Microcontroller

Paper, Order, or Assignment Requirements

 

 

Module: 5ET003 Professional Engineering and the Microelectronics

Assignment 2: Microelectronics Assignment brief:

Embedded Systems Design and Development:- Design and development of an embedded control system for a 4-axis CNC Drilling machine.

 

Introduction

Use PIC16f88 microcontroller to develop an embedded control system for a 4-axis CNC machine carrying out drilling operations on aerospace parts. The manufacture of military aircraft entails rigid demands on the dimensional accuracy of the component parts. One of the demands is a complete inter-changeability of parts without any modification of the pattern of drilled holes. This demand is met by the use of programmable machines. In most cases where a robot is used within aircraft manufacturing it is programmed to handle and position sheet metal parts to make possible further operations using another machine. In this case the CNC machine will be used for performing the machining (drilling) operation. The concept of a CNC drilling machine is to be realised by development of an embedded 4-axis motion control system for this machine that makes use of PIC16F88 microcontroller. The structure of the propose CNC drilling machine control system is shown in Figure1.The work to be drilled and its drill template is shown in Figure 2

Stepper motor 3

 

Figure1  Proposed CNC drilling machine control system.

 

Figure2. Drill template with sheet metal panel

The embedded system shown in Figure1 uses four stepper motors as actuation devices. Two Stepper motors are used for positioning of the worktable, one stepper  motor will be used for position of workhead (drilling tool) and one stepper motor will be used for the process of drilling.

Figure 3 shows worktable movement achieve through rotation of Leadscrew by stepper motor. Worktable bring the work under the drill head through moving in  X-axis and Y-axis or simultaneously in both X and Y directions.

 

 

Figure 3 Worktable movement achieve through rotation of Leadscrew by           stepper motor

 

Stepper motor 3

Figure 4- Mechanism for movement of workhead

Figure 4 Stepper motor 3 will move the workhead to up and down in Z direction

Stepper motor 4 rotates the drill for carrying out the drilling operation

Figure 5 below shows overall structure of 4-axis CNC control system (schematic of  the movement of workhead by Stepper motor 3 is presented for visualisation of  mechanism as well as stepper motor interfacing)

 

 

Figure 5 overall structure of embedded 4-axis CNC control system

 

Requirement

Students are required to elaborate on the concept of CNC control of drilling operation and discuss the design and development of hardware and software required for the realisation of a 4-axis motion control system for the proposed CNC machine. A written report of 3000 (fully referenced) required, the report should include in the following:

 

  • Design outline- More elaborate description of the embedded system to be developed and the purpose of its design and literature review. This section should in particular describe the

– Hardware and software requirement for position and speed control of worktable  – Hardware and software requirement for position and speed control of workhead – Hardware and software requirement for control of workhead (drill) operation.

 

  • Detailed analysis of the proposed system illustrating a generalised block-

diagram of the system and highlighting important features /considerations

 

  • The interfacing of the hardware components to microcontroller (interfaces).
  • Software design:- Flowchart and list of the codes being developed
  • Potential implementation issues (any consideration that would affect development and operation of the system

 

  • Summary and Discussion.

Solution instruction (Guidelines)

Stepping motors are normally used for small robots with low speed and torque requirements. When used for such applications, they have the advantage that they can be operated in open loop mode thereby eliminating the need for interfacing rather expensive feedback transducers.

 

D.C. motors and stepping motors are used for providing rotary motion in robots. Both of these motors are however, unsuitable for directly producing a linear motion. Rotary motion can be translated into linear motion using rack and pinion drives. An alternative possibility involves the use of a lead screw type device whose speed is rather limited.

 

The prospective embedded system will position the worktable under the workhead and moves the workhead in Z direction by first approaching the work in high speed and then moving the workhead (dril) slowly into the work to create holes, and then retrieve the work upward and moving the worktable to a length that allows next hole to be produced in the work. Through consideration of lead-screw’s pitch students should calculate the number of pulses required sending to stepper motors for achieving a particular distance travel, and through the change in frequency of pulse train students should be able to achieve various travel speeds. The use of sensors for any end- stop location detection and for stroke length determination can also be considered.

 

This assignment requires students to interface a keypad and four stepper motors to a

PIC16f88-based microcontroller board and develop appropriate programs (codes) for the microcontroller so that it can scan the keypad and actuate (run) particular stepper motor when particular key on the keypad is pressed.  LCDs can also be Interfaced to the microcontroller to display sensory information and or number of holes produced. Marking criteria:

You are required to investigate and design all the interfacing and the codes required for the development of the proposed embedded system for control of the CNC drilling machine. You should submit an individual report of 3000 words length (fully referenced), including in your report the following:

 

Headings (Tasks / Requirements) Marks
1 Description of the proposed embedded system and the purpose of its design and literature review.   20%
2 Detailed analysis of the proposed embedded system illustrating a generalised block diagram of the system and highlighting important features /considerations including the sensors and actuators required for effective monitoring and supervisory control of CNC drilling operation.

 

10%
3 Hardware specification (how the hardware components connect together and to the microcontroller ( interface). This in particular requires discussion and explanation of

3.1  interfacing of sensors and actuators (motors) to the microcontroller- how many sensors and  actuators used

3.2- interfacing of the microcontroller to LCD for the display of         sensory data/information/feedback.

3.3- interfacing of microcontroller to a Keypad for the issuing of the command

 

signals to the microcontroller to maintain optimum position for worktable and workhead etc,

 

include in this section the code required for the acquisition of data from sensors and their storage into the outstation microcontroller

 

 

 

 

 

 

 

20%

4 Software design:- Flowchart and list of the code

This should include Flowchart and list of codes for individual tasks as well as code for overall continuous operation of the embedded system using sensory feedback and actuation signals. Include in this section the following particular codes:

 

4.1- the code required for the positioning of woktable

4.2- code for receiving keypad command signals into the microcontroller to        maintain an optimum position of workhead and worktable and the actual drilling operation.

 

4.3 Code for transmission of sensory data to an LCD display.

 

4.4 overall code continuous operation of the embedded system illustrating

Use of appropriate LOOPS for the effective execution of the overall tasks of a      CNC drilling machine

 

 

 

 

 

 

 

 

 

 

 

 

 

 

40%

5 Summary and Discussion including recommendation of potential improvement of the system. 10%
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