands.
Acting on many outputs at once
The fix is for the layer managing the motion units to run in the same time grid as the autopilot, and to treat the car as a single entity: generate its motion vector as a whole, rather than issuing separate commands to the steering, the accelerator and the brakes. On a message bus those commands are addressed one at a time, so the arrivals spread across the window. On ASG they are one commit.
The vehicle state vector window
ASG makes that whole-vehicle vector the native object. A control supervisor holds a system state vector window that is rewritten across every module at 1 kHz, once per millisecond. Each module runs its own fragment of the motion-vector control programs and drives the sensors and actuators in its zone. The autopilot addresses one coherent snapshot of the vehicle rather than assembling one from messages that arrived at different times. The real-time OS page describes the window in full.
One organism, not a network of controllers
ASG integrates the nodes and control systems of the vehicle into a single synchronised organism that can make decisions in real time under the guidance of an autopilot. Every module reads the whole state; one feature writes each value; the commit is atomic. Determinism does not degrade as load rises or as modules are added, because sharing the channel by frequency rather than by time means an extra module takes a carrier, not frame time.
This is the layer we consider the missing element of a Level 4 or 5 autopilot. We have written about it separately.
Questions
Does ASG do perception or planning?
No. ASG is the control layer underneath the autonomy stack. Perception and planning run on top of it; what ASG provides is a synchronous, timestamped vehicle state to plan against, and synchronous actuation to carry the plan out.
Why does the control vector have to be generated in about 1 ms?
A vehicle interacts with its surroundings at up to roughly 100 Hz at speed. By the sampling theorem, holding around one per cent control precision means generating the control vector in no more than about 1 ms. When the data is large, an asynchronous system takes longer than that, and the vector is already stale when it is applied.
Is time-sensitive Automotive Ethernet not enough?
A switched network with TSN schedules frames to arrive close together, but the actuators are still addressed one message at a time and the delays at network junctions remain. They affect motion-control stability and are worked on at the implementation stage. ASG commits every output in a control group in the same 1 ms instant by construction. The full comparison is on ASG vs Automotive Ethernet.
Is ASG an autonomous-driving product?
No. ASG is a real-time E/E architecture for the vehicle. It suits autonomy because of how it handles vehicle state and actuation, but it is powertrain- and application-agnostic and runs on vehicles that are not autonomous.