pHRI-DIGI-TACT: Digits Dataset from Intrinsic Robot Tactile Sensing

The pHRI-DIGI-TACT dataset provides time-series data captured from an uninstrumented, 3D-printed touchpad interface mounted on the end-effector of a collaborative robot. Users can draw digits (0-9) on the touchpad by sliding their finger, and the robot's joint torques are recorded. This dataset facilitates research in intuitive robot control, physical human-robot collaboration, tactile sensing, machine learning for gesture recognition, and digit recognition. It leverages the intrinsic tactile sensing capabilities of a KUKA LBR iiwa 14 R820 robot, interpreting touch events on the touchpad using its joint torque sensors. The dataset is presented in four versions:

• pHRI-DIGI-TACT_SingleUser: this dataset includes 1500 time series, with 150 samples corresponding to each of the ten digits (0-9) drawn on the touchpad. All data was recorded from a single user interacting with the robot.
• pHRI-DIGI-TACT_MultipleUsers: this dataset also contains 1500 time series (150 per digit), but the data was collected from three different users (1 female, 2 male; all right-handed). This version allows for the analysis of inter-user variability in touch patterns.
• pHRI-DIGI-TACT_MultipleUsers_Reversed: this dataset contains 3000 time series, comprising the original 1500 from pHRI-DIGI-TACT_MultipleUsers and an additional 1500 generated through data augmentation to represent digits drawn in reverse.
• pHRI-DIGI-TACT_MultipleUsers_Rotated: this dataset contains 4500 time series. It includes the original 1500 from pHRI-DIGI-TACT_MultipleUsers, plus 1500 generated to represent digits rotated by +90 degrees, and another 1500 for digits rotated by -90 degrees (again, using data augmentation).    

Data format:

All four datasets are provided as separate .mat files. The sizes of the cell arrays within these files are as follows:

• pHRI-DIGI-TACT_SingleUser.mat: 1500x2 cell array
• pHRI-DIGI-TACT_MultipleUsers.mat: 1500x2 cell array
• pHRI-DIGI-TACT_MultipleUsers_Reversed.mat: 3000x2 cell array
• pHRI-DIGI-TACT_MultipleUsers_Rotated.mat: 4500x2 cell array       

In all cases, the structure of the cell array is consistent:

• Column 1: time-series data for each touch event. Each time series is represented as a 100x5 cell array. This represents the 100 temporal samples, each containing different information described below.
• Column 2: string label indicating the digit drawn (N0, N1, N2, N3, N4, N5, N6, N7, N8, N9). 

The time-series data is not ordered by digit label and has been randomized within each dataset. Each time series represents approximately 2 seconds of data and is composed of 100 samples containing the following 5 cells:

• (1x7 cell) Robot joint torques (Nm).
• (1x7 cell) Robot joint positions (rad).
• (1x6 cell) End-effector pose, described by the Cartesian position (mm) and Euler angles (rad).
• (1x3 cell) Forces at the end-effector (N).
• (1x3 cell) Moments at the end-effector (Nm).

Hardware:

• Collaborative robot: KUKA LBR iiwa 14 R820.
• Touchpad: uninstrumented touchpad consisting of a 3D-printed frame holding a smooth plexiglass surface.