S.A.A.R: Design and Implementation of a 12-DOF Quadruped Robot Using ROS 2 Humble, Raspberry Pi 4B, and Inverse Kinematics-Based Crawl Gait with Stand, Sit, and Walk Behaviours

This paper presented S.A.A.R, a 12-DOF quadruped robot controlled by a Raspberry Pi 4B running ROS 2 Humble. The S.A.A.R Driver implements four validated motion behaviours — Stand Up, Sit Down, Crawl/Walk (SLP gait), and Rest — through a layered software architecture. Power is provided by an 11.4 V 2200 mAh Li-Po battery through a 20 A buck converter to twelve 25 kg/cm servo motors. IK instability during crawl locomotion was systematically attributed to link length parameter mismatch, body frame torsional compliance, and absence of closed-loop feedback. Stand Up and Sit Down transitions were successful, confirming correctness of the joint-space interpolation approach. Future work: (1) Kinematic Calibration — measure actual link lengths, update IK parameters; (2) IMU Feedback — MPU-6050 for body-tilt compensation; (3) Trajectory Smoothing — cubic Bézier curves for foot swing paths; (4) Advanced Gaits — trot gait via Central Pattern Generator (CPG); (5) Reinforcement Learning — sim-to-real policy in Gazebo/PyBullet for terrain-adaptive locomotion.

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