Control algorithm for vehicle height adjustable system of hydro-pneumatic suspension based on LuGre model

In order to control the vehicle body position precisely,1/4 nonlinear mathematical model of hydro-pneumatic suspension is established,and the influence of the frictional force in a hydraulic cylinder is analyzed.The friction characteristics are described based on the LuGre model when the piston of a hydraulic actuator is operated at a low speed.Due to the fact parameters of the friction model are effected by the system condition,an adaptive friction compensation（AFC）controller is designed through the Backstepping method,and a dual-observer has been implemented to estimate the friction state.The global asymptotic convergence of a closed-loop system is proven by the Lyapunov theorem.The simulation results show that the positional accuracy of the adaptive friction compensation yiedls a significant improvement in the vehicle height adjustment as compared to the PID control,demonstrating the effectiveness of the adaptive fiction compensation method in the vehicle height adjustable system of the hydro-pneumatic suspension.

Antidepressant Effect of Shenwei Ningyu Tablets on Rat Chronic Stress Model and Mouse Tail Suspension Model

[Objectives]To explore the antidepressant effect of Shenwei Ningyu Tablet,a new antidepressant traditional Chinese medicine,on rat chronic stress depression model and mouse tail suspension models.[Methods]Rat chronic stress model:except for the normal group,the rats in other groups were given corresponding chronic stress,and administered by gavage 1 h before modeling,for a total of 21 d.The changes of each indicator before and after the experiment were observed through the body weight change,the sugar water test,and open field test.The relevant hormone levels were detected by radioimmunoassay.Mouse tail suspension depression model:after continuous administration for 7 d,the activity times was recorded with the mouse automatic recorder,and the mouse immobility time was recorded after tail suspension,to explore the effects of each administration group on the tail suspension immobility time of mice.[Results]Chronic stress depression model:21 d after modeling,compared with the normal group,rats in the model group exhibited significantly reduced body weight,sucrose preference index,and horizontal and vertical movement scores(P<0.05).Compared with the model group,the low-dose Shenwei Ningyu Tablets group had significant differences in the sugar water test,horizontal and vertical movement scores(P<0.05).In addition,all three dose groups of Shenwei Ningyu Tablets could effectively reduce the content of CRF in chronic stress model rats,and the low dose group could significantly reduce the ACTH level in model rats(P<0.05).Mouse tail suspension depression model:the immobility time after tail suspension in each administration group was significantly different from that in the model group(P<0.05).[Conclusions]Shenwei Ningyu Tablets has a certain anti-depression effect on both the rat chronic stress depression model and the mouse tail suspension depression model.

Active suspension with optimal control based on a full vehicle model

The 7-DOF model of a full vehicle with an active suspension is developed in this paper.The model is written into the state equation style.Actuator forces are treated as inputs in the state equations.Based on the basic optimal control theory,the optimal gains for the control system are figured out.So an optimal controller is developed and implemented using Matlab/Simulink,where the Riccati equation with coupling terms is deduced using the Hamilton equation.The all state feedback is chosen for the controller.The gains for all vehicle variables are traded off so that majority of indexes were up to optimal.The active suspension with optimal control is simulated in frequency domain and time domain separately,and compared with a passive suspension.Throughout all the simulation results,the optimal controller developed in this paper works well in the majority of instances.In all,the comfort and ride performance of the vehicle are improved under the active suspension with optimal control.

Optimization of suspension system of off-road vehicle for vehicle performance improvement

Vehicle suspension design includes a number of compromises to provide good leveling of stability and ride comfort. Optimization of off-road vehicle suspension system is one of the most effective methods, which could considerably enhance the vehicle stability and controllability. In this work, a comprehensive optimization of an off-read vehicle suspension system model was carried out using software ADAMS. The geometric parameters of suspension system were optimized using genetic algorithm (GA) in a way that ride comfort, handling and stability of vehicle were improved. The results of optimized suspension system and variations of geometric parameters due to road roughness and different steering angles were presented in ADAMS and the results of optimized and conventional suspension systems during various driving maneuvers were compared. The simulation results indicate that the camber angle variations decrease by the optimized suspension system, resulting in improved handling and ride comfort characteristics.

Establishing the need to model the actual state of stress along rock bolts

Proper design of rock bolt support in underground mines is critical to avoid incidents, accidents and loss of production. The traditional design approach only considers the axial(tensile) capacity and this is clearly not the situation in situ, where a rock bolt is subjected to both axial and shear/bending loads which determines its overall performance and failure behaviour. To demonstrate and analyse the shear displacement in bedded roof, scaled physical models of underground excavation were created. From the models it was found that the shear displacement between the layers depends on the vertical roof deformation and thickness of beds. To analyse the effect of combined loading on rock bolt design for suspension and beam building models, analytical methods were used to calculate the required spacing of rock bolt for a given safety factor. Numerical models were then created using Rocscience RS2 software to establish the stresses on the rock bolt. The results show a significant reduction in safety factor for suspension as demonstrated in an example(reduced from 3.5 to 2.0) and beam building(2.0 to 1.36) when the rock bolt capacities are calculated considering the effect of combined loading as opposed to just the axial or shear loads.

Suspension mechanism and application of sand-suspended slurry for coalmine fire prevention

North and west China has abundant coal resources, however, such resources make these regions prone to serious mine fire disasters. Although the copious sand and fly ash resources found in these areas can be used as fire-fighting materials, conventional grouting is expensive because of water shortage and loess particles. A new compound material(i.e., a sand-suspended colloid), which comprises a mineral inorganic gel and an organic polymer, is developed in the current study to improve the quality of sand injection and reduce water wastage when grouting. The new material can steadily suspend the sand, through the addition of a small amount of colloid yielding steady sand-suspended slurry. The process of producing the slurry is convenient and quick, overcoming the shortage of sand-suspending thickeners which need heat and are difficult to produce. The space work model based on the theory of the double-electric layer is established to study the suspended mechanism of the solid particles in the sand-suspended colloid.The dispersion effect of the sand-suspended colloid is demonstrated by the incorporation of the electrostatic effect by the double-electric layer and the steric hindrance effect on the sand particles, ensuring the stability of the colloid system and the steady suspension of sand particles in the sand-suspended colloid.Mechanical analysis indicates that the sand is suspended steadily under the condition that the rock sand particles stress on the lower part of the fluid is less than the yield stress of the colloid. Finally, the fireprevention technology of sand suspension was applied and tested in the Daliuta Coal Mine, achieving successful results.

Robust Active Suspension Design Subject to Vehicle Inertial Parameter Variations

This paper presents an approach in designing a robust controller for vehicle suspensions considering changes in vehicle inertial properties. A four-degree-of-freedom half-car model with active suspension is studied in this paper, and three main performance requirements are considered. Among these requirements, the ride comfort performance is optimized by minimizing the Ho~ norm of the transfer function from the road disturbance to the sprung mass acceleration, while the road holding performance and the suspension deflection limitation are guaranteed by constraining the generalized H2 （GH2） norms of the transfer functions from the road disturbance to the dynamic tyre load and the suspension deflection to be less than their hard limits, respectively. At the same time, the controller saturation problem is considered by constraining its peak response output to be less than a given limit using the GH2 norm as well. By solving the finite number of linear matrix inequalities （LMIs） with the minimization optimization procedure, the controller gains, which are dependent on the time-varying inertial parameters, can be obtained. Numerical simulations on both frequency and bump responses show that the designed parameter-dependent controller can achieve better active suspension performance compared with the passive suspension in spite of the variations of inertial parameters.

CFD modeling of a headbox with injecting dilution water in a central step diffusion tube

For engineering applications of water dilution controlling system,the fluid dynamics of a mixed flow was studied with computational fluid dynamics(CFD) simulations and self-designed experimental set-up.In order to examine the predictability of CFD model for the headbox in industrial scale,two pulp suspensions before mixing were treated as homogeneous flows separately.Standard k-ε turbulence models with the mass diffusion in turbulent flows-species transport approach were applied in the simulations.A numerical simulation of this headbox model was analyzed with semi-implicit method for pressure linked equations scheme with pressure–velocity coupling.Results show that the model can predict hydrodynamic characteristics of headbox with injecting dilution water in a central diffusion tube,and the distribution of water content at the outlet of the slice lip is ideally normal at different speeds.

Experimental Study on Mechanism and Shape Characteristics of Suspended Flexible Dam

Hydraulic structures such as groin, longitudinal dike and seawall are common in water conservancy and water transportation engineering projects at home and abroad, which have long been dominated by solid mass structural form. With brush and stone as building materials, this kind of structure has an obvious engineering effect. However, it not only requires huge capital investments, but also has negative impacts on the ecological environment. The suspended flexible dam is an innovative engineering measure, and few theoretical and experimental researches of this type dam can be found at present. This paper studies the mechanism and shape characteristics of this dam and obtains the dynamic equilibrium equation of flexible dam, the float buoyancy expression, and the condition for transformation among three forms of the underwater shape of the dam. The results are valuable in engineering application and can be used as the reference for the future work due to the distinctive design philosophy, the small negative effects on environment and the consistency for sustainable development.

Preliminarily modeling of creep effect in electro-dynamic loudspeaker suspensions

The creep effect of suspensions in electro-dynamic loudspeakers was modeled based on fractional order derivatives.The fractional standard linear solid（FSLS） model was presented by substituting the Abel dashpot for Newton dashpot in Standard Linear Solid（SLS） model.The electrical impedance as well as the transfer function between diaphragm displacement and input voltage of the two tested midrange loudspeakers was measured by Klippel laser analyzer system,and the model parameters were identified by the least-mean-square method.By comparing the fitting results of FSLS model with the other two classical models- 4 Parameter Logarithmic model and SLS model,the results show that the FSLS model can rightly predict the frequency dependent compliance loss factor and yield higher accuracy for modeling the creep effect in loudspeaker suspensions.

Prediction of aggregation behavior of submicron-sized particles of praseodymium-doped zirconium silicate in aqueous suspension by population balance model

The aggregation behavior of submicron-sized particles of praseodymium-doped zirconium silicate, a ceramic pigment, in aqueous suspension was predicted by a modified population balance model, In the model, the collision frequencies were selected to describe evolution of the particle size distribution of the suspension. The collision efficiency was estimated as a function of interaction potential between particles based on Derjaguin-Landau-Verwey-Overbeek theory. The population balance model was modified to predict the stable state of the aggregation by introducing the volume mean size of aggregate to stability ratio. In addition, aggregation of the particles in aqueous suspension in the presence of sodium dodecyl benzene sulfonate or potassium chloride was experimentally investigated. The predicted data （i.e., the final aggregate size, aggregation rate, and particle size distribution） were similar to the experimentalresults.