CN111723543A

CN111723543A - Electromagnetic compatibility design method of electric cylinder, electromagnetic compatibility electric cylinder and application

Info

Publication number: CN111723543A
Application number: CN202010560605.1A
Authority: CN
Inventors: 张鑫; 彭海波; 袁艳
Original assignee: Xian Microelectronics Technology Institute
Current assignee: Xian Microelectronics Technology Institute
Priority date: 2020-06-18
Filing date: 2020-06-18
Publication date: 2020-09-29
Anticipated expiration: 2040-06-18
Also published as: CN111723543B

Abstract

An electromagnetic compatibility design method of an electric cylinder, the electromagnetic compatibility electric cylinder and application thereof provide an electromagnetic compatibility design method throughout the original design aiming at the characteristics of electric cylinder products, and realize forward electromagnetic compatibility design. The design method comprises the steps of electromagnetic compatibility overall planning of the electric cylinder, electromagnetic compatibility design of the electric principle of the electric cylinder, PCB electromagnetic compatibility design of the electric cylinder and structural electromagnetic compatibility design of the electric cylinder. The invention relates to an electric cylinder electric interference source and a disturbed source identification, which is characterized in that principle level system division is carried out according to the electric characteristics of an electric cylinder, the layout and wiring design of an electric cylinder printed board based on signal flow direction, the static design of the electric cylinder printed board, the local ground plane design of a crystal oscillator and the semi-surrounding design of an electric cylinder shell structure are adopted.

Description

Electromagnetic compatibility design method of electric cylinder, electromagnetic compatibility electric cylinder and application

Technical Field

The invention belongs to the field of electric cylinder design, and particularly relates to an electromagnetic compatibility design method of an electric cylinder, an electromagnetic compatibility electric cylinder and application.

Background

The electric cylinder product is used as a high-precision linear displacement electromechanical output device and is widely applied to the fields of radio astronomy, machine tool control, medical instruments and the like. The electric cylinder subsystem is used as an important component of the whole system, and the electromagnetic compatibility of the electric cylinder subsystem plays an important role in stable operation of the whole system, so that the requirement on the electromagnetic compatibility of the electric cylinder is gradually strict. Although the traditional electric cylinder design includes an electric design, a structural design and a transmission design, the electromagnetic compatibility design does not systematically run through the electric cylinder design. After the electric cylinder product is debugged, the electromagnetic compatibility examination test shows that the product is difficult to pass the electromagnetic compatibility requirement. At the moment, the electromagnetic compatibility rectification can be carried out only through temporary measures, and the effect, manufacturability and aesthetic property after rectification are not as good as those of a one-step molded product.

Disclosure of Invention

The invention aims to solve the problem that the electric cylinder in the prior art is difficult to pass the electromagnetic compatibility requirement after debugging is finished, and provides an electromagnetic compatibility design method of the electric cylinder, an electromagnetic compatibility electric cylinder and application thereof, so that the forward design of electromagnetic compatibility is realized, the electromagnetic compatibility of an electric cylinder product is effectively improved, the manufacturability and the attractiveness of the product are prevented from being damaged, and the product development cost is reduced.

In order to achieve the purpose, the invention adopts the following technical scheme:

an electromagnetic compatibility design method of an electric cylinder comprises the following steps:

s1, electromagnetic compatibility overall design of the electric cylinder;

planning from two aspects of a power supply form and a communication form; the power supply mode avoids the clock interference source formed by the added direct current/direct current conversion module after the power frequency 220V power supply is introduced into the electric cylinder, and simultaneously avoids the power line harmonic interference introduced by the power frequency 220V power supply; the communication form can carry different communication protocols to realize networking requirements, and can avoid common mode radiation and differential mode radiation caused by copper wires;

s2, designing an electromagnetic compatibility circuit principle of the electric cylinder;

the design object comprises a processor, a secondary power supply, Ethernet communication, analog quantity acquisition and motor drive;

2.1) identifying an electromagnetic compatibility interference source and a disturbed source;

2.2) carrying out principle level system distribution;

2.3) selecting devices with rich functions, and performing electromagnetic compatibility design optimization on an interference source and a disturbed source;

2.4) carrying out electromagnetic compatibility filtering design on the interference source and the disturbed source;

2.5) checking whether the indications adopted for the interference source and the disturbed source are valid, if so, returning to the step 2.2) to execute the step 2.2) to the step 2.4) again, and if both are covered in place, finishing the design of the electromagnetic compatibility principle of the electric cylinder;

s3, designing an electromagnetic compatibility PCB of the electric cylinder;

3.1) designing a printed board layer;

the shielding cavity formed by the printed board layer is utilized to the maximum extent, and the minimum area is formed for the signal loop;

3.2) designing the layout of devices on the printed board;

3.3) wiring design of the printed board;

3.4) carrying out electromagnetic compatibility design inspection on the stratum, layout and wiring of the printed board of the electric cylinder according to the division of the interference source and the interfered source, and returning to the step 3.1) to re-execute the steps 3.1) to 3.3 if the electromagnetic compatibility design inspection is omitted until the requirements are all met;

s4, designing electromagnetic compatibility of the electric cylinder shell, including internal layout and wiring design of the shell, structural design of the shell, and hole and seam inhibition design, and checking whether the wiring of the case and the hole and seam formed by the shell are processed.

The step 2.1) carries out the classification and arrangement of the schematic diagram signals according to the following table:

the signal cut-off frequency is calculated according to the following formula:

if the message is knownSignal time domain rise time tau, signal cut-off frequency

If only the duration T of 1bit of the signal is known, the signal time domain rise time

Then, according to the re-calculation signal cut-off frequency;

the identification method comprises the following steps: the signal is the strongest interference source with high power and high level, high cut-off frequency and single-ended signal; the signal is low power and low level and is single ended is the most sensitive victim.

Step 2.2) the method for carrying out principle level system distribution comprises the following steps: the digital system ground, the analog system ground and the servo driving system ground are respectively kept in physical isolation; when two ground systems have mutual interference but the ground planes can work only by the same static working point, the two ground systems are connected through magnetic beads at nearby positions except for physical isolation; when two ground systems are physically separated according to functional design requirements, but one of the ground systems can form larger distributed capacitance, the two ground systems are connected nearby through the capacitance.

Step 2.4) electromagnetic compatibility filtering design for the crystal oscillator is as follows: decoupling capacitors are respectively designed at power supply inlets of the crystal oscillator, each decoupling capacitor comprises a tantalum electrolytic capacitor C1, a multilayer ceramic dielectric capacitor C2 and a capacitor C3 connected with magnetic beads L1 in series, RC filtering is connected with output ends of the crystal oscillator in series, a capacitor C4 and a resistor R1 are designed, the capacitor C4 is a multilayer ceramic dielectric surface-mounted capacitor, and the resistor R1 is a surface-mounted resistor.

The design principle of the step 3.1) comprises the following steps:

preferably, a multi-level printed board; the number of layers is even; paving a larger area on the second layer or the penultimate layer; the ground plane remains intact; the number of the polygon edges is reduced, and the convex polygon is superior to the concave polygon; wiring in the inner layer preferentially; preferentially wiring in no adjacent wiring layer, or vertically routing the adjacent wiring layer or no routing below the corresponding wiring area although the adjacent wiring layer exists; the wiring layer of the key signal line is provided with an adjacent reference stratum and ensures that the key routing does not cross the ground partition area;

in order to enable common mode interference on the printed board to be released through a low impedance path and reduce the radiation efficiency to the outside on the printed board, a static ground is designed around the printed board to form a closed annular copper-clad layer, and the closed annular copper-clad layer is electrically connected with the metal case;

the static design method comprises the following steps: each layer on the printed board is designed with a static ground with the same shape; the quiet area can not have other stratums, power supply layers and routing signals; the width of the static ground can not only release internal high-frequency noise, but also avoid interference and intrusion in the printed board; the static ground is electrically connected with the metal casing by a printed board structure fastening mode, and the strength of the printed board is considered; the metal fastener of the connector on the board is punched in a static area, and the electrical connection is realized; if the PCB is designed with the metal shielding cover, the length and the width of the metal shielding cover are attached to the static ground, and the metal shielding cover, the static ground and the metal shell are electrically connected.

The device layout design method of the step 3.2) comprises the following steps: the priority layout of important components, strong radiation sources and sensitive sources; the layout is carried out based on the layout idea of the signal flow direction, so that the shortest routing of interference signals and disturbed signals, the smallest loop area and the shortest parallel path of the interference signals and the disturbed signals are ensured; the method comprises the following steps of carrying out regional arrangement on an interference source and a disturbed source, and arranging a digital circuit, an analog circuit and a motor driving circuit in a regional manner; the critical interference source is placed along the vicinity of the center of the board; for the auxiliary circuit, the core device of each functional circuit is taken as the center, and the layout is performed around the core device according to the principle of proximity; the interface protection circuit is close to the connector, so that the shortest routing is realized and the interface protection circuit is arranged side by side; cutting the length of a pin aiming at a filter capacitor of a specific chip and enabling the pin to be close to the pin of the specific chip; when a plurality of capacitors are used for filtering, the smaller the capacitance value is, the closer the capacitance value is to the chip pin; the series matching resistance of the crystal oscillator is close to the source end.

The wiring design method of the step 3.3) comprises the following steps:

firstly, wiring high-speed signals, high-frequency signals, strong-power signals, sensitive signals and low-noise margin signals, and secondly, wiring other signals; the wiring avoids changing layers, when the wiring layers need to be changed, the wiring layers on two sides of the same reference ground plane are selected, and the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to the other stratum, arranging a ground through hole near the through hole of the wiring layer change to connect the two stratums, wherein the size of the stratum through hole is the same as that of the signal through hole; a strong interference source is paved on a local ground plane below the device, the local ground plane is connected with the ground layer of the adjacent layer through a plurality of via holes, the clock signal runs through the inner layer, and when the clock signal must run through the surface layer, the maximum allowable length of the surface layer clock line is 1/20 of the wavelength of the clock signal; designing a guard transmission ground wire by using a strong interference signal and an easily sensitive signal, wherein the distance between the guard transmission ground wire and a signal to be protected is 3 times of the line width; the guard and transmission ground wire of the clock is connected with the stratum by punching holes every lambda/10, wherein lambda is the wavelength of the clock signal; high-speed signals or easily-disturbed signals cannot be transmitted below the coil, the common-mode inductor, the isolation transformer and the isolation operational amplifier; the copper sheet of the ground wire is forbidden to extend out of redundant wire ends or suspended branch ground wires, so that the antenna effect is avoided; when the signal differential pair or the power supply positive and negative wires are wired, the wire spacing is reduced as much as possible on the premise of meeting manufacturability, and the loop area is reduced.

The invention provides an electromagnetic compatibility electric cylinder at the same time, adopt direct current 28V to input the power supply, the physical medium of the communication network deployment is the optical fiber, the processor part regards DSP as the core, the external circuit includes crystal oscillator circuit, power management circuit and reset circuit, the secondary power supply is according to the design of the ground system, it is made up of several direct current/direct current converters and direct current steady voltage source, the Ethernet communication module is made up of Ethernet protocol chip, physical layer chip and optical module, the analog quantity acquisition module is made up of analog quantity acquisition chip as the basis, the motor drive module is made up of integrated chip of motor drive and field effect tube drive bridge; aiming at different systems, primary power supply is distributed, and grounding points of the corresponding systems are kept isolated; the printed board layer utilizes the shielding cavity formed by the printed board layer to the maximum extent, the minimum area is formed for a signal loop, static grounds are designed around the printed board, the layout of devices ensures that all signal flow directions return by the minimum path, the arrangement of an interference circuit and a disturbed circuit in different regions is realized, and the electromagnetic compatibility and external radiation in the board are reduced to the maximum extent; the wiring avoids changing layers, when the wiring layers need to be changed, the wiring layers on two sides of the same reference ground plane are selected, and the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to the other stratum, a ground through hole is arranged near the through hole of the wiring layer change to connect the two stratums, the size of the stratum through hole is the same as that of the signal through hole, and a strong interference signal and a sensitive signal design shielding ground wire; the shell structure adopts a semi-surrounding design to meet the assembly requirement, and conductive rubber is installed to ensure the shielding continuity.

Preferably, the electromagnetic compatibility electric cylinder realizes the same function, and the number and the types of interference source devices are reduced by selecting multifunctional devices; the W5300 chip is selected to realize the functions of the Ethernet protocol chip and the physical layer chip.

The front side cover and the rear side cover of the shell are integrally formed with the bottom cover, so that two long-edge gaps are avoided, and the radiation of the gaps is reduced; the left side cover and the upper cover are detachable, the technological assembly requirements of a printed board and a connector are met, and the right side is a connecting part of the shell of the electric cylinder controller and the transmission part; conductive rubber is embedded in the joint position of the upper cover, the joint position of the left side cover and the joint position of the right side cover in a slotted mode; the back glue type wave-absorbing patches are adhered to the wall surfaces of the front side cover and the rear side cover of the shell, the connector which is externally connected is arranged on the left side cover, and the tail cover of the wave-absorbing patch can meet 360-degree full shielding.

The invention also provides an active surface system of the radio astronomical telescope, and the electromagnetic compatible electric cylinder is adopted as an actuator of the active surface system.

Compared with the prior art, the invention has the following beneficial effects: the design method organically integrates the electromagnetic compatibility of the electric cylinder into the traditional functional design of the electric cylinder product, comprises the electromagnetic compatibility general planning of the electric cylinder, the electromagnetic compatibility design flow of the electric principle of the electric cylinder, the PCB electromagnetic compatibility design flow of the electric cylinder and the structural electromagnetic compatibility design flow of the electric cylinder, and provides a systematic electromagnetic compatibility design method which runs through the functional design of the electric cylinder product by standing at the electromagnetic compatibility angle and considering the characteristics of the electric cylinder according to the characteristics of the electric cylinder product.

Furthermore, a special filtering design method is provided for the crystal oscillator in the electric cylinder control panel, a topological structure with three parallel-stage capacitor filtering and series-connected magnetic beads is adopted for the crystal oscillator power supply, and a topological structure with RC network filtering is carried out for the clock signal output; the method for designing the local ground plane is provided for the wiring of the crystal oscillator and other radiation devices in the electric cylinder control panel, and comprises the design of the size of the ground plane and the relation between the ground plane and other devices and plate layers; aiming at a static ground design method, a static ground position and size design method and a placing relation between the static ground and other devices in an electric cylinder control plate; the electric cylinder printed board sums up the signal flow direction based on the idea of signal flow direction layout and wiring according to the circuit characteristics of the electric cylinder product, performs layout design according to the rule that the signal flow direction is shortest in wiring and minimum in loop area, organically integrates a complete electromagnetic compatibility link, and improves the electromagnetic compatibility of the electric cylinder product.

Furthermore, the shell adopts a semi-surrounding design method, three sides are integrally formed, and electromagnetic leakage of gaps is reduced.

Drawings

FIG. 1 is a general block diagram of a functional design of an electric cylinder product;

FIG. 2 is a flow chart of the electromagnetic compatibility principle design of the electric cylinder;

FIG. 3 is a block diagram of a schematic level system design plan;

FIG. 4 is a schematic diagram of the connection relationship between the systems;

FIG. 5 is a circuit diagram of a dedicated filter design for a crystal oscillator;

FIG. 6 is a comparison graph of the periodic clock output generated by the crystal oscillator before and after filtering;

FIG. 7 is a schematic view showing the connection relationship between magnetic beads;

FIG. 8 is a flow chart of the design of an electromagnetic compatibility PCB of the electric cylinder;

FIG. 9 is a schematic view of a design quiet ground around a printed board;

FIG. 10 is a schematic diagram of a device layout design on a printed board;

FIG. 11 is a schematic diagram of the device wiring design on the printed board;

FIG. 12 is a schematic diagram of a wiring layer change with a ground via connecting two strata;

FIG. 13 is a schematic view of a local ground plane connected to the ground layer of an adjacent layer by a plurality of vias;

FIG. 14 is a flow chart of a design for electromagnetic compatibility of the housing;

FIG. 15 is a schematic structural view of a housing of the electric cylinder;

fig. 16 is a schematic view of the embedding of the conductive rubber.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Referring to fig. 1, the electric cylinder is an electromechanical device for realizing high-precision linear displacement feeding by using electric energy. The design content for the electric cylinder includes overall design, electrical design, controller structure design and transmission design.

The overall design is an overall scheme for realizing function determination, a closed-loop control strategy is determined, the motor type is determined, the communication connection relation and the physical medium between the electric cylinder and the upper computer are determined, an electric function realization frame is determined, a transmission design frame is determined, and the like.

The electric design is realized by responding to a control instruction of an upper computer through communication, collecting and feeding back the position by a sensor, realizing a closed-loop control strategy on a DSP and finally realizing the power output of the controller to the motor.

The structural design refers to the controller housing design.

The transmission design refers to a worm gear design, a lead screw design and an end cover design.

The electromagnetic compatibility design method of the electric cylinder stands in the electromagnetic compatibility angle and considers the characteristics of the electric cylinder on the basis of the traditional function design steps of the electric cylinder, and provides the following new refined thought and method and is penetrated in the function design.

1. Electromagnetic compatibility overall planning of the electric cylinder;

the electromagnetic compatibility general planning of the electric cylinder belongs to a part of general design and is the content to be planned at the beginning of product detailed design. The electromagnetic compatibility overall planning of the electric cylinder is based on the overall design of products and is planned from two aspects of a power supply form and a communication form. In order to avoid a clock interference source formed by a direct current/direct current conversion module (DC/DC) added after power frequency 220V power supply is introduced into an electric cylinder and avoid power line harmonic interference introduced by power frequency 220V power supply, the electric cylinder adopts direct current 28V input power supply. The electric cylinder completes self action through a communication instruction. Although physical transmission media formed by traditional copper wires meet the requirements of different communication protocols, the copper wires inevitably couple external electromagnetic waves in a wiring path and influence the interior of the electric cylinder through conduction, so that the electromagnetic compatibility design method of the electric cylinder adopts the optical fiber as the physical media of the electric cylinder communication networking, can carry different communication protocols to realize networking requirements, and can effectively avoid common-mode radiation and differential-mode radiation caused by the copper wires.

2. The electric principle of the electric cylinder is designed in an electromagnetic compatibility mode;

the block diagram is realized by combining the functional design principle of the electric cylinder, and the electric part comprises a processor, a secondary power supply, Ethernet communication, analog quantity acquisition, motor drive and the like. The processor part takes a DSP as a core and is assisted by a crystal oscillator circuit, a power management circuit, a reset circuit and the like. The secondary power supply is composed of a plurality of direct current/direct current converters (DC/DC) and a direct current voltage stabilizing source according to the design of a ground system. The ethernet communication is composed of an ethernet protocol chip (Mac), a physical layer chip (PHY) and an optical module, which includes a crystal oscillator circuit. The analog acquisition is based on an analog acquisition chip (AD). The motor drive mainly comprises a motor drive integrated chip and a field effect transistor (MOS transistor) drive bridge. Referring to fig. 2, a design flow of electromagnetic compatibility principle of the electric cylinder is provided.

According to the process, firstly, the electromagnetic compatibility interference source and the interfered source are identified.

The schematic signal classification arrangement is performed according to the following table:

the signal cut-off frequency can be calculated according to two empirical formulas.

If the time domain rise time tau of the signal is known, the cut-off frequency of the signal

Then, the signal cut-off frequency is calculated.

The identification method comprises the following steps: the signal with high power and high level and high cut-off frequency is the strongest interferer and the signal with low power and low level is the most sensitive victim. And vice versa.

After the electric system is evaluated by the method, the interference source is the input signals of the crystal oscillator circuit and the linear sensor. The disturbed source is an AD acquisition circuit. In order to avoid ground bounce formed by signals with different powers and different levels on a common loop, which causes digital quantity misjudgment or analog quantity performance degradation, principle level ground system allocation is carried out next.

The electromagnetic compatibility principle level distribution method comprises the following steps: the digital system ground, the analog system ground and the servo driving system ground are respectively kept in physical isolation; when two ground systems have mutual interference but the ground planes can work only by the same static working point, the two ground systems are connected through magnetic beads at nearby positions except for physical isolation; when two earth systems are physically separated according to the functional design, but one of the earth systems (generally referred to as a shell earth) can form larger distributed capacitance, the two earth systems are connected nearby through the capacitance. According to the principle level system design method and the control system electricity utilization actual, the following scheme is planned, as shown in FIG. 3:

GND is the ground of chips such as DSP, Mac and PHY, AGND is the ground of analog quantities such as displacement sensor and temperature sensor, 36VGND is the ground of step driving chip, driving bridge and step motor, and EGND is the chassis ground.

Aiming at different systems, an isolation DC/DC is required to distribute a primary power supply, and accordingly, the grounding point of the system is kept isolated. If analog quantity interaction exists between different systems, the analog quantity interaction is realized by adopting an isolation device such as an isolation operational amplifier (for example, ISO124), a photocoupler (for example, HCNR201) and the like. If digital quantity interaction exists between different systems, a digital isolator (such as the ADuM2400), an isolation transformer and the like are adopted for realization.

Meanwhile, the connection relationship between the ground systems is designed as shown in fig. 3:

the L1 selects 500 omega magnetic beads at 100MHz to connect GND and AGND, so that the AD acquisition chip (AD7606) is ensured to share a DC working point while common mode interference is suppressed. Because the frequency range of the motor driving signal reaches 100kHz, the estimation is carried out according to a time constant formula: τ is RC, C is 10 μ F, and R is estimated to be 1 Ω; because the working frequency of the digital system is covered from 25MHz to 1GHz, 1GHz is taken for calculation, and according to a time constant formula, C is 1000pF and a surface-mounted capacitor is taken; theories and actual measurements show that: the external cable of the sensor can couple interference electromagnetic waves with the frequency of 100 MHz-500 MHz (an external displacement sensor is a plastic shell, and the shielding cable is difficult to realize full shielding contact), the amplitude is continuous in the range, and as the external displacement sensor is connected to the external linear sensor through the external cable in a simulated mode, according to a time constant formula, the C3 takes a 10nF surface-mounted capacitor.

The following is a principle level electromagnetic compatibility optimization for the aggressor and victim.

First, it is pointed out that: the same function is realized, and devices with rich functions are selected to reduce the number and the variety of interference sources such as crystal oscillators, interface isolators and the like. The high-integration, multi-functional chip is superior to a circuit realized by a separate function in electromagnetic compatibility because the high-integration chip has a shorter routing distance and a flexible packaging form. Therefore, in the electrical system, in order to realize ethernet communication, the electromagnetic compatibility of a single chip integrating Mac and PHY functions is better than that of two chips (the routing length of high-speed signals on a printed board is effectively avoided, and radiation is reduced), so that the W5300 chip is selected to realize Mac and PHY functions.

The unused chip input/output signals cannot be floating and should be connected to the operating ground through a low impedance.

The crystal oscillator is an indispensable element for normal operation of a digital circuit, but periodic clock jitter generated by the crystal oscillator is also one of the most serious sources of board-level electromagnetic interference (EMI), and a method is proposed for electromagnetic compatibility design of the crystal oscillator (interference source):

the output level types of the crystal oscillator are as follows: HCMOS, TTL, ACMOS, ECL and sine wave outputs. When the clock frequency is less than 70MHz, it is recommended to use an HCMOS level type crystal oscillator. When the clock frequency is greater than 70MHz, an ECL type crystal oscillator may be used. A specific filtering design is proposed for the crystal oscillator as shown in fig. 5, and then a filtering topology design is proposed for the key interference source.

When the crystal oscillator generates a periodic clock, switching noise is generated on a ground loop where the crystal oscillator is located, and the integrity of a power supply is influenced. Therefore, decoupling capacitors (C1, C2 and C3) are respectively designed at the power supply inlets of the crystal oscillator, wherein the capacitance value of C1 is 4.7 muF, and tantalum electrolytic capacitors are selected; wherein the capacitance value of C2 is 0.1 muF, and multilayer ceramic dielectric capacitors are selected; the capacitors are surface-mounted capacitors, so that the capacitance value of C3 in ESL (series equivalent inductance) and ESR (series equivalent resistance) is effectively reduced to 0.01 mu F, and meanwhile, magnetic beads L1 are connected in series, and magnetic beads of 200 omega at 100MHz are selected. The periodic clock generated by the crystal oscillator is not a perfect square wave but a superposition of limited harmonics, and in practice, the overshoot of the waveform is too large, which indicates that the circuit has large reflection, as shown in fig. 6, so that the output end of the crystal oscillator is connected in series with RC (resistor-capacitor) filtering, and C4 and R1 are designed, and C4 is a multilayer ceramic surface-mounted capacitor, namely 10 pF; r1 is designed to be a surface-mounted resistor, the resistance value is generally 22-51 omega, and meanwhile, the resistance value needs to be optimized according to the actual PCB debugging waveform.

The magnetic beads can be equivalent to series connection of an inductor and a resistor, have an obvious effect on high-frequency interference suppression, and can be subjected to surface mounting and through hole insertion due to the flexible packaging form. Therefore, in the principle design of the electric cylinder control plate, magnetic beads can be connected in series by inhibiting the interference generated during the transmission of high-frequency signals; the interference introduced by the external single-ended interface is suppressed by connecting the magnetic beads in series.

And aiming at the interference signal of the linear sensor, selecting a series magnetic bead on a signal wire to inhibit common-mode interference. The magnetic bead is selected to have the characteristic of 500 omega when the magnetic bead is 100MHz, and the self-resonance frequency is more than 800 Mhz. The connection relationship is shown in fig. 7.

And when the point position arrangement of the connector is timed, the ground pins and the signal pins are suggested to be designed and arranged in a staggered mode.

And finally, checking whether effective measures are taken for both the interference source and the disturbed source. If the omission exists, the process design is carried out again; and if the electric cylinders are covered in place, the design of the electromagnetic compatibility principle of the electric cylinder is finished.

The design measures aiming at the sensitive device AD acquisition chip are ensured by the system design.

3. PCB electromagnetic compatibility design of the electric cylinder;

after the electric principle design of the electric cylinder is completed, a circuit board diagram is formed through PCB design, so that engineering can be realized. Therefore, an electromagnetic compatibility PCB design flow of the electric cylinder is provided.

Referring to fig. 8, a PCB-level electromagnetic compatibility design is performed based on the identification results of the electric cylinder principle level interference source and the disturbed source.

The design method of the printed board layer in the electric cylinder comprises the following steps:

1) the electromagnetic compatibility of the multi-level printed board is obviously superior to that of a single-layer printed board;

2) the number of layers is even;

3) arranging a large-area ground on the second layer or the penultimate layer;

4) the ground plane remains as intact as possible, rectangular in shape and with an aspect ratio of less than 3 being optimal;

5) if the ground plane cannot be kept rectangular due to manufacturability, etc., the number of sides of the polygon is reduced as much as possible. Moreover, the shape of the convex polygon is better than that of the concave polygon;

6) wiring in the inner layer preferentially;

7) preferentially wiring in no adjacent wiring layer, or vertically routing the adjacent wiring layer or no routing below the corresponding wiring area although the adjacent wiring layer exists;

8) the wiring layer of the critical signal line should have an adjacent reference ground layer and ensure that the critical trace does not cross the ground partition.

Layer optimization design of the four-layer plate: S1/G/P/S2;

layer optimization design of the six-layer plate: S1/G1/S2/P/G2/S3;

layer optimization design of eight-layer plates: S1/G1/S2/G2/P/S3/G3/S4;

layer optimization design of ten-layer plates: S1/G1/S2/P1/S3/G2/P2/S4/G3/S5;

wherein S represents a signal layer, G represents a stratum, and P represents a power supply layer;

the design of the above layers accords with the design method of the printed board layer, the shielding cavity formed by the printed board layer is utilized to the maximum extent, and the minimum area is formed for the signal loop.

In the design of the electric cylinder printed board, the eight-layer board layer design is adopted.

In order to enable common mode interference on the printed board to be discharged through a low impedance path and reduce the efficiency of radiation to the outside on the printed board, a static ground is designed around the printed board to form a closed annular copper clad, and the closed annular copper clad is fastened through a plurality of structural screws and electrically connected with a metal case.

The static design method of the invention is as follows:

1) each layer on the printed board is designed with a static ground with the same shape;

2) the quiet area can not have other stratums, power supply layers and routing signals;

3) the width of the static ground is generally 2-7 mm, so that internal high-frequency noise is released, and external lightning and other interference can be prevented from invading the inside of the printed board;

4) the metal shell is electrically connected with the printed circuit board in a structure fastening mode such as mounting screws of the printed circuit board, the strength of the printed circuit board is considered, and generally at least 6-8 screws are used for fastening the printed circuit board; the screw holes are all metallized holes;

5) referring to fig. 9, the metal fastener of the board connector is punched in the static area, and is electrically connected with the connector through a screw;

6) if the PCB needs to be designed with the metal shielding cover, the length and the width of the metal shielding cover are just attached to the static ground, and the metal shielding cover, the static ground and the metal shell are electrically connected through welding, screwing and other processes.

In the printed board design of the electric cylinder, a static ground design shown in fig. 9 is adopted, and the static ground width is selected to be 5 mm.

Referring to fig. 10, the layout method of the electric cylinder printed board of the present invention is as follows:

1) the layout principle of 'big first, small first, difficult first and easy last', and the priority layout of important components, strong radiation sources and sensitive sources;

2) the layout is carried out based on the layout idea of signal flow direction, firstly, the shortest routing of an interference signal and a disturbed signal, the smallest loop area and the shortest parallel path of the interference signal and the disturbed signal are ensured;

3) aiming at the regional arrangement of an interference source and a disturbed source, and the regional arrangement of a digital circuit, an analog circuit and a motor driving circuit;

4) key interference sources such as crystal oscillators, DSPs and the like are arranged near the center of the board;

5) for the auxiliary circuit, the core device of each functional circuit is taken as the center, and the layout is performed around the core device according to the principle of proximity;

6) interface protection circuits such as lightning protection circuits, power supply filter circuits, signal filter circuits and the like are closely adjacent to the connectors, so that the shortest wiring is realized and the connectors are arranged side by side;

7) the length of a short pin (shear flat welding) is required to be cut aiming at the filter capacitor of a specific chip and is close to the pin of the specific chip; when a plurality of capacitors are used for filtering, the smaller the capacitance value is, the closer the capacitance value is to the chip pin;

8) the series matching resistance of the crystal oscillator is close to the source end;

in the layout design of the PCB of the electric cylinder, the flow direction of an Ethernet communication signal enters from the connector assembly, and the Ethernet communication signal respectively passes through the interface protection circuit, the 58100 and the DSP and then returns from the DSP, the 58100, the protection circuit and the connector assembly; the AD acquisition signal passes through the connector, the interface protection circuit and the AD chip and is ended by the DSP; the motor driving signal is driven to the driving bridge by the DSP and the stepping motor driving chip and is finally output through the connector, and meanwhile, the driving bridge provides 36V servo power by the nearby connector.

The electric cylinder printed board adopts the layout design shown in fig. 11, ensures that each signal flow direction returns by a minimum path, realizes the regional arrangement of an interference circuit and a disturbed circuit, and reduces the electromagnetic compatibility and the external radiation in the board to the maximum extent.

And on the basis of layout completion, the wiring design of the electric cylinder printed board is carried out.

The printed board wiring design method of the electric cylinder comprises the following steps:

1) firstly, wiring high-speed signals, high-frequency signals, strong-power signals, sensitive signals and low-noise margin signals, and secondly, wiring other signals;

2) the wiring needs to avoid layer changing, when the wiring layer needs to be changed, the wiring layers on two sides of the same reference ground plane are selected as much as possible, and the reference ground plane is prevented from being changed;

3) if the wiring reference ground plane is from one ground layer to another ground layer, a ground via hole is needed to be arranged near the via hole of the wiring layer change to connect the two ground layers, and the size of the ground via hole is the same as that of the signal via hole, as shown in fig. 12;

4) strong interference sources, such as crystal oscillators, crystals and other devices, a local ground plane is paved below the devices, and the length and width of the local ground plane are larger than about 2mm of the devices; the local ground plane is connected with the stratum of the adjacent layer through a plurality of via holes; clock signals go to the inner layer; when the surface layer has to be walked, the maximum allowable length of the surface layer clock line is 1/20 of the wavelength of the clock signal, as shown in fig. 13;

5) the strong interference signal and the sensitive signal should be designed into a guard transmission ground wire, and the distance between the guard transmission ground wire and the protected signal is 3 times of the line width; the guard and transmission ground wire of the clock is connected with the stratum by punching holes every lambda/10; wherein λ is the wavelength of the clock signal;

6) high-speed signals or easily-disturbed signals cannot pass below devices such as a coil, a common mode inductor, an isolation transformer and an isolation operational amplifier;

7) the copper sheet of the ground wire is forbidden to extend out of redundant wire ends or suspended branch ground wires, so that the antenna effect is avoided;

8) when the signal differential pair or the power supply positive and negative wires are wired, the wire spacing is reduced as much as possible on the premise of meeting manufacturability. The loop area is reduced.

And finally, according to the division of the interference source and the interfered source, carrying out electromagnetic compatibility design check on the stratum, the layout and the wiring of the electric cylinder printed board, checking whether the printed board design meets the requirements of a corresponding method, if so, starting design iteration from the stratum again until the requirements are met, and finishing the electromagnetic compatibility PCB design of the electric cylinder.

Referring to fig. 14, the electromagnetic compatibility design method of the casing structure of the electric cylinder of the present invention is as follows;

because the controller shell of the electric cylinder has miniaturization requirement, the three-dimensional size of the shell is limited by the length, width and height of the control panel, and the wire distance and the clamp distance are reserved for ensuring manufacturability.

The printed board is laid in the shell, and the installation height of the printed board is limited by the height of the installed connectors.

Referring to fig. 15, the electromagnetic compatibility design method of the electric cylinder controller housing of the present invention is as follows:

1) the shell structure adopts a semi-surrounding design, and the front side cover and the rear side cover (ZY surface) are integrally formed with the bottom cover, so that two long-edge gaps (Z direction) are avoided, and the gap radiation is effectively reduced; the left side cover and the upper cover are detachable, the technological assembly requirements of a printed board and a connector are met, and the right side is a connecting part of the shell of the electric cylinder controller and the transmission part;

2) in order to ensure the shielding continuity, conductive rubber is designed and installed at the upper cover joint position (XY surface), the left side cover and the right side joint part (XZ surface); the installation is carried out in a slotted mode, and the installation position is shown in figure 16;

3) in order to avoid electromagnetic resonance in the shell and amplify internal interference signals, a back adhesive type wave-absorbing patch is adhered to the ZY surface of the wall of the machine box; the optimal working frequency band of the selected wave-absorbing patch is 1 GHz-4 GHz, and the full-band absorption performance is not lower than-10 dB;

4) the left side cover is provided with an externally connected connector, a Y50X series electric connector meeting the national military standard requirement is selected, and the tail cover of the connector can meet the process realization of 360-degree full shielding.

After the design is completed, whether all chassis routing is processed or not is checked, whether electromagnetic optimization is carried out on holes and seams formed by the shell or not is carried out, if the electromagnetic optimization is completed, the electromagnetic compatibility design of the electric cylinder structure is completed, and otherwise, the design flow is carried out again.

The electromagnetic compatibility electric cylinder can be used as an actuator of a large-caliber radio astronomical telescope active surface system.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical solution of the present invention, and it should be understood by those skilled in the art that the technical solution can be modified and replaced by a plurality of simple modifications and replacements without departing from the spirit and principle of the present invention, and the modifications and replacements also fall within the protection scope covered by the claims.

Claims

1. An electromagnetic compatibility design method of an electric cylinder is characterized by comprising the following steps:

s1, electromagnetic compatibility overall design of the electric cylinder;

planning from two aspects of a power supply form and a communication form; the power supply mode avoids the situation that a clock interference source is formed by a direct current/direct current conversion module added after power frequency 220V power supply is introduced into an electric cylinder, and meanwhile, power line harmonic interference introduced by the power frequency 220V power supply is avoided; the communication form can carry different communication protocols to realize networking requirements, and can avoid common mode radiation and differential mode radiation caused by copper wires;

2.2) carrying out principle level system distribution;

2.3) selecting a device with a composite function, and performing electromagnetic compatibility design optimization on an interference source and a disturbed source;

s3, designing an electromagnetic compatibility PCB of the electric cylinder;

3.1) designing a printed board layer;

3.2) designing the layout of devices on the printed board;

3.3) wiring design of the printed board;

2. The electromagnetic compatibility design method of the electric cylinder according to claim 1, characterized in that:

the signal cut-off frequency is calculated according to the following formula:

Then, calculating the cut-off frequency of the signal;

3. The electromagnetic compatibility design method of the electric cylinder according to claim 1, characterized in that:

4. The electromagnetic compatibility design method of the electric cylinder according to claim 1, characterized in that:

5. The electromagnetic compatibility design method of the electric cylinder according to claim 1, characterized in that:

the design principle of the step 3.1) comprises the following steps:

6. The electromagnetic compatibility design method of the electric cylinder according to claim 1, characterized in that:

7. The electromagnetic compatibility design method of the electric cylinder according to claim 1, characterized in that:

the wiring design method of the step 3.3) comprises the following steps:

8. An electromagnetic compatibility electric cylinder, characterized in that: the system is characterized in that direct current 28V input power is adopted, a physical medium of a communication network is optical fiber, a processor part takes a DSP as a core, an external circuit comprises a crystal oscillator circuit, a power supply management circuit and a reset circuit, a secondary power supply is designed according to a ground system and consists of a plurality of direct current/direct current converters and a direct current voltage stabilization source, an Ethernet communication module consists of an Ethernet protocol chip, a physical layer chip and an optical module, an analog quantity acquisition module consists of an analog quantity acquisition chip, and a motor driving module consists of a motor driving integrated chip and a field effect transistor driving bridge; aiming at different systems, primary power supply is distributed, and grounding points of the corresponding systems are kept isolated; the printed board layer utilizes the shielding cavity formed by the printed board layer to the maximum extent, the minimum area is formed for a signal loop, static grounds are designed around the printed board, the layout of devices ensures that all signal flow directions return by the minimum path, the arrangement of an interference circuit and a disturbed circuit in different regions is realized, and the electromagnetic compatibility and external radiation in the board are reduced to the maximum extent; the wiring avoids changing layers, when the wiring layers need to be changed, the wiring layers on two sides of the same reference ground plane are selected, and the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to the other stratum, a ground through hole is arranged near the through hole of the wiring layer change to connect the two stratums, the size of the stratum through hole is the same as that of the signal through hole, and a strong interference signal and a sensitive signal design shielding ground wire; the shell structure adopts a semi-surrounding design to meet the assembly requirement, and conductive rubber is installed to ensure the shielding continuity.

9. The electromagnetic compatibility electric cylinder according to claim 8, characterized in that: the same function is realized, and the number and the types of interference source devices are reduced by selecting multifunctional devices; the W5300 chip is selected to realize the functions of an Ethernet protocol chip and a physical layer chip;

10. A radio astronomical telescope active surface system is characterized in that: an electromagnetic compatible electric cylinder according to claim 8 or 9 is employed as an actuator of the active surface system.