15 research outputs found
Design and FDM/FFF Implementation of a Compact Omnidirectional Wheel for a Mobile Robot and Assessment of ABS and PLA Printing Materials
This paper proposes the design and 3D printing of a compact omnidirectional wheel
optimized to create a small series of three-wheeled omnidirectional mobile robots. The omnidirectional
wheel proposed is based on the use of free-rotating passive wheels aligned transversally to the center
of the main wheel and with a constant separation gap. This paper compares a three inner-passive
wheels design based on mass-produced parts and 3D printed elements. The inner passive wheel that
better combines weight, cost, and friction is implemented with a metallic ball bearing fitted inside a
3D printed U-grooved ring that holds a soft toric joint. The proposed design has been implemented
using acrylonitrile butadiene styrene (ABS) and tough polylactic acid (PLA) as 3D printing materials
in order to empirically compare the deformation of the weakest parts of the mechanical design.
The conclusion is that the most critical parts of the omnidirectional wheel are less prone to deformation
and show better mechanical properties if they are printed horizontally (with the axes that hold the
passive wheels oriented parallel to the build surface), with an infill density of 100% and using tough
PLA rather than ABS as a 3D printing material
Assessing over Time Performance of an eNose Composed of 16 Single-Type MOX Gas Sensors Applied to Classify Two Volatiles
This paper assesses the over time performance of a custom electronic nose (eNose) composed of an array of commercial low-cost and single-type miniature metal-oxide (MOX) semiconductor gas sensors. The eNose uses 16 BME680 versatile sensor devices, each including an embedded
non-selective MOX gas sensor that was originally proposed to measure the total volatile organic
compounds (TVOC) in the air. This custom eNose has been used previously to detect ethanol and
acetone, obtaining initial promising classification results that worsened over time because of sensor
drift. The current paper assesses the over time performance of different classification methods applied
to process the information gathered from the eNose. The best classification results have been obtained
when applying a linear discriminant analysis (LDA) to the normalized conductance of the sensing
layer of the 16 MOX gas sensors available in the eNose. The LDA procedure by itself has reduced the
influence of drift in the classification performance of this single-type eNose during an evaluation
period of three month
The Assistant Personal Robot Project: From the APR-01 to the APR-02 Mobile Robot Prototypes
This paper describes the evolution of the Assistant Personal Robot (APR) project developed at the Robotics Laboratory of the University of Lleida, Spain. This paper describes the first APR-01 prototype developed, the basic hardware improvement, the specific anthropomorphic improvements, and the preference surveys conducted with engineering students from the same university in order to maximize the perceived affinity with the final APR-02 mobile robot prototype. The anthropomorphic improvements have covered the design of the arms, the implementation of the arm and symbolic hand, the selection of a face for the mobile robot, the selection of a neutral facial expression, the selection of an animation for the mouth, the application of proximity feedback, the application of gaze feedback, the use of arm gestures, the selection of the motion planning strategy, and the selection of the nominal translational velocity. The final conclusion is that the development of preference surveys during the implementation of the APR-02 prototype has greatly influenced its evolution and has contributed to increase the perceived affinity and social acceptability of the prototype, which is now ready to develop assistance applications in dynamic workspaces.This research was partially funded by the Accessibility Chair promoted by Indra, Adecco Foundation and the University of Lleida Foundation from 2006 to 2018. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results
Application of a Single-Type eNose to Discriminate the Brewed Aroma of One Caffeinated and Decaffeinated Encapsulated Espresso Coffee Type
This paper assesses a custom single-type electronic nose (eNose) applied to differentiate
the complex aromas generated by the caffeinated and decaffeinated versions of one encapsulated
espresso coffee mixture type. The eNose used is composed of 16 single-type (identical) metal–oxide
semiconductor (MOX) gas sensors based on microelectromechanical system (MEMS). This eNose
proposal takes advantage of the small but inherent sensing variability of MOX gas sensors in order to
provide a multisensorial description of volatiles or aromas. Results have shown that the information
provided with this eNose processed using LDA is able to successfully discriminate the complex
aromas of one caffeinated and decaffeinated encapsulated espresso coffee type
Classification of Three Volatiles Using a Single-Type eNose with Detailed Class-Map Visualization
The use of electronic noses (eNoses) as analysis tools are growing in popularity; however, the lack of a comprehensive, visual representation of how the different classes are organized and distributed largely complicates the interpretation of the classification results, thus reducing their practicality. The new contributions of this paper are the assessment of the multivariate classification performance of a custom, low-cost eNose composed of 16 single-type (identical) MOX gas sensors for the classification of three volatiles, along with a proposal to improve the visual interpretation of the classification results by means of generating a detailed 2D class-map representation based on the inverse of the orthogonal linear transformation obtained from a PCA and LDA analysis. The results showed that this single-type eNose implementation was able to perform multivariate classification, while the class-map visualization summarized the learned features and how these features may affect the performance of the classification, simplifying the interpretation and understanding of the eNose results
Classification of Two Volatiles Using an eNose Composed by an Array of 16 Single-Type Miniature Micro-Machined Metal-Oxide Gas Sensors
The artificial replication of an olfactory system is currently an open problem. The development of a portable and low-cost artificial olfactory system, also called electronic nose or eNose, is
usually based on the use of an array of different gas sensors types, sensitive to different target gases.
Low-cost Metal-Oxide semiconductor (MOX) gas sensors are widely used in such arrays. MOX sensors are based on a thin layer of silicon oxide with embedded heaters that can operate at different
temperature set points, which usually have the disadvantages of different volatile sensitivity in each
individual sensor unit and also different crossed sensitivity to different volatiles (unspecificity). This
paper presents and eNose composed by an array of 16 low-cost BME680 digital miniature sensors
embedding a miniature MOX gas sensor proposed to unspecifically evaluate air quality. In this paper, the inherent variability and unspecificity that must be expected from the 16 embedded MOX
gas sensors, combined with signal processing, are exploited to classify two target volatiles: ethanol
and acetone. The proposed eNose reads the resistance of the sensing layer of the 16 embedded MOX
gas sensors, applies PCA for dimensional reduction and k-NN for classification. The validation results have shown an instantaneous classification success higher than 94% two days after the calibration and higher than 70% two weeks after, so the majority classification of a sequence of
measures has been always successful in laboratory conditions. These first validation results and the
low-power consumption of the eNose (0.9 W) enables its future improvement and its use in portable
and battery-operated applications
Suboptimal Omnidirectional Wheel Design and Implementation
The optimal design of an omnidirectional wheel is usually focused on the minimization
of the gap between the free rollers of the wheel in order to minimize contact discontinuities with
the floor in order to minimize the generation of vibrations. However, in practice, a fast, tall, and
heavy-weighted mobile robot using optimal omnidirectional wheels may also need a suspension
system in order to reduce the presence of vibrations and oscillations in the upper part of the mobile
robot. This paper empirically evaluates whether a heavy-weighted omnidirectional mobile robot
can take advantage of its passive suspension system in order to also use non-optimal or suboptimal
omnidirectional wheels with a non-optimized inner gap. The main comparative advantages of the
proposed suboptimal omnidirectional wheel are its low manufacturing cost and the possibility of
taking advantage of the gap to operate outdoors. The experimental part of this paper compares the
vibrations generated by the motion system of a versatile mobile robot using optimal and suboptimal
omnidirectional wheels. The final conclusion is that a suboptimal wheel with a large gap produces
comparable on-board vibration patterns while maintaining the traction and increasing the grip on
non-perfect planar surfaces.This research was funded by the MCI program, grant number PID2020-118874RB-I00
Evaluation of the Path-Tracking Accuracy of a Three-Wheeled Omnidirectional Mobile Robot Designed as a Personal Assistant
This paper presents the empirical evaluation of the path-tracking accuracy of a three-wheeled omnidirectional mobile robot that is able to move in any direction while simultaneously changing its orientation. The mobile robot assessed in this paper includes a precise onboard LIDAR for obstacle avoidance, self-location and map creation, path-planning and path-tracking. This mobile robot has been used to develop several assistive services, but the accuracy of its path-tracking system has not been specifically evaluated until now. To this end, this paper describes the kinematics and path-planning procedure implemented in the mobile robot and empirically evaluates the accuracy of its path-tracking system that corrects the trajectory. In this paper, the information gathered by the LIDAR is registered to obtain the ground truth trajectory of the mobile robot in order to estimate the path-tracking accuracy of each experiment conducted. Circular and eight-shaped trajectories were assessed with different translational velocities. In general, the accuracy obtained in circular trajectories is within a short range, but the accuracy obtained in eight-shaped trajectories worsens as the velocity increases. In the case of the mobile robot moving at its nominal translational velocity, 0.3 m/s, the root mean square (RMS) displacement error was 0.032 m for the circular trajectory and 0.039 m for the eight-shaped trajectory; the absolute maximum displacement errors were 0.077 m and 0.088 m, with RMS errors in the angular orientation of 6.27° and 7.76°, respectively. Moreover, the external visual perception generated by these error levels is that the trajectory of the mobile robot is smooth, with a constant velocity and without perceiving trajectory corrections