A model-based residual approach for human-robot collaboration during manual polishing operations

A fully robotized polishing of metallic surfaces may be insufficient in case of parts with complex geometric shapes, where a manual intervention is still preferable. Within the EU SYMPLEXITY project, we are considering tasks where manual polishing operations are performed in strict physical Human-Robot Collaboration (HRC) between a robot holding the part and a human operator equipped with an abrasive tool. During the polishing task, the robot should firmly keep the workpiece in a prescribed sequence of poses, by monitoring and resisting to the external forces applied by the operator. However, the user may also wish to change the orientation of the part mounted on the robot, simply by pushing or pulling the robot body and changing thus its configuration. We propose a control algorithm that is able to distinguish the external torques acting at the robot joints in two components, one due to the polishing forces being applied at the end-effector level, the other due to the intentional physical interaction engaged by the human. The latter component is used to reconfigure the manipulator arm and, accordingly, its end-effector orientation. The workpiece position is kept instead fixed, by exploiting the intrinsic redundancy of this subtask. The controller uses a F/T sensor mounted at the robot wrist, together with our recently developed model-based technique (the residual method) that is able to estimate online the joint torques due to contact forces/torques applied at any place along the robot structure. In order to obtain a reliable residual, which is necessary to implement the control algorithm, an accurate robot dynamic model (including also friction effects at the joints and drive gains) needs to be identified first. The complete dynamic identification and the proposed control method for the human-robot collaborative polishing task are illustrated on a 6R UR10 lightweight manipulator mounting an ATI 6D sensor

A Base Force/Torque Sensor Approach to Robot

Experimental results presented show that an accurate estimation of inertia parameters is attainable. Since the sensor is external to the manipulator, the same sensor can be used for parameter estimation for a number of different systems

Space Construction Experiment Definition Study (SCEDS), part 2. Volume 1: Executive summary

A baseline Space Construction Experiment (SCE) concept is defined. Five characteristics were incorporated: (1) large space system (LSS) element test, (2) shuttle mission payload of opportunity, (3) attachment to Orbiter with jettison capability, (4) Orbiter flight control capabilities, and (5) LSS construction and assembly operations

Simulating the dynamic interaction of a robotic arm and the Space Shuttle remote manipulator system

Industrial robots are usually attached to a rigid base. Placing the robot on a compliant base introduces dynamic coupling between the two systems. The Vehicle Emulation System (VES) is a six DOF platform that is capable of modeling this interaction. The VES employs a force-torque sensor as the interface between robot and base. A computer simulation of the VES is presented. Each of the hardware and software components is described and Simulink is used as the programming environment. The simulation performance is compared with experimental results to validate accuracy. A second simulation which models the dynamic interaction of a robot and a flexible base acts as a comparison to the simulated motion of the VES. Results are presented that compare the simulated VES motion with the motion of the VES hardware using the same admittance model. The two computer simulations are compared to determine how well the VES is expected to emulate the desired motion. Simulation results are given for robots mounted to the end effector of the Space Shuttle Remote Manipulator System (SRMS). It is shown that for fast motions of the two robots studied, the SRMS experiences disturbances on the order of centimeters. Larger disturbances are possible if different manipulators are used

Validation of an extended foot-ankle musculoskeletal model using in vivo 4D CT data

openPer simulare il movimento del corpo umano, è necessario creare dei modelli che rappresentino le strutture anatomiche. In questo elaborato ci si concentrerà su un modello biomeccanico del complesso piede-caviglia implementato in un software per la modellazione muscoloscheletrica, nella fattispecie OpenSim. OpenSim è un software che consente di sviluppare modelli di strutture muscoloscheletriche e creare simulazioni dinamiche in grado di stimare i parametri interni delle strutture anatomiche (come le forze muscolari e di contatto tra le ossa), attraverso la simulazione della cinematica e la cinetica del movimento delle varie strutture coinvolte. Nel presente elaborato, si è partiti dallo studio di un dataset, acquisito da Boey et al. (2020) tramite scansione 4D CT in combinazione con un dispositivo di manipolazione del piede su soggetti sani e pazienti affetti da instabilità cronica di caviglia. In questo modo è stata valutata la cinematica dell’osso del piede durante il cammino simulato. Lo scopo di questo elaborato è quindi validare un modello del complesso piede-caviglia sviluppato da Malaquias et al. (2016), partendo dai dati acquisiti affinché, imponendo il movimento della pedana, la simulazione restituisca delle variabili comparabili a quelle reali. Il modello muscoloscheletrico esteso del complesso piede-caviglia è composto da sei segmenti rigidi e cinque articolazioni anatomiche (caviglia, sottoastragalica, mediotarsica, tarsometatrsale e metatarsofalangea) per un totale di otto gradi di libertà. A questo modello è stata aggiunto una pedana (per simulare il dispositivo di manipolazione utilizzato nella sperimentazione) e sono stati incrementati i gradi di libertà delle articolazioni di caviglia e sottoastragalica, per ottenere tre gradi di libertà ciascuna. Dopodiché, è stato imposto un movimento combinato di inversione\eversione ed ab-adduzione alla pedana ed è stato valutato il movimento del modello del piede rispetto al dataset.To simulate the movement of the human body, it is necessary to create models that represent anatomical structures. In this thesis the focus will be placed on a biomechanical model of the complex foot-ankle implemented in a software for musculoskeletal modeling, in particular OpenSim. OpenSim is software that allows to develop models of musculoskeletal structures and create dynamic simulations capable of estimating the internal parameters of anatomical structures (such as muscle and contact forces between bones), through the simulation of the kinematics and kinetics of the movement of the various anatomical structures involved. In this paper, the starting point was the study of a dataset, acquired by Boey et al. (2020) with 4D CT scan in combination with a foot manipulator device. The study was run on healthy subjects as well as patients with chronic ankle instability. In this way, the kinematics of the movement of the foot bones during simulated gait was evaluated. The aim of this project was to validate a model of the foot-ankle complex, developed by Malaquias et al. (2016), starting from the acquired data, so that, by imposing the movement of the platform, the simulation would return variables comparable to the dataset. This extended musculoskeletal model of the foot-ankle complex is composed of six rigid segments and five anatomical joints (ankle, subtalar, midtarsal, tarsometatarsal, and metatarsophalangeal) for a total of eight degrees of freedom. A footplate was added to this model (to simulate the foot manipulator device utilized in the experiment) and the degrees of freedom of the ankle and subtalar joints were increased, to obtain three degrees of freedom each. After that, a combined inversion\eversion and plantar\dorsiflexion movement was imposed on the footplate and the movement of the foot model was evaluated against the dataset

Compliant aerial manipulation.

The aerial manipulation is a research field which proposes the integration of robotic manipulators in aerial platforms, typically multirotors – widely known as “drones” – or autonomous helicopters. The development of this technology is motivated by the convenience to reduce the time, cost and risk associated to the execution of certain operations or tasks in high altitude areas or difficult access workspaces. Some illustrative application examples are the detection and insulation of leaks in pipe structures in chemical plants, repairing the corrosion in the blades of wind turbines, the maintenance of power lines, or the installation and retrieval of sensor devices in polluted areas. Although nowadays it is possible to find a wide variety of commercial multirotor platforms with payloads from a few gramps up to several kilograms, and flight times around thirty minutes, the development of an aerial manipulator is still a technological challenge due to the strong requirements relative to the design of the manipulator in terms of very low weight, low inertia, dexterity, mechanical robustness and control. The main contribution of this thesis is the design, development and experimental validation of several prototypes of lightweight (<2 kg) and compliant manipulators to be integrated in multirotor platforms, including human-size dual arm systems, compliant joint arms equipped with human-like finger modules for grasping, and long reach aerial manipulators. Since it is expected that the aerial manipulator is capable to execute inspection and maintenance tasks in a similar way a human operator would do, this thesis proposes a bioinspired design approach, trying to replicate the human arm in terms of size, kinematics, mass distribution, and compliance. This last feature is actually one of the key concepts developed and exploited in this work. Introducing a flexible element such as springs or elastomers between the servos and the links extends the capabilities of the manipulator, allowing the estimation and control of the torque/force, the detection of impacts and overloads, or the localization of obstacles by contact. It also improves safety and efficiency of the manipulator, especially during the operation on flight or in grabbing situations, where the impacts and contact forces may damage the manipulator or destabilize the aerial platform. Unlike most industrial manipulators, where force-torque control is possible at control rates above 1 kHz, the servo actuators typically employed in the development of aerial manipulators present important technological limitations: no torque feedback nor control, only position (and in some models, speed) references, low update rates (<100 Hz), and communication delays. However, these devices are still the best solution due to their high torque to weight ratio, low cost, compact design, and easy assembly and integration. In order to cope with these limitations, the compliant joint arms presented here estimate and control the wrenches from the deflection of the spring-lever transmission mechanism introduced in the joints, measured at joint level with encoders or potentiometers, or in the Cartesian space employing vision sensors. Note that in the developed prototypes, the maximum joint deflection is around 25 degrees, which corresponds to a deviation in the position of the end effector around 20 cm for a human-size arm. The capabilities and functionalities of the manipulators have been evaluated in fixed base test-bench firstly, and then in outdoor flight tests, integrating the arms in different commercial hexarotor platforms. Frequency characterization, position/force/impedance control, bimanual grasping, arm teleoperation, payload mass estimation, or contact-based obstacle localization are some of the experiments presented in this thesis that validate the developed prototypes.La manipulación aérea es un campo de investigación que propone la integración de manipuladores robóticos in plataformas aéreas, típicamente multirotores – comúnmente conocidos como “drones” – o helicópteros autónomos. El desarrollo de esta tecnología está motivada por la conveniencia de reducir el tiempo, coste y riesgo asociado a la ejecución de ciertas operaciones o tareas en áreas de gran altura o espacios de trabajo de difícil acceso. Algunos ejemplos ilustrativos de aplicaciones son la detección y aislamiento de fugas en estructura de tuberías en plantas químicas, la reparación de la corrosión en las palas de aerogeneradores, el mantenimiento de líneas eléctricas, o la instalación y recuperación de sensores en zonas contaminadas. Aunque hoy en día es posible encontrar una amplia variedad de plataformas multirotor comerciales con cargas de pago desde unos pocos gramos hasta varios kilogramos, y tiempo de vuelo entorno a treinta minutos, el desarrollo de los manipuladores aéreos es todavía un desafío tecnológico debido a los exigentes requisitos relativos al diseño del manipulador en términos de muy bajo peso, baja inercia, destreza, robustez mecánica y control. La contribución principal de esta tesis es el diseño, desarrollo y validación experimental de varios prototipos de manipuladores de bajo peso (<2 kg) con capacidad de acomodación (“compliant”) para su integración en plataformas aéreas multirotor, incluyendo sistemas bi-brazo de tamaño humano, brazos robóticos de articulaciones flexibles con dedos antropomórficos para agarre, y manipuladores aéreos de largo alcance. Puesto que se prevé que el manipulador aéreo sea capaz de ejecutar tareas de inspección y mantenimiento de forma similar a como lo haría un operador humano, esta tesis propone un enfoque de diseño bio-inspirado, tratando de replicar el brazo humano en cuanto a tamaño, cinemática, distribución de masas y flexibilidad. Esta característica es de hecho uno de los conceptos clave desarrollados y utilizados en este trabajo. Al introducir un elemento elástico como los muelles o elastómeros entre el los actuadores y los enlaces se aumenta las capacidades del manipulador, permitiendo la estimación y control de las fuerzas y pares, la detección de impactos y sobrecargas, o la localización de obstáculos por contacto. Además mejora la seguridad y eficiencia del manipulador, especialmente durante las operaciones en vuelo, donde los impactos y fuerzas de contacto pueden dañar el manipulador o desestabilizar la plataforma aérea. A diferencia de la mayoría de manipuladores industriales, donde el control de fuerzas y pares es posible a tasas por encima de 1 kHz, los servo motores típicamente utilizados en el desarrollo de manipuladores aéreos presentan importantes limitaciones tecnológicas: no hay realimentación ni control de torque, sólo admiten referencias de posición (o bien de velocidad), y presentan retrasos de comunicación. Sin embargo, estos dispositivos son todavía la mejor solución debido al alto ratio de torque a peso, por su bajo peso, diseño compacto y facilidad de ensamblado e integración. Para suplir estas limitaciones, los brazos robóticos flexibles presentados aquí permiten estimar y controlar las fuerzas a partir de la deflexión del mecanismo de muelle-palanca introducido en las articulaciones, medida a nivel articular mediante potenciómetros o codificadores, o en espacio Cartesiano mediante sensores de visión. Tómese como referencia que en los prototipos desarrollados la máxima deflexión articular es de unos 25 grados, lo que corresponde a una desviación de posición en torno a 20 cm en el efector final para un brazo de tamaño humano. Las capacidades y funcionalidades de estos manipuladores se han evaluado en base fija primero, y luego en vuelos en exteriores, integrando los brazos en diferentes plataformas hexartor comerciales. Caracterización frecuencial, control de posición/fuerza/impedancia, agarre bimanual, teleoperación de brazos, estimación de carga, o la localización de obstáculos mediante contacto son algunos de los experimentos presentados en esta tesis para validar los prototipos desarrollados por el auto

Evolution of the measurement of body segment inertial parameters since the 1970s

Since the development of biomechanics as a sub-discipline within movement science in the last 35 to 40 years (1), analysis techniques have evolved rapidly. To attain the goals of sports biomechanics - performance enhancement, comfort, injury prevention and safety (2) - it has been necessary to further develop techniques to both quantify and analyse data. Research questions have evolved from quantification of movement to questioning how and why movement occurs, and optimisation of performance. Methods of reconstruction such as the 3D Direct Linear Transformation (DLT) (3) and 2D-DLT (4) have evolved from creation to determination of the most accurate reconstruction method (5). Motion analysis has evolved from force-time data (6) to online systems and real-time feedback (7). Errors from soft tissue motion are now investigated to quantify and correct (8-9). Data smoothing has evolved from Winter et al.’s original paper on removal of kinematic noise (10) to modern work by Robertson and Dowling (11) investigating optimal filter design. Computer modelling has evolved from simplistic models of the 70s and 80s investigating simple locomotion (12) to sophisticated modern models of high bar gymnastics (13), high jump (14) and muscle stiffness of the horse (15). Initial work on co-ordination by Bernstein (16) has now evolved into a distinct field of motor control (17-18), with its own measurement issues (19). The focus of this article, however, is on the evolution of measurement techniques for determination of body segment inertial parameters (BSIP) with particular emphasis on development of mathematical models and scanning and imaging techniques

Automation and Robotics: Latest Achievements, Challenges and Prospects

This SI presents the latest achievements, challenges and prospects for drives, actuators, sensors, controls and robot navigation with reverse validation and applications in the field of industrial automation and robotics. Automation, supported by robotics, can effectively speed up and improve production. The industrialization of complex mechatronic components, especially robots, requires a large number of special processes already in the pre-production stage provided by modelling and simulation. This area of research from the very beginning includes drives, process technology, actuators, sensors, control systems and all connections in mechatronic systems. Automation and robotics form broad-spectrum areas of research, which are tightly interconnected. To reduce costs in the pre-production stage and to reduce production preparation time, it is necessary to solve complex tasks in the form of simulation with the use of standard software products and new technologies that allow, for example, machine vision and other imaging tools to examine new physical contexts, dependencies and connections

Model-Based Robot Control and Multiprocessor Implementation

Model-based control of robot manipulators has been gaining momentum in recent years. Unfortunately there are very few experimental validations to accompany simulation results and as such majority of conclusions drawn lack the credibility associated with the real control implementation