Artificial Muscles: Actuators for Biorobotic Systems

Abstract

Biorobotic research seeks to develop new robotic technologies modeled after the performance of human and animal neuromuscular systems. The development of one component of a biorobotic system, an artificial muscle and tendon, is reported here. The device is based on known static and dynamic properties of biological muscle and tendon that were extracted from the literature and used to mathematically describe their force, length, and velocity relationships. A flexible pneumatic actuator is proposed as the contractile element of the artificial muscle and experimental results are presented that show the force-length properties of the actuator are muscle-like, but the force-velocity properties are not. The addition of a hydraulic damper is put forward to improve the actuator's velocity-dependent properties. Further, an artificial tendon is set forth whose function is to serve as connective tissue between the artificial muscle and a skeletal structure. A complete model of the artificial muscle-tendon system is then presented which predicts the expected force-lengthvelocity performance of the artificial system. Experimental results of the constructed device indicate muscle-like performance in general: higher activation pressures yielded higher output forces, faster concentric contractions resulted in lower force outputs, faster eccentric contractions produced higher force outputs, and output forces were higher at longer muscle lengths than shorter lengths.

Advances in Propulsive Bionic Feet and Their Actuation Principles

“…By controlling both actuators, the compliance and equilibrium position can be set [40]. At the University of Washington (United States) Klute et al [41,46,47] have designed an artificial muscletendon actuator to power a below-knee prosthesis. To meet the performance requirements of an artificial triceps surae and Achilles tendon, an artificial muscle, consisting of two flexible pneumatic actuators in parallel with a hydraulic damper, and placed in series with a bilinear, two-spring implementation of an artificial tendon, was built into the ankle-foot prosthesis.…”

Biologically Inspired Robots

“…Later robots have used pneumatics (Nelson & Delcomyn, 2000, Quinn et al, 2001) to drive the legs or artificial muscles such as McKibbon actuators. (Klute et al, 2002), electroactive polymers (Bar-Cohen, 2003), Nitinol wire with shape memory (Safak & Adams, 2002), and other devices. The common feature of these artificial muscle devices is that they incorporate essential features of living muscle such as compliance and favorable force-velocity relationships while at the same time not consuming too much power.…”

“…Furthermore, when pulsed, power can be controlled in ways quite similar to the ways in which muscle is controlled by the nervous system (Cocatre-Zilgien et Delcomyn & Nelson, 2000). In some cases, pneumatic control is used in flexible devices known as a McKibben actuators (Klute et al, 2002;Quinn et al, 2001). A significant problem with pneumatics, however, is that a robot so powered must either generate its own compressed air or be tethered via tubes to a supply, thus eliminating the possibility that the robot can be autonomous.…”

Propulsion System With Pneumatic Artificial Muscles for Powering Ankle-Foot Orthosis

“…Several forms of this type of muscle have actually been commercialized by different companies such as Bridgestone Co. [5], the Shadow Robot Company [6], Merlin Systems Coorporation [7] and Festo [8]. The interest in these actuators is growing increasingly and several groups all over the world use McKibben muscles in various robotic and medical applications [9][10][11][12].…”