| Currently,although the agricultural machinery equipments are relatively perfect in their functions of labor in the field,they cannot meet the needs of the public in terms of the comfort of the cab.Compared with comfortable cars,the cab of agricultural machinery is uncomfortable mainly because the design of various control devices does not fully follow the theory of ergonomics.For example,there are few studies of the laws of human-machine interaction between the devices such as the seat,steering and the driver.Therefore,this study carried out an optimization test of the agricultural machinery cab on a test platform of adjustable seat,steering wheel,foot pedal and joystick with multi-degree of freedom based on ergonomics theory,aiming to determine the comfort range and optimal combination of the position parameters of the operating device,and explore the mechanism underlying their influence on comfort.The findings can provide certain reference for the analysis,evaluation and optimization of the control device in agricultural machinery cab.The main research contents and results are as follows:?1?Considering that there are certain differences between the China standard GB10000-88“Chinese Adult Human Body Size”and the current Chinese adult body size,this study referred to the second and fourth edition of the international standard ISO 3411“Earth-moving machinery-driver's body size and minimum activity space”,and calculated the annual growth rate in the size of the same body part,which was approximated as the annual growth rate of the size of various parts of human body from 1988 to 2019.Then,GB10000-88“Human Body Size of Chinese Adults”was appropriately revised to obtain the size data closer to that of current Chinese adult human body,providing basic data for the selection of the operator's body shape and the establishment of the 3D model.?2?The four operating devices,including the seat,steering wheel,foot pedal and joystick,all have their own parameters of position.This study adopted evaluation indicators from the perspective of sitting comfort and operating comfort,and used the method of variable coefficient to calculate the weight of each factor and index.At the same time,considering the diversity of evaluation methods,after analyzing the advantages and disadvantages of various evaluation methods and their suitable occasions,we selected the principal component analysis method to reduce the dimensionality of multi-dimensional evaluation indicators.By establishing a comfort evaluation model of the agricultural machinery cab,the comfort analysis and evaluation were carried out on an adjustable test platform of agricultural machinery cab with multi-degree freedom,and the comprehensive comfort score was digitally described in the closed interval[0,1].?3?After the single-factor test of the adjustable test platform was conducted through the evaluation model,based on the response surface second-order regression model,the position parameters of the seat,steering wheel,foot pedal and joystick were designed by BBD?Box-Behnken design?or CCD?central composit design?.Then,the response surface analysis and test optimization were carried out,and the visual evaluation on the influencing law of the control device in the cab on the comfort was completed.Among them,the best combination of position parameter for seat comfort is that the front-back distance and vertical distance from the H point?hip point?to the tread point are 701.26 mm and 431.18 mm,respectively,and the backrest inclination angle is 111.67°;the best combination for steering wheel comfort is that the inclination of the wheel surface is 32.29°,the front-back distance and vertical distance from the W point?wheel center point?to the H point was 400.85 mm and 293.18 mm,respectively;the best combination for the comfort of the foot pedal is that the plane inclination of the pedal is 33.27°,and the left-right distance from the pedal point to the H point is 211.55 mm;the best combination for the joystick comfort is that the front-back distance and left-right distance and the vertical height of the handle ball center relative to the H point are 297.65,350.78 and 11.13mm,respectively.The verification test showed that the average relative errors of seat,steering wheel,foot pedal and joystick comfort were 5.19%,4.18%,3.64%and 3.71%,respectively,indicating strong reliability of the position parameter optimization results.Based on the comprehensive score of comfort in the test and the characteristics of load changes in human-machine interaction,we analyzed the mechanism for the influence of each position parameter on the comfort of the cab control device,and put forward corresponding suggestions for improvement of the comfort.?4?In the orthogonal combination at the position parameter level of the seat,steering wheel,foot pedal and joystick,a 3D human body model was established based on the improved 50thpercentile human body size and imported into the ergonomic module of CATIA software for human body posture simulation analysis and rapid upper limb analysis?RULA?.The results showed a good agreement between the comfort score results of the test and simulation,indicating strong reliability of the optimization results of the position parameters,which provides certain reference for the theoretical research on the comfort of the human-machine system in the agricultural machinery cab.?5?In order to verify the consistency between the subjective comfort evaluation and optimization results,we took five representative agricultural tractors as the research object,and combined multi-level fuzzy comprehensive evaluation and AHP to perform the subjective evaluation.Besides,the previous test results were applied to the objective evaluation experiment,which was carried out using the improved ideal solution method and entropy weight method.The results showed that the ranking results of the subjective and objective comfort evaluation were 1-3-4-5-2 and 1-3-5-4-2,indicating that the subjective and objective evaluation results are highly consistent,and the established evaluation model is reliable,which could enhance the reliability of the verification experiment results to certain extent.Moreover,the subjective and objective evaluation results also provide a new idea for the optimal design of agricultural machinery cab.First,the parameter range of the control device can be determined based on the objective comfort evaluation.Then,the rationality of the parameters can be verified by comparing the results of subjective and objective evaluation,which ensures that the design can meet both the objective comfort theory and the user's subjective comfort,thereby improving the economical efficiency and benefits of the design and manufacture of agricultural machinery products. |
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