Flow Base API

The Flow Base SDK has two layers:

Class	Location	Use
Vehicle	flow_base_controller.py	Runs on-board the Pi — joystick demo
FlowBaseClient	flow_base_client.py	Runs remotely — network Python API

FlowBaseClient

For remote control from your development machine.

from i2rt.flow_base.flow_base_client import FlowBaseClient

client = FlowBaseClient(
    host: str = "172.6.2.20",
    port: int = 11323,
    with_linear_rail: bool = False,
)

Parameter	Description
host	IP address of the Flow Base Pi
port	API server port (default 11323)
with_linear_rail	Set True if the linear rail module is installed

---

Movement Commands

set_target_velocity(velocity, frame)

# 3D (base only)
client.set_target_velocity([vx, vy, omega], frame="local")

# 4D (base + linear rail)
client.set_target_velocity([vx, vy, omega, rail_vel], frame="local")

Parameter	Unit	Description
vx	m/s	Forward/backward
vy	m/s	Left/right (strafe)
omega	rad/s	Rotation (yaw rate)
rail_vel	rad/s	Linear rail speed (positive = up)
frame	—	"local" (relative to base) or "global" (world frame)

Velocity timeout

The base stops automatically if no command arrives within 0.25 seconds. FlowBaseClient maintains a heartbeat automatically while connected.

---

Odometry

get_odometry() → dict

odom = client.get_odometry()
# {'translation': array([x, y]), 'rotation': array(theta)}

Wheel odometry only. Errors accumulate over time — integrate visual odometry (RealSense T265, ZED) for precise localization.

reset_odometry() → None

Resets position and heading to zero.

---

Linear Rail API

Only available when with_linear_rail=True.

get_linear_rail_state() → dict

state = client.get_linear_rail_state()
# {'position': float, 'velocity': float, 'limit_switches': [bool, bool]}

set_linear_rail_velocity(velocity: float) → None

client.set_linear_rail_velocity(0.05)   # raise slowly
client.set_linear_rail_velocity(0.0)    # stop
client.set_linear_rail_velocity(-0.05)  # lower

Auto-homing

The rail homes to the lower limit switch on init. Ensure clearance below before powering on.

---

Command-line Client

Quick functional tests without writing Python:

# Read odometry
python i2rt/flow_base/flow_base_client.py --command get_odometry --host 172.6.2.20

# Reset odometry
python i2rt/flow_base/flow_base_client.py --command reset_odometry --host 172.6.2.20

# Run a short movement test (⚠️ base will move)
python i2rt/flow_base/flow_base_client.py --command test_command --host 172.6.2.20

# Test linear rail (⚠️ rail will move)
python i2rt/flow_base/flow_base_client.py --command test_linear_rail --host 172.6.2.20

---

Vehicle (On-board Controller)

Runs directly on the Pi. Used for the joystick demo.

from i2rt.flow_base.flow_base_controller import Vehicle
import time

v = Vehicle()
v.start_control()

start = time.time()
while time.time() - start < 2.0:
    v.set_target_velocity((0.15, 0.0, 0.0), frame="local")

Speed and acceleration limits are configurable in flow_base_controller.py (lines 500–501).

---

Coordinate Frames

Frame	Description
local	Relative to the current base orientation. Joystick forward = robot forward regardless of heading.
global	World frame from odometry zero. Similar to drone headless mode. Accumulates error.

Switch frames at runtime via the remote Mode button, or programmatically by passing frame= to set_target_velocity.