Feature: Dynamically change polygons in collision monitor

[tonynajjar]

Since the collision monitor is supposed to replace a safety scanner, I think it would make sense to emulate field set switching by subscribing to polygons.

Typically fieldsets would change according to speed/steering angle. one could write a separate node that subscribes to speed/steering angle and publishes which fieldset/polygon should be active.

Question here is: does it undermine the safety aspect of the collision monitor?

[SteveMacenski]

is supposed to replace a safety scanner

It is not supposed to replace a safety scanner, to be clear. It is a collision monitor which is not certified as a replacement for any safety equipment. I need to repeat that anytime something like that is said, using those particular words. I think you know what I mean here :wink:

I'm not entirely clear what you're asking for. The polygons used are published that can be subscribed to. Are you asking for the ability to dynamically change the polygons?

[tonynajjar]

Gotcha, wrong wording, I did see the discussion about that on Discourse.

Anyway, yes I mean to dynamically change polygons. Updated title

[SteveMacenski]

Sure, yeah, I think that sounds reasonable. Your choices would be via dynamic parameters, topics, or services. What do you think there?

I might not tell people that's the recommended action, but certainly would be reasonable to have supported

Edit: or do you mean disabling/enabling several different pre-established polygons? Services there would make alot of sense.

[tonynajjar]

Edit: or do you mean disabling/enabling several different pre-established polygons? Services there would make alot of sense.

Mmm, no I was actually thinking new unconfigured polygons for greater flexibility.

Your choices would be via dynamic parameters, topics, or services

Yeah good question. I would think topics because of the potentially high frequency of change (e.g if the switching is dependent on speed and steering angle). As far as I know topics would offer the least latency, but I might be wrong with that assumption.

[AlexeyMerzlyakov]

In Collision Monitor, we have already subscribing on footprints in case of APPROACH behavior model. So, I do not see any obstacle to have an ability to subscribe to any arbitrary polygon for the rest of models (STOP and SLOWDOWN). In my opinion, topics is a good option for that. Maybe anyone have another thoughts, why the services in this case might be preferable over geometry_msgs/msg/Polygon (or PolygonStamped) messages?

[vinnnyr]

+1 for topics. We too have a custom variant of this feature living elsewhere in the system, and like stated @tonynajjar stated here:

Typically fieldsets would change according to speed/steering angle.

we change the "zones" based on the current speed and current steering angle of our robot, maybe at a rate near 10hz. I don't know if it makes sense hitting a service at quite that rate.

[SteveMacenski]

Topics seems reasonable to me :+1:

This should be a relatively straight forward contribution for someone interested :smile: Just need to expose a subscriber inside of the polygon class for changes in the stop/slow modes for overriding the polygon. Probably also a parameter for whether to use a parameter-defined static polygon or a dynamically changing one via a topic (but not both).

[AlexeyMerzlyakov]

Good. The major thing here was agreed: The current functionality of polygons in the Collision Monitor to be enhanced by subscribing to the topics: the similar way as APPROACH model utilizes. Current functionality with strictly-defined polygon will be intact. This could be reached e.g. by adding a new polygon_topic parameter. If this parameter is not set, using points array with polygon vertexes. Otherwise - subscribing to the polygon topic.

I'll could add this functionality in next CM update.

[tonynajjar]

Thank you very much!

[doisyg]

Just to state that we just tested this new feature (mainly @kaichie) and that is exactly what we were looking for.

[mbed92]

Does that functionality work on Humble? I need something like that to dynamically change polygons, but I cannot get it to work - params polygon_sub_topic (and polygon_topic) simply do not exist. I'm using the newest release, 1.1.8. However, polygon_sub_topic is mentioned even in polygon documentation