Jingrui Zhang

Attitude Control and Vibration Suppression for Flexible Spacecraft Using Control Moment Gyroscopes

AbstractThis paper presents a novel control strategy for attitude control and vibration suppression of flexible spacecraft. A set of control moment gyroscopes are distributed on the flexible structure of the spacecraft to provide control torques. The interactions between the control moment gyroscopes and the flexibilities of the structure are incorporated in the equations of motion. A nonlinear controller is first formulated to determine the desired control input for large angle three-axis attitude maneuvers and vibration suppression. Then, a steering law is designed to obtain the gimbal commands for the control moment gyroscopes. For the small attitude error stabilization, a simple adaptive controller is developed based on the linearized dynamic model. It can avoid the singularity issue of the control moment gyroscopes, while simultaneously achieving attitude stabilization and vibration suppression. Numerical examples demonstrate the efficacy of the proposed methods.

Placement optimization of actuators and sensors for gyroelastic body

Gyroelastic body refers to a flexible structure with a distribution of stored angular momentum provided by fly wheels or control moment gyroscopes. The angular momentum devices can exert active torques to the structure for vibration suppression or shape control. This article mainly focuses on the placement optimization issue of the actuators and sensors on the gyroelastic body. The control moment gyroscopes and angular rate sensors are adopted as actuators and sensors, respectively. The equations of motion of the gyroelastic body incorporating the detailed actuator dynamics are linearized to a loosely coupled state-space model. Two optimization approaches are developed for both constrained and unconstrained gyroelastic bodies. The first is based on the controllability and observability matrices of the system. It is only applicable to the collocated actuator and sensor pairs. The second criterion is formulated from the concept of controllable and observable subspaces. It is capable of handling the cases of both collocated and noncollocated actuator and sensor pairs. The illustrative examples of a cantilevered beam and an unconstrained plate demonstrate the clear physical meaning and rationality of the two proposed methods.

Dynamics and Trajectory Planning for Reconfigurable Space Multibody Robots

A free-floating space robot equipped with multiple reconfigurable manipulators is designed and investigated in this paper. Lockable passive cylindrical joints (PCJs) are utilized to make the manipulator have the ability of changing its length and twisted angle. Each cylindrical joint, connecting two adjacent rigid links, has no embedded actuators but a brake mechanism. Normally, the mechanism is locked during the operation. When in the reconfiguration stage, two manipulators grasp each other to form a closed loop. Then one PCJ is unlocked, whose relative rotation and translation can be changed by the active torques at other joints. This system is a typical space multibody system. The dynamics of the space robot with unlocked cylindrical joints and a closed structural loop is investigated. The equations of motion are derived through Maggi–Kane’s method. The obtained mathematical model is free of multipliers, which makes it suitable for controller design. A trajectory planning algorithm capable of avoiding the configuration singularity of the manipulators is proposed. A slide mode controller embedded with an extended state observer (ESO) is designed for the trajectory tracking control. Numerical simulations demonstrate the effectiveness of the trajectory planning and control strategy for the reconfiguration process. [DOI: 10.1115/1.4031055]

Optimal planning approaches with multiple impulses for rendezvous based on hybrid genetic algorithm and control method

In this article, we focus on safe and effective completion of a rendezvous and docking task by looking at planning approaches and control with fuel-optimal rendezvous for a target spacecraft running on a near-circular reference orbit. A variety of existent practical path constraints are considered, including the constraints of field of view, impulses, and passive safety. A rendezvous approach is calculated by using a hybrid genetic algorithm with those constraints. Furthermore, a control method of trajectory tracking is adopted to overcome the external disturbances. Based on Clohessy–Wiltshire equations, we first construct the mathematical model of optimal planning approaches of multiple impulses with path constraints. Second, we introduce the principle of hybrid genetic algorithm with both stronger global searching ability and local searching ability. We additionally explain the application of this algorithm in the problem of trajectory planning. Then, we give three-impulse simulation examples to acquire an optimal rendezvous trajectory with the path constraints presented in this article. The effectiveness and applicability of the tracking control method are verified with the optimal trajectory above as control objective through the numerical simulation.

Vibration Isolation Platform with Multiple Tuned Mass Dampers for Reaction Wheel on Satellites

Vibration isolation is a direct and effective approach to improve the ultraprecise pointing capability of an imaging satellite. To have a good trade-off between the resonance amplitude and the high frequency attenuation for the original vibration isolation platform, a novel vibration isolation system for reaction wheel (RW), including a multistrut vibration isolation platform and multiple tuned mass dampers, is proposed. The first step constructs the integrated satellite dynamic model including the RWs and the vibration isolation systems, while the static and dynamic imbalances of the rotor and base movements are considered in the modeling process. The transmissibility matrix of the vibration isolation system is then obtained, and its frequency domain characteristics are described. The third part presents the application of the vibration isolation system for RWs. The effective attenuation of RW disturbances by the new vibration isolation system is illustrated, and its safety performance is also verified. Finally, using the reasonable parameters of the vibration isolation system, its performance on the satellite is testified by numerical simulations. The study shows that the novel vibration isolation system presented cannot only be successfully applied to a satellite but also improve the attitude stability.

Optimal Station Keeping for XIPS Thrusters in Failure Mode under Eclipse Constraints

AbstractThe objective of this paper is to minimize fuel consumption needed for geostationary Earth orbit station keeping by Xenon Ion Propulsion System (XIPS) thrusters in failure mode under eclipse constraints. Two diagonal XIPS thruster pairs, each pair consisting of one north thruster and one south thruster, are mounted on the antinadir face of the satellite. In failure mode, only one diagonal thruster pair fires. The original failure-mode station-keeping strategy without consideration of the eclipse constraints fires the remaining diagonal thrusters a second time with equal duration in the vicinity of ∼0° or 180° right ascensions (RA), in addition to a first time in the vicinity of ∼90 and 270°RA, which also results in the problem of excessive fuel consumption. The eclipse constraints are considered in this paper and the feasible firing location for station keeping during eclipse time is established. A optimal failure-mode station-keeping strategy under eclipse constraints is presented with the firing...

Study of Time-Free Transfers into Libration Point Orbits with Multiple Constraints

Preliminary designs of time-free transfers connecting a low Earth orbit with a halo orbit around the sun–Earth L1 point are developed with impulse maneuver and multiple orbital element constraints....

A Two-Dimensional Generalized Electromagnetothermoelastic Diffusion Problem for a Rotating Half-Space

In the context of the theory of generalized thermoelastic diffusion, a two-dimensional generalized electromagnetothermoelastic problem with diffusion for a rotating half-space is investigated. The rotating half-space is placed in an external magnetic field with constant intensity and its bounding surface is subjected to a thermal shock and a chemical potential shock. The problem is formulated based on finite element method and the derived finite element equations are solved directly in time domain. The nondimensional temperature, displacement, stress, chemical potential, concentration, and induced magnetic field are obtained and illustrated graphically. The results show that all the considered variables have a nonzero value only in a bounded region and vanish identically outside this region, which fully demonstrates the nature of the finite speeds of thermoelastic wave and diffusive wave.

Path Planning and Collision Avoidance for a Multi-Arm Space Maneuverable Robot

In this paper, a path planning algorithm for a multi-arm space robot is proposed. The robot is capable of maneuvering on the exterior of a large space station. Based on the maneuver strategy, continuous and smooth trajectories of the manipulator end effectors are first determined via the polynomial interpolation method. Then, the kinematics describing the relation between the end effector and the joint angles as well as the platform are formulated. A Moore–Penrose pseudoinverse solution of the joint trajectories is calculated to describe the motion of the manipulators, particularly, considering the singularity avoidance. In addition, a collision detection algorithm is developed to estimate the security during operation. Constraints are formulated by considering collision avoidance, based on which a collision-free trajectory is optimized through the multiplier-penalty method. The numerical results of a triple-arm space robotic system are given to demonstrate the effectiveness of the proposed algorithms.

Dynamics and Control of Flexible Manipulators Using Variable-Speed Control Moment Gyros

In this paper, the variable-speed control moment gyros (VS-CMGs) are adopted as actuators for vibration suppression of space flexible manipulators. They are directly mounted on the flexible links of the manipulator. Such system can be viewed as a flexible multibody system in chain topology actuated by both joint motors and VS-CMGs. We first develop a general approach for establishing the system equations of motion through Kane’s method. Then, two controllers are designed for trajectory tracking and vibration suppression of the flexible manipulator: one is an inverse dynamics control, whereas the other is based on the singular perturbation method. The proposed two control strategies are applied to a free-flying platform with a flexible manipulator. Numerical results show that the VS-CMGs can significantly suppress the induced vibration of the flexible links during the large angle maneuver.