MinIAQ-II: A miniature foldable quadruped with an improved leg mechanism

Abstract

Origami has long been renowned as a simple yet creative form of art and its folding techniques have recently inspired advances in design and fabrication of miniature robots. In this work, we present the design and fabrication novelties, enhancements, and performance improvements on MinIAQ (Miniature Independently Actuated-legged Quadruped), an origami-inspired, foldable, miniature quadruped robot with individually actuated legs. The resulting robot, MinIAQ-II, has a trajectory-optimized leg actuation mechanism with longer stride, improved traction, less flexure joint bending, and smaller leg lift resulting in faster and smoother walking, better maneuverability, and higher durability and joint life. In order to maximize the joint fatigue life while keeping the leg design simple, the initial four-bar mechanism is optimized by manipulating the joint locations and changing the leg link into a non-straight knee shape with a fixed-angle lock. Despite having a 1 cm longer frame to embed its new actuation mechanism, the overall weight and dimensions are similar to its first version as its legs are no longer extended beyond its frame. As a result, MinIAQ-II is 12-cm-long, 6-cm-wide, 4.5-cm-high and weighs 23 grams. The test results demonstrate the improvement in speed over its predecessor from 0.65 to more than 0.8 bodylengths/s at 3 Hz, and an approximate decrease in body's roll ±21 • to ±9 • and pitch from 0 • -11 • to 0 • -7 • . The independent actuation and control over each leg enables such a robot to be used for gait studies in miniature scale, as is the next direction in our research.

Miniature Modular Legged Robot With Compliant Backbones

“…Steps 1, 2 and 5 are executed only once in the beginning and their outputs are stored in the main code, remaining steps are continuously executed in each loop for controlling purposes. A PID controller similar to [29] is used to control the motor positions. Reference tracking of two motors with 0 and 180 • phase (trot gait) can be seen in Fig.…”

Dynamic Modeling and Gait Analysis for Miniature Robots in the Absence of Foot Placement Control

“…MinIAQ-II (see Fig. 1) is an origami-inspired foldable robot that is cut and folded from a single A4 size cellulose acetate sheet [7]. The motors used in the robot do not have any feedback sensors attached.…”

“…Therefore, the crank angle (θ 2 ) of each leg is defined as a function of time (t), the constant angular speed of the motor (ω 2 ), and an initial phase (β 0 ) corresponding to the desired gait phase offset between the legs. For a set of input crank angles at any given time, the solution to kinematic position analysis of the fourbar, previously reported in [7], yields planar coordinates of the joints on each leg. These planar coordinates can simply be turned into 3D position vectors representing the spatial coordinates of the joints with respect to the body-attached frame (see Fig.…”

“…The second version of our robot, miniature quadruped with individually-actuated legs (MinIAQ-II) is designed with independent leg actuation to study locomotion under different gaits on a small robotic platform. [7].…”

Joint Design and Fabrication for Multi-Material Soft/Hybrid Robots

“…1. The miniature robot design is modified from another work conducted in our lab, MinIAQ-II, a miniature foldable quadruped with individually actuated legs [15]. In this, soft/hybrid robot version, the kinematic design of the robot is kept, however the limitations on further miniaturization of the robot is eliminated by replacing the origami-inspired folding techniques used on acetate sheets with molding of soft materials to achieve a very similar mechanism design.…”