Research On Optimal Design Of Vibration Isolation System Of Ambulance With X-type Hydraulically Interconnected Suspension

The ambulance is an important tool for transporting patients and providing first aid.It is an crucial part of the health care support system.The patients,paramedics and medical instruments carried by the ambulance have high vibration performance requirements.However,in order to send patient to the destination quickly,ambulance is often in driving conditions of rapid start,emergency stop,rapid turn,and frequent changes in vehicle speed,which deteriorates the riding comfort and driving stability of the ambulance.This paper takes the ambulance vibration isolation system as the research object,with the purpose of improving the patient’s riding comfort and the comprehensive performance of the ambulance.The following research works are carried out in this article:(1)It is proposed that combining the X-type hydraulically interconnected suspension(XHIS)system with the stretcher vibration isolation system to improve the comprehensive performance of the ambulance and the comfort for patient.A 13-degree-of-freedom machine-liquid coupling dynamics model include ambulance vehicle,stretcher,and human body was established in frequency domain and time domain.and the model was verified through experiments.(2)The dynamic simulation analysis in frequency and time domains of ambulances was carried out.Compared with traditional suspensions,the bounce,pitch,and roll modal frequencies of the ambulance equipped with XHIS system are reduced by 13.2%,improved by 4.2% and 9.24%,respectively.And the XHIS system can the damping ratio is significantly improved to decay the vibration of the ambulance effectively,and reduce vibration transmission at low frequency part.The ride comfort,Anti-pitch,and anti-roll performance of the ambulance improved.However,the time-domain response shows that the comfort of the patient has not been significantly improved.It is necessary to optimize the ambulance vibration isolation system parameters according to the driving characteristics and performance requirements of the ambulance.(3)Based on the Sobol global sensitivity analysis method,the parameter sensitivity is performed of the vibration isolation system of the ambulance.The first-order sensitivity and global sensitivity index of each parameter to each performance index are obtained,and the parameters that have an important impact on the performance of the ambulance can be identified.At the same time,the comprehensive sensitivity analysis was carried out,and the result shows that the parameters of the stretcher suspension system have little effect on the performance of the ambulance vehicle,while the parameters of the XHIS system have a certain effect on the performance of the stretcher.(4)A step-by-step multi-objective optimization(MOO)scheme is proposed,and the parameters of the ambulance vibration isolation system are optimized to further improve the patient’s riding comfort and the overall performance of the ambulance.Compared with the traditional suspension,the overall vibration value of the body after step-by-step MOO is reduced by 11.8%,and the pitch angle acceleration of the stretcher is reduced by 19.38%.The comfort of the patient is significantly improved.Compared with the traditional MOO scheme,the Pareto solution set of the step-by-step MOO scheme has a higher degree of aggregation and continuity,providing designers with more selectivity.And the results obtained by the step-by-step MOO scheme make the overall performance of the ambulance improved,significantly.This article adopts the form of combining XHIS and stretcher vibration isolation system to improve the ambulance performance.Through the sensitivity analysis and multi-step MOO of the ambulance vibration isolation system,the patient’s comfort and the comprehensive performance of the ambulance are improved significantly.This paper proposes a feasible solution for improving the comfort of the ambulance and the comprehensive performance of the ambulance.It has a strong practical application value and is of great significance to avoid the deterioration of the patient’s condition due to uncomfortable vibrations during the transportation.