Natural gas engine control system based on DSP chip TMS320LF2407

1 Introduction

In recent years, digital signal processor (DSP ) chips have been widely used in the fields of automatic control, image processing, communication technology, network equipment, instrumentation and home appliances; DSP provides an efficient and reliable hardware foundation for digital signal processing. At present, the most widely used DSP chip is the product of TI (Texas Instruments), and the TMS320C2000 series is a DSP suitable for digital control. This series of DSP chips has perfect performance and integrates flash memory, high-speed A/D converter, high-performance CAN module, etc., so it can reduce development difficulty, shorten product development time, and effectively reduce development cost. The price/performance ratio. The TMS320LF2407 chip is the latest, most integrated and highest performance motion control DSP chip in the TMS320C2000 series.

Natural gas as a power source is an ideal substitute for traditional fuels. Dedicated electronic control systems for various natural gas engines are constantly emerging, and the performance of natural gas engines such as power, economy, and emissions is continuously improved. The natural gas-specific engine can have lower emissions than the equivalent gasoline engine and diesel engine through good control, and the power performance is greatly improved. Therefore, it is very important to design a natural gas engine control system by using a high-performance DSP chip.

2 TMS320LF2407 chip introduction

The DSP chip is a microprocessor with a special structure. The chip's internal Harvard architecture with separate programs and data, with a dedicated hardware multiplier, extensive pipeline operation, provides special instructions that can be used to quickly implement a variety of digital signal processing algorithms.

The TMS320x24x family of digital signal processors is a new programmable DSP chip developed by TI (Texas Instruments, USA) for digital motor control, embedded control systems and digital control systems. The TMS320LF240x is a new addition to the x24x family of DSP controllers designed to meet control applications. The on-chip program memory of the LF240x is Flash EEPROM, including the LF2402, LF2406 and LF2407 models. The LF2407 is a x240x series DSP controller* with the strongest and most complete on-chip facilities. It is widely used in code development, system simulation and practical systems. Its main features:

(1) Using high-performance static CMOS technology, the supply voltage is reduced to 3.3V, reducing the power consumption of the controller; the execution speed of 30MIPS shortens the instruction cycle to 33ns (30MHz), thereby improving the real-time control capability of the controller. .

(2) Two event manager modules EVA and EVB, each including: two 16-bit general purpose timers; eight 16-bit pulse width modulation (PWM) channels. Suitable for controlling AC induction motors, brushless DC motors, stepper motors and inverters.

(3) The 10-bit A/D converter has a minimum conversion time of 500 ns. It is optional to have two event managers to trigger two 8-channel input A/D converters or one 16-bit channel input A/D converter.

3 TMS320LF2407 chip in natural gas engine control system

The traditional control system is controlled by single-chip microcomputer. First, its running speed is not high, it can not achieve good real-time control, and can not effectively achieve the effect of online detection and control. Second, the integration degree of single-chip microcomputer is low, and there is no on-chip. The dedicated peripherals required by the motion control system require more components, increasing the complexity of the system circuitry and reducing the reliability of the system. However, TI (Texas Instruments)'s x240x series DSP chips are used, and dedicated motion control peripheral circuits are integrated on-chip, and its internal DSP core can provide higher computing speed, operational precision and the ability to process large amounts of data operations. The DSP chip can better meet the real-time requirements of the system and can easily implement complex control algorithms.

3.1 hardware design of the control system

The main function of the control system is to control the ignition time of each cylinder through two speed sensors and one temperature sensor, one speed sensor is measured, the other speed sensor measures the signal to calculate the speed, and the temperature sensor measures the temperature of the exhaust gas. The measured engine speed is determined by the measured speed and exhaust gas temperature, and the solenoid valve is adjusted according to some control rules to control the intake air volume of the natural gas and the air, so that the engine speed is constant to improve the dynamic performance of the natural gas engine.

The control system uses the DSP chip of TMS320LF2407. The peripheral components of the system are few and the circuit structure is very simple. The schematic diagram of the system structure is shown in Figure 1:

Figure 1 system structure diagram