README.md

---
license: mit
language:
- en
tags:
- MechanismDesign
- LinkageMechanism
- SpatialLinkage
---
# Dataset Overview
This dataset is generated for the path synthesis of 1-DOF(degree-of-freedom) closed-loop spatial four-bar linkage mechanisms. Specifically, it contains **closed paths only** with their corresponding mechanisms. All mechanisms are actuated by revolute (R) joints, and include other various joints, including prismatic (P), cylindrical (C), universal (U), and spherical (S) joints. The dataset covers all possible 1-DOF(degree-of-freedom) closed-loop spatial four-bar mechanism topologies, resulting in a total of 26 distinct topologies.

(The database with both closed and open paths see https://huggingface.co/datasets/ComputerAidedDesignInnovation/Spatial_Four_Bar_Mechanism)

The corresponding paper is currently under review and will be linked here once published. The simulator of this database can be found in: https://github.com/Xueting-Deng/General-Spatial-Four-Bar-Mechanism-Simulator

# File Naming Convention
Each file has been thoroughly shuffled; the filenames follow the general format:

(normalization_state)\_(mec_topology)\_(mec/path/others)

where:

(normalized / non_normalized) indicates whether the data has undergone the normalization procedure;

(mec_topology) specifies the mechanism topology;

(mec / path / others) indicates whether the file stores mechanism parameters, coupler paths, or additional mechanism information.

# Normalization
Normalization is applied to both mechanisms and their corresponding paths through reconstruction (cubic B-spline interpolation), translation (by subtracting the mean coordinate), rotation (by aligning the trajectory with the principal axes obtained from principal component analysis), reflection (determined via independent component analysis), and scaling (by the total arc length). A detailed explanation of the normalization procedure can be found in the accompanying paper (https://asmedigitalcollection.asme.org/IDETC-CIE/proceedings-abstract/IDETC-CIE2024/88414/V007T07A005/1209040).

The files labeled (non_normalized) contain the raw data prior to normalization. Before normalization, the location and rotational axis of J0 are fixed as the origin and the global z-axis, respectively, and are therefore omitted to reduce storage requirements. However, after normalization, the position and rotational axis of J0 are no longer fixed. Consequently, the normalized joint location and rotational axis of J0 are stored separately in (jc0) and (ja0)

# Mechanism Topology Representation
The field (mec_topology) represents the joint-type sequence of the mechanism topology. For example, an RSCR mechanism denotes a closed-loop four-bar mechanism composed of Revolute–Spherical–Cylindrical–Revolute joints.

# Detailed Data Structure
Mechanisms are represented using six selected joints, where each mechanism is stored as a 6×3 matrix. For non-normalized mechanisms, the location and rotational axis of J0 are fixed as the origin and the global z-axis, respectively, and are therefore not recorded. For normalized mechanisms, this information is no longer fixed after normalization and is stored separately in the (jc0) and (ja0) files, each represented as a 1×3 vector. Detailed information regarding the six selected joints can be found in Appendix A of the accompanying paper (the link will be provided after publication).

Paths are represented using 3D Cartesian coordinates. Before normalization, each path contains 360 sampled points and is stored as a 360×3 matrix. After normalization and reconstruction, each path contains 100 sampled points and is stored as a 3×100 matrix.

For each topology, the dataset contains six associated files in total:

-non-normalized mechanisms,

-non-normalized paths,

-normalized mechanisms,

-normalized paths,

-normalized J0 joint locations (jc0)

-normalized J0 joint rotational axis (ja0)