In this paper we introduce the Pisa/IIT SoftHand, a novel robot hand prototype designed with the purpose of being robust and easy to control as an industrial gripper, while exhibiting high grasping versatility and an aspect similar to that of the human hand. In the paper we briefly review the main theoretical tools used to enable such simplification, i.e. the neuroscience-based notion of soft synergies. A discussion of several possible actuation schemes shows that a straightforward implementation of the soft synergy idea in an effective design is not trivial. The approach proposed in this paper, called adaptive synergy, rests on ideas coming from underactuated hand design. A synthesis method to realize a desired set of soft synergies through the principled design of adaptive synergy is discussed. This approach leads to the design of hands accommodating in principle an arbitrary number of soft synergies, as demonstrated in grasping and manipulation simulations and experiments with a prototype. As a particular instance of application of the synthesis method of adaptive synergies, the Pisa/IIT SoftHand is described in detail. The hand has 19 joints, but only uses one actuator to activate its adaptive synergy. Of particular relevance in its design is the very soft and safe, yet powerful and extremely robust structure, obtained through the use of innovative articulations and ligaments replacing conventional joint design. The design and implementation of the prototype hand are shown and its effectiveness demonstrated through grasping experiments, reported also in the multimedia extension 1.

This article reports on the state of the art of artificial hands, discussing some of the field's most important trends and suggesting directions for future research. We review and group the most important application domains of robotic hands, extracting the set of requirements that ultimately led to the use of simplified actuation schemes and soft materials and structures—two themes that clearly emerge from our examination of developments over the past century. We provide a comprehensive analysis of novel technologies for the design of joints, transmissions, and actuators that enabled these trends. We conclude by discussing some important new perspectives generated by simpler and softer hands and their interaction with other aspects of hand design and robotics in general.

One of the motivations behind the development of humanoid robots is the will to comply with, and fruitfully integrate in the human environment, a world forged by humans for humans, where the importance of the hand shape dominates prominently.This paper presents the novel hand under-actuation framework which goes under the name of synergies. In particular two incarnations of this concept are considered, soft synergies and adaptive synergies. They are presented and their substantial equivalence is demonstrated.After this, it presents the first implementation of THE UNIPI-hand, a prototype which conciliates the idea of adaptive synergies for actuation with an high degree of integration, in a humanoid shape. The hand is validated experimentally through some grasps and measurements. Results are reported also in the attached video.

In recent years, a clear trend toward simplification emerged in the development of robotic hands. The use of soft robotic approaches has been a useful tool in this prospective, enabling complexity reduction by embodying part of grasping intelligence in the hand mechanical structure. Several hand prototypes designed according to such principles have accomplished good results in terms of grasping simplicity, robustness, and reliability. Among them, the Pisa/IIT SoftHand demonstrated the feasibility of a large variety of grasping tasks, by means of only one actuator and an opportunely designed tendon-driven differential mechanism. However, the use of a single degree of actuation prevents the execution of more complex tasks, like fine preshaping of fingers and in-hand manipulation. While possible in theory, simply doubling the Pisa/IIT SoftHand actuation system has several disadvantages, e.g., in terms of space and mechanical complexity. To overcome these limitations, we propose a novel design framework for tendon-driven mechanisms, in which the main idea is to turn transmission friction from a disturbance into a design tool. In this way, the degrees of actuation (DoAs) can be doubled with little additional complexity. By leveraging on this idea, we design a novel robotic hand, the Pisa/IIT SoftHand 2. We present here its design, modeling, control, and experimental validation. The hand demonstrates that by opportunely combining only two DoAs with hand softness, a large variety of grasping and manipulation tasks can be performed, only relying on the intelligence embodied in the mechanism. Examples include rotating objects with different shapes, opening a jar, and pouring coffee from a glass.

Soft robots are one of the most significant recent evolutions in robotics. They rely on compliant physical structures purposefully designed to embody desired characteristics. Since their introduction, they have shown remarkable applicability in overcoming their rigid counterparts in such areas as interaction with humans, adaptability, energy efficiency, and maximization of peak performance. Nonetheless, we believe that research on novel soft robot applications is still slowed by the difficulty in obtaining or developing a working soft robot structure to explore novel applications

Despite some prematurely optimistic claims, the ability of robots to grasp general objects in unstructured environments still remains far behind that of humans. This is not solely caused by differences in the mechanics of hands: indeed, we show that human use of a simple robot hand (the Pisa/IIT SoftHand) can afford capabilities that are comparable to natural grasping. It is through the observation of such human-directed robot hand operations that we realized how fundamental in everyday grasping and manipulation is the role of hand compliance, which is used to adapt to the shape of surrounding objects. Objects and environmental constraints are in turn used to functionally shape the hand, going beyond its nominal kinematic limits by exploiting structural softness.In this paper, we set out to study grasp planning for hands that are simple -in the sense of low number of actuated degrees of freedom (one for the Pisa/IIT SoftHand) -but are soft, i.e. continuously deformable in an infinity of possible shapes through interaction with objects. After general considerations on the change of paradigm in grasp planning that this setting brings about with respect to classical rigid multi-dof grasp planning, we present a procedure to extract grasp affordances for the Pisa/IIT SoftHand through physically accurate numerical simulations. The selected grasps are then successfully tested in an experimental scenario.

Many walking robot presented in literature stand on rigid flat feet, with a few notable exceptions that embed flexibility in their feet to optimize the energetic cost of walking. This paper proposes a novel adaptive robot foot design, whose main goal is to ease the task of standing and walking on uneven terrains. After explaining the rationale behind our design approach, we present the design of the SoftFoot, a foot able to comply with uneven terrains and to absorb shocks thanks to its intrinsic adaptivity, while still being able to rigidly support the stance, maintaining a rather extended contact surface, and effectively enlarging the equivalent support polygon. The paper introduces the robot design and prototype and presents preliminary validation and comparison versus a rigid flat foot with comparable footprint and sole

In this article, we study the feasibility of applying the SoftHand technology to a prosthetic device that is suitable for activities of daily living (ADL) and, in particular, some important objectives such as doing work, performing home chores, and participating in hobbies. These applications have specific requirements, such as high grip power; grasp versatility; ruggedness; resilience; resistance to water, dust, and temperature; durability; power autonomy; and low cost. Alternatively, factors like the multiplicity of gestures or aesthetics are less dominant. The intuitiveness of control by the user is a particularly relevant and specific objective of our work. While multiactivation-modalities prostheses use sophisticated myoelectric control to afford versatility and dexterity, most state-of-the-art work-oriented prostheses are body powered (BP). BP prostheses (BPPs) are intuitive to use, have low cost, do not require batteries or motors, and provide useful built-in, sensorless feedback to the user