A Systematic Design Strategy for Antagonistic Joints Actuated by Artificial Muscles

Characterization, modeling, and control of pneumatic artificial muscles is typically demonstrated in an antagonistic architecture. There are many conflicting design constraints when designing these systems, resulting in many different styles of testing apparatus. A novel, systematic design methodology is proposed to improve these architectural constraints and describe the envelope of possible system outputs in terms of displacement and torque/force. It is founded upon a mathematical expression of actuator-model convolution. The proposed systematic antagonistic design by convolution (SADC) method involves three steps. First, model the workspace capability of each fluidic muscle. Second, devise the physical layout of the antagonistic apparatus by convolution, which investigates the structure for output workspace dexterity. Finally, establish trajectories and control, which is left to the application engineer. This method reduces the focus on the actuator capability, and instead represents a general method to approach system-level specification and design. The new SADC methodology facilitates design for a larger symmetric force capability. It is demonstrated for two cases, a symmetric and an asymmetric antagonistic system. It contributes a new pathway to explore optimization of antagonistic workspace symmetry at a system level and aids the engineer in visualizing architectural tradeoffs. It is independent of the application's control methodology and can be modified to examine alternative cost functions that require optimization.