pHRI-CHAR-TACT: Character Dataset from Intrinsic Robot Tactile Sensing

The pHRI-CHAR-TACT dataset provides time-series data captured from an uninstrumented, 3D-printed touchpad interface mounted on the end-effector of a collaborative robot while users slide their finger to draw 36 characters ((26 letters and 10 digits)). This dataset facilitates research in intuitive robot control, physical human-robot collaboration, tactile sensing, and machine learning for touch recognition. It contains data collected using the intrinsic tactile sensing capabilities of a KUKA LBR iiwa 14 R820 robot, leveraging its joint torque sensors to interpret touch events on the touchpad. The dataset is presented in two versions:

• pHRI-CHAR-TACT_SingleUser: this dataset includes 4500 time series, with 150 samples corresponding to each character. All data was recorded from a single user interacting with the robot.
• pHRI-CHAR-TACT_MultipleUsers: this dataset also contains 4500 time series (150 per character), but the data was collected from three different users (2 female, 1 male; 2 right-handed, 1 left-handed). This version allows for the analysis of inter-user variability in touch patterns.

Data format:

Both datasets are provided as a single .mat file. Each .mat file contains a 5400x2 cell array.

• Column 1: time-series data for each touch event (i.e., drawing of a character). Each time series is represented as a 100x4 cell array. This represents the 100 temporal samples, each containing different information described below.
• Column 2: string label indicating the character (A,B,C, etc.). 

The time series data has been randomized for each dataset. Each time series represents approximately 3 seconds of data and is composed of 100 samples containing the following 4 cells:

• (1x7 cell) Robot joint torques (Nm).
• (1x7 cell) Robot joint positions (rad).
• (1x3 cell) Cartesian position of the end-effector (mm).
• (1x6 cell) Forces and moments the center of the touchpad  (N for forces, Nm for moments). 

Hardware:

• Collaborative robot: KUKA LBR iiwa 14 R820.
• Touchpad: plexiglass, uninstrumented.