Optimal Maneuver Research Articles

Spacecraft long-duration phasing maneuver optimization using hybrid approach

Before a manned orbital rendezvous mission, the target spacecraft usually performs several maneuvers to adjust the initial phase angle of the orbital rendezvous and to coordinate the injection of the chaser. This maneuvering process is referred to as the “target phasing mission”. This target phasing presents an orbital long-duration two-point boundary value problem. Further, when the maneuver revolution numbers are used as design variables, the target phasing maneuver's optimization becomes a mixed integer nonlinear programming problem. This paper presents a new optimization method for this phasing maneuver mission, employing a hybrid approach. First, we provide an approximate phasing optimization problem that considers the phase angle influences of node drift and orbital altitude decay. This problem is then optimized using a hybrid approach that integrates branch-and-bound and sequential quadratic programming. Second, a shooting iteration method is adopted to improve the solution to the approximate problem in order to satisfy the terminal constraints of high-precision numerical integration. The proposed method is then applied to an operational target phasing maneuver problem. The results lead to four major conclusions: (1) The proposed approximate phasing optimization model presents a good approximation of the operational mission. (2) The hybrid optimization approach can solve the approximate problem effectively, and the shooting iteration used to arrive at a high-precision solution converges steadily and rapidly. (3) Compared with mixed-code genetic algorithm, the proposed method can obtain a similar result with a lower computation cost and, compared with the approximate model that does not consider node drift and orbital altitude decay, the proposed method has better convergence efficiency. (4) The terminal time of target phasing remains almost constant when the initial semi-major axis increases in a limited interval, and the transition appears only when there is a change in the terminal revolution number.

Strategies to minimize the fuel consumption of passenger cars during car-following scenarios

The way in which a vehicle is driven significantly affects its fuel consumption. This paper analyses the fuel-optimal driving strategies of a traditional vehicle equipped with a continuously variable transmission in car-following scenarios. A minimal-fuel-consumption problem is formulated, which is numerically solved using the Gauss pseudospectral method. The identified optimal manoeuvres were found to demonstrate two types of behaviour depending on the vehicle speed: pulse-and-gliding (PnG) and constant speed (CS). Further analyses indicate that the difference in behaviours mainly depends on the engine fuelling characteristics (both static and transient) and the road load. As the preceding vehicle’s speed increases, the optimal manoeuvre changes from partial PnG to full PnG, and finally to CS. In the full-PnG strategy, the engine switches between the minimum brake specific fuel consumption point and the idling point while the range error oscillates between its upper and lower bounds. The period, duty cycle percentage, and fuel economy improvement of the PnG strategy are analysed and presented.

Bearings-only target localization for unmanned underwater vehicles

This paper reports on target localization for autonomous underwater vehicles (AUVs) with acoustic bearing sensors where the bearing sensor provides detection and beamforming capabilities and reports target bearings with the associated measurement uncertainties. Estimating the state of a moving target using a bearing sensor on a moving platform is a difficult problem due to both the nonlinear nature of the measurement equations with respect to the unknown target parameters but also the observability conditions for the unknown parameters which require the observer to maneuver. This paper will report on a maximum likelihood (ML) method using Levenberg–Marquardt (LM) optimization for estimating the target state parameters. A known issue with ML solutions to this problem is that the algorithm may have difficulty reaching the global minimum unless the initial solution guess is close to the true solution. This paper will report on a genetic algorithm approach to making the initial solution guess. The performance of this approach, obtained from Matlab simulation, is presented. The implementation of the algorithms in the MOOS architecture is described using a very fast Lapack implementation for the LM parameter estimation to support the goal of optimal AUV maneuvering to improve the target state estimate.

Optimization of transition maneuvers through aerodynamic vectoring

This paper discusses the optimization of transition maneuvers between hover and cruise for small aircraft using a novel aerodynamic vectoring feature, which is achieved by allowing the wing to have variable incidence angle with respect to the fuselage. Compared to the fixed-wing aircraft case, the angle of incidence of the wing provides an additional independent control variable in the optimization problem formulation. The objective of the study is to achieve a transition scheme with minimal variation in altitude and reasonable thrust-to-weight ratio under specified transition time. The aerodynamics of the aircraft in pre- and post-stall regimes are obtained through wind-tunnel tests. The unsteady aerodynamic effects are incorporated in aerodynamic model to cater for rapid changes in the aircraft motion, which is modeled as three degree of freedom longitudinal dynamics. A nonlinear constrained optimization scheme based on Sequential Quadratic Programming (SQP) is used to generate the optimal maneuver motions. The results are discussed in light of their comparison with the fixed-wing case.

Chang’E-2 satellite asymmetric-descent orbit control technology

To accomplish high-resolution imaging of the preselected landing area, it was necessary for the Chang’E-2 mission to perform orbital maneuvering on the far side of the moon to meet the conditional height requirement of the imaging area. Engine shutdown would be executed invisibly on the back side of the moon if the descent maneuver mode opposite to the target perilune or the fuel optimal maneuver mode was used. To ensure the satellite safety, the project collectivety required that the engine shutdown should be designed to be executed in the domestic segmental arcs and meet the requirement of satellite emergency treatment simultaneously. Accordingly, the asymmetric-descent orbit control technology was adopted by offsetting the maneuver point, which obtained the orbit control parameters of finite-thrust mode with an iteration algorithm and modified the results with target perilune drift estimation. The Chang’E-2 satellite declined to the target of 100 km×15 km orbit successfully on 26 October 2010, and has been flying for 32 circles in the experimental orbit to accomplish the preselected landing area imaging. This paper describes the mechanism and realization method of the asymmetric-descent orbit control technology and evaluates the maneuver effect with the actual mission data.

Autonomous Pedestrian Collision Avoidance Using a Fuzzy Steering Controller

Collision avoidance is one of the most difficult and challenging automatic driving operations in the domain of intelligent vehicles. In emergency situations, human drivers are more likely to brake than to steer, although the optimal maneuver would, more frequently, be steering alone. This statement suggests the use of automatic steering as a promising solution to avoid accidents in the future. The objective of this paper is to provide a collision avoidance system (CAS) for autonomous vehicles, focusing on pedestrian collision avoidance. The detection component involves a stereo-vision-based pedestrian detection system that provides suitable measurements of the time to collision. The collision avoidance maneuver is performed using fuzzy controllers for the actuators that mimic human behavior and reactions, along with a high-precision Global Positioning System (GPS), which provides the information needed for the autonomous navigation. The proposed system is evaluated in two steps. First, drivers' behavior and sensor accuracy are studied in experiments carried out by manual driving. This study will be used to define the parameters of the second step, in which automatic pedestrian collision avoidance is carried out at speeds of up to 30 km/h. The performed field tests provided encouraging results and proved the viability of the proposed approach.

An Optimal Satellite Antenna Profile Using Reinforcement Learning

This paper addresses a detailed procedure to generate an optimal satellite antenna profile. The goal of antenna profile is to provide a sequence of commands for antenna movements such that the antenna directs as many ground station as possible under some constraints. The main task in generating the antenna profile is to schedule the antenna movements taking account of satellite orbit and attitude at all time points, given a mission trajectory. To generate the antenna profile, it is necessary to transform the direction of antenna from the antenna body frame to the satellite body frame and from the satellite body frame to the earth-centered fixed frame. For an optimal tracking of ground station, we generate a maneuvering sequence of azimuth and elevation angles of the antenna considering the projected beamwidth of the antenna on the ground, the off-pointing boundary, and the pointing errors. An optimal maneuvering sequence is generated by reinforcement learning (RL), which is an optimization search algorithm based on penalties and rewards obtained iteratively as episode increases. Through numerical simulations and with actual satellite data, the effectiveness of using RL is illustrated.

Handling of conjuction warnings in Eumetsat flight dynamics

Metop is the space segment of the EUMETSAT Polar System (EPS), Europe's first polar orbiting operational meteorological satellite system. Since end of 2008, EUMETSAT has been receiving conjunction warning messages from JSpOC (Joint Space Operations Centre of the US Air-Force) for Metop-A based on the high accuracy orbits estimated by the US space surveillance network. EUMETSAT Flight Dynamics team started then developing a set of software prototypes and operational procedures to properly handle the conjunction warning messages to first identify conjunctions with unacceptable level of collision risk and then, if deemed necessary, compute the optimal maneuver permitting to reduce the collision risk to negligible values.The paper will present in detail the received data and the analysis performed to evaluate their suitability for operational use, the functionalities of the developed software prototypes, the status of the operational procedures and the results obtained for the most interesting operational cases.

Optimal transition maneuvers for a class of V/STOL aircraft

This paper focuses on the problem of computing optimal transition maneuvers for a particular class of tail-sitter aircraft able to switch their flight configuration from hover to level flight and vice versa. Both minimum-time and minimum-energy optimal transition problems are formulated and solved numerically in order to compute reference maneuvers to be employed by the onboard flight control system to change the current flight condition. In order to guide the numerical computation and to validate its results, in a first stage approximated solutions are obtained as a combination of a finite number of motion primitives corresponding to analytical trajectories of approximated dynamic models. The approximated solution is then employed to generate an initial guess for the numerical computation applied to a more accurate dynamic model. Numerical trajectories computed for a small scale prototype of tail-sitter aircraft are finally presented, showing the effectiveness of the proposed methodology to deal with the complex dynamics governing this kind of systems.

An Investigation of a 3-PRS Parallel Motion Mechanism with Intersecting Rails

This study proposes a 3-axis AC servo motor parallel platform with intersecting rails. The 3-actuators are designed to be horizontally on the base platform with their extensions intersect in the base platform center. The forward kinematics, inverse kinematics and work space of this mechanism are established and the singularity distribution is investigated. Optimal maneuvering regions are recommended from the viewpoints of singularity and stiffness.

Evader maneuver on consideration of energy consumption in flight vehicle interception scenarios

To solve the problem of interception avoidance of flight vehicle, this paper comprehensively considers miss distance, energy consumption and prediction uncertainty on the final time of interception by a finite-time H ∞ performance measure, and designs optimal energy consumption maneuver. An optimal interception against optimal evader maneuver of flight vehicle is also presented. The results show that the best evader effect will be achieved under condition of a large amplitude evader maneuver at the end of interception if the flight vehicle can predict the final time of interception accurately, and a large interception miss distance will be gained at a relatively small energy consumption.

Engagement Tactics for Two Missiles Against an Optimally Maneuvering Aircraft

The engagement tactics for two missiles to attack an aircraft are studied. A tail chase scenario between two aircraft is assumed where the attacker tries to kill the evader with two missiles, while the evader employs optimal maneuvers for avoiding two missiles. The algorithm to solve this optimal control problem is first developed. For the aircraft, in order to simultaneously maximize the miss distances against two missiles, a special type of performance index is introduced and the problems are solved by the solver based on the steepest ascent method. The result shows that the aircraft optimal maneuvers are divided into three patterns. Next, the optimal timing for the attacker to launch the two missiles, in order to minimize both miss distances against the aircraft is studied. The effect of their taking trajectory shaping is also studied.

Optimal Cooperative Pursuit and Evasion Strategies Against a Homing Missile

Optimal-control-based cooperative evasion and pursuit strategies are derived for an aircraft and its defending missile. The aircraft-defending missile team cooperates in actively protecting the aircraft from a homing missile. The cooperative strategies are derived assuming that the incoming homing missile is using a known linear guidance law. Linearized kinematics, arbitrary-order linear adversaries' dynamics, and perfect information are also assumed. Specific limiting cases are analyzed in which the attacking missile uses proportional navigation, augmented proportional navigation, or optimal guidance. The optimal one-on-one, noncooperative, aircraft evasion strategies from a missile using such guidance laws are also derived. For adversaries with first-order dynamics it is shown that depending on the initial conditions, and in contrast to the optimal one-on-one evasion strategy, the optimal cooperative target maneuver is either constant or arbitrary. These types of maneuvers are also the optimal ones for the defender missile. Simulation results confirm the usefulness and advantages of cooperation. Specifically, it is shown how the target can lure in the attacker, allowing its defender to intercept the attacking missile even in scenarios in which the defender's maneuverability is at a disadvantage compared with the attacking missile.

Optimal transfers between unstable periodic orbits using invariant manifolds

This paper presents a method to construct optimal transfers between unstable periodic orbits of differing energies using invariant manifolds. The transfers constructed in this method asymptotically depart the initial orbit on a trajectory contained within the unstable manifold of the initial orbit and later, asymptotically arrive at the final orbit on a trajectory contained within the stable manifold of the final orbit. Primer vector theory is applied to a transfer to determine the optimal maneuvers required to create the bridging trajectory that connects the unstable and stable manifold trajectories. Transfers are constructed between unstable periodic orbits in the Sun–Earth, Earth–Moon, and Jupiter-Europa three-body systems. Multiple solutions are found between the same initial and final orbits, where certain solutions retrace interior portions of the trajectory. All transfers created satisfy the conditions for optimality. The costs of transfers constructed using manifolds are compared to the costs of transfers constructed without the use of manifolds. In all cases, the total cost of the transfer is significantly lower when invariant manifolds are used in the transfer construction. In many cases, the transfers that employ invariant manifolds are three times more efficient, in terms of fuel expenditure, than the transfer that do not. The decrease in transfer cost is accompanied by an increase in transfer time of flight.

Optimal Maneuvers for Aircraft Conflict Resolution Based on Efficient Genetic Webs

The problem of designing optimal conflict-free maneuvers for planar multiple aircraft encounters is studied. The maneuvers propose suitable heading changes for aircraft in a cooperative manner. The new mathematical approach provides optimal aircraft trajectories to resolve a wide variety of conflicts, especially in the presence of high-altitude clear air turbulence (CAT), normally encountered during en-route flights. The proposed approach effectively uses Genetic Algorithms (GA), together with modified webs, to quickly find conflict-resolving maneuvers. Different case studies show the method is fast enough to be used for real-time applications when resolving conflicts involving two aircraft. It is also efficient enough to resolve conflicts involving as many as 26 aircraft, which would be helpful in designing acrobatic maneuvers or in congested airspaces where emergency plans are needed.

Framework for Establishing Limits of Tabular Aerodynamic Models for Flight Dynamics Analysis

This paper describes the use of Computational Fluid Dynamics for the generation and testing of tabular aerodynamic models for flight dynamics analysis. Manoeuvres for the AGARD Standard Dynamics Model wind tunnel geometry for a generic fighter are considered as a test case. Wind tunnel data is first used to validate the prediction of static and dynamic coefficients at both low and high angles, featuring complex vortical flow, with good agreement obtained at low and moderate angles of attack. Then the generation of aerodynamic tables is described based on an efficient data fusion approach. An optimisation is used to define time optimal manoeuvres based on these tables, including level flight trim, pull-ups at constant and varying incidence, and level and 90 degree turns. The manoeuvre description includes a definition of the aircraft states and also the control deflections to achieve the motion. The main point of the paper is then to assess the validity of the aerodynamic tables which were used to define the manoeuvres. This is done by replaying them, including the control surface motions, through the time accurate CFD code. The resulting forces and moments can be compared with the tabular values to assess the presence of inadequately modelled dynamic or unsteady effects. The agreement between the tables and the replay is demonstrated for slow manoeuvres. A study for the pull-up at increasing rates shows discrepancies which are ascribed to vortical flow hysteresis at elevated motion rates.

Accurate, reproducible measurement of acetone concentration in breath using selected ion flow tube-mass spectrometry

Using selected ion flow tube-mass spectrometry (SIFT-MS) for on-line analysis, we aimed to define the optimal single-exhalation breathing manoeuvre from which a measure of expired acetone concentration could be obtained. Using known acetone concentrations in vitro, we determined the instrument's accuracy, inter-measurement variability and dynamic response time. Further, we determined the effects of expiratory flow and volume on acetone concentration in the breath of 12 volunteers and calculated intra-individual coefficients of variation (CVs). At acetone concentrations of 600–3000 ppb on 30 days over 2 months there was an instrument measurement bias of 8% that did not change over time, inter-day and intra-day CVs were 5.6% and 0.0%, respectively, and the 10–90% response time was 500 ± 50 ms (mean ± SE). Acetone concentrations at exhalation flows of 193 ± 18 (mean ± SD) and 313 ± 32 ml s−1 were 619 ± 1.83 (geometric mean ± logSD) and 618 ± 1.82 ppb in the fraction 70–85% by volume of exhaled vital capacity (V70−85%) and 636 ± 1.82 (geometric mean ± logSD) and 631 ± 1.83 ppb in V85−100%. A difference was observed between acetone concentrations in the V70−85% and V85−100% fractions (p < 0.01), but flow had no effect. Median intra-individual CVs were 1.6–2.6%. On-line SIFT-MS measurement of acetone concentration in a single exhalation requires control of exhaled volume but not flow, and yields low intra-individual CVs and is potentially useful in approximating blood glucose and monitoring metabolic stress.

Simulation‐based Bayesian optimal design of aircraft trajectories for air traffic management

AbstractIn this paper, we consider a specific Air Traffic Management problem, where multiple aircraft in a specific region are required to reach a different target zone in the minimum expected time, while maintaining safe separation. The problem is complicated by the presence of random wind disturbances. We propose a realistic policy to automatically generate optimal and safe maneuvres for each aircraft. The parameters of the optimal policy are computed using a sequential Monte Carlo approach. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Computing short-time aircraft maneuvers using direct methods

This paper analyzes the applicability of direct methods to design optimal short-term spatial maneuvers for an unmanned vehicle in a faster than real-time scale. It starts by introducing different basic control schemes, which employ online trajectory generation. Next, it presents and analyzes the results obtained through two recently developed direct transcription (collocation) methods: the Gauss pseudospec-tral method and the Legendre-Gauss-Lobatto pseudosp ectral method. The achieved results are further compared with those found through the Pontryagin’s Maximum (Minimum) Principle, and the paper continues by providing another set of direct method simulations incorporating more realistic boundary conditions. Finally, the results obtained using the third direct method, based on inverse dynamics in the virtual domain, are presented and discussed.

Investigation of the influences of tyre—road friction and engine power on motorcycle racing performance by means of the optimal manoeuvre method

This paper investigates the influences of the tyre—road friction and of the maximum engine power on the performance of a racing motorcycle. For this purpose the optimal manoeuvre method is applied, which essentially simulates an ideal driver and computes the minimum lap time for a given motorcycle and a given track. The absolute performance of a racing motorcycle is strictly related to the braking and acceleration capabilities. Braking is limited by front- or rear-tyre skidding and by a stoppie event, whereas acceleration is limited by rear-tyre skidding and by a wheelie event. Furthermore, the engine power constitutes a limiting factor during propulsive phases. Effectively the weights of these limiting factors change with the tyre—road friction condition and with the engine power availability. As a consequence, the manoeuvrability of a racing motorcycle varies and riders need to adjust their strategies properly in order to achieve the best performances allowed in any condition. For this purpose a simple L-curve manoeuvre is considered in this paper. First, a detailed description is reported, and then brake and acceleration limiting conditions are considered with respect to a reference configuration. Next, a parametric analysis is carried out at variable friction and maximum engine power, and their influences on lap time are examined. Finally, two representative configurations are evidenced, i.e. lower friction and lower power; furthermore, brake and acceleration limiting conditions are derived analytically by means of a simplified motorcycle model. Accordingly, the representative manoeuvres are interpreted, and the influences of the friction and engine power on curve entering and curve exiting using optimal strategies is examined.