Robot Control based on Motor Primitives -- A Comparison of Two Approaches

Motor primitives are fundamental building blocks of a controller which enable dynamic robot behavior with minimal high-level intervention. By treating motor primitives as basic "modules," different modules can be sequenced or superimposed to generate a rich repertoire of motor behavior. In robotics, two distinct approaches have been proposed: Dynamic Movement Primitives (DMPs) and Elementary Dynamic Actions (EDAs). While both approaches instantiate similar ideas, significant differences also exist. This paper attempts to clarify the distinction and provide a unifying view by delineating the similarities and differences between DMPs and EDAs. We provide eight robot control examples, including sequencing or superimposing movements, managing kinematic redundancy and singularity, obstacle avoidance, and managing physical interaction. We show that the two approaches clearly diverge in their implementation. We also discuss how DMPs and EDAs might be combined to get the best of both approaches. With this detailed comparison, we enable researchers to make informed decisions to select the most suitable approach for specific robot tasks and applications.Comment: 22 pages, 11 figure

Intrusive effects of task-irrelevant information on visual selective attention: semantics and size

Attentional selection is a mechanism by which incoming sensory information is prioritized for further, detailed and more effective, processing. Given that attended information is privileged by the sensory system, understanding and predicting what information is granted prioritization becomes an important endeavor. It has been argued that salient events as well as information that is related to the current goal of the organism (i.e., task-relevant) receive such priority. Here, we propose that attentional prioritization is not limited to task-relevance, and discuss evidence showing that task-irrelevant, non-salient, high-level properties of unattended objects, namely object meaning and size, influence attentional allocation. Such intrusion of non-salient task-irrelevant high-level information points to the need to re-conceptualize and formally modify current models of attentional guidance

Exp[licit]-A Robot modeling Software based on Exponential Maps

$$Deriving a robot's equation of motion typically requires placing multiple coordinate frames, commonly using the Denavit-Hartenberg convention to express the kinematic and dynamic relationships between segments. This paper presents an alternative using the differential geometric method of Exponential Maps, which reduces the number of coordinate frame choices to two. The traditional and differential geometric methods are compared, and the conceptual and practical differences are detailed. The open-source software, Exp[licit], based on the differential geometric method, is introduced. It is intended for use by researchers and engineers with basic knowledge of geometry and robotics. Code snippets and an example application are provided to demonstrate the benefits of the differential geometric method and assist users to get started with the software.Comment: 8 pages, 5 figure

Securitization and Community-Based Protection Among Chin Refugees in Kuala Lumpur

This article examines refugee-led community organizations among Chin refugees from Myanmar in Kuala Lumpur. It uses a structuration analysis that recognizes refugee-led organizations as complex governance entities engaged in a dynamic relationship with (among others) national policies of securitization of forced migration and international humanitarian governance. This approach expands the existing literature on the securitization of forced migration by exploring refugees’ lived experiences in a context of south–south migration. It expands the literature on community-based protection by going beyond recognizing the existence of refugee-led organizations to analyse their construction, constitution and consequences. Three primary areas of work by Chin refugee groups are analysed in relation to their immediate activity and longer term effects: organization (‘building ethnic unity in adversity’), documentation (‘asserting a bureaucratic identity’) and socialization (‘learning to be illegal’). These long-term effects indicate the possible impact of local protection activities on macrostructural processes such as identity construction and migration choices.construction, constitution and consequences. Three primary areas of work by Chin refugee groups are analysed in relation to their immediate activity and longer term effects: organization (‘building ethnic unity in adversity’), documentation (‘asserting a bureaucratic identity’) and socialization (‘learning to be illegal’). These long-term effects indicate the possible impact of local protection activities on macrostructural processes such as identity construction and migration choices

Influence of seed aerosol surface area and oxidation rate on vapor wall deposition and SOA mass yields: a case study with α-pinene ozonolysis

Laboratory chambers, invaluable in atmospheric chemistry and aerosol formation studies, are subject to particle and vapor wall deposition, processes that need to be accounted for in order to accurately determine secondary organic aerosol (SOA) mass yields. Although particle wall deposition is reasonably well understood and usually accounted for, vapor wall deposition is less so. The effects of vapor wall deposition on SOA mass yields in chamber experiments can be constrained experimentally by increasing the seed aerosol surface area to promote the preferential condensation of SOA-forming vapors onto seed aerosol. Here, we study the influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene ozonolysis. The observations are analyzed using a coupled vapor–particle dynamics model to interpret the roles of gas–particle partitioning (quasi-equilibrium vs. kinetically limited SOA growth) and α-pinene oxidation rate in influencing vapor wall deposition. We find that the SOA growth rate and mass yields are independent of seed surface area within the range of seed surface area concentrations used in this study. This behavior arises when the condensation of SOA-forming vapors is dominated by quasi-equilibrium growth. Faster α-pinene oxidation rates and higher SOA mass yields are observed at increasing O3 concentrations for the same initial α-pinene concentration. When the α-pinene oxidation rate increases relative to vapor wall deposition, rapidly produced SOA-forming oxidation products condense more readily onto seed aerosol particles, resulting in higher SOA mass yields. Our results indicate that the extent to which vapor wall deposition affects SOA mass yields depends on the particular volatility organic compound system and can be mitigated through the use of excess oxidant concentrations

Task-irrelevant semantic properties of objects impinge on sensory representations within the early visual cortex

Objects can be described in terms of low-level (e.g., boundaries) and high-level properties (e.g., object semantics). While recent behavioral findings suggest that the influence of semantic relatedness between objects on attentional allocation can be independent of task-relevance, the underlying neural substrate of semantic influences on attention remains ill-defined. Here, we employ behavioral and functional magnetic resonance imaging (fMRI) measures to uncover the mechanism by which semantic information increases visual processing efficiency. We demonstrate that the strength of the semantic relatedness signal decoded from the left inferior frontal gyrus (IFG): (i) influences attention, producing behavioral semantic benefits; (ii) biases spatial attention maps in the intraparietal sulcus (IPS), subsequently modulating early visual cortex (EVC) activity; (iii) directly predicts the magnitude of behavioral semantic benefit. Together, these results identify a specific mechanism driving task-independent semantic influences on attention

Relationships between illness representations, physical activity and depression in chronic kidney disease

Background: Chronic Kidney Disease (CKD) is exacerbated by depression and confers significant healthcare costs. Whilst adverse impacts may be mitigated by physical activity, many patients with CKD remain physically inactive, with this physical inactivity potentially influenced by how CKD is appraised. Objectives: The study aims to explore the relationship between physical activity, depression and illness representations in CKD. Methods: Non-dialysing patients with CKD completed the Revised Illness Perception Questionnaire (IPQ-R), Beck Depression Inventory (BDI-II) and Short-Form International Physical Activity Questionnaire (IPAQ-SF) while demographic information was obtained via medical records. Correlation and regression analyses were conducted to determine the relationship of illness representations with levels of physical activity. Moderation and mediation analyses were performed to investigate the role of depression in any relationship between illness representations and physical activity levels. Results: Seventy respondents, with a mean age of 60 ± 16 years, the majority being male (60%), took part in the study. Of illness representation dimensions, personal control was positively associated with levels of physical activity (r=.288, p<.05) while timeline cyclical was a significant predictor (Beta=-.423, p=.008). Severity of depression was neither a moderator (b= .023, 95% CI [-.015, .061], t=1.201, p=.23) nor a mediator (b=-.021, BCa CI [-.082, .008], p=.33). Conclusions: Facets of illness representations had significant relationships with levels of physical activity. Future research concerning the development and validation of psychological interventions based on an illness representations framework for patients with CKD not on renal-replacement therapy is proposed. The efficacy of such interventions could be then evaluated using a randomised controlled method