Concomitant sensing and actuation for piezoelectric microrobots

Jayaram, Kaushik; Jafferis, Noah T.; Doshi, Neel; Goldberg, Benjamin A.; Wood, Robert J.

doi:10.1088/1361-665x/aabdf1

Cited by 48 publications

(39 citation statements)

References 50 publications

(76 reference statements)

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“…Eight off-board piezoelectric encoders provide measurements of actuator tip-velocities (q a ∈ R 8 ) [38]. Though these sensors are currently off-board, an onboard implementation is straightforward as the components are both light (< 10 mg) and small (< 5 mm 2 ).…”

Section: Sensor Design and Dynamicsmentioning

confidence: 99%

Effective locomotion at multiple stride frequencies using proprioceptive feedback on a legged microrobot

et al. 2019

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Limitations in actuation, sensing, and computation have forced small legged robots to rely on carefully tuned, mechanically mediated leg trajectories for effective locomotion. Recent advances in manufacturing, however, have enabled the development of small legged robots capable of operation at multiple stride frequencies using multi-degree-of-freedom leg trajectories. Proprioceptive sensing and control is key to extending the capabilities of these robots to a broad range of operating conditions. In this work, we use concomitant sensing for piezoelectric actuation with a computationally efficient framework for estimation and control of leg trajectories on a quadrupedal microrobot. We demonstrate accurate position estimation (<16 % root-mean-square error) and control (<16 % root-mean-square tracking error) during locomotion across a wide range of stride frequencies (10 Hz to 50 Hz). This capability enables the exploration of two blue bioinspired parametric leg trajectories designed to reduce leg slip and increase locomotion performance (e.g., speed, cost-of-transport, etc.). Using this approach, we demonstrate high performance locomotion at stride frequencies of (10 Hz to 30 Hz) where the robot's natural dynamics result in poor open-loop locomotion. Furthermore, we validate the biological hypotheses that inspired the our trajectories and identify regions of highly dynamic locomotion, low cost-oftransport (3.33), and minimal leg slippage (< 10 %).

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Section: Sensor Design and Dynamicsmentioning

confidence: 99%

Effective locomotion at multiple stride frequencies using proprioceptive feedback on a legged microrobot

et al. 2019

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“…Five motion capture cameras (Vicon T040) track the position and orientation of the robot body and the position of the feet at 500 Hz with a latency of 11 ms. In addition, eight piezoelectric encoders (described below) provide low-latency estimates of actuator tip velocities at 2.5 kHz [18]. Finally, a high speed camera (Phantom v7.3) orthogonal to the sagittal plane records the motion of the robot at 500 Hz.…”

Section: A Locomotion Arenamentioning

confidence: 99%

“…6) provides an estimate of the corresponding actuator's tip velocity by computing the "mechanical" current (proportional to tip velocity [4]) produced in that actuator. This current, i m , can be computed by applying Kirchoff's law (18) to the measurement circuit in series with a lumped-parameter electrical model of an actuator:…”

Section: B Piezoelectric Encoder Dynamicsmentioning

confidence: 99%

“…The actuator is modeled as a capacitor, C, resistor, R, and current source, i m , in parallel. The voltage and frequency dependent values of R and C, and the value of the blocking factor ζ have been computed by Jayaram et al [18].…”

Section: B Piezoelectric Encoder Dynamicsmentioning

confidence: 99%

“…Schematic of lumped parameter electrical model of a single actuator (green) and associated piezoeletric encoder measurement circuit[18].…”

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confidence: 99%

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Planning locomotion trajectories for legged microrobots is challenging because of their complex morphology, high frequency passive dynamics, and discontinuous contact interactions with their environment. Consequently, such research is often driven by time-consuming experimental methods. As an alternative, we present a framework for systematically modeling, planning, and controlling legged microrobots. We develop a threedimensional dynamic model of a 1.5 g quadrupedal microrobot with complexity (e.g., number of degrees of freedom) similar to larger-scale legged robots. We then adapt a recently developed variational contact-implicit trajectory optimization method to generate feasible whole-body locomotion plans for this microrobot, and we demonstrate that these plans can be tracked with simple joint-space controllers. We plan and execute periodic gaits at multiple stride frequencies and on various surfaces. These gaits achieve high per-cycle velocities, including a maximum of 10.87 mm/cycle, which is 15% faster than previously measured velocities for this microrobot. Furthermore, we plan and execute a vertical jump of 9.96 mm, which is 78% of the microrobot's center-of-mass height. To the best of our knowledge, this is the first end-to-end demonstration of planning and tracking whole-body dynamic locomotion on a millimeter-scale legged microrobot.

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Protein‐Based Hydrogels that Actuate Self‐Folding Systems

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We describe an approach to build a chemo-mechatronic system inspired by self-folding robots. This system, which comprises a protein-based hydrogel bound to a low-profile laminate, responds to different aqueous environments by undergoing geometric transformations. This response is dependent on the thickness and stiffness of the templating hydrogel, which directly regulates the This article is protected by copyright. All rights reserved. 2 diffusion of water into and out of the platform to initiate its reversible shape changes. When modified to include more complex geometries, these controllable shape changes can also be used to selectively trigger multiple folding events, illustrating a new platform for chemically-initiated mechatronic devices. Together, our data show how compositionally discrete components are physically, chemically, and mechanically coupled together to generate a new actuator for bio-hybrid self-folding systems.

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Concomitant sensing and actuation for piezoelectric microrobots

Cited by 48 publications

References 50 publications

Effective locomotion at multiple stride frequencies using proprioceptive feedback on a legged microrobot

Effective locomotion at multiple stride frequencies using proprioceptive feedback on a legged microrobot

Contact-Implicit Optimization of Locomotion Trajectories for a Quadrupedal Microrobot

Protein‐Based Hydrogels that Actuate Self‐Folding Systems

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