can easily be integrated with electronics for signal processing, etc. by fabricating

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1 Glossary Active touch The process where objects are dynamically explored by a finger or hand as in object contour following. Adaptive thresholding A procedure in which a stimulus is interactively increased and decreased in amplitude to determine a threshold. Admittance A relation between force and resulting displacement. Afferent or sensory input Information from sensory receptors that is generated in the peripheral parts of the body and transmitted to the brain. Anatomical pulley An anatomical structure that is held to resemble a pulley; a soft tissue structure in which a tendon can run to change the direction of the pull. Arc length parameter A parameter that keeps track of the distance along an arc. Artificial neural network A machine learning technique that clusters information or approximates functions by transforming weighting and biasing of a number of inputs. Biomimetic Utilizing principles of design or function found in nature. Body representation Persistent information about an aspect of the body that is stored by the brain. Examples include information about body size or body position. Capture region The set of initial poses from which an object can be successfully grasped with a particular grasping strategy or routine. See also comfort zone. Catch-up response A characteristic pulse in grip (normal) force rate which is elicited by an unexpected perturbation of an object being grasped in a precision grip and results in a rapid initial increase in grip force. Central nervous system The part of the nervous system that consists of the brain and the spinal cord. Complementary metal oxide semiconductor (CMOS) A technology used commonly to make integrated circuits. Sensors made using the CMOS process R. Balasubramanian and V. J. Santos (eds.), The Human Hand as an Inspiration for Robot Hand Development, Springer Tracts in Advanced Robotics 95, DOI: / , Ó Springer International Publishing Switzerland

2 566 Glossary can easily be integrated with electronics for signal processing, etc. by fabricating them together. Comfort zone The set of object poses at the lift-off time point in a grasp acquisition action. See also capture region. Convex contour A shape that bends or curves outward. Corollary discharges Copies or corollaries of the motor command that originate in the motor areas of the cortex and are transmitted to the sensory centers in the brain that reflect the magnitude of the motor command generated. Corticofugal Descending fibers from motor cortex. Cortico-motoneuronal cell A neuron in the primary motor cortex with a descending axon that synapses directly on spinal motoneurons. Cortico-motoneuronal cells are found only in macaque monkeys, apes, humans. Curvature of an object The reciprocal of the radius of curvature at a given point on the object. Cutaneous Sensation derived from the skin or covering of a device or organism. Cutaneous mechanoreceptors Sensory receptors found in glabrous and hairy skin that respond to mechanical inputs such as pressure vibration and force. Damping The characteristic of matter or an arrangement of matter which resists velocity. Degrees of freedom (DOF) The number of variables required to specify the configuration of a mechanism. Often equal to the number of joints. Distal Near the end of a kinematic chain such as a finger. Dynamic range A measure of the maximum measurable value of a quantity (e.g. pressure or shear stress for a tactile sensor) typically limited by saturation, divided by the minimum measurable value, typically limited by the noise floor. Efference copy A copy of the motor command that is generated and received by the brain when it performs an action. The efference copy is used to process incoming sensory information by removing the component of the sensory information that is due to the action performed. Elastomer A flexible compliant polymer having rubber-like properties. Elbow flexors Muscles that are involved in flexing the elbow joint. Encoder A device for digital measurement of rotary or linear displacement. End-effector The rigid body segment or robot link of interest for task completion usually the most distal segment, e.g. the hand or palm segment for a manipulation task.

3 Glossary 567 Euler-Lagrange equation A differential equation whose solutions are the functions for which a given functional (a function that inputs a vector and returns a scalar) is stationary. In Lagrangian mechanics, a physical system s evolution is described by the solution to the Euler Lagrange equation for the system s action. Exploration Motion of a user s limbs (usually fingers) for the purpose of haptic detection or recognition of a target. Extensor hood A fibrous sheet on the posterior aspect of each finger; plexus of tendons with an aponeurotic sheet on the posterior aspect of the finger. Extrinsic finger or hand muscles These are muscles that act directly on the fingers but have their muscle bellies in the forearm and tendons that cross the wrist and palm to insert ultimately on the bones of the fingers (phalanges). Contraction of any of these muscles thus acts not only on certain fingers, but also tends to rotate the wrist. Some extrinsic finger muscles send tendons to more than one digit. In contrast, the intrinsic finger muscles have their bellies in the palm of the hand, and each acts on a single digit. Feasible force set The convex set in endpoint force space (normally 2-D or 3-D) that encloses all achievable force vectors based on the parameters of a tendondriven manipulator. Fingertip force vector angle The angle of the fingertip force vector with respect to the grip surface normal as viewed from the plane containing the grip axis. Gaussian mixture model regression A machine learning technique that clusters information or approximates functions by combining a number of Gaussian functions over a number of dimensions. Gaussian processes An advanced mathematical regression method to model nonlinear functions. Golgi tendon organs Receptors found at the junction between muscle fibers and tendons that respond to the forces developed in series by the muscle fibers and so provide the CNS with information regarding muscle force. Grasping posture The manipulator configuration at the lift-off time point. Grip axis Line connecting the fingertips in a two-finger precision grasp. Haptic inputs Sensory inputs arising from stimulation of receptors embedded in skin, muscles, tendons, and joints during active touch. Hysteresis Having the property that when a material is loaded and unloaded it does not follow exactly the same curve but instead forms a loop on a force/ displacement plot. The area of the loop is a measure of energy lost per loading/ unloading cycle. Impedance A measure of opposition to motion of a structure subjected to a force.

4 568 Glossary Individuated movements Movements in which the basic simultaneous motion of multiple body parts is modified such that one part moves more or differently than the others. Inertia The characteristic of matter or an arrangement of matter which resists acceleration. Intracortical microstimulation (ICMS) The delivery of small amounts of current (5 100 la) to extremely localized targets in cortex with the goal of activating s of neurons. Intrinsic hand muscles Muscles that take their origin and insertion within the hand. Jacobian matrix A matrix that maps values from one space to another space, such as joint angle velocities to manipulator endpoint velocities, or joint torques to manipulator endpoint forces and torques. Kinematic redundancy The characteristic of a mechanism which has more degrees of freedom than required to specify its end effector position and orientation. Kinesthesia Sense of limb movement that is derived from sensory receptors in muscle and skin. Kinesthetic feedback Force feedback involving muscle stimulation. Lagrange multipliers The method of Lagrange multipliers is a strategy for finding the local maxima and minima of a function subject to equality constraints. Lateral pinch A grasp in which the pad of the thumb is in contact with the lateral surface of the middle phalanx of the index finger, as when holding a key. Lift-off time point The first time when a grasped object is completely separated from the original support surface and completely supported by the manipulator. Material properties of an object Properties including stiffness, texture, and weight. Maximum isotropic value (MIV) The greatest possible force that a robotic finger or manipulator can exert in all directions (i.e., isotropically). Mechanoreceptor Nerve endings that respond to mechanical phenomena such as vibrations or local tissue strain. Mechanotransduction The mechanism by which mechanical stimulation and or deformation is converted to changes in membrane potential in mechanoreceptors.

5 Glossary 569 Meissner corpuscles Mechanoreceptors that are located near the surface of the skin, have small well-defined receptive fields, and respond to dynamic variations in skin curvature with a frequency range of tens of cycles per second. Minkowski sum In this the context of coordination patterns, it represents all possible positive or zero combinations of the collection of basis vectors for the tendons. Stated another way, it contains all possibilities of full or zero activation for all of the tendons. Moment arm The perpendicular distance from line of force application to the axis of rotation. Also, the mechanical advantage of a tendon over a joint. Moment arm matrix A matrix that contains information about all of the moment arms in a tendon-driven manipulator. Each row corresponds to a joint and each column to a specific tendon. The entries are the values of the moment arms. Motor unit Motor neuron and skeletal muscle fibers innervated by the same motor neuron. Motor-unit coherence Correlation in the discharge rate of pairs or groups of motor units within the same muscle or across different muscles. Motor-unit synchrony Temporal correlation between action potentials from two concurrently active motor units within the same muscle or across different muscles. Muscle synergy A group of muscles acting together concurrently in a fixed ratio. Muscle thixotropy A property of skeletal muscle fibres that results in the resting muscle having a stiffness or resistance to length changes. This property extends to intrafusal muscle fibres and thus affects the firing rate of muscle spindles. Musculotendon A unit composed of muscle and tendon. Neuroprosthetics Interfaces between the nervous system and electronic systems for the purpose of restoring some element of lost or reduced function. Nonprehensile Manual activities that do not involve grasping an object such as gestures made as part of normal speech or as a substitute for speech (sign language), and movements that involve depressing keys on a keyboard or musical instrument. Nonprehensile interaction Non-grasping contact or interaction where the object is not necessarily fixtured rigidly to the hand or end-effector. Object-moment External torque load imposed about the center of mass of a grasped object. Pacinian corpuscles Mechanoreceptors located beneath the skin with large receptive fields, and responding strongly to vibrations with frequencies of tens or hundreds of cycles per second, up to 1000 Hz.

6 570 Glossary Palmar pinch A grasp in which the pulp surface of the thumb opposes the finger pads of the index and middle finger. Passive joint impedance A resistive torque produced by joint rotation. Passive touch The process where objects are brought in contact with a passive finger or hand. Phantom limb The feeling that a body part exists when no sensory information about that body part is available to the brain. Many amputees experience a phantom of their amputated limb. That is, they continue to experience its presence despite its amputation. Experimental phantoms can be induced with anaesthesia. Here the subject feels the presence of the limb even when all sensory information is blocked from reaching the brain. Piezoelectric Having the property that the material acquires an electrical charge when subject to strain. Piezoresistive Having the property that the electrical resistance varies in proportion to strain. Posture The relative deposition of the body parts (i.e., a collection of joint angles). Power grip A grip that is used when force is the primary objective and there is a large area of contact between the object and the surfaces of the fingers and palm, such as when holding a hammer. Pre-grasp or preparatory interaction Contact or interaction that adjusts object placement in the environment prior to grasping and a primary manipulation task. Pre-grasp rotation Pre-grasp interaction where the object adjustment consists only of changes in the object orientation in the plane of the support surface. Prehensile Related to actions that involve the thumb and one or more fingers in grasping an object. Primary motor cortex (M1) The area of the cerebral cortex (Brodmann s cytoarchitectonic area 4) with the most direct projections to the motor centers of the brainstem and spinal cord, and hence the most direct control of body movement. In primates, this area lies directly in front of the central sulcus (Rolandic fissure). Axons descending from M1 provide the bulk of the cortical projection to the spinal cord, the corticospinal tract. Primary task or primary interaction The action following or requiring object acquisition in a grasp (e.g., transport of the object while fixtured in a grasp). Principle component analysis A mathematical method that linearly separates data along orthogonal dimensions according to variance.

7 Glossary 571 Proprioception A sense of the position and movement of the body as well as the forces and efforts involved in movement. The sense is used by the brain for conscious knowledge of the body as well as for the control of movement. The sensations and perceptions associated with the posture of the body, including torso, limbs, and hands/feet. Proximal Near the origin of a kinematic chain such as a finger. Psychophysical tests Controlled human subjects tests meant to elucidate how subjects perceive or respond to physical phenomena. PVDF Polyvinylidene fluoride. A polymer film that can be poled (placed under a strong electric field) making it piezoelectric. Rotational slip Slip between a digit and grip surface caused by torques about the axis perpendicular to a grip surface. Rubber hand illusion An illusion that manipulates the sense of ownership. By carefully controlling the location and timing of sensory information an experimenter can make a subject feel that a rubber hand is their own hand. Shape properties of an object Properties including size orientation and curvature. Size-weight illusion The size of an object influences the perceived weight of the same object. Somatosensation The set of senses arising from the body including touch vibration, pressure, movement, body movement, temperature, and pain. Static friction force The friction force between two solid objects that are not moving relative to each other. Stiffness The characteristic of matter or an arrangement of matter which resists displacement or deformation as a result of an applied force. Strain The stretching of a material defined as extension per unit length. Tactile feedback Cutaneous feedback relying on skin stimulation. Tactile sensor A device that measures physical effects arising from contact with objects and surfaces. Taxel One element of an array of tactile sensing elements analogous to a pixel in graphics. Tendon-driven system Any mechanical system that is actuated (either actively or passively) with tendons that can only pull and not push (e.g., wires, cables, strings). Tendon routing The configuration in which the tendons are arranged in a tendondriven system.

8 572 Glossary Texture of an object Properties of object surface including but not limited to roughness. Thermistor An electronic device whose resistance varies with temperature. Threshold A level of sensory amplitude at which a feature can just be detected. Tip pinch A grip that involves holding small object between the pulps of the opposed thumb and index finger. Vertical-horizontal illusion The tendency to overestimate the length of a vertical line compared to a horizontal line of the same length. Vibrissae Whiskers of animals that can sense light contacts and vibrations. Weber fraction For many sensory modalities the change in stimulus intensity that can be discriminated is a constant fraction of the intensity of the stimulus. This number is known as the Weber fraction.