ChainQueen: A Real-Time Differentiable Physical Simulator for Soft Robotics

Physical simulators have been widely used in robot planning and control. Among them, differentiable simulators are particularly favored, as they can be incorporated into gradient-based optimization algorithms that are efficient in solving inverse problems such as optimal control and motion planning. Simulating deformable objects is, however, more challenging compared to rigid body dynamics. The underlying physical laws of deformable objects are more complex, and the resulting systems have orders of magnitude more degrees of freedom and therefore they are significantly more computationally expensive to simulate. Computing gradients with respect to physical design or controller parameters is typically even more computationally challenging. In this paper, we propose a real-time, differentiable hybrid Lagrangian-Eulerian physical simulator for deformable objects, ChainQueen, based on the Moving Least Squares Material Point Method (MLS-MPM). MLS-MPM can simulate deformable objects including contact and can be seamlessly incorporated into inference, control and co-design systems. We demonstrate that our simulator achieves high precision in both forward simulation and backward gradient computation. We have successfully employed it in a diverse set of control tasks for soft robots, including problems with nearly 3,000 decision variables.Comment: In submission to ICRA 2019. Supplemental Video: https://www.youtube.com/watch?v=4IWD4iGIsB4 Project Page: https://github.com/yuanming-hu/ChainQuee

Constraint-aware coordinated construction of generic structures

This paper presents a constraint-aware decentralized approach to construction with teams of robots. We present an extension to existing work on a distributed controller for robotic construction of simple structures. Our previous work described a set of adaptive algorithms for constructing truss structures given a target geometry using continuous and graph-based equal-mass partitioning [1], [2]. Using this work as a foundation, we present an algorithm which performs construction tasks and conforms to physical constraints while considering those constraints to parallelize tasks. This is accomplished by defining a mass function which reflects the priority of part placement and prevents physically impossible states. This mass function generates a set of pointmasses in ℝn, and we present a novel algorithm for finding a locally optimal, equal-mass, convex tessellation of such a set.Boeing CompanyNational Science Foundation (U.S.).National Science Foundation (U.S.). Office of Emerging Frontiers in Research and Innovation (Grant #0735953)United States. Army Research Office. Multidisciplinary University Research Initiative. Swarms of Autonomous Robots and Mobile Sensors Project (Grant number N0014-09-1051)United States. Army Research Office. Multidisciplinary University Research Initiative. Scalable (Grant number 544252

Origami-Inspired Printed Robots

Robot manufacturing is currently highly specialized, time consuming, and expensive, limiting accessibility and customization. Existing rapid prototyping techniques (e.g., 3-D printing) can achieve complex geometries and are becoming increasingly accessible; however, they are limited to one or two materials and cannot seamlessly integrate active components. We propose an alternative approach called printable robots that takes advantage of available planar fabrication methods to create integrated electromechanical laminates that are subsequently folded into functional 3-D machines employing origami-inspired techniques. We designed, fabricated, and tested prototype origami robots to address the canonical robotics challenges of mobility and manipulation, and subsequently combined these designs to generate a new, multifunctional machine. The speed of the design and manufacturing process as well as the ease of composing designs create a new paradigm in robotic development, which has the promise to democratize access to customized robots for industrial, home, and educational use.National Science Foundation (U.S.). Expeditions Program (Grant CCF-1138967

Relating behaviours and therapeutic actions during AVATAR therapy dialogue: an observational study

OBJECTIVES: AVATAR therapy is a novel relational approach to working with distressing voices by engaging individuals in direct dialogue with a digital representation of their persecutory voice (the avatar). Critical to this approach is the avatar transition from abusive to conciliatory during the course of therapy. To date, no observational study has examined the moment-to-moment dialogical exchanges of this innovative therapy. We aim to (1) map relating behaviours between participants and their created avatars and (2) examine therapeutic actions delivered within AVATAR dialogue. METHOD: Twenty-five of the fifty-three AVATAR therapy completers were randomly selected from a randomized controlled trial (Craig et al. The Lancet Psychiatry, 5, 2018 and 31). Seventy-five audio recordings of active dialogue from sessions 1 and 4 and the last session were transcribed and analysed using a newly developed coding frame. Inter-rater reliability was good to excellent. RESULTS: Fine-grained analysis of 4,642 observations revealed nuanced communication around relational power and therapeutic activity. Early assertiveness work, reinforced by the therapist, focussed on increasing power and distancing. Participants’ submissive behaviours reduced during therapy, but the shift was gradual. Once the transition to a more conciliatory tone took place, the dialogue primarily involved direct communication between participant and avatar, focussing on sense of self and developmental and relational understanding of voices. CONCLUSIONS: AVATAR therapy supports voice-hearers in becoming more assertive towards a digital representation of their abusive voice. Direct dialogue with carefully characterized avatars aims to build the voice-hearers’ positive sense of self, supporting the person to make sense of their experiences. PRACTITIONER POINTS: AVATAR therapy enables voice-hearers to engage in face-to-face dialogue with a digital representation (‘avatar’) of their persecutory voice. Fine-grained analyses showed how relating behaviours and therapeutic actions evolve during active AVATAR therapy dialogue. Carefully characterized avatars and direct therapist input help voice-hearers become more assertive over the avatar, enhance positive sense of self, and support individuals to make sense of their experiences

Computational Markets to Regulate Mobile-Agent Systems

Mobile-agent systems allow applications to distribute their resource consumption across the network. By prioritizing applications and publishing the cost of actions, it is possible for applications to achieve faster performance than in an environment where resources are evenly shared. We enforce the costs of actions through markets where user applications bid for computation from host machines. \par We represent applications as collections of mobile agents and introduce a distributed mechanism for allocating general computational priority to mobile agents. We derive a bidding strategy for an agent that plans expenditures given a budget and a series of tasks to complete. We also show that a unique Nash equilibrium exists between the agents under our allocation policy. We present simulation results to show that the use of our resource-allocation mechanism and expenditure-planning algorithm results in shorter mean job completion times compared to traditional mobile-agent resource allocation. We also observe that our resource-allocation policy adapts favorably to allocate overloaded resources to higher priority agents, and that agents are able to effectively plan expenditures even when faced with network delay and job-size estimation error

Compliant Electric Actuators Based on Handed Shearing Auxetics

In this paper, we explore a new class of electric motor-driven compliant actuators based on handed shearing auxetic cylinders. This technique combines the benefits of compliant bodies from soft robotic actuators with the simplicity of direct coupling to electric motors. We demonstrate the effectiveness of this technique by creating linear actuators, a four degree-of-freedom robotic platform, and a soft robotic gripper. We compare the soft robotic gripper against a state of the art pneumatic soft gripper, finding similar grasping performance in a significantly smaller and more energy-efficient package.Boeing CompanyNational Science Foundation (U.S.) (grant numbers NSF IIS- 1226883)National Science Foundation (U.S.) (grant numbers NSF CCF-1138967

Nature of acoustic nonlinear radiation stress

When a fluid is insonified with ultrasound, a flow consequence of a net stress becomes observable, which has been described as acoustic streaming, quartz wind, acoustic radiation force or acoustic fountain. Following Sir James Lighthill's formulation of the Reynold's streaming, these phenomena have been attributed to a cumulative viscous effect. Instead, a new multiscale effect, whereby the constitutive elastic nonlinearity scales from the ultrasonic to the macroscopic time, is here proposed and formulated to explain its origin. This raises a new term in the Navier-Stokes equation, which ultimately stems from the anharmonicity of the atomic potential. In our experimental validation, this theory is consistent in water and for a range of ultrasonic configurations, whereas the formerly established viscous theory fails by an order of magnitude. This ultrasonic-fluid interaction, called nonlinear mechanical radiation since it is able to remotely exert a stress field, correctly explains a wide range of industrial and biomedical active ultrasonic uses including jet engines, acoustic tweezers, cyanobacteria propulsion mechanisms, nanofluidics or acoustic radiation force elastography.Ministerio de Economía y Competitividad (Spain) for Project DPI2010-17065, and Junta de Andalucía for Projects P11-CTS-8089 and GGI3000IDIB

Antisense PMO Found in Dystrophic Dog Model Was Effective in Cells from Exon 7-Deleted DMD Patient

BACKGROUND: Antisense oligonucleotide-induced exon skipping is a promising approach for treatment of Duchenne muscular dystrophy (DMD). We have systemically administered an antisense phosphorodiamidate morpholino oligomer (PMO) targeting dystrophin exons 6 and 8 to a dog with canine X-linked muscular dystrophy in Japan (CXMD(J)) lacking exon 7 and achieved recovery of dystrophin in skeletal muscle. To date, however, antisense chemical compounds used in DMD animal models have not been directly applied to a DMD patient having the same type of exon deletion. We recently identified a DMD patient with an exon 7 deletion and tried direct translation of the antisense PMO used in dog models to the DMD patient's cells. METHODOLOGY/PRINCIPAL FINDINGS: We converted fibroblasts of CXMD(J) and the DMD patient to myotubes by FACS-aided MyoD transduction. Antisense PMOs targeting identical regions of dog and human dystrophin exons 6 and 8 were designed. These antisense PMOs were mixed and administered as a cocktail to either dog or human cells in vitro. In the CXMD(J) and human DMD cells, we observed a similar efficacy of skipping of exons 6 and 8 and a similar extent of dystrophin protein recovery. The accompanying skipping of exon 9, which did not alter the reading frame, was different between cells of these two species. CONCLUSION/SIGNIFICANCE: Antisense PMOs, the effectiveness of which has been demonstrated in a dog model, achieved multi-exon skipping of dystrophin gene on the FACS-aided MyoD-transduced fibroblasts from an exon 7-deleted DMD patient, suggesting the feasibility of systemic multi-exon skipping in humans