Wearables are poised to transform health and wellness through automation of cost-effective, objective, and real-time health monitoring. However, machine learning models for these systems are designed based on labeled data collected, and feature representations engineered, in controlled environments. This approach has limited scalability of wearables because (i) collecting and labeling sufficiently large amounts of sensor data is a labor-intensive and expensive process; and (ii) wearables are deployed in highly dynamic environments of the end-users whose context undergoes consistent changes. We introduce TransNet , a deep learning framework that minimizes the costly process of data labeling, feature engineering, and algorithm retraining by constructing a scalable computational approach. TransNet learns general and reusable features in lower layers of the framework and quickly reconfigures the underlying models from a small number of labeled instances in a new domain, such as when the system is adopted by a new user or when a previously unseen event is to be added to event vocabulary of the system. Utilizing TransNet on four activity datasets, TransNet achieves an average accuracy of 88.1% in cross-subject learning scenarios using only one labeled instance for each activity class. This performance improves to an accuracy of 92.7% with five labeled instances.

Advances in embedded systems have enabled integration of many lightweight sensory devices within our daily life. In particular, this trend has given rise to continuous expansion of wearable sensors in a broad range of applications from health and fitness monitoring to social networking and military surveillance. Wearables leverage machine learning techniques to profile behavioral routine of their end-users through activity recognition algorithms. Current research assumes that such machine learning algorithms are trained offline. In reality, however, wearables demand continuous reconfiguration of their computational algorithms due to their highly dynamic operation. Developing a personalized and adaptive machine learning model requires real-time reconfiguration of the model. Due to stringent computation and memory constraints of these embedded sensors, the training/re-training of the computational algorithms need to be memory- and computation-efficient. In this paper, we propose a framework, based on the notion of online learning, for real-time and on-device machine learning training. We propose to transform the activity recognition problem from a multi-class classification problem to a hierarchical model of binary decisions using cascading online binary classifiers. Our results, based on Pegasos online learning, demonstrate that the proposed approach achieves 97% accuracy in detecting activities of varying intensities using a limited memory while power usages of the system is reduced by more than 40%.

Wearable sensors utilize machine learning algorithms to infer important events such as the behavioral routine and health status of their end users from time-series sensor data. A major obstacle in large-scale utilization of these systems is that the machine learning algorithms cannot be shared among users or reused in contexts different from the setting in which the training data are collected. As a result, the algorithms need to be retrained from scratch in new sensor contexts, such as when the on-body location of the wearable sensor changes or when the system is utilized by a new user. The retraining process places significant burden on end users and system designers to collect and label large amounts of training sensor data. In this article, we challenge the current algorithm training paradigm and introduce Share-n-Learn to automatically detect and learn physical sensor contexts from a repository of shared expert models without collecting any new labeled training data. Share-n-Learn enables system designers and end users to seamlessly share and reuse machine learning algorithms that are trained under different contexts and data collection settings. We develop algorithms to autonomously identify sensor contexts and propose a gating function to automatically activate the most accurate machine learning model among the set of shared expert models. We assess the performance of Share-n-Learn for activity recognition when a dynamic sensor constantly migrates from one body location to another. Our analysis based on real data collected with human subjects on three datasets demonstrates that Share-n-Learn achieves, on average, 68.4% accuracy in detecting physical activities with context-varying wearables. This accuracy performance is about 19% more than ‘majority voting,’ 10% more than the state-of-the-art transfer learning, and only 8% less than the experimental upper bound.

A major barrier to the personalized Human Activity Recognition using wearable sensors is that the performance of the recognition model drops significantly upon adoption of the system by new users or changes in physical/behavioral status of users. Therefore, the model needs to be retrained by collecting new labeled data in the new context. In this study, we develop a transfer learning framework using convolutional neural networks to build a personalized activity recognition model with minimal user supervision.

Wearable technologies play a central role in human-centered Internet-of-Things applications. Wearables leverage machine learning algorithms to detect events of interest such as physical activities and medical complications. A major obstacle in large-scale utilization of current wearables is that their computational algorithms need to be re-built from scratch upon any changes in the configuration. Retraining of these algorithms requires significant amount of labeled training data, a process that is labor-intensive and time-consuming. We propose an approach for automatic retraining of the machine learning algorithms in real-time without need for any labeled training data. We measure the inherent correlation between observations made by an old sensor view for which trained algorithms exist and the new sensor view for which an algorithm needs to be developed. Our multi-view learning approach can be used in both online and batch modes. By applying the autonomous multi-view learning in the batch mode, we achieve an accuracy of 83.7 percent in activity recognition which is an improvement of 9.3 percent due to the automatic labeling of the data in the new sensor node. In addition to gain the less computation advantage of incremental training, the online learning algorithm results in an accuracy of 82.2 percent in activity recognition.

We present a novel approach for monitoring beverage intake. Our system is composed of an ultrasonic sensor, an RGB color sensor, and machine learning algorithms. The system not only measures beverage volume but also detects beverage types. The sensor unit is lightweight that can be mounted on the lid of any drinking bottle. Our experimental results demonstrate that the proposed approach achieves more than 97% accuracy in beverage type classification. Furthermore, our regression-based volume measurement has a nominal error of 3%.

Wearable technologies play a central role in human-centered Internet-of-Things applications. Wearables leverage machine learning algorithms to detect events of interest such as physical activities and medical complications. These algorithms, however, need to be retrained upon any changes in configuration of the system, such as addition/ removal of a sensor to/ from the network or displacement/ misplacement/ mis-orientation of the physical sensors on the body. We challenge this retraining model by stimulating the vision of autonomous learning with the goal of eliminating the labor-intensive, time-consuming, and highly expensive process of collecting labeled training data in dynamic environments. We propose an approach for autonomous retraining of the machine learning algorithms in real-time without need for any new labeled training data. We focus on a dynamic setting where new sensors are added to the system and worn on various body locations. We capture the inherent correlation between observations made by a static sensor view for which trained algorithms exist and the new dynamic sensor views for which an algorithm needs to be developed. By applying our real-time dynamic-view autonomous learning approach, we achieve an average accuracy of 81.1% in activity recognition using three experimental datasets. This amount of accuracy represents more than 13.8% improvement in the accuracy due to the automatic labeling of the sensor data in the newly added sensor. This performance is only 11.2% lower than the experimental upper bound where labeled training data are collected with the new sensor.

Wearable technologies play a central role in human-centered Internet-of-Things applications. Wearables leverage computational and machine learning algorithms to detect events of interest such as physical activities and medical complications. A major obstacle in large-scale utilization of current wearables is that their computational algorithms need to be re-built from scratch upon any changes in the configuration of the network. Retraining of these algorithms requires significant amount of labeled training data, a process that is labor-intensive, time-consuming, and infeasible. We propose an approach for automatic retraining of the machine learning algorithms in real-time without need for any labeled training data. We measure the inherent correlation between observations made by an old sensor view for which trained algorithms exist and the new sensor view for which an algorithm needs to be developed. By applying our real-time multi-view autonomous learning approach, we achieve an accuracy of 80.66% in activity recognition, which is an improvement of 15.96% in the accuracy due to the automatic labeling of the data in the new sensor node. This performance is only 7.96% lower than the experimental upper bound where labeled training data are collected with the new sensor.

Human-centered Internet-of-Things (IoT) applications utilize computational algorithms such as machine learning and signal processing techniques to infer knowledge about important events such as physical activities and medical complications. The inference is typically based on data collected with wearable sensors or those embedded in the environment. A major obstacle in large-scale utilization of these systems is that the computational algorithms cannot be shared between users or reused in contexts different than the setting in which the training data are collected. For example, an activity recognition algorithm trained for a wrist-band sensor cannot be used on a smartphone worn on the waist. We propose an approach for automatic detection of physical sensor-contexts (e.g., on-body sensor location) without need for collecting new labeled training data. Our techniques enable system designers and end-users to share and reuse computational algorithms that are trained under different contexts and data collection settings. We develop a framework to autonomously identify sensor-context. We propose a gating function to automatically activate the most accurate computational algorithm among a set of shared expert models. Our analysis based on real data collected with human subjects while performing 12 physical activities demonstrate that the accuracy of our multi-view learning is only 7.9% less than the experimental upper bound for activity recognition using a dynamic sensor constantly migrating from one on-body location to another. We also compare our approach with several mixture-of-experts models and transfer learning techniques and demonstrate that our approach outperforms algorithms in both categories.

Metabolic equivalent of task (MET) indicates the intensity of physical activities. This measurement is used in providing physical activity intervention in many chronic illnesses such as coronary heart disease, type-2 diabetes, and cancer. Due to the small size, portability, low power consumption, and low cost, wearable motion sensors are widely used to estimate MET values. However, one major obstacle in widespread adoption of current wearable monitoring systems is that the sensors must be worn on predefined locations on the body. This imposes much discomfort for users as they are not allowed to wear the sensors on their own desired body locations. In addition, non-adherence to the predefined location of the sensors results in significant reduction in the accuracy of physical activity monitoring. In this paper, we propose a framework for sensor location-independent MET estimation. We introduce a sensor localization approach that allows users to wear the sensors on different body locations without having to adhere to a specific installation protocol. We study how such an algorithm impacts the performance of MET estimation algorithms. Using daily physical activity data, we demonstrate that an automatic sensor localization algorithm decreases the estimation error of the MET calculation by a factor of 2.3 compared to the case without sensor localization. Furthermore, our sensor localization algorithm achieves an accuracy of 90.8% in detecting on-body locations of wearable sensors. The integration of sensor localization and MET estimation achieves an accuracy of 80% in calculating the MET values of daily physical activities.