Best compromising crashworthiness design of automotive S-rail using TOPSIS and modified NSGAⅡ

In order to reduce both the weight of vehicles and the damage of occupants in a crash event simultaneously, it is necessary to perform a multi-objective optimal design of the automotive energy absorbing components. Modified non-dominated sorting genetic algorithm II(NSGA II) was used for multi-objective optimization of automotive S-rail considering absorbed energy(E), peak crushing force(Fmax) and mass of the structure(W) as three conflicting objective functions. In the multi-objective optimization problem(MOP), E and Fmax are defined by polynomial models extracted using the software GEvo M based on train and test data obtained from numerical simulation of quasi-static crushing of the S-rail using ABAQUS. Finally, the nearest to ideal point(NIP)method and technique for ordering preferences by similarity to ideal solution(TOPSIS) method are used to find the some trade-off optimum design points from all non-dominated optimum design points represented by the Pareto fronts. Results represent that the optimum design point obtained from TOPSIS method exhibits better trade-off in comparison with that of optimum design point obtained from NIP method.

Pressure performance improvement by dual-mode control in digital pump/motor

Due to the advantages of low cost,fast response and pollution resistance,digital hydraulic pump/motor can replace conventional variable hydraulic pump/motor in many application fields.However,digital hydraulic components produce large hydraulic impact at variable moments,which will shorten the service life of mechanical components.Through the simulation analysis of the variable process of digital pump/motor,it is found that the discontinuous flow caused by displacement step changes is the fundamental cause of hydraulic impact.The data analysis results of experimental tests are in good agreement with the simulation analysis results.In view of hydraulic secondary components,a variable control method based on dual-mode operating characteristics is proposed.The TOPSIS algorithm is used to give comprehensive evaluation of the displacement control results after this method.The results show that the control quality of digital pump/motor after adopting the control method has been effectively improved,with an average improvement of about 40%.