Design of Extra Robotic Legs for Augmenting Human Payload Capabilities by Exploiting Singularity and Torque Redistribution

Abstract

We present the design of a new robotic human augmentation system that will assist the operator in carrying a heavy payload, reaching and maintaining difficult postures, and ultimately better performing their job. The Extra Robotic Legs (XRL) system is worn by the operator and consists of two articulated robotic legs that move with the operator to bear a heavy payload. The design was driven by a need to increase the effectiveness of hazardous material emergency response personnel who are encumbered by their personal protective equipment (PPE). The legs will ultimately walk, climb stairs, crouch down, and crawl with the operator while eliminating all external PPE loads on the operator. The forces involved in the most extreme loading cases were analyzed to find an effective strategy for reducing actuator loads. The analysis reveals that the maximum torque is exerted during the transition from the crawling to standing mode of motion. Peak torques are significantly reduced by leveraging redundancy in force application resulting from a closed-loop kinematic chain formed by a particular posture of the XRL. The actuators, power systems, and transmission elements were designed from the results of these analyses. Using differential mechanisms to combine the inputs of multiple actuators into a single degree of freedom, the gear reductions needed to bear the heavy loads could be kept at a minimum, enabling high bandwidth force control due to the near-direct-drive transmission. A prototype was fabricated utilizing the insights gained from these analyses and initial tests indicate the feasibility of the XRL system.

Prototype System for Measuring and Analyzing Movements of the Upper Limb for the Detection of Occupational Hazards

“…The exoskeleton, or mechanical part of the capture system, is in charge of supporting the electronic part and transmitting the arm movements to the different sensors. This aspect differentiates it from most of the exoskeletons in the market, which are made to facilitate movements of people with reduced mobility, or to facilitate actions in which heavy loads are lifted [ 33 , 34 , 35 ]. One such movement capture system is PrioVR, and more specifically the Yost Labs 3-Space Micro USB module ( ), which only integrates accelerometers and gyroscopes as sensors.…”

SUPER-MAN: SUPERnumerary Robotic Bodies for Physical Assistance in HuMAN-Robot Conjoined Actions

“…In [27], an SRLG system named Extra Robotic Legs (XRL) is developed to assist workers who wear Personal Protection Equipment (PPE) while walking and assuming ergonomically complex postures, e.g., kneeling and crouching for near-ground tasks. One of the challenges is how to compromise conflicting requirements of the actuators to have a satisfying load-bearing capacity for supporting workers' and equipment's weight and high bandwidth to better control the dynamic interactions with the ground.…”

Consideration and analysis for attachment position of supernumerary robotic limbs

“…For balance assistance function, Parietti et al [20] presented SRLs consist of two robotic legs, which have 3 DOF each other and worn by a backpacklike harness. Gonzalez et al [8] designed the Extra Robotic Legs(XRL) system that is worn by the operator's back and reduces the payload. For overhead support function, Bonilla et al [2] developed 5 DOF SRLs that is worn on the shoulders.…”