Browsing by Subject "Miniature robots"
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Item Open Access C-Quad: a miniature, foldable quadruped with C-shaped compliant legs(IEEE, 2017) Güç, Ahmet Furkan; Kalın, Mert Ali İhsan; Karakadıoğlu, Cem; Özcan, OnurC-Quad is an origami-inspired, foldable, miniature robot whose legs and body are all machined from one PET sheet each. The already famous compliant legs are modified such that they can be manufactured from a flat PET sheet and folded into the C-shape wanted. The compliant legs enable the miniature robot to run fast and scale obstacles with ease due to the geometry of the legs. C-Quad has four legs that are manufactured separately from the main body frame, which is also manufactured from a single PET sheet. All of its legs are actuated individually with a total of four DC motors. Despite the thin PET film, the structural rigidity and robustness of the body frame is increased by using specialized folds and locks. The manufacturing and assembly of the robot takes approximately 2.5 hours. C-Quad carries a battery, an Arduino Pro Micro control board, a bluetooth communication module, custom made encoders and commercially available IR sensors for motor speed control and motor drivers, all of which weighs 38 grams. By using very simple control strategies, it can achieve the speed of 2.7 Bodylengths/sec, can perform in-place turns and can climb over obstacles more than half of its height.Item Open Access Control and study of bio-inspired quadrupedal gaits on an underactuated miniature robot(Institute of Physics, 2023-01-25) Askari, Mohammad; Uğur, Mustafa; Mahkam, Nima; Yeldan, Alper; Özcan, OnurThis paper presents a linear quadratic Gaussian (LQG) controller for controlling the gait of a miniature, foldable quadruped robot with individually actuated and controlled legs (MinIAQ-III). The controller is implemented on a palm-size robot made by folding an acetate sheet. MinIAQ-III has four DC motors for actuation and four rotary sensors for feedback. It is one of the few untethered robots on a miniature scale capable of working with different gaits with the help of its individually-actuated legs and the developed controller. The presented LQG controller controls each leg’s positions and rotational speeds by measuring the positions and estimating the rotational speeds, respectively. With the precise gait control on the robot, we demonstrate different gaits inspired by quadrupeds in nature and compare the simulation and experiment results for some of the gaits. An extensive simulation environment developed for robot dynamics helps us to predict the locomotion behavior of the robot in various environments. The match between the simulation and the experiment results shows that the proposed LQG controller can successfully control the miniature robot’s gaits. We also conduct a case study that shows the potential to use the simulation to achieve different robot behavior. In a case study, we present our robot performing a prancing similar to horses. We use the simulation environment to find the required motor configuration phases and physical parameters, which can make our robot prance. After finding the parameters in simulation, we replicate the configuration in our robot and observe the robot making the same moves as the simulation. © 2023 IOP Publishing Ltd.Item Open Access Design and operation of MinIAQ: an untethered foldable miniature quadruped with individually actuated legs(IEEE, 2017) Karakadıoğlu, Cem; Askari, Mohammad; Özcan, OnurThis paper presents the design, development, and basic operation of MinIAQ, an origami-inspired, foldable, untethered, miniature quadruped robot. Instead of employing multilayer composite structures similar to most microrobotic fabrication techniques, MinIAQ is fabricated from a single sheet of thin A4-sized PET film. Its legs are designed based on a simple four-bar locomotion mechanism that is embedded within its planar design. Each leg is actuated and controlled individually by separate DC motors enabling gait modification and higher degree of freedom on controlling the motion. The origami-inspired fabrication technique is a fast and inexpensive method to make complex 3D robotic structures through successive-folding of laser-machined sheets. However, there is still a need for improvement in modulating and extending the design standards of origami robots. In an effort to addressing this need, the primitive foldable design patterns of MinIAQ for higher structural integrity and rigidity are presented in detail. The current robot takes less than two hours to be cut and assembled and weighs about 23 grams where 3.5 grams is the weight of its body, 7.5 grams is its motors and encoders, 5 grams is its battery, and about 7 grams is its current on-board electronics and sensors. The robot is capable of running about 30 minutes on a single fully charged 150mAh single cell LiPo battery. Using the feedback signals from the custom encoders, MinIAQ can perform a trot gait with a speed of approximately 0.65 Bodylengths/sec, or equivalently 7.5 cm/s.Item Open Access Dynamic modeling and gait analysis for miniature robots in the absence of foot placement control(Institute of Electrical and Electronics Engineers Inc., 2019) Askari, Mohammad; Özcan, OnurThe study of animals and insects have led to realization that animals select their gaits, patterns of leg movement, according to speed. For proper gait planning, the legs must be controlled for proper foot placement with respect to the body motion and ground interactions. However, in small scale robotic platforms gait planning through foot placement control is neither cost effective nor easily attainable due to a lack of available sensors. Thus, even though a desired gait is envisioned at the design phase, it is not known whether the gait is optimum. In this work, we present the comprehensive dynamic model of the miniature foldable robot, MinIAQ-II, which has four independently actuated legs. Dynamic model is used to perform gait analysis, to investigate the difference between the intended gait and the achieved gait in the absence of foot placement control. The model is verified through slow speed walking experiments on flat terrain. The work presented can be modified for different miniature robots with passive legs to predict their locomotion under no foot placement control.Item Open Access The effect of large deflections of joints on foldable miniature robot dynamics(Springer, 2020) Karakadıoğlu, Cem; Askari, Mohammad; Özcan, OnurIn miniature robotics applications, compliant mechanisms are widely used because of their scalability. In addition, compliant mechanism architecture is compatible with the manufacturing methods used to fabricate small scale robots, such as “foldable robotics”, where the size and the materials used allow much larger deflections. In this paper, the kinematics of compliant mechanisms used in miniature foldable robots are investigated with the assumption of nonlinear large deflections that occur at the flexure joints. The solution of the large beam deflection is acquired using elliptic integrals and is verified with finite element analysis and experiments on a simple small foldable leg linkage. The large deflection model takes joint strain energies into account and yields accurate estimations for load capacity of the mechanism as well as the necessary input torque for actuation of the leg. Therefore, the model presented can be used to estimate the load capacity of a miniature robot, as well as to select appropriate actuators. The work is also extended to estimate the compliant leg kinematics and rigid body dynamics of a foldable robot. The robot’s large deflection simulation results are compared with experiments and a simplified rigid-link pin-joint kinematic model. Our results demonstrate the modeling accuracy of the two approaches and can be used by foldable robotics community when deciding on the strategy to choose for modeling their robots.Item Open Access A framework for dynamic modeling of legged modular miniature robots with soft backbones(Elsevier, 2021-06-29) Mahkam, Nima; Özcan, OnurIn this work, the dynamics of ”n” legged modular miniature robots with a soft body is modeled. The dynamic formulation is obtained using Newton–Euler formulation that depends on the contact parameters and the feet closed-chain kinematic analysis. The dynamic model determines the locomotion parameters of each module as an individual system as well as the dynamics of the whole robot in a 3D space; i.e., the robot is modeled as one system, and modules are considered to be sets of flexible links connected within this system. Kinematic constraints among these modules are obtained by considering the type of backbone integrated into the modular robot. Various types of backbones are used that are classified into three groups: rigid, only torsional, and soft. The model is verified using SMoLBot, an origami-inspired miniature robot made of multiple modules and soft/rigid backbones. Additional to the dynamic model, the effect of different sets of design parameters on the locomotion of the legged soft-bodied modular miniature robots is studied. Analyses comparing the velocity of SMoLBot with a different number of modules and various types of backbones are presented using the proposed dynamic model. Our results show the existence of an optimum backbone torsional stiffness for legged miniature modular robots and an optimum number of legs for a given backbone stiffness that maximizes the robot’s velocity. In this research, presented results and locomotion study show that the robot’s design should be iteratively improved based on specific optimum goals for exclusively defined task to satisfy the operational needs.Item Open Access Gait and locomotion analysis of a soft-hybrid multilegged modular miniature robot(Institute of Physics Publishing Ltd., 2021-09-28) Mahkam, Nima; Özcan, OnurThe locomotion performance of the current legged miniature robots remains inferior compared to even the most simple insects. The inferiority has led researchers to utilize biological principles and control in their designs, often resulting in improved performance and robot capabilities. Additionally, optimizing the locomotion patterns compatible with the robot's limitations (such as the gaits achievable by the robot) improves the performance significantly and results in a robot operating with its maximum capabilities. This paper studies the locomotion characteristics of running/walking n-legged modular miniature robots with soft or rigid module connections. The locomotion study is done using the presented dynamic model, and the results are verified using a legged modular miniature robot with soft and rigid backbones (SMoLBot). The optimum foot contact sequences for an n-legged robot with different compliance values between the modules are derived using the locomotion analyses and the dynamic and kinematic formulations. Our investigations determine unique optimum foot contact sequences for multi-legged robots with different body compliances and module numbers. Locomotion analyses of a multi-legged robot with different backbones operating with optimum gaits show two main motion characteristics; the rigid robots minimize the number of leg-ground contacts to increase velocity, whereas soft-backbone robots use a lift–jump–fall motion sequence to maximize the translational speeds. These two behaviors are similar between different soft-backbone and rigid-backbone robots; however, the optimal foot contact sequences are different and unpredictable.Item Open Access Joint design and fabrication for multi-material soft/hybrid robots(IEEE, 2019-04) Aygül, Cern; Kwiczak-Yiğitbaşı, Joanna; Baytekin, Bilge; Özcan, OnurThe premises of safer interactions with surroundings and the higher adaptability to its environment make soft robotics a very interesting research field. Some robots try to achieve these feats using soft materials in their designs whereas some achieve behavioral softness through compliant use of hard materials. In this work, we present soft/hybrid robot leg designs that utilize elastomers as leg materials but hard DC motors as actuators. Two different leg designs that would convert the rotational motion of the DC motors to a foot trajectory are proposed. The different leg designs are kinematically identical; however, the hourglass design utilizes geometrical modifications to differentiate joint locations, whereas the composite design uses materials with different Young's Moduli without geometrical effects to create joints. In order to fabricate the composite design, a new method is developed involving 3D printed molds with removable joint pieces and a two-step molding process. Both of the legs are fabricated and simulations and experiments are run to compare their performances. Both mechanisms achieve a good foot trajectory, however the hourglass joint experiences higher mechanical stress during operation, which might lead to earlier failure especially under high loads. Such multi-material structures made out of elastomers can be utilized in miniature robots or mechanisms of similar size in which absolute joint locations are needed and continuum robotic limbs are not preferred.Item Open Access MinIAQ-II: a miniature foldable quadruped with an improved leg mechanism(IEEE, 2018) Askari, Mohammad; Karakadıoǧlu, Cem; Ayhan, Furkan; Özcan, OnurOrigami 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.Item Open Access MiniCoRe: A miniature, foldable, collision resilient quadcopter(IEEE, 2020) Dilaveroğlu, Levent; Özcan, OnurCollision management strategies are an integral part of micro air vehicle (MAV) operation for flight sustainability. Among them, collision avoidance strategies require enhanced environmental and situational awareness for generating evasive maneuvers and collision-free trajectories. Simpler and more adaptable option is to prepare for collisions and design the physical system with predicted collision patterns in mind. In this work, a mechanically compliant quadcopter design using origami-inspired foldable robotics methods with protective shock absorbing elements has been proposed for a collision resilient quad-rotor MAV. 2D design of the foldable structure and the manufacturing process, including electronic hardware elements and software has been discussed. Our results show that in low speed collisions, the flight of the quadcopter is uninterrupted. The compliant quadcopter can continue flight after impact in near-hover conditions because of the reduction of impact forces due to the increased impact time.Item Open Access ReMBot: A reconfigurable, miniature, modular robot with soft connection mechanisms(2023-07) Uğur, MustafaNature has been a valuable source of inspiration for engineers, leading to the development of diverse materials, mechanisms, and algorithms that have enhanced human life. One fascinating idea borrowed from nature is the collaborative work of ant colonies. Ants work together to accomplish tasks that are impossible to achieve individually, such as constructing bridges by connecting to one another. Researchers have been motivated by such examples to create reconfigurable robots that can perform various exciting tasks, such as climbing stairs, crossing gaps, moving objects, and assisting in furniture building, by moving as separate modules and docking to each other using different connection mechanisms. However, the connection mechanism remains a challenge. Many of the existing designs re-quire an actuator or a driving circuit which makes the control harder and limits the robot’s motion. This thesis presents ReMBot: A self-reconfigurable, miniature, modular robot with a soft connection mechanism. The robot comprises multiple modules, each equipped with backbones featuring permanent magnets. Using permanent magnets offers reconfigurability without requiring additional power, actuation, or a driving circuit while enhancing the robot’s compliance. The modules, including the body, electronics, actuators, c-shaped soft legs, and backbones with magnets, weigh 29.43 grams and have 82 mm x 60 mm x 14.7 mm dimensions. These module specifications, combined with the whole system design, allow ReMBot modules to execute path-tracking tasks, dock and undock, and sense the connection between modules. Their ability to connect and maintain a longer structure enables the ReMBot to climb obstacles higher than itself. Soft c-shaped legs enable modules to dock successfully by ensuring successful path-tracking tasks while they help them to move in different terrains like gravel, sand, or grass. The modules’ miniature structure, ease of manufacture, and affordability make them a suitable option for multiple use cases. The robot’s wireless communication capability makes it a strong contender for surveillance in confined spaces like collapsed buildings and nuclear sites, large areas like farmlands, and even planetary exploration missions.Item Embargo Smolbot-VS: a soft modular robot with variable stiffness backbones(2024-09) Uygun, MuhammedThis thesis introduces a novel mobile modular C-legged robot featuring a variable stiffness mechanism. The robot’s capability to adjust the level of compliance is achieved through a tendon-driven actuation system typically found in continuum robots. This system, in conjunction with 3D-printed soft backbones, forms the core of the robot’s modular design. A significant contribution of this work lies in developing and controlling the variable stiffness mechanism for its integration into SMoLBot. The robot design, in particular the backbone design was iteratively refined through repeated case studies, enhancing the robot’s ability to sense obstacles and optimize stiffness quantification using data from conductive backbones. The research also examined the advantages of modulating backbone stiffness, particularly in improving the robot’s performance in uneven terrain in rigid and soft configurations. The work in the thesis is concluded by detailing the implementation of a PI stiffness controller that leverages voltage feedback from the backbones to adjust the robot’s stiffness to intermediate levels. This controller allows the robot to autonomously operate variable stiffness mechanisms while demonstrating another potential use of soft sensors for mobile robots. The cyclic load tests established a correlation between voltage data from the backbones and stiffness, with force and displacement measurements confirming the relation across different stiffness levels.