A5003876727- Magnetic Bearings and Levitation Dynamics
- Spacecraft Dynamics and Control
- Space Satellite Systems and Control
- Inertial Sensor and Navigation
- Control and Dynamics of Mobile Robots
- Adaptive Control of Nonlinear Systems
- Tribology and Lubrication Engineering
- Advanced Control Systems Optimization
- Geophysics and Sensor Technology
- Robotic Path Planning Algorithms
- Astro and Planetary Science
- Vibration Control and Rheological Fluids
- Dynamics and Control of Mechanical Systems
- Risk and Safety Analysis
- Aerospace Engineering and Control Systems
- Geomagnetism and Paleomagnetism Studies
- Robotic Mechanisms and Dynamics
- Healthcare Technology and Patient Monitoring
- Stability and Control of Uncertain Systems
- Safety Systems Engineering in Autonomy
- Adversarial Robustness in Machine Learning
- Bladed Disk Vibration Dynamics
- Advanced Control Systems Design
- Electric and Hybrid Vehicle Technologies
- Modeling and Simulation Systems
United States Air Force Office of Scientific Research
2016-2022
University of Michigan
2019
Kirtland Air Force Base
2013-2016
United States Air Force Research Laboratory
2010-2016
University of Florida
2006-2010
The last five years marked a surge in interest for and use of smart robots, which operate dynamic unstructured environments might interact with humans. We posit that well-validated computer simulation can provide virtual proving ground many cases is instrumental understanding safely, faster, at lower costs, more thoroughly how the robots future should be designed controlled safe operation improved performance. Against this backdrop, we discuss help robotics, barriers currently prevent its...
The development of a hybrid steering logic that maintains attitude tracking precision while avoiding hyperbolic internal singularities or escaping elliptic inherent to single-gimbal control moment gyroscopes is discussed. enables null motion and limits torque error when approaching singularity, it adds an external singularity. hybrid-steering-logic algorithm accomplishes these tasks through the definitions novel singularity metrics transition continuously from local-gradient pseudoinverse...
Spacecraft relative motion planning is concerned with the design and execution of maneuvers to a nominal target. These types are frequently used in missions such as rendezvous docking, satellite inspection, formation flight, where exclusion zones representing spacecraft or other obstacles must be avoided. The presence these leads nonlinear nonconvex constraints that satisfied. In this paper, novel approach obstacle avoidance thrust developed. This based on graph search applied virtual net...
Analytic optimization methods typically used to derive optimal steering algorithms for single-gimbal control moment gyros do not consider the structure of Jacobian matrix mapping gimbal rates onto desired torque within their cost function. Many resulting from these systematically take first and second derivatives, forming Hessian matrices obtain a solution. However, optimality is usually local result cannot be mapped back its performance. It shown that majority are with respect one specific...
This paper presents an application of model predictive control to the attitude dynamics underactuated spacecraft with two reaction wheels and zero angular momentum. Such a system cannot be stabilized by any smooth or continuous time-invariant feedback law. However, has remarkable ability generate laws that are discontinuous in state and, as such, can applied this problem. The formulation is analyzed depth shown produce asymptotically stabilizing controller, which enforces constraints....
Modeling the interaction of a slowly rotating hollow conducting sphere in magnetic field provided an understanding dynamics orbiting space objects moving through Earth's field. This analysis, performed late 1950s and limited to uniform fields, was innovative acknowledged pioneers who first observed rotary magnetism, particular, seminal work Hertz 1880. Now, there is interest using produced by one object stop spin second so that docking can occur. In this paper, we consider, yet again, We...
This paper presents a constrained attitude control approach for performing spacecraft reorientation maneuvers that maintain specified body vectors within inclusion zones and out of exclusion zones, while respecting authority limits. The controller uses supervisory switching strategy with an inner-loop Lyapunov SO(3)-based outer-loop set-point guidance. A virtual net orientation equilibria covering SO(3) is introduced, positively invariant constraint admissible sets on × ℝ <sup...
This paper presents an analytic dynamic model and a geometric numerical integrator for spacecraft with reaction wheel assemblies. According to Lagrangian mechanics on abstract Lie group, Euler-Lagrange equations are derived without any restrictive assumptions the configuration of wheels. yields most generalized model, that can possibly include effects arbitrary mass distribution about their spin axes, such as imbalance. The second part is focused constructing integrator, referred group...
This paper describes a method for recovering linear controllability the attitude of an underactuated spacecraft by accounting effects solar radiation pressure in model. The developments are based on model that has at least two functional reaction wheels. A torque is function incorporated and, under suitable assumptions, can be simplified with body symmetry. Conditions given which symmetric-body will experience zero torque. stability discussed, and necessary sufficient conditions to regained...
This brief presents a convex-optimization-based real-time control allocation algorithm to optimally utilize multiple actuators on momentum system while explicitly considering actuator constraints. The primary objective of the is minimize torque error and improve performance when saturates or becomes singular. As secondary objective, internal bearing gear friction are exploited reduce power usage without need for accurate models. exploits fact that redundant moment gyroscopes (CMGs) rotors...
This paper develops a switching feedback controller for the attitude of an underactuated spacecraft that exploits two internal control torques provided by reaction wheels. The problem is challenging; example, even in zero total angular momentum case, no smooth or continuous time-invariant law stabilizing desired orientation exists. method introduced here separation system states into inner-loop base variables and outer-loop fiber variables. track periodic reference trajectories, amplitude...
Modeling the interaction between a moving conductor and static magnetic field is critical to understanding operation of induction motors, eddy current braking, dynamics satellites through Earth's field. Here, we develop case thick-walled sphere rotating in uniform field, which simplest, non-trivial, magneto-statics problem that leads complete closed-form expressions for resulting potentials, fields, currents. This solution requires knowledge all Maxwell's time independent equations, scalar...
The attitude dynamics model for a spacecraft with variable speed control moment gyroscope (VSCMG) is derived using the principles of variational mechanics. resulting obtained in framework geometric mechanics, relaxing some assumptions made prior literature on gyroscopes (CMGs). These include symmetry rotor and gimbal structure, no offset between centers mass rotor. equations show complex nonlinear coupling internal degrees-of-freedom associated VSCMG base body's rotational...
Current methods of system identification inject random or sinusoidal signals into the and obtain feedback to learn infer parameters. In general, these do not consider learning convergence property signal its effects upon overall system. addition, richness a is reduced when passed through actuator that acts as low-pass filter. Furthermore, choice both typically effect motion on controlling body (e.g., movement tool point for robot manipulator with respect joint motion, entire satellite...
Spacecraft relative motion planning is concerned with the design and execution of maneuvers to a nominal target. These must account for spacecraft dynamics, possibly constrained thrust capabilities inclusion exclusion zone constraints, where latter can be non-linear non-convex. In this paper, scheme generating feasible trajectory based on graph search applied set (virtual net) closed (periodic) natural trajectories (NMTs) extended incorporate open (non-periodic) NMTs. This extension...
The paper discusses properties of closed-loop discrete-time systems operating under minimum-time Model Predictive Control (MPC)-based feedback laws. Minimum-time MPC is increasing interest in view applications such as attitude waypoint tracking by agile satellites, rapid spacecraft docking, and helicopter ship landing. It shown the that non-uniqueness optimal control sequence can result a loss Lyapunov stability, which be recovered through selection using lexicographic optimization. A...
A parameter governor-based controller is applied to control a pair of satellites an unforced periodic relative orbit in Hill's frame with the desired phasing thereby achieving and maintaining two satellite formation while satisfying imposed constraints. To accomplish this, adjusts commanded time shifts each along target trajectory. We refer such governor as shift governor. Theoretical guarantees are presented for convergence configuration case when set possible finite. Simulation results...
Control momentum gyros (CMGs) are often chosen for satellites where high attitude precision and torque needed while using minimal input power. of these types systems is complicated directly dependent on the number actuators their gimbal axis orientations with respect to satellite body frame. This paper discusses potential benets optimizing congurations
The attitude dynamics of a spacecraft with variable speed control moment gyroscope (VSCMG), in the presence conservative external inputs, are derived framework geometric mechanics. A complete model, that relaxes some assumptions made prior literature on gyroscopes, is obtained. These equations show complex nonlinear coupling between internal degrees freedom associated CMG and base body's freedom. General ideas how this can be used to angular momentum body using changes variables finite...
gyroscopes is developed. The method provides closed-loop internal momentum tracking control to enable the flywheels start from rest and reach desired wheel speeds. proposed controller functioning as a variable-speed moment gyroscope steering law developed in terms of gimbal rates flywheel accelerations, which are weighted by singularity measure. Specifically, using null motion, strategy simultaneously perform reconfiguration for avoidance andinternal management startup. A Lyapunov-based...