Rotary Actuator Research Articles

Innovative solution for the LHD loader intended for operation in low workings of underground mines

The article presents the results of comparative numerical tests of typical operating systems of LHD loaders with a proprietary solution based on a patent. LHD loaders belong to the group of basic machines working in various operating systems, including room-and-pillar systems. Due to the thickness of the deposits, mining is frequently carried out in low workings. In the case of typical T-kinematic or Z-kinematic systems, the operation of LHD loaders is more difficult. Due to the low height of the excavation, the excavated material is loaded in several cycles. A smaller machine generates less thrust force, which also negatively affects loading efficiency. Additionally, there are typical operational problems associated with the use of hydraulic actuators, the piston rods of which are exposed to mechanical damage and loss of tightness. In the presented proprietary solution of the working system, the bucket is attached to a telescopic boom system moved by hydraulic rotary actuators (Saga et al., 2019). Moreover, the loader is equipped with spreaders to stabilize the machine. The use of rotary actuators and a lowered pivot point of the bucket, together with a telescopic arm and spreaders, allows the bucket to be loaded in one cycle. In the article, the results of simulation tests of three kinematic systems have been presented. The analysis included, among others, the movement of the bucket, the duration of the cycle, and the related demand for hydraulic oil, as well as the load on the most important structural elements and nodes. The research has shown that the proposed solution can successfully compete with classic systems in terms of load and oil demand while offering an advantage in terms of functionality.

A New Technique to Qualify Rotary Electro-Mechanical Actuator for Tactical Class of Missile System

A novel technique has been adopted to establish the functionality and to qualify the Rotary Electro-Mechanical Actuator (REMA) system developed for a typical tactical class of weapon system in addition to the conventional method of checking the functionality through On-Board Computer in-loop simulation, Actuator in-loop simulation and Hardware in-loop simulation. The REMA along with full scale fin surface subjected to wind tunnel tests at the actual flight Mach number and flight dynamic pressure conditions. Flight hardware of REMA and fin assembly has been used in the tests so as to derive direct conclusions without applying any corrections to the measured results. This technique revealed the capability of the actuator, the dynamic functionality of its components such as gear systems, bearings and structural integrity of the whole actuator under the flight aerodynamic load on the full scale fin surface and vibration environments. The test conducted is being the most critical condition and the REMA and fin combination performed the intended commands as predictable and survived without any structural dis-integrity qualifies for further flight use. Subsequently flight tests were conducted and found the performance of REMA was as anticipated. Based on these results, recommendation made that it is mandatory that the all the actuation systems developed for fin actuation in missiles has to undergo the wind tunnel tests and qualify further actual use. The details of wind tunnel tests and the results of typical REMA with full scale fin are presented in this paper.

Parametric sensitivity analysis of the friction coefficient of coated textured surface in the rotary vane actuator end seal

This paper utilizes the extended Fourier amplitude sensitivity test (EFAST) method to analyze the effects of varying speeds on the friction coefficient of the coated textured end seal surface in rotary vane actuators. The analysis focuses on the first-order, total, and coupled sensitivities of root mean square (RMS) roughness, texture depth, and texture area ratio. The accuracy and validity of the numerical simulations are experimentally verified. At low speeds (20 rpm), RMS roughness shows the highest first-order sensitivity, 1.247 and 2.181 times greater than texture depth and texture area ratio. Using Support Vector Regression and Particle Swarm Optimization, the optimal parameters were determined: an RMS roughness ofs 0.1012 μm, a texture area ratio of 77.99%, and a texture depth of 2.9601 μm. The model can also predict the friction coefficient for various parameter combinations at different speeds.

Novel Multipoint-drive Rotary Actuator for Extraterrestrial Celestial Ultrasonic Driller

Ultrasonic drilling has emerged as a prominent technique in extraterrestrial environments due to its advantageous features. However, its application in extraterrestrial sampling missions is constrained by challenges such as drilling, chip removal efficiency, and high and low temperature adaptability. Addressing these limitations, this study introduces a novel multi-point driven rotary helical longitudinal torsion horn. The initial phase involved a detailed analysis of the actuator’s structure and operational principle. Subsequently, the actuator’s vibration mode and elliptical motion trajectory were validated through finite element simulation. The study further explores a methodology for adjusting the parameters of the helical groove and the displacement amplitude of the impact head. Following the theoretical analysis, prototypes of the actuator and drill were fabricated. Their adaptability to high and low temperatures, as well as their output characteristics, were rigorously tested. Experimental results demonstrate that with an increase in temperature, the dynamic impedance of the actuator initially rises before decreasing, while the mechanical quality factor exhibits the opposite trend. Notably, the concurrent activation of points P1 and P2 significantly enhances the no-load speed, achieving a maximum of 506 revolutions per minute (r/min). Under conditions of power below 35 W and a drilling pressure of 10 N, the drilling speed achieved in basalt is 6.2 millimeters per minute (mm/min). The proposed multipoint-driven actuator can effectively improve the drilling and chip removal efficiency of the driller, which is an important application prospect in future extraterrestrial drilling missions.

A Comparative Analysis and Scoping Review of Soft–Rigid and Industrial Parallel Rigid Grippers

In this research, it is aimed to present a comparative analysis of soft–rigid industrial parallel rigid grippers to compare their technical capabilities and assess the potential for soft–rigid grippers to address the challenge of grasping fragile objects with various shapes and sizes. In this research, 24 soft–rigid grippers are first identified through a scoping review using the Web of Science database, capturing their technical features and performance. Providing a variable stiffness grasp (n = 9, 37.5%) and a limited grasp capability (n = 8, 33.3%) is the most common advantage and challenge, respectively, of soft–rigid grippers. Pneumatic actuators (n = 12, 50.0%), followed by tendon‐driven electric rotary actuators (n = 9, 37.5%), are the predominant actuators used for soft–rigid grippers. Soft–rigid grippers are found to have a lower output force‐to‐weight ratio (n = 9, median , standard deviation (σ) = 15.17) in comparison to industrial parallel rigid grippers (n = 63, , ), but can provide a larger range of motion (n = 20, , ). This is the first quantitative comparative analysis between industrial parallel rigid and soft–rigid grippers, enhancing the understanding of their status and prospects in industrial applications. Herein, a common approach is proposed to standardize reporting to facilitate benchmarking between research‐based and industrial grippers and highlight controlling soft–rigid grippers is an underexplored area that can enhance the technology's performance.

Modeling and Validation of the Sealing Performance of High-Pressure Vane Rotary Actuator

The EHRA (Electro-Hydraulic Rotary Actuator), using a vane rotary actuator, has the advantages of a high torque density and integration and is expected to become a joint actuator for robots. This research focuses on the sealing characteristics of various parts of a vane rotary actuator. The average Reynolds equation was used to analyze the leakage characteristics at the gap. A detailed theoretical analysis was conducted on the internal leakage mechanism of a vane rotary actuator using an X-ring as the dynamic seal for the rotor vane. According to the path of internal leakage, different sealing forms are considered as a series or parallel, and the Newton iteration method is used to obtain the total internal leakage characteristics of a vane rotary actuator. It was also considered that the deformation of the vane rotary actuator caused a thicker gap, leading to an increase in internal leakage. The calculation results are consistent with the experimental data. The analysis results indicate that when estimating the internal leakage of a vane rotary actuator, it is necessary to take the pressure of the high-pressure chamber and output shaft position as inputs. This research provides a reference for an analysis of the method of internal leakage for vane rotary actuators. It provides theoretical support for designing a vane rotary actuator with more minor internal leakage and a higher volumetric efficiency.

Design and modelling of a novel single-phase-driven piezoelectric actuator

Sandwich single-phase-driven piezoelectric actuators have attracted increasing interest owing to their simple control circuits, flexible designs, and high output forces. However, there are challenges in constructing a standing-wave driving mode for sandwich single-phase-driven rotary piezoelectric actuators and in achieving bidirectional driving as well as an integrated structural and functional design, which limit their applications. To address these issues and meet the demands of the joint drive, a novel sandwich single-phase-driven rotary piezoelectric actuator is proposed in this study. The actuator stator has a beam-ring configuration, with dual rotors effectively integrated with a preload adjustment mechanism to solve the contact-warping problem of the cantilever joint and achieve an integrated structural and functional design of the joint drive. The standing-wave rotation drive and steering functions are realized through the special design of modes and unique arrangement of the upper and lower driving teeth. To reveal the dynamic characteristics of the stator, a universal electromechanical coupling dynamic model for the torsional-bending composite vibration of sandwich piezoelectric actuators was developed for the first time using the transfer matrix method, and the correctness of the dynamic model was verified using a prototype of the proposed stator. Finally, the structural design feasibility of the proposed piezoelectric actuator was verified through performance evaluation experiments on the actuator prototype. The proposed sandwich single-phase-driven rotary piezoelectric actuator lays the technical and theoretical foundations for achieving simple, fast, efficient, and precise driving and control of robotic joints.

Snap-through mechanism of an elastic bimetal ring for rotary actuation

Smart materials responsive to stimuli and new rotary mechanisms have drawn much attention in recent years. This paper investigates a novel snap-through rotation mechanism of a thermal responsive bimetal ring confined inside the annular region constraint when subjected to the local curvature induced by thermal loading. The buckled ring has movable boundaries and keeps an invariant shape during the snap-through rotation so that it requires small energy input to drive the bistable transition. To uncover the elusive mechanism behind this intriguing snap-through phenomenon, a theory based on the bifurcation and energy principle is developed to predict the critical loading curvature and the critical loading temperature, which agrees with the experimental results. The effects of loading positions and the constraint width are studied and a map predicting the critical loading curvature with different geometrical parameters is demonstrated. The rotary buckled ring not only enables the bistable actuation, but also triggers various actuation applications such as the motor actuation and the pump actuation. Due to great advantages in terms of energy supply and actuation loading, this study exhibits great potential of the proposed snap-through mechanism in bistable structures and rotary actuation.

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.

Comparative Analysis of Two Robust Strategies for an Angular Velocity Control System

In this paper, a novel flow control strategy which is the inlet throttled pump was used to design an angular velocity control system for rotary actuator. Inlet throttled systems have good performance in addition to their high efficiency compared to traditional valve controlled systems. The flow in the proposed system is adjusted by a valve that is positioned at the pump inlet with the purpose of reducing the energy loses across the valve. This regulated flow is used then to control the actuator angular velocity. The system was modeled and the open loop stability and performance were studied. In order to improve the system performance, Robust-Proportional-Integral-Derivative (RPID) and structured singular value (Mu) controllers have been designed. The multiplicative uncertainty was analyzed to assess the robustness of the feedback control system where six parameters were considered uncertain within a range of +10%. The robust stability and performance requirements of the closed-loop angular velocity control system were assessed in the frequency domain. The time response of the system showed that the system is stable with both (RPID) and (Mu) controllers. The Mu controller can handle parametric uncertainty without requiring pure integral term which is a significant advantage over the (RPID) controller. On the other hand, the (RPID) controller could achieve robust performance, making it much suitable for systems that require high levels of performance and robustness. In summary, the the (RPID) and Mu controller is a more comprehensive solution for ensuring the best performance of a system. The results for each (RPID) and Mu-controllers showed no oscillations, zero percent overshoot. Each of the (RPID) and Mu-controllers meets the robustness needs. Index Terms— Pump, valve, inlet throttling valve, angular velocity control, robust control, Mu synthesis, D-K iteration, RPID controller .

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.

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.

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

Phase-change thermal storage is essential for renewable energy utilization, addressing spatiotemporal energy transfer imbalances. However, enhancing heat transfer in pure phase-change materials (PCMs) has been challenging due to their low thermal conductivity. Rotational actuation, as an active method, improves heat transfer and storage efficiency. This study numerically examined the melting behavior of finned thermal storage units at various rotational speeds. The influence of speed was analyzed via melting time, rate, phase interface, temperature, and flow distribution. Results showed that rotational speed effects were non-monotonic: excessive speeds may hinder complete melting or reduce efficiency. There existed an optimal speed for the fastest melting rate and a limited speed range for complete melting. At the preferred rotation speed of 2.296 rad·s−1, the utilization of PCMs in a finned tube could mitigate the risk of local overheating by 97.2% compared to a static tube, while improving heat storage efficiency by 204.9%.

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.