Browsing by Subject "Mobile robots"
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Item Open Access An analytical solution to the stance dynamics of passive spring-loaded inverted pendulum with damping(World Scientific, 2009-09) Ankaralı, M. M.; Arslan, Ömür; Saranlı, UluçThe Spring-Loaded Inverted Pendulum (SLIP) model has been established both as a very accurate descriptive tool as well as a good basis for the design and control of running robots. In particular, approximate analytic solutions to the otherwise non integrable dynamics of t his model provide principled ways in which gait controllers can be built, yielding invaluable insight into their stability properties. However, most existing work on the SLIP model completely disregards the effects of damping, which often cannot be neglected for physical robot platforms. In this paper, we introduce a new approximate analytical solution to the dynamics of this system that also takes into account viscous damping in the leg. We compare both the predictive performance of our approximation as well as the tracking performance of an associated deadbeat gait controller to similar existing methods in the literature and show t hat it significantly outperforms them in the presence of damping in the leg.Item Open Access Autonomous navigation of robotic units in mobile sensor network(2012) Nazlibilek, S.This work is motivated by the problem of detecting buried anti-tank and anti-personnel mines in roads or some border regions. The problem is tried to be solved by use of small mobile robotic sensors and their some abilities such as measurement of local fields, navigation around a region, communications with each other, and constituting team within a mission area. The aim of this work is to investigate the navigation problem for the team behavior of mobile sensors within a potential field available in a small-scale environment such as an indoor area or an outdoor region. The mobile sensor network here is a collection of robotic units with sensing capability of earth magnetic field anomalies. A new kind of positioning system is needed for their collective behavior. In this work, a new method of navigation is proposed as a local positioning system. It utilizes ultrasound and radio frequency information to determine the coordinates of the points inside the operational area. The method proposed here is compared with the ultra wideband ranging ping-pong method that is used widely in recent applications. A time division multiple access method is used for the communications among the mobile sensors. The results on the positioning methods together with several simulations and experimental works are given. It is shown that the positioning method utilizing ultrasound-radio frequency method can give fairly good results. © 2012 Elsevier Ltd. All rights reserved.Item Open Access Chemical concentration map building through bacterial foraging optimization based search algorithm by mobile robots(IEEE, 2010) Turduev, M.; Kırtay, Murat; Sousa P.; Gazi V.; Marques L.In this article we present implementation of Bacterial Foraging Optimization algorithm inspired search by multiple robots in an unknown area in order to find the region with highest chemical gas concentration as well as to build the chemical gas concentration map. The searching and map building tasks are accomplished by using mobile robots equipped with smart transducers for gas sensing called "KheNose". Robots perform the search autonomously via bacterial chemotactic behavior. Moreover, simultaneously the robots send their sensor readings of the chemical concentration and their position data to a remote computer (a base station), where the data is combined, interpolated, and filtered to form an real-time map of the chemical gas concentration in the environment. ©2010 IEEE.Item Open Access A comparative study of five algorithms for processing ultrasonic arc maps(Bilkent University, 2005) Kurt, ArdaIn this work, one newly proposed and four existing algorithms for processing ultrasonic arc maps are compared for map-building purposes. These algorithms are the directional maximum, Bayesian update, morphological processing, voting and thresholding, and arc-transversal median algorithm. The newly proposed method (directional maximum) has a basic consideration of the general direction of the mapped surface. Through the processing of arc maps, each method aims at overcoming the intrinsic angular uncertainty of ultrasonic sensors in map building, as well as eliminating noise and cross-talk related misreadings. The algorithms are implemented in computer simulations with two distinct motion-planning schemes for ground coverage, wall following and Voronoi diagram tracing. As success criteria of the methods, mean absolute difference with the actual map/profile, fill ratio, and computational cost in terms of CPU time are utilized. The directional maximum method performed superior to the existing algorithms in mean absolute error, was satisfactory in fill ratio and performed second best in processing times. The results indicate various trade-offs in the choice of algorithms for arc-map processing.Item Open Access A comparison of two methods for fusing information from a linear array of sonar sensors for obstacle localization(IEEE, 1995) Arıkan, Orhan; Barshan, BillurThe performance of a commonly employed linear array of sonar sensors is assessed for point-obstacle localization intended for robotics applications. Two different methods of combining time-of-flight information from the sensors are described to estimate the range and azimuth of the obstacle: pairwise estimate method and the maximum likelihood estimator. The variances of the methods are compared to the Cramer-Rao Lower Bound, and their biases are investigated. Simulation studies indicate that in estimating range, both methods perform comparably; in estimating azimuth, maximum likelihood estimate is superior at a cost of extra computation. The results are useful for target localization in mobile robotics.Item Open Access Design, characterization, and applications of soft 3D printed strain gauges(Bilkent University, 2023-07) Özbek, DoğaThe development of soft sensors for integration into untethered miniature robots is significant for improving their environmental perception in physically challenging scenarios, such as collapsed buildings after an earthquake. The primary objective is to design and manufacture reliable soft sensors that serve as structural and sensing elements within the robots, eliminating the need for post-processing methods like data-driven learning and optimization. The soft sensors employ resistive sensing, similar to strain gauges, and are implemented on a Wheatstone bridge to convert resistive changes into voltage changes under me-chanical actuation or deformation. The study explores two categories of soft sensor designs: sheet-type and 3D shaped sensors. Sheet-type sensors are embedded in the C-legs of a soft quadruped robot (SQuad), enabling gait control, while 3D shaped sensors are structurally integrated into the robots to enhance environmental perception. Manufacturing of the soft sensors is made accessible and efficient through 3D printing technology, using conductive Thermoplastic Polyurethane (cTPU) as the printing material. Challenges arise in integrating the soft sensors into the robots while preserving their soft nature, locomotion, and agility. The thesis addresses these challenges by implementing the soft sensor concept in various robots and their parts, including the C-leg of SQuad, Modular Soft Quadruped (M-SQuad), Suspensionized Soft Quadruped (S-SQuad), Sensorized Collision Resilient Robot (SCoReR), and a tail for Reconfigurable Miniature Modular Robot (ReMBot). The soft sensors enable different functionalities to these robots, such as gait control feedback, obstacle detection, inclination detection, and collision detection, enhancing the adaptability of the robots in physically challenging environments. The thesis highlights the potential of soft 3D printed strain gauges. The ease of manufacturing and cost-efficiency of these sensors make them promising for applications in wearable robots and human-computer interfaces. Future directions are highlighted, emphasizing the need for detailed sensor characterization experiments and the development of detection algorithms to improve reliability. Additionally, a dynamic model of the coil-shaped sensors is proposed to simulate resistance changes, streamlining the design process without repetitive manufacturing iterations. As a result, this thesis presents a reliable soft sensor design, manufacturing, and integration into untethered miniature robots. The outcome of this work demonstrates the effectiveness of soft sensors in enhancing environmental perception, paving the way for innovative solutions in force measurement applications and human-computer interactions.Item Restricted Design, fabrication, and locomotion analysis of an untethered, miniature, legged, compressible, soft robot: CSQUAD(Bilkent University, 2021-09) Kalın, Mert Ali İhsanConventional 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.Item Open Access Differentiation and localization of target primitives using infrared sensors(IEEE, 2002-09-10) Aytaç, Tayfun; Barshan, BillurThis study investigates the use of low-cost infrared sensors in the differentiation and localization of commonly encountered target primitives in indoor environments, such as planes, corners, edges, and cylinders. The intensity readings from such sensors are highly dependent on target location and properties in a way which cannot be represented in a simple manner, making the differentiation and localization process difficult. In this paper, we propose the use of angular intensity scans and present an algorithm to process them. This approach can determine the target type independent of its position. Once the target type is identified, its position can also be estimated. The method is verified experimentally. An average correct classification rate of 97% over all target types is achieved and targets are localized within absolute range and azimuth errors of 0.8 cm and 1.6°, respectively. The proposed method should facilitate the use of infrared sensors in mobile robot applications for differentiation and localization beyond their common usage as simple proximity sensors for object detection and collision avoidance.Item Open Access Evaluation of solid-state gyroscope for robotics applications(Institute of Electrical and Electronics Engineers, 1995-02) Barshan, B.; Durrant-Whyte, H. F.he evaluation of a low-cost solid-state gyroscope for robotics applications is described. An error model for the sensor is generated and included in a Kalman filter for estimating the orientation of a moving robot vehicle. Orientation eshation with the error model is compared to the performance when the error model is excluded from the system. The results demonstrate that without error compensation, the error in localization is between 5-15"/min but can be improved at least by a factor of 5 if an adequate error model is supplied. Like all inertial systems, the platform requires additional information from some absolute position-sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modeling of error sources, inertial sensors can provide valuable orientation information for mobile robot applications.Item Open Access Evidential logical sensing using multiple sonars for the identification of target primitives in a mobile robot's environment(IEEE, 1996) Ayrulu, Birsel; Barshan, Billur; Erkmen, İ.; Erkmen, A.Physical models are used to model reflections from target primitives commonly encountered in mobile robot applications. These targets are differentiated by employing a multi-transducer pulse/echo system which relies on both amplitude and time-of-flight (TOF) data in the feature fusion process, allowing more robust differentiation. Target features are generated as being evidentially tied to degrees of belief which are subsequently fused for multiple logical sonars at different geographical sites. This evidential approach helps to overcome the vulnerability of echo amplitude to noise and enables the modeling of non-parametric uncertainty. Feature data from multiple logical sensors are fused with Dempster-Shafer rule of combination to improve the performance of classification by reducing perception uncertainty. Using three sensing nodes, improvement in differentiation is between 20-40% without false decision, at the cost of additional computation. Simulation results are verified by experiments with a real sonar system. This evidential approach helps to overcome the vulnerability of the echo amplitude to noise and enables the modeling of non-parametric uncertainty in real time.Item Open Access A hybrid method for 6-DOF tracking of MRI-compatible robotic interventional devices(2006-05) Krieger, A.; Metzger, G.; Fichtinger, G.; Atalar, Ergin; Whitcomb L. L.This paper reports a novel hybrid method of tracking the position and orientation of robotic medical instruments within the imaging volume of a magnetic resonance imaging (MRI) system. The method utilizes two complementary measurement techniques: passive MRI fiducial markers and MRI-compatible joint encoding. This paper reports an experimental evaluation of the tracking accuracy of this system. The accuracy of this system compares favorably to that of a previously reported active tracking system. Moreover, the hybrid system is quickly and easily deployed on different MRI scanner systems. © 2006 IEEE.Item Open Access Inertial navigation systems for mobile robots(Institute of Electrical and Electronics Engineers, 1995-06) Barshan, B.; Durrant-Whyte, H. F.A low-cost solid-state inertial navigation system (INS) for mobile robotics applications is described. Error models for the inertial sensors are generated and included in an Extended Kalman Filter (EKF) for estimating the position and orientation of a moving robot vehicle. Two Merent solid-state gyroscopes have been evaluated for estimating the orientation of the robot. Performance of the gyroscopes with error models is compared to the performance when the error models are excluded from the system. The results demonstrate that without error compensation, the error in orientation is between 5-15"/min but can be improved at least by a factor of 5 if an adequate error model is supplied. Siar error models have been developed for each axis of a solid-state triaxial accelerometer and for a conducting-bubble tilt sensor which may also be used as a low-cost accelerometer. Linear position estimation with information from accelerometers and tilt sensors is more susceptible to errors due to the double integration process involved in estimating position. With the system described here, the position drift rate is 1-8 cds, depending on the frequency of acceleration changes. An integrated inertial platform consisting of three gyroscopes, a triaxial accelerometer and two tilt sensors is described. Results from tests of this platform on a large outdoor mobile robot system are described and compared to the results obtained from the robot's own radar-based guidance system. Like all inertial systems, the platform requires additional information from some absolute position-sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modeling of error sources, low-cost inertial sensing systems can provide valuable orientation and position information particularly for outdoor mobile robot applications.Item Open Access Kinect based intelligent wheelchair navigation with potential fields(IEEE, 2014) Özçelikörs, M.; Çoşkun, A.; Say, M. Girayhan; Yazici, A.; Yayan, U.; Akçakoca, M.Increasing elderly people population and people with disabilities constitute a huge demand for wheelchairs. Wheelchairs have an important role on improving the lives and mobilization of people with disabilities. Moreover, autonomous wheelchairs constitute a suitable research platform for academic and industrial researchers. In this study, Finite state machine (FSM) based high-level controller and Kinect based navigation algorithm have been developed for ATEKS (Intelligent Wheelchair) which has high-tech control mechanisms, low-cost sensors and open source software (ROS, GAZEBO, ANDROID). © 2014 IEEE.Item Open Access Location and curvature estimation of "spherical" targets using a flexible sonar configuration(IEEE, 1996) Barshan, BillurA novel, flexible, three-dimensional (3-D) multi-sensor sonar system is employed to localize the center of a spherical target and estimate its radius of curvature. The interesting limiting cases for the problem under study are the point and planar targets, both of which are important for the characterization of a mobile robot's environment. A noise model is developed based on real sonar data. An extended Kalman filter (EKF) which incorporates the developed noise model is employed as an estimation tool for optimal processing of the sensor data. Simulations and experimental results are provided for specularly reflecting cylindrical targets.Item Open Access Location and curvature estimation of spherical targets using multiple sonar time-of-flight measurements(Institute of Electrical and Electronics Engineers, 1999-12) Barshan, B.A novel, flexible, three-dimensional multisensor sonar system is described to localize the center of a generalized spherical target and estimate its radius of curvature. Point, line, and planar targets are included as limiting cases which are important for the characterization of a mobile robot's environment. Sensitivity analysis of the curvature estimate with respect to measurement errors and some of the system parameters is provided. The analysis is verified experimentally for specularly reflecting cylindrical and planar targets. Typical accuracies in range and azimuth are 0.17 mm and 0.1°, respectively. Accuracy of the curvature estimate depends on the target type and system parameters such as transducer separation and operating range.Item Open Access A modular real-time fieldbus architecture for mobile robotic platforms(Institute of Electrical and Electronics Engineers, 2011-03) Saranlı U.; Avcı, A.; Öztürk, M. C.The design and construction of complex and reconfigurable embedded systems such as small autonomous mobile robots is a challenging task that involves the selection, interfacing, and programming of a large number of sensors and actuators. Facilitating this tedious process requires modularity and extensibility both in hardware and software components. In this paper, we introduce the universal robot bus (URB), a real-time fieldbus architecture that facilitates rapid integration of heterogeneous sensor and actuator nodes to a central processing unit (CPU) while providing a software abstraction that eliminates complications arising from the lack of hardware homogeneity. Motivated by our primary application area of mobile robotics, URB is designed to be very lightweight and efficient, with real-time support for Recommended Standard (RS) 232 or universal serial bus connections to a central computer and inter-integrated circuit (I(2)C), controller area network, or RS485 bus connections to embedded nodes. It supports automatic synchronization of data acquisition across multiple nodes, provides high data bandwidth at low deterministic latencies, and includes flexible libraries for modular software development both for local nodes and the CPU. This paper describes the design of the URB architecture, provides a careful experimental characterization of its performance, and demonstrates its utility in the context of its deployment in a legged robot platform.Item Open Access Morphological surface profile extraction from multiple sonars(IEEE, 1998) Başkent, Deniz; Barshan, BillurThis paper presents a novel method for surface profile determination using multiple sensors. Our approach is based on morphological processing techniques to fuse the range data from multiple sensor returns in a manner that directly reveals the target surface profile. The method has the intrinsic ability of suppressing spurious readings due to noise, crosstalk, and higher-order reflections, as well as processing multiple reflections informatively. The algorithm is verified both by simulations and experiments in the laboratory by processing real sonar data obtained from a mobile robot. The results are compared to those obtained from a more accurate structured-light system, which is however more complex and expensive.Item Open Access Orientation estimate for mobile robots using gyroscopic information(IEEE, 1994) Barshan, Billur; Durrant-Whyte, H. F.An error model for a solid-state gyroscope developed in previous work is included in a Kalman filter for improving the orientation estimate of a mobile robot. Orientation measurement with the error model is compared to the performance when no error model is incorporated in the system. The results demonstrate that without error compensation, the error in localization is between 5-15°/min but can be improved by a factor of 5 to 7 if an adequate error model is supplied. Results from tests of this gyroscope on a large outdoor mobile robot system are described and compared to the results obtained from the robot's own radar-based guidance system. Like all inertial systems, the platform requires additional information from some absolute position sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modelling of error sources, low cost inertial devices can provide valuable orientation and position information particularly for outdoor mobile robot applications.Item Open Access Planar motion controller design for a modular mechatronic device with heading compensation(Elsevier, 2019) Ristevski, Stefan; Çakmakçı, MelihMechaCells are designed as closed, scalable and modular semi-autonomous devices that can be used alone or part of a pack. In this paper, we discuss a locomotion system that uses the reaction force produced by a rotating unbalance that moves in a spherical domain with a steering mechanism. In order to produce the precise motion capability, a multi-loop controller is developed. This controller uses a friction compensation algorithm based on the mathematical model of the locomotion system. To improve the accuracy of tracking, conventional LuGre friction estimation model is extended for rapid directional changes of the MechaCell during planar motion. The linear and rotational acceleration of the device is also included in controller calculations since it affects the locomotion force generated by the unbalanced mass. The resulting control system is validated both with simulations and experiments and the effectiveness of the extended model and the controller is verified. Our results show significant improvement when a detailed friction compensation observer is used in the controller that includes the effect of sudden steering changes for precise path following.Item Open Access Rule-based target differentiation and position estimation based on infrared intensity measurements(SPIE, 2003) Aytaç, T.; Barshan, B.This study investigates the use of low-cost infrared sensors in the differentiation and localization of target primitives commonly encountered in indoor environments, such as planes, corners, edges, and cylinders. The intensity readings from such sensors are highly dependent on target location and properties in a way that cannot be represented in a simple manner, making the differentiation and localization difficult. We propose the use of angular intensity scans from two infrared sensors and present a rule-based algorithm to process them. The method can achieve position-invariant target differentiation without relying on the absolute return signal intensities of the infrared sensors. The method is verified experimentally. Planes, 90-deg corners, 90-deg edges, and cylinders are differentiated with correct rates of 90%, 100%, 82.5%, and 92.5%, respectively. Targets are localized with average absolute range and azimuth errors of 0.55 cm and 1.03 deg. The demonstration shows that simple infrared sensors, when coupled with appropriate processing, can be used to extract a significantly greater amount of information than they are commonly employed for.