Towards Scalable Strain Gauge-Based Joint Torque Sensors

During recent decades, strain gauge-based joint torque sensors have been commonly used to provide high-fidelity torque measurements in robotics. Although measurement of joint torque/force is often required in engineering research and development, the gluing and wiring of strain gauges used as torque sensors pose difficulties during integration within the restricted space available in small joints. The problem is compounded by the need for a scalable geometric design to measure joint torque. In this communication, we describe a novel design of a strain gauge-based mono-axial torque sensor referred to as square-cut torque sensor (SCTS), the significant features of which are high degree of linearity, symmetry, and high scalability in terms of both size and measuring range. Most importantly, SCTS provides easy access for gluing and wiring of the strain gauges on sensor surface despite the limited available space. We demonstrated that the SCTS was better in terms of symmetry (clockwise and counterclockwise rotation) and more linear. These capabilities have been shown through finite element modeling (ANSYS) confirmed by observed data obtained by load testing experiments. The high performance of SCTS was confirmed by studies involving changes in size, material and/or wings width and thickness. Finally, we demonstrated that the SCTS can be successfully implementation inside the hip joints of miniaturized hydraulically actuated quadruped robot-MiniHyQ. This communication is based on work presented at the 18th International Conference on Climbing and Walking Robots (CLAWAR)

A lightweight, high strength dexterous manipulator for commercial applications

The concept, design, and features are described of a lightweight, high strength, modular robot manipulator being developed for space and commercial applications. The manipulator has seven fully active degrees of freedom and is fully operational in 1 G. Each of the seven joints incorporates a unique drivetrain design which provides zero backlash operation, is insensitive to wear, and is single fault tolerant to motor or servo amplifier failure. Feedback sensors provide position, velocity, torque, and motor winding temperature information at each joint. This sensing system is also designed to be single fault tolerant. The manipulator consists of five modules (not including gripper). These modules join via simple quick-disconnect couplings and self-mating connectors which allow rapid assembly and/or disassembly for reconfiguration, transport, or servicing. The manipulator is a completely enclosed assembly, with no exposed components or wires. Although the initial prototype will not be space qualified, the design is well suited to meeting space requirements. The control system provides dexterous motion by controlling the endpoint location and arm pose simultaneously. Potential applications are discussed

Вимірювання крутного моменту для дослідження енергетичних характеристик приводів електромобілей

Purpose. Development of a torque measuring unit as part of a laboratory complex for studying the energy characteristics of electric drives for the purpose of mathematical modeling of the dynamic operating modes of an electric vehicle drive. Research methods. Physical experiment, regression analysis, interpolation. Findings. A torque measuring unit has been developed as part of a laboratory complex for studying the energy characteristics of electric vehicle drives, the design of which allows creating a torque on the shaft of the engine under study using a load and measuring it with a strain gauge force sensor. The laboratory stand together with the developed torque measuring unit corresponds to the required range and measurement accuracy. The experimental data obtained at the test bench make it possible to determine the dependence of the energy consumed by the drive on the mechanical power on the shaft of the engine under study, which makes it possible to analytically describe the drive under study and carry out mathematical modeling in the context of studying the influence of mechanical parameters on the consumed energy in dynamic modes of operation. Originality. A method for measuring torque on the motor shaft for studying the energy characteristics of electric vehicle drives has been developed. This method is based on the contact method of measurement, which uses 2 motors (loading and testing) and strain gauge force sensor and differs from others in the design that creates a moment on the shaft of the test motor.The result of processing the experimental data obtained by this method is the analytical dependence of the energy consumed by the drive on the value of the mechanical power on the shaft, the parameters of which are the angular speed and torque of the engine. The specified energy characteristic of the drive makes it possible, by means of mathematical modeling, to determine the electromechanical parameters of the drive, minimizing its energy consumption in dynamic modes of operation. Practical value. A method for measuring the moment on the motor shaft is proposed, with the help of which the dependence of the energy consumed by the drive on the mechanical power on the motor shaft is determined in an analytical form, which allows by mathematical modeling to find the electromechanical parameters of the system that increase the energy efficiency of the drive of an electric vehicle.Цель работы. Разработка узла измерения крутящего момента в составе лабораторного комплекса для исследования энергетических характеристик электроприводов с целью математического моделирования динамических режимов работ привода электрического транспортного средства. Методы иссследования. Физический эксперимент, регрессионный анализ, интерполяция. Полученные результати. Разработан узел измерения крутящего момента в составе лабораторного комплекса исследования энергетических характеристик приводов электрических транспортных средств, конструкция которого позволяет создавать крутящий момент на валу исследуемого двигателя с помощью нагрузочного и измерять его тензометрическим датчиком силы. Лабораторный стенд совместо с разработанным узлом измерения момента соответствует требуемому диапазону и точности измерений. Полученные на стенде экспериментальные данные позволяют определить зависимость потребляемой приводом энергии от механической мощности на валу исследуемого двигателя, что дает возможность аналитически описать исследуемый привод и провести математическое моделирование в контексте исследования влияния механических параметров на потребленную энергию в динамических режимах работы. Научная новизна. Разработан способ измерения крутящего момента на валу двигателя для исследования энергетических характеристик приводов электрических транспортных средств. Указанный способ базируется на контактном методе измерения, который использует 2 двигателя (нагрузочный и исследуемый) и тензометрический датчик силы и отличается от других конструкцией, что создает момент на валу исследующего двигателя. Результатом обработки экспериментальных данных, полученных данным способом, является аналитическая зависимость потребляемой приводом энергии от значения механической мощности на валу, параметрами которой являются угловая скорость и крутящий момент двигателя. Указанная энергетическая характеристика привода позволяет путем математического моделирования определить электромеханические параметры привода, минимизирующие его энергопотребление в динамических режимах работы. Практическая ценность. Предложен способ измерения момента на валу двигателя, с помощью которого определена в аналитическом виде зависимость потребляемой приводом энергии от механической мощности на валу двигателя, что позволяет путем математического моделирования найти электромеханические параметры системы, повышающие энергоэффективность привода электрического транспортного средства.Мета роботи. Розробка вузла вимірювання крутного моменту, у складі лабораторного комплексу для дослідження енергетичних характеристик електроприводів з метою математичного моделювання динамічних режимів роботи приводу електричного транспортного засобу. Методи дослідження . Фізичний експеримент, регресійний аналіз, інтерполяція. Отримані результати. Розроблено вузол вимірювання крутного моменту у складі лабораторного комплексу дослідження енергетичних характеристик приводів електричних транспортних засобів, конструкція якого дозволяє створювати крутний момент на валу досліджуваного двигуна за допомогою навантажувального і вимірювати його тензометричним датчиком сили. Лабораторний стенд разом із розробленим вузлом вимірювання моменту відповідає необхідному діапазону та точності вимірювань. Отримані на стенді експериментальні дані дозволяють визначити залежність споживаної електроприводом енергії від механічної потужності на валу досліджуваного двигуна, що дає можливість аналітично описати досліджуваний привод і провести математичне моделювання в контексті дослідження впливу механічних параметрів на спожиту енергію в динамічних режимах роботи. Наукова новизна. Розроблено спосіб вимірювання крутного моменту на валу двигуна для дослідження енергетичних характеристик приводів електричних транспортних засобів. Вказаний спосіб базується на контактному методі вимірювання, який використовує 2 двигуна (навантажувальний і досліджувальний) та тензометриичний датчик сили, відрізняється від інших конструкцією, що створює момент на валу досліджувального двигуна. Результатом обробки експериментальних даних, отриманих даним способом, є аналітична залежність споживаної приводом енергії від значення механічної потужності на валу, параметрами якої є кутова швидкість і крутний момент двигуна. Зазначена енергетична характеристика приводу дозволяє шляхом математичного моделювання визначити електромеханічні параметри приводу, що мінімізують його енергоспоживання у динамічних режимах роботи. Практична цінність. Запропоновано спосіб вимірювання моменту на валу двигуна, за допомогою якого визначена в аналітичному вигляді залежність енергії, що споживається приводом, від механічної потужності на валу двигуна. Це дозволяє шляхом математичного моделювання знайти електромеханічні параметри системи, що підвищують енергоефективність приводу електричного транспортного засобу

The Development of a Sensitive Manipulation Platform

This thesis presents an extension of sensitive manipulation which transforms tactile sensors away from end effectors and closer to whole body sensory feedback. Sensitive manipulation is a robotics concept which more closely replicates nature by employing tactile sensing to interact with the world. While traditional robotic arms are specifically designed to avoid contact, biological systems actually embrace and intentionally contact the environment. This arm is inspired by these biological systems and therefore has compliant joints and a tactile shell surrounding the two primary links of the arm. The manipulator has also been designed to be capable of both industrial and humanoid style manipulation. There are an untold number of applications for an arm with increased tactile feedback primarily in dynamic environments such as in industrial, humanoid, and prosthetic applications. The arm developed for this thesis is intended to be a desktop research platform, however, one of the most influential applications for increased tactile feedback is in prosthetics which are operate in ever changing and contact ridden environments while continuously interacting with humans. This thesis details the simulation, design, analysis, and evaluation of a the first four degrees of freedom of a robotic arm with particular attention given to the design of modular series elastic actuators in each joint as well as the incorporation of a shell of tactile sensors

Modelado de sensores piezoresistivos y uso de una interfaz basada en guantes de datos para el control de impedancia de manipuladores robóticos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Arquitectura de Computadores y Automática, leída el 21-02-2014Sección Deptal. de Arquitectura de Computadores y Automática (Físicas)Fac. de Ciencias FísicasTRUEunpu

Development of a low-profile planar sensor for the detection of normal and shear forces

Individuals with balance and mobility problems might benefit by the use of devices that detect small changes in ground reaction forces and potentially be used to assist movement. For maximum effectiveness, such sensors must measure pressure in all three dimensions. Impact and shear plantar force are essential variables in inverse dynamics reconstructions of the human joint force. Various force sensors have been proposed to monitor plantar forces of the human foot. Most of them have a single-axis measurement, and few are intended for monitoring normal and shear stress. This article proposes a low-cost, biocompatible triaxial piezoresistive sensor developed using simple fabrication techniques and inexpensive machinery. The sensor can detect pressures from 0-800kPa with high response and recovery with minimum hysteresis and repeatable results of over than 100 cycles

DISTRIBUTED ELECTRO-MECHANICAL ACTUATION AND SENSING SYSTEM DESIGN FOR MORPHING STRUCTURES

Smart structures, able to sense changes of their own state or variations of the environment they’re in, and capable of intervening in order to improve their performance, find themselves in an ever-increasing use among numerous technology fields, opening new frontiers within advanced structural engineering and materials science. Smart structures represent of course a current challenge for the application on the aircrafts. A morphing structure can be considered as the result of the synergic integration of three main systems: the structural system, based on reliable kinematic mechanisms or on compliant elements enabling the shape modification, the actuation and control systems, characterized by embedded actuators and robust control strategies, and the sensing system, usually involving a network of sensors distributed along the structure to monitor its state parameters. Technologies with ever increasing maturity level are adopted to assure the consolidation of products in line with the aeronautical industry standards and fully compliant with the applicable airworthiness requirements. Until few years ago, morphing wing technology appeared an utopic solution. In the aeronautical field, airworthiness authorities demand a huge process of qualification, standardization, and verification. Essential components of an intelligent structure are sensors and actuators. The actual technological challenge, envisaged in the industrial scenario of “more electric aircraft”, will be to replace the heavy conventional hydraulic actuators with a distributed strategy comprising smaller electro-mechanical actuators. This will bring several benefit at the aircraft level: firstly, fuel savings. Additionally, a full electrical system reduces classical drawbacks of hydraulic systems and overall complexity, yielding also weight and maintenance benefits. At the same time, a morphing structure needs a real-time strain monitoring system: a nano-engineered polymer capable of densely distributed strain sensing can be a suitable solution for this kind of flying systems. Piezoresistive carbon nanotubes can be integrated as thin films coated and integrated with composite to form deformable self-sensing materials. The materials actually become sensors themselves without using external devices, embedded or attached. This doctoral thesis proposes a multi-disciplinary investigation of the most modern actuation and sensing technologies for variable-shaped devices mainly intended for large commercial aircraft. The personal involvement in several research projects with numerous international partners - during the last three years - allowed for exploiting engineering outcomes in view of potential certification and industrialization of the studied solutions. Moving from a conceptual survey of the smart systems that introduces the idea of adaptive aerodynamic surfaces and main research challenges, the thesis presents (Chapter 1) the current worldwide status of morphing technologies as well as industrial development expectations. The Ph.D. programme falls within the design of some of the most promising and potentially flyable solutions for performance improvement of green regional aircrafts. A camber-morphing aileron and a multi-modal flap are herein analysed and assessed as subcomponents involved for the realization of a morphing wing. An innovative camber-morphing aileron was proposed in CRIAQ MD0-505, a joint Canadian and Italian research project. Relying upon the experimental evidence within the present research, the issue appeared concerns the critical importance of considering the dynamic modelling of the actuators in the design phase of a smart device. The higher number of actuators involved makes de facto the morphing structure much more complex. In this context (Chapter 2), the action of the actuators has been modelled within the numerical model of the aileron: the comparison between the modal characteristics of numerical predictions and testing activities has shown a high level of correlation. Morphing structures are characterized by many more degrees of freedom and increased modal density, introducing new paradigms about modelling strategies and aeroelastic approaches. These aspects affect and modify many aspects of the traditional aeronautical engineering process, like simulation activity, design criteria assessment, and interpretation of the dynamic response (Chapter 3). With respect the aforementioned aileron, sensitivity studies were carried out in compliance with EASA airworthiness requirements to evaluate the aero-servo-elastic stability of global system with respect to single and combined failures of the actuators enabling morphing. Moreover, the jamming event, which is one of the main drawbacks associated with the use of electro-mechanical actuators, has been duly analyzed to observe any dynamic criticalities. Fault & Hazard Analysis (FHA) have been therefore performed as the basis for application of these devices to real aircraft. Nevertheless, the implementation of an electro-mechanical system implies several challenges related to the integration at aircraft system level: the practical need for real-time monitoring of morphing devices, power absorption levels and dynamic performance under aircraft operating conditions, suggest the use of a ground-based engineering tool, i.e. “iron bird”, for the physical integration of systems. Looking in this perspective, the Chapter 4 deals with the description of an innovative multi-modal flap idealized in the Clean Sky - Joint Technology Initiative research scenario. A distributed gear-drive electro-mechanical actuation has been fully studied and validated by an experimental campaign. Relying upon the experience gained, the encouraging outcomes led to the second stage of the project, Clean Sky 2 - Airgreen 2, encompassing the development of a more robotized flap for next regional aircraft. Numerical and experimental activities have been carried out to support the health management process in order to check the EMAs compatibility with other electrical systems too. A smart structure as a morphing wing needs an embedded sensing system in order to measure the actual deformation state as well as to “monitor” the structural conditions. A new possible approach in order to have a distributed light-weight system consists in the development of polymer-based materials filled with conductive smart fillers such as carbon nanotubes (CNTs). The thesis ends with a feasibility study about the incorporation of carbon nanomaterials into flexible coatings for composite structures (Chapter 5). Coupons made of MWCNTs embedded in typical aeronautic epoxy formulation were prepared and tested under different conditions in order to better characterize their sensing performance. Strain sensing properties were compared to commercially available strain gages and fiber optics. The results were obtained in the last training year following the involvement of the author in research activities at the University of Salerno and Materials and Structures Centre - University of Bath. One of the issues for the next developments is to consolidate these novel technologies in the current and future European projects where the smart structures topic is considered as one of the priorities for the new generation aircrafts. It is remarkable that scientists and aeronautical engineers community does not stop trying to create an intelligent machine that is increasingly inspired by nature. The spirit of research, the desire to overcome limits and a little bit of imagination are surely the elements that can guide in achieving such an ambitious goal

Development of novel micropneumatic grippers for biomanipulation

Microbjects with dimensions from 1 μm to 1 mm have been developed recently for different aspects and purposes. Consequently, the development of handling and manipulation tools to fulfil this need is urgently required. Micromanipulation techniques could be generally categorized according to their actuation method such as electrostatic, thermal, shape memory alloy, piezoelectric, magnetic, and fluidic actuation. Each of which has its advantage and disadvantage. The fluidic actuation has been overlooked in MEMS despite its satisfactory output in the micro-scale. This thesis presents different families of pneumatically driven, low cost, compatible with biological environment, scalable, and controllable microgrippers. The first family demonstrated a polymeric microgripper that was laser cut and actuated pneumatically. It was tested to manipulate microparticles down to 200 microns. To overcome the assembly challenges that arise in this family, the second family was proposed. The second family was a micro-cantilever based microgripper, where the device was assembled layer by layer to form a 3D structure. The microcantilevers were fabricated using photo-etching technique, and demonstrated the applicability to manipulate micro-particles down to 200 microns using automated pick-and-place procedure. In addition, this family was used as a tactile-detector as well. Due to the angular gripping scheme followed by the above mentioned families, gripping smaller objects becomes a challenging task. A third family following a parallel gripping scheme was proposed allowing the gripping of smaller objects to be visible. It comprises a compliant structure microgripper actuated pneumatically and fabricated using picosecond laser technology, and demonstrated the capability of gripping microobject as small as 100 μm microbeads. An FEA modelling was employed to validate the experimental and analytical results, and excellent matching was achieved

Development of a Novel Impedance-Controlled Quasi-Direct-Drive Robot Hand

Most robotic hands and grippers rely on actuators with large gearboxes and force sensors for controlling gripping force. However, this might not be ideal for tasks which require the robot to interact with an unstructured and/or unknown environment. We propose a novel quasi-direct-drive two-fingered robotic hand with variable impedance control in the joint space and Cartesian space. The hand has a total of four degrees of freedom, a backdrivable gear train, and four brushless direct current (BLDC) motors. Field-Oriented Control (FOC) with current sensing is used to control motor torques. Variable impedance control allows the hand to perform dexterous manipulation tasks while being safe during human-robot interaction. The quasi-direct-drive actuators enable the fingers to handle contact with the environment without the need for complicated tactile or force sensors. A majority 3D printed assembly makes this a low-cost research platform built with affordable off-the-shelf components. The hand demonstrates grasping with force-closure and form-closure, stable grasps in response to disturbances, tasks exploiting contact with the environment, simple in-hand manipulation, and a light touch for handling fragile objects.Comment: 75 pages, A Thesis in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering at Stony Brook Universit