Vehicle Visual Stimulus Control for Low-Fatigue SSVEP Recognition
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Solution Overview
Problem
Existing brain-computer interface (BCI) technologies face challenges in detecting brainwave signals accurately and distinguishing them from other signals, leading to difficulties in controlling vehicles like electric powered wheelchairs, particularly due to issues with visual fatigue and reduced recognition performance in using flickering visual stimuli or augmented reality devices.
Innovation Solution
A vehicle system that outputs a visual stimulus image with changing object sizes and patterns, utilizing a checkerboard pattern and projector display, to induce steady-state visual evoked potentials (SSVEP) with reduced visual fatigue, enhancing recognition performance and enabling efficient control through an electroencephalogram (EEG) device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a flickering visual stimulus is used to induce SSVEP, then the recognition speed is improved, but visual fatigue increases
Solution Approach 1:
The patent changes the stimulation method from temporal flickering to spatial expansion/contraction of the visual stimulus. This parameter change allows the stimulus to expand and contract in size while maintaining a lower temporal frequency, thereby inducing SSVEP without causing severe visual fatigue associated with high-frequency flickering.
Solution Approach 2:
The visual stimulus dynamically changes its spatial dimensions (expanding and contracting) rather than simply flickering on and off. This dynamic spatial transformation maintains user engagement and reduces visual fatigue while still achieving the desired SSVEP induction for accurate and fast recognition.
2Object-affected harmful factors
If a checkerboard stimulus with pattern reversal is used to reduce visual fatigue, then the stimulus frequency is reduced, but the SSVEP induction efficiency may be affected
Solution Approach 1:
The patent transforms the stimulation mechanism from pattern reversal (changing the checkerboard pattern orientation) to spatial expansion and contraction of the stimulus. This parameter change maintains the beneficial low-frequency characteristic that reduces visual fatigue while achieving effective SSVEP induction through size transformation.
3Measurement precision
If the visual stimulus image is displayed at a fixed position on the monitor, then the SSVEP recognition performance is improved, but user comfort decreases and visual fatigue increases
Solution Approach 1:
The visual stimulus dynamically expands and contracts in size while maintaining its position on the display. This dynamic spatial transformation allows the stimulus to remain centrally located for optimal SSVEP induction while the size variation reduces the strain of maintaining fixed gaze, thereby improving user comfort without sacrificing recognition performance.
4Adaptability or versatility
If AR devices are used to display the visual stimulus, then the system versatility is improved, but the SSVEP recognition performance decreases due to environmental limitations
Solution Approach 1:
The patent employs spatial expansion and contraction of the visual stimulus as the primary induction mechanism, which is more robust to environmental variations than temporal flickering. This approach maintains effective SSVEP induction across different display devices including AR devices, thereby preserving recognition performance while achieving system versatility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides high performance and fast recognition speed for controlling vehicles by minimizing visual fatigue and improving SSVEP recognition, allowing intuitive user control through gaze-based commands.
Implementation Method 1
A SSVEP (Steady-State Visual Evoked Potential) is a brainwave signal generated due to repetitive visual stimulus (frequency stimulus). When the user gazes at an object (e.g., a stimulus that is reversed/reverted/toggled at a certain period), a brainwave of the user may be synchronized with a frequency of the gazed object, so that a large SSVEP may be measured at the corresponding frequency.
Implementation Method 2
an image for the visual stimulus (hereinafter, a visual stimulus image) may be output via an LCD or LED monitor
Data Source
AI summary
A vehicle includes a drive for driving the vehicle, a display for outputting a visual stimulus image, and a controller that controls the drive and the display, the visual stimulus image contains a visual stimulus object having a repeating pattern, and the controller outputs, via the display, the visual stimulus image in which a size of the visual stimulus object changes over time.