Cristina Piazza

Adaptive synergies for the design and control of the Pisa/IIT SoftHand

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 1 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 multimedia extension.

Adaptive synergies for a humanoid robot hand

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.

Grasping with Soft Hands

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.

SoftHand Pro-D: Matching dynamic content of natural user commands with hand embodiment for enhanced prosthesis control

State of the art of hand prosthetics is divided between simple and reliable gripper-like systems and sophisticate hi-tech poly-articular hands which tend to be complex both in their design and for the patient to operate. In this paper, we introduce the idea of decoding different movement intentions of the patient using the dynamic frequency content of the control signals in a natural way. We move a step further showing how this idea can be embedded in the mechanics of an underactuated soft hand by using only passive damping components. In particular we devise a method to design the hand hardware to obtain a given desired motion. This method, that we call of the dynamic synergies, builds on the theory of linear descriptor systems, and is based on the division of the hand movement in a slow and a fast components. We use this method to evolve the design of the Pisa/IIT SoftHand in a prototype prosthesis which, while still having 19 degrees of freedom and just one motor, can move along two different synergistic directions of motion (and combinations of the two), to perform either a pinch or a power grasp. Preliminary experimental results are presented, demonstrating the effectiveness of the proposed design.

The Quest for Natural Machine Motion: An Open Platform to Fast-Prototyping Articulated Soft Robots

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.

The SoftHand Pro-H: A Hybrid Body-Controlled, Electrically Powered Hand Prosthesis for Daily Living and Working

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.

Toward an adaptive foot for natural walking

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.

SoftHand at the CYBATHLON: a user’s experience

BackgroundRoughly one-quarter of upper limb prosthesis users reject their prosthesis. Reasons for rejection range from comfort, to cost, aesthetics, function, and more. This paper follows a single user from training with and testing of a novel upper-limb myoelectric prosthesis (the SoftHand Pro) for participation in the CYBATHLON rehearsal to training for and competing in the CYBATHLON 2016 with a figure-of-nine harness controlled powered prosthesis (SoftHand Pro-H) to explore the feasibility and usability of a flexible anthropomorphic prosthetic hand.MethodsThe CYBATHLON pilot took part in multiple in-lab training sessions with the SoftHand Pro and SoftHand Pro-H; these sessions focused on basic control and use of the prosthetic devices and direct training of the tasks in the CYBATHLON. He used these devices in competition in the Powered Arm Prosthesis Race in the CYBATHLON rehearsal and 2016 events.ResultsIn training for the CYBATHLON rehearsal, the subject was able to quickly improve performance with the myoelectric SHP despite typically using a body-powered prosthetic hook. The subject improved further with additional training using the figure-of-nine harness-controlled SHPH in preparation for the CYBATHLON. The Pilot placed 3rd (out of 4) in the rehearsal. In the CYBATHLON, he placed 5th (out of 12) and was one of only two pilots who successfully completed all tasks in the competition, having the second-highest score overall.ConclusionsResults with the SoftHand Pro and Pro-H suggest it to be a viable alternative to existing anthropomorphic hands and show that the unique flexibility of the hand is easily learned and exploited.

Preliminary Results Toward Continuous and Proportional Control of a Multi-synergistic Soft Prosthetic Hand

State of art of modern hand prosthesis is populated by sophisticate hi-tech poly-articular hands which usually offer a broader set of movement capabilities, with the possibility to control up to 4 or 5 motors and achieve several different postures. Unfortunately these device are not so easy to control. A novel emerging trend is oriented towards a strong simplification of the mechanical design (through i.e. underactuation mechanisms), but still maintaining a good level of performance. A successful example is the SoftHand2 Pro, a 19 Degrees of Freedom (DoF) anthropomorphic hand which, using two motors, can move along two different synergistic directions, to perform either power grasp, precision grasp and index point. The combination of this multi-synergistic prosthetic hand with advanced controls, as myoelectric pattern recognition algorithms, allows to get promising results toward a more natural and intuitive control, introducing novel features as the possibility of a continuous switch between gestures. Preliminary experimental results are presented, demonstrating the effectiveness of the idea.

The SoftPro Project: Synergy-Based Open-Source Technologies for Prosthetics and Rehabilitation

Robotics-enabled technologies for assistive and rehabilitative applications have gained an increasing attention, both in academic and industrial research settings, as a promising solution for human sensory-motor system recovery. However, many constraints remain that limit their effective employment in everyday-life, mainly related to cost, usability and users’ acceptance. The Softpro project proposes to completely reverse such paradigm, starting from the analysis of the needs from patients and the careful investigation of the sensory-motor human behaviour, capitalizing on the framework of synergistic control and soft robotics. The final goal is to study and design simple, effective and affordable soft synergy-based robotic technologies for the upper limb, such as new prostheses, exoskeletons, and assistive devices which can be useful and accessible to a wide audience of users. To pursue such an ambitious objective, SoftPro has put together research groups who laid the neuroscientific and technological fundamentals underpinning the project approach, a net of international collaborations and numerous and qualified industrial partners, which is expected to produce a strong impact on both research and innovation.