Browsing by Subject "Legged robots"

Now showing 1 - 20 of 22

Open Access
Control of underactuated planar pronking through an embedded spring-mass Hopper template
(2011) Ankaralı, M.M.; Saranlı, U.
Autonomous use of legged robots in unstructured, outdoor settings requires dynamically dexterous behaviors to achieve sufficient speed and agility without overly complex and fragile mechanics and actuation. Among such behaviors is the relatively under-studied pronking (aka. stotting), a dynamic gait in which all legs are used in synchrony, usually resulting in relatively slow speeds but long flight phases and large jumping heights. Instantiations of this gait for robotic systems have been mostly limited to open-loop strategies, suffering from severe pitch instability for underactuated designs due to the lack of active feedback. However, both the kinematic simplicity of this gait and its dynamic nature suggest that the Spring-Loaded Inverted Pendulum model (SLIP) would be a good basis for the implementation of a more robust feedback controller for pronking. In this paper, we describe how template-based control, a controller structure based on the embedding of a simple dynamical "template" within a more complex "anchor" system, can be used to achieve very stable pronking for a planar, underactuated hexapod robot. In this context, high-level control of the gait is regulated through speed and height commands to the SLIP template, while the embedding controller ensures the stability of the remaining degrees of freedom. We use simulation studies to show that unlike existing open-loop alternatives, the resulting control structure provides explicit gait control authority and significant robustness against sensor and actuator noise. © 2010 Springer Science+Business Media, LLC.
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
Design, fabrication, and locomotion analysis of an untethered miniature soft quadruped, SQuad
(IEEE, 2020) Kalın, Mert Ali İhsan; Aygül, Cem; Türkmen, Altay; Kwiczak-Yiğitbaşı, Joanna; Baytekin, Bilge; Özcan, Onur
The conventional robotics, which involves utilization of robots made out of hard materials like metals and hard plastics, has helped humankind automate many different sorts of labor and such robots have been assisting the humans in various tasks. Nevertheless, some applications require very delicate interactions and adaptability of the robots to unstructured elements and obstacles; which can only be provided by softness. The miniature and untethered robot in this work is fully made out of soft structural materials and uses a flexible circuit board. Only the electronic components, actuators and several little connection parts are hard. Its soft legs, body, and circuit enables it to overcome obstacles that conventional hard miniature robots tend to be stopped by. For the soft robot presented, walking and obstacle climbing experiments were done and pitch angle, roll angle, robot's centroid position and stiffness analyses were conducted. Additionally, three other robots are fabricated in hard body - hard leg, hard body - soft leg, and soft body - hard leg configurations and the effects of body and leg compliance on the locomotion performance are investigated. The results show that a soft body - soft leg robot configuration can scale an obstacle 1.44 times its body height whereas the hard bodied and hard legged robot can only go over 0.88 times its body height. The results also indicate that the softness of the body effects the scalable obstacle height more than the softness of the legs at this length scale.
Open Access
Design, fabrication, and locomotion analysis of an untethered, miniature, legged, compressible, soft robot: CSQUAD
(2021-09) Kalın, Mert Ali İhsan
Conventional robotics has been eﬀective for industrial applications such as fast, precise and accurate production or for sophisticatedly controlled systems for the last couple of centuries. However, as the robots become more ubiquitous in every-day lives of people, the drawbacks of conventional and rigid robots have become more and more apparent. One of the biggest problems that soft robots solve is the safe interactions with humans. Whether it be a minimally invasive surgery or a search and rescue operation under rubble, the soft robots oﬀer better performance especially in terms of compliance compared to their rigid counterparts. With especially the search and rescue environments in mind, this study presents an untethered, miniature, legged and compressible soft quadruped (cSQuad). This robot is equipped with C-shaped legs for better locomotion per-formance on unstructured surfaces. It is made out of soft materials, mainly from polydimethylsiloxane (PDMS), it utilizes a ﬂexible printed circuit board (PCB) and only some small sensors, actuators and electronic components are made out of rigid materials. The main goal of this robot is to have the ability to pass through openings that are smaller than its cross-section. In order to achieve this goal, the robot is designed to be compressible. Both the body of the robot and its C-shaped legs can compress themselves using shape memory alloy (SMA) springs. The design and fabrication steps of cSQuad is explained in detail and the tests have been done to verify that the robot can reduce its cross-section area by at least 25%. cSQuad is the successor of SQuad which is also a soft quadruped with C-shaped legs. Before starting the design of cSQuad, the locomotion performance of SQuad was studied to make sure that it would be worth continuing to design new generation of soft quadrupeds. This study was a comparative study between the soft quadruped (SQuad) and its rigid and hybrid twins. The study consisted of speed, pitch and roll angle, body centroid position and obstacle climbing per-formance analysis. The results of this analyses showed that even though the soft robot was slower it gave better performance in terms of obstacle climbing and smooth locomotion. This gave us the conﬁdence to continue improving the robot which resulted in designing of cSQuad. SMA springs of cSQuad are placed on speciﬁcally calculated locations on the body and the legs of the robot to achieve optimum compression performance. To transmit power to the SMAs on continuously rotating legs, a custom slip-ring device was built utilizing pogo pins. The compression tests for the legs and the body were conducted separately. Then, a robot with both leg and body compression was built and tested. As a result, a robot with the capability of reducing its cross-section area by at least 25% is built and tested. This robot can be used as a base design for the new generation of robots that could be used in search and rescue operations. It has the potential to be equipped with speciﬁc sensors for speciﬁc tasks. The fabrication and design steps can also be considered as a framework for fabricating soft robots in general.
Open Access
Detecting scalable obstacles using soft sensors in the body of a compliant quadruped
(Institute of Electrical and Electronics Engineers, 2022-01-10) Özbek, Doğa; Yılmaz, Talip Batuhan; Kalın, Mert Ali İhsan; Şentürk, Kutay; Özcan, Onur
In soft robotics, one of the trending topics is using soft sensors to have feedback from the robot's body. This is not an easy process to accomplish since the sensors are often nonlinear, so researchers use different methods to generate information from data such as filters, machine learning algorithms, and optimization algorithms. In this paper, we show that, with good electronic and mechanical design, it is possible to use soft sensors for detecting obstacles and distinguishing the scalable obstacles. The demonstration is conducted with an untethered miniature, soft, C-legged robot, M–SQuad, the first modular C-legged quadruped consisting of three modules, which are connected by four soft sensors. In M–SQuad's body design, sensors are utilized as both sensing and structural elements. The modular design of the M–SQuad allows testing different sensor geometries and replacing the malfunctioning parts easily, without the need to refabricate the entire robot. A case study is introduced for demonstration of the robot's capability of detecting obstacles and distinguishing scalable obstacles in a parkour consisting of two obstacles with the heights of 20 mm and 150 mm, respectively. In the case study, M–SQuad can detect an obstacle during locomotion using the coil-spring shaped soft sensors in its body. Moreover, it can distinguish the obstacle is scalable or not after an initial climbing trial. If the obstacle is not scalable, the robot turns back.
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
Effect of feet failure and control uncertainties on the locomotion of multi-legged miniature robots
(Institute of Electrical and Electronics Engineers, 2022-03-09) Mahkam, Nima; Uğur, Mustafa; Özcan, Onur
This study investigates the effects of control uncertainties and random feet failures on the locomotion of the multi-legged miniature robots. The locomotion analyses results are verified with our modular multi-legged miniature robot with a soft/hybrid body named SMoLBot. A single SMoLBot module is 44.5 mm wide, 16.75 mm long, and 15 mm high with two individually actuated and controlled DC motors. This individual actuation makes it feasible to run with any imaginable gait, making SMoLBot a nice candidate for gait study analyses. The presented locomotion study shows that the effects of control uncertainties and feet failures are highly dependent on the total number of legs and the type of backbone attached to the robot, e.g., increasing the total number of legs or utilizing a rigid backbone on the robot helps the robot to walk faster compared to similar robots with soft backbones or the ones with fewer modules. This study presents a guide to the researchers on the effects of feet failures and control uncertainties on the locomotion of soft/hybrid multi-legged miniature robots.
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
Effects of compliance on path-tracking performance of a miniature robot
(IEEE - Institute of Electrical and Electronics Engineers, 2023-05-15) Uğur, Mustafa; Arslan, Burak; Özzeybek, Alperen; Özcan, Onur
Path-tracking is often challenging in miniature robots because their feet or wheels tend to slip due to the low robot weight. In this work, we investigate the effect of c-leg compliance on path-tracking performance and the obstacle-climbing capabilities of our foldable and miniature robot with soft, c-shaped legs. With its 82 mm x 60 mm x 29 mm size and 29.25 grams weight, a single module of our robot is one of the smallest untethered miniature robots. Our results show that utilizing soft c-shaped legs provides smooth path-tracking performance, similar to a wheeled differential drive robot. However, modules with rigid c-shaped legs are affected significantly by the impact and slip between the leg and the ground, and they perform rather unpredictably. Additionally, modules with wheels cannot climb obstacles 1 mm or larger. We show that using soft legs enhances the obstacle climbing skills of modules by climbing a 9 mm obstacle, while the module with rigid legs can only climb a 7 mm obstacle. These path-tracking abilities and obstacle-climbing capacity support our vision to build a reconfigurable robot using these modules.
Open Access
A framework for dynamic modeling of legged modular miniature robots with soft backbones
(Elsevier, 2021-06-29) Mahkam, Nima; Özcan, Onur
In 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.
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, Onur
The 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.
Open Access
Joint design and fabrication for multi-material soft/hybrid robots
(IEEE, 2019-04) Aygül, Cern; Kwiczak-Yiğitbaşı, Joanna; Baytekin, Bilge; Özcan, Onur
The 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.
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
Miniature modular legged robot with compliant backbones
(IEEE, 2020) Mahkam, Nima; Bakır, Alihan; Özcan, Onur
Soft Modular Legged Robot (SMoLBot) is a miniature, foldable, modular, soft-hybrid legged robot with compliant backbones. SMoLBot's body and locomotion mechanisms are folded out of acetate sheets and its compliant connection mechanisms are molded from Polydimethylsiloxane (PDMS). High maneuverability and smooth walking pattern can be achieved in miniature robots if high stiffness kinematic parts are connected with compliant components, providing the robot structural compliance and better adaptability to different surfaces. SMoLBot is exploiting features from origami-inspired robots and soft robots, such as low weight and low cost foldable rigid structures and adaptable soft connection mechanisms made out of PDMS. Each single module in SMoLBot is actuated and controlled by two separate DC motors. This enables gait modification and higher degree of freedom on controlling the motion and body undulation of the robot in turning and rough terrain locomotion. Each module has 44.5 mm width, 16.75 mm length and 15 mm height, which is approximately the same size with two DC motors and a LiPo battery. The comparisons between robots with compliant and rigid backbones demonstrate smoother walking pattern, and approximate decrease in body's roll angle from 12° to 6°, and pitch from 10° to 7°. The independent actuation and control over each leg in n number of modules make SMoLBot an ideal candidate for gait studies. Moreover, the possibility of changing the structural stiffness of the robot with different backbones enables such a compliant modular robot to be used for locomotion optimization studies in miniature scale.
Open Access
Neural network based estimator and controller for SLIP and TD-SLIP monopod robots
(2020-12) Öztürk, Ahmet Safa
Using spring loaded inverted pendulum models for legged locomotion, a wide range of applications can be developed for mobile robots. Spring loaded inverted pendulum model brings new challenges of solving the forward and inverse kinematic maps. Although exact solutions of SLIP model cannot be obtained analytically due to nonintegrability of stance dynamics, approximate analytical solutions are proposed to overcome these challenges in many of the previous studies. An alternative to approximate analytical solutions, neural network based forward and inverse kinematic map predictions can also be used. We used neural networks to design estimators and controllers, as forward and inverse kinematic map predictors. Required datasets are generated with existing simulations for spring loaded inverted pendulum models and datasets are constructed by including the determined inputs and outputs for the neural networks. Neural networks are designed by using different architectures and properties. Training results of estimators for predicting the goal state in the apex return map are reported for different configurations. Trained controllers are verified using the simulation and verified controllers are tested under the different run scenarios. By comparing all of the results, potential of the neural network based estimators and controllers is discussed.
Open Access
Quadrupedal bounding with an actuated spinal joint
(IEEE, 2011) Çulha, Utku; Saranlı, Uluç
Most legged vertebrates use flexible spines and supporting muscles to provide auxiliary power and dexterity for dynamic behaviors, resulting in higher speeds and additional maneuverability during locomotion. However, most existing legged robots capable of dynamic locomotion incorporate only a single rigid trunk with actuation limited to legs and associated joints. In this paper, we investigate how quadrupedal bounding can be achieved in the presence of an actuated spinal joint and characterize associated performance improvements compared to bounding with a rigid robot body. In the context of both a new controller structure for bounding with a body joint and existing bounding controllers for the rigid trunk, we use optimization methods to identify the highest performance gait parameters and establish that the spinal joint allows increased forward speeds and hopping heights. © 2011 IEEE.
Open Access
Reactive footstep planning for a planar spring mass hopper
(IEEE, 2009-10) Arslan, Ömür; Saranlı, Uluç; Morgül, Ömer
The main driving force behind research on legged robots has always been their potential for high performance locomotion on rough terrain and the outdoors. Nevertheless, most existing control algorithms for such robots either make rigid assumptions about their environments (e.g flat ground), or rely on kinematic planning at low speeds. Moreover, the traditional separation of planning from control often has negative impact on the robustness of the system against model uncertainty and environment noise. In this paper, we introduce a new method for dynamic, fully reactive footstep planning for a simplified planar spring-mass hopper, a frequently used model for running behaviors. Our approach is based on a careful characterization of the model dynamics and an associated deadbeat controller, used within a sequential composition framework. This yields a purely reactive controller with a very large, nearly global domain of attraction that requires no explicit replanning during execution. Finally, we use a simplified hopper in simulation to illustrate the performance of the planner under different rough terrain scenarios and show that it is extremely robust to both model uncertainty and measurement noise. © 2009 IEEE.
Open Access
Reactive planning and control of planar spring-mass running on rough terrain
(Institute of Electrical and Electronics Engineers, 2012) Arslan, Ö.; Saranlı, U.
An important motivation for work on legged robots has always been their potential for high-performance locomotion on rough terrain. Nevertheless, most existing control algorithms for such robots either make rigid assumptions about their environments or rely on kinematic planning at low speeds. Moreover, the traditional separation of planning from control often has negative impact on the robustness of the system. In this paper, we introduce a new method for dynamic, fully reactive footstep planning for a planar spring-mass hopper, based on a careful characterization of the model dynamics and the design of an associated deadbeat controller, used within a sequential composition framework. This yields a purely reactive controller with a large domain of attraction that requires no explicit replanning during execution. We show in simulation that plans constructed for a simplified dynamic model can successfully control locomotion of a more complete model across rough terrain. We also characterize the performance of the planner over rough terrain and show that it is robust against both model uncertainty and measurement noise without replanning. © 2012 IEEE.
Open Access
ReMBot: A reconfigurable, miniature, modular robot with soft connection mechanisms
(2023-07) Uğur, Mustafa
Nature 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.
Embargo
Smolbot-VS: a soft modular robot with variable stiffness backbones
(2024-09) Uygun, Muhammed
This 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.