Bio-mimetic actuators: polymeric Pseudo Muscular Actuators and pneumatic Muscle Actuators for biological emulation

Abstract Actuators, the prime drive unit in any system (biological or mechanical), are responsible for transferring energy in its many forms into mechanical motion that permits interaction with the external environment. The complexity of the organic mechanism has traditionally precluded its emulation, but a demand in robotic and other mechatronic systems for closer human interaction involving safety, redundancy, self-repair and affinity, has highlighted the potential benefits of softness, both in terms of functional and physical behaviour. This is prompting a shift in the traditional design paradigm based on motors–gears–bearings–links to a novel bio-mimetic schema based on muscle–tendon–joint–bone. Among the most fundamental features of actuators designed around this format will be a desire to emulate the performance of natural muscle in forming a safe and natural interaction medium, while still possessing the beneficial attributes of conventional engineering actuators, i.e. high power to weight/volume, high force weight/volume and good positional and force control. In this paper a study has been undertaken of two novel forms of actuators (polymeric and pneumatic Muscle), that have characteristics that can be broadly classified as giving them a range of bio-mimetic functions. The work considers the production, modelling and performance testing of these two forms of bio-mimetic actuators. Enhancements to the performance of both systems are explored to show their capacity for bio-emulation. For the pneumatic Muscle Actuator a practical example is briefly explored to show the potential for real world applications of this technology. Finally a comparison of the relative merits of the ‘muscles’ are made with references to required enhancements, improvements or developments needed for viable future exploitation.