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The word “ ” in Chinese refers to the circle of life! Recently, I was watching a 2003 Korean movie, “ ,” and discovered this concept. The circle of life has different meanings across several civilizations, and when you think of the Software Development Life Cycle (SDLC), it is not that different either. Yǒulún Old boy The concept related to the circle of life refers to birth, aging, death, reincarnation, and a loop of the same activities. SDLC is a process of requirement gathering, designing, developing, and maintaining software throughout the life cycle. The process repeats itself for every software you create, making it almost like- “ .” Yǒulún However, SDLC is not just important for excellent software development - there are several other aspects to consider like efficiency, cost, and business impact. So let’s first know SDLC and several approaches that you can leverage to improve the effectiveness of software development. What is SDLC? The Software Development Life Cycle (SDLC) is a series of stages that helps in bringing a business case to realization through , , , , and . It involves fixing errors that incur efficiency problems leading to overhead costs. Here, execution is everything, and that is the reason you need a practical solution. design development error detection making changes deployments maintenance If your execution is correct, SDLC has several benefits like: , allowing you to plan the execution more efficiently. The entire goal of your project becomes more visible It offers who can review the entire process at the end of each stage. better management control for project managers Due to comprehensive software testing and changes made accordingly, ensure . no pending errors to resolve later Extensive documentation will enable for project execution. easy onboarding of new teams There is a constant loop of providing feedback to the earlier stages of software development, . ensuring high-quality products The SDLC Waterfall Model Conventionally, the SDLC waterfall model has been following a linear path where every stage leads to the next one, and there is no way to go back to a stage for making quick changes. This approach becomes restrictive and does not allow software engineers much flexibility. The entire SDLC model is distributed into several stages, from the requirements stage to design, development, and even maintenance. What makes this model so rigid in the modern software development landscape is the inability to incorporate changes that may be a requirement due to adding features or sudden changes. Here each stage is dependent on the predecessor one and can’t be complete without it. The output of an earlier stage is the input for further stages. So, if you don’t have the full set of requirements, you can’t design the software, and similarly, without a design, the development will not happen. However, the shortcomings of the waterfall model can be mitigated by an agile approach! An agile SDLC model follows the path of a river that changes the way whenever needed! Agile SDLC Model The agile model explores an incremental, iterative approach to software development. Several builds are created for a software project, and with each iteration, new features are added while constantly making changes as per feedback from tests. Every iterative development is known as a sprint at the end of which there is collective feedback from different teams to understand the requirement of changes. The agile approach allows businesses to improve the software with every iteration making it an open-loop SDLC model. Apart from the Agile and waterfall SDLC model, there are several others that you can explore for your software development projects like, V-model V-model explores the parallel approach where there are design stages executed on the one hand, and on the other hand, parallel tests are conducted. Both the verification and validation stages meet at the coding stage by which execution takes place. The V-model is similar to the parallel programming approach, where you can code parallel to the testing process. One of the few advantages of such an approach is creating error-free software and reducing the cost of fixing them later. Hybrid Model A Hybrid or spiral model merges the waterfall approach with agile methodologies. What makes it more comprehensive than any other SDLC approach is how it offers excellent risk analysis. It focuses on the risks pitched against the cumulative software costs, which helps improve the entire SDLC. Here the spiral loop has an outward approach that involves a requirement plan, development plan, test plan, operational prototype, risk analysis and resolutions, integration, etc. Knowing the SDLC and its models can be a way to understand how it functions, and now let’s know why it’s essential! SDLC: A Necessity! Software development is not just about the programming aspect but an entire life cycle that begins from conception and ends at deployment. So, leveraging the SDLC approach makes more sense. Framework Developing software applications need a plan that can help reduce inefficiencies and offer high-quality products. This is where SDLC acts as a guide with a framework to build your software projects. With SDLC, the entire process is distributed into different phases allowing you to assess results at the end of each stage and formulate a well-planned strategy for optimal software development. Requirement Analysis The SDLC process allows you to have a comprehensive requirement analysis, which is essential for planning the entire development. This phase not only helps in understanding the requirements of a project but also enables you to decide the, Scope Timeline Budget Risks involved It also allows you to form the entire project’s design foundation, so SDLC becomes crucial for requirement analysis. Streamlining the Development Another critical aspect where SDLC has the most importance is streamlining of the development process. Every software development process needs an approach or methodology at its core for the successful execution of operations. SDLC allows software programmers to leverage different agile, waterfall, or hybrid models for a streamlined development process. It also allows coping with sudden changes in the software development process or specific integrations. For example, suppose you want to integrate a cloud-based service with your software after the design foundation is decided. In that case, you will need a different approach than the conventional waterfall method. SDLC allows you to leverage other models and define methods for streamlining a development process. Identifying the Real Bug Software developers must identify a bug before deployment, but leveraging the waterfall approach becomes challenging due to linear and restrictive attributes. SDLC approaches like the agile or spiral model are necessary to determine the actual bugs in the software and mitigate the risks involved. For example, SDLC enables software developers to know the . It is an index that measures the number of open bugs or unresolved problems. You can calculate the BMI by using the following formula: BMI or Backlog Management Index BMI = [Number of problems resolved/ number of problems occurred]*100% SDLC also helps in the management of software testing and expenses for fixing such bugs. One of the critical aspects of software testing is the cost of test case development and execution. However, with SDLC, you can manage leveraging risk analysis and bug detection. software testing costs Conclusion: SDLC Is Important Software Development Lifecycle is not just about defining the project for higher efficiency but also about mitigating the risks involved with errors. For example, a simple forced Toyota to call back 1.9 million cars. software glitch So, you can understand why SDLC is so important for a software development project. It can help any business avoid such issues through a streamlined process.

The Software Development Life Cycle Is as Important as the Circle of Life

In electronics, the comparator is a circuit that makes use of operational amplifiers with very high gain in its open-loop state, that is, there is no feedback resistor. The has a positive or negative voltage output by comparing its input voltage against some preset DC reference voltage. The following are some common amplifier comparator circuits to analyze their functions. op-amp comparator is an operational amplifier compatible with DTL, RTL, TTL, or MOS logic levels. Its output can switch voltages to 50volts at currents to 50mA with a single supply. LM311 IC has been used for voltage comparisons for a long time in some typical circuits. Here introduces them with diagrams. LM311 versatile comparator Basic Circuit of LM311 Comparator (1) Offset voltage balance (Figure 1) When adjusting the balance, the two input terminals are grounded, and the 5kΩ potentiometer is adjusted to make the output be the minimum voltage value (close to 0V). (2) Single power supply (Figure 2) At this time, VEE is connected to GND. In Figure 1 and Figure 2, the load resistance RL is connected between VCC and Output. (3) RL is connected between pin 1 and ground (Figure 3) According to Figure 3, the input polarity is reversed, that is, pin 3 is used as the non-inverting terminal. (4) RL is connected between pin 1 and VEE (Figure 4). According to Figure 4, the input polarity is reversed. (5) General connection method of RL for positive and negative power supply (Figure 5). (6) Comparator connection with strobe (Figure 6). Connect a transistor to pin 6 for strobe connection. When the base of the transistor is connected to the TTL high level, the comparator is strobed (normal operation); when the base is connected to the low level, the comparator does not work. LM393 & LM2903 LM393 and LM2903 are a kind of low offset voltage dual comparators, and their pin arrangement is shown in Figure 7. Their main performance is the same, but the temperature range is different: the former is 0~70℃, and the latter is -40℃~105℃. Its main features are: wide operating voltage range, single power supply operating voltage is 2V~36V, dual power supply operating voltage ±(1V~18V); Working current is small, the typical value is 0.4mA; Input bias current typical value is 25nA; The input offset current is 5nA; The input offset voltage is ±1mV (LM2903 is ±2mV); The input common-mode voltage range is equal to the power supply voltage; The output voltage is compatible with TTL and CMOS logic levels; The input has ESD protection; the typical voltage gain is 200V/mA; The large signal response time is 300ns. LM393 & LM2901 The LM393 and LM2901 comparators are quad comparators. The pin arrangement is shown in Figure 8. The main parameters and performance of these two devices are the same, but the temperature range is different: the former is 0~70℃, and the latter is -40℃~105℃. The main features of these two devices: They can be powered by a single power supply or dual power supply, and the power supply voltage range is wide, ranging from 2V to 36V or ±(1V to 18V). Working current (independent of power supply voltage), the typical value is 0.8mA typical input bias current value is 25nA; typical input offset current value is ±5nA; typical input offset voltage value is 2mV; input common-mode voltage range includes low level; The differential input voltage is equal to the power supply voltage; the difference between the saturation voltage and the power supply voltage is low; the output voltage is compatible with TTL and CMOS logic levels; the typical large signal response time is 300ns; the voltage gain is 200V/mV. This article was first published on Writeup Cafe

Intro to Amplifier Comparator Circuits: LM311, LM393, LM2903 and LM2901

A controller plays an important role in the operation of a DC motor; its importance is even higher for a motor with extended functionality. Simpler motors can do without this device, but we are not going to talk about them in this article. Here, we’ll take a closer look at a brushed DC (BDC) motor controller, which is a simple and easy-to-build device. Working Principles of a BDC Motor and its Controller The main components of any DC motor include a moving part - a rotor ( or armature) and a stator, which is always at rest. The stator of a brushed DC motor can have either windings (series, shunt, compound BDC motors) or permanent magnets (permanent magnet BDC motors). The third essential component of a BDC motor is the commutator with brushes that connect the rotor with a DC power supply. The current flowing through the rotor generates the electromagnetic field around it. As the rotor starts moving, the similar poles of the magnetic fields created around the stator and rotor repel each other and provide a motion. When their opposite poles meet, the commutator switches the current supplied to the rotor. This creates the reverse polarity of the magnetic field, and the motion continues. A brushed DC motor can use a controller to start and stop the rotation, change its direction, manage the speed and torque. To perform these functions, a BDC motor controller regulates the current and voltage injected into the motor. Brushed DC motors are simple, cost-effective, and easy to control. They can perfectly fit simple low-power applications. Designing a BDC Motor Controller To design a BDC motor controller, you can choose an H-bridge, which is a traditional circuit for such types of devices. This electronic circuit has four open / close switches that supply positive and negative voltage by turns. By closing high-side and low-side switches in a diagonal pattern, the motor rotates in one direction. The rotational direction will change as soon as these switches are open and the opposite switches are closed. If you need a motor with a unidirectional rotation, you can build a controller using a simpler circuit with only one open/close switch. Choosing a transistor switch, make sure it meets the required parameters of the motor, for example, the maximum current. Otherwise, the transistor will burn out. For a low voltage controller, you can opt for power MOSFETs that provide a fast switching speed and high efficiency at a low price. Building a high current BDC motor controller, you can use IGBTs that allow a high level of current and are well suited for complex power electronics systems. Another option that you can choose for your project is a GaN transistor that can resist high temperatures and operates at very high frequency and voltage ranges. However, its production cost is still very high, so it will raise the price of your circuit design as well. You can use either an integrated circuit (IC) or discrete components. From a developer’s point of view, a DC motor controller IC is a simpler and more convenient solution. With a discrete circuit, it will take you the time and effort to assemble and solder the components. You have the same options for gate drivers that act as intermediaries between the microcontroller (MCU) and switches. An integrated H-bridge driver is a circuit with built-in power transistors. Despite the simplicity and reliability of its design, the gate driver IC is intended for low-voltage and low-power applications. Additionally, such gate drivers are not interchangeable. If they become discontinued, you’ll have to redesign the schematic together with the printed circuit board. BDC motor controller circuit design can have various configurations. Building your own device, you should consider the technical requirements and characteristics of the motor. Let’s briefly go over the design aspects that deserve your attention. Type of Signal You can build a digital or analog controller. The main difference between them is that the former comprises MCU-based hardware and firmware. You can combine these two types of signals and design a device that can be controlled with the help of both. Type of Power Regulation A BDC motor controller regulates the speed and torque by changing the power supplied to the motor. You can achieve this by using either a linear or switching voltage regulator. The linear regulator provides stable output voltage and keeps its magnitude constant, irrespective of the input voltage supplied by a power source. A switching regulator uses the pulse-width modulation (PWM) method and supplies voltage in pulses, changing its duty cycle (the ratio of the pulse to the pulse period). Thus, you can regulate the speed of the motor by adjusting various duty cycles. A switching regulator has higher efficiency and less power loss. Type of Control Some DC motor controller types can receive feedback from the motors, detect errors, and correct them, bringing the values into line with the setpoints. They are called closed-loop or feedback controllers. Alternatively, an open-loop or non-feedback controller cannot affect the situation, even if a failure occurs, as it will not detect it. You can find such motor controllers in simple systems that don’t need automatic control. Motor Characteristics Depending on the voltage necessary for the motor’s operation, you can choose a low or high voltage controller. A switching regulator works well for controllers with a wide operating voltage range. A linear regulator better suits a low voltage DC motor controller because the excessive input voltage may cause power loss and even thermal overload. Motor power relies on the current supplied by the power source. Thus, a low-power BDC motor needs a low current controller and vice versa. Challenges of Building a BDC Motor Controller Accessibility and easy implementation of BDC motors and their controllers make them a suitable solution for many projects. Despite the simplicity, a brushed DC motor controller design may still involve some challenges. For example, the switches in an H-bridge cannot be turned on and off simultaneously. There will always be a moment when all the transistors are open. It may lead to voltage and power loss, or even short-out if the opposite upper and lower switches are turned on. To avoid this situation, you can introduce dead time, which is the time when all switches of an H-bridge circuit are closed. PWM frequency (the number of pulse periods per second) is an important parameter that you should adjust in a proper way. Too low or too high PWM frequency will lead to the malfunctioning of the controller and consequently the motor. Excessive electromagnetic interference caused by the constant switching of a mechanical commutator is a common problem of a brushed DC motor, and you should cope with it too. Read about BDC motor controller in more detail here .

Building a Brushed DC Motor Controller: An Overview

By now, the need for clean energy is clear. Climate change is prompting industries of all kinds to reduce pollution and emissions to foster a healthier environment. The energy sector often takes on the responsibility of transforming others, such as by providing solar and wind as renewable options. Geothermal energy is now making a name for itself as well, thanks to new technology. Improvements for Geothermal Geothermal has stayed in the background for years while other renewables came to the fore. That’s because geothermal energy needs some improvements. Though there are a few different types of generation, the system usually requires an optimal location where there’s a good heat source under the Earth’s surface. Some locations are ideal for sourcing geothermal. For example, has access to heat under the earth and uses geothermal power as a sustainable source of energy for their campus. In addition, Petaluma, California has begun to be 100% renewable by partnering with a company that's helping to source geothermal energy via Sonoma County Geysers. Ball State University transitioning their power usage Since location plays such a crucial role, geothermal energy is not always accessible for everyone. Thus, it hasn’t gotten the attention that other renewables have. However, to combat the climate crisis, the energy sector must find solutions. Fossil fuels like oil, coal and gas are still predominant in the United States — they comprised in 2019. That number needs to drop drastically to see environmental improvements. 80% of U.S. energy consumption The Tech That Changes Everything Traditionally, geothermal energy uses an open-loop dynamic where the system pumps up water or steam and uses the heat as electricity. Though it’s a sustainable option, water and steam are still valuable resources. The open-loop loses some along the way as it pumps it all back down into the Earth. A closed-loop heat pump is a better option. Once energy experts combine that system with new technology, geothermal becomes reliable and a more practical energy option for everyone. In a closed loop, the water and steam cycle through the pipes continuously. The system does not consistently take in new resources and only uses a set amount of water and steam. Analytics and sensors give energy professionals the power to monitor exactly how efficient a geothermal system is. They can predict energy demands as well as output, using sensors within the pipes and on the power grid. Before harsh weather or blackouts can occur, professionals use the tech to understand how much energy the system can pump out. Then, they can properly prepare for the incoming demand. However, the biggest and most vital aspect of closed-loop technology is that it can provide energy on demand. Professionals can have geothermal systems store and disperse energy without disrupting anyone else. The closed loop continuously heats and generates electricity, and the tech makes it more accessible. With this dynamic in place, a geothermal energy grid can vastly expand and cater to people or businesses no matter their location. Some were surveyed as accepting of geothermal energy with environmental concerns. With innovations coming to light regarding risk minimization, more companies are becoming interested in this energy. For instance, recently backed Eavor Technologies, a startup specializing in this specific tech for geothermal energy. European and American countries BP and Chevron Geothermal for Innovation With the new technology in place, geothermal energy becomes an innovator for its sector. It can push forward larger-scale adoption of clean energy since it’s now a more accessible option. Moreover, geothermal generation helps public health and the economy. The COVID-19 pandemic has stressed the importance of clean energy, positioning geothermal as a profitable source in the next few years. Also, the unemployment rate is from April 2020’s record high. The energy sector can stimulate the economy for a green recovery by channeling new resources and tech into geothermal. Since this kind of work requires people of all backgrounds — tech, energy, environment, contracting, marketing, finance — adding jobs will be an all-around beneficial move. still slowly coming down As renewables and geothermal’s new tech increase in popularity, fossil fuels can slowly fade to the background. New geothermal tech readies the energy sector for faster integrations in households, communities and businesses. Tech Leads to Big Changes Ultimately, the tech integration starts small. Smart analytics and sensors help energy professionals more easily control supply and demand levels. As professionals use that control to supply more people with power, public health, the economy and the environment all benefit.

How Geothermal Technology Is Redefining the Energy Sector

Before the pandemic, around the world. Yet, the pandemic and the movement restriction measures that aimed to protect public health and growing consumer preference to avoid physical stores have led to a massive shift of consumers to digital channels for shopping. And, this significant shift towards online shopping has been accompanied by the increasing adoption of digital payments. e-commerce was growing at a steady pace of 4.5% a year Services such as digital payments, credit, and insurance are all increasingly being offered at the point of sale by digital providers or non-financial companies, a trend known as embedded finance (more on this one later). In other words, the pandemic acted as rocket fuel for digital transformation, providing an opportunity for the payments industry to innovate and adapt to modern retail needs. So, after a year of such rapid transformation, what can we expect to see in 2021 when it comes to the payments industry? Keep reading below to find out how the pandemic has altered consumer behaviors in terms of online payment preferences and the trends we're expecting to see more of this year. Online shopping has changed mindsets on payments With online shopping on the rise since the beginning of the pandemic, we can absolutely say that non-traditional payment methods such as bank transfers, e-wallets, cash-based digital payments, and local credit cards have experienced huge growth. In fact, they are now the prevalent payment methods around the world, being used in over . 70% of all online transactions During the pandemic, data shows that consumers were also more inclined than ever to use different payment methods in the search for the best convenience and security during national lockdowns. More precisely, data shows that 56% of global consumers reported that . they had used a new local payment method in the first month of the pandemic One payment method that thrived particularly during the pandemic was the interest-free "buy now pay later." believe that the availability of "buy now, pay later" matters a lot for how much they spend with retailers. Data shows that 44% of US consumers One of the reasons why the "buy now, pay later" payments method has seen so much popularity lately is because the pandemic has brought job losses and unprecedented financial strain to consumers. Therefore, consumers prefer the flexible nature and lack of financial penalties of "buy now, pay later" payment tools. A more competitive market in an increasingly digital business environment McKinsey described the massive boom of global e-commerce as the " ," representing a 10-year shift in e-commerce that happened in just 90 days. Data shows that during June last year when the entire world experienced the strictest lockdowns, e-commerce sales saw a 34% increase year-over-year. This is the highest growth rate reported since March 2008. quickening effect But here's the deal: many consumers didn't turn to their trusted business during this critical period caused by lockdowns. Instead, they . This created major disruptions in brand loyalty, creating a wealth of opportunities for small and big businesses, encouraging them to take their operations online and across borders. Even Facebook understood that and launched its own shopping feature to support small businesses to sell to customers. turned to new retailers Now, it's evident that this digital surge in online shopping will continue to grow, even after lockdown restrictions will be lifted by authorities. Yet, in 2021, merchants who want to stay competitive and stand out from the crowd in e-commerce's new standard must support more than only card transactions. Don't believe us? New research suggests that 42% of US consumers will abandon their shopping carts if their preferred payment method isn't available at the checkout step. So, retailers need to expand their current payment offerings more to satisfying changing needs and preferences of consumers. 4 Payment Trends To Watch Our For in 2021 Are there any payment trends we're expecting to see more of this year? Yes, quite a lot of them! 1. Improved payment-processing partnerships One of the trends we're expecting to see more of these days is that merchants will start to reconsider the effectiveness of their payment-processing partnerships. Now, more than ever, they need to make sure that they have a high-performing payment infrastructure to accommodate the shifts in payment volume. Online retailers will likely look for superior payment processing platforms for their websites and mobile apps, such as , to collaborate with to accommodate the needs of their customers. Payment for Stripe mobile point of sale app 2. Fraud prevention strategies and CX will team up What's more important: to provide a great customer experience to your audience or keep their data safe? If you didn't answer "both," you need to think twice. Data suggests that make it difficult to provide an excellent customer experience. 57% of online retailers agree that their efforts for fraud prevention Yet, in 2021, we expect security experts that collaborate with retailers to find better fraud-prevention strategies that also allow a smooth CX. 3. Embedded finance will grow further As we've promised above, we'll discuss a bit about embedded finance. by non-bank providers such as ridesharing companies, consumer-focused fintechs, telcos, or large consumer tech companies. These providers offer different financial services such as integrated payment processing, debit cards, instant payouts, digital wallets, or installment loans. Embedded finance refers to softw are and applications peddled We expect the embedded finance opportunities to only grow this year. 4. QR codes are making a comeback QR codes had their best days back in the 2010s but have since fallen out of fashion for open-loop payments. Yet, in 2021, as part of retailers' no-contact checkout strategies, we're expecting QR codes to make a comeback. After a year of steady e-commerce growth and a significant shift towards online shopping, consumers are increasing their adoption of digital payments. We should expect to see more innovation in online payments. Lead Photo by rupixen.com on Unsplash

Online Retail Innovation: Here's What 2021 Has In Store For Payments After The Digital Boom In 2020

It’s been the dream of many space enthusiasts from the 1960s to live in an intelligent artificial gravity space station ever since it was popularized by NASA chief scientist Von Braun and the legendary film: ‘Space Odyssey: 2001’. Unfortunately, generating artificial gravity for astronauts was not a priority for NASA as astronauts were able to reduce some of the impact of weightlessness on their bodies thanks to a ruthless exercise regimen. Further, a ship that contains a centrifuge for generating artificial gravity would be extremely expensive to launch to orbit. So, NASA ended up sticking with a compact and modular station that is more affordable with their budget and that doesn’t deal with weightlessness risk and accepted the risks it posed to astronauts in the international space station. Below is a comprehensive list of health risks astronauts face in the zero-g space station. Weightlessness risks are highlighted in the red box. Src: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150009516.pdf Over the past few years, new reports have come out that most astronauts are now facing visual impairments, immunosuppression, osteoporosis, and risk potential brain damage that cannot be tackled by their exercise regimen. Currently one of the biggest concerns is VIIP (Visual Impairment/Intracranial Pressure) syndrome which structurally changes the shape of the eyeball and in some cases can create blind spots. Reference: Alperin N., Bagci A.M. (2018) Spaceflight-Induced Visual Impairment and Globe Deformations in Astronauts Are Linked to Orbital Cerebrospinal Fluid Volume Increase. In: Heldt T. (eds) Intracranial Pressure & Neuromonitoring XVI. Acta Neurochirurgica Supplement, vol 126. Springer, Cham Japanese Space Agency (JAXA) ran an experiment with mice onboard the ISS Kibo. Src: iss.jaxa.jp Centrifuges were used to generate artificial 1G gravity. It was found that the artificial gravity generated did, in fact, negate the effect weightlessness had on visual impairment. Below are the CAD model and cross-section of the centrifuge used by JAXA to carry out the experiments. For context: radius= 0.15m, centripetal acceleration=9.81m/s^2, angular velocity= 77.2 rpm Artificial gravity centrifuge experiments on Kibo also found that mice lost less bone mass when in 1G artificial gravity. Src: https://iss.jaxa.jp/en/kiboexp/news/1205_0130_mouse.html Further studies have shown that there could be potential brain damage if the astronauts stay in weightlessness long enough. Src: MUSC researchers, press release: Dr  Michael Antonucci, at the Department of Radiology and Radiological Science at MUSC said https://www.telegraph.co.uk/science/2017/11/01/humans-may-need-fake-gravity-reach-mars-without-brain-damage/ “Designing a space vehicle with artificial gravity might be a way of minimizing the changes that occur in a microgravity environment.” Further, “Artificial gravity does not countermeasure for just one thing; it addresses all physical systems,” says Gilles Clement, the lead scientist for artificial gravity in the Human Health Countermeasures Element of the Human Research Program at NASA’s Johnson Space Center in Houston. Intelligent artificial gravity space stations and spacecraft for long stays in space The solution to weightlessness related health issues? Src: Nautilus-X potential design by NASA Critical innovations and technologies to bring such space stations to reality (current and pending) 1. Decreasing the cost per kg substantially (pending) For massive structures (artificial gravity space stations) to be built in space, it has to be first affordable to do so. Previous rockets were just too expensive to allow any government entity to sustainably fund a massive space station. Even the international space station is an international government effort to reduce the financial burden on any single government. Reusable rockets are changing the game when it comes to making space accessible. Below is a chart referencing the estimated cost per kg for some famous rockets. SpaceX’s BFR which is currently in the design and prototype stage might further drop the cost per kg to LEO to a few hundred dollars when it’s in full use. This could be a game changer. src: SpaceX 2. Decreasing the total mass of the space station to reduce the cost of launch substantially (pending): There are 2 proposed ways structures can be built with high strength and low mass: Tensegrity and Trusses. Tensegrity is ‘the characteristic property of a stable three-dimensional structure consisting of members under tension that are contiguous and members under compression that are not.’ src: Oxford NASA recently funded research on tensegrity approach to building an artificial gravity space station NASA is even considering using tensegrity rovers for planetary missions in the future. Trusses: the engineering definition ‘a structure consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object’ Src: stairville Trusses can be easily folded or be disassembled in a modular way to be reassembled in orbit. For example: The main support structure on the ISS is a truss. Different sections of the truss were brought on different space launches. So the main spokes and rim of the artificial gravity space station can be designed as trusses in order to reduce weight and join them together in a modular fashion. For starters, it can also be a truss mast which spins on the center. Src: Canadian space agency A perfect low weight design has yet to be perfected but would be a game-changer. Ref: NASA's Multigenerational Independent Colony for Extraterrestrial Habitation 3. Intelligent gimbals to point solar panels toward the sun (current) Beta Gimbal Assemblies (BGA) Bearing Motor Roll Ring Module (BMRRM). These gimbals are critical to sustain the presence of the station in space. Pointing the solar arrays to the sun allows the station to have electricity around the clock. Electricity is essential to maintain operations and power onboard electronics and other embedded systems These gimbals can be set up in an open-loop control or be part of an intelligent system where it is a closed feedback loop with sun tracking sensors (like Adcole). 4. Reaction Control Thrusters with PID control & sun sensors to control and monitor the spin rate (current) It is critical that the space station has a stable spin rate. Hypergolic RCS (Reaction control system) thrusters similar to R-4D can be used on each end of the mast of the intelligent artificial gravity station to control the spin (seen in picture - RCS thrusters on the end of the mast) Further, ADCOLE Coarse Sun Sensors positioned along the truss will help us monitor the spin rate of the station by calculating how much time it takes for the Adcole sensor to view the sun twice in its field of view. ref: Coarse Sun Sensor Detector (Cosine Type) ‘The Coarse Sun Sensor Detector is a single detector model used for applications including solar array pointing, sun acquisition, and failsafe recovery.’ src: adcole.com The RCS thruster and the Adcole sensor can be potentially set up in a PID control loop such that based on feedback from the Adcole sun sensor, the RCS thruster can do spin rate corrections.

Main Reasons To Build Intelligent Space Stations With An Artificial Gravity

The voltage follower , as shown in Figure 1, uses virtual short and virtual break. At first glance, it seems simple and clear. If you think that there is not much content to pay attention to, then you may be wrong. Understanding the op amp's voltage-following circuit is a great help for understanding the op amp's in-phase, inverting, differential, and various op amp circuits. circuit of the op amp Figure 1 op amp voltage follower circuit Voltage follower circuit analysis If we connect the output of the op amp to its inverting input and then apply a voltage signal to the noninverting input, we will find that the output voltage of the op amp will follow the input voltage very well. Assume that the input and output voltages of the initial state op amp are both , and then when Vin increases from , will also increase in the direction of positive voltage. This is because it is assumed that Vin suddenly increases, still has no response and is still . is greater than 0, so multiply the open-loop gain of the op amp. , so that the output of the op amp begins to increase in the direction of the positive voltage. 0V 0V Vout Vout 0V Ve=Vin-Vout Vout=Ve*A Vout When increases, the output voltage is fed back to the inverting input, which then reduces the voltage difference between the two inputs of the op amp, ie, will decrease, in the same open-loop gain case. Next, will naturally decrease. Vout Ve Vout The end result is that no matter how large the input voltage is (of course, within the op amp's input voltage range), the op amp will always output a voltage that is very close to , but this output voltage is just below . There is a sufficient voltage difference between the two inputs of the guaranteed op amp to maintain the output of the op amp, which is . Vin Vout Vin Ve Vout=Ve*A Negative feedback in op amp circuits This circuit will soon reach a steady state, the amplitude of the output voltage will accurately maintain the voltage difference between the two input terminals of the op amp, which in turn will produce an accurate amplitude of the op amp output voltage. Connecting the output of the op amp to the inverting input of the op amp is called negative feedback, which is the key to self-stabilizing the system. This applies not only to op amps, but also to any common dynamic system. This stability allows the op amp to have the ability to operate in a linear mode, rather than just being saturated, fully "on" or "off", just as it is used for comparators without any negative feedback. Due to the high gain of the op amp, the voltage maintained at the inverting input of the op amp is almost equal to . For example, an op amp has an open loop gain of 200,000. If is equal to 6V, then the output voltage will be 5.999 970 000 149 999V. This produces a sufficient voltage difference at the input of the op amp, =6V-5.999 970 000 149 999V=29.999 85uV, which is amplified and then produces a voltage of 5.999 970 000 149 999V at the output, thus the system Will be stable here. Vin Vin Ve As you can see, 29.999 85uV is a small voltage, so for practical calculations, we can think that the voltage difference between the two inputs of the op amp maintained by negative feedback is . The whole process is shown in Figure 2. This is also the “virtual short” we are familiar with, and since the impedance between the two inputs of the op amp is very large, there is naturally a “virtual break”. The circuit below has a stable double-loop closed-loop gain, and the output voltage simply follows the input voltage. Ve=0V Figure 2 The role of negative feedback One big advantage of using negative feedback is that we don't have to worry about the actual voltage gain of the op amp, as long as it is large enough. If the op amp's voltage gain is not 200 0000 but 250 000, this will cause the op amp's output voltage to be closer to , and the voltage difference between the smaller inputs will be used to produce the desired output voltage. In the circuit illustrated in Figure 2, the output voltage is also equal to the input voltage at the inverting input of the op amp. Therefore, for the circuit design engineer, in order to achieve a stable closed-loop gain of the amplifier circuit, the open-loop gain of the op amp does not have to be an accurate value, and the negative feedback causes the system to self-adjust. Vin Using negative feedback improves linearity, gain stability, output impedance, and gain accuracy, but using negative feedback also poses a serious problem, which is to reduce system stability for voltage-following circuits with unity gain. This is the worst case scenario, especially when driving capacitive loads, interested students can check the relevant information themselves. Regarding the op amp circuit, many times we are infused with the inverting end to follow the in-phase end. As mentioned above, can't we follow the inverting end of the phase? For the voltage follower circuit mentioned today, only the inverting terminal follows the non-inverting terminal. Here, if a positive input voltage is applied to the inverting terminal and the output is connected to the non-inverting terminal, and the output is assumed to be 0. will be a negative voltage, multiplied by the open-loop gain of the op amp, and the output will be a A negative voltage, returning to the non-inverting input of the op amp, will further result in a larger negative absolute voltage difference. Soon the output of the op amp will be saturated, and naturally the in-phase will not follow the inverting end. Ve However, for an op amp, if a reference voltage is applied to the inverting terminal, and other electronic components, such as a triode, MOS, etc., the overall loop of the op amp forms a negative feedback, and the in-phase end can also follow the inverting end. And this naturally breaks the rule that the inverting end of the familiar op amp follows the in-phase end. The voltage of the op amp follows the circuit, "virtual short", "virtual break" is the surface, and negative feedback is the root. Based on this root, it can help us understand the ever-changing op amp circuit.

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