the shape of sound to come: Project: A real time closed loop control system and target identification through Ethernet. Design and implementation.

Place of Development: École Nationale Supérieure d'Ingénieurs de Caen- France
Date: September 2012
Duration: 9 days
Author: Pablo Manuel Delgado et al.

Further reading on J3eA , Volume 12 (2013) (French): http://www.j3ea.org/articles/j3ea/abs/2013/01/j3ea13011/j3ea13011.html

This intensive project took place on the laboratories of ENSICAEN's Signal, Control, Telecommunications and Embedded Systems specialization (SATE) and it comprised several phases distributed in nine full days of work.
The goal was to implement a closed loop control system on a direct current motor whose parameters were passed in real time through Ethernet, in a few longer than a week's time. A group of six people was assigned for this task.

The system specifications:

A real time control algorithm (and a prior system parameter identification) to be run on a PC, the processed data must be transmitted to a microcontroller through Ethernet, which in turn controls the current motor by a PWM output.
A human-machine graphical interface with all the necessary commands to run the control program.
The processing paradigm on the micro controller must be real time i.e. preemptive task scheduling.

Technological constraints:

The microcontroller (MCU) has to be a PIC32MX795F512L from Microchip, due to availability reasons.
The program was developed on IDE MPLAB with a C 32 toolchain.
The speed measurements are made with an ADC7634 Analog to Digital Converter from Analog Devices linked to the MCU through SPI in order to minimize the final PCB layout.
The control signal generation is made through a PWM module embedded in the microcontroller. Signal filtering is performed to adapt the controlled system's input requirements. The slow dynamics and noise immunity of the system allow such solution.
The PC-MCU communication will be implemented on the TCP/IP protocol.

Technical Specifications:

PIC32MX795F512L

TQFP 100 pin package
Core working frequency: 80 MHz
Peripheral reference working frequency: 40 or 80MHz
Used peripherals set optimization

ADC AD7634

Sampling frequency: 2 KHz
Bit depth: 18 bits
Input dynamic range: +/- 10 V (unipolar power supply)
SPI digital interface for configuration and data communication
Physical configuration of the ADC's parameters is possible

PWM Signal Conditioning Circuit

PWM switching frequency at 2KHz and a 3,3V peak to peak amplitude
Second order Low Pass Filter with a 200 Hz cutting frequency with unity gain on the passband. Its purpose is to reject the PWM signal's higher order harmonics.
Adjustable gain for a correct utilization of the motor's control input dynamic range

PC to MCU link

TCP/IP protocol. TCP and UDP connection options must be available due to different requierements on the system control parameters' reaction speed.
Dynamic IP (DHCP) implementation to ensure greater portability and configuration.