# PlatformFlyThrough

A cooperative control task where a group of `k` UAVs are connected together by a
rigid frame to form an overactuated platform. Each individual UAV, attached
by a 2-DoF passive gimbal joint, acts as a thrust generator.
The goal for the agents is to make the platform fly through the obstacles and reach at a reference pose
(position and attitude).

## Observation

The observation is a `CompositeSpec` containing the following items:

- `obs_self` (1, \*): The state of each UAV observed by itself, containing its kinematic
information with the position being relative to the frame center, and an one-hot
identity indicating the UAV's index.
- `obs_others` (k-1, \*): The observed states of other agents.
- `obs_frame`:
- `state_frame`: (1, \*): The state of the frame.
- `rpos` (3): The relative position of the platform to the reference positions.
- `time_encoding` (optional): The time encoding, which is a 4-dimensional
vector encoding the current progress of the episode.

## Reward

- `pos`: Reward for maintaining the final position of the payload around the target position.
- `up`: Reward for maintaining an upright orientation.
- `effort`: Reward computed from the effort of the drone to optimize the
energy consumption.
- `spin`: Reward computed from the spin of the drone to discourage spinning.
- `action smoothness`: Reward computed from the throttle difference of the drone.

The total reward is computed as follows:

```{math}
r = [r_\text{pos} + r_\text{pos} * (r_\text{up} + r_\text{spin}) + r_\text{effort} + r_\text{action smoothness}]
```

## Episode End

The episode ends when the drone gets too close, or when the drone goes too far away horizontally,
or when the maximum episode length is reached.

## Config

| Parameter               | Type  | Default       | Description |
| ----------------------- | ----- | ------------- | ----------- |
| `drone_model`           | str   | "Hummingbird" |             |
| `num_drones`            | int   | 4             |             |
| `arm_length`            | float | 0.85          |             |
| `reset_on_collision`    | bool  | False         |             |
| `reward_distance_scale` | float | 1.0           |             |
| `time_encoding`         | bool  | True          |             |
| `obstacle_spacing`      | float | 1.0           |             |