This paper presents a position control strategy for a planar active-passive-active (APA) underactuated manipulator with second-order nonholonomic characteristics. According to the structural characteristics of the planar APA system, we divide the system into two parts: a planar virtual Pendubot (PVP) and a planar virtual Acrobot (PVA). For the PVP, we mainly fulfill the target angle of the first link, which is calculated through the geometry method, and make the system stable. In this stage, via keeping the states of the third link being zero, the system is reduced to the PVP. Meanwhile, we design an open-loop control law based on the nilpotent approximation (NA) model of the PVP to make the second link stable and the first link stabilize at its target angle. Then, the planar APA system is reduced to a PVA with all links’ angular velocities being zero. For the PVA, we mainly realize the other two links’ target angles obtained via the particle swarm optimization (PSO) algorithm. Thus, the control objective of the planar APA system is achieved. Finally, above control strategy is verified by simulation results.
This paper deals with the fixed-time group consensus problem for multi-agent systems (MASs) subjected to exogenous disturbances. Firstly, two pinning control algorithms are constructed for MASs, which not only reduce the number of controllers but also achieve expected tracking consensus. Secondly, fixed-time group consensus is ensured by utilizing the algebraic graph theory, Lyapunov stability and fixed-time control technique. Finally, simulations are finally given for demonstrate the availability of the derived results.
Unlike a fully-actuated manipulator, the position-posture control of a planar underactuated manipulator (PUM) is more difficult, but the research on it is significant due to the wide practical applications. The existing control methods consider no external disturbance and are involved in the staged control idea, bringing the problems of nonsmooth control torque and time-consuming. A novel one-stage control approach is proposed in this paper for the position-posture control of a three-link PUM with the first free joint under the external disturbance. By analyzing the coupling relationship between its active joints and free joint, the position-posture control is transformed into the trajectory tracking control. Unlike the general trajectory planning, the trajectories of the active joints are planned to include several parameters. Meanwhile, the parameters are solved using a chaos particle swarm optimization algorithm to guarantee that all joint angles can reach to their desired angles. Then, to obtain the high trajectory tracking accuracy at every moment under the external disturbance, the nonlinear disturbance observer is constructed and a nonlinear fast terminal sliding mode tracking controller is designed. Finally, the feasibility and superiority of this strategy are verified via two simulations.
Discarded train brake shoes mainly consist of steel-backed friction material. To be better reutilized, its essential features and its interaction in cement-based material need to be studied. Consequently, particle size analysis, SEM, IR and TGA were used to investigate two types of waste brake shoes, i e, mechanical grinding friction reclaimed material of waste brake-shoe (G-FRMWBS) and pyrolysis-friction reclaimed materials of waste brake-shoe (P-FRMWBS). The latter exhibited less organic content, larger range of particle size distribution and smaller medium particle diameter. Both types contained inorganic particles of spherical and irregular shapes, striped with steel fiber. Upon isometric substituting fine aggregates, G-FRMWBS lifted the strength of mortar effectively that was increased by 16.6% and 17.5% when the replacing rate was 5%; the value went up to 19.2% and 19.2% when the replacing rate was 10%. Moreover, inclusion of FRMWBS enhanced the chloride penetration resistance, and optimized the pore characteristic and ITZ (interfacial transition zone) as well. 相似文献
In order to improve the oxidation resistance of Ti Al alloy, silicide coatings were prepared by pack cementation method at 1273, 1323, and 1373 K for 1-3 hours. Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffraction(XRD) were employed to investigate the microstructures and phase constitutions of the coatings. The experimental results show that all silicon deposition coatings have multi-layer structure. The microstructure and composition of silicide coatings strongly depend on siliconizing temperatures. In order to investigate the rate controlling step of pack siliconizing on Ti Al alloy, coating growth kinetics was analyzed by measuring the mass gains per unit area of silicided samples as a function of time and temperature. The results showed that the rate controlling step was gas-phase diffusion step and the growth rate constant(k) ranged from 1.53 mg~2/(cm~4·h~2) to 2.3 mg~2/(cm~4·h~2). Activation energy(Q) for the process was calculated as 109 k J/mol, determined by Arrhenius' equation: k = k0 exp[–Q/(RT)]. 相似文献
Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of Zn O thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped Zn O thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped Zn O thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10~(-4) Ω·cm and the highest carrier concentration of 1.86×10~(21) cm~(-3) can be obtained from Zn O thin films with an indium content of 5at% in the target. 相似文献
To measure miss distance for antiaircraft projectile,a radial velocity identification and positioning method with a single radar is proposed.By analyzing the spatial resolution of multi-frequency ranging radar,the discrimination and testing model of this radar for multi-targets (projectile and target) is established to analyze the systematic error of antiaircraft miss distance.Then through the aerial target flight test and contrast test with optical test equipment,the validity of the measurement method is verified.This new method has the potential to be used in the measurement of antiaircraft projectile miss distance. 相似文献
