Type Of Pneumatic Actuator Research Articles

A Comparison of Pneumatic Actuators for Soft Growing Vine Robots.

Soft pneumatic actuators are used to steer soft growing "vine" robots while being flexible enough to undergo the tip eversion required for growth. In this study, we compared the performance of three types of pneumatic actuators in terms of their ability to perform eversion, quasi-static bending, dynamic motion, and force output: the pouch motor, the cylindrical pneumatic artificial muscle (cPAM), and the fabric pneumatic artificial muscle (fPAM). The pouch motor is advantageous for prototyping owing to its simple manufacturing process. The cPAM exhibits superior bending behavior and produces the highest forces, whereas the fPAM actuates fastest and everts at the lowest pressure. We evaluated a range of dimensions for each actuator type. Larger actuators can produce more significant deformations and forces, but smaller actuators inflate faster and can evert at a lower pressure. Because vine robots are lightweight, the effect of gravity on the functionality of different actuators is minimal. We developed a new analytical model that predicts the pressure-to-bending behavior of vine robot actuators. Using the actuator results, we designed and demonstrated a 4.8 m long vine robot equipped with highly maneuverable 60 × 60 mm cPAMs in a three-dimensional obstacle course. The vine robot was able to move around sharp turns, travel through a passage smaller than its diameter, and lift itself against gravity.

Architectural gear ratio depends on actuator spacing in a physical model of pennate muscle.

Pennate muscles are defined by the architectural arrangement of their muscle fibers, which run at an angle to the primary axis of muscle shortening. Pennation angles can vary dynamically over the course of individual contractions, influencing the speed and distance of muscle shortening. Despite their relevance to muscle performance, the physical mechanisms that drive dynamic changes in pennation angle remain poorly understood. Muscle fibers bulge radially as they shorten, a consequence of maintaining a constant internal fluid volume, and we hypothesized that radial interactions between tightly packed muscle fibers are essential to dynamic pennation angle changes. To explore this, we built physical models of pennate muscles in which the radial distance between fiber-like actuators could be experimentally altered. Models were built from pennate arrays of McKibben actuators, a type of pneumatic actuator that forcefully shortens and bulges radially when inflated with compressed air. Consistent with past studies of biological muscle and engineered pennate actuators, we found that the magnitude of pennation angle change during contraction varied with load. Importantly, however, we found that pennation angle changes were also strongly influenced by the radial distance between neighboring McKibben actuators. Increasing the radial distance between neighboring actuators reduced pennation angle change during contraction and effectively eliminated variable responses to load. Radial interactions between muscle fibers are rarely considered in theoretical and experimental analyses of pennate muscle; however, these findings suggest that radial interactions between fibers drive pennation angle changes and influence pennate muscle performance. Our results provide insight into the fundamental mechanism underlying dynamic pennation angle changes in biological muscle and highlight design considerations that can inform the development of engineered pennate arrays.

Energy-to-Mass Ratio—A Novel Selection Criterion of Pneumatic Motors Used for the Actuation of Wearable Assistive Devices

The requirements to be met by a wearable assistive device are compactness, lightweight and energy efficiency. While the literature discusses the construction and performance of such devices, no information is provided as to the criteria to be applied in selecting such an actuator, capable of satisfying the mentioned conditions. Ensuring the high autonomy of a wearable assistive device requires actuators that can store a large quantity of energy in a small as possible volume, for example, actuators with a high energy density. This paper presents a comparative study of the performance of two types of pneumatic actuators: single-acting cylinders and pneumatic muscles, respectively, and offers information that will enable users to select an optimum solution. The quality indicators considered in conducting the comparative study are size, mass, the developed force and the energy-to-mass ratio. A method is proposed to determine the energy developed by the motors over the entire stroke; based on that, the energy-to-mass ratio is subsequently calculated. This indicator is a valuable tool made available to designers of wearable assistive devices. The conclusion yielded by the study asserts that while pneumatic muscles have larger radial and axial dimensions, they present benefits as to the developed forces and the energy-to-mass ratios.

Improved fuzzy sliding mode control in flexible manipulator actuated by PMAs

AbstractPneumatic muscle actuator (PMA) similar to biological muscle is a new type of pneumatic actuator. The flexible manipulator based on PMAs was constructed to simulate the actual movement of the human upper arm. Considering the model errors and external disturbances, the fuzzing sliding mode control based on the saturation function was proposed. Compared with other fuzzy control methods, fuzzy control and saturation function are used to adjust the robust terms to improve the tracking accuracy and reduce the high-frequency chattering.

Researches regarding the use of non-conventional actuators

The purpose of this article is to present relevant concepts about the study of electro-pneumatic circuits using fluidic muscle actuators. The fluidic muscle is a type of pneumatic actuator having an extensive history of technical applications in the biomechanical field since the 1955. After Introduction, the authors study two pneumatic circuits. In fact, the first pneumatic circuit in this paper has only one actuator (fluidic muscle 1-1), but the second pneumatic circuit has two actuators (fluidic muscles 2-1 and 2-2. Further on, the authors present two electro-pneumatic schematics, a simple electro-pneumatic circuit and another electro-pneumatic circuit with PLC (Programmable Logic Controller). This type of actuator is used in robotics, material handling, motion control, industrial field and other applications. The pneumatic and electro-pneumatic circuits given in this paper are made using FluidSim software from Festo. In this case, the fluidic muscles are only non-conventional actuators. However, in pneumatic installations as well as in electro-pneumatic installations, the non-conventional actuators have the following advantages: strength, compactness, reliability, low price, ease of assembly or disassembly from their circuits, etc. Of course, in practice are many types of fluidic muscles, which are used in electro-pneumatic installations.

Acoustic Length Sensor for Soft Extensible Pneumatic Actuators With a Frequency Characteristics Model

In this study, we present a length sensor that can be used for extensible soft pneumatic actuators. Conventional length sensors detect the changes in electrical resistance and capacitance owing to the deformation of the actuator; hence, deterioration and destruction occur when they are used with an actuator that has a large expansion ratio. In addition, their low resolution and linearity makes them unsuitable for use in actuator control. Our proposed sensor comprises only a speaker and a microphone installed at one end of the actuator. We propose a method to deterministically measure the length of a tube by generating a broadband acoustic signal in a tube and measuring the resonance characteristics determined by the shape of the tube. Our experimental results demonstrate that the error in the measurement with our sensor is not more than 4% with a strain up to 200%. Unlike conventional acoustic sensing methods that measure the time of flight by using ultrasound, our proposed method yields accurate results even when the tube is bent. Therefore, the proposed method can be applied to various types of pneumatic actuators.

COMPARATIVE SURVEY OF VARIOUS STATIC AND DYNAMIC MODELS OF PNEUMATIC ARTIFICIAL MUSCLES

A lesser known type of pneumatic actuators is pneumatic artificial muscle (PAM) although these pneumatic actuators play an important role in industrial, medical and other applications. In this study a PAM model based on the assumption Euler’s law is developed, some static force models (geometric model-based static force model, static force model using maximum force of PAM and static force model using a polynomial function) are compared to Sárosi’s force model and two dynamic models based on Sárosi’s static force model and Hill’s muscle model are presented.

Improvement of Wearable Power Assist Wear for Low Back Support using Pneumatic Actuator

This study focuses on developing a safe, lightweight, power assist device that can be worn by people who like caregivers during lifting or static holding tasks to prevent low back pain (LBP). Therefore in consideration of their flexibility, light weight, and large force to weight ratio we have developed a Wearable Power Assist Wear for caregivers, two types of pneumatic actuators are employed in assisting low back movement for their safety and comfort. The device can be worn directly on the body like normal clothing. Because there is no rigid exoskeleton frame structure, it is lightweight and user friendly. In this paper, we proposed the new type of the wearable power assist wear and improved the controller of control system.

Introduction, mathematical modelling and motion control of the novel pneumatic textile actuator

AbstractThis paper introduces a novel type of pneumatic actuator, namely the pneumatic textile actuator (PTA). Although the operating principle is similar to pneumatic artificial muscles, design, fabrication and properties of PTAs show significant differences. PTAs consist of double-layered textiles, fabricated in one piece using the Jacquard weaving technology. By filling the chamber between the two layers with pressurised air, one obtains a low-weight, high-power pneumatic actuator at very low cost. The paper first describes the design, fabrication and properties of PTAs in general. Then, the characteristics of a specific PTA are determined experimentally. Moreover, we derive a mathematical model of the dynamic behaviour of the PTA. The model forms the basis for a motion control algorithm, combining flatness-based feedforward and linear feedback control. Finally, the performance of the controller is evaluated experimentally. The results indicate that PTAs are well suited for motion control tasks requiri...

Positioning Systems Actuated by Corrugated Tube Elements

The purpose of this paper is to validate the actuation of the positioning systems with a new type of pneumatic actuators based on corrugated tubular elements. The latter are also called bellows, usually operating as sealing elements or as pressure transducers.The CAD models of two positioning systems actuated with corrugated tube elements are given. The first one, with one degree of freedom, is driven by two bellows disposed in antagonist way, powered with different pressures, offering different displacements and adjustable stiffness. The second positioning system contains two overlapping platforms that can slide on two axis, (having two degrees of fredom), their operation being performed individualy with two pairs of bellows arranged in antagonist way, on two levels, disposed at 900 from each other. Pneumatic diagrams for the two positioning systems are given. Experimental prototypes are developed and the results of the first tests are presented.

Experimental Validation of Nominal Model Characteristics for Pneumatic Muscle Actuator

Pneumatic artificial muscles belong to a category of nonconventional pneumatic actuators that are distinctive for their high power/weight ratio, simple construction and low price and maintenance costs. As such, pneumatic artificial muscles represent an alternative type of pneumatic actuator that could replace the traditional ones in certain applications. Due to their specific construction, PAM-based systems have nonlinear characteristics which make it more difficult to design a control system with good performance. In the paper, a gray-box model (basically analytical but with certain experimental parts) of the one degree-of-freedom PAM-based actuator is derived. This model interconnects the description of pneumatic and mechanical part of the system through a set of several nonlinear differential equations and its main purpose is the design of intelligent control system in simulation environment. The model is validated in both open-loop and closed-loop mode using the measurements on real plant and the results confirm that model performance is in good agreement with the performance of real actuator.

Design of Wearable Power Assist Wear for Low Back Support Using Pneumatic Actuators

This research focuses on developing a safe, lightweight, power assist device that can be worn by people during lifting or static holding tasks to prevent them from experiencing Low Back Pain (LBP). In consideration of their flexibility, light weight, and large force to weight ratio, two types of pneumatic actuators are employed in assisting low back movement for their safety and comfort. Actuator A is an elongation-type pneumatic rubber artificial muscle that is installed in the outer layer of the garment. Its two ends are fixed on the shoulders and thighs. It can output contractile force, assisting the erector spinae muscles in the same direction. Compared to McKibben-type pneumatic rubber artificial muscle, the elongation type has a larger contraction rate. Actuator B is a layer-type of pneumatic actuator; it is composed of two balloons, and it is installed in the inner layer of the garment. By taking into account the biomechanic structure of the human spine, this device can provide support in two ways. Actuator A acts as an external muscle power generators to reduce the force requirement for the erector spinae muscles. As actuator B acts as a moment arm of the contractile force generated by actuator A, it will increase the effective amount of torque. The device can be worn directly on the body like normal clothing. Because there is no rigid exoskeleton frame structure, it is lightweight and user friendly. The system’s Inertial Measurement Unit (IMU), composed of accelerometer sensors and gyro sensors to measure the human motion signals, can monitor the angles of the human body in real-time mode. By measuring the EMG signal of the human erector spinae muscles, the assistance effectiveness of the proposed device has been proven through experiments.