Thermostats are essential for keeping a home cozy and tidy. However, traditional thermostats are unable to respond directly to an environment, making them inappropriate for the increasingly dynamic nature of modern building energy management. So how can we use our engineering mindset to configure thermostats that can adapt readily to their environment? Well, what if we were to make smart thermostats with real-time sensors that can collect data about the surrounding environment and make snap decisions, such as adjusting the temperature and introducing local zones, as well as be controlled from an external device? Well, it turns out that this is being carried out in everyday life, with new smart thermostat companies popping up all over the world from the heart of Silicon Valley to the streets of London.
“How exactly can we model loads that are controlled by thermostats?”
Machines take energy from the grid under many parameters. And some of them are controlled by environmental temperatures, such as temperature. And a portion of these units (such as HVAC systems, water boilers, and refrigerators) try to match their setpoints to a value on a thermostat. These machines are known as thermostatically controlled loads and are used in grid-building system modeling to generate predictions about demand side energy usage.
“How can we control the flow of air in an HVAC system?”
Many HVAC air systems operate by regulating the flow of air into a space. But how can we do so? Well, what if we were to use our engineering mindset to create a duct that would control the amount of air that would be transferred? This is known as an HVAC Damper and is commonly implemented in Variable Air Control Systems.
While Constant Air Volume HVAC Systems are affordable, they are not the most optimal solution. They don’t have the most precise temperature control, their fans can be noisy, and they can consume a large amount of energy. So how can we use our engineering mindset to solve this problem? Well, what if we were to have our air temperature be constant instead of our air supply? This would allow us to change the air temperature at a specified rate, allowing us to save money, energy, noise, and wear. This system is known as a Variable Air Volume HVAC System and is used in building systems all over the world.
“How can we measure the difference between a control signal and a half phase shift?”
When working with electronic amplifiers, the phase of an input signal might be shifted, which might introduce instability. And if this phase shift is greater than 180 degrees, then the system will be unstable. To standardize all measurements, electronics researchers have introduced the concept of a phase margin, or how far off from a 180-degree phase shift this new phase is. The phase margin can be calculated with the simple equation P_margin = |180-phase|.
“What is the margin of stability for a gain Bode Plot?”
One of the most useful features of a Bode Plot is the ability to find the stability of a system. One way to do that is to find the frequency at which the phase shift becomes 180 degrees, get the amplitude of the gain at the point, and then make a gain margin extending out to both sides equal to the magnitude of 1/|Amplitude value|, such that anything within that range will be stable.
“Can we have built-in time delays into control systems?”
When working with control systems, sometimes we don’t want all actions to occur instantaneously. For example, we might want to have an elevator door wait to close a few seconds after everyone has entered. This can be modeled as a time shift within the system. A time shift for a function in the time domain can be represented by f(t) = x(t-tau) where tau is the time constant and in the Laplace domain by the equation f(s) = e^(-tau*s) *X(s).
“What is the maximum amplitude of an oscillating system?”
In the physical world, systems can vibrate at different frequencies with different outputs. But when the system achieves maximum vibration at a certain frequency, it is called a resonance. Resonance has large impacts on the design of systems, from constructing electrical circuits to achieve certain characteristics to analyzing vibrational characteristics of bridges
“How can we make controllers that deal with uncertainty?” In an ideal implementation, controllers will have to deal with no uncertainty. However, reality is not always as nice as we would like it to be, and often times things happen that we can not prepare for. Because of this, controls engineers have invented something known as robust control to deal with such events. Robust control works by having an internal operation error boundary such that any system can handle any stimulus within the zone of error.
Isaac's Science Blog 