Inna Sharf

• McGill University

In this paper, we present a comprehensive shared autonomy framework for human-in-the-loop policy fine-tuning and alignment. Our framework integrates policy adapting algorithms on a multi-agent system foundation tailored for human-robot interaction and decision-making arbitration. This strategy is intended for complex, task-oriented robotic tasks th...

In this paper, we carry out a detailed stability and phase space analysis of the nonlinear dynamics of a plate-like spacecraft in low Earth orbit. The craft is undergoing a constant-rate rotational motion about the normal of the ecliptic plane. As per our previous work, the coupling between this rotational motion, solar radiation pressure and the s...

Designing robotic arms for On-Orbit Servicing (OOS) missions is a non-trivial task which must consider many factors related to the intended use of the servicer spacecraft. The design problem is further complicated when considering the use of robotic arms mounted to CubeSat-class spacecraft for OOS missions. Additional constraints relating to the st...

The control of quadrotor vehicles under state and parameter uncertainty is a well studied problem that is vitally important to the deployment of these systems under real world conditions. In this article, we propose a linearization‐based extension to nonlinear systems of the existing scenario model predictive control (MPC) framework, which quantifi...

The timber-harvesting industry is lagging its peer industries, such as mining and agriculture, with respect to deployment of robotic, AI and autonomous technologies. In this paper, we tackle automation of a critical task that arises in transporting logs from the forest to the sawmill: the log loading operation. This work is motivated by the acute s...

We propose two novel motion planners for a robotic manipulator with a passive end-effector that is free to sway during and after the robot’s motion. The planners utilize Dynamic Programming to generate trajectories that damp the end-effector’s residual sway while ensuring that the boom tip—the point to which the end-effector is attached—follows a c...

div> Abstract: We propose two novel motion planners for a robotic manipulator with a passive end-effector that is free to sway during and after the robot's motion. The planners utilize Dynamic Programming to generate trajectories that damp the end-effector's residual sway while ensuring that the boom tip---the point to which the end-effector is att...

p>This paper presents a chance-constrained rollover-free manipulation planning method for robotic arms under payload mass uncertainty. The corresponding motion planning problem is stated as a chance-constrained nonlinear optimal control problem (NOCP) subject to kinematics and rollover stability constraints. The latter takes the form of a chance co...

On-Orbit Servicing (OOS) is a field of orbital operations concerned with the maintenance, repair, and refuelling of space assets. It is one of many proposed solutions to aid with the mitigation of the growing space debris population. In this work, we propose the use of a CubeSat servicer equipped with a 1 Degree of Freedom (DoF) robotic arm for per...

In this work, we propose a novel shared autonomy framework to operate articulated robots. We provide strategies to design both the task-oriented hierarchical planning and policy shaping algorithms for efficient human-robot interactions in context-aware operation of articulated robots. Our framework for interplay between the human and the autonomy,...

In this paper, a computationally efficient chance-constrained rollover-free motion planning method is presented. Specifically, the method is developed to plan motions for reconfigurable vehicles with the knowledge of a 3-D terrain model that has limited accuracy. The overall motion planning problem is formulated as a nonlinear optimal control probl...

This article presents a chance-constrained rollover-free manipulation planning method for robotic arms under payload mass uncertainty. The corresponding motion planning problem is stated as a chance-constrained nonlinear optimal control problem (NOCP) subject to kinematics and rollover stability constraints. The latter takes the form of a chance co...

p>This paper presents a chance-constrained rollover-free manipulation planning method for robotic arms under payload mass uncertainty. The corresponding motion planning problem is stated as a chance-constrained nonlinear optimal control problem (NOCP) subject to kinematics and rollover stability constraints. The latter takes the form of a chance co...

p>In this paper, a computationally efficient chance-constrained rollover-free motion planning method is presented. Specifically, the method is developed to plan motions for reconfigurable vehicles with the knowledge of a 3-D terrain model that has limited accuracy. The overall motion planning problem is formulated as a nonlinear optimal control pro...

p>This paper presents a chance-constrained rollover-free manipulation planning method for robotic arms under payload mass uncertainty. The corresponding motion planning problem is stated as a chance-constrained nonlinear optimal control problem (NOCP) subject to kinematics and rollover stability constraints. The latter takes the form of a chance co...

p>In this paper, a computationally efficient chance-constrained rollover-free motion planning method is presented. Specifically, the method is developed to plan motions for reconfigurable vehicles with the knowledge of a 3-D terrain model that has limited accuracy. The overall motion planning problem is formulated as a nonlinear optimal control pro...

In this work, we propose a solution to deorbit a plate-like spacecraft by exploiting a Solar and Thermal Radiation Pressure (STRP) resonance, more specifically the STRP-J2-φ resonance in semi-major axis, by using attitude control to enforce the resonance at all time. The feasibility of the strategy is verified in a realistic environment modelled by...

On-Orbit Servicing (OOS) is a mature field with decades of research into spacecraft design, control, and operation. In this work, we propose a novel approach to OOS system configuration through the use of a CubeSat form factor servicer equipped with a single Degree of Freedom (DoF) robotic arm actuated by a prismatic joint. Control of the base spac...

In this work, we build on our prior investigation of resonance for plate-like space objects, which was restricted to the SRP and J2 perturbations, and extend the methodology to TRP-J2-φ-resonances in the semi-major axis. The feasibility of the deorbitation strategy based on this resonance is verified in a realistic environment, modelled by the stat...

In this paper, we explore the resonance behavior exhibited by the historical NASA's Echo I satellite. It is well known that the coupling between the SRP and the geopotential (second zonal harmonic (J2)) perturbations leads to a resonance effect in eccentricity under certain conditions. Here, we revisit the orbital motion of Echo I in light of the r...

This paper presents a hierarchical framework that allows online point-to-point dynamic-stability-constrained optimal trajectory planning of a mobile manipulator robot working on rough terrain. First, the kinematics model of a mobile manipulator robot and the zero moment point stability measure are presented as theoretical background. Then, a sampli...

We examine the problem of agile trajectory tracking for a quadrotor vehicle with bidirectional thrust capabilities. A time-dependent linearization of the dynamics is presented based on the Lie algebra of $SO(3)$ . The obtained linear dynamics are used as the basis for a nonlinear model predictive control algorithm that does not require operating...

Unmanned Aerial Gliders form a subclass of fixed-wing Unmanned Aerial Vehicles which promise to offer sustained flight for a wide range of applications. Autonomous soaring allows these aircraft to detect and exploit rising air masses (thermals) without user input, which greatly simplifies their operation. While previous research has focused on the...

In this work, we propose a solution to completely deorbit a plate-like spacecraft by exploiting the SRP-J 2-φ resonance and using attitude control to enforce the resonance at all time. The feasibility of the strategy is verified in a realistic environment modelled by the coupled orbit-attitude propagator D-SPOSE where the full dynamics is propagate...

Autonomous absolute orbit determination (OD) for a satellite constellation using only inter-spacecraft measurements has considerable value in space systems engineering. This paper proposes a novel solution for cooperative autonomous OD for a system comprised of an arbitrary number of spacecraft, with inertial angles-only measurements. We establish...

This paper presents a framework that allows online dynamic-stability-constrained optimal trajectory planning of a mobile manipulator robot working on rough terrain. First, the kinematics model of a mobile manipulator robot, and the Zero Moment Point (ZMP) stability measure are presented as theoretical background. Then, a sampling-based quasi-static...

In this research, two existing re-entry models, the Debris Risk Assessment and Mitigation Analysis (DRAMA) model and the Debris Assessment Software (DAS) are used to study the influences of varying the parameters of the debris disposal orbit and its release conditions on the resultant casualty risk factor. With this perspective, the de-orbiting sta...

In this work, we study the effect of the rotational motion on the SRP-J2 resonance phenomenon and we suggest that a resonance effect of considerable strength could be achieved for non-spherical spacecraft in any orbit, by adopting an appropriate rotational motion scenario. In this way, it would be possible for a spacecraft to exploit the resonance...

Utilization of latent space to capture a lower-dimensional representation of a complex dynamics model is explored in this work. The targeted application is of a robotic manipulator executing a complex environment interaction task, in particular, cutting a wooden object. We train two flavours of Variational Autoencoders---standard and Vector-Quantis...

Autonomous orbit determination (OD) for a group of spacecraft using only inter-spacecraft measurements has considerable value in space systems engineering. This paper proposes a novel solution for cooperative autonomous OD for a system comprised of three spacecraft, by employing inertial angles-only measurements. Based on the two-body dynamics of e...

The growth of space debris in Earth's orbit is recognized as a serious threat to future space missions. To contain the growth of space debris in the long term, active removal of large defunct spacecraft is needed. A promising solution to this problem is the use of tether-nets. In the envisaged mission, a net is released from a chaser spacecraft tow...

In this paper, we solve the problem of minimizing the fuel and time cost of accurate rendezvous and de-orbiting of multiple pieces of space debris in a single mission. Continuous low thrust maneuvers are used to achieve each orbital transfer. The mission scenario considered requires the chaser to capture and de-orbit the debris into a disposal orbi...

This paper proposes a linear constrained model predictive control (MPC) to solve the path following problem for quadrotor unmanned aerial vehicles. In the controller, an augmented model is employed to completely eliminate the tracking error due to external disturbances imposed on the quadrotor. The proposed controller is capable of improving the tr...

Accurate knowledge of the rotational dynamics of a large space debris is crucial for space situational awareness (SSA), whether it be for accurate orbital predictions needed for satellite conjunction analyses or for the success of an eventual active debris removal mission charged with stabilization, capture and removal of debris from orbit. In this...

Motivated by the recursive Newton-Euler formulation, we propose a novel cascaded Gaussian process learning framework for the inverse dynamics of robot manipulators. This approach leads to a significant dimensionality reduction which in turn results in better learning and data efficiency. We explore two formulations for the cascading: the inward and...

An extensive evaluation of attitude estimation algorithms in simulation and experiments is performed to determine their suitability for a collision recovery pipeline of a quadcopter unmanned aerial vehicle. A multiplicative extended Kalman filter (MEKF), unscented Kalman filter (UKF), complementary filter, [Formula: see text] filter, and novel adap...

One of the most promising techniques to capture large debris on orbit consists in the use of tether-nets. With this concept currently at a medium technological readiness level only, numerical studies on tether-net removal missions are still needed. This paper presents a versatile simulator developed with the aim of gaining insight into the dynamics...

A new model for the analysis and prediction of the rotational motion of large space debris over a long term is outlined. A formulation for a high-order gravity-gradient torque is derived as well as the aerodynamic torque for a spinning spacecraft defined by a general surface geometry model. The comprehensive model is exercised for a coupled orbit-a...

In this paper, the sling load dynamics of an aerial vehicle carrying a payload are investigated by employing three formulations of the governing equations. They are the hybrid formulation where the system exists in either a taut cable or slack cable configuration, with appropriate treatment of the transition between the two; the linear complementar...

Current efforts in active debris removal strategies and mission planning focus on removing the largest, most massive debris. It can be argued, however, that small untrackable debris, specifically those smaller than 5 cm in size, also pose a serious threat. In this work, we propose and analyze a mission to sweep the most crowded Low Earth Orbit with...

In this paper, the deployment dynamics of nets in space is investigated through a combination of analysis and numerical simulations. The considered net is deployed by ejecting several corner masses and thanks to momentum and energy transfer from those to the innermost threads of the net. In this study, the net is modeled with a lumped-parameter app...

This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target, an...

A promising method to mitigate the space debris problem is to actively capture and remove debris by means of tether-nets. The chaser-tether-net-debris system is modeled with rigid bodies connected by constraints; the tether can be spooled in and out by controlling a winch on the chaser. Through dynamics simulation, this paper analyzes the effect of...

This paper focuses on the development of guidance, navigation and control for the docking of two cubic blimps, named Tryphons. The chaser and target Tryphons are assumed to be brought sufficiently close together through a rendezvous stage, where the docking stage then begins and the target is kept stationary. An ARtag fiducial marker system is used...

Bombardment of orbital debris and micrometeoroids on active and inoperative satellites is becoming an increasing threat to space operations and has significant consequences on space missions. Concerns with orbital debris have led agencies to start developing debris removal missions and knowing a target’s rotational parameters ahead of time is cruci...

A proposed method for containing the growth of space debris, which jeopardizes operation of spacecraft, is the active debris removal of massive derelict spacecraft and launcher upper stages by means of tether nets. The behavior of nets in space is not well known; therefore, numerical simulation is needed to gain understanding of deployment and capt...

Due to the recent technological progress, Human-Robot Interaction (HRI) has become a major field of research in both engineering and artistic realms, particularly so in the last decade. The mainstream interests are, however, extremely diverse: challenges are continuously shifting, the evolution of robot’ skills, as well as the advances in methods f...

This research addresses the design and testing of a debris capture system for use in a tether-net approach to space debris removal. The tether-net debris removal concept involves the ejection of a net from a spacecraft by applying accelerations to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target,...

In this paper, we present a leader-follower controller for the Micro-Hydraulic Toolkit (MHT), a skid-steering wheel-legged robot designed by Defence Research and Development Canada - Suffield Research Centre. The objective of the controller is to maneuver the MHT towards a desired position with respect to a designated leader. Using the range and be...

Tether-nets are one of the more promising methods for the active removal of space debris. The aim of this paper is to study the dynamics of this type of systems in space, which is still not well-known and the simulation of which has multiple outstanding issues. In particular, the focus is on the deployment and capture phases of a net-based active d...

The energy consumption of worm robots is composed of three parts: heat losses in the motors, internal friction losses of the worm device and mechanical energy locomotion requirements which we refer to as the cost of transport (COT). The COT, which is the main focus of this paper, is composed of work against two types of external factors: (i) the re...

One proposed method to mitigate the space debris problem is to actively capture and remove debris by means of tether-nets. In this paper, the effectiveness of the capture maneuver in multiple net deployment and debris tumbling conditions is evaluated. The sensitivity study is performed by means of simulations based on a lumped-parameter modeling ap...

A novel real-time pose estimation system is presented for solving the visual simultaneous localization and mapping problem using a rigid set of central cameras arranged such that there is no overlap in their fields-of-view. A new parameterization for point feature position using a spherical coordinate update is formulated which isolates system para...

Initiated as a research-creation project by professor and artist Nicolas Reeves, the Aerostabile project quickly expanded to include researchers and artists from a wide range of disciplines. Its current phase brings together four robotic and research-creation labs with various expertises in unstable and dynamic environments. The first group, under...

This paper presents a new methodology for on-line inertia parameters estimation for a rigid space debris captured by a tethered system, based on a new dynamics model of the system where the base satellite (chaser) and the space debris (target) are modeled as rigid bodies and the attachment points of the tether are offset from the centers of mass of...

A proposed method for containing the growth of space debris, which jeopardizes operation of spacecraft, is the active debris removal of massive derelict spacecraft and launcher upper stages by means of tether-nets. The behavior of such systems in space is not well-known; therefore, numerical simulation is needed to gain understanding of deployment...

Wheel-legged hybrid robots are known to be extremely capable in negotiating different types of terrain as they combine the efficiency of conventional wheeled platforms and the rough terrain capabilities of legged platforms. The Micro-Hydraulic Toolkit (MHT), developed by Defense Research and Development Canada at the Suffield Research Centre, is on...

This paper presents a generalization of the classic A* algorithm to the domain of sampling-based motion planning. The root assumptions of the A* algorithm are examined and reformulated in a manner that enables a direct use of the search strategy as the driving force behind the generation of new samples in a motion graph. Formal analysis is presente...

Ground effect on rotary aircraft has been studied for many decades. Although a large body of research results is now available for conventional helicopters, this topic is just beginning to receive attention in the unmanned aerial vehicles community, particularly for small size UAVs. The objective of this paper is to assess the applicability of a wi...

Collision avoidance for small unmanned aerial vehicles operating in a variety of environments is limited by the types of available depth sensors. Currently, there are no sensors that are lightweight, function outdoors in sunlight, and cover enough of a field of view to be useful in complex environments, although many sensors excel in one or two of...

Pose estimation for small unmanned aerial vehicles has made large improvements in recent years, leading to vehicles that use a suite of sensors to navigate and explore various environments. In particular, cameras have become popular due to their low weight and power consumption, as well as the large amount of data they capture. However, processing...

This paper presents a new methodology for on-line mass estimation for massive space debris captured by a tethered system. Mass estimation of unknown debris is critical for subsequent tasks in the space debris remediation mission, in particular, for debris retrieval and deorbiting. In the proposed algorithm, the base satellite (chaser) and space deb...

In this paper, we describe a new jumping behaviour developed for the quadruped robot, PAW (Platform for Ambulating Wheels). The robot has very few degrees of freedom and no knee joints. It employs springy legs and wheels at the distal ends of the legs to achieve various modes of legged, wheeled, and hybrid locomotion, such as high-speed breaking, b...

We present an optimal kinodynamic rapidly exploring random tree, a single query in- cremental sampling based optimal motion planner for robots with non-linear dynamics, differential constraints and actuation limitations. Our work extends the algorithms presented previously by formulating a fixed-final-state-free-final-time open loop configuration s...

This paper presents the development of an algorithm to estimate the state of a neutrally- buoyant airship as well as its deviation from a perfect mass-balance. That is to say, the eccentricity of the center of mass with respect to the center of buoyancy and the difference between the mass of the system and that of the displaced fluid are estimated....