Optimal gear shift control strategy for positive independent mechanical split path transmission with automatic shift system

An improvement strategy which controls the shift effort and the power summing planetary gear set of steering clutches and brakes have been proposed based on the dynamic model of synchroniser in order to decrease the wear of synchroniser inserts, make gear shift easy and reduce the shock noise for a positive independent mechanical split path transmission which attached an auto- matic shift system when shifting. A kinetics model for the process of synchroniser engagement is built and analyzed in the paper. Thus for optimizing the gear shift process which is divided into three phases a model reference fuzzy self-adaption system is adopted. Through a 6 000 km road experiment, the control strategy has proved feasible and dependable.

RELIABILITY-BASED ANALYSIS AND SYNTHESIS OF MECHANICAL ERROR FOR PATH GENERATING LINKAGES

A reliability-based analysis approach to mechanical error in path generating linkages is pre- sented . The reliability index is taken as a measure for the deviation of the actual path of a coupler point from the desired one. A reliability-based synthesis procedure of the mechanical error for path generating linkages to allocate optimal tolerances and clearances is developed. A four-bar path generating mechanism is considered for numerical illustration.

Single boron atom anchored on graphitic carbon nitride nanosheet(B/g-C_(2)N)as a photocatalyst for nitrogen fixation:A first-principles study

It is essential to explore high efficient catalysts for nitrogen reduction in ammonia production.Based on the first-principles calculation,we find that B/g-C_(2)N can serve as high performance photocatalyst in N_(2)fixation,where single boron atom is anchored on the g-C_(2)N to form B/g-C_(2)N.With the introduction of B atom to g-C_(2)N,the energy gap reduces from 2.45 eV to 1.21 eV and shows strong absorption in the visible light region.In addition,N_(2)can be efficiently reduced on B/g-C_(2)N through the enzymatic mechanism with low onset potential of 0.07 V and rate-determining barrier of 0.50 eV.The"acceptance-donation"interaction between B/g-C_(2)N and N_(2)plays a key role to active N_(2),and the BN_(2)moiety of B/g-C_(2)N acts as active and transportation center.The activity originates from the strong interaction between 1π1π*orbitals of N_(2)and molecular orbitals of B/g-C_(2)N,the ionization of 1πorbital and the filling of 1π*orbital can increase the N≡N bond length greatly,making the activation of N_(2).Overall,this work demonstrates that B/g-C_(2)N is a promising photocatalyst for N_(2)fixation.

Effects of Cooling Paths on Through-Thickness Microstructure and Mechanical Properties of Heavy Gauge X80 Pipeline Steel

The effects of various cooling paths on uniformity of through-thickness microstructure and mechanical properties of X80 pipeline steel of 22.0 mm in thickness were studied. The finite difference method was employed to calculate the temperature field during cooling. It was confirmed by the experimental result and temperature field calculation that the optimizing process was achieved by the ultra-fast cooling with medium cooling capacity（cooling rate of ＊23 K/s）followed by ultimate cooling capacity（cooling rate of ＊50 K/s）. After optimization, the experimental steel displayed much uniform microstructure and the deviation of through-thickness hardness was controlled within 20 HV. In addition,the yield strength, tensile strength and elongation of the experimental steel were 621, 728 MPa and 21.5%, respectively,meeting the requirements of the API standard for X80 pipeline steels.

Investigations on MBSE modelling and dynamic performance assessment of an electrical trimmable horizontal stabilizer actuator

With the development of power-by-wire technology for more electric aircraft,the electromechanical actuator(EMA)has the advantages to replace the conventional hydraulic servo actuator in some aerospace flight controls.Conventional hydraulically powered trimmable horizontal stabilizer actuation(THSA)system is nowadays developed to be electrically supplied.Given their safety-criticality,no-back mechanism and redundant load paths are utilized to meet the flight control requirements.However,rare literatures have introduced these functions and addressed the virtual prototyping activities from system-level point of view.This paper proposed such a model of a THSA system with dual electric power sources and fault-tolerant mechanical load paths.The nonlinear effects of components are considered with realism,and system-level simulation test is conducted to support the model-based system engineering(MBSE)approach.The models are developed with a power view instead of a pure signal view.Focusing on the friction effect and compliance effect with backlash or preload,some improved and novel approaches are adopted for these crucial components and validated via experimental results.Meanwhile,the implemented systemlevel model enables injection of crucial faults.Finally,the simulation of the proposed model shows that it is an efficient resource to investigate the actuator’s dynamic performance,to virtually prove that the actuator meets the fail/safe constraint,and to demonstrate the soundness of the fault monitoring functions.