Design And Experiment Of All-Wheel Transmission System Based On Belt Drive

Boat-tractor is a unique power equipment in our country which adopts floating principle.With small resistance in the field operation,it is particularly suitable for the complex and changeable natural environment in the south of China,making it popular in the southern rice producing disttict.At present,the walking system of boat tractor mainly adopts the form of single bridge and two wheels.Following problems exist for them.(1)The supporting power for the transmission system is small and the mechanical efficiency is low.(2)The ability of overcoming field obstacles such as field shifts,overpasses,and uphill and downhill slopes is not satisfying.(3)Using unilateral braking to achieve differential pivot steering,it is easy to form mounds and mud pits in the field.(4)Some types of machine equips no gear shifting device,so that the mobility is poor and the most suitble operating speed can not be selected,letting alone the reverse condition.On the basis of understanding and analyzing the current research status of foreign wheeled sliding steering vehicles and domestic boat tractors,aiming at the problems of low transmission efficiency and poor mobility of traditional two-wheel drive boat tractors and taking the drive system of the four-wheel drive boat tractor as the research object,the theoretical analysis and steering model establishment of the four-wheel drive ship-type tractor is established in this paper.The design,simulation and experimental research of the transmission system of the four-wheel drive boat tractor are carried out.The specific research contents and conclusions are as follows:(1)The establishment of steering theory and steering model for four-wheel-drive boat-tractors.A theoretical analysis and mathematical model establishment of four-wheel-drive boat tractor steering is carried out.Based on the theoretical analysis of kinematics and dynamics of four-wheel-drive boat tractor's large radius steering and small radius steering,a mathematical model of steering is established.Considering comprehensively,the steering resistance moment of vehicle is greater and the steering is more difficult when turning small radius steering.(2)The design of four-wheel-drive boat-tractor transmission system.Aiming at realizing the pivot steering function,symmetrical transmission system which combines synchronous belt and driving wheel is adopted to realize the front axle and rear axle wheel drive linkage.The machine adopts the dynamic unilateral separation of the frontaxle controlled by the steering machine and the hydraulic braking of the rear axle differential case,so as to achieve the pivot steering of the complete machine.(3)Simulation and analysis of the transmission system of a boat-tractor.A simplified3 D model of front axle,rear axle and car body of boat tractor drive system is established by using SolidWorks software The created model is imported into ADAMS.After adding constraints between tires,road files and components,defining the boundary conditions,dynamic simulation is performed.The simulation test results show that the transmission system has good synchronization,high transmission efficiency and small offset in the direction of Y,which is in line with the principle of straight line walking.When the machine is pivot steering,the steering angle speed of the vehicle body and the body steering efficiency increase with the gear level increasing.The stability of the machine in pivot steering iscomparing with the cutting edge steering.When high perfoming speed steering or deviation needed to rectify the direction,the cutting steering mode is used instead of the original steering mode.(4)Research on steering performance of the boat tractor.The steering performance and evaluation index of the boat tractor were determined.And the linear performance test,minimum steering radius test and steering angle speed test of the boat tractor under different gear positions were carried out in the working environment of the cement road surface.Comparing the data obtained on cement road and ADAMS,the test results show that the steering angular velocity under the Adams environment is 100%-118% of the cement pavement experiment value,and the simulation result of the minimum steering radius is 86%-96% of the test numerical value,which shows that the dynamic simulation model is feasible.The average value of the minimum steering radius is 0.022 m in the test,which can meet the requirement of small ground turning,possessing small steering area.The steering angle speed of the car body is 0.24rad/s and 0.26rad/s respectively when the gear is 1 gear and the reverse gear.When the gear position is 2nd gear,the body steering angle speed is 0.45rad/s.When the gear position is 3rd gear,the body rotation angle speed is 0.65rad/s.Different gear positions provide different steering angle speeds,which can meet the different requirements of the operation and meet the complexity requirements of field work.However,it is proposed that the pivot steering is more suitable under the slow speed condition,and the use of the original place should be avoided when the high speed emergency steering or the direction correction is needed.(5)The test of the boat-tractor steering wheel angle.The results show that during steering processs,the rotational speed of the input shaft of the outer drive wheel remainsbasically unchanged,and the input shaft speed of the inner drive wheel continuously decreases.The rotation speed of the output shaft of the inner drive wheel will have a negative value until the input shaft speeds of the drive wheels on the inner and outer sides are equal and opposite to each other.In the test process of gears 1st,2nd,3rd,and reverse gears,four-wheel drive ship tractor driving wheels on both sides of the input shaft speed have the same change trend,and turning radius value will eventually tends to zero,which means that the machine can eventually realise pivot steering whatever the gear level the vehicle starts to turn.(6)Research on field adaptability of boat-tractors.The test results show that the working environment has a great influence on the pivot steering radius.The pivot steering radius under the paddy ground working environment is approximately 9.8 times the pivot steering radius under a solid ground working environment.Under different working conditions,the steering angle speed of the prototype has not changed much,and the turning angle speed of the prototype under the paddy field is relatively small,which means that the paddy field steering is more difficult than other working environments.The minimum steering radius of the cement floor is 8%-10% of the experimental value of the minimum turning radius of the paddy field surface.The angle velocity of the cement ground steering angle is 77%-95% of the test value of the field steering angle velocity in the paddy field,which indicates that the pivot steering in the paddy field working environment is more difficult than the cement floor working environment.But the turning radius is smaller and the steering angle speed is larger than the traditional steering mode.