A comprehensive test method for measuring actuation performance of McKibben artificial muscles

Abstract

The versatile nature of artificial muscles and their applications is derived from their ability to actuate in tensile, torsional and bending modes that can mimic the action of hydraulic rams, electric motors and biomimetic curling arms, respectively. Artificial muscles have exhibited great potential for fabricating robotic components and surgical tools due to their resemblance to biological muscles; along with their high actuation force per mass. For further investigation of these artificial muscles as tensile actuators with practical applications, it is imperative to standardise methods for characterising their performance. This article applies an integrated characterization method: simultaneously measuring the free stroke of a McKibben-type hydraulic artificial muscle; the stroke while operating against an externally applied force (isotonic); the blocked force of these muscles while keeping the muscle at constant length (isometric); and the force and displacement change when the muscle operates against a return spring (variable force, pressure). This linear mechanics approach has been verified and allows the prediction of these fundamental actuation characteristics while illustrating the effects of changing external load on the muscle performance. This study proposes an important approach to assist the design of McKibben muscles when used to carry variable loads such as in exoskeletons, prosthetics, and robotics applications.

Design and Passive Training Control of Elbow Rehabilitation Robot

“…The moment of inertia J in the elbow rehabilitation robot model actuated by pneumatic muscle changes with the weight of the patients-changing of the load, which enhances the nonlinearity and uncertainty of the system [25]. Therefore, not only the internal nonlinearity of the system but also the influence of the external load change on the system should be considered.…”

Design Optimization of a Miniaturized Pneumatic Artificial Muscle and Experimental Validation

“…In this work, the force balance principle is employed to derive the preliminary force model [14,28], as proposed by Ferrasi et al [45] and Kothera et al [30]. Considering the free-body diagram of the PAM and the forces exerted on the actuator after providing an internal pressure as shown in Figure 3, the force equilibrium in the x and z directions yields: x-direction:…”

“…The primary goal of creating such a model was to improve the functionality of PAM as passive elements in assistive technologies for human mobility. Salahuddin et al [28] proposed a characterization approach for measuring the changes in force and displacement, as well as the free contraction, blocked force, and contraction, when a hydraulic McKibben muscle was externally loaded. Pillsbury et al [29] studied the effect of bladder thickness and material on the important performance characteristics of a PAM; the results of their modeling and experiments showed that the blocked force and free contraction both decreased when the thickness of the bladder was increased.…”

Bending Properties of an Extensile Fluidic Artificial Muscle

“…The muscle is a form of soft actuation as its stiffness is magnitudes lower when compared to traditional pneumatic cylinders or linear electric motors ( Majidi (2014) ). Modeling and testing of their axial behavior has been covered by a number of research groups ( Chou and Hannaford (1996) ; Tondu and Lopez (2000) ; Takosoglu et al (2016) ; Salahuddin et al (2021) ; Chambers and Wereley (2021) ). Achieving variable stiffness of the actuators was investigated in Xiang et al (2016) .…”