Patent Application
20210140671
The present disclosure relates to aspects of using body shape information alone or in combination with other information to infer and improve occupant thermal comfort.
Thermal comfort is an important factor in building control. It drives the operation of heating, ventilation, and air conditioning (HVAC) systems, which are estimated to account for 50% of the total energy use in the built environment. Moreover, thermal comfort has a significant effect on the physiological and psychological wellbeing of an individual and affects occupants' health, satisfaction, and performance (Tom Y. Chang and Agne Kajackaite. 2019. Battle for the thermostat: Gender and the effect of temperature on cognitive performance. Plos One 14, 5 (2019); and William J Fisk. 2002. How IEQ affects health, productivity. ASHRAE journal 44 (2002)). Studies have shown that it can lead to either an increase in concentration and productivity in optimal comfort conditions or to lethargy and distraction in poor comfort conditions (Weilin Cui, Guoguang Cao, Jung Ho Park, Qin Ouyang, and Yingxin Zhu. 2013. Influence of indoor air temperature on human thermal comfort, motivation and performance. Building and Environment 68 (2013), 114-122; and Monika Frontczak and Pawel Wargocki. 2011. Literature survey on how different factors influence human comfort in indoor environments. Building and Environment 46, 4 (2011), 922-937).
Many commercial building control systems in use are based on models that regulate thermal conditions, often by means of pre-defined rules with pre-defined set-points, i.e., the goal temperature in an indoor environment. Temperature set-points are either derived from well-established standards, such as ASHRAE 55 (American Society of Heating Refrigerating and Air-Conditioning Engineers. Standards Committee. 2013. Thermal environmental conditions for human occupancy. ASHRAE standard; 55-2013 2013, STANDARD 55 (2013), 1-44), or require continuous feedback from occupants by means of surveys or wearables. Few building control systems prioritize the occupants' inherent physical characteristics, e.g., body shape information (height, weight, shoulder circumference), when making these thermal comfort estimates.
The sophistication of non-invasive sensing and privacy preserving occupancy-tracking systems has improved greatly in the last decade, making occupant tracking and occupant parameter estimation more ubiquitous (Nacer Khalil, Driss Benhaddou, Omprakash Gnawali, and Jaspal Subhlok. 2017. Sonicdoor: scaling person identification with ultrasonic sensors by novel modeling of shape, behavior and walking patterns. (2017), 3; and S. Munir, R. S. Arora, C. Hesling, J. Li, J. Francis, C. Shelton, C. Martin, A. Rowe, and M. Berges. 2017. Real-Time Fine Grained Occupancy Estimation Using Depth Sensors on ARM Embedded Platforms. In 2017 IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). 295-306). Thermal comfort prediction, on the other hand, remains a fundamental challenge in this domain, due to the stochasticity of the environment, the non-stationarity of human thermal comfort preferences, and the prohibitive cost of performing large-scale thermal comfort data-collection.
Thermal comfort has a considerable influence on the overall satisfaction in indoor environments (Weilin Cui, Guoguang Cao, Jung Ho Park, Qin Ouyang, and Yingxin Zhu. 2013. Influence of indoor air temperature on human thermal comfort, motivation and performance. Building and Environment 68 (2013), 114-122; and Monika Frontczak and Pawel Wargocki. 2011. Literature survey on how different factors influence human comfort in indoor environments. Building and Environment 46, 4 (2011), 922-937). Many building control systems rely on generic thermal comfort models for temperature regulation that average the air temperature to achieve thermal comfort among building occupants. The most widely used models are the Predicted Mean Vote model (PMV) (Poul O. Fanger. 1967. Calculation of thermal comfort, Introduction of a basic comfort equation. ASHRAE transactions 73, 2 (1967), 111-4), the Pierce Two-Node Model (PTNM) (Adolf P. Gagge. 1971. An effective temperature scale based on a simple model of human physiological regulatory response. Ashrae Trans. 77 (1971), 247-262), and the RP-884 model (Richard J. de Dear, Gail Schiller Brager, James Reardon, Fergus Nicol, et al. 1998. Developing an adaptive model of thermal comfort and preference/discussion. ASHRAE transactions 104 (1998), 145). The PMV and the PTNM models were introduced in the 1970s; the basis of both models are laboratory studies that take physiological parameters as well as environmental data into account (Poul O. Fanger. 1967. Calculation of thermal comfort, Introduction of a basic comfort equation. ASHRAE transactions 73, 2 (1967), 111-4; Adolf P. Gagge. 1971. An effective temperature scale based on a simple model of human physiological regulatory response. Ashrae Trans. 77 (1971), 247-262). This data includes air temperature, mean radiant temperature, relative humidity, and air velocity, and, as for human factors, clothing insulation and metabolic rate. All three mentioned models consider human factors, rather than using specific set-points, but they average the individual occupants' responses.
Recent literature employs machine learning in order to contextualize environmental data by means of supervised comfort modeling (L. Barrios and W. Kleiminger. 2017. The Comfstat-automatically sensing thermal comfort for smart thermostats. In 2017 IEEE International Conference on Pervasive Computing and Communications (PerCom). 257-266; Weilin Cui, Guoguang Cao, Jung Ho Park, Qin Ouyang, and Yingxin Zhu. 2013. Influence of indoor air temperature on human thermal comfort, motivation and performance. Building and Environment 68 (2013), 114-122). In a study with 38 participants, Kim et al. (Joyce Kim, Stefano Schiavon, and Gail Brager. 2018. Personal comfort models—A new paradigm in thermal comfort for occupant-centric environmental control. Building and Environment 132 (2018), 114-124) show that personalized thermal comfort models perform better than conventional models, such as the PMV, due to the increased model representational capacity. The evaluation in (L. Barrios and W. Kleiminger. 2017. The Comfstat—automatically sensing thermal comfort for smart thermostats. In 2017 IEEE International Conference on Pervasive Computing and Communications (PerCom). 257-266) assesses whether or not thermal comfort can be determined by sensor data and environmental variables, and the authors show promising results in personalized models, with an average of 83% across their 7 participants. Their results are compared against an always-comfortable model as well as a linear regression model that only uses temperature as input. However, generalizability is hard to conclude given these cohort sizes, whose data may not capture the non-stationary properties of human comfort preference as well as ambient environmental phenomena (Diana Enescu. 2017. A review of thermal comfort models and indicators for indoor environments. Renewable and Sustainable Energy Reviews 79, Supplement C (2017), 1353-1379; Laura Klein, Jun Young Kwak, Geoffrey Kavulya, Farrokh Jazizadeh, Burcin Becerik-Gerber, Pradeep Varakantham, and Milind Tambe. 2012. Coordinating occupant behavior for building energy and comfort management using multiagent systems. Automation in Construction 22 (2012), 525-536; V. Putta, G. Zhu, D. Kim, J. Hu, and J. Braun. 2012. A Distributed Approach to Efficient Model Predictive Control of Building HVAC Systems. International High Performance Buildings Conference (2012)). Moreover, these approaches do not address the role of body shape information (e.g., height, weight, and shoulder circumference) in the thermal comfort predictions.
Similar attempts that promote personalized comfort models also include occupant feedback, human factors, and bio-signal data (e.g., heart rate, skin temperature, and galvanic skin response) (Parisa Mansourifard, Farrokh Jazizadeh, Bhaskar Krishnamachari, and Burcin Becerik-Gerber. 2013. Online learning for personalized room-level thermal control: A multi-armed bandit framework. In Proceedings of the 5th ACM Workshop on Embedded Systems For Energy-Efficient Buildings. ACM, 1-8; Liang Zhang, Abraham Hang-yat Lam, and Dan Wang. 2014. Strategy-proof thermal comfort voting in buildings. In Proceedings of the 1st ACM Conference on Embedded Systems for Energy-Efficient Buildings. ACM, 160-163). Another approach proposes to use body features that are identified through video and shows that the human thermoregulation state can be inferred from the human skin (Farrokh Jazizadeh and S Pradeep. 2016. Can computers visually quantify human thermal comfort?: Short paper. In Proceedings of the 3rd ACM International Conference on Systems for Energy-Efficient Built Environments. ACM, 95-98). On a similar basis, the FORK system uses a depth sensor to detect, track, and estimate occupancy in buildings (S. Munir, R. S. Arora, C. Hesling, J. Li, J. Francis, C. Shelton, C. Martin, A. Rowe, and M. Berges. 2017. Real-Time Fine Grained Occupancy Estimation Using Depth Sensors on ARM Embedded Platforms. In 2017 IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). 295-306).
Other approaches, such as SPOT (Peter Xiang Gao and Srinivasan Keshav. 2013. SPOT: a smart personalized office thermal control system. In Proceedings of the fourth international conference on Future energy systems. ACM, 237-246) and SPOT+(Peter Xiang Gao and Srinivasan Keshav. 2013. Optimal personal comfort management using SPOT+. In Proceedings of the 5th ACM Workshop on Embedded Systems For Energy-Efficient Buildings. ACM, 1-8), describe occupancy sensing systems for thermal control; as a result, the goal of these works is to generate a zone temperature set-point, as opposed to comfort predictions. SPOT uses the Predicted Personal Vote (PPV) model, which takes Fanger's PMV (Poul O. Fanger. 1967. Calculation of thermal comfort, Introduction of a basic comfort equation. ASHRAE transactions 73, 2 (1967), III-4) and adds a linear function to include the individual's sensitivity to the variables used by the PMV. Gao and Keshav (Peter Xiang Gao and Srinivasan Keshav. 2013. Optimal personal comfort management using SPOT+. In Proceedings of the 5th ACM Workshop on Embedded Systems For Energy-Efficient Buildings. ACM, 1-8) show reductions in user discomfort, from 0.36 to 0.02, as compared to baselines.
According to one or more illustrative examples, a method for inferring and improving occupant thermal comfort accounting for body shape information includes obtaining height, weight, and shoulder circumference of an occupant of a room using a depth sensor; utilizing a model trained on a dataset including information reflecting of occupant comfort within the room versus temperature, the model receiving, as inputs, the height, the weight, and the shoulder circumference of the occupant and environmental information and outputting a comfort class; identifying a temperature set-point for which the room occupant is identified by the model as having the comfort class being indicative of user comfort; and adjusting HVAC controls for the room to the identified temperature set-point.
According to one or more illustrative examples, a system for inferring and improving occupant thermal comfort accounting for body shape information includes a memory storing instructions; and a processor. The processor is programmed to execute the instructions to perform operations including to, responsive to detecting an occupant entering a room, obtain height, weight, and shoulder circumference of the occupant of the room using a depth sensor mounted to a ceiling of the room; utilize a model trained on a dataset including information reflecting of occupant comfort within the room versus temperature, the model receiving, as inputs, the height, the weight, and the shoulder circumference of the occupant and environmental information and outputting a comfort class; identify a temperature set-point for which the room occupant is identified by the model as having the comfort class being indicative of user comfort; and adjust HVAC controls for the room to the identified temperature set-point.
According to one or more illustrative examples, a non-transitory computer-readable medium includes instructions for inferring and improving occupant thermal comfort accounting for body shape information that, when executed by a processor, cause the processor to, responsive to detecting an occupant entering a room, obtain height, weight, and shoulder circumference of the occupant of the room using a depth sensor mounted to a ceiling of the room; utilize a model trained on a dataset including information reflecting of occupant comfort within the room versus temperature, the model receiving, as inputs, the height, the weight, and the shoulder circumference of the occupant and environmental information and outputting a comfort class; identify a temperature set-point for which the room occupant is identified by the model as having the comfort class being indicative of user comfort; and adjust HVAC controls for the room to the identified temperature set-point.
Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
Thermal comfort is a decisive factor for the well-being, productivity, and overall satisfaction of commercial building occupants. Many commercial building automation systems either use a fixed zone-wide temperature set-point for all occupants or they rely on extensive sensor deployments with frequent online interaction with occupants. This results in inadequate comfort levels or significant training effort from users, respectively. However, the increasing ubiquity of cheap, depth-based occupancy tracking systems has enabled an improvement in inferential capabilities.
Human physiology implies that body shape does play an important part in thermal comfort. An individual with a larger body surface offers a larger area for sensing the temperature outside the body. Additionally, adipose tissue has the effect of trapping heat, meaning that the human core stays warm while the body surface, i.e., the skin, cools down
This disclosure describes an improved system that may be used for predicting thermal comfort preferences of occupants by leveraging their body shape information. The disclosed approach improves the accuracy of thermal comfort predictions, alleviates the need for frequent occupant comfort feedback during system deployment, and leverages data from existing commercial building sensing infrastructures. Based on a human study experiment where data was collected from human participants, a model was developed to infer thermal comfort of individuals using body shape information. This is a novel and nonobvious approach to infer thermal comfort of individuals. Moreover, in order to emphasize the increased inferential power that body shape information offers to comfort modeling, the model may be compared with other instances of the same hyperparameter configuration that are trained only on an ablated set of feature inputs. Based on the comparison with model baselines and ablations, the described approach infers thermal comfort of individuals with greater accuracy when body shape information is taken into account. The model may also be configured for temperature set-point prediction, showing that the described strategy performs proximally to state-of-the-art techniques.
In this disclosure, the FORK system is extended to include physiological body shape information in order to infer the individual's thermal comfort preferences. When an occupant enters a room, their height, weight, and shoulder circumference are obtained using a depth-based occupancy tracking assembly, based on FORK (S. Munir, R. S. Arora, C. Hesling, J. Li, J. Francis, C. Shelton, C. Martin, A. Rowe, and M. Berges. 2017. Real-Time Fine Grained Occupancy Estimation Using Depth Sensors on ARM Embedded Platforms. In 2017 IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). 295-306). This body shape information may be combined with environmental sensor data from the commercial Building Automation and Control Network (BACNet) infrastructure on our campus. The occupant's thermal comfort preference may be classified, conditioned on the body shape information and the environmental factors. Using the set of comfort predictions, an optimal zone temperature set-point range may be inferred.
Regarding performing body shape inference, the Fine-grained Occupancy estimatoR using Kinect (FORK) system (S. Munir, R. S. Arora, C. Hesling, J. Li, J. Francis, C. Shelton, C. Martin, A. Rowe, and M. Berges. 2017. Real-Time Fine Grained Occupancy Estimation Using Depth Sensors on ARM Embedded Platforms. In 2017 IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). 295-306) uses a ceiling-mounted depth sensor to estimate the number of occupants in a room. To identify and track humans in the sensor's field-of-view, FORK uses a model-based approach which relies on the anthropometric properties of human heads and shoulders. The human detection algorithm of FORK may be used to determine body shape information in the disclosed approach. One reason to utilize a depth sensor for estimating body shape (as opposed to an RGB camera, for example) is that the depth sensor is considerably less privacy-invasive: a depth sensor cannot sense skin color, hair, cloth, and—since it is mounted overhead—it cannot see facial features. Hence, it is difficult to identify individuals using depth frames, even if the sensor is compromised. The disclosed approach may perform the computation at the edge and accordingly may operate without the upload of image data to a remote server. In one example, the disclosed approaches uses the Microsoft Kinect V2, which provides depth frames at a 512×424 resolution.
With respect to determining height, responsive to FORK detecting a human head, it fits a contour and a minimum enclosing circle around the head, as shown in the sample depth frame (a). Among all the pixels within the circle, the system locates a pixel Pmin=(px, py) that has the minimum depth value Dmin. Note that, since a depth sensor provides distance to its nearest object in millimeters, Pmin is the pixel representing the highest point on the head of the person. In order to estimate the participant's height, the system estimates floor height Fmax by building a histogram of number of depth pixels at different distances from the sensor, as in FORK. The bin with the highest number of pixels is considered the floor. The height of the person is then computed as Fmax−Dmin. Since a person is captured in multiple frames while he or she enters and exits, the height may be estimated when the person is directly underneath the sensor, such that height estimations at the edges of the frame may be ignored.
Given that the end-to-end distance between two shoulders of a person is approximately three times the diameter of head, the system fits a region-of-interest (ROI) that includes the head and shoulder and discards all pixels below a threshold Dmin+H+S, in order to discard depth values below the shoulder level. An example is shown in
The circumference of the ellipse is used to estimate the circumference of the shoulder. Note that the circumference of the ellipse is in the pixel coordinate. In order to map it to real-world shoulder circumference, the system builds a linear-regression model, using elliptical circumference as predictor to fit the training data. However, this approach may suffer when the two shoulders are separated or when one shoulder gets occluded.
In this fully-controlled thermal chamber, individual comfort experiments were performed to generate a dataset than enables comprehensive study of human thermal comfort preferences, in a commercial building environment, across a wide range of indoor environmental conditions. Each comfort experiment lasted for 3.5 hours and began by manually measuring the participant's ground-truth body shape information. In one example, each participant may be asked to pace in and out of the room, beneath the depth camera, to obtain accurate body shape predictions.
The participant completed a thermal comfort survey every five minutes or whenever they initiated a change in their clothing level (e.g., adding or removing a sweater) or activity type. Participants provided their comfort votes on the basis of a reduced 5-point ASHRAE 55 scale (American Society of Heating Refrigerating and Air-Conditioning Engineers. Standards Committee. 2013. Thermal environmental conditions for human occupancy. ASHRAE standard; 55-2013 2013, STANDARD 55 (2013), 1-44), see Table 1, which is used in order to reduce the complexity of voting.
The use of seven-point scales generally improves reliability, however, in a setting where participants are polled in a frequent interval, less steps to perform the task increases the efficacy of the responses (Emin Babakus and W Glynn Mangold. 1992. Adapting the SERVQUAL scale to hospital services: an empirical investigation. Health services research 26, 6 (1992); Sheetal B Sachdev and Harsh V Verma. 2004. Relative importance of service quality dimensions: A multisectoral study. Journal of services research 4, 1 (2004)). In the instant example study, a main objective was to determine the participant's thermal comfort, which is, according to ASHRAE, mapped to “warmer”, “cooler”, or “no change”. However, it may also be useful to identify whether the participant felt “uncomfortably” or “slightly” warm or cold, as this gives important meta-information for the relevance of a change in temperature for the specific individual. This scale can be mapped to ASHRAE's thermal comfort scale as follows: “slightly uncomfortably cold” and “uncomfortably cold” to “warmer”, “comfortable” to “no change”, and “slightly uncomfortably warm” and “uncomfortably warm” to “cooler”. The ASHRAE's thermal sensation scale is not included here, as it merely indicates the subject's current sensation, but not comfort, which is a more important factor in this case. The thermal comfort index information is summarized in Table 1.
In addition, human subject population statistics are summarized in Table 2. While not shown in the Table 2, self-reported participant Gender was obtained as an additional feature: 34 males and 43 females.
During each experiment, zone air temperature is sampled (e.g., in 30-second intervals), while set point temperature and air flow rate are sampled upon change. Additionally, outside temperature and relative humidity (e.g., with 60-second granularity) are captured from a nearest weather station (in the given example located a quarter mile (half-kilometer) from the experiment location).
Dataset curation may be performed on the collected data. In an example, the collected data may include the following feature groups: biometrics sensor data (band), body shape information (body), subjective comfort data from the mobile device application (survey), environmental sensor data from the HVAC system (HVAC), and outdoor weather station data (weather). The dataset modalities themselves are summarized in Table 3. In Table 3, the samples from band, HVAC, and weather data are aligned to the nearest comfort labels specified by the survey data. The band values may be observed to exhibit little volatility in the space of 1 minute, which for the instant example is the sampling rate of the wearable device and also the maximum temporal difference between survey and band sample timestamps.
Datasets may be generated for evaluation, based on feature subsets of the full data. This may allow for comparison of ablations of the thermal comfort models that are trained with and without, e.g., body shape information, biometrics features, or external weather information. As shown in Table 3, there are five data subsets. Featureset-1 (FS1) includes environmental sensor information, occupant physical characteristics, occupant biometrics, and mobile app survey information. FS2 includes all the feature from FS1, except the body shape information. FS3 includes environmental sensor information and occupant physical characteristics. FS4 includes only environmental sensor information. FS5 includes only zone temperature information.
As shown, FS1 includes 9 features. Although other features were collected, such as activity and galvanic skin response (GSR), participants did not report many different classes for the former feature. Many selected ‘OTHER’ and proceeded to describe their activities in their own words. For the latter, after fitting a linear regression model with all the features, it was identified that GSR contributed the least when compared to the remaining features. Using Featureset-2 (FS2), the effect of omitting body shape characteristics from trained models was examined, through direct comparison with FS1. Featureset-3 (FS3) consisted of a more limited set of features. The inferential value of just these modalities was tested here, since the first two are easily obtained from BACNet and local weather stations, respectively (see Table 3), and the last three are easily regressed or inferred from depth-camera sensor data (S. Munir, R. S. Arora, C. Hesling, J. Li, J. Francis, C. Shelton, C. Martin, A. Rowe, and M. Berges. 2017. Real-Time Fine Grained Occupancy Estimation Using Depth Sensors on ARM Embedded Platforms. In 2017 IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). 295-306). Featureset-4 (FS4) tests the inferential value of environmental features alone. Finally, Featureset-5 (FS5) only considers zone temperature and serves as a baseline featureset for which only a room thermostat is needed. Additionally, some participants exhibit missing skin temperature measurements due to faulty connections between the wearable device and the mobile application. To address this, the missing measurements were augmented by implementing the heuristic SkinTemp=RoomTemp+k where k was drawn from a normal distribution with mean and standard deviation calculated, using the heuristic, on the instances where skin temperature was successfully recorded. The previous tables do not consider these new value in their calculations.
Thermal comfort modeling may be performed using the collected and curated data. The thermal comfort modeling task may be posed as a supervised multiclass classification problem, wherein the model estimates the likelihood of having accurately predicted a specific comfort label for an occupant, C=y, conditioned on some context. With the “full” data featureset FS1 (e.g., as shown in Table 3), the context of the model involves Band (B a), Body (Bo), Survey (S), HVAC (H), and Weather (W) data as shown in equation (1):
P(Ct=y|Ba,Bo,S,H,W) (1)
where,
y∈{−2, −1, 0, 1, 2}
Thus, a training objective is to minimize the aggregate negative log-likelihood of these predictions, over an arbitrary time horizon, with respect to the corresponding ground-truth comfort labels (as shown in Equation 2):
min Σ−log(P(Ct=y|Ba,Bo,S,H,W)) (2)
In machine learning literature, this formulation is also referred to as cross-entropy.
For the model architectural class, a multi-layer perceptron (MLP) may be utilized, as this may be used to flexibly represent and map diverse multimodal input distributions, as discussed in thermal comfort literature (Diana Enescu. 2017. A review of thermal comfort models and indicators for indoor environments. Renewable and Sustainable Energy Reviews 79, Supplement C (2017), 1353-1379; Soteris A. Kalogirou. 2000. Applications of artificial neural-networks for energy systems. Applied Energy 67, 1 (2000), 17-35; Joyce Kim, Stefano Schiavon, and Gail Brager. 2018. Personal comfort models—A new paradigm in thermal comfort for occupant-centric environmental control. Building and Environment 132 (2018), 114-124; and Joyce Kim, Yuxun Zhou, Stefano Schiavon, Paul Raftery, and Gail Brager. 2018. Personal comfort models: predicting individuals' thermal preference using occupant heating and cooling behavior and machine learning. Building and Environment 129 (2018), 96-106). At each timestep, the model makes a comfort prediction as a distribution over all the comfort class labels (e.g., as shown in Table 1 b.3). (Notably, time-recurrent neural encoding structures (e.g., LSTMs, GRUs) lend themselves well to these sequential data inputs and may be placed in front of the MLP classifier. However, recurrent models have significantly higher training complexity and may provide best results after using various data-augmentation techniques, e.g., weakly-supervised generative modeling.) The label with the largest probability mass may be selected as the predicted occupant's comfort label, given the input context. An example model configuration includes 4 hidden layers (in, 250, 100, 25, 5, out), tan h activations, an adaptive learning rate with an initialization of 1e-3, batch size of 5, one-hot label-vector representations, Adaptive moment estimation (Adam) as the optimization function (Diederik P Kingma and Jimmy Lei Ba. 2015. Adam: A Method for Stochastic Optimization. International Conference on Learning Representations (ICLR) 2015 (2015)), and an 80%/20% dataset split with 10-fold cross-validation in the training split.
Temperature set-point generation may be performed using the system. The thermal comfort model takes as input body shape and environmental information and outputs comfort class labels in the set −2, −1, 0, 1, 2. From these labels, a zone temperature set-point may be inferred that maximizes the number of participants in the dataset test split that would report “0” or Comfortable as their subjective response. The test split stratified according to participant includes the subjective comfort responses (and associated environmental and body shape information) for the various participants. For each participant in the test set, a forward-pass through the trained comfort model is performed to infer participant comfort preferences. This yields a distribution over zone temperatures, conditioned on comfort label, from which the temperature range is extracted that maximized the number of “0” votes across the test set. These resultant temperature set-points may be compared with set-points generated by baseline control strategies.
A paired dataset of comfort profiles and physical characteristics may be generated from the participants in a commercial building environment. Using this data, an evaluation of common modeling strategies (Diana Enescu. 2017. A review of thermal comfort models and indicators for indoor environments. Renewable and Sustainable Energy Reviews 79, Supplement C (2017), 1353-1379; and Soteris A. Kalogirou. 2000. Applications of artificial neural-networks for energy systems. Applied Energy 67, 1 (2000), 17-35) for empirical thermal comfort prediction may be performed. Additionally, it may be observed how powerful physical characteristics are for estimating the thermal comfort preferences of occupants. The models may be compared to baselines and ablations.
Regarding body shape inference performance, the performance of the system 100 in terms of its ability to estimate human height and shoulder circumference may be identified. This performance may include height estimation performance, and shoulder circumference estimation performance.
With respect to height estimation performance, Table 4 shows the performance of the system for estimating human height: the average and median error is 3.28 cm and 3.0 cm, respectively, when someone is entering. The average and median error is respectively 2.99 cm and 2.55 cm, when a person is exiting. Considering the mean and median height of our subjects are 171.25 cm and 171 cm, respectively, the height estimation as shown has an accuracy of 98%.
With respect to shoulder circumference estimation performance, Table 4 also shows the system performance for estimating human shoulder circumference. 40% of the data may be used to fit the linear regression model and the remaining 60% may be used as test data. (However, these are only examples and different data splits may be used.) The average and median errors for a person entering is 9.96 cm and 8.19 cm; the average and median errors for a person exiting is 10.03 cm and 9.82 cm. Considering the mean and median shoulder circumference of the participants are 109.44 cm and 107.15 cm, respectively, this shoulder circumference estimation is over 90% accurate.
Thermal comfort modeling performance may also be estimated. The system may be evaluated in terms of its thermal comfort inference capability. To remain grounded in the related literature (Diana Enescu. 2017. A review of thermal comfort models and indicators for indoor environments. Renewable and Sustainable Energy Reviews 79, Supplement C (2017), 1353-1379; Ali Ghahramani, Chao Tang, and Burcin Becerik-Gerber. 2015. An online learning approach for quantifying personalized thermal comfort via adaptive stochastic modeling. Building and Environment 92 (2015), 86-96; Joyce Kim, Stefano Schiavon, and Gail Brager. 2018. Personal comfort models—A new paradigm in thermal comfort for occupant-centric environmental control. Building and Environment 132 (2018), 114-124; and Joyce Kim, Yuxun Zhou, Stefano Schiavon, Paul Raftery, and Gail Brager. 2018. Personal comfort models: predicting individuals' thermal preference using occupant heating and cooling behavior and machine learning. Building and Environment 129 (2018), 96-106), the model may be evaluated across three dimensions: (i) holistic versus personalized comfort models; (ii) binary versus multi-class classification; and (iii) model ablations using different modality subsets. Throughout each of these experiments, the evaluative datasets that are generated from our human comfort experiment may be considered. For instance, with reference to Table 3, these may include: FS1 (all features), FS2 (all features, minus body shape information), FS3 (environmental features and body shape information), FS4 (environmental features only), and FS5 (zone temperature only). The effect of specific feature groups, e.g., body shape information, for providing models with improved inferential capability may also be considered.
Regarding baselines, the datasets FS1-FS5 may be used to compare the model configuration with discriminative classifiers, such as Random Decision Forest (RDF) and Support Vector Machines (SVM). Other classifiers may be included, such as the non-parametric K-Nearest Neighbors (k-NN) classifier, the naive Bayes (NB) classifier, the predicted personal vote (PPV) model proposed by (Peter Xiang Gao and S. Keshav. 2013. SPOT: A Smart Personalized Office Thermal Control System. In Proceedings of the Fourth International Conference on Future Energy Systems (e-Energy '13). ACM, New York, N.Y., USA, 237-246), and the predicted mean vote (PMV) model (Poul O. Fanger. 1967. Calculation of thermal comfort, Introduction of a basic comfort equation. ASHRAE transactions 73, 2 (1967), 111-4), which remains the baseline for comfort-aware commercial building control (American Society of Heating Refrigerating and Air-Conditioning Engineers. Standards Committee. 2013. Thermal environmental conditions for human occupancy. ASHRAE standard; 55-2013 2013, STANDARD 55 (2013), 1-44.). For all classifier baselines, a hyperparameter grid search may be performed with respect to the training set, with choice of parameters for each baseline as those of the model that performed with the highest average 10-fold cross-validation f1-micro score.
Models may be holistic models or personalized models. Models that are trained on the entire population's thermal comfort data may be referred to as holistic comfort models. Models trained only on individual participants' thermal comfort data may be referred to as personalized models.
Using a holistic model, the comfort responses of one participant are not distinguished from the responses of another participant. Instead, the models may be stratified across all participant data within the train and validation split, such that samples from the same participant may not exist across the train and validation split. This holistic model configuration illustrates a crowd-level thermal comfort prediction strategy, where individual biases are disregarded and optimization is instead performed across the entire population.
Through this evaluation, it may be observed how the same model performs differently for each participant. In particular, it can be seen that the tiles can completely change their color over the horizontal axis. However, even as the number of features used (Y-axis) is increased, the performance for each subset is generally consistent. This implies that the same personalized model configuration is able to capture each participant's unique set of preferences. Moreover, it can be seen that the highest performance achieved in the holistic approach is surpassed by around 20% of the participants that use the same model in a personalized fashion. This seems consistent with the results obtained by, e.g., Barrios and Kleiminger (L. Barrios and W. Kleiminger. 2017. The Comfstat-automatically sensing thermal comfort for smart thermostats. In 2017 IEEE International Conference on Pervasive Computing and Communications (PerCom). 257-266.) who were able to achieve similar performance for their personalized models on a smaller cohort.
Regarding binary vs. multi-class classifiers, in order to provide binary classifiers for baseline comparison, map the target labels may be re-mapped in each featureset from the 5-class categorical distribution to a binary one, with the label “0” representing Comfortable and any label in {−2, −1, 1, 1} representing “1” or Uncomfortable.
Regarding ablations, a model ablation experiment may be performed by first generating several instances of the comfort model, then feeding each instance with a unique featureset (Table 3), during training and evaluation. From
Optimal temperature set-points may be found using the aforementioned predictive capabilities. In order to validate the system accuracy in temperature set-point prediction, the comfort prediction capability of the system may be compared with other common fixed temperature control strategies used in practice and in existing literature. These strategies include a fixed temperature set-point range that mimics the current control strategy commercial buildings use, a fixed temperature set-point baseline used in (Alimohammad Rabbani and S. Keshav. 2016. The SPOT* Personal Thermal Comfort System. In Proceedings of the 3rd ACM International Conference on Systems for Energy-Efficient Built Environments (BuildSys '16). ACM, New York, N.Y., USA, 75-84) and (Peter Xiang Gao and S. Keshav. 2013. Optimal Personal Comfort Management Using SPOT+. In Proceedings of the 5th ACM Workshop on Embedded Systems For Energy-Efficient Buildings (BuildSys '13). ACM, New York, N.Y., USA, Article 22, 8 pages), a reactive set-point model PPV from (Peter Xiang Gao and S. Keshav. 2013. SPOT: A Smart Personalized Office Thermal Control System. In Proceedings of the Fourth International Conference on Future Energy Systems (e-Energy '13). ACM, New York, N.Y., USA, 237-246), and two fixed temperature models based on the mean and median temperatures of the validation split. For these baselines, models such as OccuTherm and PPV that require parameter tuning based on existent data may be trained on a 40/60 train-validation split based on the number of participants for both FS1 and FS3. In order to create a range of temperature that each model perceives as a range where comfortable labels are always produced, the fixed set-point models were treated as their set-point ±2° F., whereas in the other models this range was obtained from the training split. The PPV used the mininum and maximum temperature at which the training samples predicted [−0.5, 0.5]. On the other hand, the system comfortable temperature range was calculated from the temperatures at which the ‘Comfortable’ label was 0. For each model it was calculated the RMSE across the participants' responses in the validation split. Only responses at which the indoor temperature was within the model's ‘Comfortable’ temperature range were used as shown in equation (3):
The equation above shows the respective calculation where the ‘predicted’ label is treated as 0 for all models since it is only considering instances in their respective ‘Comfortable’ temperature range. y is the ground truth label from the participant. These results, in terms of RMSE, are summarized in Table 5:
Here, it can be seen that, when using a feature set that include body shape information, such as FS1 and FS3, MLP, RDF, and KNN are able to surpass existing control strategies by 0.26 and 0.18, in FS1 and FS3, respectively.
Though the sample size of a human subject study used in the modeling (77 participants) is significantly larger than many other thermal comfort studies in the literature, it is nevertheless small for making claims about the population (e.g., commercial building occupants in the US). Despite this, these results indicate that the system can estimate body shape information with high accuracy and, more importantly, can leverage this information to significantly improve thermal comfort preference predictions when compared to baselines and feature ablations. Though this improvement may seem modest, it is worth noting that the system works without the need for frequent user comfort feedback reports and that it leverages data from depth-imaging sensors, which are quickly becoming commonplace in indoor environments. Furthermore, this is the first demonstration of the predictive power of body shape information for inferring thermal comfort.
The system uses a 5-point comfort scale, rather than the 3-point comfort and 7-point sensation scale proposed by Fanger (American Society of Heating Refrigerating and Air-Conditioning Engineers. Standards Committee. 2013. Thermal environmental conditions for human occupancy. ASHRAE standard; 55-2013 2013, STANDARD 55 (2013), 1-44; and Poul O. Fanger. 1967. Calculation of thermal comfort, Introduction of a basic comfort equation. ASHRAE transactions 73, 2 (1967), 111-4). Though a systematic analysis of this decision is outside of the scope of this disclosure, it should be noted that there is a robust literature dating back several decades regarding the trade-offs made when using any particular scale, due to numerous issues including effects on participant's behavior and responses, ability to differentiate results, etc. Ultimately, the number of choices presented to study participants (which resembles issues in discrete-choice experiments) should be chosen wisely and could be studied with more care in future work. Finally, the train-validation split by participant had an impact on the model's performance. When a complete stratification of the dataset was done first and then split into train and validation, the system k-NN was able to achieve 79% and 72% accuracy in the binary and multi-class approach. However, this approach allows the co-existence of samples from the same participant in both splits, exposing the model to a portion of the participant's responses distribution; such a setting could be preferable for re-occurring participants. Thus, it was opted for the split based on participants.
In this disclosure a scale was used in order to measure weight of the subjects, which was used as a feature to infer thermal comfort; in the future, a model can be built using body shape to regress weights of individuals. Clothing insulation was also noted in the dataset: in the future, depth frames can be directly used to infer level of clothing insulation. Note that inaccuracies in the estimation of shoulder circumference could affect the performance of thermal comfort inference. People may carry objects, e.g., backpacks, laptops, helmets hanging in the shoulder that could affect the estimation of shoulder circumference. It may require detection of such objects as in (Niluthpol Chowdhury Mithun, Sirajum Munir, Karen Guo, and Charles Shelton. 2018. ODDS: real-time object detection using depth sensors on embedded GPUs. In Proceedings of the 17th ACM/IEEE International Conference on Information Processing in Sensor Networks. IEEE Press, 230-241) and refine the shoulder estimate.
The size of the participant group may not be large enough to capture all possible factors (e.g., social, environmental) that could impact the thermal comfort preference of individuals and the resultant commercial building control strategies (J. Francis, A. Oltramari, S. Munir, C. Shelton, and A. Rowe. 2017. Poster Abstract: Context Intelligence in Pervasive Environments. In 2017 IEEE/ACM Second International Conference on Internet-of-Things Design and Implementation (IoTDI). 315-316; and Z. Jiang, J. Francis, A. K. Sahu, S. Munir, C. Shelton, A. Rowe, and M. Bergés. 2018. Data-driven Thermal Model Inference with ARMAX, in Smart Environments, based on Normalized Mutual Information. In 2018 Annual American Control Conference (ACC). 4634-4639. https://doi.org/10.23919/ACC.2018.8431085). However, it has been shown that heat dissipation rate of individuals depends on the body surface area. As a result, a tall and skinny person can tolerate higher room temperature compared to a person having a rounded body shape since the tall person has a larger surface to volume ratio (S. V. Szokolay. 2008. Introduction to Architectural Science. Taylor & Francis). So, it is intuitive to assume that body shape can be useful to infer thermal comfort preference of individuals to some extent.
In conclusion, a novel thermal comfort prediction system is presented, based on occupant body shape information. A human thermal comfort study may be conducted in a fully-controlled and fully-sensed smart environment, where biometrics, physical measurements (height, shoulder circumference), and subjective comfort responses were recorded and integrated. With this dataset, holistic comfort models may be compared with personalized comfort models to show the significance of physical characteristics across a sample population for thermal comfort modeling. While holistic approaches can achieve f1-micro scores as high as 0.8, personalized models can surpass this value. Nevertheless, as shown in
The algorithms and/or methodologies of one or more embodiments are implemented using a computing platform, as shown in
The processor 1004 may be configured to read into memory 1002 and execute computer-executable instructions residing in software module 1008 of the non-volatile storage 1006 and embodying algorithms and/or methodologies of one or more embodiments. The software module 1008 may include operating systems and applications. The software module 1008 may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java, C, C++, C#, Objective C, Fortran, Pascal, Java Script, Python, Perl, and PL/SQL. In one embodiment, PyTorch, which is a package for the Python programming language, may be used to implement code for the machine learning model of one or more embodiments.
Upon execution by the processor 1004, the computer-executable instructions of the software module 1008 may cause the system 1000 to implement one or more of the algorithms and/or methodologies disclosed herein. The non-volatile storage 1006 may also include data 1010 supporting the functions, features, and processes of the one or more embodiments described herein.
At operation 1102, the system 1100 obtains information regarding an occupant of a room. For instance, responsive to detecting the occupant entered the room, the system 1100 obtains the height, weight, and shoulder circumference of the occupant using a depth sensor mounted to a ceiling of the room.
At operation 1104, the system 1100 models a comfort class for the occupant. For instance, the system 100 utilizes a model trained on a dataset including information reflecting of occupant comfort within the room versus temperature, the model receiving, as inputs, the height, the weight, and the shoulder circumference of the occupant and environmental information and outputting the comfort class.
At operation 1106, the system 1100 identifies a temperature set-point. For instance, the system 1100 identifies the temperature set-point for which the room occupant is identified by the model as having a comfort class indicative of user comfort.
At operation 1108, the system 1100 adjusts room HVAC settings. For instance, the system 1100 adjusts the HVAC controls for the room to the identified temperature set-point. After operation 1108, the process 1100 ends.
The program code embodying the algorithms and/or methodologies described herein is capable of being individually or collectively distributed as a program product in a variety of different forms. The program code may be distributed using a computer readable storage medium having computer readable program instructions thereon for causing a processor to carry out aspects of one or more embodiments. Computer readable storage media, which is inherently non-transitory, may include volatile and non-volatile, and removable and non-removable tangible media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. Computer readable storage media may further include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other solid state memory technology, portable compact disc read-only memory (CD-ROM), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and which can be read by a computer. Computer readable program instructions may be downloaded to a computer, another type of programmable data processing apparatus, or another device from a computer readable storage medium or to an external computer or external storage device via a network.
Computer readable program instructions stored in a computer readable medium may be used to direct a computer, other types of programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions that implement the functions, acts, and/or operations specified in the flowcharts or diagrams. In certain alternative embodiments, the functions, acts, and/or operations specified in the flowcharts and diagrams may be re-ordered, processed serially, and/or processed concurrently consistent with one or more embodiments. Moreover, any of the flowcharts and/or diagrams may include more or fewer nodes or blocks than those illustrated consistent with one or more embodiments.
The processes, methods, or algorithms disclosed herein can be deliverable to/implemented by a processing device, controller, or computer, which can include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms can be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms can also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms can be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.
