Browsing by Subject "Foldable robots"

Now showing 1 - 5 of 5

Open Access
Design and operation of MinIAQ: an untethered foldable miniature quadruped with individually actuated legs
(IEEE, 2017) Karakadıoğlu, Cem; Askari, Mohammad; Özcan, Onur
This 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.
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, Onur
The 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.
Open Access
The effect of large deflections of joints on foldable miniature robot dynamics
(Springer, 2020) Karakadıoğlu, Cem; Askari, Mohammad; Özcan, Onur
In 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.
Open Access
MinIAQ-II: a miniature foldable quadruped with an improved leg mechanism
(IEEE, 2018) Askari, Mohammad; Karakadıoǧlu, Cem; Ayhan, Furkan; Özcan, Onur
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.
Open Access
SCoReR: sensorized collision resilient aerial robot
(IEEE - Institute of Electrical and Electronics Engineers, 2023-05-15) Bakır, Alihan; Özbek, Doğa; Abazari, Amirali; Özcan, Onur
Detection and control of the physical contact/impact between micro aerial vehicles and the surrounding obstacles have become a significant issue with the rapid growth of their use in inspection and mapping missions in confined, obstacle-cluttered environments. In this work, we introduce a collision-resilient compliant micro quadcopter equipped with soft coil-spring type force sensors to passively resist and detect the physical contact/impact of the drone. The sensors act as resistive elements with a nominal resistance of 130–150 kΩ. They are manufactured from a conductive material via FDM 3D printing. We install these sensors on the protective bumpers of the collision-resilient foldable body of the drone. Any contact/impact between the bumpers and an obstacle results in deformation and buckling of the soft sensors, which results in a drastic change in their resistance, making it possible to detect the contacts/impacts of the bumpers. With a total weight of 220g and dimensions of 22cmx22cmx9cm, SCoReR successfully detects and recovers 100% of the contacts/impacts when it approaches a rigid wall with a velocity in the range of [0.1-1] m/s.