flight controller hardware structure and circuit2

Comparing uav remote sensing satellites and manned aircraft platform, has the characteristics of low cost, high flexibility.In order to satisfy the science remote sensing experiment, remote sensing work task, coordination of unmanned aerial vehicle (uav) multiple components in electronic pod working posture, control, remote sensing image sensor,System AT89S52 as the main control chip, expand multi-channel serial and USB interface so as to realize the communication system and peripheral equipment, and design the camera driver module and three dof stepping motor driver module.Through the uav remote sensing experiment proves that the system can satisfy the requirement of remote sensing experiment.

USB extension circuit design

USB extension by CH375 chip implementation.The general interface chip CH375 is the USB bus.Its main characteristic is cheap, convenient interface and high reliability.Support USB - HOST HOST way and way of USB DEVICE/SLAVE DEVICE.CH375 commonly used way of USB host support USB device at full speed, the external need to write the firmware program MCU in accordance with the relevant USB protocol and USB communication.But for common USB Storage devices, CH375 built-in firmware can automatic processing Mass - Storage Mass Storage equipment dedicated communication protocols,Normally, the external microcontroller don't need to write the firmware program. Can directly read and write data from USB storage devices.CH375 and MCU communication there are two ways: parallel and serial mode.USB extension circuit principle diagram as shown in figure 3, CH375 chip set to the built-in firmware mode, use 12 MHz crystal.SCM P0 port connected with the CH375 D0 ~ D7 as a data bus, decoder output connected pieces selected the chip CH375, microcontroller A0 and CH375 A0 is linked together, the choice of CH375 address and data input and output.When A0 to high level is the address of the transmission is D0 ~ D7, low electricity at ordinary times is the data transmission.P3.6 and P3.7 control of CH375 to read and write operation respectively.MCU input CH375, when there are data input through the USB port the interrupt signal, notify the single-chip computer for data processing.When CH375 chip initialization and successfully connected with the master, indicator.

Stepper motor drive circuit

Stable yuntai control three degrees of freedom for stepper motor control, the control of the remote sensing sensor pitch Angle, roll Angle and course Angle to keep stable yuntai horizontal (or vertical) state.Stepping motor driven by THB6128 chip implementation, microcontroller only output step motor running direction and the pulse signal can achieve the goal of control of stepping motor.

THB6128 is high subdivision, special chip two-phase hybrid stepping motor driver output control signal by single chip microcomputer, can design a high performance, multiple subdivision drive circuit.Its characteristics for both bridge MOSFET drive, low on resistance Ron Ω = 0.55, the highest 36 V voltage, large current 2.2 A (peak), A variety of optional segment, up to 128 segments, half with automatic locking function, fast, slow decline, optional hybrid three decay modes, built-in temperature protection and over-current protection.Figure 4 for the heading Angle of stepper motor drive circuit, pitch Angle and roll Angle of the stepper motor driver with the same.Figure in the CP1 and U/D of single chip microcomputer is given respectively drive pulse with the motor running direction of control signal.M1, M2, and M3 for motor drive fine points selection signal input, controlled by the dial the code switch artificially.FDT1 and VREG1 attenuation model respectively to choose voltage and current control voltage input end.When 3.5 V for slow attenuation model;When the attenuation model for mixed;When FDT1 "0.8 V for fast attenuation model. Adjust the voltage of the VREG1 can set stepper motor drive current value.

flight controller hardware structure and circuit1

In the uav flight control system, flight controllers is its core component,It is responsible for the flight control system of signal acquisition, calculation of control law, the posture and speed of the aircraft, and the communication with ground equipment, etc.As uavs become more widely used, its task is becoming more and more complex, and mobility requirements for unmanned aerial vehicle (uav) is becoming more and more high, this request of unmanned aerial vehicle (uav) control core to develop in the direction of high integration and miniaturization.

In a 586 - Engine embedded chip as the core, the design of a certain type of unmanned aerial vehicle (uav) flight controller, system hardware structure is introduced and the corresponding software flow, and the simulation results is presented.

The 586 - Engine main parameters as follows:

• for 32-bit AMD CPU Elan SC520, frequency of 133 MHZ;
• the high performance of floating point arithmetic unit, support complex operations, such as sine, tangent, logarithmic, very suitable for need to the application of complex operations.
• the configuration 512 KB SRAM, 512 KB of Flash, 114 bytes in the internal RAM;
• support 15 external interrupt.A total of seven timer, including internal a programmable timer, provide 3 16-bit internal timer and 3 16 GP timers, plus a software timer.The timer support external event timing and counting.Software timer provides microsecond time hardware benchmark.
• provide 32 programmable I/O, 2 UART.A total of 19 road 12 bit A/D input, including 11 parallel ADC ADC serial input and 8 road, switching frequency is 300 KHZ;No.6 D/A output, including two serial output DAC and four output parallel 12 bit DAC, switching frequency is 200 KHZ.
• working temperature for - 40 ℃ ~ 80 ℃, the size of 91.4 mm&Times;4 mm&Times;7.6 mm.

The type of unmanned aerial vehicle (uav) is to provide communications relay for navy combat troops use medium wheeled unmanned aerial vehicle (uav), the flight controller is a separate packing small airborne electronic equipment,By DC/DC DC power conversion board, the computer motherboard, analog channel plate, the switch quantity of channel plate and steering gear control board,All templates by bus on the motherboard connection, to reduce the size, improve the level of integration.

Detailed below flight controllers of data collection, information transmission and control output, etc.

(1) serial port extension

The figure 1 shows that the flight controller needs with GPS, magnetic heading of communication and radio altimeter, a total of five serial port.586 - Engine motherboard only provide two serial ports, respectively for the use of ground test and measurement and control stations, so the need for a serial port extension.A serial port extension circuit is shown in figure 3.

Serial port extension circuit adopts the TL16C754 UART and four channels - string conversion device, the 8-bit parallel data into serial output 4 road, plus MAX202 and MAX489 level conversion chip, expanded the 2 RS232 serial interface and 2 RS422 serial port, can meet the hardware requirements of flight controller.

• D/A conversion

The uav using simulated steering gear, A total of 6 D/A channel PWM signals to drive the servo.586 - Engine motherboard provides 8 D/A, A total of 4 road 12 parallel D/A (DA7625) were about to rise and fall control steering gear, the aileron servo and the direction of steering gear, 2 road 12 serial D/A (LTC1446) front wheel steering and throttle servo control.Because DA7625 output voltage in the range of 0 ~ 2.5 V, LTC1446 output voltage range of 0 ~ 4.096 V, and steering gear working voltage for - 10 ~ 10 V, so need to signal amplification and translation.D/A level translation circuit as shown in figure 4.

Level by the figure, the D/A conversion principle is adopted in op-amp input addition circuit, the input signal and the reference level proportion together, get the voltage range suitable for sampling.Input level

and the relationship between the output leve

• A/D acquisition

586 - Engine motherboard own 19 road 12 bit A/D interface completely meet the accuracy requirement of the channel number and the transformation of A flight control system, the A/D interface of barometric altimeter data respectively, uav airborne voltage, Engine speed and temperature, the throttle opening and so on.These signals sent to the ground tt&c computer for operators for unmanned aerial vehicle (uav) working state monitoring provides the basis.

• the I/O control

586 - Engine motherboard provides 32 16 programmable digital I/O port, used for acquisition, umbrella compartment open the Engine starting signal, etc., and the output switch signal control and other equipment, take-off and recycling process control of unmanned aerial vehicle (uav).

• power supply module

Flight controller of power supply module circuit for flight controllers provide a clean and stable power supply voltage, used to guarantee the normal work of the flight controllers.Power supply module circuit design is good or not directly affect the flight controller running stability and reliability.Due to the size of the unmanned aerial vehicle has certain requirements, at the same time, considering the reliability and cost, so use in the design of the mature standard module power supply, external work with little or no device.Flight controllers of power supply module circuit is shown in figure 5.

Among them, with 24 t05d12 module power as the main chip of the power supply circuit, provided by the power of 30 w, input voltage range to 18 v ~ 36 v, output power has three road: + 5 v and + 12 v, the power supply for airborne sensors and steering gear.

Made of led light circuit diagram

1,Figure 1 is for capacitance ballast circuit.The C1 Values determine the size of the working current .Working current normally is 12mA-15mA,and Within this scope LED is safe.We can cancel R2,C3 according to the situation .
2, Figure 2 is for the constant current source circuit.The R3 Values determine the size of the working current .When it is 30Ω,the Working current is 12mA.The VT1 voltage at the ends of the collector and emitter=the voltage for the two ends of C2 -The LED pressure drop*N .More the quantity of LED the is , lower VT need resistance to pressure and power.When the quantity of LED the is more ,We can use MJ13001 for VT1.
3, If the quantity of LED the is less ,We can use Figure 1 circuit .While the quantity of LED the is more ,We can use Figure 2 circuit .In terms of cost performance, Figure 2 circuit is the first selection.
4, The quantity of LED the is more ,the higher the energy utilization efficiency is .For example,Working current normally is 15mA(This value not only can make sure the brightness ,but also make sure the LED security)However the quantity is 1 or 90,Electric current is equal because led is In series .The power of the circuit P=220V*1.414*0.015A=4.67W.If 10 LED is used,and the pressure drop is 3.1V,then the power is 10%.While the rest is lost on the ballast or constant current source .But if 90LED is used,then the power will up to 90% .So it’s better to use more LED ,which can increase brightness In proportion,reduce the financial burden on the power part and Increase the reliability.
5, Leds classified two types :concentrated and astigmatism .For the concentrated type,Brightness is concentrated , range is far but it has a halo,which is applicable to the emergency light, flashlight, etc.While for astigmatism type ,Brightness is Scattered and soft,but it own a shorter distance,which is suitable for indoor lighting, desk lamp, etc. (can be mixed with a certain amount of concentrating)
6, There is a trick to choose LED:The bigger Light emitting chip ( visible phosphors in the LED)is ,the brighter the light will be .

PCB design relevant skills

Set skills 
All point design in different stage requires different Settings,
In the layout phase a large lattice can be used in device layout;For big components such as IC, connectors which are not located, we can choose 50 ~ 100 mil lattice accuracy to device layout .While for passive components such as resistance capacitance and inductance,we can choose 25mil.he precision of the large lattice is advantageous to the alignment of the device and the layout beautiful.
PCB layout rules:
1, Normally all components shall be arranged on the the same circuit board side.Only top-level components is too close, some device height is limited and small calorific value device be set up on the bottom ,Such as SMD resistor, SMD capacitors, SMD IC.
2, on the premise of guarantee the electrical performance,elements should be placed on the grid in parallel or vertical alignment in order to be neat, beautiful.In general we don't allow components overlap,but to compact arranged components .Components in the page layout should be uniform distribution, the density is consistent .
3,Different components on printed circuit boards, neighboring,and the minimum distance between solder graphics should be more than 1 mm .
4,The distance from Components to the circuit board edge is generally not less than 2 mm.The best shape for the circuit board is rectangular and aspect ratio is 3:2 or 4:3. When Circuit board face 'is greater than 200 mm by 150 mm, we should consider mechanical strength which circuit board can withstand .
Layout skills
In the layout of the PCB design to we should analyze circuit unit according to the function.Layout all the components of the circuit , we need to comply with the following principles:
1, Arrangement of each functional circuit unit according to the process of the circuit to facilitate signal flow and ss far as possible to maintain the signal consistent direction.
2,Centered on the core of each function unit components, we layout around it .The arrangement of components should be uniform, compact, on the PCB and we should as far as possible reduce and shorten the lead and the connection between each components.
3,For the circuit which works under high frequency , we need to consider the components distribution parameters.Generally components should be as far as possible made parallel arrangement ,which are beautiful, and easy fabrication, easy to mass production .

Method for quickly detecting fault of PCB board

PCB board production is not a simple process to finish the board, and drill a hole. PCB production is not difficult, the difficulty lies in the completion of the troubleshooting. Whether it is a personal enthusiast or industry engineer, for the PCB circuit board debugging problems encountered when it is also quite a headache, like programmers encounter BUG. Common problems in addition to circuit board design, electronic components of the damage, circuit short circuit, the quality of components, PCB circuit board disconnection fault is not a minority.

Common circuit board fault is mainly concentrated on the components above, like capacitors, resistor, inductor, diode, transistor, FET, integrated chip with obvious damage of the crystal, and the method of judging these components fault more intuitive through the eyes to see. There are obvious damage to the surface of electronic components have more obvious traces of burning. Like this kind of fault, the problem can be solved by replacing the new component.

Of course, not all of the electronic components damage can be observed with the naked eye, resistance, capacitance, as mentioned above, two or three diodes, and in some cases the damage is not from the surface to see, the need for maintenance by professional inspection tools, commonly used for inspection with multimeter, capacitance meter etc. and electronic components to a voltage or current in the normal range in the detection, the components or previous components problems, then check to see if the normal direct replacement. 

But sometimes when we give PCB board components, will encounter the problem is not detected, but the circuit board and can not be operated normally. Many novice encounter such problems MEIZHE, only to re do a board, or buy a piece of. In fact, in this case, a lot of time in the process of installation of components, due to the coordination of the various components of the problem, there may be unstable performance. In this case, the instrument has been unable to help, try to determine the range of possible fault, according to the current and voltage to reduce, experienced engineers may be able to determine the fault area quickly, but the specific components which can not determine the bad 100%. The only way to do this is to try to replace the suspect until you find the problem.

The above said is the electronic components of the problem, of course, since the PCB circuit board as components, so the circuit board fault must also exist, the most simple example of die tin parts, due to the production process, the PCB corrosion process, there may be a problem is broken. In this case, if you can not make up the line, then you can only use fine copper wire.

FPC hole metallization and copper foil surface cleaning process

* Fabrication technology of double sided FPC

The hole metallization of flexible printed circuit board is basically the same as that of rigid printed circuit board. In recent years, there has been a direct plating process, which is replaced by electroless plating and the formation of carbon conductive layer technology. This technique is also introduced in the fabrication of flexible printed boards.

Flexible printed circuit board needs a special fixture because of its soft, , the fixture can not only put the flexible printed board is fixed, but also must be stable in the bath, or copper plating thickness is not uniform, which is an important cause of breakage and bridging in the etching procedure. In order to obtain a uniform copper plating layer, the flexible printed circuit board must be tightened in the fixture, and the position and shape of the electrode should be used.

* FPC cleaning process for copper foil surface

In order to improve the adhesion of the resist mask, it is necessary to clean the surface of the copper foil before coating the resist mask.

General cleaning chemical cleaning process and mechanical grinding process for manufacturing precision graphic, is the two most occasions clean technology combined with surface treatment. Mechanical polishing using the method of throwing brush, polishing material will cause damage to the copper foil, too soft and will not be fully grinding. Nylon brush is generally, the length and hardness of the brush must be carefully studied.

Using two polishing brush roller, on top of the conveyor belt, and belt conveying direction of rotation in the opposite direction, but if the polishing brush roller pressure is too large, the substrate will be greatly elongated and tension, which is one of the important causes of size change.

If the surface treatment of copper foil is not clean, then the adhesion with the resist mask is poor, so it will reduce the pass rate of the etching process. Recently, due to the improvement of the quality of the copper plate, the surface cleaning process can be omitted in the case of a single circuit. But 1OO m below the precision graphics, surface cleaning is an essential process.

Five PCB reliability design method

Electronic equipment used in all kinds of electronic equipment and systems are still in printed circuit board as the main assembly way.Practice has proved that even if the circuit principle diagram design is correct,Printed circuit board design undeserved, also can produce adverse effect on the reliability of electronic equipment.For example, if the two parallel lines in close proximity, PCB will form the signal delay, reflection noise in transmission line terminal formation.Therefore, in the design of the printed circuit board, should pay attention to the right way.
1.ground design in electronic equipment, earthing is an important way to control interference
If you can combine grounding and shielding correct use, can solve most of the interference problem.Electronic equipment in the ground structure roughly systematically, casing (block), digital earth (logically) and simulation, etc.The ground should be paid attention to in the design of the following:
(1)Correct selection of single point grounding and multi-point earthing in low frequency circuit, the signal of the working frequency is less than 1 MHZ, little impact on its inductance between wiring and devices,The grounding circuit had a greater influence on the formation of the circulation of interference, thus should use one-point earthing.When the working frequency of the signal is more than 10 MHZ, ground impedance becomes large, at this point should try to reduce the ground impedance, nearby multipoint earthing should be adopted.When the working frequency in 1 ~ 10 MHZ, if the grounding, the ground wire length should not exceed 1/20 of the wavelength, otherwise the multipoint earthing method should be adopted.
(2)Separate digital circuit and analog circuit.Circuit board has both high speed logic circuit, and linear circuit, should make them apart as far as possible, and both ground not mixed, respectively connected to the power end ground.Try to increase the grounding area of linear circuit.
(3)Bold grounding line as far as possible if the ground wire is very thin, grounding potential changes over electric current, the timing signal level instability of the electronic equipment, noise resistance worse.Therefore earth wire should be bold as far as possible, make it can pass three allows current in printed circuit board.If possible, the width of the ground wire should be greater than 3 mm.
(4)Earth wire will constitute a closed loop road design only composed of a digital circuit PCB ground system, to make the grounding line closed loop road can obviously improve the ability to resist noise.The reason for this is that there are many integrated circuit components on printed circuit board, especially in case of more components, power consumption due to restrictions of the grounding line thickness, can produce large potential difference on the knot, cause anti-noise ability to drop, if the grounding structure into the loop, would be to reduce the potential difference value, improve the ability to resist noise electronic equipment.
2.the electromagnetic compatibility design
Electromagnetic compatibility is refers to the electronic equipment in various kinds of electromagnetic environment is still able to coordination, ability to work effectively.Electromagnetic compatibility design of the purpose is to make electronic devices can inhibit a variety of external interference, make the electronic equipment can work normally in the specific electromagnetic environment, and also can reduce the electronic device itself electromagnetic interference to other electronic equipment.
（1）Choose the reasonable width of wire.Due to transient current impact on the printed line produced by the interference is mainly caused by printed conductor inductance components, therefore should minimize the inductance of printed wiring.Printed conductor inductance is proportional to its length, its width is inversely proportional to, so the short and fine wires is favorable to suppress interference.Clock, lead line drive or bus driver signal often contains large transient current, printed wiring to short as possible.For discrete component circuit, printed wiring width at around 1.5 mm, can fully meet the requirements;For integrated circuits, printed wiring width can choose between 0.2 ~ 1.0 mm.
（2）Adopt the strategy of the correct wiring.Using equal linear conductor inductance can be reduced, but the mutual inductance between conductor and distributed capacitance increases, if allow layout, had better use well glyph structure, network cabling concrete side lateral approach is printed circuit board wiring, the other side vertical wiring, then in the cross hole is connected with metallized hole.In order to prevent the PCB cross talk between wires, when designing the wiring should try to avoid long distance equal walk the line, the distance between the lines to open and as far as possible, signal wire and ground wire and the power cord as far as possible, don't cross.In some very sensitive to interference signal lines between a grounded printing line, can effectively restrain cross talk.
In order to avoid the high frequency signal through printed wiring of electromagnetic radiation, the printed circuit board wiring, also should pay attention to the following:
●Try to reduce the discontinuity of printed wiring, such as wire width don't mutation, the wire should be greater than 90 degrees of corner ban ring line etc.
●Clock signal leads the most susceptible to electromagnetic radiation interference, go line should close, with different ground loop drive should be close to the connector.
●The bus driver should be close to its desire to drive the bus.For those who leave the printed circuit board, and lead the drive should be tightly close to the connector.
●Data bus wiring should be every two signal lines between a signal ground.Best is tightly close to the least important address fuses placed ground loops, which often contains high frequency current.
●In PCB layout, high speed, medium speed and low speed logic circuit should be arranged device
（3）Reflection interference suppression.In order to prevent the reflection interference appears in the printed line terminal, in addition to the special needs, should as far as possible, shorten the length of the printed line and adopting slow circuit.Add terminal matching when necessary, that is, at the end of the transmission line to ground and added a different power supply side resistance matching resistance.According to the experience, generally faster TTL circuit, when the printed line longer than 10 cm above the terminal matching measures should be adopted.Matching resistance value should be based on the output of the integrated circuit drive current and the maximum absorption current to decide.
3.decoupling capacitor configuration
In dc power supply circuit, the change of the load will cause the power supply noise.As in digital circuits, when the circuit from one state into another state, will be on the power line to produce a large peak currents, the formation of the noise of the transient voltage.Configuration decoupling capacitor can restrain the noise due to load changes, is the reliability of the printed circuit board design of a conventional practice, configuration principle is as follows:
●Power input end of the jumper a 10 to 100 uf electrolytic capacitor, the position of the printed circuit board permitting, adoption of more than 100 uf electrolytic capacitor anti-interference effect will be better.
●For each of the integrated circuit chip configuration a 0.01 uF ceramic capacitor.If printed circuit board and a small space, can every 4 ~ 10 chip configuration a 1 ~ 10 uf tantalum electrolytic capacitor, this particularly small high frequency impedance of the device in 500 KHZ ~ 20 MHZ range impedance is less than 1 Ω, and leakage current is very small (below 0.5 uA).
●For weak noise, shut off the current change device and ROM, RAM, storage devices, such as should be the power cord of the chip (Vcc) and ground (GND) direct access to the decoupling capacitor.
●Decoupling capacitor lead cannot too long, especially high frequency bypass capacitors can't lead