Jack, H., “Industry Concerns in Controls and Automation Courses for Mechanical and Manufac­turing Students”, The 2004 National Conference on Integrating Practice into Engineering Education, Dearborn Michigan, Oct, 2004.

Addressing Industry Concerns in Controls and Automation Courses for Mechanical and Manufacturing Engineers

 

Hugh Jack, Associate Professor, School of Engineering, Grand Valley State University

 

Abstract

 

In controls and automation the curriculum in higher education and actual industrial practices are disconnected. The widely taught approach to controls education focuses on linearized feedback control systems. However, in practice these types of problems constitute a trivial part of the controls work a practicing engineer will do. Industrial control problems normally have discrete state outputs and inputs and require sequential logic design methodologies. The gulf between academic perceptions and industrial needs can be bridged through careful curriculum redesign, and the use of industrial equipment. This paper describes an industrially relevant three course sequence in automation and controls that addresses topics in system modeling, feedback control, discrete control systems, communication and integrated manufacturing systems.

 

Introduction

 

The mission of the School of Engineering at Grand Valley State University is to support the needs of the community. In Michigan that primarily means a large manufacturing base including producers of furniture, automotive parts, avionics systems, industrial equipment, consumer products and medical devices. Industrial concerns are addressed in all aspects of the curriculum design and delivery. Mechanical and Manufacturing Engineering graduates are expected to make contributions immediately after graduation by applying engineering theory and methods to solve industrially relevant problems.

 

The controls and automation sequence is built upon a foundation of C programming in EGR 261 - Structured Programming in C and EGR 226 - Introduction to Digital Systems. EGR 261 is a lecture and laboratory based course in C programming taught at the freshmen level for engineering and computer science students. This is followed by EGR 226, a sophomore level lecture and laboratory based course that explores microcontroller programming and application. At the end of this course the students have knowledge of topics such as basic digital and analog IO, interrupts, timers, counters and structured programming techniques.

 

In the first semester of the junior year the students take EGR 345 - Dynamic Systems Modelling and Control. The lecture component of the course covers modelling mechanical and electrical systems, including DC motors. The students analyze these systems using differential equations, standard first/second order forms, state equations, numerical methods, Laplace transforms, block diagrams, phasors, Bode plots and multi-axis motion. These support industrially relevant laboratory topics such as PID feedback control, motion control systems, sensors, actuators and analog IO. The laboratory portion of the course begins with students developing a feedback control system using C to program 68HC11 microcontrollers. These controllers include PID compensation, deadband correction, motion profile generation, PWM outputs and H-bridge control. The second half of the course involves the use of industrial hardware and software such as Labview with DAQ cards, Variable Frequency Drives and Simulink.

 

EGR 450 - Manufacturing Control Systems is offered in the second semester of the junior year. It is required for Manufacturing students but is an option for Mechanical students. It focuses on sequential control systems using commercial Programmable Logic Controllers (PLCs) as the target platform. Topics include electrical system design, sensors and actuators, Boolean algebra, timing diagrams, structured logic design, state diagrams, data types, advanced programming instructions including interrupts, analog IO, serial communication and networking. The laboratories involve weekly experiences where students build, program, debug and document control systems using industrial components and practices. The course culminates with a major design project, normally done for a local company.

 

The final course in the sequence is EGR 474 - Systems Integration. It is offered to Manufacturing engineering and Electrical and Computer Engineering students as an elective. The course focuses on integration of manufacturing systems using programming and databases to combine the system components including a robot, CNC mill, material handling system with Devicenet, vision system and a web based interface.

 

The hands-on use of industrial equipment throughout all courses allows the students to understand the context of the theory and increases their interest. As a result the students are more eager to learn the theoretical fundamentals in the control sequence. This actually leads to the counterintuitive result that by doing hands-on work the students are able to learn more theory at a higher level.

 

EGR 345 - Dynamic System Modeling and Control

 

EGR 345 is the first of the three course sequence and is required for all Mechanical and Manufacturing engineering students in their fifth semester. The course format is three one hour lectures, and a three hour lab each week. The course originally began in a traditional format focusing on modeling and control of linear systems using Laplacian techniques. It has since evolved to become a mature modelling course focusing on methods and topics more relevant to non-electrical engineers [4]. Along with this, the laboratories were redesigned to make generous use of industrial hardware and software.

 

The primary shift in the theoretical part of the course was to deemphasize Laplace transforms and increase the emphasis on analysis techniques using calculus and numerical methods. At the completion of the course students are quite adept at analyzing complex systems, including non-linear models. Moreover, the additional time spent solving differential equations helps to resolve fundamental mathematical deficiencies [5]. In theoretical terms most of the traditional linear controls analysis techniques are still available. In many cases the Laplace operator ‘s’ and the differential operator ‘d/dt’ are interchangeable. The topics now covered in the course are listed in Table 1. The elimination of Laplace transforms also made it possible to expand the topic list to include motion control, sensors, actuators and Analog I/O.

 

A list of previously used laboratory experiments is given below. The students use industrial hardware, software and sensors to conduct experiments in the first half of the semester (experiments 2 to 7). For example, in experiment 6 a cylinder that contained a combined spring-damper combination was investigated. The students determined the spring coefficient using forces and displacements. The damping coefficient was then determined by measuring position as a function of time using an ultrasonic range sensor. The data was collected using Labview and a data acquisition card. By the end of experiment 7, students were able to select and use sensors such as accelerometers, potentiometers, proximity sensors (photo, inductive and capacitive), ultrasonic range sensors, strobe tachometers and load cells. They were also exposed to issues of electrical wiring, noise and some simple filtering strategies.

 

1. Web page creation and Mathcad tutorial/review

2. Computer based data collection with Labview

3. Sensors (accelerometers, potentiometers, ultrasonic, etc.)

4. Permanent magnet DC motor modeling

5. Proportional feedback controller

6. Spring and damper modeling

7. Torsional oscillation of a mass on a thin rod

8. Servo control systems - Allen Bradley Ultra 100 drives

9. Servo control systems and programming in C - Allen Bradley Ultra 5000 drives

10. Op-amp audio filters

11. Stepper motor controllers - Vexta drives and motion controllers

12. Variable frequency drives - Allen Bradley 161 series

 

Labs 8, 9, 11 and 12 focussed on industrial motors and controllers. The labs started with tutorials to get the students acquainted with the hardware, followed by further investigations. In the servo motor and VFD labs the students were exposed to the effects of motor control variables. They changed PID controller variables to make the systems under/overdamped or unstable. The stepper motor

 

Table 1: Course Topics

Topic

Description

Translation

developing differential equations for linear translation.

Calculus

solving non-homogeneous differential equations, first and second order forms, and solving non-linear systems.

Numerical methods

state equations, first order numerical integration, runge-kutta techniques, splines and tabular data.

Rotation

developing differential equations for rotational systems

Input-output equations

combining systems of multiple differential equations into a single differential equation.

Circuits

developing differential equations for circuits.

Feedback control

converting input-output equations to transfer functions and modeling feedback control systems with block diagrams.

Fourier analysis

using fourier transforms (phasors) to solve for steady state oscillation cases.

Bode plots

developing Bode plots for transfer functions.

Root-locus plots

determining system stability with root-locus plots.

Motion control

position/velocity/acceleration profiles and setpoint scheduling.

Analog I/O

quantized analog voltages

Sensors

for position, temperature, etc.

Actuators

induction, permanent magnet and stepper motors.

lab introduced them to the concept of a velocity profile.

At the completion of this course the students are able to analyze all of the problems that they could in the Laplace version. However, they were also able to analyze much more complex (non-linear) problems, and they had knowledge of industrial hardware.

 

EGR 450 - Manufacturing Control Systems

Manufacturing Control Systems is the second course in the sequence, and is required for all Manufacturing engineering students in their sixth semester. It is also a popular option for students in Mechanical engineering. The format for the course is three one hour lectures, and a three hour lab, each week. This course primarily uses Programmable Logic Controllers (PLCs) as the basis for the analysis and design of discrete event control systems [6].

This type of course is uncommon and is rarely found at the university level. This is primarily because PLCs in the 1970s and 80s were very limited in complexity and application. Since then they have grown to be ubiquitous in industrial equipment. The have also become much more sophisticated and have become the subject of research in some cases [7]. By offering this course, GVSU has been able to distinguish itself among local companies, and many of our graduates have become controls engineers as a result. The topics in the course are listed below.

 

1. PLC wiring and interfacing

2. Logical sensors and actuators

3. Combinatorial logic with Boolean algebra

4. Timers, counters and basic structured design techniques

5. Sequential logic design with state diagrams

6. Number systems

7. Basic and advanced data functions

8. Analog I/O

9. PID control

10. Data communications

 

These topics are closely tied to lab exercises. In general, labs required the students to design a program, and then debug it in the lab. The labs also help develop documenting habits and practices. The labs are listed below. Labs 1 to 6 cover fundamental logic techniques and topics that would be expected from a technician. Labs 7 and 8 focus on feedback controller implementations. Lab 9 focuses on interfacing controllers to communicate data. Labs 10 and 11 allows the students to work in small teams to develop control programs for a four station line. They must then integrate the four controllers to communicate and control the line. Finally the students integrate a vision system with a PLC in lab 12.

 

1. Introduction to Micrologix PLCs - tutorial

2. Simple logic design - combinatorial stamping press control

3. Sensors, actuators and wiring - introduction to industrial wiring and sensors

4. Intermediate ladder logic design and PLC interfacing - encoder controlled motor

5. Introduction to PLC-5s - tutorial

6. Advanced ladder logic design and PLC interfacing - sequential traffic lights

7. Analog I/O

8. PID Control of a DC motor

9. PLC Networking and Serial Communications - with DH+ and RS-232C

10. Control of a multistation keytag maker

11. Control of a multistation keytag maker (cont’d)

12. Interfacing to a DVT vision system

 

This course concludes with a major project that involves the design and construction of a control system to control a real process. In the summer of 2001 seven of the twelve projects were done for local companies.

EGR 474 - Systems Integration

 

The third and final course in the controls sequence is the Integrated Manufacturing Systems course, EGR 474. This course is an elective designed primarily for senior manufacturing engineering students, but it is also open to students in electrical and computer engineering. In the original format the course took the ‘grab-bag’ approach to topical coverage that is typical in other universities and texts. Since then it has evolved to focus on hands-on development. In the current format it uses two classes per week, each three hours long. Students are expected to read the text [8] before each class. During the class time they then follow tutorials to familiarize themselves with the technology, and then work with the equipment at a higher level.

 

Students entering the course already have a knowledge of C/C++ programming, and some experience implementing computer and/or PLC based controls. Early in the course students set up a Linux computer to act as a network/web server, and a development platform. This is subsequently used to develop drivers for communication over networks, serial cables and with an SQL database [9]. After this, students get exposure to low level devices such as robots, write drivers to communicate with them, and work towards developing higher level control architectures, as shown in the following topic list.

 

1. Installing Linux and setting up a web server

2. Basic C programming review - a number guessing game

3. An Introduction to SQL databases - using a command line interface

4. Using programs to communicate with an SQL database

5. Using C to communicate over the serial port

6. Exploring hardware; (note: each student is given a different device)

- DAQ card

- robot

- stepper motor controller

- PLC-5

- Labview based vision system

- HMI

- CNC machines

7. Writing device drivers;

- each student writes a device driver for the hardware used in 6.

- they present the results to the class with a brief tutorial document.

8. The project.

 

In this typical sequence, students get familiar with servers and mature operating systems in topics 1 and 2. Topics 3 to 5 deal with communications issues and device drivers. Topics 6 and 7 prepares them to deal with a device in depth and gain some expertise. Students then shared this expertise with their classmates through oral presentations and written tutorials. Finally, the project allows the students to partake in the design and implementation of a mature integrated system.

 

The workcell was designed and developed by the students from beginning to end. The objective the class of 2001 selected for the workcell was to mill out pen holders on 6” by 6” boards. They would be customized with a ‘S’ or ‘M’ logo, for one of two nearby football teams. The students planned the architecture for the system shown in Figure 1. They divided the work into smaller tasks, and then implemented and tested the system.

 

The physical layout of the system is shown in Figure 2. The cell is interconnected by a material handling system with straight track sections and turntables. The carts are controlled by ‘lock-and-gos’ which can lock to stop a cart and the propel it with a pneumatic air cylinder. On the straight track sections the lock-and-gos are in the center of the sections. The turntables have a stepper motor controller that will sense the presence of carts, rotate appropriately, and then ‘kick’ the carts to the next station. In the system the turntables use self contained controllers, but the other cylinders on the straight track sections are actuated by a Devicenet based control system.

 

In the design chosen by the students, an order is placed on a computer via a web browser. This then causes a wood block to be ejected from the feeder. A robot loads this into the CNC mill where the ordered pattern is cut. After this the pen holder is loaded onto a cart, and moved to the vision station where it is checked for correctness. If it is not correct the pen holder is ejected at the ‘eject’ station, and the process restarts at the feeder station. Otherwise the cart continues round to the ‘Pickup’ station where the block is given to the customer. After this the cart returns to the pickup point. This is summarized in Figure 3.

 

All of the software in the system was written and run under Linux, with the exception of software for programming the vision systems. The programs all communicated through the SQL database to coordinate device actions, and to track order data.

 

At the conclusion of this course is that students are able to develop a high end integrated manufacturing system within a single course using industrial equipment. This was not possible when using the older ‘grab-bag’ course outline, or using desktop oriented operating systems.

 

 

Summary

 

Most engineering curriculum focuses on a narrow region of theoretical problems and equipment that leave students unable to solve industrial problems. This paper has presented an approach, in three courses, that is theoretically mature, but leaves students able to implement common industrial control systems. This benefit is further enhanced by using industrial grade hardware and software that is commonly seen in industry. Students recognize the relevance to practice and are much more willing to learn difficult topics within this context. This also appeals to employers who are able to hire recent graduates who are quickly capable of being productive contributors. The success of the approach can be measured through the senior projects in the school of engineering. For example, in 2001 there were 5 projects done in teams of 4 to 6 students with an average industrial contribution of $20,000 for each project. The project topics were;

 

• A servo controlled glue deposition system - a two axis servo controlled glue over multiple paths was designed and build for a local manufacturer. The machine is now in use in production preparing cloth patterns for bus seats.

• A door beam thickness tester - a PLC based machine was designed and build for an auto parts manufacturer that would gauge door beam thickness for 100% inspection. This machine in now used in production.

• Altitude testing chamber - a chamber was purchased and temperature and pressure controls were added. This included a Labview based system, and VFD. The system is in use in the testing lab of a local avionics manufacturer.

• Combined Bending and Torsion Apparatus - this project involved the design and build of a pressure vessel that could have bending and torsion loads applied, and the stress measured. The system uses Labview for data collection, and is currently being used to support an undergraduate course.

• Die Readthrough - This was a research project for a local auto parts manufacturer who was examining the effects of die changes. The students used Labview as an integral part of their data collection and analysis system.

 

Biography

Hugh Jack is an Assistant Professor in the School of Engineering at Grand Valley State University. He has been teaching there since 1996 in the areas of manufacturing and controls. His research areas include, process planning, robotics and rapids prototyping. He previously taught at Ryerson Polytechnic university for 3 years. He holds a Bachelors in electrical engineering, and Masters and Doctorate in Mechanical Engineering from the University of Western Ontario.

 

References

[1] EGR 345 - Dynamic System Modeling and Controls course page, http://claymore.engineer.gvsu.edu/~jackh/eod/egr345.html

[2] EGR 450 - Manufacturing Control Systems course page, http://claymore.engineer.gvsu.edu/~jackh/eod/egr450.html

[3] EGR 474 - Systems Integration course page, http://claymore.engineer.gvsu.edu/~jackh/eod/egr474.html

[4] Jack, H., “ Dynamic System Modeling and Control”, http://claymore.engineer.gvsu.edu/~jackh/books.html, 2002.

[5] Adamczk, B., Reffeor, W., Jack, H., “Math Literacy and Proficiency in Engineering Students”, ASEE Annual Meeting, Montreal, Quebec, June 2002.

[6] Jack, H., “Automated Manufacturing Systems; with PLCs ”, http://claymore.engineer.gvsu.edu/~jackh/books.html, 2002.

[7] Feldmann, K., Colombo, A.W., Schnur, C., Stokel, T., “Specifications, Design, and Implementation of Logic Controllers Based on Colored Petri Net Models and the Standard IEC 1131 Part I: Specifications and Design”, IEEE Transactions on Controls Systems Technology, November 1999.

[8] Jack, H., “Integration and Automation of Manufacturing Systems ”, http://claymore.engineer.gvsu.edu/~jackh/books.html, 2002c.

[9] Postgres database web site, http://www.postgresql.org

 

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