4 research outputs found
Smooth Model Predictive Path Integral Control without Smoothing
We present a sampling-based control approach that can generate smooth actions
for general nonlinear systems without external smoothing algorithms. Model
Predictive Path Integral (MPPI) control has been utilized in numerous robotic
applications due to its appealing characteristics to solve non-convex
optimization problems. However, the stochastic nature of sampling-based methods
can cause significant chattering in the resulting commands. Chattering becomes
more prominent in cases where the environment changes rapidly, possibly even
causing the MPPI to diverge. To address this issue, we propose a method that
seamlessly combines MPPI with an input-lifting strategy. In addition, we
introduce a new action cost to smooth control sequence during trajectory
rollouts while preserving the information theoretic interpretation of MPPI,
which was derived from non-affine dynamics. We validate our method in two
nonlinear control tasks with neural network dynamics: a pendulum swing-up task
and a challenging autonomous driving task. The experimental results demonstrate
that our method outperforms the MPPI baselines with additionally applied
smoothing algorithms.Comment: Accepted to IEEE Robotics and Automation Letters (and IROS 2022). Our
video can be found at https://youtu.be/ibIks6ExGw
Sleep Quality and Attention May Correlate With Hand Grip Strength: FARM Study
Objective To determine the socio-demographic, psychologic, hematologic, or other relevant factors associated with hand grip strength in Korean farmers. Methods A total of 528 healthy Korean farmers were enrolled. Hand grip strength was measured in both hands using a hydraulic dynamometer. Socio-demographic characteristics were assessed and anthropometric measurements were obtained. Psycho-cognitive measurements such as sleep quality (Pittsburgh Sleep Quality Index) and Go/No-Go test response time were conducted. In addition to physical measurements, serologic parameters including insulin-like growth factor 1 were measured. The factors associated with hand grip strength were analyzed using multiple linear regression analysis after adjusting for age, height, and weight. Results The mean hand grip strength was associated with the Pittsburgh Sleep Quality Index total score (β=-0.12, p=0.01), the Go/No-Go test response time (β=-0.18, p=0.001), vitamin D (β=0.12, p=0.02), and insulin-like growth factor 1 levels (β=0.1, p=0.045). In female farmers, hand grip strength was only associated with the Pittsburgh Sleep Quality Index total score (β=-0.32, p<0.001). Conclusion The results of this study demonstrate that hand grip strength was associated with sleep quality and attention in Korean farmers