Replace serialized detected object mergers to reduce complexity

[technolojin]

Checklist

• I've read the contribution guidelines.
• I've searched other issues and no duplicate issues were found.
• I've agreed with the maintainers that I can plan this task.

Description

The current object tracker consists of object mergers, trackers, and tracking-merger. However, there are several issues with the current process:

1. The merged object takes the worst latency of all detectors.
2. Introducing a new detector to the pipeline can be complicated.
3. It is difficult to inspect faulty object detection/association due to the complexity of the merge process.

Here is the perception diagram. The object merger is highlighted as a red box.

Based on the current launcher, the structure inside is as following.

The object_association_merger is used 2 or 3 times. Depends on which detection mode is selected (option switches are marked as pink diamond), the input also changes.

Purpose

The purpose of this task is to:

• Mitigate the complexity of the perception launcher (perception pipeline configurations)
• Simplify the detection merge process, association process, and tracker existence management
• Reduce perception pipeline latency
• Provide redundancy in case of sensor/detection failure

Possible approaches

To achieve the goal, the following components will be developed and implemented in the multi_object_tracker:

• Channel configuration: Provide all available sources of detections.
• Input manager: Manage multiple detected object message channels.
• Process timing algorithm: Operate the tracking process in an optimal set of objects to reduce latency.
• Existence model: Model the existence probability of each detection source to understand the contributions of detections.
• Debugger: Visualize association results and existence probability on each channel.

Definition of done

• Enable the multi_object_tracker to subscribe to single or multiple detected objects.
• Ensure that it works the same way if the merged detection objects message is set as a single source.