Hardware and electrical design of intelligent QT electric actuator

在工业控制系统中，电动执行器是电动单元组合仪表中一个很重要的执行单元。它由控制电路和执行机构两个在电路上*独立的部分组成，可接收来自调节器的电控信号，将其线性地转换成机械转角或直线位移，用来操纵风门、挡板、阀门等调节机构，以实现自动控制。近年来，随着微电子技术和控制技术的迅速发展，电动执行器也获得了快速发展，特别是国外一些生产厂商在这几年中相继推出了常规的、带现场总线通信协议的智能电动执行器，而智能QT电动执行器就是有发展潜力的一种。
In the industrial control system, the electric actuator is a very important execution unit in the electric unit combination meter. It consists of two parts of the control circuit and the actuator that are completely independent on the circuit. It can receive the electronic control signal from the regulator and convert it linearly into a mechanical rotation angle or a linear displacement. It is used to control dampers, baffles, valves, etc. Adjust the mechanism to achieve automatic control. In recent years, with the rapid development of microelectronics technology and control technology, electric actuators have also achieved rapid development. In particular, some foreign manufacturers have successively introduced conventional intelligent electric actuators with fieldbus communication protocols in recent years. , and QT smart electric actuator is one of the most potential development.

本文介绍的智能QT电动执行器采用无刷直流电机控制，控制精度高，实现了数字化的阀位检测，可提高阀位测量的精度和可靠性，能取代现行普遍采用的电位器和差动变压器模拟测量方法。
The QT intelligent electric actuator introduced in this article adopts brushless DC motor control with high control precision, realizing digital valve position detection, improving the accuracy and reliability of valve position measurement, and replacing the commonly used potentiometers and differential transformers.

控制电路的硬件设计
Control circuit hardware design

整个电路主要由五个部分组成：单片机P89C58为主的主机部分，由SJA1000、82C250、光电隔离电路等组成的QT总线控制及接口部分，由无刷直流电机控制芯片MC33035组成的电机控制部分，阀门位置检测部分和LCD液晶显示部分。 1 QT总线及接口部分 QT总线控制及接口如图2所示，主要包括独立QT通信控制器SJA1000、QT总线收发器82C250和高速光电耦合器6N137。 单片机P89C58首先对SJA1000进行初始化，控制SJA1000实现数据的通信任务。SJA1000的AD0～AD7连接到89C52的P0口，CS连接到89C52的P2.0口，其余的引脚分别对应相连。 　
The entire circuit is mainly composed of five parts: the main part of the MCU P89C58, the QT bus control and interface part composed of SJA1000, 82C250, opto-isolation circuits, etc. The motor control part composed of the brushless DC motor special control chip MC33035. Valve position detection section and LCD liquid crystal display section. 1 QT bus and interface part QT bus control and interface are shown in Figure 2. They mainly include independent QT communication controller SJA1000, QT bus transceiver 82C250 and high-speed optocoupler 6N137. The one-chip computer P89C58 initializes SJA1000 at first, controls SJA1000 to realize the data communication task. The AD0 to AD7 of the SJA1000 are connected to the P0 port of the 89C52, the CS is connected to the P2.0 port of the 89C52, and the remaining pins are respectively connected.

为了增强QT总线节点的抗*力，SJA1000的TX0和RX0并不是直接与82C250的TXD和RXD相连，而是经高速光耦6N137后再与82C250相连，这样就很好地实现了总线上各QT节点间的电气隔离。82C250与QT总线的接口也采用了一定的安全和抗干扰措施，它的QTH和QTL引脚与QT总线之间各串联一个5Ω的电阻，这样可起到一定的限流作用，保护82C250免受过流的冲击；还可以在QTH和QTL引脚上并联小电容，起到滤除总线上的高频干扰和防电磁辐射的作用。82C250的Rs脚上接有一个斜率电阻，电阻大小可根据总线通信速度适当调整，一般在16～140kΩ之间。
In order to enhance the anti-interference ability of QT bus node, TX0 and RX0 of SJA1000 are not directly connected with TXD and RXD of 82C250, but are connected with 82C250 after high-speed optocoupler 6N137, so that each QT on the bus is well implemented. Electrical isolation between nodes. 82C250 and QT bus interface also uses a certain degree of safety and anti-jamming measures, its QTH and QTL pins and a series of 5Ω resistors between the QT bus, this can play a role in limiting the current, to protect the 82C250 from Overcurrent impact; can also be in parallel on the QTH and QTL pin small capacitors, to filter out the bus on the high-frequency interference and anti-electromagnetic radiation. A slope resistor is connected to the Rs pin of the 82C250. The resistance can be adjusted according to the communication speed of the bus. It is generally between 16 and 140 kΩ.

电机控制电路
Motor control circuit

该电动执行器里电机控制芯片采用了安森美公司开发的高性能第二代单元无刷直流电机控制器MC33035。该控制器内含可用于正确整流时序的转子位置译码器，以及可对传感器的温度进行补偿的参考电平；同时，还具有一个频率可编程的锯齿波振荡器、一个误差信号放大器、一个脉冲调制器比较器、三个集电极开路顶端驱动输出和三个非常适用于驱动功率MOSFET的大电流图腾柱式底部输出器。
The motor control chip in this electric actuator adopts MC33035, a high-performance second-generation unit brushless DC motor controller developed by ON Semiconductor. The controller includes a rotor position decoder that can be used for correct rectification timing, and a reference level that can compensate for the temperature of the sensor; at the same time, it also has a frequency-programmable sawtooth oscillator, an error signal amplifier, and a Pulse modulator comparators, three open-collector top drive outputs and three high-current totem-pole bottom outputs ideal for driving power MOSFETs.
该电机控制电路的功能包括PWM开环速度控制、使能控制和正反转控制。电机的转速控制是利用4-10位译码器/驱动器74LS145的功能，由单片机P89C58给出信号，通过分压电路提供给引脚速度电压来实现的。
The functions of this motor control circuit include PWM open-loop speed control, enable control, and forward/reverse control. The speed control of the motor is to use the function of the 4-10 bit decoder/driver 74LS145. The signal is given by the single-chip microcomputer P89C58, and is provided by the voltage divider circuit to the pin speed voltage.

电机的使能控制和正反转控制信号也由单片机控制，发出电平信号给89C2051，进行电平转换后输出给MC33035相应的管脚来控制电机的工作状态。
The motor's enable control and forward reversal control signals are also controlled by the MCU and send a level signal to the 89C2051. After the level conversion, the output pins are output to the corresponding pin of the MC33035 to control the working state of the motor.

阀门位置检测电路和液晶显示
Valve position detection circuit and liquid crystal display

为了实现阀位的数字化检测，在A/D转换电路中采用了ADI公司的16位∑-△(电荷平衡式)A/D转换器AD7705。AD7705包括由缓冲器和增益可编程放大器(PGA)组成的前端模拟调节电路、∑-△调制器及可编程数字滤波器等，能直接将来自传感器的不同摆幅范围内的信号放大到A/D转换器满标度电压附近，再进行A/D转换，实现了0.003%精度的非线性16位无误码数据输出；其增益和数据输出更新速率均可编程设定，还可选择输入模拟缓冲器，以及自校准和系统校准方式。通过外接高精密导电塑料电位器传感器，由基准电压值分压后所得电压值即反映了阀门位置值。
In order to achieve digital detection of the valve position, the Analog Devices 16-bit 电荷-Δ (charge-balanced) A/D converter AD7705 is used in the A/D conversion circuit. The AD7705 includes a front-end analog conditioning circuit, a sigma-delta modulator, and a programmable digital filter that consists of a buffer and a gain programmable amplifier (PGA), which can directly amplify the signals in the different swing ranges from the sensor to A/. The D converter is near the full-scale voltage and then performs A/D conversion. It achieves 0.003% accuracy of non-linear 16-bit error-free data output; its gain and data output update rate are programmable, and the input analog buffer can also be selected. And self-calibration and system calibration methods. Through the external high-precision conductive plastic potentiometer sensor, the voltage value obtained by dividing the reference voltage value reflects the valve position value.

系统采用TRULY公司生产的128×64点阵液晶，它的所有控制器、扫描电路和显示RAM集成于液晶屏背面，并带有LED背光。该模块采用单电源供电，由大规模点阵式显示控制器KS0107、液晶屏阵列驱动电路KS0108、显示存储器和液晶屏等4部分组成。
The system uses a 128 x 64 dot matrix liquid crystal manufactured by TRULY, and all its controllers, scanning circuits and display RAM are integrated on the back of the LCD screen with LED backlight. The module is powered by a single power supply and is composed of a large-scale dot matrix display controller KS0107, LCD panel drive circuit KS0108, display memory, and LCD screen.
智能型电动执行器执行器软件设计
Smart Actuator Software Design

软件设计主要包括三个方面：QT总线通信模块、电动执行器的控制和LCD显示。
The software design mainly includes three aspects: QT bus communication module, electric actuator control and LCD display.

QT总线通信部分可将SJA1000初始化，在其初始化完成以后回到正常工作状态，将执行器的运行情况通过总线向上位机传送，而且操作者可以从上位机下达控制指令来操作执行器。
The QT bus communication part can initialize the SJA1000, return to the normal working state after its initialization is complete, and transmit the operating condition of the actuator to the upper computer via the bus, and the operator can operate the actuator by issuing a control instruction from the upper computer.

电动执行器的控制部分主要实现阀门的位置控制功能，还可以通过控制电机的转速来控制阀门的闭合速度。LCD显示部分主要显示阀门的阀位情况和执行器的工作情况，还可以显示上位机给执行器发出的控制信号。
The control part of the electric actuator mainly realizes the position control function of the valve, and can also control the closing speed of the valve by controlling the rotation speed of the motor. The LCD display part mainly shows the valve position of the valve and the working condition of the actuator. It can also display the control signal sent by the upper computer to the actuator.