An obstacle disturbance selection framework: emergent robot steady states under repeated collisions

Natural environments are often filled with obstacles and disturbances. Traditional navigation and planning approaches normally depend on finding a traversable “free space” for robots to avoid unexpected contact or collision. We hypothesize that with a better understanding of the robot–obstacle interactions, these collisions and disturbances can be exploited as opportunities to improve robot locomotion in complex environments. In this article, we propose a novel obstacle disturbance selection (ODS) framework with the aim of allowing robots to actively select disturbances to achieve environment-aided locomotion. Using an empirically characterized relationship between leg–obstacle contact position and robot trajectory deviation, we simplify the representation of the obstacle-filled physical environment to a horizontal-plane disturbance force field. We then treat each robot leg as a “disturbance force selector” for prediction of obstacle-modulated robot dynamics. Combining the two representations provides analytical insights into the effects of gaits on legged traversal in cluttered environments. We illustrate the predictive power of the ODS framework by studying the horizontal-plane dynamics of a quadrupedal robot traversing an array of evenly-spaced cylindrical obstacles with both bounding and trotting gaits. Experiments corroborate numerical simulations that reveal the emergence of a stable equilibrium orientation in the face of repeated obstacle disturbances. The ODS reduction yields closed-form analytical predictions of the equilibrium position for different robot body aspect ratios, gait patterns, and obstacle spacings. We conclude with speculative remarks bearing on the prospects for novel ODS-based gait control schemes for shaping robot navigation in perturbation-rich environments

Modulation of Robot Orientation via Leg-Obstacle Contact Positions

We study a quadrupedal robot traversing a structured (i.e., periodically spaced) obstacle field driven by an open-loop quasi-static trotting walk. Despite complex, repeated collisions and slippage between robot legs and obstacles, the robot’s horizontal plane body orientation (yaw) trajectory can converge in the absence of any body level feedback to stable steady state patterns. We classify these patterns into a series of “types” ranging from stable locked equilibria, to stable periodic oscillations, to unstable or mixed period oscillations. We observe that the stable equilibria can bifurcate to stable periodic oscillations and then to mixed period oscillations as the obstacle spacing is gradually increased. Using a 3D-reconstruction method, we experimentally characterize the robot leg-obstacle contact configurations at each step to show that the different steady patterns in robot orientation trajectories result from a self-stabilizing periodic pattern of leg-obstacle contact positions. We present a highly-simplified coupled oscillator model that predicts robot orientation pattern as a function of the leg-obstacle contact mechanism. We demonstrate that the model successfully captures the robot steady state for different obstacle spacing and robot initial conditions. We suggest in simulation that using the simplified coupled oscillator model we can create novel control strategies that allow multi-legged robots to exploit obstacle disturbances to negotiate randomly cluttered environments. For more information: Kod*lab (link to kodlab.seas.upenn.edu

Rapid In Situ Characterization of Soil Erodibility With a Field Deployable Robot

Predicting the susceptibility of soil to wind erosion is difficult because it is a multivariate function of grain size, soil moisture, compaction, and biological growth. Erosive agents like plowing and grazing also differ in mechanism from entrainment by fluid shear; it is unclear if and how erosion thresholds for each process are related. Here we demonstrate the potential to rapidly assemble empirical maps of erodibility while also examining what controls it, using a novel “plowing” test of surface-soil shear resistance (r) performed by a semi-autonomous robot. Field work at White Sands National Monument, New Mexico, United States, examined gradients in erodibility at two scales: (i) soil moisture changes from dry dune crest to wet interdune (tens of meters) and (ii) downwind-increasing dune stabilization associated with growth of plants and salt and biological crusts (kilometers). We found that soil moisture changes of a few percent corresponded to a doubling of r, a result confirmed by laboratory experiments, and that soil crusts conferred stability that was comparable to moisture effects. We then compared different mechanisms of mechanical perturbation in a controlled laboratory setting. A new “kick-out” test determines peak shear resistance of the surface soil as a proxy for yield strength. Kick-out resistance exhibited a relation with soil moisture that was distinct from the plowing test and that was correlated with the independently measured threshold-fluid stress for wind erosion. Results show that our new method maps soil erodibility in arid environments and provides an understanding of environmental controls on variations in soil erodibility. (For more information: Kod*lab

Design of overvoltage suppression filter based on high-frequency modeling of cable in SiC based motor drive

SiC-based motor drives have the advantages of achieving higher efficiency and higher power density than traditional Si-based motor drives, and are gradually being widely used in electric power transmission. Due to different application situations such as oil field and airplane, a long cable is applied between the motor drive and three-phase motor and the distance may exceed hundreds of meters, which will cause serious voltage reflection problem, damaging working life of the motor. Meanwhile, the high slew rate of output voltage created by SiC-based motor drive deteriorates this phenomenon. In order to solve this problem, we first analyze the principle and influencing factors of voltage reflection, and establish the equivalent circuit model of the long cable. Then we put forward design method of LRC passive filter to suppress voltage reflection, and give simulation analysis. At last we built an experimental platform to verify the effectiveness of the LRC passive filter in SiC-based motor drive, and the experimental results show that the LRC passive filter with optimized parameters has good suppression effect of voltage reflection

Associations of Social, Cultural, and Community Engagement With Health Care Utilization in the US Health and Retirement Study

IMPORTANCE: There is growing evidence for the health benefits associated with social, cultural, and community engagement (SCCE), including for supporting healthy behaviors. However, health care utilization is an important health behavior that has not been investigated in association with SCCE. OBJECTIVE: To examine the associations between SCCE and health care utilization. DESIGN, SETTING, AND PARTICIPANTS: This population-based cohort study used data from the 2008 to 2016 waves of the Health and Retirement Study (HRS), a longitudinal panel study using a nationally representative sample of the US population aged 50 years and older. Participants were eligible if they reported SCCE and health care utilization in the relevant HRS waves. Data were analyzed from July to September 2022. EXPOSURES: SCCE was measured with a 15-item Social Engagement scale (including community, cognitive, creative, or physical activities) at baseline (frequency) and longitudinally over 4 years (no, consistent, increased, or decreased engagement). MAIN OUTCOMES AND MEASURES: Health care utilization was assessed in association with SCCE within 4 overarching categories: inpatient care (ie, hospital stays, hospital readmissions, length of hospital stays), outpatient care (ie, outpatient surgery, physician visits, number of physician visits), dental care (including dentures), and community health care (ie, home health care, nursing home stays, nights in a nursing home). RESULTS: A total of 12 412 older adults (mean [SE] age, 65.0 [0.1] years; 6740 [54.3%] women) were included in short-term analyses with 2 years of follow-up. Independent of confounders, more SCCE was associated with shorter hospital stays (incidence rate ratio [IRR], 0.75; 95% CI, 0.58-0.98), greater odds of outpatient surgery (odds ratio [OR], 1.34; 95% CI, 1.12-1.60) and dental care (OR, 1.73; 95% CI, 1.46-2.05), and lower odds of home health care (OR, 0.75; 95% CI, 0.57-0.99) and nursing home stays (OR, 0.46; 95% CI, 0.29-0.71). Longitudinal analysis included 8635 older adults (mean [SE] age, 63.7 [0.1] years; 4784 [55.4%] women) with data on health care utilization 6 years after baseline. Compared with consistent SCCE, reduced SCCE or consistent nonparticipation in SCCE was associated with more inpatient care utilization, such as hospital stays (decreased SCCE: IRR, 1.29; 95% CI, 1.00-1.67; consistent nonparticipation: IRR, 1.32; 95% CI, 1.04-1.68) but lower levels of subsequent outpatient care, such as physician visits (decreased SCCE: OR, 0.68; 95% CI, 0.50-0.93; consistent nonparticipation: OR, 0.62; 95% CI, 0.46-0.82) and dental care utilization (decreased SCCE: OR, 0.68; 95% CI, 0.57-0.81; consistent nonparticipation: OR, 0.51; 95% CI, 0.44-0.60). CONCLUSIONS AND RELEVANCE: These findings suggest that more SCCE was associated with more dental and outpatient care utilization and reduced inpatient and community health care utilization. SCCE might be associated with shaping beneficial early and preventive health-seeking behaviors, facilitating health care decentralization and alleviating financial burden by optimizing health care utilization