Double-Acting Sleeve Muscle: Concept and Example Application in Powered Prostheses

Pneumatic muscle is a new type of actuator that has a number of advantages over pneumatic cylinders, such as higher power-to-weight ratio, smooth speed adjustment, and longer operating life. Pneumatic muscle-based industrial devices can be used in combustible, explosive, and contaminated environments in different industry fields. This article is dedicated to the modeling of pneumatic muscles manufactured by FESTO, a global leader in the production of this type of pneumatic actuators. The existing pneumatic muscle models have several significant drawbacks: they can only be applied to specific types of pneumatic muscles and are inappropriate for FESTO pneumatic muscles, their accuracy is low, and they contain too many adjusting factors. The model presented in this article makes it possible to obtain static characteristics with up to 10% accuracy. The aim of this study is to assess the feasibility of application of the developed expression for modeling the dynamic characteristics of pneumatic muscle and to develop a comprehensive mathematical model of pneumatic muscle for describing the processes of raising and lowering a load.

Pneumatic muscle actuator (PMA) is a type of linear pneumatic actuator that is soft and flexible, capable of moving like human muscles. These characteristics allow the muscle actuators to adapt to different robotic systems and medical applications. This paper presents the design, construction, characterization, and experimental validation of PMA. In addition to describing the pneumatic muscle contraction, the significant hysteresis nonlinearities of PMAs have hampered high-precision motion control. This paper presents new forma for modeling the length of the contraction PMA. Because contraction length parameters have a sigmoidal structure, the sigmoid function is a suitable form to model. Applied the fitting curve method. We use the MATLAB function lsqcurvefit to fit the equation to the data. The mathematical model was validated with Mean Squared Error (MSE) between the experimental results and the mathematical model. additionally, computed the correlation coefficient to assess the relationship between the model predictions and the experimental data.

This paper describes the mechanism of a one-legged jumping robot that can mimic the muscular and skeletal system of a human leg. The jumping robot has a waist, a thigh, a shin, a foot, and a toe. The McKibben-type pneumatic muscle actuators that are able to generate the maximum output force of 1200 [N] are employed. Two kinds of pneumatic artificial muscles, mono-articular and bi-articular muscles, were installed in the rear and in the front of the thigh and shin. A jumping pattern is also developed in consideration of the performance of the pneumatic actuators. Several jumping experiments were conducted, and the effectiveness of the mechanism and jumping pattern was verified.

In this study, a simulation model for a powered hip orthosis (PHO) with air muscles to predict the gait of paraplegics is presented which can be used as a design tool for hip orthoses. Before simulation, mathematical models for a human dummy with an orthosis and a pneumatic muscle actuator were generated. For the air muscle, coefficients required were obtained by static and dynamic experiments of the air muscle and experiments for the valve controlling the air pressure. The computation was conducted on the ADAMS package together with MATLAB. Computer simulation of the flexion of hip joints by the pneumatic muscle results in similar values to those from gait analysis. With the development of a simulation model for a PHO, the gait simulation model using pneumatic muscles can be used to analyze and evaluate the characteristics and efficiency of a PHO by setting the input and boundary conditions.

This paper experimentally investigates the performance of piezoelectric force actuators. Using the same encapsulated piezoelectric stack, an inertial-type actuator and a frame-type actuator are constructed for performance comparison. The experimental results are also used to validate the recently established actuator models, whilst the mechanical and piezoelectrical parameters of the models are experimentally identified. The performance of the actuators is described by the transmitted force(s) and input power flow from the actuators to the base structure with reference to the same electrical input voltage to the stack. The validation is deemed successful due to the strong agreement observed between the measured and predicted actuator performances. Additionally, it is discovered that the frame-type actuator has the capacity to produce significantly higher transmitted forces and input power flow to the base structure compared to the inertial-type actuator. The mechanism underlying the performance disparity between these two types of actuators is also examined. This paper clarifies the mechanism, shedding light on the design and optimization of piezoelectric actuators.

Robot-assisted therapy has shown potential in neuromotor rehabilitation. A therapeutic robot driven by pneumatic muscle actuators has been developed in our research group. However, the design of fine and real-time feedback robot control is a challenge. One of the difficulties is the lack of a general dynamic model of the pneumatic muscle actuator. In this study, a phenomenological model has been developed to quantify the dynamic behavior of pneumatic muscle actuator by fitting the experimental length response of the pneumatic muscle, to a step pressure input. In addition, comparison of the dynamic responses of two pneumatic muscles of different dimensions has also been studied. Several control strategies for the pneumatic muscle actuator are discussed based on the results from this study.

A bimorph pneumatic bending actuator by control of fiber braiding angle

The exoskeleton plays an essential role in the field of physical rehabilitation. Several actuators are used for the exoskeleton application, but the pneumatic muscle actuator has proved to be the best due to its high power to weight ratio, compliance, and safe operation. The objective of this paper involves the fabrication and experimental characterization of a pneumatic muscle actuator to actuate an exoskeleton for the elbow joint. This paper presents the development and testing of twelve pneumatic muscles of varying materials and sizes, to find the best combination to suit the intended application. The characterization process involved several tests, which related force, deflection, and pressure at various loading conditions. A modular test rig was developed to conduct all the tests with minor adjustments to the test setup. The study also involved designing and developing an elbow exoskeleton to test the pneumatic muscle in the real-world scenario. The exoskeleton is designed with a novel hinge to compensate for the antagonistic nature of the pneumatic muscle actuator. The tests showed the muscles with higher tensile modules bladders having a lower hysteresis and better load handling capability, but these suffered from lower contraction and force characteristics. The styrene-based muscle with a 12mm bladder (S12LB) showed the best force and deflection characteristics at various pressures and loading conditions. The styrene bladder has a modulus closer to the skeletal muscle, therefore demonstrating higher compliance and making it a preferred choice for the exoskeleton application

It seems that the pneumatic artificial muscles (PAMs) have a very great potential in industrial applications for the actuation of new types of robots and manipulators. Their properties such as compactness, high strength, high power-to-weight ratio, inherent safety and simplicity are worthy features in advanced robotics. In this paper we describe the design, construction and experimental testing of a single-joint manipulator arm actuated by pneumatic muscle actuators. An antagonistic muscle pair is used in a linear translational sense to produce a force or in a rotational sense to produce a required torque on the pulley. The concept, operating principle and elementary properties of pneumatic muscle actuators are explained. A nonlinear mathematical model of the manipulator arm driven by pneumatic artificial muscles and controlled with proportional control valve is derived, which is used in a numerical simulation program. The experiments were carried out on practically realized manipulator actuated by pair of muscle actuators set into antagonism configuration.

In this article, a model-based tracking control of a pneumatic muscle actuator using only one 5/3 proportional directional valve is investigated. Pneumatic muscles are difficult to control due to their highly nonlinear system dynamics and hysteresis effects, but they offer advantages such as high power/weight ratio, low costs, easy maintenance and flexibility. The actuator consists of two muscles moving a mass horizontally fixed on a linear guide rail. The challenge is to control those two muscles with only one 5/3 proportional directional control valve. Based on the idea of a cascaded control structure a nonlinear model-based control algorithm is computed. The inner loop control is implemented as a force controller added by a force disturbance observer to estimate unmodeled muscles forces. A position control in the outer loop is added and implemented as a linear tracking controller. The implemented control structure shows good follow-up error and stationary precision in measurements. The shown control approach contributes to an improved path control performance of pneumatic muscle actuators.

Pneumatic servo positioning systems have been in use for long time and subject to wide spectrum of studies due to their numerous advantages: inexpensive, clean, safe and high ratio of power to weight. However, the compressibility of air and the inherent non-linearity of these systems continue to make achieving accurate position control a real challenge. Conventional pneumatic servo systems are based on cylinder actuators that are difficult to control precisely due to the aforementioned nonlinearities as well as the nonlinear behavior of the air flow through the valve, the friction between the cylinder and the piston, and the stick slip effect at the low velocity of the system. In this paper, a position servo control system using a pneumatic muscle actuator is studied. Pneumatic muscle actuator is a novel type of actuator which has even higher force to weight ratio than the cylinder. In addition, muscle actuator introduces a stick slip free operation giving an interesting option for positioning systems. However, significant hysteresis and position dependant force result in a highly nonlinear system, a real challenge for good control performance. In this paper, pneumatic muscle actuator is controlled by a low-cost on/off valve with PWM-strategy instead of costly servo or proportional valve. The main processes of the system, including flow dynamics, pressure dynamics, force dynamics and load dynamics are derived to provide a full nonlinear model that captures all the major nonlinearities of the system. This model is used for analyzing and tuning the controller performances by simulations before implementing in the real system. In addition, a recently introduced method of using bipolynomial functions to model the valve flow rate is utilized to provide a continuous and invertible description of flow for controller designs. A proportional plus velocity plus acceleration controller with feed-forward component (PVA+FF) is designed based on the linearized system model. For a comparison, a sliding mode controller (SMC) based on linear as well as non-linear system model are designed. The performance of the designed controllers is studied by simulations. The stability and performance analysis includes the effects of friction modeling error and valve modeling error. The robustness of the controllers is tested by varying the payload mass of the system.

Pneumatic Artificial Muscles, which are lightweight actuators with inherently compliant behavior, are broadly recognized as safe actuators for devices that assist or interact with humans. This paper presents the design and implementation of a soft pneumatic muscle based on the eversion principle - Eversive Pneumatic Artificial Muscle (EPAM). The proposed pneumatic muscle exerts a pulling force when elongating based on the eversion (growing) principle. It is capable of extending its length by a minimum of 100% when fully inflated. In contrast to other soft pneumatic actuators, such as the McKibben's muscle, which contract when pressurized, our EPAM extends when pressure is increased. Additionally, important advantages of employing the eversion principle are the capability to achieve high pulling forces and an efficient force to pressure ratio. In a pivoting joint/link mechanism configuration the proposed muscle provides motion comparable to human arm flexion and extension. In this work, we present the design of the proposed EPAM, study its behavior, and evaluate its displacement capability and generated forces in an agonistic and antagonistic joint/link arrangement. The developed EPAM prototype with a diameter of 25 mm and a length of 250 mm shows promising results, capable of exerting 10 N force when pressurized up to 62 KPa.

In this paper, we propose a new type of soft actuator (pneumatic silicon outer fence mold actuator) whose sponge is covered with silicon rubber. Since the stiffness of the actuator is controlled by pressure in the sponge chamber, it is possible to realize a soft mechanism by using pressure compressibility. From some experimental results, the basic characteristics of the actuator are cleared.

A study is conducted on several paradigms to provide closed-loop position control of an actuator powered by a pneumatic muscle system. This actuator has many advantages including having extremely high power/weight and power/volume ratios, being light-weight, autonomous, and safe. An implementation as a tracking controller using a gain scheduling method is presented.

The current equipment for generating of the rotational motion by antagonistic pneumatic muscle actuator is standardly solved with a circular pulley, on which a flexible strip is strung and its ends are connected with artificial muscles. However, in this solution, torque and stiffness of such actuator decrease with increasing rotation of the actuator arm. This is due to the nonlinear decrease of muscles forces according to their contraction. By application of the oval cam, a smaller decrease in torque and thus the greater and symmetrical stiffness of the actuator with pneumatic artificial muscles can be obtained.