Design of hands for aerial manipulation: Actuator number and routing for grasping and perching

Abstract

This paper examines aspects of robot hand performance specific to grasping and perching from an aerial vehicle and shows how various hand design parameters affect performance. Specifically, we consider hand performance when subject to external forces imparted to the hand from carrying a payload or from perching on a fixed item and explore the impact of design and grasp parameters including tendon routing/pulley ratio, object size, and palm size on the performance of both fully and underactuated designs. Our results show that underactuated designs utilizing a single actuator per finger are sufficient in all cases we studied, but that fully actuated designs can perform better for perching applications. Additionally, we find that increasing the palm width improves performance both when perching and grasping, and that a small distal/proximal pulley ratio is beneficial for payload carriage but counterproductive for perching. I. INTRODUCTION As aerial vehicles begin to take on increasingly greater roles in both civilian and military applications, physically interacting with the world through aerial manipulation is becoming possible. However, the challenges associated with grasping and manipulation from aerial vehicles are many: necessity for lightweight structures, prompting simplistic and efficient designs; low impedance and instability of the vehicle during flight, requiring and allowing relatively small contact force magnitudes and in only a few directions; and limited ability to orient an end-effector with respect to the vehicle, among others. The design of the hand for an aerial manipulator must take into account these challenges and limitations in order to allow for good performance. In this paper we discuss how the choice of the number of actuators, the routing of those to the links of a hand, and other factors such as palm width affect the ability of the hand to perform both payload carriage and perching tasks. While aerial manipulation platforms are becoming more prevalent, there have been few concerted efforts to investigate designs of grippers for these systems. Instead, most vehicles are equipped with simple manipulators or repurposed hands based on existing designs (1-9). Many of these systems have utilized underactuated hand designs because the benefits of underactuation, including adaptability, robustness, and lower hand complexity and mass. Although beneficial during all kinds of manipulation