CN111723543B

CN111723543B - Electromagnetic compatibility design method of electric cylinder, electromagnetic compatibility electric cylinder and application

Info

Publication number: CN111723543B
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: 2023-06-13
Anticipated expiration: 2040-06-18
Also published as: CN111723543A

Abstract

An electromagnetic compatibility design method for an electric cylinder, an electromagnetic compatibility electric cylinder and application thereof are provided, aiming at the characteristics of an electric cylinder product, the electromagnetic compatibility design method which runs through the original design of the electric cylinder is provided, and the forward electromagnetic compatibility design is realized. The design method comprises the overall electromagnetic compatibility planning of the electric cylinder, the electromagnetic compatibility design of the electric cylinder according to the electric principle, the electromagnetic compatibility design of the PCB of the electric cylinder and the structural electromagnetic compatibility design of the electric cylinder. The invention relates to an electric interference source and a disturbed source of an electric cylinder, which are identified, a principle-level system division is carried out according to the electric characteristics of the electric cylinder, the layout and wiring design of a printed board of the electric cylinder based on the signal flow direction, the static ground design of the printed board of the electric cylinder, the local ground plane design of a crystal oscillator and the semi-surrounding design of a shell structure of the electric cylinder.

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 an electromechanical output device for high-precision linear displacement and is widely applied to the fields of radio astronomy, machine tool control, medical appliances and the like. The electric cylinder subsystem is taken as an important component of the whole system, and the electromagnetic compatibility of the electric cylinder subsystem plays an important role in the stable operation of the whole system, so that the electromagnetic compatibility requirement of the electric cylinder is gradually severe. The conventional electric cylinder design includes an electric design, a structural design and a transmission design, but the electromagnetic compatibility design does not systematically penetrate through the electric cylinder design. Often after the electric cylinder product is debugged, the product is difficult to pass electromagnetic compatibility requirements when the electric cylinder product is subjected to electromagnetic compatibility assessment test. At the moment, electromagnetic compatibility modification can be carried out only through temporary measures, and the effect, manufacturability and aesthetic property after modification are not as good as those of a one-step molded product.

Disclosure of Invention

The invention aims to provide an electromagnetic compatibility design method of an electric cylinder, an electromagnetic compatibility electric cylinder and application thereof, which aim at solving the problem that the electric cylinder in the prior art is difficult to pass through the electromagnetic compatibility requirement after debugging, realize forward design of electromagnetic compatibility, effectively improve the electromagnetic compatibility of the electric cylinder product, avoid damaging the manufacturability and the aesthetic property of the product and reduce the development cost of the product.

In order to achieve the above purpose, the present 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 an electric cylinder;

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

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 driving;

2.1 Carrying out electromagnetic compatibility interference source and interfered source identification;

2.2 Principle-level system allocation;

2.3 Selecting a device with rich functions, and carrying out electromagnetic compatibility design optimization on an interference source and a disturbed source;

2.4 Electromagnetic compatibility filtering design is carried out on the interference source and the disturbed source;

2.5 Checking whether the indication adopted for the interference source and the interfered source is effective or not, if the indication is missing, returning to the step 2.2), re-executing the steps 2.2) to 2.4), and if the indication is covered in place, ending the design of the electromagnetic compatibility principle of the electric cylinder;

s3, electromagnetic compatibility PCB design of the electric cylinder;

3.1 A printed board layer design;

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 Device layout design on the printed board;

3.3 Wiring design of the printed board;

3.4 According to the interference source and the disturbed source, carrying out electromagnetic compatibility design inspection on the stratum, the layout and the wiring of the printed board of the electric cylinder, if missing, returning to the step 3.1), and re-executing the steps 3.1) to 3.3) until all the requirements are met;

s4, electromagnetic compatibility design of the electric cylinder shell comprises design of internal layout and wiring of the shell, design of a shell structure, design of hole and seam inhibition, and inspection of the wiring of the case and the hole and seam formed by the shell are finished.

Step 2.1) is to perform schematic diagram signal classification arrangement according to the following table:

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

if the signal time domain rise time τ is known, the signal cut-off frequency

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

Then reckoning the signal cut-off frequency according to the reckoning;

the identification method comprises the following steps: the signal power is high, the level is high, the cut-off frequency is high, and the signal is the strongest interference source of the single-ended signal; the signal is of low power and low level and is the most susceptible source of disturbance for single ended signals.

Step 2.2) the method for principle-level system allocation is as follows: the digital system ground, the analog system ground and the servo driving system ground are respectively kept in physical isolation; when two ground systems are interfered with each other but the ground plane needs the same static working point to work, the two ground systems are connected at nearby positions through magnetic beads except for physical isolation; when two ground systems are physically isolated according to the functional design requirements, but one of the ground systems can form a larger distributed capacitance, the two ground systems are closely connected through the capacitance.

Step 2.4) carrying out electromagnetic compatibility filtering design aiming at crystal oscillator as follows: decoupling capacitors are respectively designed at the power supply inlet 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 a magnetic bead L1 in series, the output end of the crystal oscillator is connected with RC filter 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 adopts even number; setting a larger area of pavement on the second layer or the penultimate layer; the ground plane remains intact; the number of sides of the polygon is reduced, and the convex polygon is better than the concave polygon; preferentially wiring on the inner layer; preferentially, wiring is carried out on the adjacent wiring layers, or although the adjacent wiring layers exist, the adjacent wiring layers are vertically wired or no wiring is arranged below the corresponding wiring area; the wiring layer of the key signal line is provided with an adjacent reference stratum, and the key wiring is ensured not to cross the ground partition;

in order to enable common mode interference on the printed board to be discharged through a low-impedance path and reduce external radiation efficiency on the printed board, static ground is designed around the printed board to form closed annular copper coating and realize electrical connection with the metal case;

the static design method comprises the following steps: each layer of the printed board is provided with a static land with the same shape; the static area cannot have other stratum, power supply layer and wiring signals; the width of the static land can not only drain the internal high-frequency noise, but also avoid interference from invading the inside of the printed board; the static ground is electrically connected with the metal shell by means of the fastening mode of the printed board structure, and the strength of the printed board is considered; the metal fastener of the on-board connector should be perforated in the quiet area and realize the electrical connection; if the PCB is designed with a metal shielding case, the length and the width of the metal shielding case are attached to the static ground, and the metal shielding case, the static ground and the metal shell are ensured to be electrically connected.

The device layout design method of the step 3.2) comprises the following steps: important components, strong radiation sources and sensitive sources are arranged in a preferential mode; the layout is carried out based on the layout idea of signal flow direction, so that the shortest wiring of the interference signal and the disturbed signal is ensured, the minimum loop area is ensured, and the parallel paths of the interference signal and the disturbed signal are shortest; the method comprises the steps of carrying out regional arrangement aiming at an interference source and a disturbed source, and carrying out regional arrangement on a digital circuit, an analog circuit and a motor driving circuit; a key interference source is placed near the center of the plate; for the auxiliary circuits, the core device of each functional circuit is taken as the center, and the auxiliary circuits are distributed around the core device of each functional circuit in a nearby principle; the interface protection circuit is closely adjacent to the plug-in unit, so that the shortest wiring is realized and the interface protection circuit is arranged side by side; cutting down the pin length of the filter capacitor aiming at the specific chip and closely adjacent to the pin of the specific chip; when the capacitors are filtered, the smaller the capacitance value is, the closer the capacitance value is to the chip pins; the series matching resistor 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, high-power signals, sensitive signals and low-noise-margin signals, and secondly, wiring other signals; the wiring avoids changing layers, and when the wiring layers are needed to be changed, the wiring layers on two sides of the same reference ground plane are selected, so that the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to another stratum, arranging a ground via near the via hole of the wiring exchange layer to connect the two strata, wherein the size of the ground via hole is the same as that of the signal via hole; the strong interference source is paved with a local ground plane below the device, the local ground plane is connected with the stratum of the adjacent layer through a plurality of through holes, and when a clock signal walks the inner layer and a surface layer is needed to walk, the maximum allowable surface layer clock line length is 1/20 of the clock signal wavelength; the strong interference signals and the easy sensitive signals are used for designing a protective ground wire, and the distance between the protective ground wire and the protected signal is 3 times of the line width; the protective ground wire of the clock is connected with the stratum at intervals of lambda/10 via holes, and lambda is the wavelength of the clock signal; the coil, the common mode inductor, the isolation transformer and the isolation operational amplifier device are not connected with high-speed signals or easily disturbed signals; the extra wire heads or suspended branch ground wires are forbidden to extend out of the ground wire copper sheet, so that antenna effect is avoided; when the signal differential pair or the power supply positive and negative wires are routed, 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 compatible electric cylinder at the same time, adopting direct current 28V input power supply, the physical medium of communication networking is optical fiber, the processor part takes DSP as core, the external circuit comprises crystal oscillator circuit, power management circuit and reset circuit, the secondary power supply consists of a plurality of direct current/direct current converters and direct current voltage stabilizing sources according to the design of the ground system, the Ethernet communication module consists of Ethernet protocol chip, physical layer chip and optical module, the analog quantity acquisition module consists of analog quantity acquisition chip as basis, and the motor drive module consists of motor drive integrated chip and field effect transistor drive axle; the primary power supply is distributed aiming at different ground systems, so that the ground points of the corresponding systems are kept isolated; the printed board layer maximally utilizes a shielding cavity formed by the printed board layer, forms a minimum area for a signal loop, designs a static ground around the printed board, ensures that each signal flow direction returns in a minimum path by device layout, realizes the regional arrangement of an interference circuit and a disturbed circuit, and maximally reduces the electromagnetic compatibility and external radiation in the board; the wiring avoids changing layers, and when the wiring layers are needed to be changed, the wiring layers on two sides of the same reference ground plane are selected, so that the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to another stratum, a ground via hole is arranged near a via hole of the wiring exchange layer to connect the two strata, the size of the ground via hole is the same as that of the signal via hole, and a protective ground wire is designed for strong interference signals and sensitive signals; the shell structure adopts semi-surrounding design to meet the assembly requirement, and conductive rubber is installed to ensure shielding continuity.

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

The front side cover, the rear side cover and the bottom cover of the shell are integrally formed, so that two long side gaps are avoided, and the radiation of the gaps is reduced; the left side cover and the upper cover are detachable, so that the process assembly requirements of the printed board and the connector are met, and the right side is the joint part of the shell of the electric cylinder controller and the transmission part; the upper cover joint position, the left side cover and the right side joint position are embedded with conductive rubber in a slotting mode; the back adhesive type wave absorbing patch is adhered to the wall surfaces of the front side cover and the rear side cover of the shell, the left side cover is provided with a connector which is externally connected, 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, which adopts the electromagnetic compatible electric cylinder as an actuator of the active surface system.

Compared with the prior art, the invention has the following beneficial effects: the electromagnetic compatibility design method of the electric cylinder is organically integrated into the traditional functional design of the electric cylinder product, comprises electromagnetic compatibility overall planning of the electric cylinder, electromagnetic compatibility design flow of an electric principle of the electric cylinder, PCB electromagnetic compatibility design flow of the electric cylinder and structural electromagnetic compatibility design flow of the electric cylinder, and aims at the characteristics of the electric cylinder product, stands at an electromagnetic compatibility angle and considers the characteristics of the electric cylinder, and the systematic electromagnetic compatibility design method penetrating through the functional design of the electric cylinder product is provided, so that the forward design of electromagnetic compatibility is realized, the electromagnetic compatibility of the electric cylinder product is effectively improved, the manufacturability and the attractiveness of the product are avoided, the development cost of the product is effectively reduced, and the electric cylinder product is convenient and feasible and has higher application value.

Furthermore, a special filtering design method is provided for the crystal oscillator in the electric cylinder control board, a topological structure of parallel three-stage capacitance filtering and serial magnetic beads is adopted for crystal oscillator power supply, and meanwhile, RC network filtering is carried out for clock signal output; the design method of the local ground plane is proposed for wiring of radiation devices such as crystal oscillator 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 land design method, a static land position and size design method and a static land placement relation with other devices in the electric cylinder control panel; the electric cylinder printed board is based on the ideas of layout and wiring of signal flow direction, the signal flow direction is induced according to the circuit characteristics of the electric cylinder product, layout design is carried out according to the rule that the signal flow direction is shortest and the loop area is smallest, the complete electromagnetic compatibility link is organically integrated, and the electromagnetic compatibility of the electric cylinder product is improved.

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

Drawings

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

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

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

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

FIG. 5 presents a circuit diagram of a special filter design for a crystal oscillator;

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

FIG. 7 is a schematic diagram of the connection of magnetic beads;

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

FIG. 9 is a schematic diagram of a layout of lands around a printed board;

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

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

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

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

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

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

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

Detailed Description

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

Referring to fig. 1, an electric cylinder is an electromechanical device that uses electric energy to achieve high-precision linear displacement feeding. The design content for the electric cylinder comprises an overall design, an electric design, a controller structure design and a transmission design.

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

The electric design is to realize communication response to the control instruction of the upper computer, collect the position and feed back by the sensor, realize the closed-loop control strategy on the DSP and finally realize the power output of the controller to the motor.

Structural design refers to the controller housing design.

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

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

1. Electromagnetic compatibility overall planning of the electric cylinder;

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

2. An electric principle electromagnetic compatibility design of the electric cylinder;

the realization block diagram combined with the function design principle of the electric cylinder shows that the electric part consists of a processor, a secondary power supply, ethernet communication, analog acquisition, motor driving 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 consists 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 consists of an Ethernet protocol chip (Mac), a physical layer chip (PHY) and an optical module, wherein the Ethernet communication comprises a crystal oscillator circuit. The analog quantity acquisition is based on an analog quantity acquisition chip (AD). The motor drive mainly comprises a motor drive integrated chip and a field effect transistor (MOS tube) drive axle. Referring to fig. 2, a design flow of the electromagnetic compatibility principle of the electric cylinder is proposed.

According to the flow, firstly, identifying an electromagnetic compatibility interference source and a disturbed source.

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 signal time domain rise time τ is known, the signal cut-off frequency

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

And then calculates the signal cut-off frequency.

The identification method comprises the following steps: the signal power is high and the level is high and the cut-off frequency is high and is the strongest interference source of the single-ended signal, and the signal power is low and the level is low and is the most sensitive interference source of the single-ended signal. And vice versa.

After the electrical system is evaluated by the method, the interference source is a crystal oscillator circuit and a linear sensor input signal. The disturbed source is an AD acquisition circuit. In order to avoid that signals with different powers and different levels form ground bullets on a public loop, digital quantity misjudgment or analog quantity performance degradation is caused, and principle-level system distribution is carried out.

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 are interfered with each other but the ground plane needs the same static working point to work, the two ground systems are connected at nearby positions through magnetic beads except for physical isolation; when two ground systems are physically isolated according to the functional design, but one of the ground systems (generally referred to as the chassis ground) can form a larger distributed capacitance, the two ground systems are closely connected by the capacitance. According to the principle-level system design method and by combining with the control system electricity utilization practice, the following scheme is planned, as shown in fig. 3:

wherein GND is the ground of a chip such as DSP, mac, PHY, AGND is the ground of analog quantities such as a displacement sensor, a temperature sensor and the like, 36VGND is the ground of a stepping driving chip, a driving axle and a stepping motor, and EGND is the ground of a shell.

For different ground systems, the primary power supply is distributed by adopting an isolated DC/DC, so that the corresponding ground points of the system are kept isolated. If analog quantity interaction exists between different systems, the analog quantity interaction is realized by adopting isolation devices such as an isolation operational amplifier (e.g. ISO 124), an optical coupler (e.g. HCNR 201) and the like. If digital quantity interaction exists between different systems, a digital isolator (such as an ADuM 2400), an isolation transformer and the like are adopted to realize the digital quantity interaction.

Meanwhile, the design of the connection relation between the ground systems is shown in fig. 3:

the magnetic beads of 500 Ω are connected with GND and AGND when the frequency of L1 is 100MHz, so that the common mode interference is inhibited, and meanwhile, the AD acquisition chip (AD 7606) is ensured to share a direct current working point. Since the frequency range of the motor driving signal reaches 100kHz, the frequency range is estimated according to a time constant formula: τ=rc, C is 10 μf, and 1 Ω is estimated for R; because the working frequency of the digital system is covered from 25MHz to 1GHz, 1GHz is taken for calculation, and 1000pF is taken according to a time constant formula, so that the surface-mounted capacitor is obtained; theory and actual measurement show that: the sensor external cable can couple the interference electromagnetic wave with the frequency of 100 MHz-500 MHz (the external displacement sensor is a plastic shell, the shielding cable is difficult to realize full shielding contact), and the amplitude is continuous in the range, as the simulation ground is connected to the external linear sensor through the external wiring cable, the C3 takes the 10nF surface-mounted capacitor according to the time constant formula.

The principle-level electromagnetic compatibility optimization is performed on the interference source and the disturbed source.

First, it is pointed out that: the equivalent function is realized, and devices with rich functions are selected so as to reduce the number of interference sources such as crystal oscillators, interface isolators and the like. The high-integration and multifunctional chip has excellent electromagnetic compatibility performance compared with a circuit realized by a separation type function, because the high-integration chip has a shorter wiring distance and a flexible packaging form. Therefore, in the electrical system, in order to realize Ethernet communication, the electromagnetic compatibility of a single chip integrated with Mac and PHY functions is better than that of two chips (the wiring length of a high-speed signal on a printed board is effectively avoided, and radiation is reduced), so that the Mac and PHY functions are realized by using a W5300 chip.

The unused chip input/output signals cannot be suspended and should be grounded through low impedance.

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

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

The crystal oscillator generates a periodic clock and simultaneously causes switching noise on a ground loop to influence the integrity of a power supply. Decoupling capacitors (C1, C2 and C3) are respectively designed at the power supply inlet of the crystal oscillator, wherein the capacitance value of C1 is 4.7 mu F, and a tantalum electrolytic capacitor is selected; wherein the capacitance value of C2 is 0.1 mu F, and a plurality of layers of porcelain capacitors are selected; the capacitors are all surface-mounted capacitors, so that ESL (series equivalent inductance) and ESR (series equivalent resistance) are effectively reduced, wherein the capacitance value of C3 is 0.01 mu F, and meanwhile, the magnetic beads L1 are connected in series, and the magnetic beads of 200 omega at 100MHz are selected. The periodic clock generated by the crystal oscillator is not a perfect square wave, but is the superposition of limited times of harmonic waves, and in practice, the overshoot of the waveform is too large to indicate that the circuit has larger reflection, as shown in fig. 6, so that RC filtering is connected in series at the output end of the crystal oscillator, and C4, R1 and C4 are designed by selecting a plurality of layers of porcelain dielectric surface-mounted capacitors and selecting 10 pF; r1 is designed as a surface-mounted resistor, the resistance is generally 22-51 omega, and meanwhile, the resistance is optimized according to the actual PCB debugging waveform.

The magnetic beads can be equivalently connected in series with the inductor and the resistor, have obvious effect on high-frequency interference suppression, and can be surface-mounted and through-hole-inserted due to flexible packaging form. Therefore, in the principle design of the electric cylinder control board, the magnetic beads can be connected in series to inhibit the interference generated during the transmission of the high-frequency signals; the inhibition of the interference introduced to the external single-ended interface is also solved by the serial magnetic beads.

For the interference signal of the linear sensor, serial magnetic beads on the signal line are selected to inhibit common mode interference. The characteristic of the selected magnetic bead is 500 omega when the magnetic bead is 100MHz, and the self-resonance frequency is more than 800Mhz. The connection is shown in fig. 7.

The arrangement and timing of the connector point positions are suggested to be staggered with the signal pins.

Finally, checking whether effective measures are adopted for the interference source and the interfered source. If the missing exists, the flow design is carried out again; if all the cover is in place, the design of the electromagnetic compatibility principle of the electric cylinder is finished.

The design measures for the AD acquisition chip of the sensitive device are ensured by the design of the ground system.

3. PCB electromagnetic compatibility design of the electric cylinder;

after the electric principle of the electric cylinder is designed, a circuit board diagram is formed through PCB design, and square energy engineering is realized. Therefore, an electromagnetic compatibility PCB design flow of the electric cylinder is proposed.

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

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

1) The electromagnetic compatibility of the multi-layer printed board is obviously better than that of a single-layer printed board;

2) The number of layers adopts even number;

3) Setting a large-area pavement on the second layer or the penultimate layer;

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

5) If the ground plane cannot remain rectangular for manufacturability, etc., the number of sides of the polygon is reduced as much as possible. Moreover, the convex polygon shape is better than the concave polygon shape;

6) Preferentially wiring on the inner layer;

7) Preferentially, wiring is carried out on the adjacent wiring layers, or although the adjacent wiring layers exist, the adjacent wiring layers are vertically wired or no wiring is arranged below the corresponding wiring area;

8) The routing layers of the critical signal lines should have adjacent reference strata and ensure that the critical traces are not segmented across the region.

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

layer optimization design of six layers: S1/G1/S2/P/G2/S3;

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

layer optimization design of the ten-layer plate: 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 layer;

the design of the upper layer accords with the design method of the printed board layer, maximally utilizes the shielding cavity formed by the printed board layer, and forms the minimum area 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, the external radiation efficiency on the printed board is reduced, a 'static ground' is designed around the printed board, a closed annular copper coating is formed, and the closed annular copper coating is fastened with a metal chassis through a plurality of structural screws to realize electrical connection.

The static land design method of the invention is as follows:

1) Each layer of the printed board is provided with a static land with the same shape;

2) The static area cannot have other stratum, power supply layer and wiring signals;

3) The width of the static land is generally 2 mm-7 mm, so that the internal high-frequency noise is discharged, and the interference of external lightning and the like can be avoided from invading the inside of the printed board;

4) The static place is electrically connected with the metal shell by means of structural fastening modes such as printed board mounting screws, and the like, and the printed board is generally fastened by at least using 6-8 screws in consideration of the strength of the printed board; the screw holes are all metallized holes;

5) Positional relationship of board connector and land referring to fig. 9, the metal fastener of the board connector should be perforated in the land area and electrically connected by screws;

6) If the PCB needs to be designed with a 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 design of the printed board of the electric cylinder, a static design shown in fig. 9 is adopted, and the static width is selected to be 5mm.

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

1) The layout principle of 'big before small, difficult before easy', 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 wiring of the interference signal and the disturbed signal is ensured, the minimum loop area is ensured, and the parallel paths of the interference signal and the disturbed signal are shortest;

3) Aiming at the regional arrangement of an interference source and a disturbed source, a digital circuit, an analog circuit and a motor driving circuit are arranged in a regional manner;

4) The key interference sources such as crystal oscillator, DSP and the like are placed near the center of the plate;

5) For the auxiliary circuits, the core device of each functional circuit is taken as the center, and the auxiliary circuits are distributed around the core device of each functional circuit in a nearby principle;

6) Interface protection circuits, such as lightning protection circuits, power supply filter circuits, signal filter circuits and the like, are closely adjacent to the plug-in units, realize the shortest wiring and are arranged side by side;

7) The filter capacitor aiming at the specific chip should be cut to short pin length (cut flat welding) and be close to the pin of the specific chip; when the capacitors are filtered, the smaller the capacitance value is, the closer the capacitance value is to the chip pins;

8) The serial matching resistor of the crystal oscillator is close to the source end;

in the PCB layout design of the electric cylinder, the Ethernet communication signal flow direction enters from the connector, respectively passes through the interface protection circuit, 58100 and the DSP, and then returns from the DSP, 58100, the protection circuit and the connector; the AD acquisition signal passes through the connector, the interface protection circuit and the AD chip until the end of the DSP; the motor driving signal is output from DSP and step motor driving chip to the driving bridge, and the driving bridge is provided with 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 in a minimum path, realizes the regional arrangement of an interference circuit and a disturbed circuit, and reduces the electromagnetic compatibility and external radiation in the board to the greatest extent.

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

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

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

2) The wiring is required to avoid layer replacement, and when the wiring layers are required to be replaced, the wiring layers on two sides of the same reference ground plane are selected as much as possible, so that the reference ground plane is prevented from being changed;

3) If the wiring reference ground plane is from one formation to another, then a ground via must be provided adjacent to the wiring level change via to connect the two formations, the formation via size being the same as the signal via size, as shown in FIG. 12;

4) The strong interference source such as a crystal oscillator, a crystal and other devices is formed by paving a local ground plane below the devices, and the length and width dimensions of the local ground plane are larger than those of the devices by about 2mm; the local ground plane is connected with the stratum of the adjacent layer through a plurality of through holes; the clock signal goes through the inner layer; when the surface layer must be walked, the maximum allowed surface layer clock line length is 1/20 of the clock signal wavelength, as shown in fig. 13;

5) The strong interference signal and the easy sensitive signal should design the protective ground wire, the distance between the protective ground wire and the protected signal is 3 times of the line width; the protective ground wire of the clock is connected with the stratum by punching through holes at intervals of lambda/10; where λ is the wavelength of the clock signal;

6) High-speed signals or easily disturbed signals cannot be transmitted below devices such as a coil, a common-mode inductor, an isolation transformer, an isolation operational amplifier and the like;

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

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

Finally, according to the division of the interference source and the disturbed source, carrying out electromagnetic compatibility design inspection on the stratum, the layout and the wiring of the printed board of the electric cylinder, checking whether the design of the printed board meets the requirements of the corresponding method, if the design is omitted, starting design iteration from the stratum again until the design meets the requirements, and ending the electromagnetic compatibility PCB design of the electric cylinder.

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

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

The printed board is laid in the shell in a flat mode, and the installation height of the printed board is limited by the flush of the installation connector.

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, the front side cover, the rear side cover (ZY surface) and the bottom cover are integrally formed, two long side gaps (Z direction) are avoided, and the radiation of the gaps is effectively reduced; the left side cover and the upper cover are detachable, so that the process assembly requirements of the printed board and the connector are met, and the right side is the joint part of the shell of the electric cylinder controller and the transmission part;

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

3) In order to avoid electromagnetic resonance in the shell, amplifying internal interference signals, and sticking a back adhesive type wave-absorbing patch on the ZY surface of the chassis wall; the optimal working frequency band of the selected wave-absorbing patch is 1 GHz-4 GHz, and the absorption performance of the full frequency band 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 army standard requirement is selected, and the tail cover can meet the full shielding process of 360 degrees.

After the design is finished, checking whether all chassis wires are processed, performing electromagnetic optimization on holes and slots formed by the shell, if so, finishing electromagnetic compatibility design of the electric cylinder structure, otherwise, re-performing the design flow.

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

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the technical solutions of the present invention in any way, and it should be understood by those skilled in the art that the technical solutions may be modified and replaced in several ways without departing from the spirit and principle of the present invention, and these modifications and substitutions are also included in the protection scope of 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 an electric cylinder;

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

2.2 Principle-level system allocation;

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

s3, electromagnetic compatibility PCB design of the electric cylinder;

3.1 A printed board layer design;

3.2 Device layout design on the printed board;

3.3 Wiring design of the printed board;

s4, electromagnetic compatibility design of the electric cylinder shell comprises design of internal layout and wiring of the shell, design of a shell structure, and design of hole and seam inhibition, wherein the inspection of the wiring of the case and the hole and seam formed by the shell is completed;

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:

if the signal time domain rise time τ is known, the signal cut-off frequency

Then calculating the signal cut-off frequency;

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:

selecting a multi-level printed board; the number of layers adopts even number; setting a large-area pavement on the second layer or the penultimate layer; the ground plane remains intact; the number of sides of the polygon is reduced, and the convex polygon is better than the concave polygon; preferentially wiring on the inner layer; preferentially, wiring is carried out on the adjacent wiring layers, or although the adjacent wiring layers exist, the adjacent wiring layers are vertically wired or no wiring is arranged below the corresponding wiring area; the wiring layer of the key signal line is provided with an adjacent reference stratum, and the key wiring is ensured not to cross the ground partition;

6. 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:

firstly, wiring high-speed signals, high-frequency signals, high-power signals, sensitive signals and low-noise-margin signals, and secondly, wiring other signals; the wiring avoids changing layers, and when the wiring layers are needed to be changed, the wiring layers on two sides of the same reference ground plane are selected, so that the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to another stratum, arranging a ground via near the via hole of the wiring exchange layer to connect the two strata, wherein the size of the ground via hole is the same as that of the signal via hole; the strong interference source is paved with a local ground plane below the device, the local ground plane is connected with the stratum of the adjacent layer through a plurality of through holes, and when a clock signal walks the inner layer and a surface layer is needed to walk, the maximum allowable surface layer clock line length is 1/20 of the clock signal wavelength; the strong interference signals and the easy sensitive signals are used for designing a protective ground wire, and the distance between the protective ground wire and the protected signal is 3 times of the line width; the protective ground wire of the clock is connected with the stratum at intervals of lambda/10 via holes, and lambda is the wavelength of the clock signal; the coil, the common mode inductor, the isolation transformer and the isolation operational amplifier device are not connected with high-speed signals or easily disturbed signals; the extra wire heads or suspended branch ground wires are forbidden to extend out of the ground wire copper sheet, so that antenna effect is avoided; when the signal differential pair or the power supply positive and negative wires are routed, the wire spacing is reduced and the loop area is reduced on the premise of meeting manufacturability.

7. An electromagnetic compatibility electric cylinder, which is characterized in that: the direct current 28V input power supply is adopted, the physical medium of the communication networking is an optical fiber, the processor part takes a DSP as a core, the external circuit comprises a crystal oscillator circuit, a power management circuit and a reset circuit, the secondary power supply consists of a plurality of direct current/direct current converters and direct current voltage stabilizing sources according to the design of a ground system, the Ethernet communication module consists of an Ethernet protocol chip, a physical layer chip and an optical module, the analog quantity acquisition module consists of an analog quantity acquisition chip as a base, and the motor driving module consists of a motor driving integrated chip and a field effect transistor driving bridge; the primary power supply is distributed aiming at different ground systems, so that the ground points of the corresponding systems are kept isolated; the printed board layer maximally utilizes a shielding cavity formed by the printed board layer, forms a minimum area for a signal loop, designs a static ground around the printed board, ensures that each signal flow direction returns in a minimum path by device layout, realizes the regional arrangement of an interference circuit and a disturbed circuit, and maximally reduces the electromagnetic compatibility and external radiation in the board; the wiring avoids changing layers, and when the wiring layers are needed to be changed, the wiring layers on two sides of the same reference ground plane are selected, so that the reference ground plane is prevented from being changed; if the wiring reference ground plane is from one stratum to another stratum, a ground via hole is arranged near a via hole of the wiring exchange layer to connect the two strata, the size of the ground via hole is the same as that of the signal via hole, and a protective ground wire is designed for strong interference signals and sensitive signals; the shell structure adopts semi-surrounding design to meet the assembly requirement, and conductive rubber is installed to ensure shielding continuity.

8. The electromagnetic compatible electric cylinder according to claim 7, characterized in that: the same function is realized, and the number and the types of interference source devices are reduced by selecting the multifunctional devices; the W5300 chip is selected to realize the functions of an Ethernet protocol chip and a physical layer chip;

9. An active surface system of a radio astronomical telescope is characterized in that: use of an electromagnetic compatible electric cylinder according to claim 7 or 8 as an actuator for an active surface system.