Overview
Exoskeleton robots have broad applications in rehabilitation, industrial assistance, and military domains. This project implements a complete ankle exoskeleton control system, recently upgraded with a ROS1 → ROS2 migration and hardware architecture redesign.
v2.0 Major Upgrade: Full migration from ROS1 Melodic (Ubuntu 18.04) to ROS2 Humble (Ubuntu 22.04). CAN architecture rewritten, IMU protocol upgraded, controller capabilities massively expanded.
Architecture
The system runs on Ubuntu 22.04 + ROS2 Humble, built with colcon.
can_ankle — 5-Mode Adaptive Gait Controller
The core control package has evolved from simple torque/velocity control to a complete 5-mode state machine adaptive gait controller:
State Machine:
STAND_MODE → TORQUE_MODE → PRE_TORQUE_MODE → TORQUE_DRIVE_MODE → VELOCITY_MODE → STAND_MODEKey Features:
- Adaptive Pace Estimation: Real-time pace calculation from stance phase time via exponential model
pace = -ln((t2-c1)/a1) / b1 - PID Auto-tuning: Kp/Ki/Kd dynamically adjusted across 5 pace brackets (Kp range 20-60)
- Slope-Assist Torque: Estimates ground slope from IMU quaternion z-component, computes
assist_torque = 8/π * atan(slope/2) - Floating Compensation: Dynamic adjustment based on theoretical vs actual swing time difference
- Two Control Modes: Mode 1 — cosine torque curve + adaptive rise/fall; Mode 2 — fixed 0.18s/0.21s curve
- Support-Phase Position Compensation: Alternating cycle position recording with return correction
CAN Bus — Dual-Protocol Redesign
Upgraded from direct VCI_USBCAN2 calls to a dual-layer architecture.
- Hardware: CANalyst-II (USB
04d8:0053, 1 Mbps), replacing old USBCAN2 - Motor: CANopen Node 83, SDO COB-ID
0x653 - Layer 1:
can_bridge.py— python-can + canalystii, publishes/can_rx/ subscribes/can_tx - Layer 2: C++ embedded CAN subprocess via
posix_spawn()+ bidirectional pipes
fdilink_ahrs — IMU Protocol Upgrade: FC → 5A 5A
| Aspect | Old | New |
|---|---|---|
| Header | FC | 0x5A 0xA5 |
| Frame | Variable | 82 bytes (2H+2L+76B+2T) |
| Baud Rate | 921600 | 115200 |
| Firmware | Legacy | v1.6.8+ (2025-07-17) |
Publishes 7 ROS2 Topics (up from ~3):
/imu (Eigen quaternion rotation), /euler_angles, /mag_pose_2d, /magnetic, /gps/fix, /system_speed, /NED_odometry
New TF Broadcaster (imu_tf.cpp): world → gyro_link with configurable offset.
Force Sensor — Modbus RTU Redesign
Complete redesign from ASCII text protocol to industrial Modbus RTU: Function Code 0x03, Register 0x0FA0/0x0FA1, Slave ID 1, CRC16 validation, configurable scale factor, 20Hz loop, debug toggle.
New Nodes
| Node | Function |
|---|---|
serial_sendCommand_node | Foot switch serial read + gait phase timing (6 topics) |
serial_encoder_node | Modbus RTU encoder read |
storeTopicMSG_node | Gait phase data to file |
storeVelMSG_node | Encoder angle/torque to file |
can_test_node | CAN sinusoidal velocity test |
imu_tf | IMU coordinate TF broadcast |
Safety Features
Encoder limit (±45°), force overload (300N), standing timeout (>5s), command sequence validation, cmd_vel timeout auto-stop.