Paxini Sensor Community & FAQ
Frequently asked questions on mounting, calibration, ROS2 integration, and data interpretation. Links to research, documentation, and the SVRC forum.
Frequently Asked Questions
What sensor variants are available in the GEN3 family?
The GEN3 family ships in three anatomical form factors across multiple size and tier options. Fingertip (DP) variants range from 13 mm to 30 mm diameter (7 variants: Core, Elite, and Omega tiers). Finger-pad (IP/CP) variants are flat or curved pads from 16×10 mm to 53×25 mm (4 variants). The palm (MC) variant is a 20×20 mm Elite module. See Specifications for the complete variant table with part numbers and XLSX coordinate files.
Which variant fits the LinkerBot O6 / Wuji Hand fingertips?
The 13 mm variants (PX6AX-GEN3-DP-S1813-Core and S1813-Elite) are dimensioned for compact dexterous hand fingertips. The 15 mm (S2015-Elite) and 16 mm (S2716-Core) variants also work for slightly larger fingertip caps. The S3013-Core provides an integrated fingertip+pad in a single 13 mm module for hands with limited mounting area. Consult your hand's fingertip CAD model to confirm fit before ordering.
How do I choose the right communication board?
For single-sensor prototyping or evaluation, use the single-channel serial converter board — it is the simplest to set up and works directly with PXSR and pyserial. For full-hand deployments with multiple fingertip sensors, use the 10-channel SPI hub, which multiplexes up to 10 sensors over a single USB connection. The high-speed integrated board is for custom deployments requiring lower latency or higher aggregate sampling rates than the SPI hub provides.
How do I calibrate the sensor after remounting?
Any time the sensor is remounted, zero the baseline in PXSR before collecting data: ensure the sensor face is completely unloaded, then click Calibrate → Zero Baseline. PXSR averages 100 frames and stores the per-taxel and per-axis offsets. On Linux without PXSR, implement a startup calibration in your Python bridge that reads N frames at rest and subtracts the mean as an offset. See Setup Step 4 for the full calibration procedure.
What does the XLSX signal coordinate file do and how do I use it?
Each GEN3 variant ships with an XLSX file (e.g., PXSR-STDDP03B.xlsx for the 26 mm fingertip) that maps each taxel's raw linear index to physical (x, y) coordinates in millimetres relative to the sensor centre. This is required for spatially-accurate heatmap rendering, contact centroid computation, and contact area estimation. Load it in PXSR via File → Open Coordinate Map. In custom code, read the XLSX rows to build an index-to-position lookup table — then convert your flat taxel array to a 2D pressure image.
How do I integrate the GEN3 with ROS2?
Use pyserial to read frames from the communication board's USB-serial port and publish them on a ROS2 topic. The Setup Guide Step 6 contains a complete skeleton node. For the single-channel serial converter, open the port at the baud rate specified in the PaXini GEN3 Communication Protocol v1.0.5 document (included in the product bundle). Parse the frame per the protocol spec to extract the 6-axis F/T values and flat taxel array. Publish as a std_msgs/String (JSON) or a custom message type for downstream nodes.
How do I integrate the GEN3 with the Fearless Platform for episode recording?
Run your Python bridge script to open a USB connection to the communication board, then connect to the Fearless Platform WebSocket at /api/teleop/ws. Send the registration handshake with device_type: "tactile_sensor" and capabilities: ["tactile", "force_torque", "telemetry"]. Once the platform responds with type: "ready", stream telemetry frames containing the 6-axis F/T values, taxel array, and Unix millisecond timestamp. The platform records all frames synchronously with joint and camera streams in a JSONL episode archive. See the Developer Wiki for the full telemetry frame format.
PXSR shows no device — what do I check?
First confirm the communication board power LED is lit. Then: (1) try a different USB cable and port, (2) re-run the PXSR installer as Administrator to re-register the USB driver, (3) check Device Manager for the board under "Ports (COM & LPT)" — if it appears as an unknown device, the driver did not install. If the board appears correctly but PXSR still shows no device, verify the sensor ribbon is fully seated on both ends and the board is connected to the sensor before being plugged into USB.
How do I interpret the 6-axis F/T data for grasp control?
Fz (normal force) represents the pressing force perpendicular to the sensor face — the primary grasp force. Fx and Fy (shear forces) indicate lateral contact loads, which increase during slip onset. A rising |Fx| or |Fy| while Fz is constant is an early slip indicator. Tz (torque about normal axis) increases when the contacted object rotates within the grasp. For grasp stability monitoring, compute the friction cone constraint: grasp is stable when sqrt(Fx² + Fy²) / Fz is below the coefficient of friction between the sensor surface and the object material (typically 0.3–0.6 for rubber-on-metal contact).
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