Pneumatic artificial muscles (PAMs) have been researched for applications in powered exoskeletons, orthosis and robotics. Their high force to mass ratio, low cost and inherent compliance are particularly advantageous for systems requiring physical interaction with humans.Sleeve PAMs, which introduce an internal structure to the actuator, offer improved force capacity, contraction ratio, efficiency and operating bandwidth. In this paper sleeve PAMs are applied to a popular muscle configuration; that of a joint operated antagonistically by two muscles. It is shown that the sleeve PAM can increases the range of joint rotation by 14% or load capacity by over 50% of that of a comparable joint actuated with traditional PAMs, depending on the joint configuration. The stiffness of joints actuated with both PAM types is also studied, particularly the case of closed system operation (mass of air in the PAMs is constant), where the reduced volume of the sleeve PAM significantly increases the observed stiffness. Finally energy consumption is considered, showing substantial savings in the case of joints actuated with sleeve PAMs.

Force-based manipulation control strategies are evolving as a primary mechanism in robotics for performing the fine manipulation tasks typical within manufacturing assembly. The ability to systematically compare robotic system performance and quantify true advancement in fine manipulation is of utmost importance. Accordingly, the objectives of this paper are threefold: 1) creation of a peg-in-hole test method with associated performance metrics and a systematic data analysis strategy for performance benchmarking, 2) first demonstration of a recently developed manipulation controller piloting a robotic hand and its paired task-level logic for completing the peg-in-hole test, and 3) exemplifying the performance benchmarking technique by comparing two approaches for robotic insertions-the previously mentioned compliant hand, stiff arm system, and a stiff gripper, compliant arm system. Analyses reveal that the unconventional hand system can perform at and sometimes above the level of the gripper system in the developed peg-in-hole scenario. Moreover, the hand's active control of the peg's full Cartesian pose reduces positional error sensitivity and minimizes exerted insertion forces, highlighting the strategy's potential for fine manipulation tasks. Results indicate that robotic arms equipped with highly articulated and sensorized robotic hands can provide a truly realizable solution path for performing peg-in-hole tasks.