turbopilot
RVF Expert
I just found a document new to me but has apparently been around since 2017 titled OnGuardActive System Description.
I have made one pass through the document but it will take some more reading before I fully digest the content. OnGuard is a far more robust system than I thought. Many moving parts to this system. I will highlight some notes I have taken representing new information for me about the system. Documentation clearly states there will be false and unwanted warnings and activations. It is an acknowledged "restriction" of OnGuard. This document covers in detail differences (which are significant) between operation supporting Adaptive Cruise Control (ACC) versus activation of the Collision Mitigation System (CMS).
Everyone with this option should read this document. I now understand much better some of the subtle things that happen driving with OnGuard. I have had 3 OnGuard "crashes" since new. Each crash through a "blocking" error and required restarting the engine to clear the error. Since I drive predominately in the SouthWest US I now understand what is happening as the system is designed to shut down with a blocking error when it does not detect any objects for a period of time (section 6.1.2).
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OnGuardACTIVE is an advanced driver assistance system with the following functions:
ACC (Adaptive Cruise Control)
. DW (Distance Warning)
FCW (Forward Collision Warning)
CMS (Collision Mitigation System)
EBA (Extended Brake Assist)
Section 3.7.4.1 False and unwanted warnings
In addition to unnecessary warnings, false warnings can also occur. False warnings are caused by incorrect measurement or classification of detected objects. Such restrictions currently represent the current state of technology for individual radar sensors.
Section 6.1 Sensor Overview
OnGuardACTIVE uses a 77 GHz radar sensor with a mechanical scan antenna that contains two independent radar beams: a long-range beam of ±9° with a range from 0.25 to 200 m, and a short-range beam of ±28° with a range from 0.25 to 60 m. The system operates simultaneously in transmission and reception mode, with both operating modes using the same antenna.
... use object data from a forward-facing radar sensor, which is mounted at the front of the host vehicle. This radar sensor creates an object list of the six closest objects on each lane (two objects respectively for its own lane, the adjacent lane to the right and to the left) for the above functions. The AEBS, EBA, CMS and FCW functions take all these objects into account, while ACC and DW only use one object – the closest object on the host vehicle’s lane.
ACC (adaptive cruise control) only responds to moving and stopped objects driving in the same direction. It does not respond to stationary or oncoming objects. An object that was initially detected as moving and then stops is classified as a stopped vehicle. An object that has never before been detected as moving is classified as a stationary object.
Section 3.2.2.1 Input from driver
The driver can override ACC at any time by pressing the accelerator pedal. The maximum deceleration that ACC can request from the braking system is -2.5 m/s2.
Section 3.2.3 ACC Control Behavior
The ACC function supports three different main control mechanisms, depending on the current driving manoeuvre. It distinguishes between continuous follow-on driving, approach manoeuvres with a lower than the set distance to a slower object and the removal of an object (e. g. after an approach manoeuvre or due to an object that is moving into the current follow-on distance).
Section 3.2.3.3 Moving Away
When a faster vehicle (e.g. an overtaking car) moves into the lane of the host vehicle, ACC offers a special behaviour. If the distance produced by the manoeuvre is very small, ACC’s response would normally be very sharp. In the situation described above, such a drastic reaction would not be desired, however, because overtaking manoeuvres should not influence the dynamics of the host vehicle. This is less fuel-efficient and uncomfortable. If a faster objects moves into lane and remains faster, ACC will not react at all in most cases.
Section 3.3.3.2 Lateral Acceleration
When the lateral acceleration actually begins to exceed the parameterised threshold value (the default value is 2 m/s2), ACC limits the engine torque to prevent further acceleration and thus a further increase in lateral acceleration. Under certain conditions the lateral acceleration limitation function can also request the retarder and/or the wheel brakes.
4.3.4 Distance warning (DW)
DW is an extension of ACC and, like ACC, only responds to moving and stopped objects that drive on the same lane and in the same direction as the host vehicle. It does not react to stationary of oncoming objects.
6.3.6 Collision Mitigation System (CMS) incl. collision warning (FCW)
CMS automatically initiates partial braking of max. -3.5 m/s2 in order to reduce the total collision energy if the system assumes that a collision is unavoidable. CMS cannot prevent the accident.For its function CMS calculates the likely movement for the host vehicle and the vehicles driving ahead. Taking into account the estimated response time of the driver to carry out emergency braking or an evasive manoeuvre, the CMS initiates automatic braking if a collision is assessed as unavoidable by braking or steering action through the driver. In general, the CMS uses the same algorithms as the AEBS function, but is configured differently.
3.7.3.3 Reaction to objects that enter the lane of the host vehicle
The emergency braking sequence may differ if the FCW cannot start early enough. This situation could occur if the criteria for issuing the warning are fulfilled too late – e.g. if an object enters the lane of the host vehicle at a very short distance. Figure 3 shows an example of such a cutting-in situation at a short distance. As a result, the warning is issued too late because the object was not relevant for the warning before it executed its cutting-in manoeuvre. After the FCW has been output, the situation is so critical that AEBS starts activating the brake shortly after the FCW. The HCW is skipped, but AEBS is limited
in its deceleration while the minimum warning time (1.4 seconds) has not yet been reached. After the minimum warning time has elapsed, AEBS requests its full braking power. In this situation, collision avoidance is not possible due to the limited emergency braking at the beginning of the event.
6.1.2 Blockage detection
Driving in areas without traffic ahead and almost without objects at the roadside (e. g. desert-like regions) can also lead to a blocking error, because the radar does not detect any objects.
I have made one pass through the document but it will take some more reading before I fully digest the content. OnGuard is a far more robust system than I thought. Many moving parts to this system. I will highlight some notes I have taken representing new information for me about the system. Documentation clearly states there will be false and unwanted warnings and activations. It is an acknowledged "restriction" of OnGuard. This document covers in detail differences (which are significant) between operation supporting Adaptive Cruise Control (ACC) versus activation of the Collision Mitigation System (CMS).
Everyone with this option should read this document. I now understand much better some of the subtle things that happen driving with OnGuard. I have had 3 OnGuard "crashes" since new. Each crash through a "blocking" error and required restarting the engine to clear the error. Since I drive predominately in the SouthWest US I now understand what is happening as the system is designed to shut down with a blocking error when it does not detect any objects for a period of time (section 6.1.2).
-------------------------------------------------------------------------------------------------------------------------------------------------------
OnGuardACTIVE is an advanced driver assistance system with the following functions:
ACC (Adaptive Cruise Control)
. DW (Distance Warning)
FCW (Forward Collision Warning)
CMS (Collision Mitigation System)
EBA (Extended Brake Assist)
Section 3.7.4.1 False and unwanted warnings
In addition to unnecessary warnings, false warnings can also occur. False warnings are caused by incorrect measurement or classification of detected objects. Such restrictions currently represent the current state of technology for individual radar sensors.
Section 6.1 Sensor Overview
OnGuardACTIVE uses a 77 GHz radar sensor with a mechanical scan antenna that contains two independent radar beams: a long-range beam of ±9° with a range from 0.25 to 200 m, and a short-range beam of ±28° with a range from 0.25 to 60 m. The system operates simultaneously in transmission and reception mode, with both operating modes using the same antenna.
... use object data from a forward-facing radar sensor, which is mounted at the front of the host vehicle. This radar sensor creates an object list of the six closest objects on each lane (two objects respectively for its own lane, the adjacent lane to the right and to the left) for the above functions. The AEBS, EBA, CMS and FCW functions take all these objects into account, while ACC and DW only use one object – the closest object on the host vehicle’s lane.
ACC (adaptive cruise control) only responds to moving and stopped objects driving in the same direction. It does not respond to stationary or oncoming objects. An object that was initially detected as moving and then stops is classified as a stopped vehicle. An object that has never before been detected as moving is classified as a stationary object.
Section 3.2.2.1 Input from driver
The driver can override ACC at any time by pressing the accelerator pedal. The maximum deceleration that ACC can request from the braking system is -2.5 m/s2.
Section 3.2.3 ACC Control Behavior
The ACC function supports three different main control mechanisms, depending on the current driving manoeuvre. It distinguishes between continuous follow-on driving, approach manoeuvres with a lower than the set distance to a slower object and the removal of an object (e. g. after an approach manoeuvre or due to an object that is moving into the current follow-on distance).
Section 3.2.3.3 Moving Away
When a faster vehicle (e.g. an overtaking car) moves into the lane of the host vehicle, ACC offers a special behaviour. If the distance produced by the manoeuvre is very small, ACC’s response would normally be very sharp. In the situation described above, such a drastic reaction would not be desired, however, because overtaking manoeuvres should not influence the dynamics of the host vehicle. This is less fuel-efficient and uncomfortable. If a faster objects moves into lane and remains faster, ACC will not react at all in most cases.
Section 3.3.3.2 Lateral Acceleration
When the lateral acceleration actually begins to exceed the parameterised threshold value (the default value is 2 m/s2), ACC limits the engine torque to prevent further acceleration and thus a further increase in lateral acceleration. Under certain conditions the lateral acceleration limitation function can also request the retarder and/or the wheel brakes.
4.3.4 Distance warning (DW)
DW is an extension of ACC and, like ACC, only responds to moving and stopped objects that drive on the same lane and in the same direction as the host vehicle. It does not react to stationary of oncoming objects.
6.3.6 Collision Mitigation System (CMS) incl. collision warning (FCW)
CMS automatically initiates partial braking of max. -3.5 m/s2 in order to reduce the total collision energy if the system assumes that a collision is unavoidable. CMS cannot prevent the accident.For its function CMS calculates the likely movement for the host vehicle and the vehicles driving ahead. Taking into account the estimated response time of the driver to carry out emergency braking or an evasive manoeuvre, the CMS initiates automatic braking if a collision is assessed as unavoidable by braking or steering action through the driver. In general, the CMS uses the same algorithms as the AEBS function, but is configured differently.
3.7.3.3 Reaction to objects that enter the lane of the host vehicle
The emergency braking sequence may differ if the FCW cannot start early enough. This situation could occur if the criteria for issuing the warning are fulfilled too late – e.g. if an object enters the lane of the host vehicle at a very short distance. Figure 3 shows an example of such a cutting-in situation at a short distance. As a result, the warning is issued too late because the object was not relevant for the warning before it executed its cutting-in manoeuvre. After the FCW has been output, the situation is so critical that AEBS starts activating the brake shortly after the FCW. The HCW is skipped, but AEBS is limited
in its deceleration while the minimum warning time (1.4 seconds) has not yet been reached. After the minimum warning time has elapsed, AEBS requests its full braking power. In this situation, collision avoidance is not possible due to the limited emergency braking at the beginning of the event.
6.1.2 Blockage detection
Driving in areas without traffic ahead and almost without objects at the roadside (e. g. desert-like regions) can also lead to a blocking error, because the radar does not detect any objects.
