Variable PWM Dither Control for Fluid Actuator Positioning
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Solution Overview
Problem
Fluid actuators face positioning inaccuracies due to hysteresis effects, which are exacerbated by traditional dithering methods that increase noise, wear, and energy inefficiency, particularly when using pulse width modulation at lower frequencies.
Innovation Solution
A control system that dynamically adjusts the frequency and width of pulse width modulation based on the system's operational needs, increasing voltage and reducing frequency to enhance positioning accuracy while minimizing undesirable effects, and vice versa, to optimize dithering for reduced hysteresis and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional dithering with pulse width modulation is applied to reduce hysteresis effects, then positioning accuracy is improved, but noise, wear, and energy consumption increase
Solution Approach 1:
The patent implements dynamic adjustment of dithering parameters (frequency and amplitude) based on real-time operating conditions. The control system continuously monitors the fluid actuator's state and adapts the PWM duty cycle and frequency accordingly, transitioning from static to dynamic dithering to optimize performance while minimizing harmful effects.
Solution Approach 2:
The patent changes the parameters of the dithering signal (frequency, amplitude, duty cycle) to optimize the balance between reducing hysteresis and minimizing noise/wear. By adjusting these parameters dynamically, the system achieves effective dithering at lower intensities when possible, reducing the harmful side effects while maintaining positioning accuracy.
2Measurement precision
If pulse width modulation frequency is reduced to enhance dithering effect, then hysteresis reduction is improved, but energy efficiency deteriorates
Solution Approach 1:
The control system dynamically adjusts the PWM frequency based on the required dithering intensity. When high hysteresis compensation is needed, the system uses lower frequencies with higher energy input. When less compensation is needed, it transitions to higher frequencies with lower energy consumption, optimizing the energy-hysteresis reduction trade-off in real-time.
Solution Approach 2:
The patent applies partial dithering action by using variable duty cycles and frequencies rather than continuous full-strength dithering. This allows the system to apply just enough dithering to overcome hysteresis effects without excessive energy input, achieving energy efficiency while maintaining positioning accuracy.
3Measurement precision
If dithering amplitude is increased to overcome mechanical hysteresis, then positioning accuracy is improved, but output disturbance and wear increase
Solution Approach 1:
The patent dynamically changes the dithering amplitude parameter based on operating conditions. The control system monitors the fluid actuator's response and adjusts the PWM duty cycle to optimize dithering amplitude, using lower amplitudes when possible to reduce output disturbance and wear while maintaining sufficient positioning accuracy.
Solution Approach 2:
The system uses feedback from the fluid actuator's actual position and performance to adjust dithering parameters in real-time. This closed-loop control allows the system to apply minimal necessary dithering amplitude to overcome hysteresis, reducing output disturbance and wear while maintaining positioning accuracy through continuous adaptation.
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 effectively reduces hysteresis and friction, improving positioning accuracy and energy efficiency by modulating dither in real-time according to the system's requirements, balancing noise and wear considerations.
Implementation Method 1
A control applies pulse width modulation to the voltage or current supplied to the fluid actuator. The pulse width modulation frequency and/or the applied voltage is varied to enhance dithering.
Implementation Method 2
providing 'dither' by utilizing pulse width modulation (PWM) on a voltage or current supply or, by other means, to a motor or other drive for a fluid system, the performance of the system can be enhanced
Implementation Method 3
magnetic systems exhibit a hysteresis characteristic which can cause the actual positioning of the component dynamic response to be different from that which is desired. There is also mechanical hysteresis which can be present in actuator systems.
Data Source
Figure 1~2
AI summary
A fluid system has a fluid actuator that receives a fluid to cause movement of a component. A valve (34) selectively controls the flow of fluid to the fluid actuator. A motor (50) for the valve is provided with an electric voltage or current. A control (59) applies a pulse width modulation variation to the supplied voltage or current. The control is operable to vary the pulse width modulation of the voltage or the current based upon conditions of the system. A mechanical system and a method are also disclosed.