The length of the acknowledgments section in a doctoral dissertation should be directly proportio... more The length of the acknowledgments section in a doctoral dissertation should be directly proportional to the time it took to complete it and inversely proportional to its contribution. Well, here is mine. Working with Prof. G. de Veciana was a blessing which came initially in disguise. It would take me long to describe the various ways I benefited from him but Gustavo's reputation precedes him. Therefore, I will not repeat his well known virtues and talents. I will just express my gratitude to him for his trust and will paraphrase the famous mathematician G. H. Hardy 1 in writing that "I still say to myself when I am depressed, and find myself forced to listen to pompous and tiresome people, Well, I have done one the thing you could never have done, and that is to have collaborated with Gustavo on something like equal terms. It is to him that I owe an unusually late maturity". Writing this section it is my duty to mention the late Prof. Margarida Jacome. Margarida recruited me to UT Austin and introduced me to the field of pervasive computing. With her enormous engineering intuition she set the 1 G. H. Hardy "A mathematician's apology". v direction for my thesis. I am sorry she is not still with us to see the fruits of the seeds she planted. I would also like to thank the members of my PhD committee for their patience, if not anything else. Prof. V. Garg introduced me to distributed systems through his excellent course and gave me an idea of what a relentless researcher looks like. Prof. A. Mok was sensitive enough to hire me as his TA for his course on fault-tolerant distributed systems at the time of Margarida's illness. Interacting with him was one of the most motivating experiences in my academic life. Prof. C. Julien, the local expert on pervasive computing, influenced me positively through the academic environment she created with her lab and her course on Formal Methods. Additionally, she provided the most helpful and well articulated 'criticism' to my thesis. Prof. N. Touba and Dr. M. Breternitz Jr. added helpful diversity to my committee. In my long journey to graduate school, the two most stable companions were P. Aliferis and D. Peroulis. Friends, mentors, and drivers at different times, they never failed to maintain communication in person, through email, Skype, or on the phone. It is not an exaggeration to say that they were the closest to family I ever had, apart from my family. At UT the names of two colleagues stand out. V. Rajamani and B. Balasubramanian have formed the 'inner sanctum' of my social circle. They stayed close through thick and thin. Above all, they are two interesting individuals and it still gives me pleasure to discuss with them a multitude of topics. Additionally, Vasanth mentored me successfully through my job search.
28th IEEE International Real-Time Systems Symposium (RTSS 2007), 2007
Recent technological advances have opened up several distributed real-time applications involving... more Recent technological advances have opened up several distributed real-time applications involving battery-driven embedded devices with local processing and wireless communication capabilities. Energy management is the key issue in the design and operation of such systems. In this paper, we consider a single-hop networked real-time embedded system where each node supports both dynamic voltage scaling (DVS) and dynamic modulation scaling (DMS) power management techniques to tradeoff time for energy savings. In this model, we address the problem of scheduling periodic complex tasks where each task consists of several precedence constrained message passing sub-tasks. Our contributions towards this problem are two fold. First, we analyze the system level energy-time tradeoffs considering both the computation and communication workloads by defining a novel energy gain metric. We then present static (centralized) and dynamic (distributed) energy gain based slack allocation algorithms which reduce the total energy consumption, while guaranteeing the ready time, deadline and precedence constraints. We compare the performance of the proposed algorithms with several baseline algorithms through simulation studies. Our results show that the proposed algorithms perform significantly better than the baseline algorithms for the simulated conditions. Finally, we identify several interesting energy-aware research problems in the area of networked real-time embedded systems.
We consider the problem of resource provisioning for real-time cyber-physical applications in an ... more We consider the problem of resource provisioning for real-time cyber-physical applications in an open system environment where there does not exist a global resource scheduler that has complete knowledge of the real-time performance requirements of each individual application that shares the resources with the other applications. Regularity-based Resource Partition (RRP) model is an effective strategy to hierarchically partition and assign various resource slices among such applications. However, previous work on RRP model only discusses uniform resource environment, where resources are implicitly assumed to be synchronized and clocked at the same frequency. The challenge is that a task utilizing multiple resources may experience unexpected delays in non-uniform environments, where resources are clocked at different frequencies. This paper extends the RRP model to non-uniform multi-resource open system environments to tackle this problem. It first introduces a novel composite resour...
A cyberphysical avatar is a semi-autonomous robot that adjusts to an unstructured environment and... more A cyberphysical avatar is a semi-autonomous robot that adjusts to an unstructured environment and performs physical tasks subject to critical timing constraints while under human supervision. This article first realizes a cyberphysical avatar that integrates three key technologies: body-compliant control, neuroevolution, and real-time constraints. Body-compliant control is essential for operator safety, because avatars perform cooperative tasks in close proximity to humans; neuroevolution (NEAT) enables “programming” avatars such that they can be used by non-experts for a large array of tasks, some unforeseen, in an unstructured environment; and real-time constraints are indispensable to provide predictable, bounded-time response in human-avatar interaction. Then, we present a study on the tradeoffs between three design parameters for robotic task systems that must incorporate at least three dimensions: (1) the amount of training effort for robot to perform the task, (2) the time av...
The Cloudbased Advanced Robotics Laboratory (CARL) integrates a whole body controller and webbase... more The Cloudbased Advanced Robotics Laboratory (CARL) integrates a whole body controller and webbased teleoperation to enable any device with a web browser to access and control a humanoid robot. By integrating humanoid robots with the cloud, they are accessible from any Internetconnected device. Increased accessibility is important because few people have access to stateoftheart humanoid robots limiting their rate of development. CARL's implementation is based on modern software libraries, frameworks, and middleware including Node.js, Socket.IO, ZMQ, ROS, Robot Web Tools, and ControlIt!. Feasibility is demonstrated by having inexperienced human operators use a smartphone's web browser to control Dreamer, a torquecontrolled humanoid robot based on series elastic actuators, and make it perform a dualarm manipulation task. The implementation serves as a proof of concept and foundation upon which many advanced humanoid robot technologies can be researched and developed.
our probabilistic data stream model where each data value is given by a probability distribution.... more our probabilistic data stream model where each data value is given by a probability distribution. In particular, for uniform and gaussian distributions, we show how we derive a set of constraints on distribution parameters as a metric of similarity distances, exploiting the semantics of probabilistic queries being monitored. The derived constraints enable us to formulate the probabilistic similarity region that suppresses unnecessary data transmission in a monitoring system.
In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key r... more In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key results in real-time scheduling theory and the historical events that led to the establishment of the current realtime computing infrastructure. We conclude this paper by looking at the challenges ahead of us.
A process control system manages fluid processes in a factory plant. It typically reads temperatu... more A process control system manages fluid processes in a factory plant. It typically reads temperatures, speeds, etc. from the plant via smart sensors and adjusts the process via smart actuators like valves and motors. In many cases the control system and the smart devices are from different vendors. Fortunately, industry standards have been established for the communications among them. These standards are based on wireline networks; they are no longer suitable for wireless networks. In this paper we discuss the interoperability issues related to wireless communication among process control system components.
: The objective of the project is to be able to predict welding failures in real time and correct... more : The objective of the project is to be able to predict welding failures in real time and correct them as quickly as possible. This will be a drastic shift from the current statistically controlled manufacturing to dynamic model based manufacturing control.
2008 IEEE Real-Time and Embedded Technology and Applications Symposium, 2008
Wireless technology has been regarded as a paradigm shifter in the process industry. The first op... more Wireless technology has been regarded as a paradigm shifter in the process industry. The first open wireless communication standard specifically designed for process measurement and control applications, WirelessHART was officially released in September 2007 (as a part of the HART 7 Specification). WirelessHART is a secure and TDMAbased wireless mesh networking technology operating in the 2.4GHz ISM radio band. In this paper, we give an introduction to the architecture of WirelessHART and share our first-hand experience in building a prototype for this specification. We describe several challenges we had to tackle during the implementation, such as the design of the timer, network wide synchronization, communication security, reliable mesh networking, and the central network manager. For each challenge, we provide a detailed analysis and propose our solution. Based on the prototype implementation, a simple WirelessHART network has been built for the purpose of demonstration. The demonstration network in turn validates our design. To the best of our knowledge, this is the first reported effort to build a WirelessHART protocol stack.
The length of the acknowledgments section in a doctoral dissertation should be directly proportio... more The length of the acknowledgments section in a doctoral dissertation should be directly proportional to the time it took to complete it and inversely proportional to its contribution. Well, here is mine. Working with Prof. G. de Veciana was a blessing which came initially in disguise. It would take me long to describe the various ways I benefited from him but Gustavo's reputation precedes him. Therefore, I will not repeat his well known virtues and talents. I will just express my gratitude to him for his trust and will paraphrase the famous mathematician G. H. Hardy 1 in writing that "I still say to myself when I am depressed, and find myself forced to listen to pompous and tiresome people, Well, I have done one the thing you could never have done, and that is to have collaborated with Gustavo on something like equal terms. It is to him that I owe an unusually late maturity". Writing this section it is my duty to mention the late Prof. Margarida Jacome. Margarida recruited me to UT Austin and introduced me to the field of pervasive computing. With her enormous engineering intuition she set the 1 G. H. Hardy "A mathematician's apology". v direction for my thesis. I am sorry she is not still with us to see the fruits of the seeds she planted. I would also like to thank the members of my PhD committee for their patience, if not anything else. Prof. V. Garg introduced me to distributed systems through his excellent course and gave me an idea of what a relentless researcher looks like. Prof. A. Mok was sensitive enough to hire me as his TA for his course on fault-tolerant distributed systems at the time of Margarida's illness. Interacting with him was one of the most motivating experiences in my academic life. Prof. C. Julien, the local expert on pervasive computing, influenced me positively through the academic environment she created with her lab and her course on Formal Methods. Additionally, she provided the most helpful and well articulated 'criticism' to my thesis. Prof. N. Touba and Dr. M. Breternitz Jr. added helpful diversity to my committee. In my long journey to graduate school, the two most stable companions were P. Aliferis and D. Peroulis. Friends, mentors, and drivers at different times, they never failed to maintain communication in person, through email, Skype, or on the phone. It is not an exaggeration to say that they were the closest to family I ever had, apart from my family. At UT the names of two colleagues stand out. V. Rajamani and B. Balasubramanian have formed the 'inner sanctum' of my social circle. They stayed close through thick and thin. Above all, they are two interesting individuals and it still gives me pleasure to discuss with them a multitude of topics. Additionally, Vasanth mentored me successfully through my job search.
28th IEEE International Real-Time Systems Symposium (RTSS 2007), 2007
Recent technological advances have opened up several distributed real-time applications involving... more Recent technological advances have opened up several distributed real-time applications involving battery-driven embedded devices with local processing and wireless communication capabilities. Energy management is the key issue in the design and operation of such systems. In this paper, we consider a single-hop networked real-time embedded system where each node supports both dynamic voltage scaling (DVS) and dynamic modulation scaling (DMS) power management techniques to tradeoff time for energy savings. In this model, we address the problem of scheduling periodic complex tasks where each task consists of several precedence constrained message passing sub-tasks. Our contributions towards this problem are two fold. First, we analyze the system level energy-time tradeoffs considering both the computation and communication workloads by defining a novel energy gain metric. We then present static (centralized) and dynamic (distributed) energy gain based slack allocation algorithms which reduce the total energy consumption, while guaranteeing the ready time, deadline and precedence constraints. We compare the performance of the proposed algorithms with several baseline algorithms through simulation studies. Our results show that the proposed algorithms perform significantly better than the baseline algorithms for the simulated conditions. Finally, we identify several interesting energy-aware research problems in the area of networked real-time embedded systems.
We consider the problem of resource provisioning for real-time cyber-physical applications in an ... more We consider the problem of resource provisioning for real-time cyber-physical applications in an open system environment where there does not exist a global resource scheduler that has complete knowledge of the real-time performance requirements of each individual application that shares the resources with the other applications. Regularity-based Resource Partition (RRP) model is an effective strategy to hierarchically partition and assign various resource slices among such applications. However, previous work on RRP model only discusses uniform resource environment, where resources are implicitly assumed to be synchronized and clocked at the same frequency. The challenge is that a task utilizing multiple resources may experience unexpected delays in non-uniform environments, where resources are clocked at different frequencies. This paper extends the RRP model to non-uniform multi-resource open system environments to tackle this problem. It first introduces a novel composite resour...
A cyberphysical avatar is a semi-autonomous robot that adjusts to an unstructured environment and... more A cyberphysical avatar is a semi-autonomous robot that adjusts to an unstructured environment and performs physical tasks subject to critical timing constraints while under human supervision. This article first realizes a cyberphysical avatar that integrates three key technologies: body-compliant control, neuroevolution, and real-time constraints. Body-compliant control is essential for operator safety, because avatars perform cooperative tasks in close proximity to humans; neuroevolution (NEAT) enables “programming” avatars such that they can be used by non-experts for a large array of tasks, some unforeseen, in an unstructured environment; and real-time constraints are indispensable to provide predictable, bounded-time response in human-avatar interaction. Then, we present a study on the tradeoffs between three design parameters for robotic task systems that must incorporate at least three dimensions: (1) the amount of training effort for robot to perform the task, (2) the time av...
The Cloudbased Advanced Robotics Laboratory (CARL) integrates a whole body controller and webbase... more The Cloudbased Advanced Robotics Laboratory (CARL) integrates a whole body controller and webbased teleoperation to enable any device with a web browser to access and control a humanoid robot. By integrating humanoid robots with the cloud, they are accessible from any Internetconnected device. Increased accessibility is important because few people have access to stateoftheart humanoid robots limiting their rate of development. CARL's implementation is based on modern software libraries, frameworks, and middleware including Node.js, Socket.IO, ZMQ, ROS, Robot Web Tools, and ControlIt!. Feasibility is demonstrated by having inexperienced human operators use a smartphone's web browser to control Dreamer, a torquecontrolled humanoid robot based on series elastic actuators, and make it perform a dualarm manipulation task. The implementation serves as a proof of concept and foundation upon which many advanced humanoid robot technologies can be researched and developed.
our probabilistic data stream model where each data value is given by a probability distribution.... more our probabilistic data stream model where each data value is given by a probability distribution. In particular, for uniform and gaussian distributions, we show how we derive a set of constraints on distribution parameters as a metric of similarity distances, exploiting the semantics of probabilistic queries being monitored. The derived constraints enable us to formulate the probabilistic similarity region that suppresses unnecessary data transmission in a monitoring system.
In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key r... more In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key results in real-time scheduling theory and the historical events that led to the establishment of the current realtime computing infrastructure. We conclude this paper by looking at the challenges ahead of us.
A process control system manages fluid processes in a factory plant. It typically reads temperatu... more A process control system manages fluid processes in a factory plant. It typically reads temperatures, speeds, etc. from the plant via smart sensors and adjusts the process via smart actuators like valves and motors. In many cases the control system and the smart devices are from different vendors. Fortunately, industry standards have been established for the communications among them. These standards are based on wireline networks; they are no longer suitable for wireless networks. In this paper we discuss the interoperability issues related to wireless communication among process control system components.
: The objective of the project is to be able to predict welding failures in real time and correct... more : The objective of the project is to be able to predict welding failures in real time and correct them as quickly as possible. This will be a drastic shift from the current statistically controlled manufacturing to dynamic model based manufacturing control.
2008 IEEE Real-Time and Embedded Technology and Applications Symposium, 2008
Wireless technology has been regarded as a paradigm shifter in the process industry. The first op... more Wireless technology has been regarded as a paradigm shifter in the process industry. The first open wireless communication standard specifically designed for process measurement and control applications, WirelessHART was officially released in September 2007 (as a part of the HART 7 Specification). WirelessHART is a secure and TDMAbased wireless mesh networking technology operating in the 2.4GHz ISM radio band. In this paper, we give an introduction to the architecture of WirelessHART and share our first-hand experience in building a prototype for this specification. We describe several challenges we had to tackle during the implementation, such as the design of the timer, network wide synchronization, communication security, reliable mesh networking, and the central network manager. For each challenge, we provide a detailed analysis and propose our solution. Based on the prototype implementation, a simple WirelessHART network has been built for the purpose of demonstration. The demonstration network in turn validates our design. To the best of our knowledge, this is the first reported effort to build a WirelessHART protocol stack.
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