Sensorless Fluid Pump Control via Current Waveform Adaptation
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Solution Overview
Problem
Modern fluid pumps for motor vehicles, particularly those using electronically commutated motors, face limitations in speed range due to the reliance on counter-EMF for rotor position detection, which restricts operation below a certain minimum speed, and experience pressure imbalances leading to increased torque and current requirements.
Innovation Solution
A control device and method that adjust motor current intensity and waveform, and apply voltage based on sensed speed, allowing for comparison with a speed threshold to manage pump operation effectively across varying speeds, including below the minimum speed limit, by using power electronics for monitoring and controlling the fluid pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If back EMF detection method is used for rotor position detection, then the control system can operate without position sensors, but the minimum operating speed is limited and cannot operate below a certain speed threshold
Solution Approach 1:
The patent changes the control parameter from voltage-based control to current-based control. By directly controlling the motor current with adapted current intensity and waveform, the system can operate the pump below the minimum speed threshold where back EMF detection is no longer valid, while maintaining sensorless operation.
Solution Approach 2:
The patent implements dynamic switching between two control modes: above the speed threshold, voltage control is used; below the threshold, current control is used. This dynamic adaptation allows the system to maintain optimal performance across the entire speed range without requiring additional position sensors.
2Stability of the object's composition
If positive displacement pump design is used, then hydraulic-mechanical stiffness is increased, but pressure increase causes significant torque and current requirements
Solution Approach 1:
The patent applies partial action by using internal consumers (jet pumps) to handle the minimum fuel consumption requirement, allowing the main electric pump to operate only when additional fuel is needed. This reduces the overall operating time and power consumption of the high-stiffness positive displacement pump.
Solution Approach 2:
The control device periodically monitors the fuel system pressure and fuel consumption requirements, switching the pump on and off or adjusting its speed accordingly. This periodic control allows the system to maintain hydraulic stability while minimizing the torque and current requirements over time.
3Stability of the object's composition
If pump current is increased to maintain pressure, then pressure stability is improved, but energy consumption and heating increase
Solution Approach 1:
The control device continuously monitors the actual pump current and compares it with reference values. Based on this feedback, it adjusts the motor current with adapted waveform and intensity to maintain pressure stability while minimizing energy consumption and heating effects.
Solution Approach 2:
The patent changes the control parameter from voltage to current, allowing direct control of the motor current with adapted waveform. This enables more precise control of the pump's power consumption and heating while maintaining the required pressure stability.
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
Enables efficient operation and reduced heating at low speeds, allowing for stable fluid pump performance and pressure management across the entire speed range, while minimizing energy consumption and maintaining hydraulic stability.
Implementation Method 1
These EC-type drive motors operate on the principle of a permanent magnet synchronous machine and can be operated over a specific speed range
Implementation Method 2
injecting currents of suitable amplitude and waveforms. The control field frequency is maintained at a preset value. By injecting a current of the appropriate amplitude, the pump rotor can be forced to rotate
Implementation Method 3
the electronics required for operation are able to detect the back EMF (electromotive force), or in other words, the induced voltage, of the free-running phase and use it as a position signal for the rotor
Data Source
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AI summary
Apparatus (1) for controlling a fluid pump for a motor vehicle, said apparatus comprising: a first control device (10) designed to control an electric prime mover (110) of a fluid pump (100) by impressing at least one motor current having an adapted current intensity and an adapted waveform; and a second control device (20) designed to detect a speed of the electric prime mover (110) and apply an adapted voltage to the electric prime mover (110) on the basis of the detected speed.