Dynamics and Control of a Flexible Solar Sail

Solar sail can merely make use of solar radiation pressure (SRP) force as the thrust for space missions. The attitude dynamics is obtained for the highly flexible solar sail with control vanes, sliding masses, and a gimbaled control boom. The vibration equations are derived considering the geometric nonlinearity of the sail structure subjected to the forces generated by the control vanes, solar radiation pressure (SRP), and sliding masses. Then the dynamic models for attitude/vibration controller design and dynamic simulation are obtained, respectively. The linear quadratic regulator (LQR) based and optimal proportional-integral (PI) based controllers are designed for the coupled attitude/vibration models with constant disturbance torques caused by the center-of-mass (cm)/center-of-pressure (cp) offset, respectively. It can be concluded from the theoretical analysis and simulation results that the optimal PI based controller performs better than the LQR based controller from the view of eliminating the steady-state errors. The responses with and without the geometrical nonlinearity are performed, and the differences are observed and analyzed. And some suggestions are also presented

Effect of acupotomy on nitric oxide synthase and beta-endorphin in third lumbar vertebrae transverse process syndrome model rats

AbstractObjectiveTo explore the long-term effects and pain relief mechanism of acupotomy by observing changes in nitric oxide synthase (NOS) and beta-endorphin (β-EP) in the hypothalamus, spinal cord, and peripheral blood of rats with third lumbar vertebrae (L3) transverse process syndrome.MethodsTwenty-eight SD rats were randomly assigned to normal, model, electroacupuncture (EA), and acupotomy group. The last three groups were put through an operation to emulate L3 transverse process syndrome. Fourteen days after the simulation operation, EA and acupotomy treatments were applied to the respective groups. Fifty-six days after the simulation operation, biochemistry tests and enzyme-linked immunosorbent assay were used to measure NOS and β-EP in the hypothalamus, spinal cord, and peripheral blood.ResultsRats with the simulation operation showed significantly higher levels of NOS and β-EP in the hypothalamus, spinal cord, and peripheral blood than those in the normal group. The EA and acupotomy groups had significantly lower levels of NOS and β-EP than those in the model group. There was no statistical difference between the EA and acupotomy groups.ConclusionEA and acupotomy treatments significantly lowered NOS and β-EP levels in the hypothalamus, spinal cord, and peripheral blood and alleviated L3 transverse process syndrome

Experimental study of phase equilibria in the systems PbO x -CaO and PbO x -CaO-SiO2

The reported experimental work on the systems PbO-CaO and PbO-CaO-SiO in air is part of a wider research program that combines experimental and thermodynamic computer modeling techniques to characterize zinc/lead industrial slags. Extensive experimental investigation by high-temperature equilibration and quenching techniques followed by electron probe microanalysis was carried out in the temperature range 640 °C to 1500 °C (913 to 1773 K) and in the composition ranges 0 to 65 mol pet SiO and 0 to 42 mol pet CaO. Liquidus and solidus data were reported for most of the primary phase fields. Liquidus surfaces in the systems CaO-Pb-O and PbO-CaO-SiO in air were completely reconstructed. Extensive solid solutions of PbO in α' dicalcium silicate and CaPbSiO, were measured

Nonlinear static analysis-based thrust for solar sail

An accurate thrust model is extremely important for the navigation and space mission of solar sails. The thrust is deeply affected by the deformation of the highly flexible structure. Thus, in this paper, the exact thrust models for two-point and infinite-point-connected sails are presented by calculating the static deformations for the sail support beam structure with geometrical nonlinearity based on the assumption that the deformation of the sail film coincides with the support beam. And the film is merely regarded as the structure that transfers the solar radiation pressure force to the support beam. The nonlinear finite element model of the support beam with the Von-Karman’s nonlinear strain–displacement relationships is obtained. Then the Newton iteration method is used to calculate the large deformation of the sail structure. The thrust-modification methods are proposed for the two-connected sail. The deformation of the two-point-connected sail is larger than the infinite-point-connected sail, and the thrust loss of the two-point-connected sail is larger than the infinite-point-connected sail by nonlinear static calculations. Some suggestions are given based on the calculation results and relevant analysis. The thrust model should be verified and modified by in-flight data in the future. </jats:p

Dynamics of the Space Tug System with a Short Tether

The dynamics of the space tug system with a short tether similar to the ROGER system during deorbiting is presented. The kinematical characteristic of this system is significantly different from the traditional tethered system as the tether is tensional and tensionless alternately during the deorbiting process. The dynamics obtained based on the methods for the traditional tethered system is not suitable for the space tug system. Therefore, a novel method for deriving dynamics for the deorbiting system similar to the ROGER system is proposed by adopting the orbital coordinates of the two spacecraft and the Euler angles of ROGER spacecraft as the generalized coordinates instead of in- and out-plane librations and the length of the tether and so forth. Then, the librations of the system are equivalently obtained using the orbital positions of the two spacecraft. At last, the geostationary orbit (GEO) and the orbit whose apogee is 300 km above GEO are chosen as the initial and target orbits, respectively, to perform the numerical simulations. The simulation results indicate that the dynamics can describe the characteristic of the tether-net system conveniently and accurately, and the deorbiting results are deeply affected by the initial conditions and parameters

A Multi-Leveled Coordinate for Multibody Mechanics

For a proper way of modelling and simulation, as well as the precise and completeness, and a new multi-level method named homogeneous tensor coordinate(HTC) was developed by improving the absolute nodal coordinate formulation(ANCF) and the homogeneous coordinates(HC). In HTC, a new form of 2×2 matrix was employed instead of angles, when the capacity of expression and calculation was increased at the same time. HTC has good performance in traditional rigid body mechanics, which especially suitable for multibody modelling. Therefore, the robotic engineering may benefit from this finding, and a new formulation for scientific research may also affect the physics although some mathematical problems are raised in matrix theory

A Multi-Leveled Coordinate for Multibody Mechanics

For a proper way of modelling and simulation, as well as the precise and completeness, and a new multi-level method named homogeneous tensor coordinate(HTC) was developed by improving the absolute nodal coordinate formulation(ANCF) and the homogeneous coordinates(HC). In HTC, a new form of 2×2 matrix was employed instead of angles, when the capacity of expression and calculation was increased at the same time. HTC has good performance in traditional rigid body mechanics, which especially suitable for multibody modelling. Therefore, the robotic engineering may benefit from this finding, and a new formulation for scientific research may also affect the physics although some mathematical problems are raised in matrix theory