Kinematics & Dynamics Library for Baxter Arm

TL;DR

This work addresses unreliable native IK support for Baxter by delivering a Python-based Kinematics & Dynamics library that provides forward and inverse pose kinematics for a 7-DOF arm, along with velocity mapping via the Jacobian and redundancy resolution. It combines a DH-based closed-form forward model, a 6-DOF analytical IK, and three iterative IK solvers (Jacobian pseudoinverse, random restart, and CCD) to handle redundancy, complemented by a dynamics module using Euler–Lagrange to compute $M(q)$, $C(q,\dot{q})$, and $G(q)$ for model-based control. The library also includes a skeletal visualization and workspace analysis, plus trajectory-following validation against Baxter’s Gazebo interface, demonstrating comparable real-time performance to existing tools like PyKDL. Overall, the toolkit enhances Baxter research capabilities by delivering robust kinematics, dynamics, redundancy handling, and practical trajectory execution, facilitating safer and more flexible experimentation in robotics research.

Abstract

The Baxter robot is a standard research platform used widely in research tasks, supported with an SDK provided by the developers, Rethink Robotics. Despite the ubiquitous use of the robot, the official software support is sub-standard. Especially, the native IK service has a low success rate and is often inconsistent. This unreliable behavior makes Baxter difficult to use for experiments and the research community is in need of a more reliable software support to control the robot. We present our work towards creating a Python based software library supporting the kinematics and dynamics of the Baxter robot. Our toolbox contains implementation of pose and velocity kinematics with support for Jacobian operations for redundancy resolution. We present the implementation and performance of our library, along with a comparison with PyKDL. Keywords- Baxter Research Robot, Manipulator Kinematics, Iterative IK, Dynamical Model, Redundant Manipulator

Figures (8)

• Figure 1: Baxter's 7-DOF arm
• Figure 2: Link Diagram with coordinate frame assignment
• Figure 3: Baxter Arm represented by a skeleton model
• Figure 4: Workspace Diagram of Baxter Left Arm, colored based on Yoshikawa Manipulability Index (Red = Low, Yellow = Medium, Green = High)
• Figure 5: PseudoInverse-RR in action