Characterisation of Physiological Tremor using Multivariate Empirical Mode Decomposition and Hilbert Transform.

Fatigue-induced physiological tremor (FIPT) is undesirable when performing micromanipulation tasks that require high precision. It is important to characterise this form of tremor to aid in identifying and suppressing it from the intended micromanipulation task. Researchers have used surface electromyography (sEMG) and mechanomyography (MMG) separately or in combination to study tremor, which is further processed using Fourier transform-based techniques. The major drawback of using these techniques is that it assumes the signals are linear and stationary. On the contrary, Empirical Mode Decomposition (EMD) can provide localised information on energy of the non-linear and non-stationary signals at a particular time and frequency and hence is considered superior to the Fourier transform-based techniques when analysing signals like physiological tremor. This paper characterises physiological tremor by extracting the frequency band of interest using multivariate empirical mode decomposition (MEMD). The extracted frequency band is assessed using Hilbert spectral analysis for energy estimation. Energy Ratio (ER) is the parameter proposed in this study to indicate fatigue-induced physiological tremor. The linear regression of the ratio across task epoch (TE) showed an increasing trend with R2≈0.7 for sEMG signals and R2≈0.9 for accelerometer signals to indicate levels of fatigue increase.Clinical Relevance - This study presents an effective & versatile indicator of FIPT. The characterisation method discussed in this paper will form an integral part of creating control strategies that can eliminate undesired consequences of fatigue-induced tremor in prolonged surgical manipulation. In addition, in surgical training modules, it aids the learning rate of novice surgeons.

Real-time biodiversity analysis using deep-learning algorithms on mobile robotic platforms.

Ecological biodiversity is declining at an unprecedented rate. To combat such irreversible changes in natural ecosystems, biodiversity conservation initiatives are being conducted globally. However, the lack of a feasible methodology to quantify biodiversity in real-time and investigate population dynamics in spatiotemporal scales prevents the use of ecological data in environmental planning. Traditionally, ecological studies rely on the census of an animal population by the "capture, mark and recapture" technique. In this technique, human field workers manually count, tag and observe tagged individuals, making it time-consuming, expensive, and cumbersome to patrol the entire area. Recent research has also demonstrated the potential for inexpensive and accessible sensors for ecological data monitoring. However, stationary sensors collect localised data which is highly specific on the placement of the setup. In this research, we propose the methodology for biodiversity monitoring utilising state-of-the-art deep learning (DL) methods operating in real-time on sample payloads of mobile robots. Such trained DL algorithms demonstrate a mean average precision (mAP) of 90.51% in an average inference time of 67.62 milliseconds within 6,000 training epochs. We claim that the use of such mobile platform setups inferring real-time ecological data can help us achieve our goal of quick and effective biodiversity surveys. An experimental test payload is fabricated, and online as well as offline field surveys are conducted, validating the proposed methodology for species identification that can be further extended to geo-localisation of flora and fauna in any ecosystem.

Design and realization of a novel haptic graspable interface for augmenting touch sensations.

A novel haptic grasper that renders touch sensations to the user in 3-DoF (degrees of freedom), namely linear, rotary, and grasping motions, is presented. The touch sensations of the grasper include the combination of kinesthetic and tactile modalities such as stiffness, texture, and shape. The device is equipped with two swappable modular segments that provide stiffness and shape sensations. To increase the haptic fidelity, the textural surfaces that surround the outer surface of the segments are equipped with vibro-actuators underneath them. These vibro-actuators contribute to increasing the number of perceivable textures by varying amplitude, frequency, duration, and envelope of vibrations. The proposed device is characterized in terms of stiffness, shape and texture rendering capabilities. The experimental results validate the effectiveness of the developed haptic grasper in virtual/remote interactions. Also, the user studies and statistical analysis demonstrate that the users could perceive the high-fidelity haptic feedback with the unified sensations of kinesthetic and tactile cues.

Design, Analysis, and Testing of a Hybrid VTOL Tilt-Rotor UAV for Increased Endurance.

Unmanned Aerial Vehicles (UAVs) have slowly but steadily emerged as a research and commercial hotspot because of their widespread applications. Due to their agility, compact size, and ability to integrate multiple sensors, they are mostly sought for applications that require supplementing human effort in risky and monotonous missions. Despite all of these advantages, rotorcrafts, in general, are limited by their endurance and power-intensive flight requirements, which consequently affect the time of flight and operational range. On the other hand, fixed-wing aircrafts have an extended range, as the entire thrust force is along the direction of motion and are inherently more stable but are limited by their takeoff and landing strip requirements. One of the potential solutions to increase the endurance of VTOL rotorcrafts (Vertical Take-Off and Landing Vehicles) was to exploit the thrust vectoring ability of the individual actuators in multi-rotors, which would enable take-off and hovering as a VTOL vehicle and flight as a fixed-wing aircraft. The primary aim of this paper is to lay out the overall design process of a Hybrid VTOL tilt-rotor UAV from the initial conceptual sketch to the final fabricated prototype. The novelty of the design lies in achieving thrust vectoring capabilities in a fixed-wing platform with minimum actuation and no additional control complexity. This paper presents novel bi-copter that has been designed to perform as a hybrid configuration in both VTOL and fixed wing conditions with minimum actuators in comparison to existing designs. The unified dynamic modelling along with the approximation of multiple aerodynamic coefficients by numerical simulations is also presented. The overall conceptual design, dynamic modeling, computational simulation, and experimental analysis of the novel hybrid fixed-wing bi-copter with thrust vectoring capabilities aiming to substantially increase the flight range and endurance compared to the conventional aircraft rotorcraft configurations are presented.

Design of a tether-driven minimally invasive robotic surgical tool with decoupled degree-of-freedom wrist.

BACKGROUND: Dexterous surgical tool wrists used in tele-operated robotic surgery typically have mechanically coupled pitch and yaw degree of freedom (DoF). This leads to complex control requirements. MATERIALS AND METHODS: The design of a robotic surgical tool with a mechanically decoupled dexterous wrist which uses stationary tether guides to guide drive tethers is presented. The tethers are routed through the plane of symmetry of the tool and follow law of belting to mechanically decouple the wrist. An optimization procedure for the placement of the stationary tether guides to minimize the change in tether length is presented. RESULTS: Experimental and analytical results confirm the decoupled motion capability of the wrist. Also, the change in length of tether segments over the operating range of motion was found to be very small. CONCLUSION: A prototype has been fabricated through metal 3D printing and integrated to a tele-operated robotic setup to demonstrate its utility in surgical application.

Differential analysis of muscle fatigue induced elbow and wrist tremor in controlled laparoscopic manoeuvring.

BACKGROUND: Fatigue induced hand tremor (FIT) is a primary limiting concern for the prolonged surgical intervention in minimally invasive surgery (MIS) and robot-assisted-minimally invasive surgery (RAMIS). A thorough analysis is necessary to understand the FIT characteristics in laparoscopic tool movement. The primary aim of this study is to perform a differential analysis of the elbow and wrist tremor due to muscle fatigue in laparoscopic manoeuvring. METHODS: We have introduced a joint angle based tremor analysis method, which enables us to perform a differential study of FIT characteristics at the individual joint. Experimental data was acquired from a group of subjects during static and dynamic laparoscopic movement in an imitative RAMIS master manipulation scenario. A repetitive task was performed with a total span of 1 h for observing the effect of muscle fatigue. Along with the joint angle variation, surface electromyography (sEMG) signal was also studied in the analysis. RESULTS: The wrist tremor is more predominant than tremor generated at the elbow, especially in highly fatigued condition. The high-frequency tremor (>4 Hz) is contributed by the wrist joint. Moreover, the variation of the wrist and elbow tremor ratio was found to be dependent upon the experience of the surgeons. CONCLUSIONS: In this work, we have investigated the attribution of elbow and wrist joints in FIT during laparoscopic tool manipulation. The outcomes may be useful for the design of robot-assisted surgical manipulator, and can be used for quality assessment of surgical training as well.

Dominant component in muscle fatigue induced hand tremor during laparoscopic surgical manipulation.

Accuracy of laparoscopic surgery gets affected by the hand tremor of the surgeons. Though cognitive load is inevitable in such activity which promotes tremor, muscle fatigue induced tremor is significant among the most important sources of tremor. Characteristic of fatigue induced hand tremor and its dominant directional properties are reported in this work. For a fixed laparoscopic tool grip with temporally synchronized predefined task protocols, characteristics of fatigue induced tremors have been studied. Dominant component of tremor was found to be in the sagittal plane in case of both static and dynamic tasks. In order to relate it with the muscle fatigue level, spectral properties of surface electromyography (SEMG) were also investigated simultaneously. A study of transient effect on tool positioning was also included, which conjointly advocates the other experimental results on fatigue induced hand tremor as well.