Electric Motor Pump Control for Vehicle Braking Systems
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Solution Overview
Problem
Existing vehicle brake systems face challenges in precise control and comfort due to high starting currents and voltage fluctuations when delivering small hydraulic volumes, requiring complex consumer designs and often necessitating an angular position sensor.
Innovation Solution
A method using an electrically driven motor pump unit where the motor current is reduced after a specified time interval, with a rising motor voltage ramp, and motor voltage is reduced to 0 V when the motor current drops, allowing for precise metering of hydraulic volume without excessive loading of the vehicle electrical system, and eliminating the need for an angular position sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump motor is activated with full load for short periods to deliver small hydraulic volumes, then the hydraulic volume delivery is achieved, but high starting currents cause current and voltage fluctuations in the vehicle electrical system
Solution Approach 1:
The pump motor is activated in periodic pulse sequences rather than continuous operation. The control unit applies voltage ramps in repeated cycles, activating the pump only when needed to deliver small hydraulic volumes while allowing the electrical system to recover between pulses, thereby reducing cumulative current and voltage fluctuations
Solution Approach 2:
The voltage applied to the pump motor is changed dynamically using rising voltage ramps instead of immediate full voltage application. The control unit increases voltage gradually from 0 to maximum over a specified time interval, which limits inrush current while still achieving the required motor torque for hydraulic volume delivery
2Speed
If full motor voltage is applied immediately to start the pump motor, then the pump starts quickly, but excessive starting currents load the vehicle electrical system heavily
Solution Approach 1:
The voltage parameter is changed progressively rather than applied at full level immediately. The control unit implements a rising voltage ramp that increases voltage from 0 to maximum over a specified time interval, which reduces starting current while still achieving acceptable motor acceleration speed
Solution Approach 2:
The voltage ramp preparation is performed in advance before full power application. The control unit pre-charges the motor circuit by gradually increasing voltage during the ramp period, preparing the motor for operation while limiting the sudden current surge that would occur with immediate full voltage application
3Measurement precision
If an angular position sensor is used to determine the current angular position of the motor, then precise control is achieved, but the device complexity increases
Solution Approach 1:
The motor pump assembly itself provides the measurement information needed for control without requiring external sensors. The control unit detects motor current characteristics and uses them to infer angular position and delivery status, allowing the system to self-determine its state through existing electrical parameters rather than additional sensing hardware
Solution Approach 2:
The mechanical/angular sensing system is replaced with an electrical measurement system. Instead of using physical sensors to detect motor position, the control unit uses electrical current measurements and analysis to determine angular position and pump delivery status, substituting a mechanical sensing approach with an electrical field-based approach
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 reduces current and voltage fluctuations, simplifies the vehicle electrical infrastructure, and enables precise control of hydraulic volume delivery, enhancing comfort and safety by avoiding complex consumer designs and angular position sensing requirements.
Implementation Method 1
an electric motor (20) of the motor pump unit (10, 10') driving a mechanical pump (12, 12')
Implementation Method 2
a motor voltage (24) being subjected to a rising motor voltage ramp (11), with a motor current (22) being recorded, wherein delivery operation of the motor pump assembly (10, 10') begins as soon as a motor torque generated by the motor current (22) exceeds a sum of drag torque, breakaway torque and friction torque of the motor pump assembly (10, 10')
Data Source
Figure 1a~1b
Figure 2
AI summary
The invention relates to a method for conveying a metered hydraulic volume in a vehicle braking system by means of an electrically driven motor pump assembly, wherein a mechanical pump of the motor pump assembly is driven by means of an electric motor of the motor pump assembly. A rising motor voltage ramp is applied to the electric motor, a motor current (12) being detected, and a conveying mode of the motor pump assembly starting as soon as a motor torque generated by the motor current (12) exceeds a total of drag torque, breakaway torque and friction torque of the motor pump assembly. The motor current (12) reduces when the conveying mode starts. The method is characterized in that, when a reduction in the motor current (12) is detected after a specified time interval has elapsed, a motor voltage (11) is reduced to a value which ends the conveying mode. The invention further relates to a vehicle braking system.