Implementation Of Dsp Based Cnc Machine Computer Science Essay

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Digital signal processing uses special dedicated processors to convert and interpret digital signals at very high speeds. Digital Signal processing technology is enabling cost effective and energy efficient control system design. The performance of a DSP Architecture allows an intelligent approach to reduce the complete system costs of digital motion control applications

using cheaper electrical motors, fewer sensors, and smaller sizes of EMI filters. To provide also a cost optimal solution Texas Instruments (TI") developed a single chip solution combining the features of a Micro controller and the performance advantages of a DSP core. This new - so-called "DSP-Controller" delivers the real-time MIPS and the tightly integrated peripherals to implement optimal control algorithms with no cost penalty.

The incredible power of DSP for specific tasks is illustrated by the fact that a DSP chip can execute a multiply-accumulate (MAC) instruction, a fundamental operation, in a single clock

cycle. This same operation on a current Pentium processor chip takes 11 clock cycles. Obviously a 120-MHz Pentium will still take nearly four times as long as a 40-MHz DSP processor.

This paper deals with the new DSP-Controller and its low speed & high speed interfacing applications.

INTRODUCTION:

There are many varieties of DSP and those choices give control builders choices in their priorities for control functions. The variety of DSP available means that you as a user can obtain different control performance, functions and capabilities to meet your specific needs.DSP's speed allows better accuracy and speed, yet is gentler on the machines it controls. What

can a high-speed control do for you?

In simple terms, it gives you the ability to finish one task faster and movealong to the next sooner. The combination of fast block transfer time with a still faster servo cycle time ensures high data throughput, with optimal accuracy. In a broader sense, high speed creates many other benefits. Improved accuracy, fit, finish and cutter life are the most commonly reported peripheral benefits. Customers share the benefits of high speed through the entire manufacturing process, not just to produce more work in less time, but also improving the accuracy and finish and reducing polishing and fitting time. They do this by using the high speed to reduce the step over and the tolerances. Tools simply last longer because their chip load is much more consistent. The TMS320X28x DSP includes the same advantages as the micro controller but also offers higher speed, higher resolution, and capabilities to implement the math-intensive algorithms to lower the system cost. The high speed is attributable mainly to the dual bus of the Harvard architecture as well as single-cycle multiplication and addition instructions. One bus is used for data and the other is used for program instructions. This saves time because each is utilized simultaneously. Traditionally, cost has been a potential disadvantage of the DSP solution, but this aspect has

diminished with the continuing decline of DSP costs. DSP controllers enable enhanced, real-time algorithms as well as sensor less control. The combination reduces the number of components and optimizes the design of silicon to achieve a system cost reduction. DSP are capable of processing data at much faster rates than micro controllers. For example, the speed of the DSP allows it to estimate motor velocity, a task accomplished by a tachometer in analog and micro controller systems.

TI TMS320x28x DSP Family _ the first single-chip DSP solution for the digital control system market

Features:

High-Performance Static CMOS Tech 150 MHz (6.67-ns Cycle Time) Low-Power (1.8-V Core, 3.3-V0) 3.3-V Flash Programming Voltage" JTAG Boundary Scan Support "High-Performance 32-Bit CPU (TMS320x28x) 16x16 and 32 x 32 MAC Operations 16 x 16 Dual MAC Harvard Bus Architecture Fast Interrupt Response and Processing, Unified Memory Programming Model, Code-Efficient (in C/C++ and Assembly TMS320F24x/LF240x Processor Source Code Compatible " On-Chip Memory Up to 128K x 16 Flash 1K x 16 OTP ROM.

Single-Access RAM (SARAM)

Boot ROM (4K x 16)

External Interface Up to 1M Memory

Clock and System Control Dynamic PLL Ratio Changes Supported

Motor Control Peripherals

Serial Port Peripherals Serial Peripheral Interface (SPI)

Two Serial Communications

Interfaces,(SCIs), Standard UART, Enhanced Controller Area Network (eCAN)

Multichannel Buffered Serial Port (Mc BSP) With SPI Mode 12-Bit ADC, 16 Channels

Up to 56 Individually Programmable,

Multiplexed General-Purpose Input / Output (GPIO) Pins

High speed peripheral interfacing:

In AC servo drives, DSP are used for vector control of AC motors. AC drives have complex control structures because of the cross coupling of the three-phase currents. Vector rotation techniques transform three-phase axes into rotating two-phase dq axes. This two-phase rotation technique greatly simplifies the analysis, making it equivalent to analyzing field-wound DC motors. In UPSs and power converters, DSP are used for PWM generation as well as power factor correction and harmonic elimination. Advanced mathematical techniques can be used to control the firing angles of the inverters, creating low-harmonic PWM with unity power factors.

Three classical motors are among the existing electric motors on the market:

1. DC with commutators (wound field)

2. Synchronous AC motor

3. Asynchronous AC motor

When properly controlled, these classical motors produce constant instantaneous torque (very little torque ripple) and operate from pure DC or AC sine wave supplies. Unlike DC motors, the use of which is leveling off and even declining each year, the use of AC motors is increasing each year. A couple of reasons for this increase are possible: AC motors cost less than DC motors and, AC motors can be controlled more easily using digital control (especially DSP). For example, brush less permanent magnet synchronous motors (PMSM) includes a vector control approach in which matrix and vectors represent the control quantities. Using a MAC

calculation unit included with the TMS320x28x DSP provides

the following advantages:

1. Full motor torque capability at low speed

2. Better dynamic behavior

Using the TMS320x28X DSP Controller for Optimal Digital Control

Higher efficiency for each operation point in a wide speed range

Decoupled control of torque and flux

3. Short term overload capability

4. Four quadrant operation

Sensoring or sensor less algorithms can also be implemented with DSP_s. The most common way to sense motor speed on the shaft is to use an incremental encoder. The TMS320C240 includes a module, the quadrature encoder pulse (QEP), that handles the Situation perfectly, calculating the speed and direction of the rotation using only two digital inputs and a 16- or 32-bit internal timer register. In some applications emphasizing efficiency, cost, reliability, and mechanics, it is not possible to use a speed, position, or Hall (commutation signals) sensor.

Low speed peripheral interfacing:

The 320x240 Graphics display S1D13305 series interface operates at with crystal frequency of 10 MHz, While the DSP Processor operates at 150MHz.From the timing diagram of Graphics Display shown below, it is clear that for execution of each command at least one cycle time tCYC =440ns is required, hence it can not be operated with suchhigh speed processor Where tCYC =2tC +tCC+ tCEA .For TMS320x28X DSP the oscillator input range is 20 MHz to 3.5MHz.The PLL has a 4-bit ratio control to select different CPU clock rates. The PLLCR bits [3:0] set the clocking ratio

How to write .BMP image on graphics display?

Bmp file cannot be directlywritten on graphics display. Bmp to text converter software is used for the conversion. The data obtained after conversion is in vertical format, while it should be in horizontal format for graphics display, so again conversion software is added for the same & then the data is displayed.

CAN communication:

You can throw away the wiring loom _ and replace it with two wires! Smart gauges and sensors can be directly connected to the CAN bus. Control modules can read/send data, display systems can read/log data and because it is a network, it is irrelevant where components are physically located. Information display panels show the driver/operator

what he needs to know. Logging of information feeds the service system and panels display information where required. CAN bus also have the bandwidth to cope with real-time

control as well as data collection International Conference on Systemics, Cybernetics and Informatics.

Interfacing flowchart for graphics display with DSP is as given

below.

]

Implementation of DSP Based CNC Machine supporting Card for interfacing high & low speed peripherals.

The analog input to the converter is provided via four channel multiplexer. A unique configuration of low on-resistance switches allows an unselected ADC input channel to provide power and an accompanying pin to provide ground for an external device. By maintaining a differential input to the converter and a differential reference architecture, it is possible to negate the switchs on-resistance error .

The ADS7843 is a classic Successive Approximation Register SAR) ADC. The architecture is based on capacitive redistribution which inherently includes a sample-and-hold function. The converter is fabricated on a 0.6µs CMOS process. The basic operation of the ADS7843 is shown in above Figure The device requires an external reference and an external clock. It operates from a single supply of 2.7V to 5.25V. The external reference can be any voltage between 1V and +VCC. The value of the reference voltage directly sets the input range of the converter. The average reference input current depends on the conversion rate of the ADS7843.

40

Block digram eZdspTM F2812

Emulator:

The software developed is first checked with emulator kit eZdspTM F2812. The eZdspTM F2812 is a stand-alone card--allowing evaluators to examine the TMS320F2812 digital signal processor (DSP) to determine if it meets their application requirements. Furthermore, the module is an excellent platform to develop and run software for the TMS320F2812 processor. The eZdspTM F2812 is shipped with a TMS320F2812 DSP.

The eZdspTM F2812 allows full speed verification of F2812 code. Two expansion

connectors are provided for any necessary evaluation circuitry not provided on the as shipped configuration. To simplify code development and shorten debugging time, a C2000 Tools Composer driver is provided. In addition, an onboard JTAG connector provides interface to emulators, operating with other debuggers to provide assembly language and _C_ high level language

Implementation of DSP Based CNC Machine supporting Card for interfacing high & low speed

Peripherals.

Fig. Photograph of CNC machine supporting card system

Summary

This application report presents new controller architecture: the DSP controller and its single chip solutions for the control Applications. The TI TMS320x28x DSP controller combines the performance of DSP architecture with the optimized peripherals of a micro controller. With this DSP controller, an intelligent control and sensor less approach become possible. In addition, the System cost will be reduced and the reliability of the entire system will be improved & with the feature of programmable clock it is possible to interface high as well as low speed peripherals

with the same DSP with maximum efficiency.

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