ASCS Online Fault Detection and Isolation Based on an Improved MPCA

Multi-way principal component analysis（MPCA）has received considerable attention and been widely used in process monitoring.A traditional MPCA algorithm unfolds multiple batches of historical data into a two-dimensional matrix and cut the matrix along the time axis to form subspaces.However,low efficiency of subspaces and difficult fault isolation are the common disadvantages for the principal component model.This paper presents a new subspace construction method based on kernel density estimation function that can effectively reduce the storage amount of the subspace information.The MPCA model and the knowledge base are built based on the new subspace.Then,fault detection and isolation with the squared prediction error（SPE）statistic and the Hotelling（T2）statistic are also realized in process monitoring.When a fault occurs,fault isolation based on the SPE statistic is achieved by residual contribution analysis of different variables.For fault isolation of subspace based on the T2 statistic,the relationship between the statistic indicator and state variables is constructed,and the constraint conditions are presented to check the validity of fault isolation.Then,to improve the robustness of fault isolation to unexpected disturbances,the statistic method is adopted to set the relation between single subspace and multiple subspaces to increase the corrective rate of fault isolation.Finally fault detection and isolation based on the improved MPCA is used to monitor the automatic shift control system（ASCS）to prove the correctness and effectiveness of the algorithm.The research proposes a new subspace construction method to reduce the required storage capacity and to prove the robustness of the principal component model,and sets the relationship between the state variables and fault detection indicators for fault isolation.

Asymptotic Analysis Soot Model and Experiment for a Directed Injection Engine

The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many researchers within the error range in the current computer speed. On the basis of the latest experimental results, TP （temperature phases） model is presented as a new soot model to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature and excess air factor are the most important two parameters in this model. When zone temperature T〈 1 500 K and excess air factor Ф〉0.6, only the soot precursors-- polycyclic aromatic hydrocarbons（PAH） is created and there is no soot emission. When zone temperature T ≥ 1 500 K and excess air factor Ф〈0.6, PAHs and soot source terms （particle inception, surface growth, oxidation, coagulation） are calculated. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. KIVA standard model and experimental data are analyzed for the results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP models. The experimental results indicate that the TP model can carry out optimization and computational fluid dynamics can be a tool to calculate for a high-pressure common rail directed injection diesel engine. The TP model result is closer than the use of the original KIVA-3V results of soot model accuracy by about 50% and TP model gives a new method for engine researchers.

Design of hydraulic shift mechanism for AMT vehicles based on the collaborative optimization method

Based on multidisciplinary design optimization（MDO）,a new design method is put forward for hydraulic shift mechanism of heavy-duty vehicle automated manual transmission（AMT）.Taking a shift cylinder for example,the collaborative optimization（CO）method for the design problem of a cylinder is devided into one system level design optimization problem and three subsystem level design optimization problems.The system level is an economic model and the subsystem level is mechanics,kinetics,and a reliability model.Application of the multidisciplinary design optimization software iSIGHT modeling and solving,optimal solution of the shifting cylinder CO model is obtained.According to the optimal solution,oil cylinders are machined out and installed on the gearbox of an AMT system for the bench cycle shift test.The results show that the output force and action speed of the optimized mechanism can meet requirements very well.In addition,the optimized mechanism has a better performance compared to the structure of the traditional design method,which indicates that the CO method can optimize the design of hydraulic transmission.

Uphillshift decision strategy of an AMT off-road vehicle based on generalized road resistance coefficient

In order to improve the shift decision strategy for an off-road vehicle with automated manual transmission（AMT）,the generalized road resistance coefficient is defined based on the longitudinal dynamics analysis.Vehicle mass and generalized road resistance coefficient are estimated using the recursive least square（RLS）method with multiple forgetting factors.The improved shift schedule is designed based on the generalized road resistance coefficient under uphill road condition.The simulation and real vehicle test verify the effectiveness of improved shift strategy and the improvement of vehicle dynamic performance.

Numerical analysis on three dimensional temperature field of the gap between piston and cylinder

The three dimensional temperature field of the gap between piston and cylinder was ob- tained by numerically solving energy equation. The boundary condition of the equation was given in the form of heat transfer coefficient, instead of solving the temperature field of solid parts. The tem- perature field was calculated both under high speed high pressure condition and low speed low pres- sure condition. The numerical result was compared to experimental result under low speed low pres- sure condition and showed good agreement. It was shown that the influence of heat transfer coeffi- cient on t＇tim temperature was significant. The adiabatic condition was reasonable under low speed low pressure condition, but invalid under high speed high pressure condition. It was a good way to describe the influence of solid parts on temperature using heat transfer coefficient but avoiding sol- ving the temperature field of solids parts.

Analysis on the gear-shifting schedule of hydraulic automatic transmission

With an advanced foreign hydraulic automatic transmission as the objective,an analytical method for the gear-shifting schedule is proposed.First the demanded maximum gradient of test is estimated.Then a test scheme and analytical procedure is formulated by initial test and hypothetical shift parameters.Finally through gear-shifting tests under different road conditions,load,accelerator pedal position limitation,throttle opening and output shaft speed are found to be the gear-shifting parameters.Under a common road condition,the gear-shifting schedule is a double-parameter schedule.Based on the driver＇s demands on braking and dynamic performance,different shift schedules are made under downhill,uphill and quick releasing acceleration pedal conditions.The operation criteria of down-shift schedule on abrupt grade are proposed.

Determination of Slip Length in Couette Flow Based on an Analytical Simulation Incorporating Surface Interaction

An analytical simulation based on a new model incorporating surface interaction is conducted to study the slip phenomenon in the Couette flow at different scales. The velocity profile is calculated by taking account of the micro-force between molecules and macro-force from the viscous shearing effect, as they contribute to the achieve- ment of the slip length. The calculated results are compared with those obtained from the molecular dynamics simulation, showing an excellent agreement. Further, the effect of the shear rate on the slip is investigated. The results can well predict the fluid flow behaviors on a solid substrate, but has to be proved by experiment.

Numerical film torque modeling of friction pair in hydro-viscous clutchs

A numerical model to predict film torque of hydro-viscous clutch was developed.The model was established with computational fluid dynamics（CFD）.The pressure distribution,velocity of flow and film torque were obtained based on vertical-horizontal grooved plate and radial grooved plate separately.The boundary conditions,such as the relative rotation,the fluid temperature and the oil feeding pressure,were also discussed.The results showed that the film torque of two kinds of grooved plate increased with increasing relative rotation.However,the film torque decreased with increasing fluid temperature and feeding pressure.Meanwhile,the film torque of radial grooved plate was less than vertical-horizontal grooved plate at the same condition.Our study showed that the model can efficiently calculate the film torque with complex geometry parameters and boundary conditions.

Fault diagnosis of AMT gear shifting process based on semi-quantitative SDG model

In order to diagnose gear shifting process in automated manual transmission（AMT）,a semi-quantitative signed directed graph（SDG）model is applied.Mathematical models are built by analysis of the power train dynamic and the gear shifting control process.The SDG model is built based on related priori knowledge.By calculating the fuzzy membership degree of each compatible passway and its possible fault source,we get the possibilities of failure for each possible fault source.We begin with the nodes with the maximum possibility of failure in order to find the failed part.The diagnosis example shows that it is feasible to use the semi-quantitative SDG model for fault diagnosis of the gear shifting process in AMT.

Self-adaptive correction of clutch control with proportional valve

A new method for self-adaptive correction of the clutch proportional valve by Lyapunov stability function is proposed. Compared with displacement curve of hydraulic control cylinder under standard load, pulse width modulation （PWM） voltage imposed on clutch proportional valve is cor- rected according to the error to improve the consistency of the clutch control system in the process of clutch engagement. Computer simulations are conducted with this self-adaptive correction method by establishing the clutch control system model and results indicate that the principle of the method is correct. The flow rate variation obtains effective restraint which is caused by clutch control system characteristic of different vehicle under constant PWM voltage.

Shifting force control of an AMT heavy-duty truck based on manual shift test

Taking a heavy-duty truck as a research platform,the changing characteristics of shifting force,shift time,and slipping work are obtained through theoretical analysis and manual shift test of a real vehicle. Based on the analysis of the test results,a gear-shifting control strategy of the hydraulic automated shift control system is designed and experimentally verified on the bench. By optimizing the control parameters of high-speed switching valves,a control strategy and parameters are obtained,which can meet the requirements of dynamic performance and reliability.

Multi-parameter load sensing pump model simulation and flow rate characteristics research

Load sensing pumps have been widely used in diverse hydraulic systems.Studies show that structural parameters have undeniable impacts on the characteristics and efficiency of the load sensing pump.The main purpose of this article is to study the influence of load sensing pump structure parameters on flow characteristics.In the present study,a nonlinear multi-parameter model is proposed for this type of pump.In this model,different parameters,including spool clearance,spool covering amount,internal leakage are considered to reflect the displacement adjustment process of the load sensing pump.Moreover,a frequency sweep method is proposed to analyze the frequency domain of the nonlinear mathematical model.An experiment rig was built to study the influence of key structural parameters on the dynamic follow-up characteristics of the pump flow.The obtained results show that the diameter of the orifice d can significantly affect the working characteristics of the pump.It is found that a large diameter of the orifice d can improve the phase following ability of the system,while a small diameter of the orifice d can reduce the bypass flow rate and increase the amplitude following ability.This paper provides a new consideration to study the dynamic follow-up characteristics of the load sensing pump.

Controllable synthesis and surface modification of molybdenum oxide nanowires: a short review

Transition metal oxides are found to have overwhelming applications in energy,electronics,catalytic,and bio-and micromechanical systems.A recent report emphasized the current advancements in molybdenum oxide(MoO_(x))nanowire synthesis and the corresponding surface-functionalized nanostructured materials based on our previously reported investigations.The preparation of the nanowires and their applications were systematically summarized.MoO_(x) nanowires combined with substrates exhibited remarkable performances for high energy storage and power densities with high stability.In addition,the review concluded the future advancements of MoO_(x) nanowires.

Numerical simulation and scaling analysis of elasticity-induced lift force in a viscoelastic fluid between confining surfaces

How to accurately characterize the lift force on the particles near the solid surfaces is an ongoing challenge in fluid mechanics and microfluidic techniques, especially in a complex system with viscoelastic fluid or/and soft surface that is commonly encountered in a biological system. The motions of the particles in vicinity of a surface can be simplified to be a rigid cylinder surrounded by the viscoelastic fluid moving along a substrate which can be rigid or soft according to different cases. In such an inertial free system with a wide range of Weissenberg number (Wi < 5.00, representing the ratio of the elastic force to the viscous force), firstly we numerically evaluate the influence of the systematic parameters, including the polymer viscosity, the geometry and Wi, on the net normal force for a cylinder closely moving along a rigid substrate, and the elasticity-induced lift force in a scaled form. It is shown that a strong shear arises in the viscoelastic confinement between the moving cylinder and the rigid substrate, it leads to the asymmetry of the first normal stress distribution around the cylinder, and thus the lift force. Then, the influence of a soft substrate on the lift force is considered, and we find that the lift force induced by the viscoelastic fluid always dominates in magnitude over that induced by the soft substrate deformation. This work provides a reliable scaling that can be utilized to quantify the elasticity-induced lift force on the particles in a viscoelastic system, such as the micro- and nanofluidic systems in biological applications.

Gear fault diagnosis using gear meshing stiffness identified by gearbox housing vibration signals

Gearbox fault diagnosis based on vibration sensing has drawn much attention for a long time.For highly integrated complicated mechanical systems,the intercoupling of structure transfer paths results in a great reduction or even change of signal characteristics during the process of original vibration transmission.Therefore,using gearbox housing vibration signal to identify gear meshing excitation signal is of great significance to eliminate the influence of structure transfer paths,but accompanied by huge scientific challenges.This paper establishes an analytical mathematical description of the whole transfer process from gear meshing excitation to housing vibration.The gear meshing stiffness(GMS)identification approach is proposed by using housing vibration signals for two stages of inversion based on the mathematical description.Specifically,the linear system equations of transfer path analysis are first inverted to identify the bearing dynamic forces.Then the dynamic differential equations are inverted to identify the GMS.Numerical simulation and experimental results demonstrate the proposed method can realize gear fault diagnosis better than the original housing vibration signal and has the potential to be generalized to other speeds and loads.Some interesting properties are discovered in the identified GMS spectra,and the results also validate the rationality of using meshing stiffness to describe the actual gear meshing process.The identified GMS has a clear physical meaning and is thus very useful for fault diagnosis of the complicated equipment.