Wire-driven Mechanism Research Articles

A Bioinspired Control Strategy Ensures Maneuverability and Adaptability for Dynamic Environments in an Underactuated Robotic Fish

Bioinspired underwater robots can move efficiently, with agility, even in complex aquatic areas, reducing marine ecosystem disturbance during exploration and inspection. These robots can improve animal farming conditions and preserve wildlife. This study proposes a muscle-like control for an underactuated robot in carangiform swimming mode. The artifact exploits a single DC motor with a non-blocking transmission system to convert the motor’s oscillatory motion into the fishtail’s oscillation. The transmission system combines a magnetic coupling and a wire-driven mechanism. The control strategy was inspired by central pattern generators (CPGs) to control the torque exerted on the fishtail. It integrates proprioceptive sensory feedback to investigate the adaptability to different contexts. A parametrized control law relates the reference target to the fishtail’s angular position. Several tests were carried out to validate the control strategy. The proprioceptive feedback revealed that the controller can adapt to different environments and tail structure changes. The control law parameters variation accesses the robotic fish’s multi-modal swimming. Our solution can vary the swimming speed of 0.08 body lengths per second (BL/s), and change the steering direction and performance by an angular speed and turning curvature radius of 0.08 rad/s and 0.25 m, respectively. Performance can be improved with design changes, while still maintaining the developed control strategy. This approach ensures the robot’s maneuverability despite its underactuated structure. Energy consumption was evaluated under the robotic platform’s control and design. Our bioinspired control system offers an effective, reliable, and sustainable solution for exploring and monitoring aquatic environments, while minimizing human risks and preserving the ecosystem. Additionally, it creates new and innovative opportunities for interacting with marine species. Our findings demonstrate the potential of bioinspired technologies to advance the field of marine science and conservation.

High-strength and flexible mechanism for body weight support

Wearable body weight support systems can assist individuals with mobility impairments in performing daily living activities with greater ease and independence. However, existing systems have limitations in terms of balancing their strength, compact size, interaction with the ground, and driving. In this paper, we present the High-Strength and Flexible Mechanism (HSFM) designed for body weight support. The HSFM utilizes a coiling truss mechanism to perform flexible transformation between a straight and spiral shape. Its complex linkages create the mechanical constraints of the structure and enhance its stiffness. Additionally, the HSFM achieved a high extension rate, effective wire-driven mechanism, and smooth shift of the grounding point. We provide a detailed description of the HSFM, including the simplest 4-linkage mechanism, its mechanical constraints, and the wire-driven mechanism. Moreover, we conducted parametric analysis and geometric calculation on the link structure. The results justified the mechanical constraints of the HSFM and ensured the high extension rate. Further, its functionality for body weight support was evaluated with the hardware and showed sufficient results in terms of strength, smooth grounding, and wire-driven. This novel mechanism has the potential to develop a wearable body weight support robot enhancing daily living activities such as sit-to-stand transfer and walking.

Kinematic and hydrodynamic modeling of a wire-driven robotic fishtail: An experimental study

Robotic fish have been extensively developed for scientific research and engineering applications, with the robotic fishtail serving as a crucial component. Due to the complex deformation mechanism and hydrodynamic interaction, it remains a significant challenge to establish a real-time precise kinematic and hydrodynamic model for flapping robotic fishtails. This paper presents a kinematic and hydrodynamic model for a wire-driven robotic fishtail, incorporating experimental investigation. The wire-driven mechanism featuring a continuously compliant backbone and position-variable vertebrae is developed, enabling more flexible fishtail flapping and adjustable fish morphology. The kinematic and hydrodynamic models are established through the quasi-static method with proposed corrections accounting for flapping velocity and nonlinear backbone deformation during a flapping stroke, precisely assessing real-time hydrodynamic responses. The proposed models have been validated through physical tests in an open-water environment, and exhibit superior response predictive ability compared to traditional methods. A significant force peak is observed at the beginning of a flapping stroke, while small amount of reversed thrust occurs at its end. In a high-frequency flapping motion, the soft caudal fin generates greater thrust than a hard fin. Comprehensively, this study presents a systematic research methodology for modeling and experimental investigation of novel robotic fishtails and biomimetic propellers.

Miniature camera module with a hollow linear ultrasonic motor-based focus feature

The construction of a miniature camera module that can explore inside limited spaces is of great interest for the design of millimeter-scale devices, such as endoscopes. This article presents a miniature camera module with a focus feature using a hollow linear ultrasonic motor. The hollow stator, which is simplified by the expansion and thickness-shear piezoelectric effects, is suitable for the miniaturization of the camera module because it can contain a lens group. The linear slider, which is thin and cylindrical with a slit, is inserted into the stator’s hole and generates a preload that exploits optimal motor performance measures. The resultant camera module is 4.6 mm × 4.6 mm square, which is the smallest one of camera modules reported to date. The motion of the miniature camera module is demonstrated by the wire-driven mechanism and a visual feedback control system. The orientation of the camera module head is controlled by a wire-driven mechanism until the target object is set in the range of view. The lens group placed inside the slider is controlled by the hollow linear ultrasonic motor in a visual feedback-loop system.

Development of a Novel Underactuated Robotic Fish with Magnetic Transmission System

In this study, a robotic fish inspired to carangiform swimmers has been developed. The artifact presents a new transmission system that employs the magnetic field interaction of permanent magnets to ensure waterproofness and prevention from any overload for the structure and the actuating motor. This mechanism converts the rotary motion of the motor into oscillatory motion. Such an oscillating system, along with the wire-driven mechanism of the tail, generates the required traveling wave in the robotic fish. The complete free swimming robotic fish, measuring 179 mm in length with a mass of only 77 g, was able to maintain correct posture and neutral buoyancy in water. Multiple experiments were conducted to test the robotic fish performance. It could swim with a maximal speed of 0.73 body lengths per second (0.13 m/s) at a tail beat frequency of 3.25 Hz and an electric power consumption of 0.67 W. Furthermore, the robotic fish touched the upper bound of the efficient swimming range, expressed by the dimensionless Strouhal number: 0.43 at 1.75 Hz tail beat frequency. The lowest energy to travel 1 meter was 4.73 Joules for the final prototype. Future works will focus on endowing the robot with energy and navigation autonomy, and on testing its potential for real-world applications such as environmental monitoring and animal–robot interaction.

Basics of Wire-driven Mechanism using Synthetic Fiber Ropes and Their Application to Robots

In recent years, high-strength synthetic fiber ropes development has remarkably progressed. One of the ropes achieves two times higher tensile strength than a conventional stainless steel wire, while its weight is 1/5. Suppose we can utilize these synthetic fiber ropes as a wire-driven mechanism. In that case, it is possible to develop a high-performance robot mechanism that can not be achieved with conventional driving mechanisms. This paper introduces the basics of the wire-driven mechanism using synthetic fiber ropes and their application to robots developed by our research group.

Gravity and Impedance Compensation of Body Weight Support System Driven by Two Series Elastic Actuators

Robotic devices that can support human’s motions, such as exoskeletons, have recently drawn attention. Body weight support (BWS) systems are potential robotic devices that support and assist trunk motions with elaborate force control for rehabilitation and training exercises. This article presents a BWS system with 2-D motion assistance controlled by two series elastic actuators, which can perform not only weight compensation but also impedance compensation for trunk motion assistance. As the core technology of the proposed system, a wire-driven mechanism is developed that consists of a compact planetary-geared elastic actuator (cPEA), which is a series elastic actuator. All the dynamic aspects of the cPEA output torque, the tension-generating system using a winding drum, and the dynamics interacting with the BWS system are analyzed and used to design a motion-assistive controller. The functionality and ability of the proposed system are validated through experiments performed under various conditions. The results verify that the dynamic behavior of trunk motion can be assisted by the impedance control of the proposed BWS system. In particular, the inertial force required for the trunk motion can be reduced by the proposed BWS system.

Delta-Type Parallel Mechanism with Wire-Pulleys and Wire-Driven Mechanism for Spherical Wrist

Delta-Type Parallel Mechanism with Wire-Pulleys and Wire-Driven Mechanism for Spherical Wrist

Singular Wire-Driven Series Elastic Actuation with Force Control for a Waist Assistive Exoskeleton, H-WEXv2

This article presents a design of an electrically powered waist-assistive exoskeleton H-WEXv2 to reduce back-muscle fatigue and prevent back-injury of industrial workers. It utilizes a wire-driven mechanism based on a singular series elastic actuation to achieve system performances in aspect of cost, weight, operational time, and system endurance and maintainability for industrial feasibility. This proposed mechanism consisting of a ball screw drive and a series elastic actuator enables H-WEXv2 to accomplish better control maneuverability on powered flexion/extension while maintaining the advantage of allowing natural human walking with almost zero impedance. Also, to transfer torque determined by a high-level controller, a SEA force controller was implemented by measuring elastic displacements of installed spring elements at both hip joints. In order to evaluate the effectiveness of the developed robot installed with the proposed mechanism, electromyographic (EMG) signals of relevant muscles of ten subjects related to target waist motions were measured and compared for three cases: 1) wearing H-WEXv1, 2) wearing H-WEXv2, and 3) wearing nothing. Finally, the statistical analysis on acquired EMG signals verified the effectiveness of waist assistance provided by H-WEXv2.

A Leg Mechanism Using Bundled Wire Drive

Taking advantage of low friction of synthetic fiber rope, a new wire-driven mechanism called Bundled Wire Drive, in which multiple wires are bundled and share the same transmitting pathway, was proposed. Conventional wire-driven mechanism requires complicated structure consisting of many pulleys to relay joints, but it can be replaced with simple structure by using Bundled Wire Drive. We developed a leg mechanism which is light and has a wide range of motion using Bundled Wire Drive. We confirmed that torque transmission efficiency of Bundled Wire Drive used in the leg mechanism was sufficient for driving joints. Furthermore, we confirmed that load capacity of the leg mechanism was enough to be applied to a walking robot.

Control of an intended motion assist device using a parallel wire-driven mechanism

Control of an intended motion assist device using a parallel wire-driven mechanism

Analysis of kinematic dexterity and stiffness performance based on Spring’s wire-driven 4-SPS/U rigid‒flexible parallel trunk joint mechanism

Purpose The purpose of this paper is to propose a two-degrees-of-freedom wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism based on spring, in order to improve the robot’s athletic ability, load capacity and rigidity, and to ensure the coordination of multi-modal motion. Design/methodology/approach First, based on the rotation transformation matrix and closed-loop constraint equation of the parallel trunk joint mechanism, the mathematical model of its inverse position solution is constructed. Then, the Jacobian matrix of velocity and acceleration is derived by time derivative method. On this basis, the stiffness matrix of the parallel trunk joint mechanism is derived on the basis of the principle of virtual work and combined with the deformation effect of the rope driving pair and the spring elastic restraint pair. Then, the eigenvalue distribution of the stiffness matrix and the global stiffness performance index are used as the stiffness evaluation index of the mechanism. In addition, the performance index of athletic dexterity is analyzed. Finally, the distribution map of kinematic dexterity and stiffness is drawn in the workspace by numerical simulation, and the influence of the introduced spring on the stiffness distribution of the parallel trunk joint mechanism is compared and analyzed. It is concluded that the stiffness in the specific direction of the parallel trunk joint mechanism can be improved, and the stiffness distribution can be improved by adjusting the spring elastic structure parameters of the rope-driven branch chain. Findings Studies have shown that the wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism based on spring has a great kinematic dexterity, load-carrying capacity and stiffness performance. Research limitations/implications The soft-mixed structure is not mature, and there are few new materials for the soft-mixed mixture; the rope and the rigid structure are driven together with a large amount of friction and hindrance factors, etc. Practical implications It ensures that the multi-motion mode hexapod mobile robot can meet the requirement of sufficient different stiffness for different motion postures through the parallel trunk joint mechanism, and it ensures that the multi-motion mode hexapod mobile robot in multi-motion mode can meet the performance requirement of global stiffness change at different pose points of different motion postures through the parallel trunk joint mechanism. Social implications The trunk structure is a very critical mechanism for animals. Animals in the movement to achieve smooth climbing, overturning and other different postures, such as centipede, starfish, giant salamander and other multi-legged animals, not only rely on the unique leg mechanism, but also must have a unique trunk joint mechanism. Based on the cooperation of these two mechanisms, the animal can achieve a stable, flexible and flexible variety of motion characteristics. Therefore, the trunk joint mechanism has an important significance for the coordinated movement of the whole body of the multi-sport mode mobile robot (Huang Hu-lin, 2016). Originality/value In this paper, based on the idea of combining rigid parallel mechanism with wire-driven mechanism, a trunk mechanism is designed, which is composed of four spring-based wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism in series. Its spring-based wire-driven 4SPS/U rigid‒flexible parallel trunk joint mechanism can make the multi-motion mode mobile robot have better load capacity, mobility and stiffness performance (Qi-zhi et al., 2018; Cong-hao et al., 2018), thus improving the environmental adaptability and reliability of the multi-motion mode mobile robot.

Bundled Wire Drive: Proposal and Feasibility Study of a Novel Tendon-Driven Mechanism Using Synthetic Fiber Ropes

This letter proposes a new wire-driven mechanism in order to relay many ropes very simply and compactly. Ropes pass through in a joint while bundled. Synthetic fiber rope can slide and twist, exploiting its low friction coefficient. In order to use this mechanism, it is necessary to investigate the influence of sliding on tension transmission efficiency and rope strength. The results of this study reveal that it is feasible for a robot arm using this mechanism to have more than 15 joints. Sliding has little influence on the rope strength. The feasibility of this system was studied through hardware experiments, and its mechanical performance was evaluated by constructing a horizontally extendable manipulator with three degrees of freedom.

Development of a Robot Hand Using Shape Memory Gel and Wire-Driven Mechanism

Development of a Robot Hand Using Shape Memory Gel and Wire-Driven Mechanism

Assistance device for positioning of forearm with a parallel wire-driven mechanism

Assistance device for positioning of forearm with a parallel wire-driven mechanism

A Biarc Method for Kinematics and Configuration Planning of Concentric Wire-Driven Manipulators

Concentric wire-driven mechanism (CWM) contains two nested tendon/cable-driven mechanisms (TMs). In the CWM, the lengths of the bending sections are controlled by the insertion of the TMs. This greatly expands the workspace and improved the trajectory following performance. However, its inverse kinematics and configuration planning are very challenging. Conventionally, only end position (excluding equally important end direction and task configuration) is considered to solve inverse kinematics and configurations of this type of manipulator. In this paper, a biarc method is proposed to resolve end position, end direction, and task configuration simultaneously for the concentric wire-driven manipulator. Firstly, configuration of the concentric wire-driven manipulator is parameterized by typical biarc parameters, such as total bending angle of outer nodes, total bending angle of inner nodes and desired direction vector. Then, task configuration optimization based on basic module parameters, end direction, and bending angle is detailed. Corresponding to a minimally invasive surgery, configurations can easily be designed and re-planned by adjusting above biarc parameters. Finally, trajectory tracking on large intestine examination through typical `S' configuration are simulated and experimented on the designed concentric wire-driven manipulator. Results demonstrate that the proposed method can provide reasonable solutions of kinematics and configuration planning. In addition, results also demonstrate that the concentric wire-driven manipulator can track desired trajectory in extremely confined space.

A Passive Snake-like Arm Based on Wire-driven Mechanism for Laparoscopic Surgery

In this paper, a passive snake-like arm based on wire-driven mechanism is proposed, which can be connected with remote center of motion (RCM) mechanism to form a laparoscope-holder robot and be used in laparoscopic surgery. The purpose of the snake-like arm is to replace traditional multi-joint manipulator, making it possible for the robot to assist the surgeon in the best position in a surgery. The snake-like arm consists of a main body composed of four arm units and a wire locking device with 12 wire locking units. The arm units are connected by hook hinges. Four classes force amplificatory structure is adopted in the wire locking unit. The detail structure and working principle of the wire locking device are proposed in this paper. The wire tensioning and guiding mechanism as well as the layout of wires are also introduced in this paper. Mechanical calculation of the force amplicatory structure is proposed in this paper to ensure that sufficient locking force can be provided. The workspace of the snake-like arm is drawn by simulation, and the large workspace allows the snake-like arm to be used in most laparoscopic surgeries.

Development of a Robot Hand Using Shape Memory Gel and Wire-Driven Mechanism

Development of a Robot Hand Using Shape Memory Gel and Wire-Driven Mechanism

Robot fish with two-DOF pectoral fins and a wire-driven caudal fin

This paper presents a robot fish with a wire-driven caudal fin and a pair of pectoral fins. First, the design of the robot fish is presented. The caudal fin is driven through wire-driven mechanism. The pectoral fins can perform two degrees-of-freedom motions, i.e. flapping (roll) and feathering (pitch). The pectoral fins can move in labriform mode for propulsion, or for other purposes such as turning and diving. Second, the propulsion analysis models for caudal fin propulsion and pectoral fins propulsion are derived. Finally, three types of experiments are conducted. Experiment results show that the swimming speed of caudal fin propulsion and pectoral fin propulsion match the model predictions. Moreover, with the caudal fin propulsion alone, the robot fish can swim up to 0.66 BL/s (body length/second); with the pectoral fin propulsion alone, the robot fish can swim up to 0.26 BL/s. The pectoral fins can significantly improve the maneuverability of the robot fish. Without using the pectoral fins, the turning radius of the robot fish is 0.6 BL; with the pectoral fins, the turning radius is reduced to 0.25 BL.

ワイヤー式衝撃緩和機構を搭載した人間共存型ロボットの研究

ワイヤー式衝撃緩和機構を搭載した人間共存型ロボットの研究