Maria Chiara Carrozza

Restoring Natural Sensory Feedback in Real-Time Bidirectional Hand Prostheses

A multigrasp, bidirectional hand prosthesis delivers dynamic sensory feedback, allowing a user with a hand amputation to achieve fine grasping force control and realistic object sensing. An Artificial Hand’s Sense of Touch To feel the hard curvature of a baseball or the soft cylinder that is a soda can—these sensations we often take for granted. But amputees with a prosthetic arm know only that they are holding an object, the shape and stiffness discernible only by eye or from experience. Toward a more sophisticated prosthetic that can “feel” an object, Raspopovic and colleagues incorporated a feedback system connected to the amputee’s arm nerves, which delivers sensory information in real time. The authors connected electrodes in the arm nerves to sensors in two fingers of the prosthetic hand. To “feel” an object, the electrodes delivered electrical stimuli to the nerves that were proportional to the finger sensor readouts. To grasp an object and perform other motor commands, muscle signals were decoded. This bidirectional hand prosthetic was tested in a single amputee who was blindfolded and acoustically shielded to assure that sound and vision were not being used to manipulate objects. In more than 700 trials, the subject showed that he could modulate force and grasp and identify physical characteristics of different types of objects, such as cotton balls, an orange, and a piece of wood. Such sensory feedback with precise control over a hand prosthetic would allow amputees to more freely and naturally explore their environments. Hand loss is a highly disabling event that markedly affects the quality of life. To achieve a close to natural replacement for the lost hand, the user should be provided with the rich sensations that we naturally perceive when grasping or manipulating an object. Ideal bidirectional hand prostheses should involve both a reliable decoding of the user’s intentions and the delivery of nearly “natural” sensory feedback through remnant afferent pathways, simultaneously and in real time. However, current hand prostheses fail to achieve these requirements, particularly because they lack any sensory feedback. We show that by stimulating the median and ulnar nerve fascicles using transversal multichannel intrafascicular electrodes, according to the information provided by the artificial sensors from a hand prosthesis, physiologically appropriate (near-natural) sensory information can be provided to an amputee during the real-time decoding of different grasping tasks to control a dexterous hand prosthesis. This feedback enabled the participant to effectively modulate the grasping force of the prosthesis with no visual or auditory feedback. Three different force levels were distinguished and consistently used by the subject. The results also demonstrate that a high complexity of perception can be obtained, allowing the subject to identify the stiffness and shape of three different objects by exploiting different characteristics of the elicited sensations. This approach could improve the efficacy and “life-like” quality of hand prostheses, resulting in a keystone strategy for the near-natural replacement of missing hands.

Design of a cybernetic hand for perception and action

Strong motivation for developing new prosthetic hand devices is provided by the fact that low functionality and controllability—in addition to poor cosmetic appearance—are the most important reasons why amputees do not regularly use their prosthetic hands. This paper presents the design of the CyberHand, a cybernetic anthropomorphic hand intended to provide amputees with functional hand replacement. Its design was bio-inspired in terms of its modular architecture, its physical appearance, kinematics, sensorization, and actuation, and its multilevel control system. Its underactuated mechanisms allow separate control of each digit as well as thumb–finger opposition and, accordingly, can generate a multitude of grasps. Its sensory system was designed to provide proprioceptive information as well as to emulate fundamental functional properties of human tactile mechanoreceptors of specific importance for grasp-and-hold tasks. The CyberHand control system presumes just a few efferent and afferent channels and was divided in two main layers: a high-level control that interprets the user’s intention (grasp selection and required force level) and can provide pertinent sensory feedback and a low-level control responsible for actuating specific grasps and applying the desired total force by taking advantage of the intelligent mechanics. The grasps made available by the high-level controller include those fundamental for activities of daily living: cylindrical, spherical, tridigital (tripod), and lateral grasps. The modular and flexible design of the CyberHand makes it suitable for incremental development of sensorization, interfacing, and control strategies and, as such, it will be a useful tool not only for clinical research but also for addressing neuroscientific hypotheses regarding sensorimotor control.

Robotic techniques for upper limb evaluation and rehabilitation of stroke patients

This paper presents two robot devices for use in the rehabilitation of upper limb movements and reports the quantitative parameters obtained to characterize the rate of improvement, thus allowing a precise monitoring of patients recovery. A one degree of freedom (DoF) wrist manipulator and a two-DoF elbow-shoulder manipulator were designed using an admittance control strategy; if the patient could not move the handle, the devices completed the motor task. Two groups of chronic post-stroke patients (G1 n=7, and G2 n=9) were enrolled in a three week rehabilitation program including standard physical therapy (45 min daily) plus treatment by means of robot devices, respectively, for wrist and elbow-shoulder movements (40 min, twice daily). Both groups were evaluated by means of standard clinical assessment scales and a new robot measured evaluation metrics that included an active movement index quantifying the patients ability to execute the assigned motor task without robot assistance, the mean velocity, and a movement accuracy index measuring the distance of the executed path from the theoretic one. After treatment, both groups improved their motor deficit and disability. In G1, there was a significant change in the clinical scale values (p<0.05) and range of motion wrist extension (p<0.02). G2 showed a significant change in clinical scales (p<0.01), in strength (p<0.05) and in the robot measured parameters (p<0.01). The relationship between robot measured parameters and the clinical assessment scales showed a moderate and significant correlation (r>0.53 p<0.03). Our findings suggest that robot-aided neurorehabilitation may improve the motor outcome and disability of chronic post-stroke patients. The new robot measured parameters may provide useful information about the course of treatment and its effectiveness at discharge.

Biomechatronic Design and Control of an Anthropomorphic Artificial Hand for Prosthetic and Robotic Applications

This paper proposes a biomechatronic approach to the design of an anthropomorphic artificial hand able to mimic the natural motion of the human fingers. The hand is conceived to be applied to prosthetics as well as to humanoid and personal robotics; hence, anthropomorphism is a fundamental requirement to be addressed both in the physical aspect and in the functional behavior. In this paper, a biomechatronic approach is addressed to harmonize the mechanical design of the anthropomorphic artificial hand with the design of the hand control system. More in detail, this paper focuses on the control system of the hand and on the optimization of the hand design in order to obtain a human-like kinematics and dynamics. By evaluating the simulated hand performance, the mechanical design is iteratively refined. The mechanical structure and the ratio between number of actuators and number of degrees of freedom (DOFs) have been optimized in order to cope with the strict size and weight constraints that are typical of application of artificial hands to prosthetics and humanoid robotics. The proposed hand has a kinematic structure similar to the natural hand featuring three articulated fingers (thumb, index, and middle finger with 3 DOF for each finger and 1 DOF for the abduction/adduction of the thumb) driven by four dc motors. A special underactuated transmission has been designed that allows keeping the number of motors as low as possible while achieving a self-adaptive grasp, as a result of the passive compliance of the distal DOF of the fingers. A proper hand control scheme has been designed and implemented for the study and optimization of hand motor performance in order to achieve a human-like motor behavior. To this aim, available data on motion of the human fingers are collected from the neuroscience literature in order to derive a reference input for the control. Simulation trials and computer-aided design (CAD) mechanical tools are used to obtain a finger model including its dynamics. Also the closed-loop control system is simulated in order to study the effect of iterative mechanical redesign and to define the final set of mechanical parameters for the hand optimization. Results of the experimental tests carried out for validating the model of the robotic finger, and details on the process of integrated refinement and optimization of the mechanical structure and of the hand motor control scheme are extensively reported in the paper.

Design and development of an underactuated prosthetic hand

Current prosthetic hands are basically simple grippers with one or two degrees of freedom, which barely restore the capability of the thumb-index pinch. Although most amputees consider this performance as acceptable for usual tasks, there is ample room for improvement by exploiting recent progresses in mechatronic design and technology. This paper focus on an innovative approach for the design and development of prosthetic hands based on underactuated mechanisms. Furthermore, it describes the development and a preliminary analysis of a first prototype of an underactuated prosthetic hand.

The SPRING Hand: Development of a Self-Adaptive Prosthesis for Restoring Natural Grasping

Commercially available prosthetic hands are simple grippers with one or two degrees of freedom; these pinch type devices have two rigid fingers in opposition to a rigid thumb. This paper focuses on an innovative approach for the design of a myoelectric prosthetic hand. The new prosthesis features underactuated mechanisms in order to achieve a natural grasping behavior and a good distribution of pinching forces. In this paper it is shown that underactuation allows reproducing most of the grasping behaviors of the human hand, without augmenting the mechanical and control complexity.

Micro-systems in biomedical applications

In this paper we analyse the main characteristics of some micro-devices which have been developed recently for biomedical applications. Among the many biomedical micro-systems proposed in the literature or already on the market, we have selected a few which, in our opinion, represent particularly well the technical problems to be solved, the research topics to be addressed and the opportunities offered by micro-system technology (MST) in the biomedical field. For this review we have identified four important areas of application of micro-systems in medicine and biology: (1) diagnostics; (2) drug delivery; (3) neural prosthetics and tissue engineering; and (4) minimally invasive surgery. We conclude that MST has the potential to play a major role in the development of new medical instrumentation and to have a considerable industrial impact in this field.

The SmartHand transradial prosthesis

BackgroundProsthetic components and control interfaces for upper limb amputees have barely changed in the past 40 years. Many transradial prostheses have been developed in the past, nonetheless most of them would be inappropriate if/when a large bandwidth human-machine interface for control and perception would be available, due to either their limited (or inexistent) sensorization or limited dexterity. SmartHand tackles this issue as is meant to be clinically experimented in amputees employing different neuro-interfaces, in order to investigate their effectiveness. This paper presents the design and on bench evaluation of the SmartHand.MethodsSmartHand design was bio-inspired in terms of its physical appearance, kinematics, sensorization, and its multilevel control system. Underactuated fingers and differential mechanisms were designed and exploited in order to fit all mechatronic components in the size and weight of a natural human hand. Its sensory system was designed with the aim of delivering significant afferent information to the user through adequate interfaces.ResultsSmartHand is a five fingered self-contained robotic hand, with 16 degrees of freedom, actuated by 4 motors. It integrates a bio-inspired sensory system composed of 40 proprioceptive and exteroceptive sensors and a customized embedded controller both employed for implementing automatic grasp control and for potentially delivering sensory feedback to the amputee. It is able to perform everyday grasps, count and independently point the index. The weight (530 g) and speed (closing time: 1.5 seconds) are comparable to actual commercial prostheses. It is able to lift a 10 kg suitcase; slippage tests showed that within particular friction and geometric conditions the hand is able to stably grasp up to 3.6 kg cylindrical objects.ConclusionsDue to its unique embedded features and human-size, the SmartHand holds the promise to be experimentally fitted on transradial amputees and employed as a bi-directional instrument for investigating -during realistic experiments- different interfaces, control and feedback strategies in neuro-engineering studies.

A microrobotic system for colonoscopy

Colonoscopy is an important procedure for the diagnosis of various pathologies, in particular cancer of the colon and of the rectum, the second most malignant tumor in industrialized countries. At present however, colonoscopy is a procedure often painful for the patient and complex for the doctor. This is mainly due to the characteristics of current colonoscopes, which are quite rigid and require the doctor to perform difficult maneuvers for insertion. In this paper we present the concept and describe the design and fabrication of a new system for colonoscopy based on a microrobot capable of being propelled semi-autonomously along the colon. The microrobot system comprises a mothership incorporating devices for clamping the colon wall and tools for diagnosis and intervention. The actuation system is based on purposely developed shape memory alloy (SMA) pneumatic microvalves. A human/machine interface allows the doctor to teleoperate or supervise the functioning of the microrobot and to receive visual and other information during endoscopy. Particular attention has been paid to investigating a reliable and safe method of locomotion and to develop an efficient clamping system for the microrobot. The resulting configuration of the microrobot is very simple and potentially suitable for real clinical application. A prototype microrobot system has been tested in vitro with promising results.

Intention-Based EMG Control for Powered Exoskeletons

Electromyographical (EMG) signals have been frequently used to estimate human muscular torques. In the field of human-assistive robotics, these methods provide valuable information to provide effectively support to the user. However, their usability is strongly limited by the necessity of complex user-dependent and session-dependent calibration procedures, which confine their use to the laboratory environment. Nonetheless, an accurate estimate of muscle torque could be unnecessary to provide effective movement assistance to users. The natural ability of human central nervous system of adapting to external disturbances could compensate for a lower accuracy of the torque provided by the robot and maintain the movement accuracy unaltered, while the effort is reduced. In order to explore this possibility, in this paper we study the reaction of ten healthy subjects to the assistance provided through a proportional EMG control applied by an elbow powered exoskeleton. This system gives only a rough estimate of the user muscular torque but does not require any specific calibration. Experimental results clearly show that subjects adapt almost instantaneously to the assistance provided by the robot and can reduce their effort while keeping full control of the movement under different dynamic conditions (i.e., no alterations of movement accuracy are observed).