Complex Events: Logic Gates & Fusion

In the previous tutorials, we triggered actions based on single, isolated conditions (e.g., “If Mapper Fails” or “If Person Seen”).

However, real-world autonomy is rarely that simple. A robot shouldn’t stop every time it sees an obstacle, maybe it only stops if it’s moving fast. It shouldn’t return home just because the battery is low, maybe it waits until it finishes its current task.

In this tutorial, we will use Logic Gates and Multi-Topic Fusion to create smarter, more robust reflexes.

Complex Condition Logic

Kompass allows you to compose complex triggers using standard Python bitwise operators. This effectively turns your Event definitions into a high-level logic circuit.

Logic	Operator	Description	Use Case
AND	&	All conditions must be True.	“Safety Checks” (Speed > 0 AND Obstacle Close)
OR	|	At least one condition is True.	“Redundancy” (Lidar Blocked OR Bumper Hit)
NOT	~	Inverts the condition.	“Exclusion” (Target Seen AND NOT Low Battery)

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Scenario: The “Smart” Emergency Stop (AND Logic)

The Problem: A naive emergency stop triggers whenever an object is within 0.5m. But if the robot is docking or maneuvering in a tight elevator, this stops it unnecessarily.

The Solution: We create a “Smart Stop” that triggers ONLY if: An obstacle is close (< 0.5m) AND The robot is moving fast (> 0.1 m/s)

1. Define Event Sources (Topics)

We need data from the Radar (perception) and Odometry (state).

from kompass.ros import Topic

# 1. Lidar (0.2s timeout for safety)
radar = Topic(name="/radar_front", msg_type="Float32", data_timeout=0.2)

# 2. Odometry (0.5s timeout)
odom = Topic(name="/odom", msg_type="Odometry", data_timeout=0.5)

2. Define The Composed Event

We combine the conditions using the & operator.

from kompass.ros import Event

# Condition A: Obstacle Close
is_obstacle_close = radar.msg.data < 0.3

# Condition B: Moving Fast (Linear X velocity)
is_robot_moving_fast = odom.msg.twist.twist.linear.x > 0.1

# Composed Event: BOTH must be True
event_smart_stop = Event(
    event_condition=(is_obstacle_close & is_robot_moving_fast),
    on_change=True
)