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Mechatronics
Is the word we use to refer to biologically-inspired hand with embedded electronics and sensors in the structure. A group of mechanical and electronic engineers work for the development of advanced devices integrating both sensors and electronics, in order to build stand-alone systems. Several working prototypes have been built at ARTS Lab since 2001.
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| [Backgrounds] [CyberHand] [RobotCUB Hand] [RPP Hand] [SmartHand] [TOP] |
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| The RTR1 hand is composed of a palm (realized in epoxy resin through STL) and three fingers prototypes (realized in ABS, acrylonitrile/butadiene/styrene through FDM): 2 equal fingers, composed by three phalanxes, and the third finger, which is in opposition, formed by two phalanges. The RTR1 hand weights ~250 grams.
This model of mechatronic hand has 6 independent degrees of freedom and 2 passive d.o.f. The sensory system is composed of:
- 6 position sensors for detecting the angular displacement of the active joints;
- 3 force sensor on the fingertips.
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The RTR 1 was developed by ARTS Lab in collaboration with INAIL since 2001.
Additional Resources
Detail of the inter-phalangeal movement and of the sensor output: MPEG movie, 1MB - download
Detail of the metacarpo-phalangeal movement and of the sensor output: MPEG movie, 1.9MB - download
RTR1 Hand in action - free movements: AVI movie, 4.5MB - download
RTR1 Hand in action - grasping an orange: AVI movie, 4.3MB - download
RTR1 Hand in action - grasping a sponge: AVI movie, 2.4MB - download
Related Publications
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| In the RTR2 hand, the actuation system is based on the concept of underactuation. In other words the fingers can self-adapt to the object shape with a simple movement of a slider linked to the finger through a steel wire. Two DC actuators (MINIMOTOR, CH), integrated in the palm, actuate the hand:
- the first (6 V, diameter: 10mm) is used only for the thumb positioning: thanks to a four linked mechanism the thumb can abduct and adduct;
- the second (6 V, diameter: 17mm) moves the slider and pulls the wires, in such a way that all the 3 fingers close together towards the object.
The RTR2 hand weights ~350 grams. The control system is embedded in the palm and its sensory system is composed of proprioceptive and exteroceptive sensors. The RTR 2 hand was developed by ARTS Lab in collaboration with INAIL since 2003. |
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| Cylindrical Palmar Prehension |
Prehension by subtermino-lateral opposition |
Prehension by terminal opposition |
An example showing the grasp adaptability |
additional resources
RTR2 Hand in action - pouring water in a glass: AVI movie, 2.8MB - download
RTR2 Hand in action - grasp stability: AVI movie, 2.12MB - download
RTR2 Hand in action - grasping a candy: AVI movie, 0.8MB - download
Related Publications
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| Also in the SPRING Hand, the actuation system is based on the concept of underactuation. One DC actuator (6 V, diameter: 17mm, MINIMOTOR CH), integrated in the palm, actuates the hand. The movement of the slider, bringing the wires in tension, causes the flexion of all the fingers. The SPRING hand weights ~400 grams. Its sensory system is composed of a tension sensor fixed to the slider in order to continuously monitor the cable tension applied by the motors. additional resources
SPRING Hand in action - free movements: AVI movie, 385KB - download
SPRING Hand in action - a functional grasp : AVI movie, 481KB - download
SPRING Hand in action - an adaptive grasp: AVI movie, 519KB - download Related Publications |
The SPRING Hand
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An example showing the grasp adaptability The SPRING hand was developed by ARTS Lab in collaboration with INAIL since 2004. |
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The SPRING Hand applied on an anthropomorphic arm |
| cylindrical palmar prehension |
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| Also in the Silicone Hand, the actuation system is based on the concept of underactuation. One DC actuator (6 V, diameter: 17mm, MINIMOTOR CH), integrated in the palm, actuates the hand. The movement of the slider, bringing the wires in tension, causes the flexion of all the fingers. The SPRING hand weights ~400 grams. Its sensory system is composed of a tension sensor fixed to the slider in order to continuously monitor the cable tension applied by the motors. The Silicone hand was developed by ARTS Lab in collaboration with INAIL since 2004. Related Publications |
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The Silicone Hand |
| The Hand mounted onto a clinical stump |
The Silicone Hand simulating a pinch grasp |
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| [Backgrounds] [CyberHand] [RobotCUB Hand] [RPP Hand] [SmartHand] [TOP] |
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The main objectives of the CYBERHAND Project (IST-FET 2001-35094) were to increase the basic knowledge of neural
regeneration, and sensory-motor control of the hand in humans and to exploit this knowledge to
develop a new kind of hand prosthesis in order to overcome some of the drawbacks of current
systems. The new prosthesis was aimed to:
- be felt by an amputee as the lost natural limb delivering her/him a natural sensory feedback by
means of the stimulation of some specific afferent nerves;
- be controlled in a very natural way by processing the efferent neural signals coming from the
central nervous system (reducing the discomfort of the current EMG-based control prosthesis).
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The CyberHand
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Comparison with the natural hand |
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In the CyberHand developed by ARTS Lab, the three fingered RTR2 hand has been redesigned. In order to improve the hand grasp functionality and its anthropomorphism, all the phalanges have a cylindrical shape without sharp edges. Their dimensions are much closer to the anthropomorphous ones and the proximal phalanges have a diameter of only 16 mm. Each finger is underactuated and the mechanism is the same of the RTR2.
The CyberHand was designed as a prototype for testing and evaluating neural interfaces, control algorithms and sensory feedback protocols. It has 16 DoFs and 6 motors (that is, 6 degrees of mobility, DoMs): each finger of the CyberHand has three DoFs and one DoM (flexion/extension) and the thumb has, in addition, 1 DoM for positioning. The size of the CyberHand is comparable to human hands and can generate many different grasps; its control is currently limited to a subset of functional grasps: lateral pinch, cylindrical and spherical grasps and the tripod grasp.
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The five motors for finger flexion are housed in a socket and occupy a total volume of ~ 250 cc, whereas the motor devoted to the thumb positioning is in the palm. The palm is composed by an outside shell, made of carbon fiber, divided into dorsal and volar parts, and by an inside frame, which holds the fingers and contains the thumb mechanism. A soft padding made of silicon rubber can be mounted on the palm in order to increase the compliance of the grasping. The total weight of the hand is about 320 grams , excluding the motors in the forearm and the cosmetic covering of the palm.
The design of the CyberHand took into account a number of features of the human hand that simplifies its replication. Most of the muscles are, for instance, located in the forearm. This reduces limb inertia, allows more room for the muscles, and permits fine manipulation of small objects. Moreover, in the natural hand, the transmission system consists of tendons that allow the muscles in the forearm to actuate the digits of the hand. Cable transmissions obviously make it possible to relocate bulky actuation and avoid problems due to rigid transmissions in articulated mechanism.
additional resources
CYBERHAND - example of the prono-supination of the wrist: AVI movie, 304KB - download
CYBERHAND - the 3D CAD model replicating the cylindrical palmar grasp of the human hand: AVI movie, 226KB - download
CYBERHAND - the 3D CAD model replicating the lateral grasp of the human hand: AVI movie, 368KB - download
CYBERHAND - the 3D CAD model replicating the pinch grasp of the human hand: AVI movie, 644KB - download
CYBERHAND - The three fingers can move in order to allow more complex grasps like the tridigital grip: AVI movie, 228KB - download
CYBERHAND - The CYBERHAND mimicking a gesture: AVI movie, 1960KB - download
CYBERHAND -The CYBERHAND grasping a plastic tomato: AVI movie, 3380KB - download
CYBERHAND - Handshake: AVI movie, 4060KB - download
Related Publications
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The socket containing motors and control electronics.
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CyberHand capabilities
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Current CyberHand mechatronics characteristics are here resumed. Mechanical characteristics:
- Number of DoFs: 16
- Number of DoMs (number of motors): 6 (1 for each finger + 1 for thumb abduction/adduction)
- Actuation type: DC motors
- Type of trasmission: tendons
- Trapezo-metacarpal thumb joint abduction/adduction range:0°-120°
- Finger joints flexion range: 0-90°
- Maximum grasping force: 40 N (during cylindrical grasp)
- Maximum tip to tip force: 15 N
- Grasping capabilities: cylindrical, spherical, lateral, tridigital, bidigital
- Weight of the hand structure: 320 grams (excluding the motors)
- Minimum closing time: 6 sec
Electronic characteristics:
- Number of position sensors: 21 (6 DC Motor built-in encoders + 15 joint hall sensors)
- Number of force sensors: 8 (3 three-component fingertip force sensors + 5 cable tension sensors)
- Number of touch sensors: 15 (1 for each phalanx)
- Grasping control type: position, velocity and force control.
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| [Backgrounds] [CyberHand] [RobotCUB Hand] [RPP Hand] [SmartHand] [TOP] |
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The main goals of the RobotCUB Project (IST-2004-004370) are to create a
physical platform for research that can be used by
researchers involved in embodied cognition, and to advance the understanding of several key issues in the investigation of several cognitive capabilities.
To enable the investigation of relevant cognitive aspects the robot should be able to explore the environment and to grasp and manipulate objects on the floor. It has to be pointed out that manipulation capabilities (obviously supported with sensors) are not considered only as a tool but also the main link between action and perception. Anyway as the room for the motors is a huge problem, a trade-off between the accomplishment of high-level manipulation tasks and the dimensional limitations is mandatory.
Eventually two typologies of finger have been developed, the fully under-actuated and the hybrid actuated ones.
Concerning the under-actuated joints, a pulling cable runs along the phalanges and around idle pulleys and flexes the finger and torsion springs (when the cable is released) extend the finger. According to the human hand physiology the proximal (PIP) and the distal interphalangeal (DIP) joints are coupled in all the fingers. |
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Developed RobotCUB prototype. |
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hallowing of the palm and the finger abduction permits to correctly wrap a mouse... |
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The little and the ring fingers are designed as fully under-actuated and coupled together. This is implemented using a differential mechanism placed in the palm. A motor pulling two tendons in an agonistic/antagonist way is the solution for controlling independently the MP joint in the hybrid fingers . This is a compact solution, even if cable pretension is mandatory. The number of DoMs/DoFs (8/14) of the thumb, index and middle fingers are enough for manipulation (if well controlled).
Related Publications
More info @ RobotCUB Project Webpage |
| [Backgrounds] [CyberHand] [RobotCUB Hand] [RPP Hand] [SmartHand] [TOP] |
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NON-AVAILABLE INFORMATION
Please come-back in a few days... |
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| [Backgrounds] [CyberHand] [RobotCUB Hand] [RPP Hand] [SmartHand] [TOP] |
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A five finger anthropomorphic hand prosthesis, employing robust sensors and electronics will be developed. The main requirement will be the hand assessment with amputees during the last year of the project. Since the majority of amputations are distal (quite near to wrist level), the prosthetic hand will employ a low number of motors fitted in a small volume package inside or nearby the palm. Characteristics such as grasping capabilities, robustness, cosmetics, small weight and human size will be preferred in respect to high dexterity, high power and manipulation capabilities. The prosthetic hand will be designed with a biomechatronic approach in order to mimic the functional anatomy of the musco-skeletal system and the natural motor control loop. The finger flexion/extension actuation will be based on underactuated and differential mechanisms and on torsion springs in order to reduce both encumbrance and weight. Moreover, the hand will have an opposable thumb in order to perform an high number of prehensile patterns such as lateral, bi-digital, tri-digital and cylindrical grasps, and will be actuated with a sensorized tendon driven transmission in order to decrease weight. |
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The SmartHand mechanical design: Five underactuated fingers are driven by four non-back-drivable actuation units based on DC-Motors. All fingers are made of 3 phalanxes and endowed with angular and grasping sensors. Thumb opposition axis positionin is also provided. |
More info @ SmartHand Project Webpage |
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