罗克韦尔自动化

1. Introduction
　　
    Based on DSP technology speed sensorless vector control system is accomplished and the drive is directly accessed to Internet by means of the embedded Internet technology to complete remote control. In combination with the above functions this is my paper thesis.

2. System Structure & Function
   
    As a control mode of AC induction motor, vector control technology is the first scheme of advanced performance frequency conversion timing system. Based on mathematics model of induction motor, this technology decomposes magnetic flux current and torque current of motor winding coupling together in the selected coordinates system, and controls magnetic flux and torque separately in order to make the induction motor approach DC motor’s characteristic.

    TMS320F240 which is our drive core option, is a low price and high performance 16 bit DSP in 1997 from TI corporation of USA. It is a flash EEPROM specially designed digital motor control. It not only has high performance CPU core deployed with high speed digital signal processor, but has the peripheral device function just as single chip motor control. Combined with high speed operation function of digital signal processor and powerful control capability oriented motor, it is a desired substitute of traditional multi microprocessor unit (MCU) and multi-chip design system.

    Fig. 1 shows the schematic diagram of speed sensorless vector control system based DSP TMS320F240. The system makes up of main circuit, control circuit and assistant circuit. Adopting 6-cubes encapsulation power module IGBT the main circuit performs power transform. As TMS320F240 the core, the control circuit is used to complete these functions such as vector control core algorithm, PWM generator, rotor speed estimate algorithm, IP module communication program and keypad panel etc. Other available optional circuit is composed of power supply, drive circuit, IP module circuit, current and voltage detection circuit to realize these functions such as providing multi DC power supply to the system and isolation drive of IGBT etc. Key features include:

i. Current output detection
   
    When detecting two phrase currentandfrom three phrases by using magnetic balanced current sensor, calculate the third phrase currentto acquire real-time current output information, i.e. the motor’s stator current information, providing real-time signal for vector counting and system protection.

ii. Speed estimate

    Speed sensorless vector control system needs not any speed sensor. It uses stator voltage, stator current easy to measure and motor parameter to estimate rotor speed. Under compensating rotor’s whole magnetic chain, the speed value is estimated by adopting torque current feedback method in F240 to form closed-loop rotate speed and field-oriented vector.
iii. PWM output

    PWM circuit of TMS320F240 can generate 6 routes PWM signal with programmable dead section and changeable output polar. After isolation drive unit EXB840, the signals control the main circuit’s IGBT to realize inverted output.
iv. System software design

    The system software is composed of main program and PWM interrupt subprogram. The main program accomplishes system initialization, stop, run, program mode etc. The current loop’s coordinates transform, PWM signal’s generator and speed sampling program are achieved in the interrupt subprogram, see Fig. 2. So this can not only ensure speed control precision, but shorten interrupt time greatly, improving switch frequency to make system switch frequency reach 16kHz. 

Fig. 2   The Architecture Diagram of System Software