A Compliant and Precise Pneumatic Rotary Drive Using Pneumatic Artificial Muscles in a Swash Plate Design

Compliant and precise rotary drive units are essential for the design of articulated robots that are capable of safe human-robot collaboration. In this paper, we present a new pneumatic rotary drive unit that combines the compliance of pneumatic systems with the ability to perform high precision positioning. We use pneumatic artificial muscles (PAMs) pulling on a swash plate to avoid the stick-slip phenomenon and to realize adjustable stiffness. Furthermore, the presented drive unit can operate in 360° continuous rotation. These properties make the drive particularly suitable for the later use in human-robot collaboration. We explain the mechanic design as well as the pneumatic and electric control system that we use to operate the drive unit. We derive the equations to calculate the static torque distribution and compare the theoretical results to the data measured on the realized laboratory test stand, depicted in figure 1. The accuracy of the used 16-bit encoder is achieved and adjustable stiffness is realized and measured on the laboratory test stand. The measurements of the reaction to a step response are discussed based on a first and basic control strategy.