| The roadway repairing machine is specially used for underground coal mining and tunnel repairing,because of its compact structure,high efficiency,strong adaptability and high security,it has been widely used in coal mining industry.Due to the limitation of underground space environment,the backhoe working arm is required to meet the certain loading height under the limited height,while the conventional working arm cannot meet the requirements.In order to solve these problems,this paper first studies the adaptability of two arm and three arm to the limited space,and then optimizes the mechanism and makes a analysis,so as to choose a more suitable design scheme,and obtains that the three arm is more suitable for the special underground environment.On the premise of ensuring the strength and rigidity of the structure,the combination of size optimization and topology optimization are used to reduce the mass of the structure as much as possible.The main research contents and results are summarized as follows:(1)The objective function and constraint expression of two and three arms are derived.The kinematic models of two arm backhoe and three arm backhoe are established by using the D-H homogeneous transformation matrix method,and the kinematic analysis of them is carried out,so as to obtain the position relationship between the hinge points,and the expression of boundary constraint is derived;At the same time,the maximum theoretical digging force of two arm backhoe working device and three arm backhoe working device is deduced,and the objective function expression with nonlinear and multivariable points is derived.(2)The structure adaptability of backhoe working device was studied.The geometric relationship between the structure of two arm and three arm and the height of the roadway is established;then the expression of objective function and constraint conditions of the backhoe working device based on the excavation force are established,and the optimization mathematical model of the backhoe working device mechanism is established.The adaptability of two arm backhoe and three arm backhoe are studied.When the roadway height is more than 2.5m,the two arm is broken in the range of i?0.59,three arm is broken in the range of i?0.69.The three arm has a wider adaptive range than the two arm.(3)The key factors influencing the optimization results are analyzed.The influencing factors of the mechanism optimization of the three arm backhoe working device are analyzed,and the key constraint conditions that affect the three armbackhoe working device is obtained.The research shows that the unloading height and the roadway height have a significant impact on the optimization results of the three arm backhoe working device.The roadway height is higher and the unloading height is lower,the digging force of the three arm backhoe working device is greater.It shows that after optimization,the boom length decreases by 8.9%,the intermediate arm increases by 47.9%,the arm decreases by 18.7% and the digging force increases by9.4%.(4)The structure optimization of three arm backhoe working device is completed.On the basis of mechanism optimization,the size optimization and topology optimization of the optimized three arm backhoe working device are carried out,the mathematical models of size optimization and topology optimization are derived.On the premise of meeting the requirements of strength,the structural optimization of three arms is completed.After optimization,the mass of boom is reduced by 16.93%,the mass of intermediate arm is reduced by 19.74%,the mass of arm is reduced by 17.87%,the overall mass is reduced by 17.97% and the stress is improved. |
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