Dynamic Analysis And Optimization Of The Virtual Prototyping Model Of Stretcher Bed On Ambulance Based On The Combination Of Pro/E And ADAMS

Comfort is a very important standard to an ambulance as its main function is to deliver the patients. It requires that the vibration and impact from the road should be reduced as much as possible in operation. The patients will feel comfortable and steady while they are ensured to be delivered safely and quickly, and the vibration will not increase the patients' pain or make the wound worse. In order to improve radically the comfortable delivery, special chassis should be used to the ambulance. But nowadays, the ambulances are mostly refitted from the cars' chassis of typeⅡorⅢ. The main measure to improve the comfort is the reasonable design of the stretcher bed to reduce the vibration. Therefore, this research is founded on the virtual prototyping model of stretcher bed on ambulance and uses the principle of random sine wave superposition to change the PSD of pavement roughness to displacement in time-domain and Visual Basic language to program it. The program can create files of pavement roughness of all levels according with GB7031-86 in different ride speed. The files are used as stimulation on the model for simulation and analysis of dynamics. The parameters of absorber in stretcher bed are optimized, and thereby, the comfort is effectively improved. Main work and conclusions of the study are as followed:1. Professional CAD software Pro/E was used to build the three-dimensional solid model. The whole model was assembled by more than 300 parts (not including standard parts and parts used several times). It solved the problem that the dynamic analysis software was not good at building complex model.2. The interface between Pro/E and ADAMS was managed well with Mech/Pro. Firstly, the key of interface in the study was to define rigid bodies. That is to define those parts that hadn't movement with each other as a rigid body in the system. Secondly, the key consisted in precisely picking up and transferring the information of parts. It's important to solve the distortion of the model transferred to ADAMS. The virtual prototyping model built in the study was easy to manipulate, and the parameters could be changed conveniently to meet the requirements.3. A time-domain pavement roughness creating software was programmed. The key of programming was application of the principle of random sine wave superposition to educe the formula transferring the PSD of pavement roughness to the displacement in time-domain. That is the most difficult in the study. The software can be used in any research referring to vibration in "pavement-car" system.4. The curve of vertical acceleration in time and frequency domain and the RMS of vertical acceleration without absorber were obtained. Conclusion can be drawn by comparing the curve and data: Vibration intensity was enhanced with the increase of speed and the deterioration of road surface. Vibration intensity at abdomen was greater than that at head with low or medium speed, while the former was less than the latter with high speed. The inherent frequency of the system was 2.7 Hz. This experiment confirmed the dynamic characteristic and movement status of the stretcher bed, and it was the experimental base of optimizing the stretcher bed.5. The stretcher bed was optimized for the goal of minimizing the average of the square of vertical acceleration under the circumstances of secondary road and 50 Km h ride speed. When the stiffness coefficient of the spring-damper was 30 N mm, and the damping coefficient was 5.9 N ? smm, the RMS of vertical acceleration turned to 5001 mm s2 from 5344 mm s2, and the vibration intensity reduced obviously. The capability of vibration reduction was remarkably improved. This experiment could be used as a reference in choosing parameters of vibration reduction system to some extent.