Proposed Actuation System Research Articles

Compact Design and Task Space Control of a Robotic Transcatheter Delivery System for Mitral Valve Implant.

Mitral regurgitation (MR) is one of the most common valvular abnormalities, and the gold-standard for treatment is surgical mitral valve repair/replacement. Most patients with severe MR are over the age of 75, which makes open-heart surgery challenging. Thus, minimally invasive surgeries using transcatheter approaches are gaining popularity. This paper proposes the next generation of a robotic transcatheter delivery system for the mitral valve implant that focuses on the design of the actuation system, modeling, and task space control. The proposed actuation system is compact while still enabling bidirectional torsion, bending, and prismatic joint motion. A pulley structure is employed to actuate the torsion and bending joints using only one motor per joint in conjunction with an antagonistic passive spring to reduce tendon slack. The robotic transcatheter is also optimized to increase its stability and reduce bending deflection. An inverse kinematics model (with an optimization algorithm), singularity analysis method, and joint hysteresis and compensation model are developed and verified. Finally, a task space controller is also proposed. Experiments, including trajectory tracking and demonstrations of the robot motion in an ex vivo porcine heart and a phantom heart through a tortuous path are presented.

Scope actuation system for articulated laparoscopes

BackgroundAn articulated laparoscope comprises a rigid shaft with an articulated distal end to change the viewing direction. The articulation provides improved navigation of the operating field in confined spaces. Furthermore, incorporation of an actuation system tends to enhance the control of an articulated laparoscope.MethodsA preliminary prototype of a scope actuation system to maneuver an off-the-shelf articulated laparoscope (EndoCAMaleon by Karl Storz, Germany) was developed. A user study was conducted to evaluate this prototype for the surgical paradigm of video-assisted thoracic surgery. In the study, the subjects maneuvered an articulated scope under two modes of operation: (a) actuated mode where an operating surgeon maneuvers the scope using the developed prototype and (b) manual mode where a surgical assistant directly maneuvers the scope. The actuated mode was further assessed for multiple configurations based on the orientation of the articulated scope at the incision.ResultsThe data show the actuated mode scored better than the manual mode on all the measured performance parameters including (a) total duration to visualize a marked region, (a) duration for which scope focus shifts outside a predefined visualization region, and (c) number of times for which scope focus shifts outside a predefined visualization region. Among the different configurations tested using the actuated mode, no significant difference was observed.ConclusionsThe proposed articulated scope actuation system facilitates better navigation of an operative field as compared to a human assistant. Secondly, irrespective of the orientation in which an articulated scope’s shaft is inserted through an incision, the proposed actuation system can navigate and visualize the operative field.

One-Shot 3D Printed Soft Device Actuated Using Metal-Filled Channels and Sensed with Embedded Strain Gauge.

In this article, the multimaterial extrusion (M-MEX) technology is used to fabricate, in a single step, a three-dimensional printed soft electromagnetic (EM) actuator, based on internal channels, filled with soft liquid metal (Galinstan) and equipped with an embedded strain gauge, for the first time. At the state of the art, M-MEX techniques result underexploited for the manufacture of soft EM actuators: only traditional manufacturing approaches are used, resulting in many assembly steps. The main features of this work are as follows: (1) one shot fabrication, (2) smart structure equipped with sensor unit, and (3) scalability. The actuator was tested in conjunction with a commercial magnet, showing a bending angle of 22.4° (when activated at 4A), a relative error of 0.7%, and a very high sensor sensitivity of 49.7 Two more examples, showing all the potentialities of the proposed approach, are presented: a jumping frog-inspired soft robot and a dual independent two-finger actuator. This article aims to push the role of extrusion-based additive manufacturing for the fabrication of EM soft robots: several advantages such as portability, no cooling systems, fast responses, and noise reduction can be achieved by exploiting the proposed actuation system compared to the traditional and widespread actuation mechanisms (shape memory polymers, shape memory alloys, pneumatic actuation, and cable-driven actuation).

Electromagnetic actuator design for distributed stiffness

Origami robots characterized by rigid plates linked together with flexible joints have inherent compliance and large deformations. Their low-profile design and folding mechanical transmissions provide substantial force and torque, especially for wearables and human-interactive devices. The current major limitation in the field is the need for embeddable dynamic actuation systems that produce actuation frequencies similar to human motion. In this study, we propose a novel low-profile printable electromagnetic actuator that can be integrated into thin large robotic surfaces made of rigid panels and into the streamlined pushbutton manufacturing process. We use already existing variable stiffness joints to demonstrate the scalability and distributable properties of the proposed actuation system on a locally controllable variable-stiffness distributed surface.

Analysis and Optimal Design of a Novel Actuator System for a Camera Module

Owing to the fourth industrial revolution and the recent trend for compact, high-performance, and multifunctional electrical devices, the demand for a small and high-performance camera module has dramatically increased. To address this, in this study, a novel, miniaturized, high-performance, low-cost multifunctional camera module with optical image stabilization (OIS) via a novel two-axis motional actuator with 1-Stage is proposed. To date, a systematic analysis and optimal design method for the actuators of camera modules has not been proposed yet. Accurate and rapid analysis and optimal design methods are proposed herein. Based on the proposed methods, it is possible to reduce the time and cost for the development of actuators for camera modules. The usefulness of the proposed actuator system for small, high performance, and multifunctional camera modules, and the proposed analysis and optimal design method were verified experimentally in this study.

Flexible-elastomer-based active radial embedded actuation system of railway vehicles

To improve the integration of active radial systems of railway vehicles and their adaptability to the vehicle structure, this paper proposes an active radial actuation system based on flexible elastomers. The execution unit of the system has a compact layout and can be embedded in an axle box. The core functional component is a flexible elastic oil-filled rubber bladder, which has active radial actuating capabilities and provides primary longitudinal suspension stiffness. To clarify these aspects of the execution unit, the typical physical properties of the rubber bladder are analysed using a fluid-structure-interaction finite element analysis method. The resulting calculation data are used to formulate the response characteristic equation of the execution unit. This equation is used to establish a simulation model of the actuation system, and the response characteristics of the proposed actuation system and traditional hydraulic cylinder are analysed and compared. The results show that the proposed system exhibits better following performance. Subsequently, the SIMPACK-SIMULINK co-simulation results indicate that the system can realize an effective primary longitudinal suspension; further, in the active radial mode, the performance indexes of vehicle curve passing are significantly improved. These findings provide a reference for the engineering implementation of active radial technology.

A New Type of Rotary Magnetic Actuator System Using Electromagnetic Vibration and Wheel

In recent years, large structures, such as bridges, which are a type of social infrastructure, have been constructed with increasing traffic volume. For this reason, inspection and maintenance of social infrastructures, such as large bridges and tanks, is important. In the present paper, a magnetic wheel actuator system capable of movement using a new principle of locomotion was proposed and tested. The experimental results indicated a maximum pulling force of 1.6 N. By on-off control of the attractive force of the magnetic wheel, the actuator system was demonstrated to be able to move on a step having a height of 10 mm. Furthermore, the proposed actuator system could freely rotate in horizontal and vertical planes of over angles of 360°.

Next Generation Autofocus and Optical Image Stabilization System for Camera Modules Using Magnetic Shape Memory Actuators

Currently, camera modules are used in a wide range of applications ranging from micropo-sitioning actuator systems used in smartphones to larger modules used in stationary cameras, CCTV, and others. Modern camera modules are required to perform positioning functions to improve the stability and quality of captured images. These functions mainly include the autofocus (AF) and optical image stabilization (OIS) functions. Traditionally, separate actuators and sensors are used for AF and OIS, each contributing towards energy consumption, module size, and manufacturing costs. This is particularly disadvantageous in the case of smartphones owing to their inherent space and battery charge limitations. This paper presents a novel Magnetic Shape Memory (MSM) actuator system that combines the AF and OIS functions, which are performed using two actuators; thus, this system is a simple, compact, and cost-effective solution to the drawbacks of conventional technology. Furthermore, the smart properties of MSM alloys reduce the energy consumption of these systems through the utilization of their inherent holding forces and the associated shape memory effect. The realization of AF and OIS functions is discussed and verified experimentally for the proposed actuator system using data obtained from a fabricated prototype.

Soft Elbow Exoskeleton for Upper Limb Assistance Incorporating Dual Motor-Tendon Actuator

Loss of muscle functions, such as the elbow, can affect the quality of life of a person. This research is aimed at developing an affordable two DOF soft elbow exoskeleton incorporating a dual motor-tendon actuator. The soft elbow exoskeleton can be used to assist two DOF motions of the upper limb, especially elbow and wrist movements. The exoskeleton is developed using fabric for the convenience purpose of the user. The dual motor-tendon actuator subsystem employs two DC motors coupled with lead-to-screw converting motion from angular into linear motion. The output is connected to the upper arm hook on the soft exoskeleton elbow. With this mechanism, the proposed actuator system is able to assist two DOF movements for flexion/extension and pronation/supination motion. Proportional-Integral (PI) control is implemented for controlling the motion. The optimized value of Kp and Ki are 200 and 20, respectively. Based on the test results, there is a slight steady-state error between the first and the second DC motor. When the exoskeleton is worn by a user, it gives more steady-state errors because of the load from the arm weight. The test results demonstrate that the proposed soft exoskeleton elbow can be worn easily and comfortably by a user to assist two DOF for elbow and wrist motion. The resulted range of motion (ROM) for elbow flexion–extension can be varied from 90° to 157°, whereas the maximum of ROM that can be achieved for pronation and supination movements are 19° and 18°, respectively.

A Novel Actuator System Combining Mechanical Vibration and Magnetic Wheels Capable of Rotational Motion Using Shape Memory Alloy Coils

In every country, large steel bridges, such as cable-stayed bridges, are actively being constructed, and the number of such bridges has been progressively increasing. These bridges are often inspected using drones, but inspection techniques have not been established because of strong winds and thunder. Therefore, robots capable of working in difficult environments are desired. In the present study, a prototype of a rotary actuator system combining two iron disks and two electromagnetic-vibration-type actuators was fabricated. A new operation principle was developed that drives the system using the reaction force of the vibration-type actuator. Two shape memory alloy coils and two friction pads were integrated into the system to enable it to carry out turning operations, which were successfully demonstrated. The proposed actuator system can thus move in any direction. In addition, with this actuator system, both slide-on-ceiling and wall-climbing motions are possible.

Design of a Twisted-String Actuator for Haptic Force Rendering

Abstract In this paper, the design of a Twisted-String Actuation (TSA) module suitable for a wide set of robotic applications is presented. The TSA module is characterized by an integrated force sensor based on optoelectronic components and embedded controller with power electronics. The proposed actuation system is particularly suited for very compact, light-weight, wearable and low cost robotic devices, such as haptic devices, wearable systems and rehabilitation exoskeletons. The whole module design and the basic force sensor working principle are illustrated and discussed. Particular attention is given to the integration of the force sensor into the TSA module to solve the drawbacks of previous solutions. Moreover, the structure of the TSA module electronics and embedded controller is presented. Finally, the actuation module has been experimentally tested, and the ability of the system of controlling the actuation force has been demonstrated.

An unconventional adaptive flutter suppression actuation system: From modeling to experimentation

This article contributes to the definition of an unconventional actuation system coupled with an adaptive control algorithm, it is intended specifically for slender/highly flexible wings flutter suppression. The design and validation process of the novel actuation architecture is presented together with the performance analysis of the post-flutter dynamics control. Robustness of the overall control architecture is verified with respect to the uncertainties deriving from the unpredictable degradation of the structural properties. The proposed actuation system is based on a row of multiple mini-spoilers, located in proximity of the leading edge and coordinated by a modified model reference adaptive control algorithm. The spoiler configuration is optimized by computational fluid dynamics numerical simulation, whereas the aerodynamic database is derived by wind tunnel tests on the prototype by means of a six-axes force balance. The resulting aeroelastic mathematical model is then used to implement and validate the adaptive control algorithm for a wide range of conditions, from on-design flutter speed and nominal structural stiffness to post-flutter speed and reduced structural stiffness. The two degree of freedom aeroelastic model is successfully controlled in all conditions. This article aims at defining a robust procedure for aeroelastic phenomena control system design, which employs a synergy of modeling, simulation, and experimental approaches. Pertinent conclusions are discussed in the final section of the article.

Design and Simulation of Three Degrees-of-Freedom Tracking Systems for Capsule Endoscope

Wireless capsule endoscopes (WCE) are a new technology for inspection of the intestines, which offer many advantages over conventional endoscopes, while devices currently in use are passive and can only follow the natural transit of the intestines. There is a considerable interest in methods of controlled actuation for these devices. In this paper, an actuation system based on magnetic levitation is proposed, utilizing a small permanent magnet within the capsule and an arrangement of digitally controlled electromagnet placed on a movable frame. The objective of this paper is to design a multi-input multi-output (MIMO), three degrees-of-freedom (3DOF) tracking system for capsule endoscope. Two techniques, entire eigenstructure assignment (EEA) and linear quadratic regulator (LQR), are presented to design the controller of the system. The performance of the EEA and LQR controllers was compared based on the stability parameters to validate the proposed actuation system. Finally, simulation results suggest that the LQR approach can be used to synthesize a suitable and simple controller for this application.

A Novel Electromagnetic Actuation System for Magnetic Nanoparticle Guidance in Blood Vessels

Targeted drug delivery using magnetic nanoparticles (MNPs) is a new therapeutic method and is being improved continually. However, recent improvements have focused mainly on the introduction and synthesis of special drugs and there are still limitations getting a drug to desired locations in the body, primarily owing to the small size of nanoparticles and the difficulty of controlling their movement in the body. This paper introduces a new electromagnetic actuation system for guiding MNPs in blood vessels. This system uses six electromagnets powered by currents that can generate a high-gradient magnetic field in the desired direction. A differential current coil (DCC) approach is used to calculate the current applied to each coil. Due to properties of the DCC approach, it is possible to use soft iron cores at the centers of the coils to amplify and concentrate the magnetic field in the desired region and generate a stronger magnetic force than the existing coil systems. To evaluate the performance of the actuation system, a model that guided nanoscale magnetic particles inside special channels was studied using commercial software. To improve the efficiency of the electromagnets for MNP guidance, the structural parameters of the cores and coils were chosen based on the simulation results to get the largest magnetic force in the region of interest, which was set as size of the mouse brain. The proposed actuation system is very compact and less expensive than previous systems. Furthermore, the simulation results demonstrated that the actuation system can generate adequate magnetophoretic forces for nanoparticle steering in a Y-shaped vascular model and can be potentially used as a propulsion tool for MNP guidance in blood vessels.

A New Actuator System Using Dual-Motors and a Planetary Gear

This paper proposes a new actuator system for mobile robot applications. Since the actuator system to be proposed consists of dual-motors and a planetary gear, it is referred to as the dual-motor system using a planetary gear (DuPG) in this paper. The suggested DuPG improves the speed-torque performance by combining two motors with one planetary gear, in which one motor is for high speed and the other for high torque. In other words, it is able to realize a high speed at low torque, and high torque at low speed, as an automatic transmission operates in an automobile. The proposed actuator system is able to extend the speed/torque operation region. Finally, several experimental results are suggested to show a few advantages such as the extended speed/torque operation region and the enhanced energy efficiency.

A New Actuation System With Simulated Electrocardiogram Signal for MR Elastography

Elasticity is an important physical attribute of biological tissue. Elasticity of normal tissue can differ significantly with pathological tissue in its stiffness. It is important to develop a clinical viable method to determine and visualize the elasticity of histological tissue. Magnetic resonance (MR) elastography is a promising noninvasive method to quantitatively measure the viscoelastic properties of biological tissue. We developed a new quasi-static actuation system with the spatial modulation of magnetization (SPAMM) imaging pulse sequence. The MR compatible actuation system consists of an ultrasonic motor, a force sensor, motion-transmission mechanism, ECG signal generation, and controller. The high torque ultrasonic motor, USR60-E3 by Shinsei Corporation, Japan, can function well in the magnetic environment. The simulated ECG signal is generated using function generator, and outputted to both MR scanner and controller respectively. SPAMM imaging sequence is utilized to acquire tagging images of the deformed tissue. The actuation is synchronized with the SPAMM sequence via simulated ECG signal. Indentation force is measured by MR compatible force sensor for the subsequent stiffness inversion procedure. Imaging experiments were conducted using this actuation system and a GE SIGNA 1.5T MR scanner. Clear tag-deformed images of agar gel phantom have been acquired. The results demonstrated the feasibility of utilizing SPAMM sequence and the proposed actuation system for tissue characterization. In comparison with dynamic method of MR elastography, this quasi-static method is relatively simple to implement since no motion sensitive gradient or gradient synchronization is required. A limitation of indentation method is the difficulty to obtain significant deformation of tumor inside the liver organ. Since radio frequency (RF) needle is inserted into liver organ during tumor ablation, the proposed system with needle-based actuation making use of this inevitable insertion will be able to intra-operatively image the liver tumor during ablation. The RF needle can directly vibrate the pathological tissue within the liver organ.

Robot-assisted endoscopic exploration of the spinal cord

This work presents the design and development of an integrated image-guided robot-assisted endoscopic system for the safe navigation within the spinal subarachnoid space, providing the surgeon with the direct vision of the structures (i.e. spinal cord, roots, vessels) and the possibility of performing some particularly useful operations, like local electrostimulation of nerve roots. The modelling, micro-fabrication, fluidic sustentation, and cable-based actuation system of a steerable tip for a multilumen flexible catheter is described; the hierarchical control system shared between the surgeon and the computer, and based on machine vision techniques and a simple but effective three-dimensional reconstruction is detailed. The Blind Expected Perception sensory-motor scheme is proposed in robot-assited endoscopy. Results from in vitro, ex vivo, and in vivo experiments show that the described model can accurately predict the shape of the catheter given the tension distribution on the cables, that the proposed actuation system can assure smooth and precise control of the catheter tip, that the fluidic sustentation of the catheter is essential in in vivo navigation, and that the proposed rear view mirror interface to show non-visible obstacles is appropriate; in conclusion, the results proved the validity of the proposed solution to develop an intrinsically safe robotic system for navigation and intervention in a narrow and challenging environment such as the spinal subarachnoid space.

Design and Control of a Multi-jointed Robot Finger Driven by an Artificial Muscle Actuator

In this paper, we present a robotic actuation system using an artificial muscle actuator based on a dielectric elastomer. A novel linear actuator called a 'multi-stacked actuator' is proposed that can be embedded in the phalanges of a multi-jointed robot finger. This actuator ensures a compact design of the overall system. As an example, a 2-d.o.f. robot finger is developed and its performance under the proposed actuator system is experimentally demonstrated. The application of the proposed system can be extended easily to a multifingered robot hand and even to articulated mechanisms such as legged robots, etc.

A novel design of active accelerator pedal using linear electromagnetic actuator

This paper describes a novel design of an active accelerator pedal(AAP) using a linear electromagnetic actuator that transfers warning messages recognized by the automobile from the sensors to the driver. In an emergency driving situation, the electromagnetic actuator creates additional pedal forces such as active pedal force and vibration force. In a passive situation however, the actuator does not produce additional force. In the past, a system with a rotary actuator was developed for AAP but was found to have critical drawbacks such as inaccurate movement by backlash and torque occurrence due to the high gear ratio. This research, therefore, aims to solve these drawbacks and maximize car safety by optimizing the electromagnetic linear actuator. Finite element analysis is performed to analyze the coupled system of electric, magnetic, and mechanical subsystems, and to characterize the dynamic performance of the proposed actuator system. A novel design of the AAP system with the optimized electromagnetic linear actuator is developed. The dynamic characteristics of the AAP system are simulated by a 3D dynamic analysis software program. Satisfactory results were obtained. Finally, the test result and the simulation result of the AAP system are compared.

Design and Control of Multi–jointed Robot Finger based on Artificial Muscle Actuator.* *This research was financially supported by the Ministry of Knowledge Economy(MKE) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource Training Project for Strategic Technology, Korea. All correspondences are to be sent to Prof. Choi at hrchoi@me.skku.ac.kr

A new biomimetic actuation system by artificial muscle actuator based on dielectric elastomer is presented in this paper. A novel linear actuator called “multi-stacked actuator” is introduced, which can be embedded in the phalanges of the finger and ensures a compact design of the overall system. The performance of the proposed actuation system is demonstrated using two degree–of–freedom robot finger. A pulse-width-modulation proportional-integral-derivative (PWM-PID) feedback controller based on the discharging circuit is implemented and tested. The proposed system can be extended to the multi–fingered robot hand easily, and applied even for articulated mechanisms such as legged robots etc.