Position Control of Manipulator using PMAC with DC Servo Motors
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24-02-2011, 10:58 AM
P. BHAVYA GEETHIKA
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Position Control of Manipulator using PMAC with DC Servo Motors
The “Defence Research and Development Laboratory” (DRDL) in Hyderabad, formerly directed by A.P.J. Abdul Kalam, is the main research center for the Integrated Missile Development Program. It is located in the Defence Research Complex at Kanchanbagh, on the periphery of Hyderabad Old City.
“Defence Research & Development Laboratory” (D.R.D.L) is one of the laboratories of DRDO, which was formed in 1958 from the amalgamation of the then already Functioning Technical Development Establishment (TDEs) of the Indian Army and the Directorate of Technical Development & Production (DTDP) with the Defence Science Organization (DSO). DRDO was then a small organization with 10 establishments or laboratories. Over the years, it has grown multi-directionally in terms of the variety of subject disciplines, number of laboratories, achievements and stature.
Today, DRDO is a network of 51 laboratories, which are deeply engaged in developing defence technologies covering various disciplines, like aeronautics, armaments, electronics, combat vehicles, engineering systems, instrumentation, missiles, advanced computing and simulation, special materials, naval systems, life sciences, training, information systems and agriculture. Presently, the Organization is backed by over 5000 scientists and about 25,000 other scientific, technical and supporting personnel.
Several major project and implimentations for the development of missiles, armaments, light combat aircrafts, radars, electronic warfare systems etc are on hand and significant achievements have already been made in several such technologies.
The Delta-Tau Systems, Inc. Programmable Multi-Axis Controller(PMAC) is a family of high performance servo motion controllers capable of commanding upto eight axes of motion simultaneously with a high level of sophistication. Through the power of a Digital Signal Processor (DSP), PMAC offers a price-performance ratio for multi-axis control that was not previously available. Motorola’s DSP 56001 is the CPU for PMAC, and it handles all the calculations for all eight axes.
As a general purpose controller , PMAC can serve in a wide variety of applications, from those requiring sub-microinch precision to those needing hundreds of kilowatts or horsepower. Its diverse uses include robotics, machine tools, paper and lumber processing, assembly lines, food processing, printing, packaging, material handling, camera control, automatic welding, silicon water processing, laser cutting and many others.
The project and implimentation work aims at controlling the position of DC servomotor using DC servo drive. PC based position controlling is done for single or multi-axis. Desired Position Command is given to the PMAC through PEWIN32PRO software which gives its output to Servo Drive to drive the servomotor at specific speed, direction and position. Out of the four hardware versions, the non-turbo type PMAC-PCI Lite is used.
CHAPTER 1: OVERVIEW
This project and implimentation is aimed to demonstrate the feasibility of integrating the DC servomotor to the clamping mechanism and controlling its position through Programmable Multi Axis Controller called PMAC with Dc servo drive.
1.2 Aim of the project and implimentation
• Integration of DC servomotor to clamp mechanism with DC servo drive.
• Interfacing of Programmable Multi Axis Controller to the DC servo drives in closed loop.
• Parameter optimization and Tuning of the drive.
As the system employ the PC based stand alone controller, the precise positioning of the table become possible with the soft CNC, motion control program and PLC for I/O control of the system.
The controller involved in this application is Programmable Multi Axis Controller (PMAC). It is a high performance servo motion controller capable of commanding up to 8 axes of motion simultaneously with a high level of sophistication. Motorola’s DSP 56001 is the CPU for PMAC, and it handles all the calculations for 8 axes.
The servo drive used for this application is transistor controlled PWM DC servo drive. By employing servo drive we can get effective position control. With this speed can also be controlled from 0.1 rpm to full rated speed.
1.4 Flexibility and Configuration for a task
There are four hardware versions of PMAC: the PMAC-PC, the PMAC-Lite, the PMAC-VME, and the PMAC-STD. These cards differ from each other in their form factor, the nature of the bus interface, and in the availability of certain I/O ports. All versions of the card have identical on-board firmware, so PMAC programs written for one version will run on any other version. As a general-purpose controller, PMAC can serve in a wide variety of applications.
PMAC is configured for a particular application by the choice of the hardware set(through options and accessories), configuration of parameters, and the writing of motion and PLC programs. Each PMAC possess firmware capable of controlling eight axes. The eight axes can be all associated together for completely coordinated motion; each axis can be put in its own coordinate system for eight completely independent operations. The PMAC CPU communicates with the axes through specially designed custom gate array ICs, refered to as “DSPGATES”. Each of these ICs can handle four analog output channels, four encoders as input, and four analog-derived inputs from accessories board.Upto 16 PMAC may be ganged together with complete synchronization, for a total of 128axes.
1.6 PMAC is a Computer
It is important to note that PMAC is a full computer in its own right, capable of standalone operation with its own stored programs. Furthermore, it is a real-time, multitasking computer that can prioritize tasks and have the higher priority tasks pre-empt those of lower priority (most personal computers are not capable of this). Even when used with a host computer, the communications should be thought of as those from one computer to another, not as computer to peripheral. In these applications , the ability to run multiple tasks simultaneously,properly prioritized can take a tremendous burden off the host computer (and its programmer!), both in terms of time, and of task-switching complexity.
CHAPTER 2 : BACKGROUND STUDY
2.1 Computer Numerical control (CNC)
The abbreviation CNC stands for Computer(ized) Numerical(ly) Control(led), and refers specifically to the computer control of machine tools for the purpose of (repeatedly) manufacturing complex parts in metal as well as other materials, using a program. CNC was developed in the late 1940s and early 1950s. CNC machines were relatively briefly preceded by the less advanced NC, or Numerically Controlled machines.
2.1.1 Numerical Control (NC)
Numerical control or numerically controlled (NC) machine tools are machines that are automatically operated by commands that are received by their processing units. NC machines were first developed soon after World War II and made it possible for large quantities of the desired components to be very precisely and efficiently produced in a reliable repetitive manner.
Numerical Control (NC) was the precursor of today's Computer Numerical Control (CNC), which controls the automation of machine tools and the inherent tool processes for which they are designed. The CNC machine tool is the servo actuator of the CAD/CAM (Computer Assisted Design/Computer Assisted Manufacturing) technology both literally and figuratively. CNC inherits from NC the essential character of by-the-numbers interpolation of transition points in the work envelope of a mult-axis motion platform, based on the separation of programming from operations. Once stored in the CNC memory and selected, the program is executed by pressing the appropriate key on the machine operator panel.
The axes movements of all CNC machines are controlled in closed loop. Closed loop provides position control with feedback. Feedback minimizes the difference between commanded position and the actual position and also the commanded velocity to the actual velocity
A closed loop motion –control system consists of a controller (the CNC System), an amplifier to drive motor, a motor an transducer that monitors the motion. The position loop terminates onto the CNC System and the CNC System generates the Analog command voltage to the amplifier. The velocity loop terminates in the driver amplifier.