CN110702974A - High-reliability current sampling circuit of alternating current servo motor - Google Patents
High-reliability current sampling circuit of alternating current servo motor Download PDFInfo
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- CN110702974A CN110702974A CN201911003198.8A CN201911003198A CN110702974A CN 110702974 A CN110702974 A CN 110702974A CN 201911003198 A CN201911003198 A CN 201911003198A CN 110702974 A CN110702974 A CN 110702974A
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Abstract
The invention discloses a high-reliability current sampling circuit of an alternating current servo motor, which comprises: the resistance sampling unit is used for converting a phase current signal of the alternating current servo motor into an alternating voltage signal for transmission; an isolation amplifier unit for converting the alternating voltage signal into a differential voltage signal; the differential conditioning unit is used for carrying out scaling and filtering processing on the differential voltage signal; the sigma-delta modulation unit is used for converting the differential voltage signal processed by the differential conditioning unit into a digital quantity signal; and the central processing unit is used for calculating the digital quantity signal and acquiring a sampling current value. The invention converts the phase current signal of the alternating current servo motor into a differential voltage signal for transmission by adopting the resistance sampling unit and the isolation amplifier unit, realizes signal isolation, and simultaneously utilizes the differential amplifier unit and the sigma-delta modulation unit to condition, shape and convert the differential voltage signal into analog-to-digital. The method has the characteristics of low cost, high anti-interference performance, good isolation effect and high reliability.
Description
Technical Field
The invention relates to the technical field of motor current detection, in particular to a high-reliability alternating current servo motor current sampling circuit.
Background
Industrial motion control covers a range of applications including inverter-based fan or pump control, factory automation with more complex ac drive control, and advanced automation applications (e.g., robots with advanced servo control). These systems require sensing and feedback of a number of variables such as motor winding current or voltage, dc link current or voltage, rotor position and speed. The choice of variables and the required measurement accuracy depends on the end-application requirements, system architecture, target system cost, or system complexity. In the control strategy of the alternating current servo motor, the current sampling performance is an important index. A typical three-closed-loop control structure is generally adopted in an alternating current servo drive control system and comprises a position loop, a speed loop and a current loop, wherein the current loop is used as an innermost link, actual current needs to be accurately reproduced, the fastest dynamic adjustment characteristic of a motor can be ensured, and the quick response of the torque of the motor is ensured. However, the ac servo driving system has a complex application environment and a high switching frequency, so that the phase current of the ac servo motor has a high harmonic content, and thus current sampling becomes a difficult point in the hardware of the ac servo control system.
The current sampling methods most commonly used in motor control at present are high-precision low-resistance sampling, Hall Effect Sensors (HES) and Current Transformers (CT). The high-precision low-resistance resistor sampling mode has the advantages of linearity, lowest cost, suitability for alternating current and direct current measurement, no isolation function and loss; current transformers and hall effect sensors, while providing inherent isolation, can also be used in higher current systems, but such sensors themselves have poor initial accuracy and accuracy in temperature, and are relatively costly.
In view of this, it is an urgent need to solve the technical problem in the art to develop a low-cost and high-reliability ac servo motor current sampling circuit.
Disclosure of Invention
The invention aims to provide a high-reliability alternating current servo motor current sampling circuit, which realizes signal isolation and converts an alternating current motor current signal into a differential voltage signal for transmission by adopting a resistance sampling unit and an isolation amplifier unit, is not only suitable for alternating current and direct current measurement, but also has stronger anti-interference performance, and simultaneously utilizes a differential conditioning unit and a sigma-delta modulation unit to condition, shape and convert an analog-to-digital signal for the differential voltage signal, thereby providing excellent performance even at a lower input signal level, meeting the sampling requirement in a wider range and greatly reducing the hardware cost.
In order to solve the above technical problem, the present invention provides a high-reliability current sampling circuit for an ac servo motor, comprising:
the resistance sampling unit is used for converting a phase current signal of the alternating current servo motor into an alternating voltage signal for transmission;
the isolation amplifier unit is used for converting the alternating voltage signal of the resistance sampling unit into a differential voltage signal;
the differential conditioning unit is used for carrying out scaling and filtering processing on the differential voltage signal of the isolation amplifier unit;
the sigma-delta modulation unit is used for converting the differential voltage signal processed by the differential conditioning unit into a digital voltage signal;
and the central processing unit is used for receiving the digital voltage signal of the sigma-delta modulation unit and carrying out filtering processing on the digital voltage signal so as to obtain a sampling current value of the servo motor.
Preferably, the resistance sampling unit comprises a high-precision alloy resistor R1, and the high-precision alloy resistor R1 is directly connected in series in a phase line of the alternating current servo motor.
Preferably, the isolation amplifier unit includes an isolation amplifier U1, which is implemented using an AMC1100 chip from TI corporation.
Preferably, the differential conditioning unit comprises a fully differential amplifier U2, and the fully differential amplifier U2 adopts a THS4531 chip of TI company.
Preferably, the sigma-delta modulation unit comprises a sigma-delta modulator U3, and the sigma-delta modulator U3 employs ADS131a04 series chips of TI corporation.
Compared with the prior art, the invention realizes the isolation of output and input signals by adopting the resistance sampling unit and the isolation amplifier unit and converts the phase current signal of the alternating current servo motor into a differential voltage signal for transmission, thereby fully utilizing the advantages of good resistance sampling linearity, lowest cost and suitability for alternating current and direct current measurement, and greatly improving the anti-interference performance of the current sampling system; meanwhile, the differential voltage signal is conditioned, shaped and subjected to analog-to-digital conversion by the differential amplifier unit and the sigma-delta modulation unit, and excellent performance can be provided even under a lower input signal level, so that the sampling circuit disclosed by the invention can meet a wider sampling requirement, and the hardware cost is greatly reduced. The method has the characteristics of low cost, high anti-interference performance, good isolation effect and high reliability.
Drawings
FIG. 1 is a block diagram of a high-reliability AC servo motor current sampling circuit according to the present invention,
FIG. 2 is an overall circuit diagram of a high-reliability AC servo motor current sampling circuit according to the present invention,
figure 3 is a circuit diagram of a resistive sampling cell and an isolation amplifier cell of the present invention,
figure 4 is a circuit diagram of a differential conditioning unit of the present invention,
fig. 5 is a circuit diagram of a sigma-delta modulation unit according to the present invention.
In the figure: 1. the device comprises a resistance sampling unit, 2 an isolation amplifier unit, 3 a differential conditioning unit, 4 a sigma-delta modulation unit and 5 a central processing unit.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings.
As shown in fig. 1, a high-reliability ac servo motor current sampling circuit includes:
the resistance sampling unit 1 is used for converting a phase current signal of the alternating current servo motor into an alternating voltage signal for transmission;
the isolation amplifier unit 2 is used for converting the alternating voltage signal of the resistance sampling unit 1 into a differential voltage signal;
the differential conditioning unit 3 is used for carrying out scaling and filtering processing on the differential voltage signal of the isolation amplifier unit 2;
the sigma-delta modulation unit 4 is configured to convert the differential voltage signal processed by the differential conditioning unit 3 into a digital voltage signal;
and the central processing unit 5 is used for receiving the digital voltage signal of the sigma-delta modulation unit 4 and performing filtering processing, so as to obtain a sampling current value of the servo motor.
In the embodiment, the isolation of output and input signals is realized by adopting the resistance sampling unit 1 and the isolation amplifier unit 2, and the phase current signal of the alternating current servo motor is converted into a differential voltage analog signal for transmission, so that the advantages of good resistance sampling linearity, lowest cost and suitability for alternating current and direct current measurement are fully utilized, and the anti-interference performance of the current sampling system is greatly improved; meanwhile, the differential conditioning unit 3 and the sigma-delta modulation unit 4 are used for conditioning, shaping and analog-to-digital conversion of the differential voltage analog signal, so that a digital voltage signal is obtained, and the obtained digital voltage signal is subjected to filtering processing (sinc3 filtering algorithm) by the central processing unit 5, so that the sampling current value of the servo motor is obtained. The sampling circuit of the invention can provide excellent performance even under the condition of lower input signal level, thus meeting the requirement of current sampling in a wider range and greatly reducing the hardware cost. The method has the characteristics of low cost, high anti-interference performance, good isolation effect and high reliability.
As shown in fig. 2 and fig. 3, the resistance sampling unit 1 includes a high-precision alloy resistor R1, and the high-precision alloy resistor R1 is directly connected in series to the phase line of the ac servo motor. In this embodiment, the phase current of the ac servo motor is converted into an alternating voltage signal after passing through the high-precision alloy resistor R1, and then transmitted to the isolation amplifier unit 2 through the differential filter circuit formed by the resistor R2, the resistor R3, and the capacitor C1.
As shown in fig. 2 and 3, the isolation amplifier unit 2 includes an isolation amplifier U1, which is an AMC1100 chip from TI corporation. In this embodiment, the isolation amplifier U1 is a TI AMC1100 chip, and the relevant pins of the chip include: primary side power supply pins VDD1 and GND1, secondary side power supply pins VDD2 and GND2, primary side signal input pins VIN + and VIN-, and secondary side signal output pins VOUT + and VOUT-, adopt 5V for power supply. C2 and C3 are decoupling capacitors, an external power supply supplies power to the AMC1100 chip after being subjected to capacitance filtering, and the VCCISO and the VCC power supply are isolated through an isolation amplifier U1, so that isolation between a sampled alternating voltage signal and output V + and V-signals is realized.
As shown in fig. 2 and 4, the differential conditioning unit 3 includes a fully differential amplifier U2, and the fully differential amplifier U2 is a THS4531 chip of TI. In this embodiment, the differential conditioning unit 3 includes a fully differential amplifier U2, resistors R4-R9, and capacitors C4-C10. Wherein the relevant pins of the fully differential amplifier U2 comprise: the VCOM pin sets the voltage input to the positive terminal voltage input pin + IN and the negative terminal voltage input pin-IN of the amplifier at a ratio of 1:1 to set the common mode output voltage, the amplifier positive terminal output voltage pin + OUT and the negative terminal voltage output pin-OUT have an inverse relationship between the input voltage and the output voltage. In the embodiment, the fully differential amplifier U2 selects the THS4531 chip of the TI company for fully differential amplification, the chip is a low-cost, differential or single-ended input to the differential output amplifier, the gain can be set through the feedback resistor, and compared with the conventional operational amplifier, the fully differential amplifier has great advantages in transmission of a micro signal long line, and can effectively suppress harmonic waves and reduce radiation electromagnetic interference. The isolated alternating voltage signals V + and V-are respectively connected with a low-voltage system reference ground GND through C4 and C5 and are subjected to basic filtering processing, V + enters a positive input pin + IN of U2 through R4, V-enters a negative input pin-IN of U2 through R5, VCOM is connected with GND through a capacitor C6, the + IN and a negative output pin-OUT are connected with C7 through R6, the IN and a positive output pin + OUT are connected with C8 through R7 to form a feedback loop, different scaling ratios are realized by adjusting the resistance values of R4-R7, attention needs to be paid to ensuring that R4/R6 is R5/R7, and the gain relation between the input voltage and the output voltage is R6/R4 times that the input voltage is input. The positive output pin forms a first-order low-pass filter circuit through R9 and C10, the negative output pin forms a first-order low-pass filter circuit through R8 and C9, and the positive output and the negative output are input to the sigma-delta modulation unit in a differential pair mode.
As shown in fig. 2 and 5, the sigma-delta modulation unit 4 includes a sigma-delta modulator U3, and the sigma-delta modulator U3 employs ADS131a04 chip series by TI. In this embodiment, the sigma-delta modulation unit 4 includes a sigma-delta modulator U3, resistors R10-R22, and capacitors C11-C16, wherein the sigma-delta modulator U3 selects an ADS131a04 chip of TI corporation, and related pins of the chip include: analog input pins 4, AIN1P/N-AIN4P/N, analog power supply pins AVDD and analog negative power supply pins AVSS, analog output pins CAP and VNCP, communication pins CS #, SCLK, DIN, DONE #, DOUT and DRDY #, digital power supply pins IOVDD and digital power ground pin GND, digital input pins M0, M1 and M2, clock input pin XTAL1/XTAL2, analog reference level input and output pins REFEX, REFFP and REFN, RESET pin RESET # and reserved pin V, ADS131A0X series chips are two-channel or four-channel synchronous sampling 24-bit sigma-delta analog-to-digital converters. The wide dynamic range, the scalable data rate of the maximum 128kSPS, the built-in fault monitor and the like are achieved, and the method is very suitable for energy monitoring, power grid protection and control and other applications. The series of chips have flexible power supply options (including internal negative charge pumps), can improve the effective resolution to the maximum extent, and are very suitable for wide dynamic range application. IN the method, a simplest 4-path synchronous sampling circuit is drawn by using an internal reference level of a chip, VOUT + and VOUT-after operation and amplification conditioning are input into a fourth path of analog input interfaces AIN4P and AIN4N, and the other three paths of interfaces are respectively connected with U + and U- (collecting the other phase current of an alternating current motor), VDC _ IN (direct current bus voltage sampling) and TEMP _ IN (temperature sampling). CLK _ IN is used as ADC sampling external clock reference, ADC _ RESET, SPI _ SCLK, SPI _ MOSI, SPI _ MISO and SPI _ DRDY are connected with a central processing unit, and the collected model is decoded. In this example, the key signal sampling requirement in the servo system can be realized by using one ADS131a04 chip, which is a set of excellent synchronous sampling scheme with high precision and low cost.
The current sampling circuit of the high-reliability alternating current servo motor provided by the invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the core concepts of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (5)
1. The utility model provides a high reliability AC servo motor current sampling circuit which characterized in that includes:
the resistance sampling unit (1) is used for converting a phase current signal of the alternating current servo motor into an alternating voltage signal for transmission;
an isolation amplifier unit (2) for converting the alternating voltage signal of the resistance sampling unit (1) into a differential voltage signal;
the differential conditioning unit (3) is used for carrying out scaling and filtering processing on the differential voltage signal of the isolation amplifier unit (2);
the sigma-delta modulation unit (4) is used for converting the differential voltage signal processed by the differential conditioning unit (3) into a digital voltage signal;
and the central processing unit (5) is used for receiving the digital voltage signal of the sigma-delta modulation unit (4) and carrying out filtering processing, so that the sampling current value of the servo motor is obtained.
2. The high-reliability AC servo motor current sampling circuit according to claim 1, wherein the resistance sampling unit (1) comprises a high-precision alloy resistor R1, and the high-precision alloy resistor R1 is directly connected in series with a phase line of the AC servo motor.
3. A high reliability ac servo motor current sampling circuit according to claim 1, characterized in that the isolation amplifier unit (2) comprises an isolation amplifier U1, which is implemented as an AMC1100 chip from TI corporation.
4. The high-reliability AC servo motor current sampling circuit according to claim 1, wherein the differential conditioning unit (3) comprises a fully differential amplifier U2, and the fully differential amplifier U2 adopts a TI THS4531 chip.
5. The high reliability ac servo motor current sampling circuit of claim 1, wherein the sigma-delta modulation unit (4) comprises a sigma-delta modulator U3, the sigma-delta modulator U3 being an ADS131a04 series chip from TI corporation.
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| CN111398658A (en) * | 2020-04-03 | 2020-07-10 | 北京京源恒泰云科技有限公司 | Isolated current sensor |
| CN111426874A (en) * | 2020-05-25 | 2020-07-17 | 湖南科技大学 | Strong anti-interference wide-range alternating current permanent magnet synchronous motor current sampling circuit |
| CN113552412A (en) * | 2021-07-15 | 2021-10-26 | 北京思灵机器人科技有限责任公司 | Phase current acquisition device and method of motor and motor driving system |
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