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DSP + CPLD-based control system of induction motor Design development platform

In Electronic Infomation Category: D | on April 20,2011

With the power electronics, motor control theory and MC34166T datasheet and the continuous development of micro-controllers, the modern AC variable speed in the national economy has been widely used. Currently, high-performance speed control strategy and MC34166T price and modern control theory has been progressively applied to the field of AC motor control, general motion control system can not meet high-performance speed control requirements, and MC34166T suppliers and establish a core DSP + CPLD to control the development of induction motor control system platform, high-performance motion control strategy for the study of great significance. It not only can reduce system size and complexity of real-time control can improve the system computing power, this development platform to facilitate users to quickly complete motor control system product development and applications.

1 overall design of the hardware development platform

1.1 development platform, the overall design and features

The development platform as a three-phase asynchronous motor controlled object to the controller TMS320F2812 and complex programmable logic device CPLD as the control, the main circuit is a typical AC - DC - AC voltage source inverter circuit, the diode constitute a three-phase bridge rectifier circuit, the filtered DC voltage obtained by the intelligent power module (IPM) as the main inverter switching devices, the output frequency and voltage of a certain three-phase AC induction motor to power.

DSP chip has a wealth of resources and efficient data processing, run faster, so fast with the requirements of the external parts are also high. If the external components using a dedicated circuit control, not only on the DSP extensions for more features, and can reduce system complexity, increase system control precision.

Complex programmable logic device has a wealth of logic resources, but also for completion of various algorithms and combinatorial logic. With I / O ports and more flexible design, scale and speed, the advantages of the logic processing power, if a separate form with its variable speed system, the development cycle is long and expensive. Alteras MAX IIZ CPLD has several key advantages. Achieved in a single device advanced features and zero power consumption. Both in the advanced system features beyond the traditional macrocell CPLD, these features include user flash memory, internal oscillator, cost optimization, greater density, smaller packages and lower power consumption. For these reasons, and considering the system and the subsequent development of the universal realization of different control schemes, the control circuit to DSP + CPLD as the control, the use of

TMS320F2812 chip complex induction motor control algorithm, CPLD logic control to achieve the external circuit. Not only meet the performance requirements for system control, and reduce the burden of DSP processing, so you can concentrate on DSP control algorithm, simplifying the logic circuit to improve the reliability of the motor.

TMS320F2812 + CPLD-based control system of induction motor development platform for hardware principle, shown in Figure 1.

Figure 1, the hardware design structure development platform

Compared with ordinary control system, the control system development platform has the following characteristics:

(1) DSP and CPLD coordinated control, can play their respective advantages, to achieve high-performance motor speed control.

(2) DSP, complex programmable logic devices has constituted more intelligent motor control system development.

(3) of the control system control scheme and flexible development platform, programmable strong, reserved port rich, easy to expand, not only can the control of induction motors can also be reached on other high-performance motor control, system upgrade easy maintenance and good.

(4) use of the control system development platform, can shorten the product development cycle, reduce development costs and improve development efficiency, and can be completed in a short time motor control system product development and applications.

(5) of the control system development platform for the control circuit switch in the form of the output signal through the optical isolators are the main circuit interface with the system to ensure the strength of electrical isolation, high stability of the system can meet the high motor control system reliability requirements.

1.2 of the module circuit design

1.2.1 Main Circuit

Main circuit is a typical AC - DC - AC voltage source inverter circuit, through the three-phase non-controlled rectifier to the inverter and switching power supply. Smart power module (IPM) as the main inverter switching devices, and its external components, simple structure and high reliability. Equipped with comprehensive protection measures to ensure system reliability.

(1) inverter circuits.

Development platform for the typical three phase inverter circuit - DC - AC voltage source inverter circuit, the use of Mitsubishi Intelligent Power Module (IPM) PM50RL1A120, the voltage 1200 V, rated current 50 A, 6 way internal integration high-speed, low power composed of Three Phase IGBT bridge and all the way for the braking IGBT, as well as over voltage, over current and overheating fault detection and protection circuit, and detection signal to the DSP to interrupt handling. After the controller output signals are opto isolated circuit into the IPM, the system effectively suppress interference.

(2) voltage and current detection circuit.

DC in the inverter circuit and the output of the AC side of the design of the voltage and current detection circuit, through the Hall voltage and current sensors to obtain voltage and current signals, the isolation amplifier evacuation through the ADC DSP module, the A / D conversion, in order to achieve closed-loop control system. Occurred when the system current, over voltage, the circuit will be low-level signals can be quickly sent to the DSPs PDPINT protect the pin block PWM pulse output, to avoid system failure.

1.2.2 Control circuit

Control system development platform is mainly used to complete a variety of complex control algorithm for induction motor drive, motor control system to accelerate product development and applications. DSP contact with the external circuit can be completely controlled through the CPLD, DSP and CPLD way by bus to communicate. CPLD DSP chip as a system extension, to complete a number of logic control and I / O expansion task. CPLD can be configured to function with the address decoder, based on the address of DSP output signals, decode them, through the address bus input CPID, strobe the external circuit to be controlled, and the SRAM can be achieved, and LED, IED to read and write signal control.

TMS320F2812 is TIs latest 32-bit fixed point DSP controller, a modified Harvard architecture, with high-speed data processing capabilities. The chip has a wealth of integrated motion control specific peripherals: PWM generation circuit, SVPWM state machine, programmable dead zone, compare / capture unit and so on. Other peripheral functions: A / D conversion unit, SCI, SPI, CAN controller, suitable for use in the field of high-precision servo control.

Alteras MAX IIZ family EPM57OZM144C7N by MBGA package, 144 pins and 116 available to the user I / O port, typically equivalent to 440 macrocells, DSP match the voltage and the chip also provides a JTAG interface, ISP can be programmed, the logic processing power, the external logic circuits can be simplified.

(1) power module.

TMS320F2812 dual power supply, the system would let all of +3.3 V for I / O power, and then connected to 1.9 V core power supply. Power requirements for this, the choice of TIs dual-power supply provided to the DSP chip TPS767D301 power, the chip is dual-output, all the way to a constant output voltage of 3.3 V, adjustable output voltage of the other, to achieve timing requirements for DSP power supply . By TPS3823S chip power monitoring and manual / automatic reset, run the monitoring program to prevent the program into an endless loop. TPS767D301 level output circuit shown in Figure 2.

Figure 2 TPS767D301 level output circuit

1OUT = (1 + R1/R2), 2OUT = 3.3 V. Where, VREF = 1.183 4 V. Select the appropriate resistance value R1 and R2, can be adjustable voltage.

(2) memory modules.

Completion of system development platform, a variety of different control strategies and data processing algorithms, will produce a lot of temporary data, if only by the DSP on-chip RAM commitments will add to the burden of DSP, making system control precision of lower limit integrity of the system running. To meet the data storage needs expand a model IS61LV516 the SARAM, generated by CPLD chip select address decoding signal, you can specify it as a program memory or data memory.

(3) CPLD module.

CPLD development platform in the play the role of logic control. Can be: 1) QEP signal processing, position sensors provide input for the speed of the speed of position signal, DSP gives the PWM pulse width modulation signal, the output for the IGBT drive module control signals, the optocoupler isolated circuit into the IPM. Quadrature encoder to the motor position detected speed signal sent to the DSP, through its internal QEP circuit to the motor speed and direction, to achieve the systems feedback control and PWM control signal output to achieve the speed closed-loop control. 2) address decoding, the output of the DSP address signals address decoder, to achieve expansion of F2812-chip peripheral chip select function, gating the corresponding peripheral chips mapped to the F2812 memory. 3) DSPs I / O expansion, if the system simultaneously control multiple motors, DSPs own I / O pins can not meet the requirements, need to extend through the CPLD. CPLD on the other motor quadrature encoder signals are processed to complete the orthogonal signal frequency, pulse count, while the output counting results, as the motor speed and position for judging.

(4) display module.

To protect system reliability, the co-ordination through the DSP and CPLD design with LCD liquid crystal display interface circuit, control, LCD display and LED indicators show the system to achieve man-machine interface, making the system has good people machine interface. LCD module who use Sun Electronics Co., Ltd. Changsha SMG12864ZK standard point of formation of Chinese characters and graphics LCD modules, can display 128 64 dot matrix or 8 characters 4 lines, DSP and the LCD interface circuit between the Figure 3 .

Figure 3 DSP with LCD interface circuit between the

LCD reset signal / RST and the chip select signal RS by the DSP control signals generated by CPLD, after decoding the data lines. DB [0] ~ DB [7] by the TMS320F2812 data lines DATA [0] ~ DATA [7] through the CPLD bus driver by two-way, other signals corresponding to the same name connected.

(5) protection module.

Protection module is the system power up / down or the case of failure to provide timely blocking signals, to ensure safe and reliable system to work. The development platform has a bus over-voltage protection circuit protection, overcurrent protection, motor overheat, IPM Fault signal processing functions. System protection signal can also be integrated into the CPLD logic, when a fault occurs, you can quickly cut off the CPLD in the real-time PWM output.

Meanwhile, in order to make the application of the hardware system was extended outside the asynchronous motor is designed addition to the different motor and different control strategies may be used in signal acquisition circuit, and position feedback devices that use different interface circuit.

2 pieces of the overall development of platform software design

Development platform for software development and debugging DSP at TI, under the integrated development environment CCSC2000. With C language programming of the control system software. The modular design makes easy and flexible programming and the use of both. Using this control system development platform, software programming, can easily achieve vector control induction motor, direct torque control, the control algorithm.

CPLD development tools for the Max PlusII software, VHDL programming, according to the specified fuse pin configuration files automatically after download of the CPLD device programming. Each module within the program of work according to strict timing, but they parallel each module to complete the different actions.

System control program is divided into two parts, namely the main program and interrupt service routine. After the main program is initialized into the circulation. Interrupt service order process to complete the system mainly various control strategies, including the stator current and voltage sampling, complete the current, voltage A / D conversion. Orthogonal encoding unit processing speed feedback signal. According to the output PWM signal of various control algorithms to control the motor torque. System main program flow chart shown in Figure 4.

system main program flow chart in Figure 4

3 Conclusion

DSP CPLD with built motor development platform, suitable for induction motor control algorithm, the DSP as the main controller, CPLD Accessibility expanded development platform makes the whole control system has strong expansion capabilities and greater flexibility not only cost savings, reducing the system development cycle, and improve development performance.

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