How do you make electronic systems strong and flexible?

Make sure you have a realistic design specification before you start. Do full design calcs and derate everything as much as possible. Include maximums possible in design calcs so a new add-on or change elsewhere can be quickly evaluated. Simulations are good, but only as good as the data driving them, always have a prototype or two that you can modify (add breadboard area with convenient power rails on prototypes) and carry out real testing too.

During design process, it is important for a system to identify the feedback mechanism that will provide enough data to measure its system strength and weakness. Also, flexibility can be achieve with appropriate design plan and taking note of the factor of over-engineering. Appropriate system testing, data gathering, and data analysis provides strong and flexible system.

Spend proper time clarifying the requirements that will define overall reliability. Write the requirements to be clear, singular, feasible, implementation independent and verifiable. Develop test plans to verify and validate each requirement and aim to leverage existing standards (EMC, ESD, vibration, dust and water ingress protection, Sun exposure etc) as guidelines and then use third parties for the final tests and reports. Invest in some internal test equipment to speed up the verification process. Get the verified prototypes out in the real world with real users for real tests.

When designing the system, design your system to a "known" failure point, well above the operating point, if you don't, the system will choose the failure for you. Do VIPT calculation (Voltage, Current, Power, Temperature) for every component, considering environmental factors, thermography of your board/system, ESD events, EMI/EMC, stresses due to mechanical packaging/vibrations and system input fluctuations.

Build the final product through an evolutionary method to be able to start immediately to design, build and test the core functionalities in order to ensure to have a minimum viable product able to be evaluated by your customers. Work with requirements to define accurately the key functions and how you intend to verify them. Define only what is necessary when is needed, to have a well-defined and consolidated core design but leave the rest to its natural evolution following the maturity of your design concept. Use the modelling of the use environment to understand and test the most critical stress factors of your system and apply incrementally the use of simulation models to quantify the stress margins of critical parts and components.

One thing people need to remember when designing a circuit is to do regular reviews. Waiting till the end of the design process (prototype stage) to do a single review is bad practice. One form of check is regularly simulating your circuit using Pspice.

If you have a trusted supplier, make sure to run all critical components selections by them. They likely have a local alternative that is more cost optimized with a more forgiving lead time. Naturally ask for test reports and certificates and then make sure to test your prototypes with the final "mass production" brands as much as you can. Carefully consider which components absolutely need to be sourced from original sources (digikey, mouser etc) and which can be "local". The above assumes you'll manufacture in Asia.

Component selection aligns with qualification and production screening per industry standards. Categorize components by system criticality. Analyse specs for compatibility with design requirements and environmental conditions. Apply strict reliability and performance criteria to select the essential components. Prefer pre-certified components for streamlined product certification. Conduct early cost analysis and address supply chain issues. Collaborate with approved distributors recognized by procurement and production to find valid alternative parts and reduce single-source components. After listing essential components, assess manufacturability and assembly with the manufacturer to prevent issues during prototyping and testing (DfM).

For a manufacturable design, component package consideration should be kept in mind in the initial stage itself, favoring standard packages whenever possible. Additionally, when selecting components based on calculations and thorough analysis, mitigate sourcing risks by actively identifying two alternative options within the same component workflow.

You need to select good quality components/Long lasting components. Always go for the long term solutions. Calibrating all equipment is timely for better monitoring.

Modularity addresses diverse design needs. In complex distributed systems, it facilitates separate assembly and subsystem(s) design by independent teams. At the subsystem level, it allows the reuse of approved functional blocks for mass production, reducing costs and development timelines. This fosters increased product reliability and confidence. It relies on robust functional modelling and standardized interfaces, establishing a compatibility matrix for integrating pre-existing modules into new designs. Achieving these benefits requires substantial development time and costs before maturity.

Consider using FPGAs for digital "glue logic". They usually have high IO capacity, a variety of standard and high-speed interfaces and can be reprogrammed on demand.

Focus on optimizing component utilization by crafting the hardware in a manner where minor component replacements can fulfill all required functionalities. For instance, consider implementing a combination of pull-up, pull-down, and series resistors on a pin to accommodate various functionalities. This approach enhances flexibility and streamlines the design process by only changing Bill of Material and not the Gerber files.

Compartmentalisation/modularisation allows for: - creating a clear dependency chart, - parallelising independent workflows, - testing of modules before integration. This enables breaking down a complex system into smaller tasks that can be tackled by engineering teams effectively. Modularity also allows for easy monitoring of progress and enables performing demonstrations of partial functionality while the full system is still under development.

To a certain degree, it is good design practice to adopt design factors on the components that may be under higher stress or offer a single point-of-failure to the system. A design factor is just a buffer between your expected worst-case scenario for a certain parameter (for example, peak voltage) and the maximum ratings of the selected component. It definitely helps making a system more robust, but it also could make it bulkier and more costly. So striking a balance is key.

Protective measures should not be overlooked, as they play a crucial role in ensuring the long-term reliability and performance of these systems. Neglecting protective measures can lead to premature failures and costly repairs or replacements. Engineers must strike a balance between functionality and protection. Integrating protective measures into the design process early on can result in more robust and durable electronic systems that are less prone to issues caused by environmental factors or wear and tear. Ultimately, a comprehensive approach that considers both functionality and protection is essential for creating electronic systems that meet performance goals while also being resilient in various operating conditions.

Identifying which components are critical for the user's safety and which components would result in a loss of functionality helps determine which components require protective measures. Incorporating redundancy into such safety-critical components or systems can ensure continuous operation even when a primary component fails. Simulating the circuit or system behaviour can help find out about potential weaknesses or previously unknown error states, which can then be eradicated. Considering application-specific conditions, for instance, vibrations in the case of designing a PCB for automotive applications, allows for making appropriate design decisions, such as PCB component mounting technique, potting, encapsulation, and damping required.

Feedback mechanism would be crucial based on the criticality and severity of application failure or the RPN from FMEA. Systems with lower severity like small application for domestic uses can have fewer feedback like temperature, current voltage stability etc. The application with Industry or automotive with safety requirements would need feedback for all the crucial parameters including the connection of supply and have PWM to check impedance of line. There are high value resistors which are connected to power line to have feedback. Mathematical modelling of the dominant parameters could improvise the correction rate and algorithm can be built for specific application. Redundancies in the feedback, indirect correlation for failures

Incorporate hardware provisions for monitoring parameters like bus voltage, temperature (including those at hot and ambient locations), inertia (for dynamic systems). Utilizing signals from power management ICs smartly (EN, UVLO, Power Good). This data can serve as inputs to a software algorithm, enabling the addition of diagnostic capabilities to enhance system performance and reliability.

Intensive simulations are the keys to every successful design. Optimal component placement is the key to a good PCB layout. Multiple placement adjustments during routing should be encouraged.

In addition to the above, you should consider all modes so that the system does not freeze. Freezing the system and suspending the process can cause a lot of damage. For this reason, this state should be prevented in different layers so that there is no undefined state in the system.