| With the increasing of labor cost,the demand for automation and intelligent products continues to expand.Robots are becoming progressively popular in many enterprises.As one of the most important types of robot in industrial enterprises,assembly robots are being increasingly wide used in the production process;meanwhile,the design and development is becoming more and more mature.However,under the influence of assembling accuracy,price and degree of intelligence,assembly robots are difficult to be accepted by the public enterprises,many assembly workshops still rely on manual work to assemble.Motion control system is crucial to an assembly robot in completing complicated assembling technology.This paper takes the visual positioning assembly robot as the research object,practicality as the idea,control precision as the core,and realizes the precision assembly process as the ultimate goal,to develop an economical,practical and intelligent motion control system.In the condition of the position of the workpiece and the mounting point are random,which can control the assembly robot completes the automated assembly process with high accuracy and efficiency.(1)By detailed analysis of the assembly process,the functions of the motion control system for the assembly robot are known.And based on this,finish the selection of main hardware.Finally,combine the selected hardware with the actual control requirements to complete the designing of the overall motion control system.Selecting PC as the host computer and the PLC as the slave computer,PC communicates with PLC through RS485.At the same time,PLC can control of the four sets of servo motors in the form of RS-485 bus through another group of 485 ports.(2)According to the actual structure of the visual positioning assembly robot,to establish the kinematics equation by using the first coordinate system of the rod,and solve the articulated variable expression.Analyze the existence ofmultiple solutions of the inverse solution,and use "the closest solution" to get the optimal solution.Using the linear programming method of parabolic transition to complete the path planning and get the final speed and acceleration expression.(3)The PR mode is used to control the servo driver,combine the characteristics of peripheral hardware with the actual functional requirements to analyze the number of I/O points required by the PLC and what functions and characteristics the PLC should have.And on the basis,complete the selection of PLC and its I/O address distribution,complete the design of electrical system and pneumatic system,finish assembling of the control cabinet.Meanwhile,using the modular programming ideas,complete the PLC control system program design with the ladder diagram.Finally,the PLC achieve the accurate control of four groups of servo motor by the RS485 bus and modbus communication protocol.(4)Under the development environment of Visual Studio 2012,the host computer system and human-computer interaction interface are developed by using MFC.C/C++ high-level programming language is used to realize the serial communication between PLC and PC through the RS485 serial port.Meanwhile,the host computer processes the pose information extracted by vision system,and calculates the joint variables,speed and variable by software,then sends the solution to PLC by RS485 after the unit is unified.PLC analyzes the received data and extracts the actual displacement and velocity of each axis.Finally,the motion control system realize two kinds of control modes: manual and automatic.The actual test shows that the PLC can realize the independent coordinated control of the four groups of servo motors through the RS485 bus,and the performance of the motion control system is stable and efficient,which can meet the requirements of high precision assembly in the industrial field and has strong practicality. |
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