UMArm: Untethered, Modular, Wearable, Soft Pneumatic Arm

Abstract: Robotic arms are essential to modern industries, however, their adaptability to unstructured environments remains limited. Soft robotic arms, particularly those actuated pneumatically, offer greater adaptability in unstructured environments and enhanced safety for human-robot interaction. However, current pneumatic soft arms are constrained by limited degrees of freedom, precision, payload capacity, and reliance on bulky external pressure regulators. In this work, a novel pneumatically driven rigid-soft hybrid arm, ``UMArm'', is presented. The shortcomings of pneumatically actuated soft arms are addressed by densely integrating high-force-to-weight-ratio, self-regulated McKibben actuators onto a lightweight rigid spine structure. The modified McKibben actuators incorporate valves and controllers directly inside, eliminating the need for individual pressure lines and external regulators, significantly reducing system weight and complexity. Full untethered operation, high payload capacity, precision, and directionally tunable compliance are achieved by the UMArm. Portability is demonstrated through a wearable assistive arm experiment, and versatility is showcased by reconfiguring the system into an inchworm robot. The results of this work show that the high-degree-of-freedom, external-regulator-free pneumatically driven arm systems like the UMArm possess great potential for real-world unstructured environments.

• The paper introduces UMArm, an untethered, modular, wearable soft pneumatic arm that integrates valve-embedded McKibben actuators and a lightweight rigid spine for untethered operation in complex environments.
• UMArm demonstrates high precision (2.6 mm RMSE) and payload capacity (3 kg) through its dense actuator arrangement and integrated architecture, enabling approximately 12 minutes of untethered operation.
• The UMArm's versatility is shown in applications like a wearable assistive arm and an inchworm robot, highlighting its potential for adaptable use in unstructured and human-interactive robotics.

Untethered, Modular, Wearable, Soft Pneumatic Arm

The paper "UMArm: Untethered, Modular, Wearable, Soft Pneumatic Arm" elaborates on the introduction and evaluation of an innovative pneumatically driven hybrid robotic arm designed to address challenges faced by traditional robotic arms in unstructured environments. By integrating valve-embedded McKibben actuators into a lightweight rigid structure, the UMArm offers an untethered, highly adaptable solution with precise control capabilities.

Design and Innovation

The UMArm combines multiple technological advancements to overcome limitations in existing pneumatic soft arms. It utilizes valve-embedded McKibben actuators (VEMAs), which integrate self-regulating pressure mechanisms directly within each actuator. This removes the need for external pressure regulators and complex tubing systems, significantly enhancing portability and reducing system complexity.

• Integrated Pneumatic-Power-Communication Bus Architecture: This design supports numerous actuators operating in parallel, sharing tubing and wiring, thereby enabling a high number of independently controlled degrees of freedom (DoF).
• Dense Actuator Arrangement: Each arm segment accommodates eight VEMAs, allowing multidirectional antagonistic stiffening at each joint to enhance precision and payload capacity.
• Lightweight Rigid Spine Structure: Constructed to efficiently transmit forces, this spine supports a large range of motion while maintaining high strength-to-weight ratios.

Performance and Capabilities

UMArm demonstrates remarkable capabilities for use in real-world environments. The arm achieves full untethered operation courtesy of its simplified pneumatic inputs and streamlined architecture. Tests reveal the following performance metrics:

• Precision: Achieves a steady-state RMSE of 2.6 mm during waypoint tracking experiments, showcasing its reliability in complex tasks.
• Payload Capacity: Capable of lifting weights up to 3 kg, attesting to its strength despite its lightweight construction (1.15 kg).
• Untethered Operation: Equipped with a portable compressed air tank, UMArm can sustain operations for approximately 12 minutes at full capacity.

Applications and Demonstrations

UMArm's versatility was demonstrated through several experiments, showcasing its ability to perform tasks traditionally challenging for pneumatically driven arms:

• Wearable Assistive Arm: When worn on a rig by a human operator, UMArm assisted with carpentry tasks, demonstrating its potential as a portable assistive device.
• Directional Compliance Control: Exhibited the capability to maintain stiffness in one direction while allowing flexibility in another, thus adapting to varying environmental interactions.
• Transformation into Inchworm Robot: By reconfiguring its structure, UMArm transitioned into an untethered inchworm robot, effectively broadening its application scope to include autonomous locomotion and interaction scenarios.

Implications and Future Research

The UMArm presents a pivotal shift in the design of robotic arms, particularly in unstructured and dynamic environments. Its ability to operate untethered and safely interact with humans opens new avenues in industrial, assistive, and wearable robotics. Future research could focus on exploiting UMArm's hardware capabilities with advanced control strategies to achieve even higher levels of precision and efficiency. Enhancements such as increased segment numbers or improved actuator models could further boost its dexterity and operational range.

In conclusion, UMArm exemplifies the integration of dense actuator networks within lightweight, untethered systems, highlighting the trajectory for innovation in soft robotic arms for varied real-world applications.