PROJECT DESCRIPTION
One main field of activity of the Department of Mechanical Engineering and Material Science at the Escuela Superior de Ingenieros de Sevilla is material fatigue testing. In order to evaluate material characteristics under specified conditions, material probes are outset to biaxial movements, i.e.
traction or pressure, and
torsion.
The machines for this particular application typically use hydraulics for the power generation; the exact movement is achieved by servo-ventils. Industrial manufacturers demand at least 300.000 € for building a machine like that. This appears very expensive, keeping in mind the very basic task of the machine. Whereas a university of western industrialized countries may bear inversions like that, for universities of third world it is hardly possible to procure such a machine.
This was the motivation for the Department of Mechanical Engineering and Material Science at the Escuela Superior de Ingenieros de Sevilla to start a project in order to find a cheap as well as reliable solution for biaxial material fatigue testing.
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Table of Contents
Chapter 1: Project description
Chapter 2: Main concept
Chapter 3: Stepper Motors
3.1 Types
3.1.1 Variable Reluctance Motors
3.1.2 Unipolar Motors
3.1.3 Bipolar Motors
3.1.4 Multiphase Motors
3.2 Stepper Motor Parameters
3.3 Characteristics of the particular motors chosen
Chapter 4: Low-level Control
4.1 H-Bridge
4.1.1 Switching elements: IGBT vs. MOSFET
4.1.2 Low-side Switch
4.1.3 High-side Switch
4.1.4 Circuit design of the H-Bridge
4.2 Short Circuit Avoidance
4.3 Current Control
4.3.1 Pulse Width Modulation
4.3.2 The 555 timer circuit
4.3.3 Reference Voltage
Chapter 5: Mid-level Control
5.1 Moore Machine
5.2 Step Synthesis
5.3 Sequential Logic
5.4 Reset and Enable
5.5 Interface
Intersection: The Low- and Mid-level-PCB
Chapter 6: High-level Control
6.1 Timing Devices
6.1.1 Interrupts
6.1.2 Timing Hardware
6.1.3 Timing Routines
6.1.3.1 The Procedure SetTimerSpeed
6.1.3.2 The Function GrabTimer
6.1.3.3 The Procedure SetTimerHandler
6.1.3.4 The Procedure InternalHandler
6.1.3.5 The Procedure DisableHandler
6.1.3.6 The Procedure NormTimerSpeed
6.1.3.7 The Procedure ResetTimer
6.2 I/O-Management
6.2.1 Developing an ISA I/O-Card
6.2.2 The Parallel Port
6.2.3 I/O-Routines
6.2.3.1 The Procedure MotorWrite
6.2.3.2 The Procedures Motor1Move and Motor2Move
6.3 Control Routines
Chapter 7: Human Machine Interface:
7.1 Turbo Vision
7.2 The TFatigueControl Object
7.2.1 Desktop and Menu Design
7.2.2 Options-Window
Chapter 8: Summary and outlook
Research Objectives and Topics
The thesis aims to develop a cost-effective and reliable control system for a biaxial material fatigue testing machine. The research investigates whether stepper motors can replace traditional hydraulic systems to simplify the mechanical design and reduce overall costs.
- Design of a three-level control system (Low-level, Mid-level, High-level)
- Utilization of stepper motors as cost-effective actuators
- Implementation of a robust current-mode control using an H-Bridge
- Integration of a Human-Machine Interface (HMI) via Turbo Vision
- Development of hardware and software routines for real-time motor control
Excerpt from the Book
4.1 H-Bridge
As bipolar stepper motors have no center taps on their windings, the current through the winding needs to be reversed, in order to reverse the direction of the field produced by a motor winding. This is realized in form of an H-bridge as shown in Figure 4.1:
H-Bridges for smaller stepper motors (up to approx. 50V and 4A) are already available as integrated circuit solutions. However, the above selected motors exceed by far the characteristics of such an IC, so there remains only the possibility of a discrete design. Certainly the switching elements are the most important components, so the next subsection deals with them.
Summary of Chapters
Chapter 1: Project description: Defines the motivation for finding a low-cost alternative for material fatigue testing using stepper motors.
Chapter 2: Main concept: Outlines the hierarchical division of the control system into three levels and the introduction of a Human-Machine Interface.
Chapter 3: Stepper Motors: Explores different types of stepper motors and the parameters relevant for the chosen configuration.
Chapter 4: Low-level Control: Details the design of the H-Bridge, including switching elements (IGBT/MOSFET) and current control methods.
Chapter 5: Mid-level Control: Describes the implementation of a Moore Machine for stepping sequences and sequential logic using synchronous counters.
Intersection: The Low- and Mid-level-PCB: Explains the physical implementation of the controller electronics on a printed circuit board.
Chapter 6: High-level Control: Covers timing hardware, interrupt management, and I/O routines for communication with the control board.
Chapter 7: Human Machine Interface:: Focuses on the implementation of the user interface using Turbo Vision and the management of desktop and options windows.
Chapter 8: Summary and outlook: Reviews the project achievements and suggests future potential improvements.
Keywords
Stepper Motors, Material Fatigue Testing, H-Bridge, Current Control, Pulse Width Modulation, Real-time Control, Turbo Vision, HMI, ISA I/O-Card, Sequential Logic, MOSFET, IGBT, Embedded Systems, Bipolar Motors, Motor Control
Frequently Asked Questions
What is the core purpose of this research project?
The project focuses on designing an affordable and robust control system for a biaxial material fatigue testing machine to replace expensive hydraulic systems used in universities.
What are the primary technical fields covered in the work?
The work integrates mechanical engineering, electrical circuit design, real-time software programming, and user interface development for industrial control applications.
What is the main goal of the control design?
The primary goal is to achieve precise biaxial movement using two stepper motors in an open-loop control configuration, significantly reducing costs while maintaining reliability.
Which scientific methods were employed?
The research uses bottom-up hardware design, OrCAD simulation for circuits, state-machine modeling (Moore Machine) for control logic, and interrupt-driven software programming.
What does the main part of the thesis examine?
The main section examines the three-level control architecture: the H-Bridge for current supply, sequential logic for motor states, and high-level control using old PC architecture.
Which keywords characterize this thesis?
Key terms include Stepper Motors, Bipolar Motors, H-Bridge, Pulse Width Modulation, Turbo Vision, Real-time Control, and Material Fatigue Testing.
How is short-circuit protection implemented in the H-bridge?
Short-circuit avoidance is handled at a low level by incorporating specific sequential logic and diodes to manage voltage spikes during switching transitions.
What is the function of the Turbo Vision interface?
Turbo Vision provides an object-oriented application framework to build a text-mode HMI, allowing users to issue movement commands and monitor system status in real-time.
- Quote paper
- Jörg Henseler (Author), 2001, Designing a Control for a Material Fatigue Testing Machine, Munich, GRIN Verlag, https://www.grin.com/document/6661
