Description of pneumatic muscle

CHAPTER 2 LITERATURE REVIEW

2.1 Pneumatic Muscle Background

2.1.1 Description of pneumatic muscle

A pneumatic muscle actuator PMA is a mechanical apparatus that copies the conduct of skeletal muscle where it contracts and creates drive in a nonlinear way when activated [1]. PMAs could be found in common elastic tube, wrapped inside man-made mesh, for example Kevlar, at predetermined angle. Defensive elastic covering encompasses the fibber wrapping and fitting metal fittings are connected at every close [2]. The filament wrapping gives uphold and upgrades incitation. PMA is an actuator which changes over pneumatic or water driven vigor into mechanical structure by exchanging the force connected on the internal surface of its bladder into shortening tension. When the PMA is pressurized, the hose expands in its peripheral direction, thus generating a tensile force and a contraction motion of muscle longitudinal direction. The level of contraction and constrain preparation is reliant on the pulling constrain against the PMA load. Figure 2.1 represents the operation of a PMA and Figure 2.2 shows the Festo fluidic muscle. Figure 2.1: Illustration of pneumatic muscle operation [2] Figure 2.2: Commercially used PMA Festo fluidic muscle [11]. This type of actuator has several unique characteristics, some of its characteristics which have made it as an ideal actuator for applications involving human interaction. Pneumatic muscles are capable of producing a high force output. They have higher powerweight and powervolume ratios about 1 Wg and 1Wcm 3 than electric motors or hydraulic actuators [3]. They have a higher force output than a pneumatic cylinder of equal volume [4]. Pneumatic muscles are cost effective, clean, highly dynamic movements, no slip effect; intermediate positions can be set easily by regulating the pressure, compact, and can be used in harsh environments because they do not have moving parts such as pistons or guiding rods [5]. There are also a safe alternative to other actuators. The main disadvantage of this actuator is that its motion is difficult to be controlled due to its nonlinear characteristics. This is due to the need of controlling the both PMA displacement and PMA force by only varying the inlet pressure to the muscle actuator.

2.2 Types of pneumatic muscle