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Serial architectures. In the differential transmission symbol the smallest circle is the output while the outer circles are the two inputs. The represented springs are in general nonlinear. Serial architectures. In the differential transmission symbol the smallest circle is the output while the outer circles are the two inputs. The represented springs are in general nonlinear.
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![Figure 15: Drawing of the MESTRAN [61].](profile/Giorgio-Carpino/publication/234154336/figure/fig3/AS:670705817505792@1536920136000/Drawing-of-the-MESTRAN-61_Q320.jpg)
Novel compliant actuation systems have been developed in recent years for a variety of possible advantages, such as establishing a safe human–robot interaction, increasing energy efficiency, reducing the effects of impacts and even for the development of neuro-inspired robotic platforms to be used in human motor control studies.In this rapidly grow...
Citations
... Adjustable compliant structures are commonly known by different terms such as adjustable, controllable or variable -stiffness, damping or compliant -connection, mechanism, actuator, or element 11 . Vanderborght et al. 12 , van Ham et al. 13 , Tagliamonte et al. 14 , and Wolf et al. 15 show with their review papers the wide field of application of these elements. They primarily address the use in robotic applications. ...
This publication addresses the development of a compact, adjustable hydraulic damper that meets the requirements for vibration testing. Dampers from the literature do not meet all the requirements, such as compact design, vibration resistance, high strength, broadly adjustable and dominantly symmetrical damping, and modularity. Additive manufacturing (AM) enables the design of integral and compact systems that can compensate for several disadvantages of known damping systems. Three stages of development are presented, from a proof of concept to a prototype manufactured by Stereolithography (SLA) as Vat Photopolymerization (VPP-UVL/P) to a ready-to-use hydraulic damper manufactured by Selective Laser Melting (SLM) as Laser Powder Bed Fusion (PBF-LB/M). The final additively manufactured damper is much more compact due to its geometric freedom in the design phase and requires a much smaller number of components. The damper has been tested over a wide range of operating conditions and has proven its reliable damping performance even under high loads. This performance makes it suitable for many other systems subject to vibration.
... Adaptable compliance can be created via mechanical reconfiguration. The design is more complex, but passive compliance can absorb impact shocks and store energy [151][152][153]. ...
This literature review presents a comprehensive analysis of the use and potential application scenarios of collaborative robots in the industrial working world, focusing on their impact on human work, safety, and health in the context of Industry 4.0. The aim is to provide a holistic evaluation of the employment of collaborative robots in the current and future working world, which is being increasingly driven by the automation and digitization of production processes, and which can be outlined using the term Work 4.0. In this context, the forms of work organization, and the demands and impacts on humans are changing profoundly. Collaborative robots represent a key technology to aid the transition. The review utilizes expert interviews for identifying relevant keywords, and follows the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) framework to evaluate peer-reviewed literature between 2002 and January 2022. The analysis includes forms of interaction, and the distribution of roles, control interfaces, safety procedures, and ergonomics and health. In addition, the review offers a heatmap displaying the research topics of 715 publications for each year, and a database of these publications in BibTeX format that is publicly accessible. The review highlights the challenges, potential benefits, and trends of using collaborative robots in the industrial working world, emphasizing the importance of a careful evaluation of their impact on human work, safety, and health. It offers a tool set for researchers and practitioners to further explore and evaluate the employment of collaborative robots in Work 4.0.
... Several studies have proposed actuators that involve dual motors and transmission systems to obtain complaint actuation (Tagliamonte et al. 2012;Szufnarowski and Schneider 2010). The variable stiffness elastic actuators could further reduce the torque and power requirements of the system and therefore, by exploiting the elasticity of the elements, human gait could be performed in a much more energy-efficient way (Sugar and Holgate 2014;Verstraten et al. 2017;Tonietti, Schiavi, and Bicchi 2005;Hurst, Chestnutt, and Rizzi 2010). ...
Selection of an actuation system for assistive robotic exoskeletons requires careful consideration of various design factors. It is generally the requirement of the system to produce lightweight and power-efficient systems. In some cases, the torque and power requirements could be relaxed by using redundant systems. This paper involves the study of one such case in which the actuation redundancy of the system will be exploited, and the design optimization will be explored for a rigid and an elastic system. A multi-factor optimization technique will be developed for a redundant elastic actuation system. An actuator design framework will be used to evaluate the different actuator choices to determine the best motor and transmission system combination in a redundant actuation system arrangement. This will be evaluated for a rigid, parallel, and series elastic actuation system. The optimal redundant actuation system significantly reduced the power requirements of the system. The case study was virtually implemented. It was established that variable parallel elastic actuators (V-PEA) performed better as compared to variable series elastic actuators (V-SEA).
... C1. changing pretension of non-linear compliant components (often arranged in an antagonistic way [34])e.g. varying air pressure in a pair of pneumatic muscles, C2. changing transmission between the compliant component and output linke.g. ...
Modern robot applications benefit from including variable stiffness actuators (VSA) in the kinematic chain. In this paper, we focus on VSA utilizing a magnetic spring made of two coaxial rings divided into alternately magnetized sections. The torque generated between the rings is opposite to the angular deflection from equilibrium and its value increases as the deflection grows – within a specific range of angles that we call a stable range. Beyond the stable range, the spring exhibits negative stiffness what causes problems with prediction and control. In order to avoid it, it is convenient to operate within a narrower range of angles that we call a safe range. The magnetic springs proposed so far utilize few pairs of arc magnets, and their safe ranges are significantly smaller than the stable ones. In order to broaden the safe range, we propose a different design of the magnetic spring, which is composed of flat magnets, as well as a new arrangement of VSA (called ATTRACTOR) utilizing the proposed spring. Correctness and usability of the concept are verified in FEM analyses and experiments performed on constructed VSA, which led to formulating models of the magnetic spring. The results show that choosing flat magnets over arc ones enables shaping spring characteristics in a way that broadens the safe range. An additional benefit is lowered cost, and the main disadvantage is a reduced maximal torque that the spring is capable of transmitting. The whole VSA can be perceived as promising construction for further development, miniaturization and possible application in modern robotic mechanisms.
... The authors that employed this controller approached the mobile robot helper's base to perform the cooperative carrying of a load [52,53]. The authors of [54,55] also used a lifting controller with cascaded second-order virtual admittance controllers applied to the same applications. The authors of [56,57] designed and evaluated an interactive controller for cooperatively carrying a load with the help of the robot and human simultaneously. ...
Citation: Hameed, A.; Ordys, A.; Możaryn, J.; Sibilska-Mroziewicz, A. Control System Design and Methods for Collaborative Robots: Review. Appl. Sci. 2023, 13, 675. https:// Abstract: Collaborative robots cooperate with humans to assist them in undertaking simple-to-complex tasks in several fields, including industry, education, agriculture, healthcare services, security, and space exploration. These robots play a vital role in the revolution of Industry 4.0, which defines new standards of manufacturing and the organization of products in the industry. Incorporating collaborative robots in the workspace improves efficiency, but it also introduces several safety risks. Effective safety measures then become indispensable to ensure safe and robust interaction. This paper presents the review of low-level control methodologies of a collaborative robot to assess the current status of human-robot collaboration over the last decade. First, we discuss the classification of human-robot collaboration, architectures of systems and the complex requirements on control strategies. The most commonly used control approaches were presented and discussed. Several methods of control, reported in industrial applications, are elaborated upon with a prime focus on HR-collaborative assembly operations. Since the physical HRC is a critical control problem for the co-manipulation task, this article identifies key control challenges such as the prediction of human intentions, safety, and human-caused disturbances in motion synchronization; the proposed solutions were analyzed afterwards. The discussion at the end of the paper summarizes the features of the control systems that should be incorporated within the systematic framework to allow the execution of a robotic task from global task planning to low-level control implementation for safe and robust interactions.
... A robot joint construction can be implemented with one single electric drive or with a pair of antagonistically coupled drives (Tagliamonte et al. 2012). Implementation of an antagonistically coupled drives pair can bring more complexity in robot structure due to increased drives volume and mass, but a drives pair can eliminate reducer backlash if drives will be loaded each only in one single direction by using stretchers or springs. ...
In this review, we are considering an actively developing tool in neuroscience—robotic modeling. The new perspective and existing application fields, tools, and methods are discussed. We try to determine starting positions and approaches that are useful at the beginning of new research in this field. Among multiple directions of the research is robotic modeling on the level of muscles fibers and their afferents, skin surface sensors, muscles, and joints proprioceptors. Some examples of technical implementation for physical modeling are reviewed. They are software and hardware tools like event-related modeling algorithms, reduced neuron models, robotic drives constructions. We observe existing drives technologies and prospective electric motor types: switched reluctance and transverse flux motors. Next, we look at the existing examples and approaches for robotic modeling of the cerebellum and spinal cord neural networks. These examples show practical methods for the model neural network architecture and adaptation. Those methods allow the use of cortical and spinal cord reflexes for the network training and apply additional artificial blocks for data processing in other brain structures that transmit and receive data from biologically realistic models.
... To improve the safety of the robot, the best option is to mimic the stiffness adjustment of the human arm joints [1,2]. Based on the bionic principle of human muscles, early researchers proposed the pneumatic and electrical polymer artificial muscles [3]. ...
... According to the deflection angle Eqs. (2) and (3) of the free end and the vertical displacement distance of roller center is ω 1 and Eq. (5), the relationship between the passive deflection angle and the bending angle of the VSA can be obtained φ max : ...
Variable Stiffness Actuator (VSA) is the core mechanism to achieve physical human–robot interaction, which is an inevitable development trend in robotic. The existing variable stiffness actuators are basically single degree-of-freedom (DOF) rotating joints, which are achieving multi-DOF motion by cascades and resulting in complex robot body structures. In this paper, an integrated 2-DOF actuator with variable stiffness is proposed, which could be used for bionic wrist joints or shoulder joints. The 2-DOF motion is coupling in one universal joint, which is different from the way of single DOF actuators cascade. Based on the 2-DOF orthogonal motion generated by the spherical wrist parallel mechanism, the stiffness could be adjusted by varying the effective length of the springs, which is uniformly distributed in the variable stiffness unit. The variable stiffness principle, the model design, and theoretical analysis of the VSA are discussed in this work. The independence of adjusting the equilibrium position and stiffness of the actuator is validated by experiments. The results show that the measured actuator characteristics are sufficiently matched the theoretical values. In the future, VSA could be used in biped robot or robotic arm, ensuring the safety of human–robot interaction.
... The introduction of intrinsically compliant mechanisms, also widely adopted in active mechatronic and passive mechanical joints for human-centered and biomechanical applications (Vanderborght et al., 2013;Tagliamonte et al., 2012), ensures an adaptive behavior during the interaction with objects. ...
In the last decades, there have been great efforts in the development of advanced polyarticulated prosthetic hands; in contrast, prosthetic wrists have drawn less interest. Nevertheless, increasing the dexterity of the wrist improves handling skills because the wrist allows the prepositioning of the hand before carrying out a task, avoiding the onset of unwanted trunk or shoulders compensatory movements and potential onset or exacerbation of articular injuries. This study presents a novel 2‐degree‐of‐freedom prosthetic wrist module with active pronation/supination and passive elastic flexion/extension. This system is suitable to be included in hand prostheses to improve anthropomorphism and produce a more physiological motion. The first submodule within the socket is able to rotate a prosthetic hand and an external load of 3 kg at 2.6 rad/s. The second one can guarantee a range of motion of ±75° with a centering elastic torque (compliant mode) or it can keep firms grasps (fixed mode). Compliant mode is based on a Scotch‐Yoke mechanism converting wrist flexion/extension into the linear motion of a crossbeam acting on compression springs, while fixed mode is achieved by means of a piston that can be engaged/disengaged. The whole module fits with anthropometry and the modular design ensures the proposed system can be used in a stand‐alone way and adapted to different hand prostheses. This device is expected to favor a more physiological dexterity with respect to simpler fixed prostheses that can potentially induce harmful motion of body districts not naturally involved in the reaching and grasping tasks.
... In previous publications, the usage of variable stiffness mechanisms have been widely discussed in the domain of robotics or actuators for safe and efficient operation [1][2][3][4][5]. Variable stiffness mechanisms are designed such that their mechanical interface stiffness can be adjusted in a certain range. ...
This contribution examines a variable stiffness mechanism that is intended for the use as a boundary element in vibration tests. The mechanism consists of two antagonistic nonlinear springs guided along the central axis. The axis is axially guided via two bearings. This paper concerns itself with comparing the effects of friction and roller bearings on the frequency response. Further, a comparison of different measurement techniques for the dynamic characterization of the aforementioned mechanism is in focus. An experimental study utilizing a multisine, sine-sweep, and impulse excitation signal is conducted. A nonlinear numerical model as well as a linear approximation are presented and compared with the measurement results. The results indicate that friction bearings have a strong influence on the frequency response of the system, especially at low displacement amplitudes. The influence of the friction contact on the results of different measurement methods is shown. The presented variable stiffness mechanism with the roller bearing configuration yielded in a predictable vibration behavior even for high mechanism pretensions.
... In the flexible actuation technologies of the robots, there are several common implementation methods. For example, the active compliance control of the rigid robot joints based on algorithms and sensors [1], [2], the compliance control based on magnetorheological fluid damper [3], the series elastic actuators [4], [5], the flexible pneumatic actuators [6], [7], [8], [9], the cable-driven flexible actuators [10], [11], [12], the flexible actuator based on magnetic spring [13], and the variable impedance actuator with special structural designs [14], [15], etc. Among the above flexible actuation methods, the active compliance control and the variable impedance control are the most studied and applied. ...
... When a new deformation s of the spring occurs under the action of the slider, the new elastic potential energy stored in the elastic output module of the VSA can be expressed by Equation (15). ...
... In Figure 17(e), the (12) refers to the mounting base of two motor reducers, and the (13) refers to the bearing locating ring, and the (14) refers to the bearing on the lever pivot, which contacts with the wire rope in the spring module to reduce friction. The (15), the (16) and the (17) are firmly connected by bolts. The (18) refers to the output shaft of the actuator, which is fixedly connected with the spring module. ...
Among many types of flexible robot actuators, the variable stiffness actuator (VSA) is an actuator that can adjust the compliance of the actuator output shaft by adjusting the equivalent stiffness of its internal elastic element. Compared with the traditional rigid actuators, the VSAs have inherent flexibility and adjustable stiffness because they contain elastic elements and stiffness adjusting mechanisms. They have advantages in human-robot physical interaction security and task adaptability. The independent controllability of position and stiffness and the ability of stiffness adjustment make the VSAs have research value and application prospects in the fields of rehabilitation training equipment, prosthetics, wearable devices and so on. The mechanical scheme design of the VSA is an open research field. At present, there is no perfect mechanical structure design of any type of VSA. Optimizing and improving the mechanical structure design of the VSA is helpful to improve its actuation characteristics and application value. Due to the limitation of the mechanical structure design, most of the existing VSAs have limited rotation angle range of the output shaft, which limits their application. The purpose of this paper is to design the parallel driven VSA whose rotation angle range of output shaft is not limited. Moreover, inspired by the mechanical structure design ideas of some stiffness adjustment mechanisms with good implementation schemes and elastic elements with good force transmission characteristics, this paper makes some improvement, synthesis and innovation in the mechanical structure design of the VSA, so as to improve the structural compactness design, assembly modular design, mechanical transmission reliability design and actuation characteristics. The main contribution of this paper is that six types of parallel drive VSAs with unrestricted rotation angle range of output shaft have been proposed, and they have different implementation schemes of stiffness adjustment mechanisms and elastic elements. The transmission structure diagrams of the designed VSAs show the working principle and stiffness adjustment principle. The actuation characteristics of the designed VSAs are analyzed and their differences are compared. The detailed mechanical structure scheme views of the VSAs are shown. The differences between the designed VSAs and the reference VSAs in mechanical structure designs are described. In the designed VSAs, the model of the VSA based on the symmetrical Archimedes spiral cam groove plate mechanism is printed and assembled to show the feasibility of the implementation of the designed mechanical structure scheme. Finally, a manual adjustment experiment verifies the stiffness adjustment ability of the assembled VSA model, and shows that the rotation angle range of the output shaft of the assembled VSA model is unlimited.
