nick-the-cheme

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Bose Headphone Noise Canceling Technology (‘Deep Dive’ on Process Control)

Whenever I go to the library or café to study, I often use my Bose noise canceling headphones to block out the sounds of my environment.  It helps me focus a lot better, and if I decide to play music, I don’t have to worry about annoying ambulance alarms or passing cars or any of the disturbances that characterize everyday New York. I recognize that active noise cancelling (ANC) technology employs a classic example of process control. ANC is based on the principle of phase cancellation, a phenomenon in which waves of equal magnitude and opposite phase cancel each other out when added. ANC headphones record the background noise, invert the noise signal to create “anti-noise,” add it to the output signal (which can include the music) and deliver the “filtered” output signal to a user’s ears.

For my Bose headphones, I can specify the level of cancellation desired through a feature on the Bose app, which then reduces background noise level to anywhere between one-quarter and one-sixteenth of the original input. This corresponds to my set point. Tiny noise-capturing microphones must then sample ambient sounds accurately enough to provide the needed amount of attenuation. As such, these systems need to be finely tuned to respond to incoming disturbances effectively and near-instantaneously. In process control terms, the headphone controller must minimize offset (ambient sounds are cancelled by the produced anti-noise) and minimize time response (tuning occurs faster than or at the speed of music delivery).

There are also two forms of ANC technology analogous to the open- and closed-loop tuning methods discussed in class. Feedforward ANC (think open-loop Cohen-Coon) places the noise-capturing microphones on the outside of the headphones to map the raw incoming noise signal. External microphones typically have the best noise sensitivity and can isolate specific sounds like traffic. However, this also means that feedforward ANC is more sensitive to wind howl and other forms of incidental noise. Feedback ANC (think closed-loop Ziegler-Nichols) places the microphones on the inside of the headphones to more accurately sample the ambient sounds the user will actually hear. This makes feedback ANC self-correcting and more resistant to incidental noise, but also more susceptible to inadvertently capturing the user’s audio and cancelling desired frequencies. Luckily, Bose employs a hybrid of the two to give consumers like me the best of both worlds!

Source: https://www.soundguys.com/noise-canceling-anc-explained-28344/

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Driving with Honda’s ECON Button (Process Control in My Life)

I drive a Honda Civic when I’m back home for holidays in Miami. A cool feature on my car I make regular use of is the ECON button, designed to help Honda owners save money on gas by calibrating vehicle systems to maximize fuel efficiency. I hadn’t thought too much on how this feature worked until now, but if ECON mode automatically changes the settings on different systems in my car to maximize fuel economy depending on my driving patterns, it must employ some form of process control.

Honda reports there are three main settings ECON mode manipulates: throttle, cruise control, and air conditioning. Throttle response is changed at highway speeds to help reduce acceleration, as accelerating burns fuel the fastest. When I hit the gas pedal on ECON mode, there is often a longer time delay and slower increase to my target speed. ECON mode thus teaches my car to respond to gas pedal disturbances slower than normally. When I turn on cruise control, my car is less likely to downshift gears to maintain set speed. This means there will likely be more variation around set point and my speed will vary by a couple miles per hour. ECON mode thus teaches my car to be more lenient with any offset. Finally, when ECON is engaged, the air conditioner compressor will turn on and off more often. This means it will likely take more time for the car to cool (which can be brutal in the sweltering South Florida summer), but it won’t expend fuel as rapidly because A/C will occasionally turn off when it senses the temperature in my car is already at target.

ECON mode is a fascinating feature because it optimizes a parameter that makes individual control systems ostensibly “worse” at control. ECON deliberately instructs the throttle, cruise control, and A/C systems to either respond slower or with greater offset in order to save money at the pump. I feel this example best illustrates how the “best” form of control is often a contextual one. It entirely depends on what the user prioritizes at the moment of use. For a college student with minimum income, it appears less control is my priority!

Source: https://www.kirklandhonda.com/what-is-honda-econ-button/

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The Chemtool Chemical Fire in Rockton, Illinois (Process Safety in the News)

This past summer, an explosion at a chemical plant in Rockton, Illinois resulted in a chemical fire that forced evacuations of the entire community. The explosion was caused by a scissor lift accident in which an operator likely struck a valve or pipe “with sufficient mechanical force to cause the release of mineral oil." Although accidental, this can still arguably be considered a process safety violation, as scissor lift operation requires significant spatial awareness and machinery training. Luckily, many emergency protocols were followed immediately after the spill was detected. Operators "promptly shut down the boiler,” began “placing containment booms” and “depressurizing the heat transfer piping network” right before the fire ignited. Officials at the plant immediately notified the fire department to issue a one-mile radius evacuation. Around 70 plant employees were also evacuated before fire-fighters arrived. Anyone within three miles was instructed to wear a mask because of excessive smoke.

The company, Chemtool, manufactures more industrial grease than any other plant in the country, so onsite hazardous chemicals like lead and sulfuric acid posed a significant environmental threat to nearby areas. This prompted plant officials to inform the Rockton fire department to avoid using water for suppressing the flames, as runoff would likely carry these toxic chemicals into the nearby river and groundwater. A private industrial firefighting crew from Louisiana with experience fighting refinery fires was called in to release a fire-retarding foam instead.

The Chemtool chemical fire illustrates the importance of all plant employees being aware of all fire safety protocols to avoid excessive disaster. The fire in Rockton was contained because of the mobilization efforts of operators, engineers, and fire-fighters. Operators responded promptly with the appropriate de-escalation methods, all other employees quickly evacuated once they were informed of the fire, and city officials informed the community to evacuate and seek out necessary safety precautions to decrease risk of smoke inhalation. Environmental disaster was also avoided through the use of foam rather than water to extinguish the fire. (Engineers at my summer internship in Minneapolis even used the Chemtool example to emphasize the importance of fire safety training at the pilot plant, so hopefully this blog post will help readers be more aware as well!)

Source: https://www.nbcchicago.com/news/local/rockton-il-chemical-plant-fire-likely-caused-by-scissor-lift-accident/2541335/?amp

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Smart Insulin Patches for Diabetes Treatment (Process Control in the News)

In 2020, a team of bioengineers at UCLA developed a smart adhesive diabetes patch that monitors blood sugar and delivers insulin for a rapid response when the sensor detects a glucose spike above a certain threshold. The rate of insulin delivery also slows down when blood sugar levels are near the normal set point to prevent overdose. In that sense, it mirrors the regulatory function of a working pancreas!  

The team developed the smart patch because the current treatment for diabetes is “inconvenient.” Patients must manually draw blood using a needle and cellphone-sized device to measure glucose levels. Insulin must then be injected with a syringe or pump attached to the body. In other words, there is no form of automatic control on the system. Patients administer the blood sugar test and insulin injection once every few hours when glucose levels might have already become life-threatening.

The smart patch takes advantage of faster, more sensitive feedback control to maintain glucose levels at steady state. Once applied to the skin, microneedles made with a glucose-sensing polymer release insulin when triggered. They measure glucose levels in live-time and adjust rate of release accordingly. Although the current manual system is somewhat a form of feedback control, the patient no longer has to wait hours for a sensor (blood sugar test) to relay output information to some process control variable (insulin injection amount). Additionally, there is significantly decreased risk of overshoot (insulin overdose) because the rate of release instantly adjusts in response to glucose concentration. Human trials are likely to start within the next couple years.

Source: https://www.healtheuropa.eu/smart-wearable-insulin-patch-could-revolutionise-diabetes-treatment/98142/

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Day in the Life of a Process Control Engineer (Process Control YouTube Video)

Kaylin is a process control engineer at Chevron in Houston, Texas. She says that her primary role is to make sure that the computer systems are operating at their best on a daily basis. At the Process Automation Center (PCA), she describes the variety of computers and instrumentation she works with, including everything from temperature and pressure regulation to flow rates and composition. “I like to think of my job,” she shares, “as helping Operations make their jobs as easy as possible so that they can run safely, reliably, and profitably.”

Kaylin tells us that one common processing issue at crude oil refineries is slugging, or the accumulation of oil/condensate in a gas pipeline. Sensors at the plant report this data to PCA and Kaylin can watch in real-time on her computer. She then simulates various parameters (perhaps a form of PID control) to determine the optimum operating conditions to reduce and eliminate the slugging. Kaylin immediately informs the plant of these optimized parameters and thus helps prevent shut-in. “That’s my favorite portion of my job,” she says, “the immediate gratification of helping a facility now, because the facilities are physically there, and we have to maintain them through their life.” It seems that Kaylin and I share a value for “tangible solutions,” as that is precisely what got me interested in chemical engineering to begin with. The problems that process control engineers like Kaylin encounter are solved as they occur, so Kaylin can leave work feeling that she “accomplished something today.” As someone who will be working in process engineering after I graduate, I hope to share that feeling as well.

Source: https://www.youtube.com/watch?v=kK_8gvijNPI