Fine Robotic Manipulation without Force/Torque Sensor

TL;DR

This paper introduces a neural network approach to estimate external forces on robots using only internal signals, enabling force sensing without additional hardware like force/torque sensors, suitable for precise tasks such as assembly.

Contribution

The paper presents a novel neural network method that accurately estimates external wrench solely from internal robot signals across diverse scenarios, eliminating the need for external force sensors.

Findings

Accurate external wrench estimation demonstrated in pin insertion with 100-micron clearance.

Successful hand-guiding experiment without external force sensors.

Potential to retrofit existing industrial robots with force sensing capabilities.

Abstract

Force Sensing and Force Control are essential to many industrial applications. Typically, a 6-axis Force/Torque (F/T) sensor is mounted between the robot's wrist and the end-effector in order to measure the forces and torques exerted by the environment onto the robot (the external wrench). Although a typical 6-axis F/T sensor can provide highly accurate measurements, it is expensive and vulnerable to drift and external impacts. Existing methods aiming at estimating the external wrench using only the robot's internal signals are limited in scope: for example, wrench estimation accuracy was mostly validated in free-space motions and simple contacts as opposed to tasks like assembly that require high-precision force control. Here we present a Neural Network based method and argue that by devoting particular attention to the training data structure, it is possible to accurately estimate the external wrench in a wide range of scenarios based solely on internal signals. As an illustration, we demonstrate a pin insertion experiment with 100-micron clearance and a hand-guiding experiment, both performed without external F/T sensors or joint torque sensors. Our result opens the possibility of equipping the existing 2.7 million industrial robots with Force Sensing and Force Control capabilities without any additional hardware.