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We present an off-board phase estimator and controller for leg position near the resonance of the Harvard Ambulatory MicroRobot's (HAMR) two degree-of-freedom transmission. This control system is a first step towards leveraging the significant increase in stride length at transmission resonance for faster and more efficient locomotion. We experimentally characterize HAMR's transmission and determine...
A multilayer fabrication method has been used to create crawling soft robots based on dielectric elastomer actuators. These actuators are created without the need for pre-stretch, eliminating the need for rigid components. A four-legged, multi-gait capable crawler can be fabricated in a matter of hours and shows promise for future untethered systems. Studies on inchworm robots show them to be the...
This paper presents an off-board trajectory controller for a range of stride frequencies (2–45 Hz) that enables zero-radius turns and holonomic control on one of the smallest and fastest legged robots, the Harvard Ambulatory MicroRobot (HAMR). An experimental model is used as the basis for control to capture the highly nonlinear response of the robot to input signals. Closed-loop trajectories are...
Self-folding provides an efficient way of creating complex 3D geometries from 2D composites. However, the precision of self-folding structures is often limited by the use of open-loop folding mechanisms. In this paper we demonstrate feedback-controlled self-folding using a shape memory polymer and optical sensors to accurately control folding angles. We present a method of quickly and inexpensively...
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...
Legged locomotion is an open problem in robotics, particularly for non-level surfaces. With decreasing robot size, different issues for climbing mechanisms and their attachment and detachment appear due to the physics of scaling. This paper describes micro-scale phenomena for different adhesion methods that can be employed in microrobots. These adhesion methods are applied to a sub-2 gram legged robot,...
Locomoting soft robots typically walk or crawl slowly relative to their rigid counterparts. In order to execute agile behaviors such as jumping, rapid actuation modes are required. Here we present an untethered soft-bodied robot that uses a combination of pneumatic and explosive actuators to execute directional jumping maneuvers. This robot can autonomously jump up to 0.6 meters laterally with an...
Transmission and actuator selection are crucial for robot locomotion at any scale. This is especially true at small scales where actuation choices are limited and locomotion is energetically expensive. These components control the payload capacity and determine the height of the obstacles the robot can navigate over. In this study, we analyze the drivetrain of the new Harvard Ambulatory MicroRobot...
Turning gaits and optimal undulatory straight-line gaits for a walking myriapod millirobot are presented. Simulation and experiments show that body undulations similar to those found in natural centipedes enhance straight-line locomotion via increased speeds and reduced cost of transport for myriapod millirobots with passively flexible bodies composed of a variety of segments. A simple turning strategy...
The design and modeling of a segmented myriapod millirobot with a compliant body is presented. A dynamic model is used to demonstrate how body undulations can result from only varying the phase difference in the stance change between adjacent segments - even with passive intersegmental connections - and how these gaits affect locomotion. Different gaits are demonstrated experimentally in a 20-leg,...
Here we present an autonomous 1.7g hexapod robot as a platform for research on centimeter-scale walking robots. It features six spherical five-bar linkages driven by high energy density piezoelectric actuators and onboard power and control electronics. This robot has achieved autonomous ambulation using an alternating tripod gait at speeds up to 0.9 body lengths per second, making this the smallest...
Large collections of robots have the potential to perform tasks collectively using distributed control algorithms. These algorithms require communication between robots to allow the robots to coordinate their behavior and act as a collective. In this paper we describe two algorithms which allow coordination between robots, but do not require physical environment marks such as pheromones. Instead,...
Here we present the design, modeling, and fabrication of a 2g mobile robot. By applying principles from biology and existing meso-scale fabrication techniques, a 5.7cm hexapod robot with sprawled posture has been created, and is capable of locomotion up to 4 body-lengths per second using the alternating tripod gait at 20Hz actuation frequency. Furthermore, this work proves the viability of a new mechanical...
The kinematic design of a multi-segment ambulatory microrobot inspired by centipedes is presented. The kinematics of five repeated segments joined by a flexible backbone of rigid links and flexures are described and simulated. The kinematic model was used to guide the design of an individual two degree of freedom segment, which was fabricated using the Smart Composite Microstructures process. Testing...
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