The publisher makes no warranties, express or implied, with respect to the material contained therein. For more information, see our print and e-book bulk sales website at www.apress.com/bulk-sales.
About the Authors
Acknowledgements
Introduction
In Chapter 1, we begin with a brief description of the drone system and its critical components. Chapter 6 discusses the software processes and real-time software that go into drone-like systems.
What Is a Drone?
Military
Industrial
Commercial
Parts of a Drone System
Hardware
The SOC
Note Intel Core, atom, and Quark processors are SoCs on a single package
Subsystems
Input
Output
Storage
Communication Devices
Subsystems play an important role in defining the specifications of the product. Product” is the proper term for a system when it is in production stage and available in the market). As seen earlier, some subsystems from the list may or may not be required for the target application of the system.
Software
Given the nature of use, drones must use a real-time operating system (RTOS). Application-specific components use the "OS and Drivers" part to accomplish the goal.
Mechanical
Note heavier drones are powered using alternate fuels other than batteries, such as solar power or gasoline. drones operating with
Ground-Based Controllers and Accessories
Summary
Drone System Design Flow
System Design
Often the composition of the team depends on the nature of the product being designed and developed. In general, the product design process involves three main aspects: specification, architecture, and implementation.
Requirement Specification
Architecture
Mechanical Design
Hardware and software undergo the minor changes mid or later in the detailed design phase. Building a prototype from the 3D mechanical model is cooler these days, as opposed to hardware design, which still remains a long pole in system design.
Hardware Design
The 3D printers print (create) objects with a plastic-like substance, unlike traditional printers that spread ink across a page.
Software Design
Implementation
Specifications for Our Drone, “Crop Squad”
As mentioned in the previous section, the starting point is to define (create) or choose the right mechanical design of the system. In the following sections, we will talk about the most important aspects of making mechanical design choices.
Definition
All other things being the same, the ID is one of the major deciding factors as it creates the first impression in the customers and a favorable impression increases product sales.
Purpose
Requirements
Enclosure Top: A plastic or fiber mechanical enclosure of the drone protects the internal electrical and mechanical subsystems from external disturbances. End of Enclosure: A plastic or fiber mechanical enclosure of the drone protects the internal electrical and mechanical subsystems from external disturbances.
Dependencies
Hardware Requirements
Electrical Ingredients Selection
BOM and Component Procurement
The EBOM is part of the system BOM in most systems and is one of the subordinate elements of the main BOM. The design, build date, quantity and delivery time of the part must match the project plan.
At a minimum, engineering samples should be available during the design phase, if not production samples. Reservations must be made for parts that must be provided by third-party vendors.
PCBA Design
An ODM (original design manufacturer) is a company that designs and manufactures the product according to the specifications; the product is remarketed by another company for sale.
PCBA Dimensions
The thin red line in the figure is the outline of the PCBA, from which the dimensions are marked as XXmm. This is actually a top view of the PCBA showing the footprints of the components placed on top.
PCB Type
In the Crop Squad drone, shown in Figure 2-1, the architecture diagram of the SSD and WiFi Bluetooth modules is placed on a separate board and connected to the main board via an FPC connector. This shows that the electrical part of the drone is split into two rigid PCBAs connected via a flexible PCB.
Layer Stack-Up
The last column in the stack is the dielectric constant of the dielectric materials. Generally, the stack will have a few more columns, including the trace width of the signal to reach the target impedances.
Floor Plan
The electrical components placed on a PCB vary in height and the mechanical design must take each component into account. Cooling systems, such as heatsinks and fans, are non-electrical parts that are considered part of the PCBA and they add to the overall height of the PCBA.
Power Architecture
Power Estimation
SOC Power Requirements
Ripple and noise can be reduced by placing the power layers in the stack up as well. Other ways to reduce the ripple are by placing the power components in the right place and implementing the most well-known power routing techniques.
Platform Power Requirements
Power Devices
In addition to the device cost, the switching regulator requires external components for normal operation, so the total cost is many times higher than that of a linear regulator. Ripple/Noise: Ripple and noise are lower in a linear regulator; this quality makes the linear regulator more suitable for analog designs and clock and PLL blocks in the SOC.
Power Map
Rail Name is the name of the link used in the table to distinguish from each other. On the upper side of the power map are the details of SOC blocks and subsystems (camera, display, memory, modem, etc.); current consumptions are listed.
Power Sequencing
Battery Estimation
Battery Constraints
Battery Capacity
If you fit a 4 Ah battery pack it can be expected to run for an hour on average.
Watt Hours and Energy Density
Battery Cost
This is exactly why designers and engineers must have skills and knowledge to analyze battery regimes to make the best choice for a particular application. It is therefore necessary to make careful evaluations of the requirements and limitations imposed by a specific application.
Software Architecture
In some cases, the device vendor may not have the driver for the operating system we want to use. It is also possible to influence the device vendor to provide the driver for the operating system of our choice; it's a business decision for the device vendor.
Logistics and Operations Management
Application Specific Components: Application specific components, as the name suggests, are based on the intended use of the drone.
Board and System Assembly
Demand BOM
Production BOM
In addition, we have created a high-level definition of the drone system we intend to design. Overall, this chapter sets the stage for the detailed discussion of UAV system design that will be covered in subsequent chapters.
Key Ingredients and Selection
System on a Chip
The critical subsystems are overloaded as the processors in a harvest monitoring drone, which is explained in detail below. ISPs: Image signal processors convert the raw recording to a specific format that a computer can read or the software application can recognize for further processing.
Categories
Network Modem: Establishes the connection between the drone and the IP network/cloud/server and helps to upload the enormous data for further processing if needed. In such a case, the ISPs within the SOC receive the raw recording from the camera through a direct digital interface without any compression, apply the required image or video processing algorithms and compress the data before converting it into any standard file format.
Key Considerations
Solutions
Memory
Standard DRAM
First Generation
Second Generation
Third Generation
Fourth Generation
Fifth Generation
Mobile DRAM
The choice of memory device is based on the system software requirements and also depends on the SOC. If the SOC's memory controller does not support 8GB of memory, then there is no way the system can have 8GB.
Magnetic Storage
Optical Storage
Flash Storage
CompactFlash
Multimedia Card
Secure Digital Card
Solid State Drives
USB Flash Storage
If the uSSD serves as the main integrated storage, SD cards and USB flash devices can serve as external extended storage devices. In addition to the micro SSD part, the system can provide a micro SD card connector or a USB connector for external removable storage devices.
Communication Module
The system will have one or all of these wireless networks depending on requirements. The system must strictly comply with all regulatory standards so that it does not interfere with any other communication inside or outside the device.
WiFi+BT
Every time a system adds wireless communication, radiation is intentionally and unintentionally added to the system.
Mobile Network
IR/RF Wireless
Solution
Camera
Monochrome
Color
Spectral Imaging
The camera must go beyond color wavelengths to capture the anatomy of leaves, stems, pods, flowers and fruits. For example, to monitor leaf health and nutrient value, the camera must capture the internal pattern and distribution of chlorophyll, which is beyond the visible spectrum and includes the IR and UV range.
Display
A hyperspectral image sensor can produce an RGB color image aligned with multi-band spectral images. This creates the necessary infrared wavelengths from light reflections from the object along with an RGB color image.
Internal
Even if there is no compatible interface in the SOC, there are options available to convert any display, interface and protocol to make it compatible for the display.
External
A dedicated video transmission communication channel is required between the drone and the remote controller to stream the video live.
Flight Controllers
MCU/MPU
FPGA
Key considerations for a flight controller are the complexity of integration with the system, supported sensors, flight capability and cost.
Battery
Lead Acid
Nickel Cadmium
Nickel Metal Hydride
Lithium-Ion Batteries
So for a drone, the cell architecture should be two cells in a series, also called 2S1P architecture, which means two cells in series and one in parallel. In that case, the charger should be designed to charge the batteries faster.
Thermal Solution
Active Cooling
Passive Cooling
Since the drone will fly to perform the intended application and will produce enough noise with the propellers of the quadcopter, noise from the board makes no difference.
Interconnects
Since a drone is a complex electromechanical system, choosing the right interconnections is critical to achieving the best performance. There is a wide range of connectors from different manufacturers that can be used on a vehicle to connect electrical parts and subsystems.
Cable Connectors
The mini and micro USB varieties are typically used with smaller, portable devices such as PDAs, phones, and digital cameras. The standard USB connections are more commonly used on devices that often remain connected, such as external hard drives, keyboards and mice.
Ethernet
Board-to-Board Connectors
Three different mounting types of board-to-board connectors are through-hole, surface-mount and press-fit technology. BTB connectors are selected by considering mounting method, pin spacing, number of rows (also called number of ways), pin length, stacker height, etc.
Wire-to-Board Connectors
RF Connectors
Research activity in radio frequency (RF) circuit design has increased in the 2000s in direct response to the huge market demand for low-cost, high-data-rate wireless transceivers.
FPC/FFC Connectors
Connector selection is strictly based on applications and board form factor.
Mechanicals
The camera can be placed on the bottom of the drone to provide a good 360-degree view. A housing covers all parts of the drone except the propellers on the top and the camera on the bottom.
Drone Hardware Development
The first step of the design is to develop the PCBA library and the last step is to obtain a complete, functionally working PCBA. To get the final working PCBA, the total development cycle is split into design and validation cycles.
PCB Library Development
Symbol Creation
The completed schematic has all the required symbols connected together with wires (nets) as per the design requirement. For example, the logic symbol for resistors is the same for all values.
Logical Symbol Creation
PCB Layout is a visual representation of the actual PCB with all required PCB traces connected to each other with copper traces on a multi-layer PCB. All components shown in the architecture block diagram in Figure 2-2 have a logic symbol and corresponding trace with all discrete components connected.
Symbol Verification
Pin names and numbers usually match the names and numbers of the component data sheet or the device accessories. The created symbol must comply with the standards and BKMs, and more importantly the symbol must be well suited to the schematic design.
PCB Footprint Creation
The pins are arranged in such a way that the connections can be made with other peripheral components in a presentable manner and better readability. A symbol cannot be changed once it is added to the central library, allowing other board developers to use the same symbol for other boards and different projects.
Footprint Verification
These signal terminations are shown in schematics with the appropriate components such as resistors, inductors, and capacitors on the actual connection. This recommended design is based on the evaluation board design and manufacturer's tested data.
Design Rules Checking
However, a designer may choose to design an entirely new circuit that is different from the reference circuit. There are several complicated circuit designs for the complete drone hardware, interconnected on multi-page schematics that may follow the reference circuit from the datasheet.
Generating a Netlist
However, simulation requires the actual electrical model of the components or the schematic to be exported to other simulation tools with all the electrical specifications of the component.
Bill of Materials
Since creating a schematic is a manual, time-consuming process, a BOM is often generated from partially completed schematics. This partial BOM is called the intermediate requirement BOM and is sent to the PCBA manufacturing plant.
Symbol Attributes
BOM Generation
Material Readiness
Layout Design
Track width is a compromise based on current flow, available space, part size, and electromagnetic interference. Depending on the impedance, receptivity and signal on the tracks, the loop area is another trade-off considered during design.
Board Outline
The thickness of a layer will affect how much current can flow through the circuit without damaging the traces. Track width is another factor that affects how much current can safely flow through the circuit.
Electrical Constraints
To determine safe values for width and thickness, you need to know the amperage that will flow through the trace in question. Like layer thickness, the width of your traces will affect how much current can flow through your circuit without damaging the circuit.
Signal Integrity
The proximity of tracks to components and adjacent tracks will also determine how wide your tracks can be. When designing a small PCB with many traces and components, you may need to narrow the traces so that everything fits.
Impedance Mismatch
In the case of a printed circuit board, this can be achieved through careful choice of medium and through the use of termination schemes.
Signal Attenuation
Cross Talk
Power Integrity
The noise or voltage ripple must be handled differently depending on the frequency of operation. The placement of the capacitors is of varying importance depending on the frequency of operation.
Mechanical Constraints
Most PCB design software can only view a board in a single orientation and from a single direction. In particular, most PCB programs lack the associated automatic dimensioning that mechanical CAD users take for granted.
Coordinate System
The panels are viewed from one side and the opposite side features and components as an "X-ray". Even the cheapest mechanical CAD software does extensive relative measurements and has a "snap" capability.
Orientation
Dimension
Keep Out Zones (KOZ)
Physical Constraints
Design Constraints
Component Location
Note that using the pad as a reference point does not always work for surface mount parts as the center of the pad may not correspond to either the pin or the lead center.
Netlist
Placement
It is important to set up the board perimeter, stacking, electrical and mechanical constraints before entering the netlist. Other components (in gray) imported from the netlist are already grouped and placed within the outline of the board.
Routing
The associated components highlighted in green for this IC are assembled outside the board before being placed inside the board outline.
Mechanical Check
This 3D view of the PCB assembly has a certain standard file format, which can be imported into any mechanical tool to check the mechanical assembly of the drone with other mechanical components already imported into the tool or designed in the same tool.
Gerber Release
Simply put, Gerber format files are essential from the beginning to the end of the PCB fabrication process. Finally, the Gerber release for all boards needed for the drone marks the end of the drone hardware design cycle, which is the half mile traveled for the entire development cycle.
System Assembly, Bring-Up
This chapter covers the manufacture and assembly of the drone with the list of brand and purchase items ordered according to the system parts list. PCB is the primary manufacture; they are designed in-house and manufactured by the PCB suppliers using a complex manufacturing and assembly process.
PCB Fabrication Process
Fabrication Steps
Transfer the orientation to the plate by exposing the dry film and the orientation film on top. The board continues from step 2 of the PCB process for the top and bottom layers.
PCB Assembly Process
The total copper thickness of the top and bottom layers is the combined thickness of the copper foil and plating. Most companies that specialize in PCB assembly need the PCB design file to start along with any other design notes and specific requirements.
Surface Mount Assembly Process
Solder Paste Stenciling
Pick and Place
Reflow Soldering
Inspection and Quality Control
Manual Checks
Automatic Checks
Ray Check
Through Hole Assembly Process
Manual Soldering
Wave Soldering
After this soldering process is complete, the PCB can go to final inspection, or go through the previous steps if the PCB needs to add additional parts or mount a different side.
Final Inspection and Functional Test
Post Process
Typically, the design engineers will be present at the factory to do the initial commissioning. The factory commissioning helps the engineers to solve any assembly related problems in the factory itself.
Board Power-On
This is because it is the ions in plain water that damage a circuit, not the water itself. After washing, a quick drying cycle with compressed air leaves the finished PCBs ready for firing.
Basic Inspection
They should be performed very carefully and all observations should be recorded so that they can be reviewed in case of problems.
Short-Circuit Checks
Some power rails may display impedances as low as 20 ohms, 40 ohms or 90 ohms due to higher current consumption. For example, all of the power strips shown in Figure 2-10 in Chapter 2 should show limited resistance when measured with a digital multimeter, which qualifies the board for safe ignition.
Power Check
The CPU core voltage of the latest generation Intel multi-core processors can even show 1 ohm impedance due to the high current requirement of that rail. These busbar voltages should pass the voltage level and tolerance criteria as per the requirement.
Sequencing and Reset Check
Power supplies that do not meet the exit criteria may have problems with the actual design, assembly or even PCB.
Board-Level Testing
BIOS Flash Programming
OS and Application Installation
Functionality Check
In a typical Crop Squad UAV architecture, a number of board-level components are available to test the functionality of the board itself. If there are problems that cannot be fixed by rework, the board will go through the entire design cycle again.
Design Validation Testing
The motherboard (includes subsystems such as SOC, memory, storage, flight controller, sensors), daughter board (WiFi+BT module), camera, battery, antenna and motors are assembled first with all the electrical connections, without enclosures, to make the board do -level functionality checks. The complete board level validation helps the designers and test engineers to resolve any hardware or software level issues on the board before the system assembly.
Power Validation
A test plan describes the process to ensure that the design meets the test specification. The most important step in validating a power supply is measuring the ripple, noise and transients on the power rails.
Efficiency
Supply power from the desktop power supply through the input test points of the power supply devices on the board and connect the electronic load to the output of the power supply device. Use the simple formula of efficiency = power output/power input for each power rail used on the board.
Thermal
The product of the input voltage and the input current gives the input power in the same way as the output power. All efficiency issues must be tuned to meet the target energy consumption of the system as specified in the PRD. the system mounting).
Power and Performance
Each unit is attached to the thermocouple with a longer lead extended outside the chamber for measurement. If it cannot be solved due to a defect in the device itself or the semiconductor, then the battery life indicated in the PRD should be revisited or changed according to the actual measurement.
Electrical Validation
Signal Integrity Testing
If any of the issues cannot be resolved, the board goes through a redesign cycle. Most signal integrity problems occur due to PCB trace impedance mismatch, return loss, insertion loss, crosstalk, and jitter.
Integration Testing
Theoretically, although the design follows all the electrical constraints mentioned in Chapter 4, the physical board may have problems due to the variation in the calculated parameters and properties of the materials. Any of the measured values do not meet the specification, the problem should be solved by hardware or software setting.
Drone Assembly
Drone System Validation Testing
System Pilot Build
The pilot builds can only be distributed for field testing after certification by an authorized regulatory test lab. The positive results of the system-level tests lead to the factory pilot build.
Software Development
Software Development and Deployment
Software Development Life Cycle
Software Development Models
Waterfall Model
Shaped Model
As can be seen, the V-shaped model is only suitable for systems where the requirements are well known in advance and there is little chance of changing the requirements.
Incremental, Iterative, and Agile
Other models such as the rapid application development (RAD) model and the spiral model are not as common. Let's start with the software stack of a generic system and then get down to the details.
Software Stack
Now, from a software perspective, we first need the system firmware to boot the system. In addition to the BIOS, system firmware also contains UEFI (pre-OS) drivers for various components in the system.
System Firmware and Device
It has nothing to get to, so now we need to install an operating system on the system. The high-level mechanism or architecture of the firmware update capsule is that the OS software passes the device firmware as a payload to the system firmware.
Operating System
As can be seen, in the RTLinux operating system there is a layer (the RTLinux layer or RTLinux plugin) between the real hardware and the standard Linux kernel. The standard Linux kernel is not modified at all, and in an RTLinux operating system the RTLinux plugin/layer takes over.
RTLinux Design
The real-time tasks are handled directly by the RTLinux layer, while the default kernel is treated as a low-priority monolithic task. The scheduling of real-time tasks is handled by the RTLinux layer and not by the standard Linux kernel.
SDK and Libraries
Application
Key Considerations of Drone Software Design
This means we will talk about the specific features of the drone system and follow that up with specific hardware and software design considerations to support the needs. In the following sections, we'll talk about both aspects in detail and discuss the specific hardware and software design decisions we need to make.
Low Power
However, it is clear that there are some specific characteristics of a drone system that require consideration. Drones are real-time systems, meaning that drones operate under very tight timing / response time constraints.
HW Considerations
And at the platform design level, the design choices should be made in such a way that the components involved in one use case share the power resources (or in other words in the same power domain); more importantly, however, the components involved in mutually exclusive use should *not* share the power resources. This allows the system/software to turn off the power resource for components that are not in use, thereby saving power.
SW Considerations
Active power management refers to the management of power when the system is in use. ACPI defines a mechanism to switch the system between work mode (G0) and a sleep mode (G1) or soft-off (G2) mode.
