Actuator Driver Feedback Control for Low-THD H-Bridge Output
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Solution Overview
Problem
Existing actuator drivers introduce significant total harmonic distortion (THD) in driving signals due to switching operations of the H-bridge amplifier, affecting driving accuracy and varying from 5% to 10% across the output range.
Innovation Solution
An actuator driver incorporating a feedback signal generator and loop filter to adjust the input control signal based on sensed voltage levels of the driving signals, using a digital adder, digital pulse width modulation (PWM) generator, and H-bridge amplifier to reduce THD by implementing a feedback control mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If H-bridge amplifier switching operations are used to drive the haptic actuator, then the actuator can be controlled with varying duty cycles, but total harmonic distortion increases by 5% to 10% across the output range
Solution Approach 1:
The patent implements a feedback mechanism where the actual driving signal is sensed and compared with the ideal driving signal. The difference (error signal) is processed through a loop filter and used to generate a compensation signal that corrects the control signal. This closed-loop feedback system continuously reduces the THD by adjusting the driving signal based on real-time error detection, thereby maintaining high driving accuracy across the full duty cycle range.
Solution Approach 2:
The patent changes the parameter of the control signal by adding a compensation signal generated from the error signal. This parameter modification (adding corrective voltage components) adjusts the driving signal characteristics to reduce harmonic distortion while maintaining the desired duty cycle control versatility.
2Ease of operation
If H-bridge amplifier switching operations are used to enable polarities switching, then the actuator direction can be controlled, but harmonic noise components are introduced to the driving signals
Solution Approach 1:
The feedback mechanism senses the actual driving signal including harmonic noise components introduced by the H-bridge switching operations. The error signal processing and compensation signal generation specifically target and reduce these harmonic noise components while preserving the essential polarity switching functionality needed for actuator direction control.
Solution Approach 2:
The patent converts the harmful harmonic noise components into useful information by using them as part of the error signal. The feedback system detects these noise components and uses the error information to generate compensation signals that actively cancel the harmonic distortion, thereby transforming the harmful switching noise into an opportunity for precision correction.
3Manufacturing precision
If feedback control mechanism is implemented to reduce THD, then driving signal accuracy is improved, but device complexity increases due to additional components
Solution Approach 1:
The patent merges the feedback control functionality with the existing driving circuit by integrating the error signal processing and compensation signal generation within the existing control architecture. The loop filter and compensation mechanism are combined with the PWM generation and H-bridge control, creating a unified system that reduces THD without requiring entirely separate complex subsystems.
Data Source
AI summary
In an aspect, an actuator driver includes a first digital adder configured to output an adjusted control signal based on combining an input control signal and a filtered difference signal, a digital pulse width modulation (PWM) generator configured to convert the adjusted control signal to one or more PWM signals, and an H-bridge amplifier configured to output one or more driving signals based on the one or more PWM signals. The actuator driver further includes a feedback signal generator configured to generate a feedback signal based on the one or more driving signals, a second digital adder configured to output a difference signal based on subtracting the feedback signal from the adjusted control signal, and a loop filter configured to generate the filtered difference signal based on the difference signal.