Neurostimulator Supervisor Circuit for Closed-Loop Overstimulation Control
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Solution Overview
Problem
Implantable neuro-stimulation devices face challenges in maintaining stable closed-loop control due to potential software malfunctions, changes in patient posture affecting loop gain, and risk of overstimulation.
Innovation Solution
An implantable neuro-stimulation device with a supervisor module connected to the feedback signal, capable of detecting malfunctions and adjusting the stimulation energy control accordingly, thereby preventing overstimulation and maintaining stable closed-loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop control is implemented to adjust stimulation output, then stimulation precision is improved, but system reliability deteriorates due to software glitches and coding errors
Solution Approach 1:
The patent introduces a supervisor circuit as an intermediary hardware component that monitors the closed-loop control system. This supervisor independently verifies feedback signals and control decisions, acting as a mediator between the software controller and the stimulation output, thereby preventing software-induced errors from causing harmful overstimulation
Solution Approach 2:
The supervisor circuit performs self-monitoring of the control system's health and integrity. It continuously checks for malfunctions, signal clipping, and abnormal conditions, and autonomously takes corrective action by adjusting or disabling stimulation output when issues are detected, enabling the system to self-correct without external intervention
2Reliability
If feedback signal monitoring is increased to detect malfunctions, then system safety is improved, but device complexity increases
Solution Approach 1:
The patent divides the control system into distinct functional segments: the primary closed-loop controller, the supervisor circuit, and the stimulation output stage. The supervisor is a separate, dedicated monitoring module that focuses solely on safety verification, allowing complex monitoring functions to be isolated from the main control logic and implemented with simpler, more reliable hardware
3Adaptability or versatility
If loop gain is adjusted to accommodate posture changes, then adaptability is improved, but control stability deteriorates due to oscillation
Solution Approach 1:
The supervisor circuit applies preliminary anti-action by preemptively detecting conditions that could lead to instability or oscillation. It monitors for signs of malfunction and abnormal loop gain behavior before they cause harmful effects, and takes corrective action in advance to prevent oscillation, rather than reacting after instability has already occurred
Data Source
AI summary
This disclosure relates to implantable neuro stimulation devices with a feedback loop to control an amount of energy delivered into a neural tissue based on a measured evoked neural response. Stimulation electrodes deliver stimulation energy to neural tissue. A microprocessor performs closed-loop control of the stimulation energy based on a feedback signal that is indicative of an evoked neural response. A supervisor is connected to the feedback signal and detects malfunction of the stimulator based on the feedback signal. The supervisor is also connected to the stimulator to provide a status signal to the stimulator and changes the status signal to indicate malfunction upon detecting malfunction based on the feedback signal. The microprocessor adjusts the control of the stimulation energy in response to the status signal from the supervisor indicating malfunction.