Xiaolei Hou

Representation of vehicle dynamics in haptic teleoperation of aerial robots

This paper considers the question of providing effective feedback of vehicle dynamic forces to a pilot in haptic teleoperation of aerial robots. We claim that the usual state-of-the-art haptic interface, based on research motivated by robotic manipulator slaves and virtual haptic environments, does a poor job of reflecting dynamic forces of a mobile robotic vehicle to the user. This leads us to propose a novel force feedback user interface for mobile robotic vehicles with dynamics. An analysis of the closed-loop force-displacement transfer functions experienced by the master joystick for the classical and the new approach clearly indicate the advantages of the proposed formulation. Both the classical and the proposed approach have been implemented in the teleoperation of a quadrotor vehicle and we present quantitative and cognitive performance data from a user study that corroborates the expected performance advantages.

Dynamic kinesthetic boundary for haptic teleoperation of aerial robotic vehicles

This paper introduces a novel dynamic kinesthetic boundary to aid a pilot to navigate an aerial robotic vehicle through a cluttered environment. Classical haptic teleoperation interfaces for aerial vehicles utilize force feedback to provide the pilot with a haptic feel of the robots interaction with an environment. The proposed approach constructs a dynamic kinesthetic boundary on the master device that provides the pilot with hard boundaries in the haptic workspace to indicate approaching obstacles. An advantage of the proposed approach is that when the vehicle is flying free of obstacles, then the haptic feedback of the joystick can be used to provide a more natural feel of the vehicle dynamics. Furthermore, rather than a gradual onset of virtual potential forces that are felt in the classical approaches, a pilot encountering the dynamic kinesthetic boundary is immediately aware of the presence of the obstacle and can act accordingly. The approach is implemented on an admittance haptic joystick to ensure that the haptic boundaries are faithfully rendered. We prove that in the case of perfect velocity tracking, the proposed algorithm will ensure the vehicle never colliding with the environment. Experiments were conducted on a robotic platform and the results provide verification of the novel approach.

Dynamic Kinesthetic Boundary for Haptic Teleoperation of VTOL Aerial Robots in Complex Environments

This paper introduces a novel constraint in the master joystick workspace, termed the dynamic kinesthetic boundary, that aids a pilot to navigate an aerial robotic vehicle through a cluttered environment. The proposed approach exploits spatial cues by projecting the remote environment into a hard boundary in the master device workspace that provides a pilot with a natural representation of approaching obstacles. The approach is distinguished from classical force feedback approaches by allowing normal operation of the vehicle in free flight and only imposing constraints when approaching and interacting with the environment. A key advantage is that contact with the environment constraint is immediately perceptible to a pilot, allowing them to make suitable adjustments to their inputs. Modulation of the velocity reference for the slave robot ensures obstacle avoidance while allowing a vehicle to approach as close as desired to an object, albeit at a slow speed. A comprehensive user study was performed to systematically test the proposed algorithm and comparisons to two existing state-of-the-art approaches are provided to demonstrate the relative performance of the proposed approach.

Intercontinental haptic teleoperation of a flying vehicle: A step towards real-time applications

This paper describes the theory and practice for a stable haptic teleoperation of a flying vehicle. It extends passivity-based control framework for haptic teleoperation of aerial vehicles in the longest intercontinental setting that presents great challenges. The practicality of the control architecture has been shown in maneuvering and obstacle-avoidance tasks over the internet with the presence of significant time-varying delays and packet losses. Experimental results are presented for teleoperation of a slave quadrotor in Australia from a master station in the Netherlands. The results show that the remote operator is able to safely maneuver the flying vehicle through a structure using haptic feedback of the state of the slave and the perceived obstacles.

Comparative Study of Haptic Interfaces for Bilateral Teleoperation of VTOL Aerial Robots

Force feedback is a powerful sensory cue that can provide a user, remotely teleoperating a vertical takeoff and landing (VTOL) aerial robotic vehicle, with an enhanced perception of the robot motion and interaction with the local environment. The accepted framework for mobile vehicle teleoperation, inspired by decades of research into manipulator teleoperation, maps joystick displacements to vehicle velocity set points and reflects interactive forces from the vehicle to the human operator. This paper proposes a novel admittance configured haptic interface where the force input from the user is used as a velocity set point and the joystick position is servo-controlled to reflect the vehicle velocity. This paper provides a comparative study, both analytic and experimental, of the two interfaces to investigate the performance and perceptual differences in the context of teleoperation of a VTOL aerial robot.

An intuitive multimodal haptic interface for teleoperation of aerial robots

This paper presents a novel intuitive multi-modal force feedback interface for teleoperation of mobile robotic vehicles. Two different force feedback interfaces are considered: a force feedback joystick and a novel force feedback trackball. The joystick considered is based on the admittance user interface developed by the authors in earlier work and is configured to servo velocity of the vehicle. The force feedback trackball is configured to map vehicle velocity directly to trackball velocity, exploiting the effectively infinite workspace of the trackball to overcome the classical challenge of servo controlling a slave with infinite workspace using a master device with finite workspace. A key contribution of the paper is to provide a modeling framework, based on the bond graph formalism, that allows the energy consistent modeling of input from an admittance joystick as reference to an internal velocity regulation loop for the vehicle. Once this is implemented it is straightforward to interconnect multiple input devices, and in particular the trackball device, using standard interconnection rules in bond graphs. Experiments were performed, and the outcomes verify the feasibility and effectiveness of the proposed interface.