Tutorial 04: Multi-Motor Control

Prerequisites

Completed Tutorial 03: Mode Switch and Control
Multiple motors connected and identified

Same Vendor, Same Controller

For motors from the same vendor, use one controller:

from motorbridge import Controller, Mode

with Controller("can0") as ctrl:
    # Add multiple Damiao motors
    m1 = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    m2 = ctrl.add_damiao_motor(0x02, 0x12, "4340P")
    m3 = ctrl.add_damiao_motor(0x03, 0x13, "4340P")

    # Enable all at once
    ctrl.enable_all()

    # Set modes individually
    m1.ensure_mode(Mode.MIT, 1000)
    m2.ensure_mode(Mode.MIT, 1000)
    m3.ensure_mode(Mode.MIT, 1000)

Different Vendors, Separate Controllers

For mixed vendor setups, use separate controllers:

from motorbridge import Controller, Mode

# Damiao motors
with Controller("can0") as dm_ctrl:
    dm = dm_ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    dm_ctrl.enable_all()

    # RobStride motors (different controller on same bus)
    with Controller("can0") as rs_ctrl:
        rs = rs_ctrl.add_robstride_motor(127, 0xFD, "rs-06")
        rs_ctrl.enable_all()

        # Control both
        dm.send_mit(0.5, 0.0, 30.0, 1.0, 0.0)
        rs.send_mit(0.3, 0.0, 2.0, 0.1, 0.0)

Do not mix vendors in the same Controller instance. Each vendor has a different protocol implementation.

Dictionary-Based Motor Management

Use dictionaries for organized motor access:

from motorbridge import Controller, Mode

# Configuration
MOTOR_CONFIG = {
    "front_left_hip": {"motor_id": 0x01, "feedback_id": 0x11, "model": "4340P"},
    "front_left_knee": {"motor_id": 0x02, "feedback_id": 0x12, "model": "4340P"},
    "front_right_hip": {"motor_id": 0x03, "feedback_id": 0x13, "model": "4340P"},
    "front_right_knee": {"motor_id": 0x04, "feedback_id": 0x14, "model": "4340P"},
}

with Controller("can0") as ctrl:
    # Create motor handles
    motors = {}
    for name, cfg in MOTOR_CONFIG.items():
        motors[name] = ctrl.add_damiao_motor(
            cfg["motor_id"],
            cfg["feedback_id"],
            cfg["model"]
        )

    # Enable all
    ctrl.enable_all()

    # Set modes
    for motor in motors.values():
        motor.ensure_mode(Mode.MIT, 1000)

    # Send commands by name
    motors["front_left_hip"].send_mit(0.5, 0.0, 30.0, 1.0, 0.0)
    motors["front_left_knee"].send_mit(-0.3, 0.0, 30.0, 1.0, 0.0)

Batch Feedback Query Pattern

Efficiently query all motor states:

import time
from motorbridge import Controller, Mode

with Controller("can0") as ctrl:
    motors = [ctrl.add_damiao_motor(i, 0x10+i, "4340P") for i in range(1, 5)]
    ctrl.enable_all()

    for i in range(100):
        # Request all feedbacks
        for m in motors:
            m.request_feedback()

        # Single poll for all
        ctrl.poll_feedback_once()

        # Read all states
        states = [m.get_state() for m in motors]

        # Print summary
        for j, state in enumerate(states):
            if state:
                print(f"Motor {j+1}: pos={state.pos:.3f}")

        time.sleep(0.02)

Coordinated Motion

Synchronized Motion

import time
import math
from motorbridge import Controller, Mode

with Controller("can0") as ctrl:
    m1 = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    m2 = ctrl.add_damiao_motor(0x02, 0x12, "4340P")

    ctrl.enable_all()
    m1.ensure_mode(Mode.MIT, 1000)
    m2.ensure_mode(Mode.MIT, 1000)

    # Synchronized sinusoidal motion
    for i in range(200):
        t = i * 0.02
        target = math.sin(t)

        # Same target for both
        m1.send_mit(target, 0.0, 30.0, 1.0, 0.0)
        m2.send_mit(target, 0.0, 30.0, 1.0, 0.0)

        time.sleep(0.02)

Alternating Motion

import time
import math
from motorbridge import Controller, Mode

with Controller("can0") as ctrl:
    m1 = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    m2 = ctrl.add_damiao_motor(0x02, 0x12, "4340P")

    ctrl.enable_all()
    m1.ensure_mode(Mode.MIT, 1000)
    m2.ensure_mode(Mode.MIT, 1000)

    # 180° phase difference
    for i in range(200):
        t = i * 0.02

        target1 = math.sin(t)
        target2 = math.sin(t + math.pi)  # Phase shift

        m1.send_mit(target1, 0.0, 30.0, 1.0, 0.0)
        m2.send_mit(target2, 0.0, 30.0, 1.0, 0.0)

        time.sleep(0.02)

Safety Monitoring

Monitor multiple motors for safety:

import time
from motorbridge import Controller, Mode

TEMP_LIMIT = 80.0
TORQUE_LIMIT = 10.0

def check_safety(states):
    """Check states for safety issues."""
    issues = []
    for name, state in states.items():
        if state is None:
            continue

        if state.t_mos > TEMP_LIMIT:
            issues.append(f"{name}: MOSFET overheat ({state.t_mos:.1f}°C)")
        if state.t_rotor > TEMP_LIMIT:
            issues.append(f"{name}: Rotor overheat ({state.t_rotor:.1f}°C)")
        if abs(state.torq) > TORQUE_LIMIT:
            issues.append(f"{name}: Over-torque ({state.torq:.2f} Nm)")
        if state.status_code != 0:
            issues.append(f"{name}: Error 0x{state.status_code:02X}")

    return issues

with Controller("can0") as ctrl:
    motors = {
        "m1": ctrl.add_damiao_motor(0x01, 0x11, "4340P"),
        "m2": ctrl.add_damiao_motor(0x02, 0x12, "4340P"),
    }

    ctrl.enable_all()

    try:
        for i in range(1000):
            # Send commands
            for motor in motors.values():
                motor.send_mit(0.5, 0.0, 30.0, 1.0, 0.0)

            # Read states
            states = {}
            for name, motor in motors.items():
                motor.request_feedback()
                states[name] = motor.get_state()

            # Safety check
            issues = check_safety(states)
            if issues:
                print("SAFETY ALERT:")
                for issue in issues:
                    print(f"  {issue}")
                ctrl.disable_all()
                break

            time.sleep(0.02)

    except KeyboardInterrupt:
        pass
    finally:
        ctrl.disable_all()

Performance Tips

Minimize CAN Overhead

# Bad: Multiple polls
for motor in motors:
    motor.request_feedback()
    ctrl.poll_feedback_once()  # Poll for each motor
    state = motor.get_state()

# Good: Single poll
for motor in motors:
    motor.request_feedback()
ctrl.poll_feedback_once()  # Single poll for all
for motor in motors:
    state = motor.get_state()

Maintain Loop Timing

import time

DT_S = 0.02  # 50Hz target

for i in range(100):
    t0 = time.time()

    # Control work
    # ...

    work_time = time.time() - t0
    if work_time < DT_S:
        time.sleep(DT_S - work_time)
    else:
        print(f"WARNING: Overrun! {work_time*1000:.1f}ms > {DT_S*1000:.1f}ms")

Complete Example

import time
import math
from motorbridge import Controller, Mode

def main():
    MOTORS = {
        "left_hip": {"id": 0x01, "fb": 0x11},
        "left_knee": {"id": 0x02, "fb": 0x12},
        "right_hip": {"id": 0x03, "fb": 0x13},
        "right_knee": {"id": 0x04, "fb": 0x14},
    }

    with Controller("can0") as ctrl:
        motors = {
            name: ctrl.add_damiao_motor(cfg["id"], cfg["fb"], "4340P")
            for name, cfg in MOTORS.items()
        }

        print("Enabling...")
        ctrl.enable_all()

        print("Setting mode...")
        for motor in motors.values():
            motor.ensure_mode(Mode.MIT, 1000)

        print("Running (Ctrl+C to stop)...")
        try:
            for i in range(500):
                t = i * 0.02

                # Generate targets
                targets = {
                    "left_hip": 0.3 * math.sin(t),
                    "left_knee": 0.5 * math.sin(t),
                    "right_hip": 0.3 * math.sin(t + 0.1),
                    "right_knee": 0.5 * math.sin(t + 0.1),
                }

                # Send commands
                for name, target in targets.items():
                    motors[name].send_mit(target, 0.0, 30.0, 1.0, 0.0)

                time.sleep(0.02)

        except KeyboardInterrupt:
            print("\nInterrupted")
        finally:
            print("Disabling...")
            ctrl.disable_all()

if __name__ == "__main__":
    main()

Next Steps

Tutorial 05: Register and Parameters - Motor parameter tuning
Best Practices - Production patterns
Controller API - Full API reference

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04 multi motor

Tutorial 04: Multi-Motor Control

Prerequisites

Same Vendor, Same Controller

Different Vendors, Separate Controllers

Dictionary-Based Motor Management

Batch Feedback Query Pattern

Coordinated Motion

Synchronized Motion

Alternating Motion

Safety Monitoring

Performance Tips

Minimize CAN Overhead

Maintain Loop Timing

Complete Example

Next Steps

​Tutorial 04: Multi-Motor Control

​Prerequisites

​Same Vendor, Same Controller

​Different Vendors, Separate Controllers

​Dictionary-Based Motor Management

​Batch Feedback Query Pattern

​Coordinated Motion

​Synchronized Motion

​Alternating Motion

​Safety Monitoring

​Performance Tips

​Minimize CAN Overhead

​Maintain Loop Timing

​Complete Example

​Next Steps

Tutorial 04: Multi-Motor Control

Prerequisites

Same Vendor, Same Controller

Different Vendors, Separate Controllers

Dictionary-Based Motor Management

Batch Feedback Query Pattern

Coordinated Motion

Synchronized Motion

Alternating Motion

Safety Monitoring

Performance Tips

Minimize CAN Overhead

Maintain Loop Timing

Complete Example

Next Steps