Adaptive-Optimal Control of Spacecraft near Asteroids

Spacecraft dynamics and control in the vicinity of an asteroid is a challenging and exciting problem. Currently, trajectory tracking near asteroid requires extensive knowledge about the asteroid and constant human intervention to successfully plan and execute proximity operation. This work aims to reduce human dependency of these missions from a guidance and controls perspective. In this work, adaptive control and model predictive control are implemented to generating and tracking obstacle avoidance trajectories in asteroid’s vicinity. Specifically, direct adaptive control derived from simple adaptive control is designed with e modification to track user-generated trajectories in the presence of unknown system and sensor noise. This adaptive control methodology assumes no information on the system dynamics, and it is shown to track trajectories successfully in the vicinity of the asteroid. Then a nonlinear model predictive control methodology is implemented to generate obstacle avoidance trajectories with minimal system information namely mass and angular velocity of the asteroid. Ultimately, the adaptive control system is modified to include feed-forward control input from the nonlinear model predictive control. It is shown through simulations that the new control methodology names direct adaptive model predictive control (DAMPC), is able to generate sub-optimal trajectories. A comparative study is done with Asteroid Bennu, Kleopatra and Eros to show the benefits of DAMPC over adaptive control and MPC. A study on effect of noisy measurements and model is also conducted on adaptive control and direct adaptive model predictive control

Axial Compressor Design with Counter-Rotation and Variable RPM for Stall Mitigation

Compressor Stall, an aerodynamic instability due to abnormal air flow in the compressor resulting in loss of total pressure and compressor performance. One of the reasons of compressor stall is due to rise in static back pressure at compressor exit which may result from an imbalance of incidence angle at the rotor and stator and rotational speed. The paper presents the results of a new axial compressor design with counter rotation and variable RPM. Counter-Rotation is used to push compressor performance during stall by moving the operating point away from surge line with a higher pressure ratio rise. Initially an axial compressor is designed with counter-rotation at design point. The flow is modelled by means of Navier-Stokes computation using the upstream rotor conditions and exit static pressure condition with k-epsilon as the turbulence model. Compressor exit conditions are then changed to stall the compressor. After the compressor stalls the RPM of the counter-rotating stage is varied until the compressor recovers from the stall. This novel idea unlike the conventional stall control systems mitigates the stall without compromising compressor performance, in fact it helps to increase the performance and pressure ratio of the compressor with the means of counter-rotation and variable RPM

Computationally Efficient Data-Driven Discovery and Linear Representation of Nonlinear Systems For Control

This work focuses on developing a data-driven framework using Koopman operator theory for system identification and linearization of nonlinear systems for control. Our proposed method presents a deep learning framework with recursive learning. The resulting linear system is controlled using a linear quadratic control. An illustrative example using a pendulum system is presented with simulations on noisy data. We show that our proposed method is trained more efficiently and is more accurate than an autoencoder baseline

Adaptive Modified RISE-based Quadrotor Trajectory Tracking with Actuator Uncertainty Compensation

This paper presents an adaptive robust nonlinear control method, which achieves reliable trajectory tracking control for a quadrotor unmanned aerial vehicle in the presence of gyroscopic effects, rotor dynamics, and external disturbances. Through novel mathematical manipulation in the error system development, the quadrotor dynamics are expressed in a control-oriented form, which explicitly incorporates the uncertainty in the gyroscopic term and control actuation term. An adaptive robust nonlinear control law is then designed to stabilize both the position and attitude loops of the quadrotor system. A rigorous Lyapunov-based analysis is utilized to prove asymptotic trajectory tracking, where the region of convergence can be made arbitrarily large through judicious control gain selection. Moreover, the stability analysis formally addresses gyroscopic effects and actuator uncertainty. To illustrate the performance of the control law, comparative numerical simulation results are provided, which demonstrate the improved closed-loop performance achieved under varying levels of parametric uncertainty and disturbance magnitudes

Direct-Adaptive Nonlinear MPC for Spacecraft Near Asteroids

In this work, we propose a novel controller based on a simple adaptive controller methodology and model predictive control (MPC) to generate and track trajectories of a spacecraft in the vicinity of asteroids. The control formulation is based on using adaptive control as a feedback controller and MPC as a feed-forward controller. The spacecraft system model, asteroid shape and inertia are assumed to be unknown, with the exception of the estimated total mass and angular velocity of the asteroid. The MPC is used to generate feed-forward trajectories and control input using only the mass and angular velocity of the asteroid combined with obstacle avoidance constraints. However, since the control input from MPC is calculated using only an approximated model of the asteroid, it fails to control the spacecraft in the presence of disturbances due to the asteroid’s irregular gravitational field. Hence, we propose an adaptive controller in conjunction with MPC to handle unknown disturbances. The numerical results presented in this work show that the novel control system is able to handle unknown disturbances while generating and tracking sub-optimal trajectories better than adaptive control or MPC solely

Direct-Adaptive Nonlinear MPC for Spacecraft Near Asteroids

In this work, we propose a novel controller based on a simple adaptive controller methodology and model predictive control (MPC) to generate and track trajectories of a spacecraft in the vicinity of asteroids. The control formulation is based on using adaptive control as a feedback controller and MPC as a feed-forward controller. The spacecraft system model, asteroid shape and inertia are assumed to be unknown, with the exception of the estimated total mass and angular velocity of the asteroid. The MPC is used to generate feed-forward trajectories and control input using only the mass and angular velocity of the asteroid combined with obstacle avoidance constraints. However, since the control input from MPC is calculated using only an approximated model of the asteroid, it fails to control the spacecraft in the presence of disturbances due to the asteroid’s irregular gravitational field. Hence, we propose an adaptive controller in conjunction with MPC to handle unknown disturbances. The numerical results presented in this work show that the novel control system is able to handle unknown disturbances while generating and tracking sub-optimal trajectories better than adaptive control or MPC solely

Adaptive Modified RISE-based Quadrotor Trajectory Tracking with Actuator Uncertainty Compensation

This paper presents an adaptive robust nonlinear control method, which achieves reliable trajectory tracking control for a quadrotor unmanned aerial vehicle in the presence of gyroscopic effects, rotor dynamics, and external disturbances. Through novel mathematical manipulation in the error system development, the quadrotor dynamics are expressed in a control-oriented form, which explicitly incorporates the uncertainty in the gyroscopic term and control actuation term. An adaptive robust nonlinear control law is then designed to stabilize both the position and attitude loops of the quadrotor system. A rigorous Lyapunov-based analysis is utilized to prove asymptotic trajectory tracking, where the region of convergence can be made arbitrarily large through judicious control gain selection. Moreover, the stability analysis formally addresses gyroscopic effects and actuator uncertainty. To illustrate the performance of the control law, comparative numerical simulation results are provided, which demonstrate the improved closed-loop performance achieved under varying levels of parametric uncertainty and disturbance magnitudes

Anaesthetic significance and management of a child with neonatal purpura fulminans

Protein C deficiency is a rare autosomal-dominant disorder of varying severity. Patients with homozygous and compound heterozygous protein C deficiency present with neonatal purpura fulminans (NPF). Other presentations usually include disseminated intravascular coagulation and venous thromboembolism. This disorder usually poses a unique anaesthetic challenge to the anaesthesiologist, requiring special precautions to prevent various intra- and post-operative complications. We hereby report the successful anaesthetic management of a 1-month-old infant who presented with NPF

Anesthetic management of peripartum cardiomyopathy using "epidural volume extension" technique: A case series

Peripartum cardiomyopathy is a rare cause of dilated cardiomyopathy in parturients, occurring in approximately one in 1000 deliveries, manifesting during the last few months or the first 5 months of the postpartum period. It can result in severe ventricular dysfunction during late puerperium. The major concern while managing these patients is to optimize fluid administration and avoid myocardial depression, while maintaining stable intraoperative hemodynamics. We present a case series of five parturients that were posted for elective cesarean section and managed successfully by the epidural volume extension technique

MadhurDixit13/MovieRecommender: MovieRecommender_v2.0.0

<p>Revamped UI with Integrated OMDB API!</p> <p>Experience our sleek, modern user interface with the power of the OMDB API seamlessly woven in. Now, you can easily access essential information from the movie database, including IMDb ratings and eye-catching posters. Say goodbye to the old and hello to the new and improved Movie Recommender! </p> <h2>What's Changed</h2> <ul> <li>Update README.md by @MadhurDixit13 in https://github.com/MadhurDixit13/MovieRecommender/pull/2</li> <li>Madhur by @MadhurDixit13 in https://github.com/MadhurDixit13/MovieRecommender/pull/1</li> <li>Madhur by @MadhurDixit13 in https://github.com/MadhurDixit13/MovieRecommender/pull/5</li> <li>Update workflow.yml by @MadhurDixit13 in https://github.com/MadhurDixit13/MovieRecommender/pull/8</li> <li>Madhur dixit13 patch 4 by @MadhurDixit13 in https://github.com/MadhurDixit13/MovieRecommender/pull/9</li> <li>Created Cards for predicted movies with poster and imdb ratings by @ATHARVA47 in https://github.com/MadhurDixit13/MovieRecommender/pull/15</li> </ul> <h2>New Contributors</h2> <ul> <li>@ATHARVA47 made their first contribution in https://github.com/MadhurDixit13/MovieRecommender/pull/15</li> </ul> <p><strong>Full Changelog</strong>: https://github.com/MadhurDixit13/MovieRecommender/commits/version2.0</p&gt