Hardware and electrical design of intelligent QT electric actuator

在工業控制系統中，電動執行器是電動單元組合儀表中一個很重要的執行單元。它由控制電路和執行機構兩個在電路上*獨立的部分組成，可接收來自調節器的電控信號，將其線性地轉換成機械轉角或直線位移，用來操縱風門、擋板、閥門等調節機構，以實現自動控制。近年來，隨著微電子技術和控制技術的迅速發展，電動執行器也獲得了快速發展，特別是國外一些生產廠商在這幾年中相繼推出了常規的、帶現場總線通信協議的智能電動執行器，而智能QT電動執行器就是有發展潛力的一種。
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.

本文介紹的智能QT電動執行器采用無刷直流電機控制，控制精度高，實現了數字化的閥位檢測，可提高閥位測量的精度和可靠性，能取代現行普遍采用的電位器和差動變壓器模擬測量方法。
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.

控制電路的硬件設計
Control circuit hardware design

整個電路主要由五個部分組成：單片機P89C58為主的主機部分，由SJA1000、82C250、光電隔離電路等組成的QT總線控制及接口部分，由無刷直流電機控制芯片MC33035組成的電機控制部分，閥門位置檢測部分和LCD液晶顯示部分。 1 QT總線及接口部分 QT總線控制及接口如圖2所示，主要包括獨立QT通信控制器SJA1000、QT總線收發器82C250和高速光電耦合器6N137。 單片機P89C58首先對SJA1000進行初始化，控制SJA1000實現數據的通信任務。SJA1000的AD0～AD7連接到89C52的P0口，CS連接到89C52的P2.0口，其余的引腳分別對應相連。 　
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.

為了增強QT總線節點的抗*力，SJA1000的TX0和RX0并不是直接與82C250的TXD和RXD相連，而是經高速光耦6N137后再與82C250相連，這樣就很好地實現了總線上各QT節點間的電氣隔離。82C250與QT總線的接口也采用了一定的安全和抗干擾措施，它的QTH和QTL引腳與QT總線之間各串聯一個5Ω的電阻，這樣可起到一定的限流作用，保護82C250免受過流的沖擊；還可以在QTH和QTL引腳上并聯小電容，起到濾除總線上的高頻干擾和防電磁輻射的作用。82C250的Rs腳上接有一個斜率電阻，電阻大小可根據總線通信速度適當調整，一般在16～140kΩ之間。
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.

電機控制電路
Motor control circuit

該電動執行器里電機控制芯片采用了安森美公司開發的高性能第二代單元無刷直流電機控制器MC33035。該控制器內含可用于正確整流時序的轉子位置譯碼器，以及可對傳感器的溫度進行補償的參考電平；同時，還具有一個頻率可編程的鋸齒波振蕩器、一個誤差信號放大器、一個脈沖調制器比較器、三個集電極開路頂端驅動輸出和三個非常適用于驅動功率MOSFET的大電流圖騰柱式底部輸出器。
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.
該電機控制電路的功能包括PWM開環速度控制、使能控制和正反轉控制。電機的轉速控制是利用4-10位譯碼器/驅動器74LS145的功能，由單片機P89C58給出信號，通過分壓電路提供給引腳速度電壓來實現的。
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.

電機的使能控制和正反轉控制信號也由單片機控制，發出電平信號給89C2051，進行電平轉換后輸出給MC33035相應的管腳來控制電機的工作狀態。
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.

閥門位置檢測電路和液晶顯示
Valve position detection circuit and liquid crystal display

為了實現閥位的數字化檢測，在A/D轉換電路中采用了ADI公司的16位∑-△(電荷平衡式)A/D轉換器AD7705。AD7705包括由緩沖器和增益可編程放大器(PGA)組成的前端模擬調節電路、∑-△調制器及可編程數字濾波器等，能直接將來自傳感器的不同擺幅范圍內的信號放大到A/D轉換器滿標度電壓附近，再進行A/D轉換，實現了0.003%精度的非線性16位無誤碼數據輸出；其增益和數據輸出更新速率均可編程設定，還可選擇輸入模擬緩沖器，以及自校準和系統校準方式。通過外接高精密導電塑料電位器傳感器，由基準電壓值分壓后所得電壓值即反映了閥門位置值。
In order to achieve digital detection of the valve position, the Analog Devices 16-bit 電荷-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.

系統采用TRULY公司生產的128×64點陣液晶，它的所有控制器、掃描電路和顯示RAM集成于液晶屏背面，并帶有LED背光。該模塊采用單電源供電，由大規模點陣式顯示控制器KS0107、液晶屏陣列驅動電路KS0108、顯示存儲器和液晶屏等4部分組成。
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.
智能型電動執行器執行器軟件設計
Smart Actuator Software Design

軟件設計主要包括三個方面：QT總線通信模塊、電動執行器的控制和LCD顯示。
The software design mainly includes three aspects: QT bus communication module, electric actuator control and LCD display.

QT總線通信部分可將SJA1000初始化，在其初始化完成以后回到正常工作狀態，將執行器的運行情況通過總線向上位機傳送，而且操作者可以從上位機下達控制指令來操作執行器。
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.

電動執行器的控制部分主要實現閥門的位置控制功能，還可以通過控制電機的轉速來控制閥門的閉合速度。LCD顯示部分主要顯示閥門的閥位情況和執行器的工作情況，還可以顯示上位機給執行器發出的控制信號。
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.