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A Biomimetic Gaze Control to Restore Head-Neck Movements

A Biomimetic Gaze Control to Restore Head-Neck Movements

Colin Rubow, Haohan Zhang · N/A · 2026

vision control
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Summary

Powered neck exoskeletons are developed to restore head-neck motions for those with neck muscle weakness. Current methods using hand-held input devices to control these robotic systems are unintuitive or non-viable for these populations.

Abstract Summary

Powered neck exoskeletons are developed to restore head-neck motions for those with neck muscle weakness. Current methods using hand-held input devices to control these robotic systems are unintuitive or non-viable for these populations. Alternatively, the eyes coordinate with the head to accomplish many daily tasks. Therefore, movements of the eyes can be a useful signal to control the neck exoskeletons without needing to use the hands. However, previous control models lack biobehavioral basis as well as means to personalize the control behavior, causing unnatural head-neck movements. This paper presents a novel eye-tracking controller design leveraging the vestibulo-ocular reflex to emulate natural eyehead coordination. Personalization tools were also designed, consisting of sliders to allow users to adjust the parameters of this controller. Here, we present the technical design and validation of this system in human users. Compared to the previous eye-tracking model, the new controller provides natural head motions personalized to the user through more natural velocity profiles and a 24 percent average increase of accurate motion intent detection. This system provides a powerful platform for studying eye-tracking controllers in the context of personalization and preference, and ultimately restoring the lost head-neck mobility in patient populations.

Key Points

  • Powered neck exoskeletons are developed to restore head-neck motions for those with neck muscle weakness.
  • Current methods using hand-held input devices to control these robotic systems are unintuitive or non-viable for these populations.
  • Alternatively, the eyes coordinate with the head to accomplish many daily tasks
  • Therefore, movements of the eyes can be a useful signal to control the neck exoskeletons without needing to use the hands.
  • However, previous control models lack biobehavioral basis as well as means to personalize the control behavior, causing unnatural head-neck movements.

Design of a Novel Gaze Control Model

In the literature, gaze is defined as the head angle plus the eye angle relative to the head, or, the direction of sight [ 19 ] . When a gaze shift is performed, the eyes quickly shift towards the target (saccade). The VOR then enables the counter rotations of the eyes and head so that the gaze remains fixed on the target while the eyes become centered in the head [ 20 , 21 ] .

Design of a Novel Gaze Control Model — A Biomimetic Gaze Control to Restore Head-Neck Movements
Fig. 1: Deadzone and gaze diagram with plot of rotational speed related to gaze shift distance. $\Delta\theta_{\text{des}}$ is the desired angle of the rotation of the head. $\dot{\theta}_{h}$ is the velocity of the head which is broken into its pitch and yaw rotational components. $d_{x}$ and $d_{y}$ are the lengths of the deadzone elliptical axis where the deadzone is centered in the world camera view. While the gaze is inside the deadzone, the head velocity is 0, but once outside the deadzone, the velocity increases linearly at the rate of $v_{p}$, the velocity proportion, in the direction of the gaze.

Robotic Integration

We then implemented the vector gaze control model with a powered neck exoskeleton to evaluate the model performance in the context of a human-robot system. In this section, we describe the hardware and software implementation of this controller, as well as tools for tuning controller parameters for potential personalization. The robotic system contains four main components (Fig.

3 ): an exoskeleton hardware, a head-mounted eye-tracker, mechanical sliders for manual parameter tuning, and computer programs associated with control software.

Robotic Integration — A Biomimetic Gaze Control to Restore Head-Neck Movements
Fig. 2: Trajectory comparison results between the vector and region-based controllers in 100 computer simulated gaze shifts. (left) A typical gaze shift performance. The vector controller moves straight towards the target, while the region-based controller moves first to the right, then zigzags towards the target (enlarged in the zoomed view). Both controllers stop when the gaze target hits their respective deadzones, the dashed lines of the same color. The 100 gaze targets are distributed from directly rightward to upwards with a slope of 45 ∘ . (right) Box plot of the difference of path lengths between both controllers. Higher values correspond to a higher path length performed by the region-based controller as compared to the vector controller. The median value is $13.7^{\circ}$.

Experiments with Human Users

To test our deadzone hypothesis and justify the vector gaze control model, as well as evaluate the performance of the controller in a human-robot context, we performed a human experiment. Eight healthy participants without known history of head-neck injuries were enrolled in this study (4 male, 4 female , 23-29 yrs). Four participants wear glasses and were given the option to not wear them during the experiment.

Three opted for that option and were able to perform the given tasks.

Experiments with Human Users — A Biomimetic Gaze Control to Restore Head-Neck Movements
Fig. 3: The robotic system. The arrows denote the directional interaction subsystems have with each other. The android phone runs a program that allows gaze data streaming.

Results

The natural velocity proportion and deadzone characteristics are summarized by participant in Table II . Reported is the slope and r-value of the regression results for calculating the velocity proportion ($p [ 23 , 19 , 22 ] , while the deadzone columns provide new results in eye-head coordination. A wide variety of best-fit ellipse dimensions were observed.

As an example, the best-fit ellipse and velocity proportion regression results are shown for participant 4 in Fig. 7 .

Results — A Biomimetic Gaze Control to Restore Head-Neck Movements
Fig. 4: The powered neck exoskeleton with eye-tracking integration. An inertial measurement unit (IMU) was included for the study as an independent measurement of head motions, but it was not used in the robot control. The headband can be easily detached from the rest of the robot by removing a set of fasteners.

Sources and Demonstrations

Figures are reproduced from Rubow et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.

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