A novel method of mathematical compression of the value function for polynomial (in the state) time complexity of value iteration / policy iteration

March 27, 2018 09:01 ,

Alex Gorodetsky, Sertac Karaman, and Youssef Marzouk, High-dimensional stochastic optimal control using continuous tensor decompositions, The International Journal of Robotics Research Vol 37, Issue 2-3, pp. 340 – 377, DOI: 10.1177/0278364917753994.

Motion planning and control problems are embedded and essential in almost all robotics applications. These problems are often formulated as stochastic optimal control problems and solved using dynamic programming algorithms. Unfortunately, most existing algorithms that guarantee convergence to optimal solutions suffer from the curse of dimensionality: the run time of the algorithm grows exponentially with the dimension of the state space of the system. We propose novel dynamic programming algorithms that alleviate the curse of dimensionality in problems that exhibit certain low-rank structure. The proposed algorithms are based on continuous tensor decompositions recently developed by the authors. Essentially, the algorithms represent high-dimensional functions (e.g. the value function) in a compressed format, and directly perform dynamic programming computations (e.g. value iteration, policy iteration) in this format. Under certain technical assumptions, the new algorithms guarantee convergence towards optimal solutions with arbitrary precision. Furthermore, the run times of the new algorithms scale polynomially with the state dimension and polynomially with the ranks of the value function. This approach realizes substantial computational savings in “compressible” problem instances, where value functions admit low-rank approximations. We demonstrate the new algorithms in a wide range of problems, including a simulated six-dimensional agile quadcopter maneuvering example and a seven-dimensional aircraft perching example. In some of these examples, we estimate computational savings of up to 10 orders of magnitude over standard value iteration algorithms. We further demonstrate the algorithms running in real time on board a quadcopter during a flight experiment under motion capture.

Posted in: Probability and statistics, Robot motion planning , Tagged: , , , ,

A microprocessor designed for real-time predictability and short WCETs

March 26, 2018 08:58 ,

Schoeberl, M., Puffitsch, W., Hepp, S. et al, Patmos: a time-predictable microprocessor, Real-Time Syst (2018) 54: 389, DOI: 10.1007/s11241-018-9300-4.

Current processors provide high average-case performance, as they are optimized for general purpose computing. However, those optimizations often lead to a high worst-case execution time (WCET). WCET analysis tools model the architectural features that increase average-case performance. To keep analysis complexity manageable, those models need to abstract from implementation details. This abstraction further increases the WCET bound. This paper presents a way out of this dilemma: a processor designed for real-time systems. We design and optimize a processor, called Patmos, for low WCET bounds rather than for high average-case performance. Patmos is a dual-issue, statically scheduled RISC processor. A method cache serves as the cache for the instructions and a split cache organization simplifies the WCET analysis of the data cache. To fill the dual-issue pipeline with enough useful instructions, Patmos relies on a customized compiler. The compiler also plays a central role in optimizing the application for the WCET instead of average-case performance.

Posted in: Electronics, Real-Time Systems , Tagged: , ,

On how seeking for the lowest-cost action is not always what happens in reality

March 21, 2018 08:51 ,

Michael Inzlicht, Amitai Shenhav, Christopher Y. Olivola, The Effort Paradox: Effort Is Both Costly and Valued, Trends in Cognitive Sciences, Volume 22, Issue 4, 2018, Pages 337-349, DOI: 10.1016/j.tics.2018.01.007.

According to prominent models in cognitive psychology, neuroscience, and economics, effort (be it physical or mental) is costly: when given a choice, humans and non-human animals alike tend to avoid effort. Here, we suggest that the opposite is also true and review extensive evidence that effort can also add value. Not only can the same outcomes be more rewarding if we apply more (not less) effort, sometimes we select options precisely because they require effort. Given the increasing recognition of effort’s role in motivation, cognitive control, and value-based decision-making, considering this neglected side of effort will not only improve formal computational models, but also provide clues about how to promote sustained mental effort across time.

Posted in: Psycho-physiological bases of engineering , Tagged:

On how children learn with progressive environment changes aimed at improving their learning statistically

March 21, 2018 08:49 ,

Linda B. Smith, Swapnaa Jayaraman, Elizabeth Clerkin, Chen Yu, The Developing Infant Creates a Curriculum for Statistical Learning, Trends in Cognitive Sciences, Volume 22, Issue 4, 2018, Pages 325-336, DOI: 10.1016/j.tics.2018.02.004.

New efforts are using head cameras and eye-trackers worn by infants to capture everyday visual environments from the point of view of the infant learner. From this vantage point, the training sets for statistical learning develop as the sensorimotor abilities of the infant develop, yielding a series of ordered datasets for visual learning that differ in content and structure between timepoints but are highly selective at each timepoint. These changing environments may constitute a developmentally ordered curriculum that optimizes learning across many domains. Future advances in computational models will be necessary to connect the developmentally changing content and statistics of infant experience to the internal machinery that does the learning.

Posted in: Psycho-physiological bases of engineering , Tagged:

A theory that integrates motivation and control

March 21, 2018 08:46 ,

Giovanni Pezzulo, Francesco Rigoli, Karl J. Friston, Hierarchical Active Inference: A Theory of Motivated Control, Trends in Cognitive Sciences, Volume 22, Issue 4, 2018, Pages 294-306, DOI: 10.1016/j.tics.2018.01.009.

Motivated control refers to the coordination of behaviour to achieve affectively valenced outcomes or goals. The study of motivated control traditionally assumes a distinction between control and motivational processes, which map to distinct (dorsolateral versus ventromedial) brain systems. However, the respective roles and interactions between these processes remain controversial. We offer a novel perspective that casts control and motivational processes as complementary aspects − goal propagation and prioritization, respectively − of active inference and hierarchical goal processing under deep generative models. We propose that the control hierarchy propagates prior preferences or goals, but their precision is informed by the motivational context, inferred at different levels of the motivational hierarchy. The ensuing integration of control and motivational processes underwrites action and policy selection and, ultimately, motivated behaviour, by enabling deep inference to prioritize goals in a context-sensitive way.

Posted in: Psycho-physiological bases of engineering , Tagged:

A critic of the “two types of thinking” myth (deliberative, slow, rational, optimal vs. reactive, quick, emotional, suboptimal)

March 21, 2018 08:43 ,

David E. Melnikoff, John A. Bargh, The Mythical Number Two, Trends in Cognitive Sciences, Volume 22, Issue 4, 2018, Pages 280-293, DOI: 10.1016/j.tics.2018.02.001.

It is often said that there are two types of psychological processes: one that is intentional, controllable, conscious, and inefficient, and another that is unintentional, uncontrollable, unconscious, and efficient. Yet, there have been persistent and increasing objections to this widely influential dual-process typology. Critics point out that the ‘two types’ framework lacks empirical support, contradicts well-established findings, and is internally incoherent. Moreover, the untested and untenable assumption that psychological phenomena can be partitioned into two types, we argue, has the consequence of systematically thwarting scientific progress. It is time that we as a field come to terms with these issues. In short, the dual-process typology is a convenient and seductive myth, and we think cognitive science can do better.

Posted in: Psycho-physiological bases of engineering , Tagged:

A standard format for robotic maps

March 15, 2018 10:01 ,

F. Amigoni et al, A Standard for Map Data Representation: IEEE 1873-2015 Facilitates Interoperability Between Robots, IEEE Robotics & Automation Magazine, vol. 25, no. 1, pp. 65-76, DOI: 10.1109/MRA.2017.2746179.

The availability of environment maps for autonomous robots enables them to complete several tasks. A new IEEE standard, IEEE 1873-2015, Robot Map Data Representation for Navigation (MDR) [15], sponsored by the IEEE Robotics and Automation Society (RAS) and approved by the IEEE Standards Association Standards Board in September 2015, defines a common representation for two-dimensional (2-D) robot maps and is intended to facilitate interoperability among navigating robots. The standard defines an extensible markup language (XML) data format for exchanging maps between different systems. This article illustrates how metric maps, topological maps, and their combinations can be represented according to the standard.

Posted in: Mobile robot mapping

A gentle tutorial on Industrial Ethernet

March 15, 2018 09:58 ,

K. Langlois et al., EtherCAT Tutorial: An Introduction for Real-Time Hardware Communication on Windows [Tutorial], IEEE Robotics & Automation Magazine, vol. 25, no. 1, pp. 22-122, DOI: 10.1109/MRA.2017.2787224.

Setting up real-time hardware communication for applications such as precise motion control can be time consuming and confusing. Therefore, this tutorial introduces the deployment of an Ethernet for control automation technology (EtherCAT) protocol. We situate EtherCAT, briefly discuss the origins and working principles, and mention advantages over other widely used protocols. Additionally, the main objectives of the tutorial and the required software to complete it are presented. Online supplements are included, explaining all steps to run a Simulink model in real time on a Windows machine within a few hours.

Posted in: Communication networks , Tagged: ,

Survey on the concept of affordance and its use in robotics (the rest of this issue of the journal also deals with affordances in robotics)

March 15, 2018 09:54 ,

L. Jamone et al, Affordances in Psychology, Neuroscience, and Robotics: A Survey,, IEEE Transactions on Cognitive and Developmental Systems, vol. 10, no. 1, pp. 4-25, March 2018, DOI: 10.1109/TCDS.2016.2594134.

The concept of affordances appeared in psychology during the late 60s as an alternative perspective on the visual perception of the environment. It was revolutionary in the intuition that the way living beings perceive the world is deeply influenced by the actions they are able to perform. Then, across the last 40 years, it has influenced many applied fields, e.g., design, human-computer interaction, computer vision, and robotics. In this paper, we offer a multidisciplinary perspective on the notion of affordances. We first discuss the main definitions and formalizations of the affordance theory, then we report the most significant evidence in psychology and neuroscience that support it, and finally we review the most relevant applications of this concept in robotics.

Posted in: Psycho-physiological bases of engineering , Tagged: ,

A study of the influence of teleoperation in the remote driving of robots

March 12, 2018 09:45 ,

Storms, J. & Tilbury, D. J, A New Difficulty Index for Teleoperated Robots Driving through Obstacles, Intell Robot Syst (2018) 90: 147, DOI: 10.1007/s10846-017-0651-1.

Teleoperation allows humans to reach environments that would otherwise be too difficult or dangerous. The distance between the human operator and remote robot introduces a number of issues that can negatively impact system performance including degraded and delayed information exchange between the robot and human. Some operation scenarios and environments can tolerate these degraded conditions, while others cannot. However, little work has been done to investigate how factors such as communication delay, automation, and environment characteristics interact to affect teleoperation system performance. This paper presents results from a user study analyzing the effects of teleoperation factors including communication delay, autonomous assistance, and environment layout on user performance. A mobile robot driving task is considered in which subjects drive a robot to a goal location around obstacles as quickly (minimize time) and safely (avoid collisions) as possible. An environment difficulty index (ID) is defined in the paper and is shown to be able to predict the average time it takes for the human to drive the robot to a goal location with different obstacle configurations. The ID is also shown to predict the path chosen by the human better than travel time along that path.

Posted in: Human teleoperation