Six-Axis Force/Torque Sensor
六维力传感器
What Is a Six-Axis Force/Torque Sensor?
A six-axis force/torque sensor (6-axis F/T sensor) measures three orthogonal forces (Fx, Fy, Fz) and three torques (Mx, My, Mz) at one point, typically using strain gauges or capacitive elements. Range, accuracy, and sample rate should be confirmed from the selected sensor's datasheet.
Where It Goes and What It Does
- Wrist: between the arm flange and the tool, for precision assembly, polishing/deburring, and hand-guided teaching — any force-control task that needs true end-effector contact forces;
- Ankle: on humanoid feet, measuring ground reaction force and center of pressure (ZMP/CoP), a key input for walking balance;
- Test rigs: torque calibration of joint actuators, impact testing.
Do You Still Need One If the Joint Does Current-Based Force Control?
Quasi-direct-drive (QDD) joints can estimate output torque from phase current after motor and drivetrain calibration. This can support joint-level compliance, but accuracy depends on friction, temperature, efficiency, and model error. A practical comparison is:
| Scenario | Current-based estimation (QDD) | External 6-axis F/T sensor |
|---|---|---|
| Leg impact absorption, whole-body compliance | Useful control feedback; accuracy depends on calibration | Fit according to control and safety needs |
| Precision assembly | Does not directly measure six-axis tool forces | Usually the better fit |
| Foot ZMP / ground reaction force | Indirect estimate only | Direct and reliable |
| Hardware and integration | No dedicated joint sensor added | Adds sensing, calibration, and cabling |
One-line verdict: QDD current estimation supports joint-level compliance, while six-axis F/T sensors directly measure tool or foot loads. They can be combined according to accuracy and safety requirements.