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In this paper, optimal swing up of a double inverted pendulum (DIP) with two underactuated degrees of freedom (DOFs) is solved using the indirect solution of optimal control problem. Unlike the direct method that leads to an approximate solution, the proposed indirect method results in an exact solution of the optimal control problem, but suffers from its limited convergence domain which makes it difficult to solve. In order to overcome this problem, an inversion-based method is used to obtain the required initial solution for the indirect method. In the proposed methodology, dynamic equations are derived for a general inverted pendulum using Euler-Lagrange formulation. Then the necessary optimality conditions are derived for a DIP on the cart using the Pontryagin’s maximum principle (PMP). The obtained equations establish a two-point boundary value problem (TPBVP) which solution results in optimal trajectories of the cart and pendulums. In order to demonstrate the applicability of the presented method, a simulation study is performed for a DIP. The simulation results confirm the superiority of the proposed method in terms of reduced effort.

Abstract Soft materials that convert light into mechanical energy can create new untethered strategies for actuating soft robotics. Yet, the available light‐driven materials are often incompatible with standard fabrication in soft robotics and restricted to shapes (e.g., sheets) that have limited capability for 3D deformation; often laser or focused light is required for actuation. Here, to address these challenges, a straightforward method for synthesizing sunlight‐responsive fluidic actuators from off‐the‐shelf silicone precursors capable of expanding in 3D is developed. A liquid phase and activated carbon as photothermal elements are constrained in the elastomer. Solar spectral light triggers a liquid–gas phase transition creating sufficient pressure to overcome the internal elastic stress and actuate the material. The fluidic actuation is characterized under varying light conditions reaching expansion cycle times between ≈20–500 s, strains of 28%, and actuation stress of ≈1.3 MPa in different experiments. The materials were then used to exemplarily drive a mechanical switch, a liquid dispensing soft pump, a valve, and a bending actuator. As the described materials are easy to produce in a 5 min synthesis by standard molding techniques, it is believed that they are a promising opportunity for embodied energy converters in environmentally powered soft robots that respond to sunlight.

Abstract The emergence of the field of soft robotics has led to an interest in suction cups as auxiliary structures on soft continuum arms to support the execution of manipulation tasks. This application poses demanding requirements on suction cups with respect to sensorization, adhesion under non‐ideal contact conditions, and integration into fully soft systems. The octopus can serve as an important source of inspiration for addressing these challenges. This review aims to accelerate research in octopus‐inspired suction cups by providing a detailed analysis of the octopus sucker, determining meaningful performance metrics for suction cups on the basis of this analysis, and evaluating the state‐of‐the‐art in suction cups according to these performance metrics. In total, 47 records describing suction cups are found, classified according to the deployed actuation method, and evaluated on performance metrics reflecting the level of sensorization, adhesion, and integration. Despite significant advances in recent years, the octopus sucker outperforms all suction cups on all performance metrics. The realization of high resolution tactile sensing in suction cups and the integration of such sensorized suction cups in soft continuum structures are identified as two major hurdles toward the realization of octopus‐inspired manipulation strategies in soft continuum robot arms.

Soft pneumatic network (Pneu-net) actuators are frequently used to achieve sophisticated movements, but they face challenges in producing both bending and twisting motions concurrently. In this paper, we present a new Pneu-net twisting and bending actuator (PTBA) design that enables them to perform complex motions. We achieved this by adjusting the chamber angle, ranging from 15 to 75 degrees, to optimize the bending and twisting movements through finite element analysis and experimental verification. We also investigated the variation trends in bending and twisting motions and determined the actuator’s workspace and maximum grasping force for a variety of objects with different shapes, materials, and sizes. Our findings suggest that PTBA is a promising candidate for advanced applications requiring intricate and bioinspired movements. This new design method offers a path toward achieving these goals.

The octopus has unique capacities are sources of inspiration in developing soft robotic‐enabling technologies. Herein, soft, sensorized, suction cups inspired by the suckers of Octopus vulgaris are presented. The suction cups using direct casting are fabricated, so that materials with different mechanical properties can be combined to optimize sensing and grasping capabilities. The artificial suckers integrate four embedded strain sensors, individually characterized and placed in a 90° configuration along the rim of the suction cup. Based on this arrangement, how well the sensory suction cup can detect 1) the direction and 2) the angle (from 30° to 90°) of a touched inclined surface and 3) the stiffness of a touched flat object (shore hardness between 0010 and D50) both in air and underwater is evaluated. Data processing on neural networks is based using a multilayer perceptron to perform regression on individual properties. The results show a mean absolute error of 0.98 for angles, 0.02 for directions, and 97.9% and 93.5% of accuracy for the material classification in air and underwater, respectively. In view of the results and scalability in manufacturing, the proposed artificial suckers would seem to be highly effective solutions for soft robotics, including blind exploration and object recognition.

Accommodation of mechanism with human being’s physical characteristics creates the possibility of safe and efficient interaction between human being and robot. Regarding the fact that amputation of a limb in human beings causes several mental, economical and social difficulties and problems, need to a substitute limb which has the most efficiency for the person after amputation is a vital need. The cable robots are the kinds of robots that the cable is used instead of rigid link. The cable robots have a simple appearance that some cables connect the motors to the final organ. In this research a robot with cable mover is designed and modeled as a tool in the case of creating movement with the most accordance for an artificial organ below the knee. In addition, in this mechanism some advantages are also considered including creating movement in two axes, its cheapness and lightness. In this research at first a primary design of the artificial organ is presented. The forward and inverse kinematic relations which are dominant on system are explained, in fact you can find different features with kinematic robots like dexterity, global condition, local condition, etc, and finally we study the available workspace for the system. Workspace in cable robots is different from other parallel robots, in this paper, first description about some methods for finding work­space in cable-driven-robots and then use of force-closure workspace to find workspace for this system are presented.