Chapter 7: Implementation & Integration

弘익人間 (홍익인간) · Benefit All Humanity

7.1 System Architecture

Implementing a complete humanoid robot system requires integrating mechanical, electrical, software, and safety subsystems into a cohesive whole. WIA-ROB-019 defines standard architectures enabling modular development and interoperability.

7.1.1 Hardware Architecture

Typical hardware architecture consists of:

Distributed Computing Nodes

Network Topology

Computers connected via high-speed networks:

7.1.2 Software Architecture

Layered software architecture:

Operating System Layer

Middleware Layer

ROS 2 (Robot Operating System 2) is the de facto standard for robot software:

Application Layer

Robot-specific application software:

7.2 Sensor Integration

7.2.1 Sensor Drivers

Each sensor requires driver software:

7.2.2 Time Synchronization

Critical for sensor fusion:

7.2.3 Calibration Data Management

Store and load sensor calibrations:

7.3 Actuator Integration

7.3.1 Motor Driver Configuration

Configure motor drivers for each joint:

7.3.2 Control Loop Tuning

Tune controller gains for performance:

Position Control Tuning

Torque Control Tuning

7.3.3 Safety Integration

Integrate actuator safety features:

7.4 Control Implementation

7.4.1 Real-Time Control Loop

Structure of main control loop:

void control_loop() {
    initialize_system();
    while (running) {
        // 1. Read sensors (1-2 ms)
        read_joint_encoders(&joint_positions, &joint_velocities);
        read_imu(&imu_data);
        read_force_torque_sensors(&foot_forces);

        // 2. State estimation (2-3 ms)
        estimate_base_pose(&base_position, &base_orientation);
        update_robot_state();

        // 3. Control computation (3-5 ms)
        compute_desired_com_trajectory();
        compute_zmp_controller(&desired_joint_torques);
        apply_gravity_compensation(&desired_joint_torques);

        // 4. Safety checks (1 ms)
        check_joint_limits();
        check_force_limits();
        if (safety_violation) {
            trigger_protective_stop();
        }

        // 5. Send commands (1 ms)
        send_joint_commands(&desired_joint_torques);

        // 6. Wait for next cycle
        wait_for_next_period(); // 1 kHz cycle = 10 ms period
    }
}

Timing budget for 1 kHz control (10ms period):

Use real-time profiling to verify timing. If exceeding budget, optimize or reduce control frequency.

7.4.2 Multi-Rate Control

Different control tasks run at different rates:

Implement using hierarchical control structure. Fast loops inside slow loops. Ensure data consistency when slower loop updates reference for faster loop.

7.4.3 Controller State Machine

Manage transitions between behaviors:

States:
- INITIALIZATION: System startup, homing, calibration
- IDLE: Standing still, ready for commands
- WALKING: Executing walking gait
- MANIPULATION: Reaching, grasping, manipulating
- RECOVERY: Balance recovery, protective reactions
- ERROR: Fault detected, safe stop

Transitions:
INITIALIZATION → IDLE: When initialization complete
IDLE → WALKING: On walk command
WALKING → IDLE: On stop command or destination reached
IDLE → MANIPULATION: On manipulation command
MANIPULATION → IDLE: On task complete
Any → RECOVERY: On balance disturbance detected
Any → ERROR: On safety fault detected
ERROR → IDLE: On fault cleared and manual reset

State machine ensures clean transitions, prevents conflicting behaviors, handles errors gracefully.

7.5 Perception Integration

7.5.1 Vision Pipeline Deployment

Deploy deep learning models on edge GPU:

7.5.2 Sensor Fusion Implementation

Combine data from multiple sensors:

Localization Fusion

Object Detection Fusion

7.5.3 Perception-Control Interface

Bridge perception and control systems:

7.6 System Integration Testing

7.6.1 Hardware-in-Loop (HIL) Testing

Test control software with real hardware before full integration:

7.6.2 Simulation and Validation

Extensive testing in simulation before hardware tests:

7.6.3 Integration Test Progression

Systematic integration approach:

  1. Standing: First goal is stable standing. Verify balance control, state estimation, sensor integration. Robot suspended by harness initially.
  2. Weight Shifting: Shift weight side-to-side. Test single support balance, foot force distribution.
  3. Stepping in Place: Lift and place feet without forward motion. Validate swing leg control, transition to double support.
  4. Walking Forward: Short forward steps (0.1-0.2m). Gradually increase step length, speed. Maintain safety harness.
  5. Turning: In-place turning, curved paths. Test lateral stability, footstep planning.
  6. Obstacle Navigation: Step over obstacles, walk around. Test perception integration, adaptive planning.
  7. Manipulation: Reaching, grasping while standing. Then combine with walking (approach, grasp, carry).
  8. Stairs and Slopes: Advanced locomotion. Test perception of terrain, adaptive gait.
  9. Disturbance Rejection: Push robot (controlled forces). Verify recovery strategies. Gradually increase disturbance magnitude.

7.7 WIA Ecosystem Integration

7.7.1 WIA-INTENT Integration

Natural language control via WIA-INTENT:

7.7.2 WIA-OMNI-API Integration

Universal API gateway for external integration:

7.7.3 WIA-SOCIAL Integration

Multi-robot coordination:

7.8 Deployment and Field Testing

7.8.1 Pilot Deployment

Before full production deployment:

7.8.2 Performance Monitoring

Monitor robot performance in deployment:

7.8.3 Maintenance and Updates

Keep robot operating well:

7.9 Chapter Summary

This chapter covered implementation and integration of humanoid robot systems. We examined system architecture (hardware and software), sensor integration including drivers and calibration, actuator integration and control loop implementation, perception deployment with sensor fusion, comprehensive integration testing from simulation to real-world validation, WIA ecosystem integration for natural language control and cloud connectivity, and deployment strategies with performance monitoring and maintenance.

Successful integration requires careful attention to detail, systematic testing, and iterative refinement. The specifications and best practices in WIA-ROB-019 guide engineers through this complex process, reducing risk and accelerating development.

In Chapter 8, we'll look ahead to future directions in humanoid robotics—emerging technologies, research frontiers, and transformative applications on the horizon.