This paper presents an attitude regulation controller that is utilized by a nanosatellite, called Deorbiter CubeSat, intended for the removal of sizable debris from low Earth orbit. The controller is used to detumble an uncooperative debris object to which the Deorbiter CubeSat is attached. The spacecraft performs a rendezvous maneuver, attaches rigidly to the exterior of the target debris, and detumbles and steers it toward the deorbit altitude. Three reaction wheels, in a mutually-orthogonal configuration, are used to control the attitude of the combined CubeSat and debris system. Each reaction wheel is capable of producing about 20 mN·m of torque, and has a maximum momentum capacity of 60 mN·m·s. Since physical parameters of the debris to be detumbled, e.g., mass and moment of inertia, are not known a priori, or there are large uncertainties in their values, the detumbling controller estimates the unknown parameters in order to reduce the regulation error to zero over time. Simulation results show that the controller is able to fully detumble the CubeSat-debris system in a matter of minutes, without knowing the debris physical parameters in the beginning of the maneuver.

This paper presents an advice mechanism compatible with heterogeneous advisers that incorporates advice into the advisee's policy via a method guaranteeing convergence to an optimal policy. Further, the mechanism has the capability to use multiple advisers at each time step and decide when advice should be requested and accepted, such that the use of advice decreases over time. Experiments are formed with a simulated team of heterogeneous robots performing a foraging task. We show that the proposed mechanism can provide a performance improvement for homogeneous and heterogeneous robot teams, and the use of advice decreases over time. 

This paper details a concurrent attitude and orbit control method for a debris-removing nanosatellite, called deobriter CubeSat, during the rendezvous and synchronization maneuver with an uncontrollable tumbling debris object. The CubeSat is designed based on the utilization of an eight-unit form factor and commercially-available components with substantial space heritage, and is intended for the removal of sizable debris objects in low-Earth orbit. In particular, a low-thrust propulsion system is used for orbit control, as well as three reaction wheels allowing for a three-axis attitude control. Since the thruster can only produce force in one direction in the body frame, the spacecraft is considered to be underactuated. The controller employs the reaction wheels and the thruster to simultaneously rendezvous and synchronize the attitude of the CubeSat with the tumbling debris object, allowing for a concurrent attitude and position tracking. Detailed derivation of the concurrent controller is discussed, the effects of high-order derivatives are analyzed, and the stability of the system is proved. Simulation scenarios are created for two different thruster operation modes, namely, unsaturated thrust force and continuously-saturated thrust force, in order to verify the performance of the controller, as well as its robustness against gravity gradient disturbance torque and gravitational perturbation force.

This paper proposes a control method for space manipulators, involving concurrent operation of an optimal and a coordinated controller. The optimal controller moves center of mass of the base spacecraft to a desired position along an optimal rendezvous trajectory for minimizing the energy. The optimal control problem is solved through Calculus of Variations, using saturation functions to represent the physical limitations in thrust forces. The coordinated controller drives the arm end-effector to a desired pose (for rendezvousing with the target), as well as making the base attitude follow a desired profile. It also generates augmented reactive moments on the base spacecraft to ensure controlling its attitude when the base actuators reach their limits. Simulations of a realistic space manipulator model demonstrate the performance of the proposed concurrent control method.

Communication systems are adopting all‐software architectures, because of their scalability, extensibility, flexibility, and cost‐effectiveness. This paper introduces a concurrent approach to the development and verification of baseband systems for satellite ground operations based on the behaviour‐driven development methodology. The open‐source GNU Radio development kit is used for developing the software‐defined radio baseband signal processing, as well as simulating the satellite and realistic channel impairments. The system performance at the end shows deviations of less than 1 dB with respect to the ideal performance and the Green Book standards specified by the Consultative Committee for Space Data Systems.

Cornerstone design courses have become a major part of engineering curricula, where students with different personality types and learning styles work together to design, develop, build, and demonstrate the functionality of a prototype within the duration of a term. This study analyzes student and team performance against gender, personality types, and learning styles in a second-year engineering design course. Further, the correlations between several assessment mechanisms are studied, and the effects of three different instructional design approaches on students’ performance are explored. Data have been collected on student performance and psychometrics, including marks, gender, personality type, and learning style from 2001 to 2018. To identify students’ personality types and learning styles, Myers–Briggs Type Indicators (MBTI) and Neil Fleming’s Learning VARK tests were administered. To evaluate students’ performance in the course, a number of assessment mechanisms have been defined. Several statistical methods are used to analyze data, and to determine correlation between datasets. Over nearly two decades of marks, gender, MBTI, and VARK data for 2637 students are presented for an engineering design course. The results demonstrated that there was no significant difference in performance across most assessments based on gender or gender distribution on a team. A better performance was observed from VK bimodal and quadmodal learning styles in most assessment mechanisms. Further, certain MBTI groups, namely, judging types outperformed their peers in engineering design assessments, with interesting interplay between MBTI dimensions for specific assessments and team dynamics. Traditional assessment mechanisms, such as engineering notebook and design proposals, are shown to be good predictors of student success. Lastly, scaffolded design activities and front-loading of lecture content were shown to be beneficial for student learning. There is negligible performance difference between female and male students in the engineering design course. Students whose preferred learning styles align with the assessment themes showed better performance in the course. The outcomes of this paper can be readily applied by instructors for design of assessment mechanisms, course materials, team formation, and instructional design.

This paper studies the gait characteristics of a quadruped rover that mimics domestic cats, and attempts to optimize these characteristics. The kinematics and dynamics formulation of the rover’s three-dimensional model is developed, and its gait, pose and corresponding control parameters are computed to minimize torque or maximize speed, using a genetic algorithm. The optimization model consists of a set of equality and inequality constraints that ensure the feasibility and stability of the gaits, while considering the entire gait spectrum that feline species exhibit. The optimal gaits for minimizing the torque closely resemble lateral sequence gaiting, with a trotting behaviour as speed increases. A running gait is obtained at the maximum speed. The optimization results appear to conform to the biological observations of feline species, suggesting the tendency of conserving energy in biological gaiting.

This paper presents a new dynamic formulation as well as control scheme for space manipulators in order to drive the end-effector along a desired trajectory while minimizing the base disturbances caused by the arm movements. Through the new dynamic formulation, the end-effector is viewed as a virtual base, and the end-effector variables are also considered as generalized coordinates. As a result, joint controllers can be designed without having to solve for the inverse kinematics problem and computing the derivative of the generalized Jacobian matrix. Consequently, the joint control torque can be obtained analytically through the Lagrange multipliers method. Further, the joint control torque is also obtained through a quadratic programming problem in order to take into account the joint torque constraints. Several case studies are simulated to demonstrate the new control scheme and compare its performance with that of other controllers.

This paper investigates the attitude estimation capabilities of a debris-removing nanosatellite called deorbiter CubeSat. The spacecraft is designed based on the utilization of commercially-available components with long space heritage, which are embedded in an eight-unit form factor. The attitude estimation machinery employed in this work is a discrete-time, quaternion-based, extended Kalman filter, which utilizes measurements provided by a three-axis rate sensor, five sun sensors, and a three-axis magnetometer. To obtain a linear state-space model, gravity gradient and magnetic disturbance torques are included in the plant model, and the model is linearized with respect to the process noise and the states, namely the inertial angular velocities and the quaternions. measurements noises are modelled based on zero-mean Gaussian distributions, and are quantified based on the performance of the state-of-the-art, commercial-of-the-shelf devices. A Monte Carlo simulation is created to analyze the performance of the estimator against various initial angular velocities and quaternions, both in the sunlit and in the eclipsed portions of the orbit. In light of the results, the accuracy of the deorbiter CubeSat’s attitude knowledge is discussed.

The ascent prediction of high-altitude zero-pressure stratospheric balloons is an important aspect of targeted test flight. Prediction of the balloon ascent rate is the prerequisite for many of the flights as it helps in planning ballasting and valving manoeuvres. In this paper, a standard analytical model, a fuzzy model and a statistical regression model are developed and compared to predict the zero-pressure balloon ascent. The flight data is extracted from the Esrange balloon service system for zero-pressure balloons with different payload capability, and several potential explanatory variables are computed for every sampled climbed segment. For the fuzzy modelling approach, a fuzzy c-mean clustering algorithm is used for system identification and prediction. For the regression approach, a Gaussian process regression is used, and principal component analysis is applied for finding the significant inputs. The result shows that the data driven approaches are more efficient than the standard analytical model.