Control robotic arms for automated pick-and-place operations, positioning, and test fixture manipulation.
Import
from lager.arm.rotrics import Dexarm
# For exception handling
from lager.arm.arm_net import ArmBase, MovementTimeoutError
The lager.arm module’s __init__.py is empty. Import Dexarm directly from lager.arm.rotrics.
Methods
| Method | Description |
|---|
position() | Get current arm position (x, y, z) |
move_to() | Move to absolute coordinates |
delta() | Move relative to current position |
go_home() | Return arm to home position |
enable_motor() | Enable arm motors |
disable_motor() | Disable arm motors |
read_and_save_position() | Save current position to memory |
get_current_position() | Get full position including joint angles |
sliding_rail_init() | Initialize the sliding rail |
Method Reference
Dexarm(port, serial_number)
Create a Dexarm robotic arm instance.
from lager.arm.rotrics import Dexarm
# Auto-detect arm
with Dexarm() as arm:
print(arm.position())
# Specify serial port
with Dexarm(port='/dev/ttyACM0') as arm:
print(arm.position())
# Specify by serial number
with Dexarm(serial_number='ABCD1234') as arm:
print(arm.position())
| Parameter | Type | Description |
|---|
port | str | Serial port path (optional, auto-detected) |
serial_number | str | USB serial number for identification |
Dexarm instance (context manager supported)
position()
Get the current arm position.
x, y, z = arm.position()
print(f"Position: X={x}, Y={y}, Z={z}")
tuple[float, float, float] - (x, y, z) coordinates in mm
move_to(x, y, z, timeout=5.0)
Move the arm to absolute coordinates with blocking wait.
# Move to specific position
arm.move_to(100, 200, 50)
# Move with longer timeout
arm.move_to(100, 200, 50, timeout=10.0)
| Parameter | Type | Description |
|---|
x | float | Target X coordinate (mm) |
y | float | Target Y coordinate (mm) |
z | float | Target Z coordinate (mm) |
timeout | float | Maximum wait time in seconds (default: 5.0) |
MovementTimeoutError if position not reached within timeout
delta(dx=0, dy=0, dz=0, timeout=5.0)
Move relative to current position.
# Move 10mm in X direction
new_x, new_y, new_z = arm.delta(dx=10)
# Move diagonally
new_x, new_y, new_z = arm.delta(dx=10, dy=10, dz=-5)
| Parameter | Type | Description |
|---|
dx | float | Relative X movement (mm) |
dy | float | Relative Y movement (mm) |
dz | float | Relative Z movement (mm) |
timeout | float | Maximum wait time (default: 5.0) |
tuple[float, float, float] - New (x, y, z) position after move
go_home()
Return the arm to its home position (X=0, Y=300, Z=0).
enable_motor()
Enable the arm motors.
disable_motor()
Disable the arm motors (arm will be loose).
read_and_save_position()
Save the current position to the arm’s internal memory.
arm.read_and_save_position()
get_current_position()
Get the full position including joint angles.
x, y, z, e, a, b, c = arm.get_current_position()
print(f"Cartesian: ({x}, {y}, {z})")
print(f"Joint angles: A={a}, B={b}, C={c}")
tuple[float, ...] - (x, y, z, e, a, b, c) where a, b, c are joint angles
End Effector Methods
Soft Gripper
arm.soft_gripper_pick() # Activate gripper to pick
arm.soft_gripper_place() # Release gripper to place
arm.soft_gripper_nature() # Return to neutral state
arm.soft_gripper_stop() # Stop gripper action
Air Picker
arm.air_picker_pick() # Activate vacuum to pick
arm.air_picker_place() # Release vacuum to place
arm.air_picker_nature() # Return to neutral state
arm.air_picker_stop() # Stop vacuum action
Laser Module
arm.laser_on(value=0) # Turn laser on with power level
arm.laser_off() # Turn laser off
Conveyor Belt Methods
arm.conveyor_belt_forward(speed=0) # Move belt forward (speed 0-100)
arm.conveyor_belt_backward(speed=0) # Move belt backward (speed 0-100)
arm.conveyor_belt_stop() # Stop belt
Sliding Rail Methods
arm.sliding_rail_init() # Initialize the sliding rail
Utility Methods
delay_ms(value) / delay_s(value)
Add delay to the arm’s command queue.
arm.delay_ms(500) # 500ms delay
arm.delay_s(2) # 2 second delay
set_acceleration(acceleration, travel_acceleration, retract_acceleration=60)
Configure acceleration settings.
arm.set_acceleration(100, 100, 60)
set_module_type(module_type)
Set the attached module type.
# 0=PEN, 1=LASER, 2=PNEUMATIC, 3=3D
arm.set_module_type(0) # Set to PEN module
get_module_type()
Get the currently detected module type.
module = arm.get_module_type()
print(f"Module: {module}") # 'PEN', 'LASER', 'PUMP', or '3D'
Examples
Basic Movement
from lager.arm.rotrics import Dexarm
with Dexarm() as arm:
# Go to home position
arm.go_home()
# Get current position
x, y, z = arm.position()
print(f"Home position: ({x}, {y}, {z})")
# Move to test position
arm.move_to(100, 250, 0)
# Move up
arm.delta(dz=50)
# Return home
arm.go_home()
Pick and Place
from lager.arm.rotrics import Dexarm
with Dexarm() as arm:
arm.go_home()
# Move to pick position
arm.move_to(100, 200, 50) # Above target
arm.delta(dz=-30) # Lower to pick height
# Pick up object
arm.soft_gripper_pick()
arm.delay_ms(500)
# Lift
arm.delta(dz=30)
# Move to place position
arm.move_to(150, 200, 50)
arm.delta(dz=-30)
# Place object
arm.soft_gripper_place()
arm.delay_ms(500)
# Return home
arm.delta(dz=30)
arm.go_home()
Automated Test Positioning
from lager.arm.rotrics import Dexarm
from lager import Net
from lager.pcb.constants import NetType
# Test positions for probe points
PROBE_POSITIONS = [
(100, 200, -10), # Test point 1
(120, 200, -10), # Test point 2
(140, 200, -10), # Test point 3
]
with Dexarm() as arm:
arm.go_home()
adc = Net.get('PROBE', type=NetType.ADC)
results = []
for i, (x, y, z) in enumerate(PROBE_POSITIONS):
# Move above position
arm.move_to(x, y, z + 20)
# Lower probe
arm.move_to(x, y, z)
arm.delay_ms(200) # Settle time
# Take measurement
voltage = adc.input()
results.append((i, voltage))
print(f"Point {i}: {voltage}V")
# Lift
arm.delta(dz=20)
arm.go_home()
Error Handling
from lager.arm.rotrics import Dexarm
from lager.arm.arm_net import MovementTimeoutError
try:
with Dexarm() as arm:
arm.move_to(100, 200, 50, timeout=3.0)
except MovementTimeoutError:
print("Arm movement timed out - check for obstructions")
except RuntimeError as e:
print(f"Arm not found or cannot be opened: {e}")
except Exception as e:
print(f"Error: {e}")
Supported Hardware
| Manufacturer | Model | Features |
|---|
| Rotrics | Dexarm | 4-axis, multiple end effectors, conveyor support |
Exceptions
| Exception | Module | Description |
|---|
MovementTimeoutError | lager.arm.arm_net | Arm didn’t reach target position in time |
RuntimeError | builtin | Arm device not found or cannot be opened |
Notes
- Always use the context manager (
with statement) to ensure proper cleanup
- The arm must be homed before accurate movements
- Movement timeout errors may indicate obstructions or out-of-bounds coordinates
- Joint angles (a, b, c) are in the arm’s internal coordinate system
- Default tolerance for position verification is 0.5mm
- The arm auto-detects via USB VID/PID (0x0483:0x5740)
