Piezoelectric Pump Frequency Control for Blood Pressure Measurement
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Solution Overview
Problem
Conventional piezoelectric blood pressure measurement devices face challenges in precision due to noise interference and pulsation influences, particularly when using voltage control for inflation speed, which increases circuit complexity and costs.
Innovation Solution
A control method for piezoelectric pumps that modulates voltage in predetermined steps, applying voltages above and below the target amplitude in alternating ratios to maintain consistent output, reducing noise and pulsation effects while achieving precise inflation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage control precision is increased to control inflation speed properly, then blood pressure measurement precision is improved, but the number of components and circuitry costs increase
Solution Approach 1:
The patent replaces complex voltage control circuitry with a simpler frequency control approach. Instead of using high-precision voltage control circuits to regulate inflation speed, the invention controls the piezoelectric pump by adjusting the driving frequency of the piezoelectric element, which simplifies the control circuit while maintaining measurement precision.
Solution Approach 2:
The patent changes the control parameter from voltage amplitude to driving frequency. By controlling the frequency of the piezoelectric element rather than the voltage magnitude, the system achieves precise inflation speed control with simpler circuitry, avoiding the need for high-precision voltage control components.
2Manufacturing precision
If AM modulation is added to voltage control to increase resolution, then pump output precision is improved, but the system becomes affected by pulsations, ambient sounds, and noise
Solution Approach 1:
The patent substitutes AM modulation of voltage with frequency control of the piezoelectric element. By controlling the driving frequency directly rather than modulating voltage amplitude, the system achieves precise pump output control without introducing the pulsations and noise associated with AM modulation.
3Ease of operation
If conventional PWM control is used for piezoelectric pump, then control simplicity is maintained, but inflation speed precision is insufficient for accurate blood pressure measurement
Solution Approach 1:
The patent replaces PWM control with direct frequency control of the piezoelectric element. This substitution maintains control simplicity while dramatically improving inflation speed precision, as the piezoelectric pump responds more precisely to frequency changes than to PWM duty cycle adjustments.
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
This approach enhances the precision of blood pressure measurement by suppressing noise and reducing pulsation influence, allowing for high-precision inflation control comparable to amplitude modulation methods without the associated noise and complexity.
Implementation Method 1
a piezoelectric pump configured to increase the pressure within the cuff
Data Source
AI summary
A control amplitude and a control frequency of a voltage applied to a piezoelectric pump are determined, control is carried out so that a voltage at the determined control amplitude and control frequency is applied to the piezoelectric pump, and a blood pressure value is calculated based on a cuff pressure detected by a pressure detection unit during inflation when the cuff pressure is increased by the piezoelectric pump. The amplitude of the voltage is controlled in predetermined steps, and a voltage having an amplitude that is a value above the control amplitude by at least one step and a voltage having an amplitude that is a value below the control amplitude by at least one step are applied, in a predetermined order, so that the control is essentially the same as when a voltage at the determined control amplitude is applied.