Cui Hu-tao

Attitude and position determination scheme of lunar rovers basing on the celestial vectors observation

In lunar exploration mission, it is very critical to determine the attitude and position of the lunar rover with a high degree of accuracy both for exploration achievement of scientific goals and for safe navigation. In this paper we address the problem of determining the attitude and position on the moon surface and provide a celestial navigation algorithm for lunar rover autonomous navigation. A CCD sun sensor is used to provide lunar rovers a vector observation by sun imaging and sun vector is computed in the lunar navigation frame using ephemeris data. A CCD earth sensor is designed to provide another vector observation, the image processing and earth centroid computation based on nonlinear least square is described. Finally, the attitude estimate using q-method and the position propagation is presented, simulation experiments are conducted, that corroborate the presented algorithm.

Autonomous optical navigation for landing on asteroids

Purpose – In order to succeed in landing asteroids, good accuracy autonomous navigation is absolutely necessary. Aims to describe a new autonomous navigation algorithm.Design/methodology/approach – First, gray images of asteroid surface are acquired by optical navigation camera, and nature feature points are detected and tracked autonomously. Second, the directional vector from spacecraft to the center of each feature point can be computed from the image coordinates in camera focal plane. Then, LIDAR/LRF is directed to three feature points and the distances from spacecraft to feature points are obtained. Last, the relative position vector from spacecraft to the target asteroid is reconstructed base on measurement outputs of navigation cameras and laser light radar (laser range finder).Findings – Suppose the initial conditions presented in this paper, the autonomous optical navigation position error and velocity error are less than 1 m and 0.1 m/s, respectively; this navigation accuracy can satisfy the req...

Autonomous design of spacecraft attitude control based on normal matrix and genetic algorithm

The problem of autonomous robust attitude control for flexible spacecraft is considered. A novel autonomous design approach is introduced based on the normal matrix design theory of the multivariable control system, and the parameters of controller are optimized by genetic algorithm (GA). The robustness of proposed approach is independent of the parameters of the spacecraft attitude dynamics, including the inertia tensor of the spacecraft and the vibration of the flexible appendages. Under a class of feedback perturbation, named inverse additive perturbation, the robust stabilization criterion in normal matrix description is obtained based on the structure and numerical properties of spacecraft attitude dynamics, and this criterion converts the robustness requirement into a constrain to the control designing parameters. Applying this criterion into GA, the chromosome is shortened, and therefore the running of GA is effectively promoted. A design example shows the efficiency of the algorithm.

Large angular autonomous attitude maneuver of deep spacecraft using pseudospectral method

An autonomous large angular slew of deep spacecraft is studied, which is a key factor in the development of future spacecraft autonomous platform. The objective is to minimize some performance index and rotate the spacecraft to a desired attitude while subject to dynamic and geometric constraints. The investigated literature did not handle this problem very well either in performance or constraints consideration. In this paper, we propose a new approach based on pseudospectral method for autonomous attitude control, not only satisfies the nonconvex constraints but also optimizes performance. We approach this by two stages: (1) get the feasible path using RRT in Rodrigues space and (2) transform the optimal control problem to a nonlinear planning problem (NLP) utilizing Pseudospectral method. Finally, attitude path is obtained by solving the NLP with an initial value from (1). Simulation example is presented and discussed.

UPF based autonomous navigation scheme for deep space probe

Abstract The autonomous “celestial navigation scheme” for deep space probe departing from the earth and the autonomous “optical navigation scheme” for encountering object celestial body are presented. Then, aiming at the conditions that large initial estimation errors and non-Gaussian distribution of state or measurement errors may exist in orbit determination process of the two phases, UPF (unscented particle filter) is introduced into the navigation schemes. By tackling nonlinear and non-Gaussian problems, UPF overcomes the accuracy inuence brought by the traditional EKF (extended Kalman filter), UKF (unscented Kalman filter), and PF (particle filter) schemes in approximate treatment to nonlinear and non-Gaussian state model and measurement model. The numerical simulations demonstrate the feasibility and higher accuracy of the UPF navigation scheme.

RHC‐based attitude control of spacecraft under geometric constraints

Purpose – The purpose of this paper is to propose an attitude control algorithm for spacecraft with geometric constraints.Design/methodology/approach – The geometric constraint is reformulated as a quadratic form when quaternion is used as attitude parameter, then the constraint is proved to be nonconvex and is further transformed to a convex one. By designing a new constraint formulation to satisfy the real constraint in the predictive horizon, the attitude control problem is reshaped to a convex planning problem which is based on receding horizon control.Findings – The proposed algorithm is more effective in handling geometric constraints than previous research which used single step planning control.Practical implications – With novel improvements to current methods for steering spacecraft from one attitude to another with geometric constraints, great attitude maneuver path can be achieved to protect instruments and meanwhile satisfy mission requirements.Originality/value – The attitude control algorit...

Design for autonomous mission planning system

Because of indeterminateness of the environment and delay of the communication, deep space spacecraft is required to be autonomous. Planning technology is studied in order to realize the spacecraft autonomy. First, a multi‐agent planning system (MAPS) based on temporal constraint satisfaction is proposed for concurrency and distribution of spacecraft system. Second, timeline concept is used to describe simultaneous activity, continue time, resource and temporal constraints. Third, for every planning agent in the MAPS, its layered architecture is designed and planning algorithm based on the temporal constraint satisfaction is given in detail. Finally, taking some key subsystems of deep space explorer as an example, the prototype system of MAPS is implemented. The results show that with the communication and cooperation of the planning agents, the MAPS is able to produce complete plan for explorer mission quickly under the complex constraints of time and resource.

Orbit dynamics and control in the neighborhood of the asteroid's center point

According to the similarity of the equations of motion between around the asteroid and in the circular restricted three-body problem (CRTBP), equilibrium theory in CRTBP are introduced to the asteroids satellite orbital dynamics in this paper. Using this theory, we calculate the position of equilibrium point in body fixed frame and analyze the stability of these points. By choosing a suitable initial state, we eliminate the unbounded modal effects on the orbits, which have been the Halo-orbit and Lassjous-orbit around the asteroids equilibrium point. A small force controller based on linear feedback control law is also designed to keep the spacecrafts orbit round the norm orbit.

Research on Autonomous Navigation of Lunar Rovers for the Moon Exploration

In order to explore the moon more efficiently, it is very important to endow lunar rovers with increased autonomy both for exploration achievement of scientific goals and for safe navigation. In this paper, autonomous navigation techniques for lunar rovers are discussed, and an autonomous navigation scheme is presented. First, algorithm and technique of initial position determination of lunar rovers are introduced. Then, matched-features set is build by multi steps of image processing such as feature detection, feature tracking and feature matching. Based on the analysis of the image processing error, a two-stage estimation algorithm is used to estimate the motion, robust linear motion estimation is executed to estimate the motion initially and to reject the outliers, and Levenberg-Marquardt nonlinear estimation is used to estimate the motion precisely. The sun sensor is used to update the rovers heading periodically for long range navigation. Next, a weighted ZSSD algorithm is presented to estimate the image disparities by analyzing the traditional ZSSD. Finally, a virtual simulation system is constructed using the development tool of Open Inventor, this simulation system can provide stereo images for simulations of stereo vision and motion estimation techniques, simulation results are provided and future research work is addressed in the end.