Skeletally-coupled finger-mounted navigation device and method

Abstract

A wearable navigation device 10 is disclosed comprising a rigid chassis configured to non-rotatably engage a digit phalanx, a motion sensing suite 32 coupled to the chassis, and a processor 34 configu

Description

Field of the Invention The present invention relates to human-computer interface devices. More particularly, the invention relates to a finger-mounted navigation device configured to mechanically couple to a digit phalanx and generate control signals for digital interface navigation based on skeletal-referenced motion. BACKGROUND OF THE INVENTION Digital interface navigation is commonly performed using hand-operated input devices such as computer mice, trackpads, touchscreens, and scroll wheels. These devices typically rely on translation of a hand-held object across a support surface, capacitive touch interaction, or free-space gesture detection. Conventional computer mice provide high positional accuracy by referencing movement against a static planar surface. However, use of such devices requires a dedicated support surface and often necessitates repositioning of the entire hand, which may contribute to repetitive strain over prolonged use. Trackpads and touchscreens allow direct contact-based interaction but require displacement of a finger across a sensing surface. Such interfaces may lack tactile anchoring and may introduce unintended cursor movement during selection events. Wearable ring-based input devices have been proposed that utilize inertial measurement units (IMUs) to detect finger gestures in free space. However, such systems typically interpret probabilistic gesture patterns and often lack a mechanically stabilised reference to skeletal articulation. As a result, translational movement of the arm or wrist may introduce signal noise or unintended displacement. There remains a need for a wearable navigation device that is mechanically stabilised relative to skeletal motion of a finger, capable of isolating rotational articulation from proximal limb movement, and configured to provide precise sequential navigation and selection control without requiring a planar gliding surface. SUMMARY OF THE INVENTION According to a first aspect of the invention, there is provided a wearable navigation device configured to mechanically couple to a digit phalanx of a user such that motion of the device corresponds directly to skeletal articulation of the engaged phalanx. The device comprises a rigid chassis configured to non-rotatably engage the phalanx, at least one motion sensing suite coupled to the chassis, and a control processor configured to establish a skeletal reference frame derived from the orientation of the engaged phalanx. The processor is configured to isolate rotational articulation of the phalanx relative to the skeletal reference frame from translational movement of the arm or wrist. In a primary operating mode, the processor maps the isolated rotational articulation to one-dimensional sequential navigation within a graphical user interface while suppressing two-dimensional pointer displacement. The device is further configured to detect a transient inertial impulse signature associated with a deliberate phalangeal action and to generate a selection command in response. During detection of the impulse, the processor temporarily suppresses navigation output to prevent unintended displacement resulting from the impulse itself. In certain embodiments, the internal passage of the chassis comprises an asymmetric or non-circular geometry configured to resist axial rotation of the device relative to the phalanx. In other embodiments, a secondary motion sensor may be provided at a proximal anatomical location to define the skeletal reference frame via differential orientation. The invention thereby provides a mechanically stabilised, skeletally-referenced navigation architecture capable of precise sequential control and selection without requiring planar surface translation. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Figure 1 illustrates a perspective view of a finger-mounted navigation device engaged with a digit phalanx. Figure 2 illustrates a transverse cross-sectional view of the device showing a skeletal engagement structure and internal passage configured to resist rotational displacement relative to the phalanx. Figure 3 illustrates a block diagram of the electronic architecture of the device, including a motion sensing module, processing unit, memory, communication interface, power source, and feedback module. Figure 4 illustrates a functional diagram showing mapping of rotational articulation of the digit about a longitudinal axis to sequential navigation within a digital interface. Figure 5 illustrates detection of a transient inertial impulse and generation of a selection event, including temporary suppression of navigation output during the impulse detection interval. Figure 6A-6D illustrate perspective views of alternative chassis embodiments for engaging the digit, including saddle, saddle-ring hybrid, C-clip, and split-ring configurations. Figure 7 illustrates stabilisation detection based on reduced translational motion variance when the device is supported on a surface, and activation of a precision navigation mode in response to the stabilised state. DETAILED DESCRIPTION Core Architecture Referring initially to Figure 1, a wearable navigation device (10) is configured to engage a digit phalanx (12) of a user. In the illustrated embodiment, the device is dimensioned to engage a middle phalanx, although engagement with other phalangeal segments is contemplated. The device comprises a rigid chassis (14) defining an internal passage (16) configured to receive the phalanx. The internal passage is structured to mechanically couple the chassis to skeletal articulation of the phalanx such that rotation of the phalanx results in corresponding rotation of the chassis. In certain embodiments, rotational stabilisation of the chassis relative to the phalanx is achieved through longitudinal skeletal abutment extending along a portion of the phalanx length. Such stabilisation may occur independently of, or in addition to, circumferential compression forces. In contrast to a conventional annular ring that primarily resists rotation through radial compression against soft tissue, the present engagement structure derives torsional stability from structural engagement aligned with the longitudinal axis of the phalanx. In certain embodiments, the internal passage (16) comprises a non-circular or asymmetric geometry configured to resist axial rotation of the chassis relative to the phalanx. As shown in Figure 2, the internal passage may include one or more planar facets (18) configured to abut lateral aspects of the phalanx. A resilient liner may optionally be provided to improve conformity while maintaining anti-rotational coupling. The device further comprises a motion sensing module (32), which may include one or more inertial measurement units (IMUs), accelerometers, gyroscopes, or magnetometers, rigidly coupled to the chassis. Because the motion sensing suite is mechanically coupled to the skeletal structure of the engaged phalanx, motion data corresponds to skeletal articulation rather than free-space gesture motion. A processing unit (34) is provided in communication with the motion sensing suite (20). The processor is configured to establish a skeletal reference frame derived from orientation data of the engaged phalanx. In certain embodiments, the stabilisation detection module (44) may be implemented as a software component executed by the processing unit (34). In certain embodiments, the internal engagement structure is configured as a skeletal saddle extending along a longitudinal portion of the engaged phalanx. The engagement structure may include opposing lateral contact regions configured to abut corresponding lateral anatomical surfaces of the phalanx. By engaging opposing sides of the phalanx, torsional displacement of the chassis relative to skeletal articulation is mechanically resisted during flexion and extension movements. In certain embodiments, the device includes a vibration sensor or acoustic sensor coupled to the chassis, such as a piezoelectric element, contact microphone, or an accelerometer configured to detect high-frequency vibration, to sense a bone-conducted vibration or acoustic transient associated with a deliberate tap or impact. The processor may require temporal coincidence between the inertial impulse event and the bone-conducted vibration / acoustic transient within a predefined coincidence window to confirm selection intent and reduce false positives. In certain embodiments, the skeletal engagement structure extends along the longitudinal axis of the phalanx over an axial span sufficient to resist torsional displacement through structural contact aligned with the bone axis. The axial span may correspond to a substantial portion of the phalanx length such that rotational stability is achieved through longitudinal skeletal abutment rather than reliance solely on radial compression against soft tissue. The engagement structure may extend across at least a predetermined portion of the phalanx length to increase rotational stability. In certain embodiments, the chassis constrains rotational micro-slip about the longitudinal axis of the phalanx such that angular motion detected by the motion sensing suite corresponds directly to bone-referenced articulation rather than relative motion between the device and soft tissue. The mechanical coupling thereby establishes a bone-aligned reference orientation from which articulation can be derived with reduced contamination from surface slippage or device rotation about the digit circumference. Skeletal Reference and Motion Isolation The processor (22) is configured to analyse motion data from the motion sensing module (32) to determine rotational articulation of the engaged phalanx relative to the established skeletal reference frame. Because the chassis (14) is non-rotatably coupled to the phalanx (12), rotational movement of the phalanx produces corresponding rotational signals in the motion sensing suite. Translational movement of the arm, wrist, or hand produces a distinct motion profile. In certain embodiments, the processor applies signal processing techniques to isolate rotational articulation from translational limb motion. Such techniques may include frequency-based filtering, axis discrimination, inertial modelling, or combinations thereof. Rotational articulation associated with phalangeal flexion and extension typically produces higher-frequency angular change relative to lower-frequency proximal limb translation, permitting separation of signal components. Isolation of rotational articulation relative to the skeletal reference frame reduces contamination from proximal limb movement and improves control precision. Primary Operating Mode - One-Dimensional Sequential Navigation In a primary operating mode, the processor maps isolated rotational articulation of the phalanx to one-dimensional sequential navigation within a graphical user interface. In this mode, two-dimensional pointer displacement is suppressed. Sequential navigation may correspond to scrolling through a document, traversing image slices, advancing frames within a dataset, navigating a timeline, or other linear index traversal. In certain embodiments, mapping between rotational articulation and sequential navigation employs a non-linear transfer function. The transfer function may provide fine incremental control at low angular velocities and accelerated traversal at higher angular velocities. By suppressing pointer displacement in the primary operating mode, unintended cursor drift during sequential navigation is reduced. In operation, the device does not require translation across a planar support surface to generate navigation input. In certain embodiments, the processor operates in a default indexed navigation state in which two-dimensional pointer displacement is disabled. In this state, rotational articulation about the longitudinal axis of the phalanx is interpreted exclusively as incremental traversal through a linear index space. This architecture differs from continuous two-dimensional cursor tracking in that control input is constrained to a single navigation dimension unless an explicit state transition is invoked. The default indexed navigation state reduces unintended displacement caused by multi-axis limb motion and permits fine sequential control independent of planar surface translation. Impulse Detection and Selection Command Generation The device is further configured to detect a transient inertial impulse signature associated with a deliberate phalangeal action. In certain embodiments, the impulse signature corresponds to a rapid, short-duration acceleration event generated by a controlled finger action such as a tap event, abrupt directional halt, or rapid articulation of the digit. The processor classifies the impulse based on waveform characteristics including magnitude, duration, directional vector, or frequency content. Upon detection of a qualifying impulse signature exceeding a predefined threshold, the processor generates a selection command. To reduce unintended displacement caused by the impulse itself, the processor temporarily suppresses navigation output during a defined temporal window surrounding the impulse event. The suppression window may extend before, during, and / or immediately after the impulse detection interval. By filtering displacement output during the impulse window, the device reduces cursor jitter or index shift that would otherwise result from the physical selection action. Different impulse directions or waveform profiles may optionally correspond to different command types. In certain embodiments, the processor defines a temporal impulse window surrounding detection of a qualifying inertial impulse event. During this window, navigation output derived from articulation signals is temporarily gated such that rotational motion occurring contemporaneously with the impulse does not generate navigation displacement. Following expiration of the impulse window, indexed navigation resumes. This mutually exclusive temporal gating architecture separates selection execution from navigation traversal. Stabilisation Detection and Surface Interaction In certain embodiments, the processor detects a stabilised state of the hand based on reduced translational motion variance. A stabilised state may occur when the user’s hand rests upon a support surface, such as a table, armrest, or other structure. Surface contact may be identified through characteristic vibration signatures, damping patterns, or reduction in translational acceleration noise. When a stabilised state is detected, the processor may increase sensitivity of rotational articulation mapping or modify gain parameters to provide finer control. This adaptive sensitivity enhances precision when the hand is supported while maintaining stability during free-space operation. Differential Skeletal Referencing In certain embodiments, a secondary motion sensor may be positioned at a proximal anatomical location relative to the engaged phalanx. The skeletal reference frame may be derived at least in part from differential orientation between the motion sensing suite mounted on the phalanx and the secondary motion sensor. Differential orientation permits compensation for proximal limb rotation and reduces influence of wrist or forearm motion on detection of phalangeal articulation. The secondary motion sensor may be integrated into a wrist-mounted apparatus, glove, band, or other wearable structure. In alternative embodiments, differential reference may be derived from a fixed environmental reference or gravitational vector calibration. System Integration, Calibration, and Power Management The device may further comprise a wireless communication module configured to transmit navigation and command signals to an external electronic system. In certain embodiments, output may be formatted as a Human Interface Device (HID) signal compatible with standard computing systems. An onboard power source may be provided within the chassis. The processor may transition between active and low-power states based on detection of a predefined kinetic signature, orientation change, or inactivity threshold. In certain embodiments, a calibration routine is performed to align the skeletal reference frame with a known orientation of the phalanx relative to gravity or a support surface. Calibration may occur automatically upon detection of a stable resting orientation. A haptic actuator may optionally be included to provide tactile feedback corresponding to discrete sequential navigation increments or command execution. In multi-digit embodiments, motion data from a plurality of devices mounted on different digits may be aggregated to execute compound commands or multi-axis navigation functions. Features described in relation to any embodiment may be combined with features of other embodiments unless incompatible.

Claims

CLAIMSIndependent Device Claim1.A wearable navigation device comprising:a chassis configured to mechanically couple to a digit of a user;a motion sensing module configured to detect motion of the digit;a processing unit in communication with the motion sensing module; anda communication interface configured to transmit control signals to an external computing device,wherein the processing unit is configured to:a) establish a skeletal reference frame corresponding to an orientation of the engaged digit;b) detect rotational articulation of the digit about a longitudinal axis of the digit;c) map the detected rotational articulation to one-dimensional sequential navigation of a digital interface;d) detect a transient inertial impulse generated by the digit; ande) generate a selection command in response to the transient inertial impulse, wherein navigation output is temporarily suppressed during detection of the transient inertial impulse.Independent Method Claim2.A method for controlling a digital interface, comprising:detecting rotational articulation of a digit about a longitudinal axis of the digit;establishing a skeletal reference frame corresponding to an orientation of the digit;mapping the detected rotational articulation to sequential navigation within a digital interface;detecting a transient impulse generated by the digit;generating a selection command in response to the transient impulse; andtemporarily suppressing navigation output during detection of the transient impulse.Dependent Claims — Structural Features3.The device of claim 1, wherein the chassis comprises a skeletal engagement structure configured to resist rotational displacement relative to the digit.4.The device of claim 1, wherein the chassis is configured to mechanically couple to a phalanx of the digit such that rotation of the phalanx produces corresponding rotation of the chassis.5.The device of claim 3, wherein the skeletal engagement structure comprises a saddle-shaped structure extending along a dorsal surface of the digit.6.The device of claim 3, wherein the skeletal engagement structure comprises a partially circumferential engagement structure configured to engage the digit while permitting flexion of adjacent finger joints.7.The device of claim 1, wherein the chassis includes a sensor housing positioned on a dorsal portion of the digit.Dependent Claims — Motion Sensing8.The device of claim 1, wherein the motion sensing module comprises an inertial measurement unit including at least one accelerometer and at least one gyroscope.9.The device of claim 1, wherein the motion sensing module is configured to detect angular velocity corresponding to rotational articulation of the digit.10.The device of claim 1, wherein the transient inertial impulse corresponds to a short-duration acceleration event exceeding a predefined threshold.Dependent Claims — Navigation Behaviour11.The device of claim 1, wherein the sequential navigation comprises incremental traversal through a sequence of digital interface elements including document pages, image slices, data records, or timeline positions.12.The device of claim 1, wherein a direction of rotational articulation determines forward or reverse navigation within the sequence.13.The device of claim 1, wherein the processing unit applies a non-linear transfer function between rotational articulation and navigation step size.Dependent Claims — Impulse Selection14.The device of claim 1, wherein the transient inertial impulse corresponds to a rapid tap, flick, or abrupt motion of the digit.15.The device of claim 1, wherein detection of the transient inertial impulse causes generation of a selection event within the digital interface.16.The device of claim 1, wherein navigation output is suppressed fora predefined temporal interval during detection of the transient inertial impulse.Dependent Claims — Stabilisation Detection17.The device of claim 1 further comprising a stabilisation detection module configured to detect a stabilised state based on reduced translational motion variance.18.The device of claim 17, wherein the stabilised state corresponds to contact between the digit and a support surface.19.The device of claim 17, wherein detection of the stabilised state activates a precision navigation mode with increased sensitivity to rotational articulation.Dependent Claims — Feedback and Output20.The device of claim 1 further comprising a feedback module configured to generate tactile feedback corresponding to navigation or selection events.21.The device of claim 20, wherein the feedback module comprises a haptic actuator.22.The device of claim 1, wherein the communication interface transmits navigation and selection commands to an external computing device.23.The device of claim 22, wherein the external computing device comprises at least one of:• a computer• a mobile device• an augmented reality device• a virtual reality system.Interaction Model24.The method of claim 2, wherein rotational articulation of the digit is detected using any sensing modality capable of determining rotation of the digit about the longitudinal axis, including inertial sensing, optical tracking, magnetic sensing, or camera-based motion tracking, such that sequential navigation and impulse-based selection may be implemented independently of the specific sensing technology used.25.The method of claim 2, wherein the sequential navigation and selection commands collectively provide a rotational navigation and impulse-based selection interface for controlling a digital system, and wherein the sequential navigation corresponds to traversal through a one-dimensional ordered dataset including image slices, document pages, menu items, timeline positions, or data records.A

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