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A building must meet requirements related to energy usage and good indoor environment. The building ́s ventilation system aims to maintain optimal air quality, thermal condition, and efficient energy usage. By being able to control and adjust airflow as needed with a Variable Air Volume (VAV) system, energy usage of the ventilation system can be reduced without sacrificing indoor air quality. The VAV system operates with a variable airflow, so the accuracy of the VAV terminal at low flows is important. The study aims to verify the accuracy of three different methods for measuring airflow: iris damper, hot- wire anemometer, and volume flow hood. Data collection was carried out through measurements in a laboratory environment. The collected data were managed in the Excel spreadsheet program. The three methods were tested on a prototype consisting of a supply airline and an exhaust airline, each equipped with a VAV unit that varied the airflow through a potentiometer, allowing different airflow values to be obtained for the experiment. The results of the iris damper method were chosen as reference for the other methods due to its ability to predict results using manufacturer tables, which provide useful information about airflow values when varying pressure drop and the iris damper loss k-factor. In this way, set points were stablished for all tests. Two experiments were conducted with different set points. In retrospect it is acknowledged that an air flow meter of higher accuracy had been needed to ascertain the results of the study. That said, the attained results indicate the following: In the experiments, measurements were taken for 12 different airflow values, ranging from 200 l/s to 20 l/s. The test results showed that the most inaccurate method was the volume flow hood, with an average error ranging from ±19% to ±49%, followed by the hot wire anemometer, which had a measurement error between ±15% to ±18%. The high inaccuracy of the volume flow hood was due to a lack of instrument recalibration, resulting in highly inaccurate measurements. All methods showed lower uncertainty between 20 l/s and 50 l/s. Finally, it was verified that the iris damper method improved its average reading error by increasing the pressure drop across the damper and reducing its loss k-factor, achieving the lowest error of the entire experiment at ±12%.

Successful race teams rely heavily on track testing to search for the ideal suspension setup. As more restrictions are placed on the amount of on-track testing by major racing sanctioning bodies, such as NASCAR, teams have increased their attention to alternate testing methods to augment their track data and better understand the dynamics of their racecars. One popular alternate to track testing is 8-post dynamic shaker rig testing. Eight-post rig testing gives the team a better understanding of the vehicle's dynamics before they arrive at the race track, allowing them to use their limited track testing time more efficiently. While 8-post rig testing certainly is an attractive option, an extensive test matrix is often required to find the best suspension setups. To take full advantage of 8-post rig tests, more efficient experimental methods are needed. Since investigating shock absorber selection is often the most time-consuming task, this study focuses on developing more efficient methods to select the best shock absorber setups. This study develops a novel method that applies dynamic substructuring and system identification to generate a mathematical model that predicts the results of future tests as both command inputs and components are changed. This method is used to predict the results of 8-post rig tests as actuator commands and shock absorber forces are varied. The resulting model can then be coupled with shock absorber models to simulate how the vehicle response changes with shock absorber selection. This model can then be applied to experimental design. First, a physically-motivated nonlinear dynamic shock absorber model is developed, suitable for quickly fitting experimental data and implementing in simulation studies. Next, a system identification method to identify a vehicle model using experimental data is developed. The vehicle model is then used to predict response trends as shock absorber selection is varied. Comparison of simulation and experimental results show that this model can be used to predict the response levels for 8-post rig tests and aid in streamlining 8-post rig testing experimental designs. / Ph. D.

The design of nonlinear adaptive control systems for reducing vibration transmission in applications such as transportation systems is discussed. The systems studied include suspension systems, such as those used in vehicles, employing nonlinear magneto-rheological (MR) dampers that are controlled to provide improved vibration isolation. Magneto-rheological dampers use a novel class of smart fluid whose apparent viscosity changes as it is exposed to a magnetic field. The developed adaptive control scheme is designed to deal with the nonlinearities and uncertainties that commonly arise in most suspension applications. Some of the nonlinearities that are considered include time-varying characteristics, displacement-dependent effects, and hysterisis damping of magneto-rheological dampers. The uncertainties include mass and stiffness variations that can commonly occur in a suspension system. A number of nonlinear analytical models are developed and used in numerical simulation to evaluate the validity and effectiveness of the developed adaptive controllers. Further, the results of the numerical study are used in an experimental evaluation of the controllers on a seat suspension for heavy vehicles. The analytical and experimental evaluation both indicate the effectiveness of the proposed adaptive control technique in controlling vibration transmission in the presence of both system nonlinearities and uncertainties. The manuscript will provide a detail account of the modeling, dynamic analysis, adaptive control development, and testing that was performed throughout this study. / Ph. D.

This study proposes various methods to harvest the mechanical energy present in railcar suspensions and railroad tracks to generate electricity that is suitable for onboard or trackside electronics, using electromagnetic generators. Compact electromagnetic energy harvesters that can be installed onboard railcars or wayside on railroad tracks are designed, fabricated, and tested. The designs integrate a mechanical motion rectifier (MMR) with embedded one-way clutches in the bevel gears in order to convert the bi-directional mechanical energy that commonly exists in the form of vibrations into a unidirectional rotation of the generator. The ball screw mechanism is configured such that it has reduced backlash and thus can more efficiently harvest energy from low-amplitude vibrations. Two prototype harvesters are fabricated and tested extensively in the laboratory using a suspension dynamometer and in the field onboard a railcar and on a test track. A power management system with an energy storage circuit has also been developed for this onboard harvester. The laboratory evaluation indicate that the harvesters are capable of harvesting power with sufficient current and voltage for successfully powering light electronics or charging a low demand battery pack. The harvested power varies widely from a few to tens of Watts, depending on the resistive load across the harvester and the amplitude and frequency of the mechanical motion. The laboratory test results are verified through field testing. One harvester is tested onboard a freight railcar, placing it across the wedge suspension, to use the small amount of relative displacement at the wedge suspension to harvest energy. A second harvester is placed on a test track to use the vertical motion that occurs due to passing wheels for wayside energy harvesting. Both onboard and wayside tests confirm the laboratory test results in terms of the success of the design concept in providing low-power electrical power. The harvester design is further integrated into a conventional railroad tie for ease of field installation and for improving the efficiency of harvesting the mechanical energy at the rail. The integrated design, referred to as the "smart tie," not only protects the energy harvester, the wiring harness, and supporting electronics from the maintenance-of-the-way equipment, but also positions the harvester in a mechanically advantageous position that can maximize the track-induced motion, and hence the harvested power. Although for testing purposes, the smart tie uses a modified composite tie, it can be integrated into other track tie arrangements that are used for revenue service track, including concrete and wooden ties. A prototype smart tie is fabricated for laboratory testing, and the results nearly surpass the results obtained earlier from the wayside harvester. The smart tie is currently being considered for revenue service field testing over an extended length of time, potentially at a railroad mega site or similarly suitable location. / Doctor of Philosophy / This dissertation proposes three different electromagnetic energy harvesters for harvesting railroad track and railcar suspension vibration energy. The concept is similar to what you may have seen in self-powering flashlights that are often advertised in late-night TV commercials. You shake the flashlight vigorously, which moves an energy harvester devoice and, Voila, the light bulb comes on. The device design in this study uses the mechanical energy that is present in a vehicle or at a railroad track to harvest the mechanical energy that is naturally present in the form of electrical energy, which can then be used for powering electronic devices and sensors of various kinds. Such sensors and electronics would help with improving the operational efficiency of railroads. The energy harvesters can be installed onboard a railcar or at the track. In either case, the movement of the train creates a small amount of vibration energy that is turned into electrical power. When onboard a train the power can be used for sensors, GPS, and similar devices to allow the operator to better monitor the condition and location of the train. Note that most railcars, especially the freight railcars, do not have any onboard electrical power. Similarly, the energy harvester can be installed at the track to convert the small amount of up and down motion that happens with the passing of each wheel into energy that could be used for integration of sensors that make the track "smarter." This means that the sensors can potentially alert the engineers who are responsible for monitoring the track of an existing or impending problem with the track. Both the railcar and track integration of the energy harvester that is designed, fabricated, and tested during this study are exciting concepts that can improve the rail industry in the U.S. This document includes the details of designing efficient energy harvesters, specifically for rail applications. A prototype of the energy harvester is fabricated and tested extensively in the lab and in the field, albeit to a more limited extent. The test results were quite successful, which is why I am telling you about them! Both the laboratory and field test results show that the device holds significant promise for rail applications.