Design, Topology Optimization, and Additive Manufacturing of a Pneumatically Actuated Lightweight Robot

Abstract

Soft robotics research has rapidly incorporated Additive Manufacturing (AM) into its standard prototyping repertoire. While numerous publications have highlighted the suitability of AM for producing soft pneumatic actuators, fluidic components, and lightweight structures, their integration into an industry-like robotic arm has not yet been shown. Against this background, a pneumatically actuated robot was developed that incorporates additively manufactured soft structures into rigid articulated hinges that generally allow for integration into today’s industrial production lines. The development of the robot, including pneumatic soft rotary bellows and rotary vane actuators (RVAs), is summarized, and its functionality is proven. It was found that using AM can increase the structural stiffness of robot links to a significant degree as manufacturing-related constraints in topology optimization are largely eliminated. Moreover, it was found that multi-material polyjet printing of soft rotary bellows actuators allows for highly integrated designs that provide low leakage and friction. However, these soft rotary actuators are still inferior in terms of endurance and performance if compared to AM replicas of RVAs. Our work narrows the gap between soft robotics research and today’s industrial applications, may realign research directions, and may provide impulses for the industry towards soft robotics and AM.

Bisection Constraint Method for Multiple-Loading Conditions in Structural Topology Optimization

“…From Section 4, it is found that the proposed method yields good results by minimizing the maximum compliance when solving TO problems under multiple-loading conditions compared to the TEWS method. On the other hand, past research has considered that the proper optimization solution can be obtained for multiple objectives with different degrees of importance by changing the weight factors (WS methods, [29,[34][35][36][37][38][39][40][41][42]). In this section, the features of the proposed method and its advantages are discussed by comparing the TO results between this method and the WS methods (including the TEWS method in Stage 1 of the proposed framework).…”

“…Thus, it is easier to obtain one or more optimal solutions by solving the transformed problem(s) [35]. Among these methods, the weighted sum (WS) method [29,[34][35][36][37][38][39][40][41][42] for multi-objective optimization is widely utilized, which involves assigning weights to each objective and determining a compromised solution. This method not only allows for the generation of multiple solution points by adjusting the weights accordingly but also enables obtaining a single solution point reflecting preferences linked to a specific set of weights.…”

“…WS methods have also been widely used in recent studies, particularly in applied articles. For instance, Sun et al [41] and Dämmer et al [42], in 2023, used WS methods to develop 3D real robot structures. Guo et al [43], in 2023, utilized WS methods in their studies to develop explicit TO for 3D geometrically nonlinear structures.…”

Multimethodology based on Design-to-Value (DtV), integrated with simulation techniques and prioritization of teamwork for the optimization of a pneumatic rack & pinion actuator

“…In a second extremely important step, FEA are used to perform an optimization of the shape and dimensions of each component, a set of characteristics often defined as "topology" [8]. It is possible to model the component geometry, reinforcing the areas where a high strength is needed and lightening other ones where reinforcing material is not necessary [9,10]. Two examples are reported below, for describing more clearly how this approach was used.…”

Design and Additive Manufacturing of a Continuous Servo Pneumatic Actuator

“…A quest for particularly lightweight, compact, and affordable systems with compliant and back-drivable behavior [ 1 ] has given rise to a variety of actuation concepts. Pneumatic actuators have attracted interest because of their simple design, low weight, and low cost, and functional prototypes of pneumatically actuated robots with articulated joints have already been described [ 2 , 3 , 4 ]. In soft robotics where different compliant actuation methods, such as electrohydrodynamic devices [ 5 ], are researched, the easily manufacturable pneumatic actuators are still the most common [ 6 , 7 , 8 ].…”