Inspired by the morphology characteristics of the earthworms and the excellent deformability of origami structures, this research creates a novel earthworm-like locomotion robot through exploiting ...the origami techniques. In this innovation, appropriate actuation mechanisms are incorporated with origami ball structures into the earthworm-like robot 'body', and the earthworm's locomotion mechanism is mimicked to develop a gait generator as the robot 'centralized controller'. The origami ball, which is a periodic repetition of waterbomb units, could output significant bidirectional (axial and radial) deformations in an antagonistic way similar to the earthworm's body segment. Such bidirectional deformability can be strategically programmed by designing the number of constituent units. Experiments also indicate that the origami ball possesses two outstanding mechanical properties that are beneficial to robot development: one is the structural multistability in the axil direction that could contribute to the robot control implementation; and the other is the structural compliance in the radial direction that would increase the robot robustness and applicability. To validate the origami-based innovation, this research designs and constructs three robot segments based on different axial actuators: DC-motor, shape-memory-alloy springs, and pneumatic balloon. Performance evaluations reveal their merits and limitations, and to prove the concept, the DC-motor actuation is selected for building a six-segment robot prototype. Learning from earthworms' fundamental locomotion mechanism-retrograde peristalsis wave, seven gaits are automatically generated; controlled by which, the robot could achieve effective locomotion with qualitatively different modes and a wide range of average speeds. The outcomes of this research could lead to the development of origami locomotion robots with low fabrication costs, high customizability, light weight, good scalability, and excellent re-configurability.
The goal of this research is to develop a generic earthworm-like locomotion robot model consisting of a large number of segments in series and based on which to systematically investigate the ...generation of planar locomotion gaits and their correlation with a robot’s locomotion performance. The investigation advances the state-of-the-art by addressing some fundamental but largely unaddressed issues in the field. These issues include (a) how to extract the main shape and deformation characteristics of the earthworm’s body and build a generic model, (b) how to coordinate the deformations of different segments such that steady-state planar locomotion can be achieved, and (c) how different locomotion gaits would qualitatively and quantitatively affect the robot’s locomotion performance, and how to evaluate them. Learning from earthworms’ unique morphology characteristics, a generic kinematic model of earthworm-like metameric locomotion robots is developed. Left/right-contracted segments are introduced into the model to achieve planar locomotion. Then, this paper proposes a gait-generation algorithm by mimicking the earthworm’s retrograde peristalsis wave, with which all admissible locomotion gaits can be constructed. We discover that when controlled by different gaits, the robot would exhibit four qualitatively different locomotion modes, namely, rectilinear, sidewinding, circular, and cycloid locomotion. For each mode, kinematic indexes are defined and examined to characterize their locomotion performances. For verification, a proof-of-concept robot hardware is designed and prototyped. Experiments reveal that with the proposed robot model and the employed gait controls, locomotion of different modes can be effectively achieved, and they agree well with the theoretical predictions.
Earthworm-like locomotion robots have great potential for applications in areas such as pipeline inspection and disaster rescue. The vibration-driven mechanism, due to its simplicity in design and ...ease of miniaturization, is promising to be employed in earthworm-like robot development. Note that the coordination of actuation and the connection between adjacent robot modules play an important role in determining locomotion performance. In this paper, without applying any prerequisite and aiming at improving locomotion performance, we investigate the coordination of the actuation phases in a multi-module vibration-driven robot with linear or nonlinear connections, thereby advancing the current state of the art. Specifically, the optimal phase-difference coordination pattern corresponding to the maximal average steady-state velocity is sought via the particle swarm optimization algorithm. For an
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-module vibration-driven robot with linear connections and working around the resonant frequencies, we discover that the optimal phase differences between adjacent modules can be determined based on their relative position relationship in the corresponding mode shape. For an
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-module vibration-driven locomotion robot with nonlinear connections, the identical-phase-difference pattern is preferred in implementation because it not only reduces the number of independent phase-difference variables to one, but also achieves an average steady-state velocity very close to the maximum. Moreover, dynamic analysis shows that the bent frequency–response curve caused by the cubic nonlinearity can substantially improve the maximum average steady-state velocity level of the robot while acquiring the unique merits of multiple locomotion modes and broadband characteristics. The findings of this paper would provide useful guidelines for the design and control of earthworm-like vibration-driven robots.
Although earthworms are recognized for their excellent mobility in confined environments, little is known about the triaxial ground reaction forces (GRFs) they produce during locomotion. This study ...explores the triaxial GRF characteristics of the earthworm during rectilinear locomotion and their implications for robot development. A strain gauge-based triaxial miniature force plate is designed to measure the triaxial GRFs of
Pheretima guillelmi
during rectilinear locomotion. By correlating the time histories of the measured GRFs with recorded videos, the motion of one cycle of the earthworm is divided into three phases, and the relationship between the deformation of the earthworm’s body and the characteristics of the GRFs is established. Based on the experimental data of nine subjects, this study also statistically analyzes the characteristics of the GRFs and derives a model of the earthworm’s resistance coefficient during its rectilinear motion. Furthermore, this study presents models of resistance coefficients closely related to robot segment/section deformations for both discrete and continuous configurations of earthworm-like robots. The results of this study are instructive for understanding earthworm locomotion biomechanics and designing and regulating the interface between the earthworm-like robot and the ground.
The average velocity and the backward velocity are two critical factors to evaluate the locomotion performance of a vibration-driven robot. These two factors are often antagonistic when the ground ...friction is isotropic and, consequently, lead to a bi-objective optimization. The goal of this paper is to give a practicable bi-objective optimization scheme for vibration-driven locomotion robots. To this end, a generalized dynamic model of the multi-module vibration-driven locomotion robot is built by assuming that the ground friction is isotropic Coulomb type and the driving force is ideal. The non-dominated sorting genetic algorithm II (NSGA-II) is then employed to construct the optimization scheme and then obtain the Pareto front. A numerical example with a two-module vibration-driven system is provided to demonstrate the necessity and effectiveness of applying the bi-objective optimization method. A robot prototype is further designed, and a series of experimental tests are carried out. By choosing the motors’ rotary speed and phase shift as optimization parameters, the average and backward velocities are extracted to check against the Pareto front. The consistency between the theoretical predictions and the experimental results shows the practicability of the proposed bi-objective optimization scheme. Therefore, the proposed optimization scheme will provide comprehensive guidance for system design and optimization in micro-locomotion robots.
Squamous cell carcinoma is a common form of lung cancer, the leading cause of cancer deaths in the world. Identifying early stage lung squamous cell carcinoma patients who would benefit most from ...effective therapies will reduce the mortality. We have previously shown that microRNAs (miRNAs) were stably present in sputum and potentially useful in diagnosis of lung cancer. The objective of this study was to develop a panel of miRNAs that can be used as a sputum-based test for early stage squamous cell carcinoma of the lungs. This study contained three phases: (1) marker discovery by profiling miRNA expression signatures on 15 lung squamous cell carcinoma and matched normal lung tissue samples with GeneChip miRNA Array; (2) marker optimization by real-time quantitative RT-PCR on sputum of a case-control cohort of 48 stage I lung squamous cell carcinoma patients and 48 healthy individuals; and (3) marker validation on an independent set including 67 lung squamous cell carcinoma patients and 55 healthy subjects. On the surgical tissues, six miRNAs were identified, of which three were overexpressed and three were underexpressed in all 15 tumors. On the sputum samples of the case-control cohort, three (miR-205, miR-210 and miR-708) of the six miRNAs were selected, which in combination produced the best prediction in distinguishing lung squamous cell carcinoma patients from normal subjects with 73% sensitivity and 96% specificity. Validation of the marker panel in the independent populations confirmed the sensitivity and specificity that provided a significant improvement over any single one alone. The sputum markers showed the potential to improve the early detection of lung squamous cell carcinomas.
Annelids such as earthworms are considered to have central pattern generators (CPGs) that generate rhythms in neural circuits to coordinate the deformation of body segments for effective locomotion. ...At present, the states of earthworm‐like robot segments are often assigned holistically and artificially by mimicking the earthworms’ retrograde peristalsis wave, which is unable to adapt their gaits for variable environments and tasks. This motivates the authors to extend the bioinspired research from morphology to neurobiology by mimicking the CPG to build a versatile framework for spontaneous motion control. Here, the spatiotemporal dynamics is exploited from the coupled Hopf oscillators to not only unify the two existing gait generators for restoring temporal‐symmetric phase‐coordinated gaits and discrete gaits but also generate novel temporal‐asymmetric phase‐coordinated gaits. Theoretical and experimental tests consistently confirm that the introduction of temporal asymmetry improves the robot's locomotion performance. The CPG‐based controller also enables seamless online switching of locomotion gaits to avoid abrupt changes, sharp stops, and starts, thus improving the robot's adaptability in variable working scenarios.
This work pioneers neurobiologically inspired control in metameric worm‐like robots. A generic, biologically plausible, versatile, and strongly adaptable control framework for metameric earthworm‐like robots is established to achieve polymorphism and better performance in metameric robotic locomotion. Seamless and smooth online switching of earthworm‐like robotic locomotion gaits is also realized to avoid abrupt changes and sharp stops or starts.
Non-small-cell lung cancer (NSCLC) is the leading cause of cancer-related death. Developing minimally invasive techniques that can diagnose NSCLC, particularly at an early stage, may improve its ...outcome. Using microarray platforms, we previously identified 12 microRNAs (miRNAs) the aberrant expressions of which in primary lung tumors are associated with early-stage NSCLC. Here, we extend our previous research by investigating whether the miRNAs could be used as potential plasma biomarkers for NSCLC. We initially validated expressions of the miRNAs in paired lung tumor tissues and plasma specimens from 28 stage I NSCLC patients by real-time quantitative reverse transcription PCR, and then evaluated diagnostic value of the plasma miRNAs in a cohort of 58 NSCLC patients and 29 healthy individuals. The altered miRNA expressions were reproducibly confirmed in the tumor tissues. The miRNAs were stably present and reliably measurable in plasma. Of the 12 miRNAs, five displayed significant concordance of the expression levels in plasma and the corresponding tumor tissues (all r>0.850, all P<0.05). A logistic regression model with the best prediction was defined on the basis of the four genes (miRNA-21, -126, -210, and 486-5p), yielding 86.22% sensitivity and 96.55% specificity in distinguishing NSCLC patients from the healthy controls. Furthermore, the panel of miRNAs produced 73.33% sensitivity and 96.55% specificity in identifying stage I NSCLC patients. In addition, the genes have higher sensitivity (91.67%) in diagnosis of lung adenocarcinomas compared with squamous cell carcinomas (82.35%) (P<0.05). Altered expressions of the miRNAs in plasma would provide potential blood-based biomarkers for NSCLC.
Adenocarcinoma is the most common type of lung cancer, the leading cause of cancer deaths in the world. Early detection is the key to improve the survival of lung adenocarcinoma patients. We have ...previously shown that microRNAs (miRNAs) were stably present in sputum and could be applied to diagnosis of lung cancer. The aim of our study was to develop a panel of miRNAs that can be used as highly sensitive and specific sputum markers for early detection of lung adenocarcinoma. Our study contained 3 phases: (i) marker discovery using miRNA profiling on paired normal and tumor lung tissues from 20 patients with lung adenocarcinoma; (ii) marker optimization by real‐time reverse transcription‐quantitative polymerase chain reaction on sputum of a case–control cohort consisting of 36 cancer patients and 36 health individuals and (iii) validation on an independent set of 64 lung cancer patients and 58 cancer‐free subjects. From the surgical tissues, 7 miRNAs with significantly altered expression were identified, of which “4” were overexpressed and “3” were underexpressed in all 20 tumors. On the sputum samples of the case–control cohort, 4 (miR‐21, miR‐486, miR‐375 and miR‐200b) of the 7 miRNAs were selected, which in combination produced the best prediction in distinguishing lung adenocarcinoma patients from normal subjects with 80.6% sensitivity and 91.7% specificity. Validation of the marker panel in the independent populations confirmed the sensitivity and specificity that provided a significant improvement over any single one alone. The sputum markers demonstrated the potential of translation to laboratory settings for improving the early detection of lung adenocarcinoma.
Trajectory planning of the knee joint plays an essential role in controlling the lower limb prosthesis. Nowadays, the idea of mapping the trajectory of the healthy limb to the motion trajectory of ...the prosthetic joint has begun to emerge. However, establishing a simple and intuitive coordination mapping is still challenging. This paper employs the method of experimental data mining to explore such a coordination mapping. The coordination indexes, i.e., the mean absolute relative phase (MARP) and the deviation phase (DP), are obtained from experimental data. Statistical results covering different subjects indicate that the hip motion possesses a stable phase difference with the knee, inspiring us to construct a hip-knee Motion-Lagged Coordination Mapping (MLCM). The MLCM first introduces a time lag to the hip motion to avoid conventional integral or differential calculations. The model in polynomials, which is proved more efficient than Gaussian process regression and neural network learning, is then constructed to represent the mapping from the lagged hip motion to the knee motion. In addition, a strong linear correlation between hip-knee MARP and hip-knee motion lag is discovered for the first time. By using the MLCM, one can generate the knee trajectory for the prosthesis control only via the hip motion of the healthy limb, indicating less sensing and better robustness. Numerical simulations show that the prosthesis can achieve normal gaits at different walking speeds.
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