In the industrial process control system, the electric actuator can be the received control signal (4 ~ 20mA current signal or a voltage signal of the 1-5V or 1-10V) is converted into the angular displacement of the output shaft, and linear displacement to thereby control the position of the valve [1]. Traditional electric actuator controller to drive through the SCR AC motor, due to the characteristics of the AC motor braking inertia caused by poor control precision, while driven by the high torque motor volume large, it is difficult for speed adjustment. With the development and application of electronic circuits and LSI, the emergence of a variety of high-performance electronic devices and microprocessor, while in recent years, motor brushless DC motor control theory and the rapid development of the rare earth permanent magnet materials such its volume Small, high reliability and large output torque, etc., so the brushless DC motor in many areas applications [2].
Using ARM core LPC2132 [3] and the selection of a brushless DC motor to drive the executing agency, while using C8051F410 [4] to high-precision signal acquisition. The system uses a combination of hardware filtering and digital filtering technology to greatly improve the accuracy of the input signal and the feedback signal acquisition, through the chip LPC2132 to control a brushless DC motor to achieve the speed of adjustment, while the operation of the actuator position to achieve the digitized positioning.
The ARM (AdvancedRISCMachine) is the name of the company to design this processor core. ARM core chip. And other components, such as RAM, ROM, and the on-chip peripherals, come together to constitute the real chip. ARM microprocessor generic term as a class, as a low-power, high-performance 32-bit embedded microprocessors, has been widely used in various fields
The selection ARM chip LPC2132 is based on the one to support real-time simulation and track 16/32 ARMTTDMI-SCPU, with 64KB embedded high-speed Flash memory. A 128-bit wide memory interface and a unique accelerator architecture 32-bit code to be run at maximum clock rate. It has a very low power consumption, more than one 32-bit timer, 2-channel 10-bit ADC, PWM channels and up to nine external interrupt and 47 GPIO they are widely used in automotive, industrial control and other fields.
The control system uses the LPC2132 chip and digitization methods to control electric actuators run. Allows the operator panel buttons and LCD menu, the settings of the various parameters can either be done in the field. The controller can be set in advance Pneumatic control valve hysteresis, speed and stroke parameters, acceptance of the valve opening degree of the given signal C8051F410 transmitted collected.
Valve during the movement, the controller in real time to the setting signal and the feedback signal, when the input and output within a certain range when the motor is stopped. Collected by LPC2132 timely Hall signal, to calculate the speed of the motor by measuring the pulse width of the Hall, the acquisition speed is compared with a set speed value, the value of the real-time adjustment of the PWM to achieve the purpose of controlling the speed. System Principle
The realization of the system
Hardware circuit design
The system uses dual MCU structure, the main circuit is composed of two parts: First, the brushless DC motor Hall acquisition circuit and driver circuit; signal acquisition circuit. C8051F410's ADC module potentiometer position feedback signal and the control signal sent by the remote (such as 4-20MA) is converted into a digital signal; transmit data through the serial port to the the lpc2132 main controller, dual processor between photoelectric The isolation circuit enhances the anti-interference ability of the system. In the present system, the position detection is the key to the position control, it is not only able to provide to the controller the current state of the motor, but also to reflect the speed of rotation of the motor. To achieve better accuracy and practical application, to avoid interference, the position signal is collected only when power-on initialization, so the first determined location. The position signal is converted to a motor current pulse count.
The LM2575 output 5V power conversion module, the drive power FET IRF3205 tube PWM principle 39V high pressure. Hall signal collected 74HC14 chip, three signal connection LPC2132 the P0.27, P0.28, P0.29 the mouth, P0.27 pin is set to capture and generate an interrupt to a pulse in two counts between interrupts. Can be obtained by calculating the timer value of the motor speed. P2.5 port design take C8015F410 measuring input signal, feedback with P0.26 mouth of measuring the voltage value of the potentiometer. Measuring circuit shall be as close as possible to the C8051F410 the I / O ports can reduce interference. Get the LPC2132 sent to the percentage of feedback output through the serial port, the the use C8051F410 PWM pin through the optocoupler control feedback output 4 ~ 20MA.
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