Rotary Actuator Research Articles

Improvement of tracking performance of SMA-actuated rotary actuator via thermocouple delay compensation using adaptive predictor

This paper investigates the impact of bounded and unknown delay of a J-type thermocouple sensor on controlling a Shape Memory Alloy (SMA) actuated rotary actuator. To compensate for the delay, a nonlinear adaptive predictor is utilized, which predicts the exact temperature of the present moment using the output of the sensor. A robust sliding mode control is then designed to track the reference input, which is the rotation angle of the pulley. In addition to temperature estimation, the inner system identification algorithm of the predictor identifies the heat transfer coefficients of the experimental setup. Experimental tests demonstrate the precise control of the proposed algorithm. The tracking error of the adaptive predictor with sliding mode control is compared to that of a regular sliding mode controller without temperature delay compensation consideration, showing the superior performance of the proposed control algorithm.

Soft yet secure: Exploring membrane buckling for achieving a versatile grasp with a rotation-driven squeezing gripper

Nowadays, there is a growing demand for versatile robotic grippers that facilitate adaptive grasping across a range of objects, characterized by diverse attributes such as shapes, sizes, and mechanical properties. This research introduces a new soft gripper, denoted as ROSE (ROtation-based Squeezing GrippEr), dedicated to the torsional buckling phenomenon to achieve its grasping capability. The inherent gripping pattern, formed through a single rotational actuation, enables ROSE to dynamically accommodate various objects (relatively smaller than the diameter of ROSE), even in challenging environments like an oil container, without a complicated controller. Experimental tests demonstrate that ROSE exhibits substantial gripping force, reaching up to more than 300 N in the specific setup, and a remarkable payload-to-weight ratio. Especially, ROSE can maintain mechanical integrity through long-term open-close operation cycles in a specific condition. In this paper, we also introduce non-linear simulations for the elaboration of behaviors of ROSE concerning different morphologies, encompassing geometry configurations and material properties. The findings highlight a significant correlation between morphological features and grasping performance, leading to the refinement of a dependable version of ROSE. This refined version was subsequently assessed through experimental trials in crop harvesting tasks, where ROSE demonstrated high success rates in picking both individual and clustered crops, regardless of their soft or stiff characteristics. Project’s website with videos: https://sites.google.com/view/rosesoftgripper .

A new design and analysis of low-profile soft rotary pneumatic actuator for enhanced rotation and torque

Soft actuators producing bending motions have gained significant attention for their advantages in mimicking the properties and movements of human muscles. However, the research on soft rotary actuators has yet to keep pace with other soft actuators. This paper makes two key contributions to the design and modeling of these actuators. First, we introduce a novel design for a soft rotary pneumatic actuator. This design outperforms existing cylindrical shaped soft actuators, especially in terms of torque. Second, we present an analytical model based on finite deformation. This model accurately describes the relationship between rotational movement and corresponding torque. The accuracy of this model is validated through Finite Element Method (FEM) simulations and corresponding tests. By providing a mechanically efficient design and a highly accurate analytical model, this work offers a comprehensive solution for the development of new soft pneumatic actuators.

Active Disturbance Rejection Control of Hydraulic Quadruped Robots Rotary Joints for Improved Impact Resistance

Hydraulic actuated quadruped robots have bright application prospects and significant research values in unmanned area investigation, disaster rescue and other scenarios, due to the advantages of high payload and high power to weight ratio. Among these fields, inevitable collision of robots may occur when contact with unknown objects, step on empty objects, or collapse, all of which have an impact on the working hydraulic system. To overcome the unknown external disturbances, this paper proposes an active disturbance rejection control (ADRC) strategy of double vane hydraulic rotary actuators for the hip joints of the quadruped robots. Considering the order of the valve-controlled actuator model, a three-stage tracking differentiator, a four-stage extended state observer, and a state error feedback controller are designed relatively, and the extended state observer is adopted to observe and compensate the uncertainty of external load torque of the system. The effectiveness of the ADRC method is verified in simulation environment and a single joint experimental platform. Moreover, the impact experiments of the limb leg unit are carried out after introducing the proposed ADRC strategy into hip joint, the limb leg unit of quadruped robots presents better impact resistance ability.

Decreasing the non-linearity of hybrid reluctance actuators by air gap design

This paper presents an air gap design approach to improve the linearity of rotational Hybrid Reluctance Actuators (HRAs) used in fast steering mirrors. The approach involves modeling a one-degree-of-freedom HRA with a magnetic equivalent circuit to identify and analyze sources of non-linearities. On the basis of the verified model, solutions for an improved linear system behavior are analytically searched. Two linearized HRA designs are proposed, one with linear cross-section dependency and the other with hyperbolic air gap length dependency. Finite element method simulations are employed to evaluate the performance with respect to the linearity and the motor constant of these designs, showing factor 50 improved system linearity.

An Integrated MCDM Framework for Optimizing Rotary Actuator Selection in Smart Robotic Power Wheelchair Prototypes

An Integrated MCDM Framework for Optimizing Rotary Actuator Selection in Smart Robotic Power Wheelchair Prototypes

Design and Characterisation of a 3D-Printed Pneumatic Rotary Actuator Exploiting Enhanced Elastic Properties of Auxetic Metamaterials

Design and Characterisation of a 3D-Printed Pneumatic Rotary Actuator Exploiting Enhanced Elastic Properties of Auxetic Metamaterials

Investigation on Melting Process of Finned Thermal Energy Storage with Rotational Actuation

Investigation on Melting Process of Finned Thermal Energy Storage with Rotational Actuation

Dynamic control simulation of a new joint model with energy recovery during walking, using magnetorheological fluids, for lower limb prosthesis

AbstractResearchers can now utilize new materials to create innovative models for lower limb prostheses and explore novel ways to use them for efficient dynamic control. To achieve user-friendliness, one area of research focuses on recovering and reusing kinetic walking energy for dynamic control. This paper proposes a new design for a magnetorheological (MR) valve, along with a rotary actuator which offers a dynamic control for a lower limb prosthesis. The design will allow the storage of the energy during heel and mid-foot contact phases and to utilize it during toe support to lift the foot off the ground and establish a balance for the lower limb prosthesis. The energy is transferred through a magnetorheological hydraulic circuit and stored using a pneumatic system. The speed of energy transfer is regulated by magnetorheological valves. A series of MR valve designs were proposed and evaluated experimentally, which allowed the identification of the most suitable variant in the targeted application context. The design of the lower limb prosthesis was simulated using SolidWorks, and its dynamic behavior was analyzed in ANSYS.

Modular reconfigurable rotary style soft pneumatic actuators

Modular soft robots have the advantage in their ability to be reconfigured and change their morphology on-demand according to a specified task. The actuator design and particularly the inter-unit connectivity strength commonly govern the usability and functionality of these modular robots and their applications. In this paper, we present development of reconfigurable modular rotary soft actuators that allow the construction of highly versatile soft robotic actuators and systems. These pneumatically driven modular actuators are composed of an inner balloon and a flexible arched reinforcement structure to produce a rotary motion. They serve as building blocks which may be combined in various configurations to construct linear assemblies capable of extensile or bending motions. The connection scheme allows for the larger actuators to grow or shrink with the addition or removal of modules. Using finite element simulations and physical characterizations, we systematically explore the mechanical response of individual modular actuators and the role of various connection schemes on their motions upon pressurization. A key conceptual contribution of this work lies in the idea that for a modular soft robotic system, offsetting and tuning actuator alignment relative to an axis of symmetry can lead to substantial changes in mechanical performance. Utilizing these modules we demonstrate the reconfigurability of this modular system by both reconfiguring a large actuator into a pair of smaller actuators that can grasp delicate objects, and reconfiguring actuators to develop a linear crawling robot.

Reliability and robustness of a novel preclinical torsional wave-based device for stiffness evaluation

In this work, we present a novel preclinical device utilizing Torsional Wave Elastography (TWE). It comprises a rotational actuator element and a piezoceramic receiver ring circumferentially aligned. Both allow the transmission of shear waves that interact with the tissue before being received. Our main objective is to demonstrate and characterize the reliability, robustness, and accuracy of the device for characterizing the stiffness of elastic materials and soft tissues. Experimental tests are performed using two sets of tissue mimicking phantoms. The first set consists of calibrated CIRS gels with known stiffness value, while the second test uses non-calibrated manufactured phantoms. Our experimental observations show that the proposed device consistently and repeatably quantifies the stiffness of elastic materials with high accuracy. Furthermore, comparison with established techniques demonstrates a very high correlation (> 95%), supporting the potential medical application of this technology. The results obtained pave the way for a cross-sectional study aiming to investigate the correlation between gestational age and cervical elastic properties during pregnancy.

Adaptive second-order backstepping control for a class of 2DoF underactuated systems with input saturation and uncertain disturbances

An adaptive second-order backstepping control algorithm is proposed for a kind of two degrees of freedom (2DoF) underactuated systems. The system dynamics is transformed into a nonlinear feedback cascade system with an improved global change of coordinates. Fully taking the cascade structure into consideration and in order to simplify the design process, each step in the backstepping process is designed for a second-order subsystem. Two neural networks are applied to approximate system unknown functions and two adaptive laws are designed to estimate the upper bound of the sum of approximation error and external disturbances. To overcome the explosion problem of complexity, a second-order filter is applied to produce the virtual control and its second-order derivative that is needed in the next backstepping step. Two auxiliary dynamic systems are proposed and integrated into the backstepping process to eliminate the effects of filtering error and input saturation. The system stability is analyzed by the Lyapunov stability theory and verified by numerical simulations with two 2DoF benchmark underactuated systems: the translational oscillator with a rotational actuator (TORA) and the inertial wheel pendulum (IWP).

On the analysis and control of a bipedal legged locomotion model via partial feedback linearization

In this study, we introduce a new model for bipedal locomotion that enhances the classical spring-loaded inverted pendulum (SLIP) model. Our proposed model incorporates a damping term in the leg spring, a linear actuator serially interconnected to the leg, and a rotary actuator affixed to the hip. The distinct feature of this new model is its ability to overcome the non-integrability challenge inherent in the conventional SLIP models through the application of partial feedback linearization. By leveraging these actuators, our model enhances the stability and robustness of the locomotion mechanism, particularly when navigating across varied terrain profiles. To validate the effectiveness and practicality of this model, we conducted detailed simulation studies, benchmarking its performance against other recent models outlined in the literature. Our findings suggest that the redundancy in actuation introduced by our model significantly facilitates both open-loop and closed-loop walking gait, showcasing promising potential for the future of bipedal locomotion, especially for bio-inspired robotics applications in outdoor and rough terrains.

Permanently magnetized elastomer rotating actuator using traveling waves

We report a soft actuator that generates continuous rotation of an object placed on it by electromagnetically exciting circular travelling waves in a soft disk. The disk, that serves as the stator, is made of a stretchable composite consisting of segments of silicone elastomer in which hard ferromagnetic particles are embedded. Inspired by piezoelectric traveling wave rotary actuators, the disk’s 16 sections are driven by underlying printed circuit board coils to create a flexural traveling wave on the disk’s surface. The rotor can be any object directly placed on the stator: the traveling wave in the stator leads by friction to the rotation of the rotor. Unlike conventional electromagnetic motors that rely on a precisely controlled gap between stator and rotor, a concept incompatible with soft robotics, our device exploits the contact between rotor and stator and the associated dry friction to generate torque. Rotation speeds of over 6 rpm were obtained for a partially rice-filled balloon, 30 cm diameter, weighing 17 g. We report detailed speed and performance metrics when rotating plastic disks. With this rotating actuator, we demonstrate an innovative way to transmit torques and rotations within soft structures.

Tolerance analysis of slat gear rotary actuator in civil aircraft

Abstract The slat gear rotary actuator of civil aircraft needs to meet the requirements of small space and large transmission ratio. The planetary gear system based on triple teeth is a common actuator design, and the design structure is complex, so its tolerance control is also strict. In order to meet the design requirements of its internal structure, this paper presents a deviation analysis method for the internal structure design of a typical civil aircraft slat gear rotary actuator. The results of preliminary tolerance distribution and improved tolerance distribution are analyzed using the Jacobi-based assembly deviation model. By comparing the standard deviation of the analysis results, the validity of this deviation analysis method is verified, which proves that this method can be used to analyze the internal structure deviation of the rotary actuator of slat gear in civil aircraft.

Kinematic Modeling and Performance Analysis of a 5-DoF Robot for Welding Applications

Robotic manipulators are critical for industrial automation, boosting productivity, quality, and safety in various production applications. Key factors like the payload, speed, accuracy, and reach define robot performance. Optimizing these factors is crucial for future robot applications across diverse fields. While 6-Degrees-of-Freedom (DoF)-articulated robots are popular due to their diverse applications, this research proposes a novel 5-DoF robot design for industrial automation, featuring a combination of three prismatic and two revolute (2R) joints, and analyzes its workspace. The proposed techno-economically efficient design offers control over the robot manipulator to achieve any reachable position and orientation within its workspace, replacing traditional 6-DoF robots. The kinematic model integrates both parallel and serial manipulator principles, combining a Cartesian mechanism with rotational mechanisms. Simulations demonstrate the end effector’s flexibility for tasks like welding, additive manufacturing, and material inspections, achieving the desired position and orientation. The research encompasses the design of linear and rotational actuators, kinematic modeling, Human–Machine Interface (HMI) development, and welding application integration. The developed robot demonstrates a superior performance and user-friendliness in welding. The experimental work validates the design’s optimized joint trajectories, efficient power usage, singularity avoidance, easy access in application areas, and reduced costs due to fewer actuators.

Adaptive neural tracking control for flexible joint robot including hydraulic actuator dynamics with disturbance observer

AbstractIn this paper, a disturbance observer‐based adaptive neural backstepping integral sliding mode control (BISMC) is developed for a flexible joint robot (FJR) with the integration of an adjustable stiffness rotary actuator (ASRA). This system suffers from unknown system dynamics, external disturbance, and the influence of variable stiffness, which is a challenge for achieving precision tracking performance. Considering the lumped disturbances in FJR generated by the hydraulic system and the stiffness modulation of the ASRA, we investigate the structural dynamics nonlinear model of the FJR system, including hydraulic actuator dynamics. While other linear control strategies are applied for the FJR, the proposed controller uses BISMC, neural networks (NN), and nonlinear disturbance observers to deal with the disadvantages mentioned above. Radial basis function neural networks (RBFNN) are designed to tackle unknown nonlinear functions, and the disturbance observers are introduced to compensate for the influence of the variable stiffness, disturbance, and the approximation error caused by NN. Simulations and experiments are independently implemented to demonstrate the effectiveness and feasibility of the proposed controller. Results exhibit that the integral absolute error‐index is reduced by 20.4% when the proposed method is deployed for the experiment with a multistep trajectory.

Cornerstone for MRI-compatible robots: A continuous pneumatic actuator with easy-to-connect prismatic/revolute and bidirectional encoder modules

The exceptional imaging capability of magnetic resonance imaging (MRI) enables the applications of robot-assisted surgery under MRI guidance. Essential to these robotic systems are the MRI-compatible robotic joint actuators. Among various actuation methods using MRI-compatible materials, pneumatic actuators are considered the most suitable for this application scenario due to their sterility, safety, and reliability. Yet, the current pneumatic actuators are either bulky, inefficient, or cannot achieve accurate bidirectional continuous motion. As a step forward, a novel high-performance continuous MRI-compatible pneumatic motor is proposed, along with quick-connect revolute/prismatic motion output modules and high accurate bidirectional encoder modules. The high performance of the pneumatic rotary and linear actuators are evaluated through experimental testing, where the rotary actuator can provide up to 2 Nm of output torque and over 28 W of output power, while the linear variant can deliver over 50 N of thrust, which surpass the SOTA competitors. Corresponding dynamic models are established and verified via experiments, with a maximum error of only 2.01%. Closed-loop control experiments demonstrate the high control precision and fast response frequency of the proposed pneumatic actuators, promoting the performance of joint actuators of various MRI-compatible surgical robots.

A compact bimorph rotary piezoelectric actuator with customized small power supply

A compact bimorph rotary piezoelectric actuator with customized small power supply

Reconfigurable transmissive metasurface with a combination of scissor and rotation actuators for independently controlling beam scanning and polarization conversion

Polarization conversion and beam scanning metasurfaces are commonly used to reduce polarization mismatch and direct electromagnetic waves in a specific direction to improve the strength of a wireless signal. However, identifying suitable active and mechanically reconfigurable metasurfaces for polarization conversion and beam scanning is a considerable challenge, and the reported metasurfaces have narrow scanning ranges, are expensive, and cannot be independently controlled. In this paper, we propose a reconfigurable transmissive metasurface combined with a scissor and rotation actuator for independently controlling beam scanning and polarization conversion functions. The metasurface is constructed with rotatable unit cells (UCs) that can switch the polarization state between right-handed (RHCP) and left-handed circular polarization (LHCP) by flipping the UCs to reverse their phase variation. Moreover, independent beam scanning is achieved using the scissor actuator to linearly change the distance between the UCs. Numerical and experimental results confirm that the proposed metasurface can perform beam scanning in the range of 28° for both the positive and negative regions of a radiation pattern (RHCP and LHCP beams) at an operational frequency of 10.5 GHz.