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arXiv · 2205.10940

Toward smart composites: small-scale, untethered prediction and control for soft sensor/actuator systems

Sarah Aguasvivas Manzano·Vani Sundaram·Artemis Xu·Khoi Ly·Mark Rentschler·Robert Shepherd·Nikolaus Correll
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Abstract

We present formulation and open-source tools to achieve in-material model predictive control of sensor/actuator systems using learned forward kinematics and on-device computation. Microcontroller units (MCUs) that compute the prediction and control task while colocated with the sensors and actuators enable in-material untethered behaviors. In this approach, small parameter size neural network models learn forward kinematics offline. Our open-source compiler, nn4mc, generates code to offload these predictions onto MCUs. A Newton-Raphson solver then computes the control input in real time. We first benchmark this nonlinear control approach against a PID controller on a mass-spring-damper simulation. We then study experimental results on two experimental rigs with different sensing, actuation and computational hardware: a tendon-based platform with embedded LightLace sensors and a HASEL-based platform with magnetic sensors. Experimental results indicate effective high-bandwidth tracking of reference paths (greater than or equal to 120 Hz) with a small memory footprint (less than or equal to 6.4% of flash memory). The measured path following error does not exceed 2mm in the tendon-based platform. The simulated path following error does not exceed 1mm in the HASEL-based platform. The mean power consumption of this approach in an ARM Cortex-M4f device is 45.4 mW. This control approach is also compatible with Tensorflow Lite models and equivalent on-device code. In-material intelligence enables a new class of composites that infuse autonomy into structures and systems with refined artificial proprioception.

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Sarah Aguasvivas Manzano, Vani Sundaram, Artemis Xu, Khoi Ly, Mark Rentschler, Robert Shepherd, Nikolaus Correll. 2022-05-22. Toward smart composites: small-scale, untethered prediction and control for soft sensor/actuator systems. https://arxiv.org/abs/2205.10940

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