Joint Zero Calibration (Homing)

关节零位标定（回零）Common

Telling a robot exactly where “zero degrees” is for each of its joints.

Joint zero calibration is the process of establishing how each joint's encoder reading maps to the joint's true physical angle: the joint is moved to a known reference pose (a mechanical hard stop, a calibration fixture, or a specified zero posture), the encoder reading at that pose is recorded as an offset, and every later angle is computed relative to that zero point. Incremental encoders lose track of position when powered off, so the robot must be “homed” at startup; absolute encoders remember position but still need recalibrating after reassembly or after a motor or reducer is replaced. If the zero point is off, forward kinematics will compute the wrong end-effector position, and a policy trained on one robot may fail when moved to another — so this step is typically done first after any hardware change.

ExampleBefore first use, LeRobot's SO-101 arm requires running a calibrate command that moves each joint to a middle position and through its full range to record the zero point and joint limits.

Also called: Homing, Zero-Point Calibration
Related: Rotary Encoder · Absolute Encoder · Incremental Encoder · Kinematic Calibration · Forward Kinematics (FK) · SO-100 / SO-101 Arm
Sources: Rotary encoder - Wikipedia