[Type here] Ty HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY DAI HOC PROJECT REPORT TOPIC: “CONTROL CNC MACHINE TABLE WITH PID CONTROLLER” Student Name: ID number: Class: Instructor: PhD. Hanoi, 02/2023 Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh CHAPTER I: ANALYSIS OF PRINCIPLES AND SPECIFICATIONS.0 0 rr rr nh TK nhà 4 2. Identify the components of the control sys£em.
nàn sexy 7 CHAPTER HI: COMPUTATION METHODS AND INTERPOSAL. - cv TH nh nh nh hen ky 9 2.2 Line interpolation method:. - án vn nh ghi 10 2.3 Circle inferpoÌafion. nh HH gu nh nen hy 12 CHAPTER II: MOTOR CONTROLLING TABLE X,Y BY PID CONTROL.
Build a transfer function model of the sysfem. Qualified transfer function G(s) for table X. Check the stability of the transfer function G($). PID controller design for table X.
Table Yoo rr. Build a transfer function for table Y.2 Qualified transfer function G(s) for table Y. Check the stability of the transfer function G($). PID controller design for table Y.
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49 CHAPTER V: SYSTEM OPERATION SIMULATION WHILE MACHINING IS ALRSO A GIVEN ORIGINAL.- - ch nhe kh 50 5. Export 3D model files to Matlab. Straight line simulafÏOI.---Q ch nh TH nhà 52 5. Circle line inferpoÏafion.
- - - ccc nh nh nọ kh nh 56 2|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh (OF ONC Oo 1 BRS) 0 6) nnn 61 REFERENCE G.ccccccccccccsssseeseeccsseseeeccsssseececceseesececeeeseeeecesenseeecessnssaeanes 62 3|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh CHAPTER I: ANALYSIS OF PRINCIPLES AND SPECIFICATIONS 1. Working principles Control systems in an interdisciplinary field covering many areas of engineering and sciences.
Control systems exist in many systems of engineering, sciences, and in human body. Some type of control systems affects most aspects of our day-to-day activities. Control means to regulate, direct, command, or govern. A system is a collection, set, or arrangement of elements (subsystems).
A control system is an interconnection of components forming a system configuration that will provide a desired system response. Hence, a control system is an arrangement of physical components connected or related in such a manner as to command, regulate, direct, or govern itself or another system. In order to identify, delineate, or define a control system, we introduce two terms: input and output here. The input is the stimulus, excitation, or command applied to a control system, and the output is the actual response resulting from a control system.
The output may or may not be equal to the specified response implied by the input. Inputs could be physical variables or abstract ones such as reference, set point or desired values for the output of the control system. Control systems can have more than one input or output. The input and the output represent the desired response and the actual response respectively.
A control system provides an output or response for a given input or stimulus, as shown in Fig.1 Input: stimulus Output: response ——————> C`°ontroÌ system Desired response Actual response Fig.1 Simple block diagram There are two control system configurations: open-loop control system and closed- loop control system. A block is a set of elements that can be grouped together, with overall characteristics described by an input/output relationship as shown in Fig. A block diagram is a simplified pictorial representation of the cause-and-effect relationship between the input(s) and output(s) of a physical system. 4|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph.
Tao Ngoc Linh »| Physicalcomponents |— y Inputs ——______» ————>y Outputs within the block Block Fig.2 Block diagram of whole control system The simplest form of the block diagram is the single block as shown in Fig. The input and output characteristics of entire groups of elements within the block can be described by an appropriate mathematical expressions as shown in Fig.3 ————* Mathematical F——— Inputs _———————y ặ L_———y_ Oufputs expression ———————* E—————— Fig.3 Block diagram for logic expression (b) Transfer Function. The transfer function is a property of the system elements only, and is not dependent on the excitation and initial conditions. The transfer function of a system (or a block) is defined as the ratio of output to input as shown in Fig.4 Input Output ————————y_ lransferfunclon | ————————————>y Fig.4 Block diagram for transfer function Transfer functions = Transfer functions are generally used to represent a mathematical model of each block in the block diagram representation.
All the signals are transfer functions on the block diagrams. §|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh For instance, the time function reference input is r(t), and its transfer function is R(s) where t is time and s is the Laplace transform variable or complex frequency. Transfer functions can be used to represent closed-loop as well as open-loop systems.
(c) Open-loop Control System. Open-loop control systems represent the simplest form of controlling devices. A general block diagram of open-loop system is shown in Fig.5 Disturbance Disturbance input | input 2 Di(s) D:(s) Reference Input Ez(s)|_ | UG@) ; | Output Input > transducer pj G(s) | »ị Q;(S) ) > Controlled R(s) 1 variable Controller Plant or process Fig.5 Block diagram of opened-loop system (d) Closed-loop (Feedback Control) System. Closed-loop control systems derive their valuable accurate reproduction of the input from feedback comparison.
The general architecture of a closed-loop control system is shown in Fig. A system with one or more feedback paths is called a closed-loop system. 6|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh Disturbance Disturbance input | input 2 D,(s) D,(s) Reference alS j Output Input <Yy [Controlled R(s) Controller Plant or S¥™™INg] variable Forward process Pe C(s) path Feedback path H(s) |4 L_— Output transducer or sensor Fig.6 Block diagram of closed-loop system 7|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph.
Tao Ngoc Linh 2. Identify the components of the control system Down below are some notable about benefits of closed-loop control system - These systems are exceedingly precise and faultless. - Errors can be fixed through feedback signals. - It supports better for automation.
- They are not affected by interference. So, I choose closed-loop control system for CNC machine. Control system is closed-loop with feedback path: Control signal Controller >| Motor +| Mechanical | _—> | Feedback signal Encoder Position |4———————— — Fig.7 The structure diagram of the CNC machine The control system consists of the following main components: + Actuator: Motor: transmit motion to the lead screw through coupling. Coupling and ball screw system: transmit motion to the machine table Machine table.
+ Sensor: Encoder: as a measuring device to assist CNC machining achieve high precision, determine the precise location of the machine axes and the position of the cutter Optical ruler, magnetic ruler. Cruise switch or travel sensor, temperature sensor, pressure sensor for lubrication and cooling systems. + Control devices: Drivers for motors, PCs, PLCs. 8|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph.
Tao Ngoc Linh Spindle | Encoder/ Motor Coupling | Sensor Control | From controller— Sơn |__ FE DODD To controller Feedback measurements Fig.8 Feed drive mechanism with a lead screw drive In this project, I will control the motor to construct a CNC machine table controller. This controller requires fewer than 5% overshoot, a response time of less than 0.5s, and the system clings to the input excitation signal. 9|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh CHAPTER IT: COMPUTATION METHODS AND INTERPOSAL 2.
Interpolation method On numerically controlled machine tools, the line of action between the tool and the part is formed by shifting coordinates on multiple axes. To produce a machined profile, there must be a functional relationship (linear or non-linear) between the motions on each of the individual coordinates. The fulcrums must be located so densely that the resulting machined profile is sufficiently precise (no point is out of tolerance). The coordinate values of the intermediate points are found in a cluster of numerical control functions called the interpolator.
Interpolator task: - Find out the position of intermediate points that allow the formation of a given profile within a specified tolerance. - The speed given the positions of the intermediate pots must match the tool speed. - Go to the correct points and end the progress. To determine the required values of position on individual axes, different interpolation methods are applied.
If classified according to the algorithm used, we can distribute the interpolation in 2 groups: - Group |: devices that work on the principle of evaluation and fractional integral parts. - Group 2: devices working on the principle of mtegral numbers. If classified by implementation method, there are 2 types: - Using hardware - Using software Technically, the implementation of interpolation by analog or digital working devices: - Simple analog-style interpolator with limited accuracy. - In fact, people use interpolation according to the number principle.
Calculating interpolation of functions im numerical form is done by 3 methods: - Calculate functions directly from the curve in the form of a mathematical function f(x,y,Z) 10|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh - Calculate the parameters of the curve in real time. - Converting the eigenvectors of the system to differential equations for numerical calculation will find the toolpath values through the sum of the differentials. This method is called Digital Diferential Analysis (DDA) method.2 Line interpolation method: +Definition: The drill head is moved from the beginning to the end of the stroke in a straight line sequence.
+ Implementation: Line interpolation along 2 or 3 axes + Required parameters: Start point coordinates, end point coordinates. Movement speed per axis. + Possibility: Theoretically, line interpolation can make any curved trajectory, but the amount of data to be processed is very large. Using arc, parabolic, and helix interpolation reduces the amount of data to be programmed.
Pp - a “+ Interpolated y -~ point 11|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph. Tao Ngoc Linh | XZ^.1 Line interpolated Example: Interpolate from pointA to point E Using the method “Digital differential analysis” Consider a knife that needs to be moved from : From starting point P, to ending point P; in a straight line with a specified tool speed u .2 Example of line interpolation L: Path different from F, to Fr So in time: T = L/u. Line components ( Xs-X,) and (Yr-Ya) have to process. Coordinates of intermediate positions are calculated as a function of time: M1) =X, [Ved = Ket [AEA yt)t) =Y,+=¥, + [Vd = X+ [= Yeo[— [Vyd=X+ a Divide the time T into 4 =F/N sufficiently small intervals du nho , Integral can be replaced by numeric addition: 12|Page Hanoi University of Science and Technology Project Design Control System for CNC Machine School of Mechanical Engineering Instructor: Ph.
Tao Ngoc Linh x(t) =x nA,) =X, et n N y(t) =y(n.A,) =, + Ye Ky N For n =1,2,3.n With each addition step, the position value is increased by a constant step by one.
