Plug, Play, and Comply: A Modular Framework for Online Variable Impedance with Arbitrarily Oriented Compliance Axes
2026-07-24 • Robotics
Robotics
AI summaryⓘ
The authors present a control system for robots that works with different types of robot arms without needing major changes. Their system uses plugins to separate the control method from the robot hardware, allowing easy reuse across various robots. It supports flexible control commands that can adjust stiffness and movement in both joint and space coordinates, helpful for tasks where the robot interacts with objects gently. They also made it open-source and demonstrated it working on real robots and simulations, showing it can adapt compliance directions based on the task needs. This approach helps in complex tasks where the robot must carefully manage how it moves and applies force.
compliant controlROS controlCartesian impedance controlvariable impedanceplugin-based architectureURDF modelsrobot kinematicsrobot dynamicsPinocchio librarycontact-rich manipulation
Authors
Mihael Simonič, Xiaocong Li
Abstract
The paper proposes a robot-agnostic compliant-control framework that extends the ROS control ecosystem with standardized joint and Cartesian command interfaces. It addresses a key limitation of existing control software: no reusable infrastructure for implementing compliant-control algorithms across different manipulators while preserving a common interface to higher-level applications. A plugin-based architecture separates controller infrastructure from control-law implementation. Generic wrappers use existing hardware abstractions to interface with different manipulators, while runtime-loaded plugins implement only the control law. Command interfaces support joint- and Cartesian-space references, stiffness and damping gains, nullspace targets, and feedforward terms, enabling variable impedance and diverse compliant-control formulations. Robot kinematics and dynamics are computed from URDF models using Pinocchio. The architecture facilitates the development of compliant-control strategies and enables the same implementation to be deployed across platforms unchanged. The complete framework, including reference controllers, high-level task interfaces, and example configurations for various manipulators, is open-sourced. The reference Cartesian impedance controller supports task-dependent compliance by rotating translational and rotational stiffness and damping, allowing the principal compliance directions to be updated online according to local task geometry rather than remaining fixed in the robot base or TCP frame. This is particularly important in contact-rich manipulation, where the desired directions of motion, constraints, and compliance directions may vary throughout task execution. Real-robot experiments demonstrate task-dependent compliance in contact-rich manipulation, while simulations show portability across manipulators with distinct kinematic and dynamic characteristics.