controllers have also been suggested. One type fuzzy controller for building control has been designed with a pre-determined cost function that incorporates the major factors of interest to the control designer with relative importance weightings . Simulations performed by the researchers have indicated that this fuzzy control system can be effective at tracking set points under variable external loads, but it does not incorporate individualized preferences or enable tailored controls. While the proposed system attempts to incorporate both HVAC and lighting systems, it is limited by its fully decentralized implementation. An adaptive neuro-fuzzy controller for lighting has also been suggested for an artificial lighting and automatic window blinds integrated controller that considers impacts to both lighting and HVAC systems though evaluation of both daylight and solar heat gain (Kurian et al., 2008). This system relies heavily on extensive training data sets, and although it is capable of considering both visual and thermal comfort in conjunction with energy savings, the tradeoffs between comfort and savings and relative weightings are not explicit. Genetic algorithms (GA) have also been suggested for in situ parameter updating for control decisions . The window blinds control scheme suggested by Guillemin et al. utilizes GA for nightly parameter updates. These updates are based on knowledge of manual overrides to the automated system, i.e. when window blind angle was set by the automated system but changed by the occupant. In this way the system adapts to the preferences of the occupants. This approach is useful for blind control because of the generally poor characterization of objective criteria for determining the preferred settings of blinds in daylit spaces with respect to known information including sun position and irradiance. This technique may have implications for other systems such as ventilation and temperature which have complex interactions with respect to comfort; however, with environmental conditions such as desktop illuminance where occupants are capable of explicitly specifying their preference, more reliable information can be gained by providing them with direct selection. As the algorithms for building control become more sophisticated, industry and research entities continue to develop the hardware and communication systems that implement algorithms. Web-based monitoring systems are of interest because
network are not required for the laboratory scale prototype but might be of service in a large-scale, real-world network. As Digi produces a drop-in, interchangeable ZigBee model to the 802.15.4 model, the prototype board could easily be upgraded to incorporate a ZigBee model if additional networking functionality is desired in a future application. The IEEE 802.15.4 protocol specifies a maximum data signal rate of 250 kilobytes per second and up to 65,000 nodes using local addressing. The necessary data shared within a zone in the wireless network are contained in short packets of less than 10 bytes. The small amount of necessary data transmission per additional node in the system implies that the zones could be scaled to be very large while maintaining fast zone-wide updating. However, the radios are limited in communication range and therefore data may require multiple hops to move between an edge node and the zone manager. With consideration of the need for multiple hops, the expectation of imperfect communication, which requires packets to often be sent multiple times, and the latency both within the wireless infrastructure and within the higher level unit software, a more realistic upper bound on the number of nodes per zone is on the order of 100. Implementing a zone on this scale also requires sufficient memory and processing power at the zone manager level to compute the optimal lamp settings for a problem of this size. The radio operates at 3.3 V in contrast to the 5 V supplied to the microcontroller. A second voltage regulator is employed to supply a constant 3.3 V to the radio and a voltage translator is used to moderate the communications between the radio and the microcontroller. The selection of the fluorescent ballast is important to the design of the lighting control interface. Unlike light-emitting diodes (LEDs) or incandescent bulbs, fluorescent lamps require very specific inputs to function properly and therefore require more sophisticated dimming hardware. With an LED, a direct current signal is simply turned on and off at a high rate with the proportion of on versus off time providing the level of dimming. An incandescent bulb can be dimmed by clipping the alternating current input for a selected width after the zero crossover points, twice per
messages and all radio settings can be changed in situ enabling the radios to change to whom they are communicating as necessary as they execute the individual tasks. In transparent mode, no additional information is provided to the units about the origin of the messages they receive. To remedy this issue, a packet structure is designed for this project. Packets typically include a byte indicating the length of the message; however, in this case the length information is unnecessary because each possible message is a command or sensor reading of the same length with one exception, the transmission of the utility curves from zone manager to building server. For the curve transmission case, the zone manager sends a “curve will be sent” command followed by a message containing the length of the data stream that is queued up for the next transmission. Upon receiving this specific message, the building server enters a state responsible for handling the subsequent data stream. In place of a message integrity check, the function that reads in the packet information verifies the packet header, the “unit to” byte, the “unit from” byte, and that message itself is an appropriate message for the current state and the units involved. If any of these conditions are not met, the message is discarded. To avoid missing important messages, the units receiving messages send acknowledgement commands to the units from whom they receive messages. The sending unit continues to issue the command until it receives an acknowledgement confirmation. Figure 3-7 depicts the packet structure used for wireless communication throughout the tiered system. Figure : RF Packet Structure. A/D Module and Sensor Signal Interpretation The Atmega64 built in Analog to Digital (A/D) converter is used for taking sensor measurements. This microcontroller has an 8-channel multiplexed analog input. The A/D module first waits to ensure no other lines on the multiplex are in use and then
The sensor response in voltage output is linear with the of irradiance from each source as both the response curve and the distribution of radiation from both sources are constant. Because the design of the system allows for the determination of the measured incident radiation due to the artificial source, the contribution to the sensor reading from natural light can be determined and thus the total sensor response can be decomposed into artificial and natural contributions. With the sensor response decomposed thusly, the contribution of each source to the human eye response can be evaluated similarly. For a commercial system it would be preferable to select a sensor more closely tailored to the visible light spectrum or incorporate light filtering films to the design of the sensor itself to address the variable spectral distributions of reflected light; however, for use in the laboratory test bed where the largest portions of measured light are direct light components this decoupling procedure is deemed sufficient. In order to determine the visible light contributions from the two sources, transformation factors are calculated. These factors are evaluated by comparing the numerical integral of the original emittance and spectral power distribution curves with the product of these curves and the relevant response curve. By comparing the results from the photopic curve and sensor response curve computations, the measured sensor response can be converted to the equivalent visible spectrum value. Using the response parameters for the selected sensor, the luminance value is computed using Equation 3-1. [3-1] D/A Module The hardware design for the digital-to-analog (D/A) converter enables direct and robust software implementation. The eight pins on the Atmega64 port C are connected in parallel with the eight input signal pins on the D/A allowing the port C pins positions, when initialized as digital output pins, to function as the bits of the control signal. The desired light level fraction is converted to a fraction of the maximum value represented by the eight bits, 255, and this value is written to port C.
In the energy trading rounds, the units start at their previous energy allocation levels and trade energy units based on relative utility level. The zones are divided into prospective buyers and sellers based on where they fall with respect to the average utility level, those who fall below are buyers and those who are above are sellers. There is no actual currency in the exchange of energy units; instead the units are exchanged based on the value each zone places on the particular unit of energy. In order for the buyers to “purchase” energy units from the sellers, their “buying price” is calculated in the same way the value was computed in the original energy allocation. The sales price for the sellers is similarly computed but is taken as the minimum average loss over losing up to three units of energy. In order for the exchange to take place, the buyer has to be willing to pay more than what the seller is offering. The trading could be designed in two ways. In one approach, the highest bidders buy from the lowest sellers until no buyers are willing to pay the purchase price. Alternatively, the maximum number of transactions can be forced to occur by matching as many buyer-seller pairs as possible. This second method is selected to allow as many transactions to occur as possible per round. This buying and selling process continues iteratively until there are no buyers willing to pay what the sellers require or the trading results in back-and-forth cycling. At this point, zones with more energy units allocated than they need to remain at the peak of the utility curve are stripped of their extra units. After this process is finished, any additionally available energy units are allocated in an identical manner to the original allocation scheme, first according to utility and then disbursed evenly to give room for increased demand. In the absence of concerns as to the expediency of the processing of the data and data transmission requirements, the building-level server could perform a global optimization of the same form as the zone managers for the entire building, constructing a global influence matrix for the entire building system. As the zones are considered entirely independent of one another, there are no coupling terms between the zones in the global influence matrix. The solution to this problem would be guaranteed to yield a globally optimal solution unlike with the greedy solution.