Nonparametric Inverse Dynamic Models for Multimodal Interactive Robots

TL;DR

This paper introduces a nonparametric, multimodal Gaussian process regression method for modeling inverse dynamics in interactive robots, effectively handling complex, uncertain interactions and external disturbances.

Contribution

It proposes a novel clustering-based Gaussian process approach for multimodal inverse dynamic modeling, enabling better handling of unmeasured interactions and external inputs in robotic systems.

Findings

The method accurately models complex dynamic modes.

It effectively separates perturbed data with external inputs.

Experiments demonstrate improved safety and performance.

Abstract

Direct design of a robot's rendered dynamics, such as in impedance control, is now a well-established control mode in uncertain environments. When the physical interaction port variables are not measured directly, dynamic and kinematic models are required to relate the measured variables to the interaction port variables. A typical example is serial manipulators with joint torque sensors, where the interaction occurs at the end-effector. As interactive robots perform increasingly complex tasks, they will be intermittently coupled with additional dynamic elements such as tools, grippers, or workpieces, some of which should be compensated and brought to the robot side of the interaction port, making the inverse dynamics multimodal. Furthermore, there may also be unavoidable and unmeasured external input when the desired system cannot be totally isolated. Towards semi-autonomous robots, capable of handling such applications, a multimodal Gaussian process regression approach to manipulator dynamic modelling is developed. A sampling-based approach clusters different dynamic modes from unlabelled data, also allowing the seperation of perturbed data with significant, irregular external input. The passivity of the overall approach is shown analytically, and experiments examine the performance and safety of this approach on a test actuator.