Redundant Thrusters Research Articles

Bioinspired Control Architecture for Adaptive and Resilient Navigation of Unmanned Underwater Vehicle in Monitoring Missions of Submerged Aquatic Vegetation Meadows.

Submerged aquatic vegetation plays a fundamental role as a habitat for the biodiversity of marine species. To carry out the research and monitoring of submerged aquatic vegetation more efficiently and accurately, it is important to use advanced technologies such as underwater robots. However, when conducting underwater missions to capture photographs and videos near submerged aquatic vegetation meadows, algae can become entangled in the propellers and cause vehicle failure. In this context, a neurobiologically inspired control architecture is proposed for the control of unmanned underwater vehicles with redundant thrusters. The proposed control architecture learns to control the underwater robot in a non-stationary environment and combines the associative learning method and vector associative map learning to generate transformations between the spatial and velocity coordinates in the robot actuator. The experimental results obtained show that the proposed control architecture exhibits notable resilience capabilities while maintaining its operation in the face of thruster failures. In the discussion of the results obtained, the importance of the proposed control architecture is highlighted in the context of the monitoring and conservation of underwater vegetation meadows. Its resilience, robustness, and adaptability capabilities make it an effective tool to face challenges and meet mission objectives in such critical environments.

A Design Method for Redundant Microthruster Layout With Allocation Error

The microthruster is generally chosen as the actuator of the drag‐free satellite control system, and the layout directly affects the stability of the satellite control. Due to the extremely rigorous objectives of drag‐free control, a design method for the redundant thruster layout is proposed in this paper to improve the control stability of the satellite and reduce the allocation error of the control system. First, the factors corresponding to the allocation errors of redundant thruster layouts are analyzed. And the minimum number of thrusters required for satellite control is determined through the calculation method of thruster redundancy. Then, the design criterion of reducing the allocation error and increasing the satellite control stability is put forward. To demonstrate the effectiveness and feasibility of the design method proposed in this paper, the space gravitational wave detection satellite is taken as a simulation case. Thrust distribution models corresponding to the designed thruster layouts are established, and the results show that a proper layout can not only improve stability but also reduce fuel consumption. The research is looking forward to providing a reference for designing the microthruster layout of the gravitational wave detection satellite in the future.

Lightweight underwater robot developed for archaeological surveys and excavations

This paper reports the development of a lightweight remotely operated vehicle that performs underwater excavation work for archaeological surveys. Discovering underwater artifacts is generally difficult because they are in high risk areas and are often covered with sediment. To discover them, divers and large remotely operated vehicles must conduct excavation work with a manipulator(s). Nevertheless, accomplishing such tasks is difficult for small and portable underwater robots without a manipulator(s). As described herein, we developed a lightweight underwater robot of 35 kg that can remove sediment from the seabed or lake bottom using its thrusters instead of a manipulator. Numerous redundant thrusters are equipped with the robot to compensate the reaction force of the thrusters for sediment removal. Eight thrusters are arranged not only for sediment removal but also for fine maneuvering. First, through preliminary experiments, we investigated the potential use of a water flow generated using a pair of small marine thrusters to remove surface sediment. Next, we described the design and development of a lightweight underwater robot with eight thrusters and high-definition cameras for archaeological surveys. Finally, we conducted field experiments to demonstrate the sediment removal performance and usefulness of the developed robot.

Adaptive Robust Fault-Tolerant Regulation of Mechatronic Systems with Prescribed-Time Convergence

In this paper, we propose a synchronized prescribed-time control strategy for a class of nonlinear mechatronic systems with external disturbance, actuation saturation, and actuator faults, which features simultaneous translational and rotational motion tracking in the same prescribed time. Dual quaternion is employed to model the coupling effect between translational and rotational motions, which provides a unified representation for describing multiple degree-of-freedom motions. In addition, online adaptive technology is incorporated for real-time monitoring and separation of actuator failure information. The adaptive capability of the controller to parameter perturbation, disturbance, and fault deviation is therefore enhanced. Furthermore, the closed-loop system is featured by L2 gain stability/robustness against thrust output deviation, while the system trajectory is guaranteed to converge with user-defined settling time. Finally, numerical simulations on a microsatellite platform with redundant thrusters are performed to verify the effectiveness of the proposed fault-tolerant control approach.

Research on Modeling and Fault-Tolerant Control of Distributed Electric Propulsion Aircraft

Distributed electric propulsion (DEP) aircrafts have high propulsion efficiency and low fuel consumption, which is very promising for propulsion. The redundant thrusters of DEP aircrafts increase the risk of fault in the propulsion system, so it is necessary to study fault-tolerant control to ensure flight safety. There has been little research on coordinated thrust control, and research on fault-tolerant control of the propulsion system for DEP aircrafts is also in the preliminary stage. In this study, a mathematical model of DEP aircrafts was built. Aiming at the lateral and longitudinal control of DEP aircrafts, a coordinated thrust control method based on total energy control and total heading control was designed. Furthermore, a fault-tolerant control strategy and control method was developed for faults in the propulsion system. Simulation results showed that the controller could control the thrust to the prefault level. The correctness and effectiveness of the designed coordinated thrust control method and the fault-tolerant control method for DEP aircrafts were theoretically verified. This study provides a theoretical basis for future engineering application and development of the control system for DEP aircrafts.

Distributed optimal control allocation for 6-dof spacecraft with redundant thrusters

Control allocation for 6-dof spacecraft maneuvers is considered. Retired spacecraft, whose own control system is inoperable, can be reused by installing multiple cellular thruster modules to provide thrusts for translational and rotational control. Such cellular thruster modules collaborate with their neighbors in a network topology to calculate an optimal distribution matrix for thrust allocation. A pseudo-inverse optimal thrust allocation scheme is extended to a distributed iteration algorithm to enable this optimal problem to be solved by cellular thruster modules in a distributed manner. Subsequently, a norm-based distributed pseudo-inverse optimal thrust allocation scheme is developed to solve the same optimal thrust allocation problem. The syntheses of two distributed optimal thrust allocation schemes are discussed. Numerical simulations are demonstrated in the end to show the effectiveness of two proposed distributed thrust allocation schemes. Performance comparisons between two schemes are analyzed as well.

Control Allocation for Redundant Thruster of a Spacecraft via Direction-Preserving Approach in Simplex Algorithm

در این مقاله استفاده از روش برنامه‌ریزی خطی در تخصیص‌گر کنترلی جهت استفاده در زیرسیستم کنترل وضعیت فضاپیما با تراسترهای افزونه مورد مطالعه قرار گرفته است. از الگوریتم سیمپلکس به ‌عنوان حل‌کننده برتر و از دو رویکرد حفظ راستا و حفظ راستای اصلاحی بودسون به ‌عنوان رویکردهای برگزیده در مواجهه با جواب‌های غیرقابل دستیابی استفاده شده است. همچنین کارکرد مناسب این رویکردها با پدیده خرابی تراسترها نیز مورد ارزیابی قرار گرفته است. نتایج بیانگر آن هستند که رویکرد حفظ راستا دارای زمان پردازش و مصرف سوخت کمتر است؛ اما روش حفظ راستای اصلاحی بودسون زمان پردازش و مصرف سوخت بیشتر داشته و البته دارای خطای ردگیری سه محوره کمتری است. لازم به ذکر است کنترلر PD به‌عنوان قانون کنترلی فضاپیما استفاده شده و شبیه‌سازی برای تعداد و چیدمان تراستر مشخص صورت پذیرفته است.

A new approach in three-axis satellite stabilisation using redundant thruster in elliptical orbit

Three-axis attitude stabilisation of a satellite in a LEO elliptical orbit, with respect to the effects of applied disturbances such as eccentricity, gravity gradient, solar radiation pressure and aerodynamic loads is presented by applying three reaction wheel actuators. A new attitude stabilisation method is investigated by considering failure in one or more reaction wheels. If any failure happens in reaction wheels, redundant thruster will be added to the system by gimbal mechanism as an input controlling actuator. Control algorithm based on dynamic and kinematic equations of the satellite's motion is developed. Considering the variable satellite model in different situations, neuro-fuzzy controller is employed. For training the intelligent neuro-fuzzy controller, PID controller is utilised. Numerical simulations show that the recommend control method has acceptable results and supplementing of a thruster actuator as redundancy, could increase the space mission reliability.

A new approach in three-axis satellite stabilisation using redundant thruster in elliptical orbit

A new approach in three-axis satellite stabilisation using redundant thruster in elliptical orbit

Finite time attitude takeover control for combination via tethered space robot

Up to April 6, 2016, there are 17,385 large debris in orbit around the Earth, which poses a serious hazard to near-Earth space activities. As a promising on-orbit debris capture strategy, tethered space robots (TSRs) have wide applications in future on-orbit service owing to its flexibility and great workspace. However, lots of problems may arise in the Tethered Space Robots (TSRs) system from the approaching, capturing, postcapturing and towing phases. The postcapture combination attitude takeover control by the TSR is studied in this paper. Taking control constraints, tether oscillations and external disturbances into consideration, a fast terminal sliding mode control (FTSMC) methodology with dual closed loops for the flexible combination attitude takeover control is designed. The unknown upper bounds of the uncertainties, external disturbances are estimated through adaptive techniques. Stability of the dual closed loop control system and finite time convergence of system states are proved via Lyapunov stability theory. Besides, null space intersection control allocation was adopted to distribute the required control moment over TSR's redundant thrusters. Simulation studies have been conducted to demonstrate the effectiveness of the proposed controller with the conventional sliding mode control(SMC).

Attitude Control of Chaotic Satellite with Unknown Input and uncertainties based on Sliding Control

attitude control of missiles, spacecraft and satellites is essential; in order to remain them fixed in space to perform their missions accurately. The attitude equation of a satellite is a six- dimensional nonlinear system which includes some types of nonlinear behavior such as periodic trajectory, chaotic dynamics. In this paper, a sliding mode control design method for stabilization of the attitude chaotic satellites with unknown inputs and uncertainties. Using Lyapunov theory, the stability control system is proven. Simulation results show that the proposed controller can be chaotic satellite attitude in the presence of unknown inputs and uncertainties will converge to the unstable equilibrium points. In this section, the satellite system and the chaotic dynamics are studied. In (16) the problem of satellite attitude control with redundant thrusters, and in (17) satellite attitude control with an uneven inertia distribution has been investigated. However, given that the satellite attitude motion under external disturbances becomes chaotic mode, the control satellite system will be very complex. So, be very careful satellite control system is designed. In (13) and (14) satellite attitude control of chaotic behavior has been investigated. The orientation of the satellite at a given point can be locally described in terms of three angles

Optimal Thrust Allocation for Semisubmersible Oil Rig Platforms Using Improved Harmony Search Algorithm

Deep-water offshore drilling vessels, such as a semisubmersible drilling rig, use the dynamic positioning (DP) system and the thruster-assisted position-mooring system for maintaining a stationary position. In the DP system, the thrust allocator is used to distribute the desired generalized forces computed by the motion controller among the thrusters. However, to ensure safe operation of the vessel despite the thruster failure, the vessel is equipped with redundant thruster configuration and, therefore, is overactuated. For overactuated vessels, the choice of a particular solution for thrust allocation is found using some kind of optimization process. In this paper, the thrust allocator tries to minimize the power consumption and takes forbidden/spoil zones into account. The formulated thrust allocation problem becomes nonconvex due to thrust direction constraints on azimuth thrusters. The conventional methods get trapped in local minima and fail to find the optimum solution for the formulated nonconvex thrust allocation problem. In this paper, an improved harmony search (IHS) algorithm for solving the nonconvex thrust allocation problem is proposed. IHS is a variant of the harmony search (HS) algorithm. The HS algorithm is a music-based meta-heuristic optimization method, which is analogous with the music improvisation process where a musician continues to polish the pitches to obtain better harmony. Obtained numerical results show that the IHS algorithm has better convergence property when compared to the HS algorithm and the genetic algorithm (GA). Moreover, the power consumption for thrust allocation using the IHS algorithm is lower when compared with HS, GA, and Mincon (sequential quadratic programming) algorithms. The percentage savings in total power consumption for thruster allocation as compared to the Mincon algorithm for GA, HS, and IHS methods are 44.96%, 48.39%, and 51.58%, respectively.

Fault-Tolerant Region-Based Control of an Underwater Vehicle with Kinematically Redundant Thrusters

This paper presents a new control approach for an underwater vehicle with a kinematically redundant thruster system. This control scheme is derived based on a fault-tolerant decomposition for thruster force allocation and a region control scheme for the tracking objective. Given a redundant thruster system, that is, six or more pairs of thrusters are used, the proposed redundancy resolution and region control scheme determine the number of thruster faults, as well as providing the reference thruster forces in order to keep the underwater vehicle within the desired region. The stability of the presented control law is proven in the sense of a Lyapunov function. Numerical simulations are performed with an omnidirectional underwater vehicle and the results of the proposed scheme illustrate the effectiveness in terms of optimizing the thruster forces.

Robust Control Allocation among Overactuated Spacecraft Thrusters under Ellipsoidal Uncertainty

Spacecrafts with overactuated and redundant thrusters can work normally once some of them are out of work, which improves the reliability of spacecraft in orbit. In this way, the desired command of controller needs to be dynamically allocated among thrusters. Considering that uncertain factors may appear in forms of dynamics, installation errors, thrust deviations, or failures, this paper proposes a robust control allocation under ellipsoidal uncertainty. This method uses the uncertainty ellipsoid set to describe the uncertainty of the thrusters firstly and establish the thrust allocation robust reference model and then transforms it into a cone optimization model which can be solved as an optimized problem. Finally, this paper adopts the interior-point method for solving the optimization problem. In this way, difficulties of solving the problem caused by parameter uncertainties are avoided effectively. Finally, we take satellite rendezvous and docking as simulation scenarios; it is verified that the cumulative distribution error and maximum error can be reduced by more than 15% when the random error of control efficiency matrix is 5%–20%; also, precision of thruster allocation is improved.

Velocity-free fault-tolerant control allocation for flexible spacecraft with redundant thrusters

This paper proposes a novel velocity-free nonlinear proportional-integral (PI) control allocation scheme for fault-tolerant attitude control of flexible spacecraft under thruster redundancy. More specifically, the nonlinear PI controller for attitude stabilisation without using body angular velocity measurements is first designed as a virtual control of the control allocator to produce the three-axis moments, and can ultimately guarantee uniform boundedness of the closed-loop system in the presence of external disturbances and possible faults. The associated stability proof is constructive and accomplished by the development of passivity filter formulations together with the choice of a Lyapunov function containing mixed terms involving the various states. Then, a robust least-squares-based control allocation is employed to deal with the problem of distributing the three-axis moments over the available thrusters under redundancy, in which the focus of this control allocation is to find the optimal control vector of the actuator by minimising the worst-case residual, under the condition of thruster faults and control constraints like saturation. Simulation results using the orbiting flexible spacecraft model show good performance under external disturbances and even in different thruster fault scenarios, which validates the effectiveness and feasibility of the proposed scheme.

Mass and Cost Model for Selecting Thruster Size in Electric Propulsion Systems

A model of system mass and life-cycle costs is used to determine the optimal number of thrusters for electric propulsion systems. The model is generalized for application with most electric propulsion systems and then applied to high-power Hall thruster systems in particular. Mass and cost models were constructed for individual thruster strings using as inputs the number of active thrusters, the number of redundant thrusters, and the total system power. Mass and cost are related through the launch cost of the propulsion-system mass, which unifies the optimization to a single global parameter based on cost. Fault-tolerance and string cost are driving factors determining the optimum thruster size for a given system-power level. After considering factors such as fault-tolerance, cost uncertainty, complexity, ground-test-vacuum-facility limitations, previously demonstrated power capabilities, and possible technology limitations, the development of two thrusters to flight status is suggested: a low-power model operating at 20–50 kW per thruster to support missions up to 500 kW system power and the development of a high-power model operating at 50–100 kW per thruster to support missions up to 1 MW system power.

Fault tolerant control with H ∞ performance for attitude tracking of flexible spacecraft

A fault-tolerant control scheme with thruster redundancy is developed and applied to perform attitude tracking manoeuvres for an orbiting flexible spacecraft. Based on the assumption of bounded elastic vibrations, an adaptive sliding mode controller is proposed to guarantee that all the signals of the resulting closed-loop attitude system are uniformly ultimately bounded in the presence of an unknown inertia matrix, bounded disturbances and unknown faults. An H ∞ performance index is introduced to describe the disturbance attenuation performance of the closed-loop system. This approach is then extended to the problem of elastic vibration without knowledge of the bounds a priori. The presented approach addresses thruster saturation limits and the desired thruster force is guaranteed to stay within the limit of each thruster. Extensive simulation studies have been conducted to demonstrate the closed-loop performance benefits compared to conventional control schemes.

Attitude control of a satellite with redundant thrusters

Redundant thrusters are generally used for a reliable attitude control system. Also, redundant thrusters yield a better performance if they are used appropriately. In this paper, the authors propose an efficient redundancy management algorithm to reduce the fuel consumption. The algorithm is based on a linear programming problem which is a constrained optimization problem. For the algorithm, a cost function is defined as a quantity related to the fuel consumption for a maneuver. The independent variables are the thrusters' on-times which are control input variables of a satellite dynamic model. The advantage of the proposed method is verified by numerical examples. The examples show that the proposed method consumes less fuel than an existing method for a given maneuvering command. A sub-optimal algorithm is also discussed for an onboard computation. The proposed algorithm is applied to two maneuvers: move-to-rest and rest-to-rest. This is verified by a numerical simulation.

Reconfiguration of Redundant Thrusters by Allocation Method

Thrusters are important actuators where air is rare. Since the maintenance or replacement of thrusters is not easy in such an environment, a thrusting system must be highly reliable. Redundant thrusters are used to meet the reliability requirement. In this paper, a reconfiguration problem for those redundant thrusters is discussed, especially the management or distribution logic of redundant thrusters is focused on. The logic has to be changed if faults occur at thrusters. Reconfiguration is to change the distribution logic to accommodate thrusters' faults. The authors propose a reconfiguration algorithm based on the linear programming method. The authors define the reconfiguration problem as an optimization problem. The performance index is a quantity related with total fuel consumption by thrusters. This algorithm can accommodate multiple faults. Numerical examples are given to show the advantage of the proposed algorithm over existing methods.

여유 조종력 할당기법을 이용한 인공위성의 여유 추력기 제어

Redundant thrusters are generally adopted to satellite designs for a highly reliable attitude control system. So efficient redundancy management is required to take advantage of these redundant thrusters. In this paper, control allocation method is proposed as a method for controlling redundant thrusters. Control allocation is a method to calculate optimal distribution on redundant controls for realizing desired forces/torques. It is shown that a control allocation problem for redundant thrusters is formulated as a linear programming problem which minimizes fuel consumptions with thrusters, constraints. We also show that the proposed method is more efficient than an existing method by numerical examples.會ĀĀЀ؀؀㞓⁗Ɨ⨀梖ﾖ⨀炏ﾖ⨀ Ԁ䭏䩉䌀䢕ﾖ⨀ﾖ⨀؀Ā碗ﾖ⨀ﾖ⨀袖ﾖ⨀ā☈會ĀĀЀḀḀ⃶㞓硖Ɨ⨀⢗ﾖ⨀炏ﾖ⨀☈Ԁ噎彃一碖ﾖ⨀낖ﾖ⨀؀Ā肗ﾖ⨀낖ﾖ⨀ꂖﾖ⨀䢗ﾖ⨀ȀĀﾖ⨀낖ﾖ⨀邒ﾖ⨀肗ﾖ⨀袗ﾖ⨀碗ﾖ⨀ԀȀ袖ﾖ⨀䢗ﾖ⨀䢗ﾖ⨀삗ﾖ⨀袖ﾖ⨀ЏȀЀ܀ԀȀ炏ﾖ⨀灮ﾖ⨀섆덀炒ﾖ⨀偮ﾖ⨀쀆䁧ʗ⨀
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