Research On Mechanism Design And Analysis For Robotization Of Coal Road Driving Equipment For Soft And Outburst Coal Seam

Underground mining is the main method of domestic coal production; therefore a large number of roadways are necessary. With the rapid development of fully mechanized coal mining technology the fast tunneling technology in coal should be improved to meet the production requirements. At those mines with better geological condition of coal seam, the effective comprehensive mechanization tunneling technology has been applying and spreading, and is developing toward automation and robotization. However, the coal road driving speed in three soft and outburst coal has not been improved efficiently so far. The direct reason for this is due to the great time consumption of the outburst prevention measures and tunnel bracing process, while the root cause is that the equipments can not comprehensively adapt to the complex press measures of the coal road driving. Hence, pertinently research and develop advanced equipment is necessary. Heading equipment robotization has become consensus in the coal industry, and may be the best way to conquer the problem of coal road heading in soft and outburst seam, hence related researches should be developed actively.In this dissertation, based on the typical soft and outburst seam coal road heading process of some mines, the common characteristics of the present equipment technology for gas release, proof bolting, and boring cutting are studied, the idea and mechanism design thinking of multi function robotization of heading equipment are put forward. The key principles of robotization mechanism design are verified by means of a modified light roadheader, and researches on some main issues of the mechanism design and analysis are also made in hope to make theoretical reference to the further research of the robotized roadheader for soft and outburst coal seam. The main contents are as follows:(1) In soft and outburst coal seam, the outburst prevention measures, boring cutting, and tunnel bracing measures are very complex and multiple equipments involved, so that most time is spent on ancillary work and the drivage efficiency is very poor. In view of this, the idea of shifting the tools corresponding to different jobs to realize multifunctional robotization of heading equipment is proposed. The characteristics of equipment demand of coal road tunneling process are analyzed, the functions and kinematics similarities of different equipments are studied, and then the feasibility of tunneling equipment robotization is demonstrated. Taking full account of the characteristics of the operating objects, the operating environments, and the tasks, the functional goals of the robotized roadheader are properly determined; the mechanism design scheme is put forward and the key principles are verified by means of prototype. The limits from structure and types of wrist to multiple operations of the robotized roadheader are studied, by which the mechanism design is improved. The robotized roadheader combines the cutting function, the drilling functions of all kinds of drill, and other auxiliary functions in one, so that the tunneling process become more mechanized and the drivage efficiency can be effectively promoted.(2) Research on the design of joint driving force is made. The Load force and torque on robotized roadheader are complicated, and cutting path varies dramatically; therefore the most unfavorable conditions can not be obtained by conventional methods. A joint force analysis method based on reverse modeling of wrist kinematic chain is presented to solve the problem. The cutting head is supposed to be unmovable, conversely, variations of two angular parameters are used to express all possible orientation of the wrist, an other angular parameter is used to express all possible working path. By this way, operation status under all possible cutting paths can be simply expressed by only three angular parameters; therefore the complicated working load is simplified effectively. By establishing the force system balance equation of the whole wrist and solving it, the driving force system of the cutting arm at the wrist point is obtained, and then the driving force (torque) of each joint can be obtained. The maxium driving force (torque) of each joint and the best working mode are obtained by driving force analysis. The method and the results can provide theoretical guidance for the design of joint driver and selection of cutting path.(3) The robotized roadheader has5DOFs; however, it can be seen as essentially a6-DOF serial robot manipulator with offset wrist without practical closed-form inverse kinematics solution. Research on the inverse kinematics algorithm for this type of manipulator is made, and a numerical algorithm based on offset compensation is proposed according to the geometric characters of the offset wrist to solve the inverse kinematics problem. Based on the reference end orientation of corresponding spherical wrist manipulator, by compensatorily translating and iteratively correcting its wrist position in proper direction, the numerical solutions for the manipulators with offset wrist can be obtained. The one advantage of the algorithm is that it does not affect the end orientation; the orther is that the program is versatile to manipulators with same type offset wrist. A large number of tests confirmed the good real-time performance of the algorithm.(4) In order to ensure that robotized roadheader could perform various tasks in the roadway, its workspace problem is studied. The defects of poor random point distribution on boundary and low calculation precision of the Monte Caro method is analyzed, and a kind of orientational distribution algorism is presented. Based on the continuity of the mapping from joint space to workspace, new random points are generated around the searched boundary points targeted to improve the boundary point distribution, and sub stratification method is also used to reduce the error caused by the slice thickness, hence more precise boundary points may be extracted from the newly generated. The new algorithm could significantly improve the calculation precision of workspace boundary and promote the computational efficiency. Operating characteristics of typical tools are also analyzed, and design requirements for standard tools are proposed so that the workspace could be generalized.(5) Robotized roadheader has to accomplish several different operations; therefore its dexterity is important. Research on this subject is made to assess the performance of it. In order to solve the unit inconsistency problem in the conventional Jacobian matrix, a simple but effective method based on variable weighting matrix to normalize the Jacobian matrix is presented. According to the essence of robot dexterity, general ideas and methods for normalizing the Jacobian matrix are put forward, and the variable weighting matrix is defined. The variable weighting matrix is deduced just from the Jacobian matrix, therefore the disvantages of introducing additional parameters of the traditional methods are avoided. The validity of the variable weighting matrix is illustrated by theoretical deduction and numerical simulations. By means of the variable weighting matrix, the dexterity of the robotized roadheader is analyzed, and the singularity discriminant is presented. Analysis of the relationships between the dexterity and the link parameters provided the design basis for the geometric parameters determination.