Design and control of a low profile electromagnetic actuator for foldable pop-up mechanisms

Thin foldable origami mechanisms bring miniaturization and reconfiguration of complex structures allowing large volumetric change, low cost and versatility. Many applications require small robots with multiple capabilities including movement, sensing and communication. One of the major design constraints in these systems is miniaturization, in particular actuator down-scaling. To meet the challenges, researchers have focused both on investigating designs that use high power to size ratio actuators as well as defining novel fabrication methods that aid reduced size component integration. This paper presents a novel approach for designing and controlling a low profile electromagnetic (EM) actuation system that can provide high speeds and easy control. Additionally, the system can be embedded in miniaturized foldable mechanisms. We report here the modelling of the low-profile EM actuator and the design methodology; further, the fabrication of a 3-cm wide, 1.4 mm thick prototype and real case scenario testing were executed. Our extensive test results verify the position control performance and validate the thermo-mechanical model in terms of expected steady state temperature and dependency by actuation frequency.

Development and control of interactive reconfigurable robotic systems

Jian-Lin Huang

While reconfigurable robots provide a new promising approach for interactive systems, the complexity of distributed actuation/sensing systems, coupled kinematics and desired functionalities also bring new challenges and questions both in control design and hardware development: What design approaches enable direct human-robot interactions to address the morphological transformations and constraints of multi-DoF distributed activated robotic system? How to implement in-situ, multi-stage, programmable, and controllable actuation for the desired range of motion and functionalities? How to design multi-DoF robotic systems and needed for operation in distinct, real-world applications? These challenges and research questions formulate the objective and framework of my thesis. Namely, I explore for the solutions to provide methodologies for not only building the hardware for reconfigurable interactive systems but also investigating the control algorithm considering human-in-the-loop and evaluating the effectiveness of the integrated system with different application scenarios. In order to address the challenges associated with the development of reconfigurable robotic systems for human interactions, I first outline the concept of an interactive interface between humans and robots. I study the design methods for intuitively and dynamically controlling multi-DoF reconfigurable systems and algorithms for integrating mechanical characteristics of the core robotic components. Then, we investigate the design space and limitation of gesture-based multi-modalities interactions for further exploring the controllability, scalability, and versatility in functions for reconfigurable robotic systems. To realize the reconfigurable interactive robotic system, the design, capability, and limitation of the hardware system need to be established and evaluated. One of my research goals is to take the advantage of current non-conventional manufacturing technologies and materials as well as overcome their limitations. I study and develop compact actuators and unique transmission mechanisms inspired by origami patterns that can be integrated with multi-DoF robotic systems. I start with the design, model, and experimental validation of core functional components. Then, we investigate the fabrication process which has an additive manufactured structure with subtractive manufactured functional components integrated for compact, light-weight, and distributed activated mechanisms. Lastly, I propose the strategies for configuring and controlling the functional components to achieve functionalities like multi-DoF distributed actuation, self-assembly, and tunable stiffness. The achievable functionalities are further examined with several application scenarios. The main contributions of this thesis are: Development of interactive control interface for reconfigurable robotic systems Design and validation of distributed actuation solution and transmission mechanisms for compact multi-DoF robotic systems Study the synergy of additive manufacturing techniques and smart materials for achieving customizable functionalities and overcoming the limitation for conventional robotic systems

EPFL2021

Méthodologie de conception et optimisation d'actionneurs intégrés sans fer

Igor Stefanini

The growing demand for new technologies in several fields : recreation, medicine, transport, telecommunications and the space industry, etc. is increasingly related to the field of the management, transformation and use of electric power. In this domain, the development of no-ferromagnetic integrated electromechanical actuators finds wide application and thus implies an usefulness over a large diversity of geometries. The absence of ferromagnetic materials does not allow for quick determination of an equivalent electromagnetic circuit for this type of actuator. The interaction of the magnetic induction fields produces phenomenas like the skin effect and the proximity effect which degrade its performance. In such circumstances, there is a compromise to be made between the analytical model's complexity and the precision of the results. Often, a modeling based on numerical approaches, which uses finite element methods, is the best adapted approach. Nevertheless, this type of analysis requires much experience and in particular, the parameterization of the actuator specifications and the exploitation of such a model in the optimized design is not very practical and requires considerable computing time. The use of discretized analytical models constitutes a good compromise between the degree of complexity and the model's correspondence to reality. Accordingly, in this thesis, we propose a suite of discretized analytical models allowing for the design and the optimization of this type of actuator. The development of a general rule to determine the optimal discretization step allows an arbitration between computing time, degree of complexity, and the precision of the results. The identification and the validation of the analytical models describing the skin and proximity effects have made it possible to improve the computation of self-inductance and winding resistance. The development of a design and optimization methodology for this type of actuator permits each application to be optimized in a systematic and efficient way, by proposing one or more possible solutions with their advantages and their disadvantages. Two distinct applications were conceived and optimized adopting this design methodology : the Montrac® system and the Iglus® system. In the Montrac® project, it was a question of modifying the power system of a modular assembly line. This system is composed of a fixed track with motorized shuttles for use in a clean room environment. The replacement of the electrical contacts by a contactless energy transmission system was dimensioned and optimized in order to guarantee an operation compatible with the requirements of the above mentioned environment. In the Iglus® project, a subcutaneous biomedical actuator for glycemic level detection, with the aim of measuring the glucose level of diabetes patients was optimized. The measurements and results from these two applications, made it possible to confirm the validity of the models expounded in this thesis.

EPFL2006

Escapement-Based Movements as Positioning Mechanisms: Design and Modelling

Romain David Besuchet

This work has been triggered by an industrial project targeting the design of a mechatronic injector for the medical field. Injections are usually performed using a syringe, a quite clumsy tool that transforms the injection task in a positioning one. The quality of injections can be enhanced by using devices that help control the injected dose, or the injection rate, but usually at the cost of a slower operation, a reduced manoeuvrability, or a short battery life for electrically-powered devices. The idea was therefore to provide a cordless miniaturised injector capable of managing the dosage as well as injection rate according to the user's desires, with the constraint that it should have a long battery life. This is why escapementbased movements are investigated in this work. Such stepper movements, where a regulator controls the speed at which a stock of mechanical energy is emptied, have been used for centuries in clockwork. Purely mechanical devices, the regulators are designed to work at a given frequency, with the stability of said frequency as the main objective. For the discussed application, the use of an electronic regulator permits variable injection rates and simplifies dosage control. Beingmostly used in clockwork, escapement-based movements are hardly mentioned, let alone studied, outside this field in the literature. This research is aimed at filling this void to provide engineers with the basics for the design of escapement-based movements, using Pahl & Beitz's design methodology. First of all, a general structure of suchmovements is proposed. Using functional analysis, a canvas for the requirements specification of a movement is given. To ensure an efficient and fast evaluation of the quality of a solution at any stage of the development, modelling and design tools are suggested. The industrial project is then used as a case study that exemplifies the concepts introduced. The requirements, a selected functioning principle, and the main technical solutions are described. The application of the modelling tools is done in two parts, representing two subsystems designed concurrently but separately: the purely mechanical part of the movement that includes the escapement, and the mechatronic regulator. The dynamic and energetic performances of both subsystems are modelled, using relevant techniques. Analytical models characterise the mechanical part of the system, using advantageously the stepper nature of the system. Because they are analytical, the models require very limited computational resources and are thus extremely convenient design tools. They also permit a stochastic study of the influence of manufacturing tolerances on said performance. Regulators, in particular electronically-controlled ones, are then discussed. An optimisation strategy for highly constrained problems is proposed. It consists in first optimising a set of input parameters towards acceptable values for the constraints. Once one or more sets of parameters respecting the constraints are found, these sets are used as initial points for the actual optimisation of the objectives. The efficacy of this strategy is demonstrated by an example. Finally, a prototype of the devised escapement-based movement is presented. It is used to establish the validity of the developedmodels, but also demonstrate the capabilities of the retained functioning principle.

EPFL2016