Using NI ELVIS and LabVIEW for DC Motor Speed Control in an Overhead Gantry System
Print
Author(s):
Alex See, Ph.D. -
Monash University Malaysia, School of Engineering
William Suryandri Lavi - Monash University Malaysia, School of Engineering
Industry:
Education
Products:
NI ELVIS, PXI/CompactPCI, LabVIEW
The Challenge:
Teaching students to control the speed and direction of a DC motor and detecting the rotational speed of the motor in overhead gantry application.
The Solution:
Using National Instruments LabVIEW 7 Express, NI ELVIS, and PCI-6070E to develop the system with motion control, data acquisition, and signal measurements capabilities.
"We believe this learning approach and the appreciation of PWM techniques and data acquisition fundamentals have been made easier using NI products. "
Developing a Software-Controlled Overhead Gantry System Using DC Motors
Automation systems are essential for many purposes, mainly for enhancing system performances and reducing human labor in laborious activities. Motors are necessary in a large number of applications. Electronic devices, such as automatic doors, winch systems, or even CD players, use motors to function.
Second-year mechatronics students at Monash University Malaysia are required to enroll in a course module known as Project and Practice, GSE2800, which promotes learning through a hands-on approach. This module, which comprises a one-hour lecture and three hours of laboratory work per week, lasts for 13 weeks in the second semester of each year. In 2004, we divided the students into eight groups, and we instructed each group to solve and achieve the objectives specified. One of the projects we initiated used NI ELVIS in DC motor speed control for an overhead gantry system.
Overhead gantry systems are not new in the industry and can be widely found. Overhead gantry systems are also applied and can be found outside industrial fields. One example of such applications includes using an overhead gantry system in a coin-operated toy machine. This machine is normally controlled by joysticks to pick up an object, for instance a toy doll, as a prize. The pick-up tool in use is an overhead gantry system. We designed our project to control various DC motors in this overhead gantry system using NI ELVIS and LabVIEW software. We developed a prototype of this overhead gantry system, and it resembled the real application system.
Creating a User-Friendly, Reliable System
In this project, students used LabVIEW 7 Express and NI ELVIS. We chose NI ELVIS because it uses LabVIEW -based software instruments, a multifunction DAQ card, and a custom-designed benchtop workstation and prototyping board to provide the functionality of a suite of common laboratory instruments.
We chose LabVIEW in this application for a number of reasons. First, LabVIEW is different from other programming software. Because LabVIEW is a graphical programming language instead of text-based programming, it is much easier to learn or create programs. From our past experiences, we found that LabVIEW was popular among students. The learning curve for LabVIEW programming is significantly shorter when students already have fundamental programming concepts. LabVIEW software uses dataflow programming, which means that the flow of data determines whether or not the program functions. Unlike text-based programming where commands or codes and instructions determine the operation of the program, LabVIEW contains a comprehensive set of tools for acquiring, analyzing, displaying, and storing data, as well as tools to help the users to troubleshoot the codes. LabVIEW -based applications directly transform the PC into a virtual instrument, which gives the user-friendly environment designed specifically to meet the demands of engineers and scientists.
Using DC Motors and Sensors to Implement the System
We used four DC motors in this system, two of them for y-direction movement, one for x-direction of motion, and another one for z-direction. Our main objective was to control the speed as well as the direction of the four motors. The students acquired and computed the rotational speed of the motors by using photoelectric break-beam sensors. They also connected all of these devices to the main NI ELVIS board and monitored and controlled the whole system through a PC using LabVIEW .
In this work, students had the opportunity to use NI ELVIS for generating a pulse width modulation (PWM) signal for motor speed control. This PWM technique uses a square waveform with a variable duty cycle. Students could adjust the duty cycle, and the speed would increase or decrease accordingly. There were various methods from which the square waveforms could be generated from NI ELVIS. They were from analog output, digital, or counter channels in the prototyping board of NI ELVIS. This system required three channels because there were two motors which ran at the same speed (y-direction movement) and shared one channel by connecting them in parallel. We used counter outputs because counter has the fastest response to changes. Counter has the shortest lagging time as compared to analog output. However, there are only two counter output channels from the NI ELVISboard. Another option for the waveform generation was by using analog output.
For rotational motor speed detection, the students employed photoelectric break-beam sensors, which acted like tachometers. To complete the sensing mechanism, the students attached a disk about 2 cm in diameter with a slot about 0.5 cm wide and 1 cm deep to the shaft of the motor. The disk was a solid oblique aluminum material. In operation, each revolution of the motor generated one pulse. The students could detect the pulse by using analog input channels at the NI ELVIS prototyping board. For motor direction control, the students used a H-Bridge IC 293D.
NI ELVIS and LabVIEW Provide Hands-On Practice in Mechatronics Courses
In this project, the students were exposed to virtual instrumentations with real implementation in the mechatronics field. Through the use of NI ELVIS and LabVIEW , we introduced the students to the the fundamentals of PWM technique in DC motor speed control and data acquisition. It is clear that there are enormous advantages using LabVIEW for undergraduates learning. We believe this learning approach and the appreciation of PWM techniques and data acquisition fundamentals have been made easier using NI products.
Related Case Studies
Georgia Institute of Technology Simplifies Teaching Circuit Design with NI ELVIS, NI LabVIEW, and NI MultisimDesign of an Atomic Force Microscope using NI ELVIS and LabVIEW
DeVry University Teaches Electronics and Circuits Courses Using NI ELVIS and NI Multisim
Quanser Integrates NI LabVIEW Control Design and Simulation Tools with Hands-On Controls Experiments
PosiCon Ball – A Laboratory Experiment to Teach Control Systems Design
|
|