Actuators are a vital component, and more often than not one of the limiting factors in robotics and robotics related applications. For the use of actuators in robotics related to humanoids, exoskeletons, exo-suits, prosthetics and orthosis, there are more factors that influence the selected actuator than the basic mechanical outputs, size, backlash, material and power consumption. The main interest within these applications is that because the device is being carried by the human user, thus weight, power consumption and form factor are important selection parameters. Selecting the smallest actuator that suits the specifications has significant follow on effects for full system design. Such decision optimisation leads to less energy to operate, lighter actuator and human loading, and a reduced form factor.This correct selection of an actuator for these applications is a difficult and lengthy process to perform. They come in multiple forms that include electric, pneumatic, hydraulic and combustion. In addition, there are some more specialised actuators like pneumatic gel muscles (PGM) and similar where a flexible tube is pressurised by pneumatics or hydraulics, which causes the tube to swell and contract like human muscles. The interest behind looking into as wide of a range as possible of actuators is that each type of actuator behaves differently and has different situations where it is the most effective. Selecting an actuator that is able to perform the function is relatively simple, if one exists, however selecting the most suitable actuator is not as it depends on designer knowledge and available search time. This is due to the plethora of available actuators across suppliers with different types of actuators being better at different application cases making selecting the ideal actuator a complicated and time-consuming task.This paper creates an organisational framework and database for searching the wide range of actuators. This dataset is organised into a design tool that plots the properties of each actuator on varying graphs creates various Ashby charts to rapidly narrow the selection space for designers. Available actuators are compared and grouped based on a variety of parameters linking pairs of key related corresponding parameters (for example torque and size) and conflicting parameters (for example torque and speed).A case study is performed that looks at the relationship of where current actuators that are used for humanoids, exoskeletons, exo-suits, prosthetics and orthosis lie on these charts. Following this case study, a trial situation where a specific application is chosen and the database is utilised to pick the ideal actuator is compared to the actuator that is selected by multiple experts in the field. The time taken to select the actuator and a comparison between the selected actuators properties and the initial specifications are used to determine the effectiveness of the database. In addition, a meta-analysis identifies clusters of current actuators, gaps for new developments, and trends.This work provides research direction into developing specific actuators to fit into these gaps which will allow for the advancement of all fields of robotics, with significant benefits to humanoids, exoskeletons, exo-suits, prosthetics and orthosis. Further, the database of Ashby charts alone is a useful tool for the selection process of an actuator in any application.

Development of an Organisational Framework for the Optimal and Efficient Selection of Actuators

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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