New Specification for Minimum Performance Criteria for Muscle Activation During Overhead Activities While Wearing Exoskeletons Intended to Support the Shoulder Joint
1. Scope
Minimum performance criteria is determined based on a downselection of possible performance metrics (e.g., muscle activation, torque, metabolic cost, range of motion, etc.) – evaluated using a set of representative tasks – to those considered appropriate for a given combination of exoskeleton and task type. For example, metabolic cost is not typically evaluated for an exoskeleton intended to support the lower back during a lifting task, so it is not considered minimum performance criteria for that combination of exoskeleton and task type. However, torque is an appropriate performance metric for that scenario, so it is considered minimum performance criteria for that scenario. Individual standards are or will be developed for each scenario as deemed relevant by the F48 committee.
This standard specification only considers minimum performance criteria for user-centric performance metrics (e.g., physiological measures); mechanical performance metrics (e.g., material or actuator properties) or computational performance metrics (e.g., controller processing speed) are covered in other standards. This specification standard defines one or more user-centric minimum performance criteria for an exoskeleton that is intended to support a joint (or joints) on the body while a given type of task is being performed.
While the specific tasks performed while wearing in exoskeleton in a given application will vary (e.g., lifting boxes for an industrial logistics application vs. lifting ammunition rounds for a military logistics application), there are common classes of tasks that are largely representative of the physical challenges present during these applications. This standard includes test methods to evaluate the defined minimum performance criteria by conducting evaluations on a series of users wearing the exoskeleton. This standard specifies the required representative tasks to be performed, test procedures, population selection, performance metrics, and analysis methods.
This specification standard defines minimum performance criteria for muscle activation related to the shoulder joint when an exoskeleton intended to support the shoulder joint is worn while performing overhead activities (e.g., lifting a box above the shoulders, manipulating a tool overhead). Both active and passive exoskeletons are in scope.
The class of tasks in scope for this standard specification are those that involve use of the exoskeleton wearer’s arm(s) and hand(s) to handle an object required to perform a task overhead (e.g., drilling) wherein the wearer’s arm(s) and hand(s) are continuously engaged for a period of time before they are disengaged (e.g., drilling overhead for two minutes then lowering the drill such that the task is no longer being performed overhead for a period of time, then repeating).
An exoskeleton may impact other parts of the user’s body beyond the joint(s) specified in this standard. However, this standard only considers the impacts to the user according to the specified criteria as applied to the specified joint(s). Therefore, the specified minimum performance criteria is limited to the joint(s) the exoskeleton is intended to support.
ASTM F48 standards assist industry in developing and evaluating their exoskeleton systems (i.e., standard test methods, practices, and guides). There remains a gap in defining a set of criteria with minimum performance thresholds (i.e., standard specifications and classifications). We envision this as three types of products: (1) establishing a set of minimum performance criteria, (2) developing testing specifications to evaluate for that criteria, and (3) determining minimum performance thresholds to be achieved.
