Publications

Stable Adaptive Extended Kalman Filter for Estimating Robot Link Velocity and Acceleration

Published in IEEE IROS, 2023

Robot manipulators link velocity and acceleration can be estimated using nonlinear observers. This is done by model-based fusion of inertial measurement units (IMUs) with the robot motor encoders. This method has been proven to be light, generally applicable (broad bandwidth) and easily implementable. In order to further improve the estimation accuracy while running the system, we propose to adapt the noise information in this paper. This would automatically reduce the system vulnerability to imperfect modelings and sensor changes. Moreover, viable strategies to maintain the system stability are introduced. Finally we fully evaluate the overall framework with a seven DoF robot manipulator, whose links are equipped with IMUs.

Motion Planning and Inertia Based Control for Impact Aware Manipulation

Published in IEEE Transactions on Robotics - Under review, 2022

In this paper, we propose a method for motion generation and controls for a robot manipulator to interact with the environment through a striking or hitting motion. Given the task of placing a known object outside of the workspace of the robot, the robot needs to come in contact with it at a non zero relative speed. The configuration of the robot and the speed at contact matter because they affect the motion of the object. The physical quantity that depends on the configuration, the robot speed and the properties of the environment is formulated and referred to here as pre-impact flux. An approach to achieve the desired directional pre-impact flux for the robot is presented. This is achieved through a combination of a dynamical system (DS) for motion generation and a control system that regulates the directional inertia of the robot. Furthermore, a Quadratic Program (QP) formulation for achieving a desired inertia matrix at a desired position while following a motion plan constrained to the robot limits is presented. The system is tested for different scenarios in simulation showing the repeatability of the procedure and in real scenarios with KUKA LBR iiwa 7 robot.

Learning to Hit: A statistical Dynamical System based approach

Published in IROS, 2021

This paper proposes a manipulation scheme based on learning the motion of objects after being hit by a robotic end-effector. This allows for the object to be positioned at a desired location outside the physical workspace of the robot. An estimate of the object dynamics under friction and collisions is learnt and used to predict the desired hitting parameters (speed and direction), given the initial and desired location of the object. Based on the obtained hitting parameters, the desired pre-impact velocity of the end-effector is generated using a stable dynamical system. The performance of the proposed DS is validated in simulation and and is used to learn a model for hitting using real robot. The approach is tested on real robot with a KUKA LBR IIWA robot.

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A Virtual Reality Interface for an Autonomous Spray Painting UAV

Published in IEEE-RAL (Robotics and Automation Letters), 2019

PaintCopter is an autonomous UAV capable of spray painting on complex 3D surfaces. This work aims to make PaintCopter more user-friendly and to enable more intuitive human-robot interaction. We propose a virtual reality interface that allows the user to immerse in a virtual environment, navigate around the target surface and paint at desired locations using a virtual spray-gun. A realistic paint simulator provides a real-time pre-visualization of the painting activity that can either be processed right away or stored to disk for later execution. An efficient optimization based planner uses this information to plan the painting task and execute it. The proposed planner maximizes the paint quality while respecting the spray nozzle constraints and platform dynamics. Our experiments show that the interface allows the user to make precise modifications to the target surface. Finally, we demonstrate the use of virtual reality interface to define a painting mission, and then the PaintCopter carrying out the mission to paint a desired multi-colored pattern on a 3D surface