Magneto-rheological Power Steering Coupling Control
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Solution Overview
Problem
Existing power steering systems, both hydraulic and electro-hydraulic, face inefficiencies in controlling pump speed independently of engine speed, particularly under varying steering conditions, which affects steering assistance and fuel efficiency.
Innovation Solution
A method and control system utilizing a magneto-rheological power steering coupling with an electronic controller and power driver to compute a duty cycle value based on sensor inputs, adjusting the magneto-rheological fluid coupling's magnetic field to vary the pump speed through a non-linear proportional-integral-derivative equation, ensuring optimal torque transfer and pump speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power steering pump is driven directly by the engine using a belt, then the pump operates continuously as long as the engine is running, but this results in continuous circulation of hydraulic fluid through the steering gear and cannot adapt to varying steering conditions
Solution Approach 1:
The patent applies a magneto-rheological clutch (MRC) between the engine-driven belt and the power steering pump to enable dynamic speed control. The MRC allows the pump speed to be continuously adjusted based on actual steering demands, transitioning from fixed engine-speed coupling to variable-speed operation that adapts to steering conditions while maintaining engine-driven operation.
Solution Approach 2:
The patent changes the operational parameter of pump speed by using a magnetic field to control the viscosity of magneto-rheological fluid in the clutch. By varying the magnetic field intensity, the clutch adjusts the torque transmission ratio, thereby controlling pump speed independently of engine speed to match steering requirements.
2Reliability
If the power steering pump must provide the required flow and pressure for the worst case engine speed, then the system can handle all operating conditions, but this results in energy waste during light steering conditions
Solution Approach 1:
The dynamic speed control capability provided by the MRC enables the pump to operate at optimal speeds matching actual steering demands rather than maintaining constant high-speed operation. This dynamic adaptation reduces energy consumption during light steering while preserving the ability to deliver maximum flow and pressure when needed.
Solution Approach 2:
By changing the pump speed parameter through magnetic field control of the MRC, the system adjusts hydraulic fluid circulation to match actual steering requirements. This prevents energy waste during light steering conditions while maintaining sufficient flow and pressure capacity for worst-case scenarios when required.
3Adaptability or versatility
If an electro-hydraulic power steering system uses an electric motor to drive the pump, then the pump speed can be controlled independently of engine speed, but this increases system complexity and cost
Solution Approach 1:
The patent replaces the electric motor-driven system with an engine-driven system that uses a magneto-rheological clutch for speed control. This substitution eliminates the need for electric motors, inverters, and associated electronic control systems while achieving independent pump speed control through magnetic field control of the clutch mechanism.
Solution Approach 2:
The patent achieves independent speed control by changing the physical state of magneto-rheological fluid through magnetic field application. This parameter change approach allows continuous speed adjustment without requiring complex electronic drive systems, maintaining mechanical simplicity while enabling adaptive control.
4Adaptability or versatility
If a conventional electronic control unit controls the intensity of the magnetic field, then the speed of the power steering pump may be varied independent of engine speed, but this requires complex control algorithms and processing
Solution Approach 1:
The patent implements feedback control by continuously monitoring steering wheel angle and steering torque, then using this information to adjust the magnetic field intensity in the MRC. This closed-loop feedback enables automatic speed adaptation to steering conditions without requiring complex predictive algorithms or multiple sensors.
Solution Approach 2:
The control system adjusts the magnetic field parameter directly based on steering conditions, providing simple and effective speed control. By changing the magnetic field intensity in response to steering torque and angle feedback, the system achieves smooth speed variation without complex control mathematics or multiple control stages.
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 solution allows for precise control of the power steering pump speed, enhancing steering assistance and fuel efficiency by adapting to different steering conditions, reducing energy consumption, and preventing overheating of the pump.
Implementation Method 1
The viscosity of the magneto-rheological fluid, or MRF, contained within the MRC can be controlled by exposing the MRF to a magnetic field. As the viscosity of the MRF is increased, the torque transfer through the fluid is increased.
Data Source
AI summary
A method of controlling a magneto-rheological power steering coupling is provided. The method is to be employed by a controller and is initiated upon engine start-up. The method includes initializing calibration parameters and reading a plurality of input values. Subsequently, a hand wheel angle rate value is calculated from one of said plurality of input values. A pump speed command value is calculated as a function of at least the hand wheel angle rate value. A pump speed error value is then calculated, and a proportional-integral-derivative calculation is performed acting on the pump speed error value to determine a pulse width modulation duty cycle value. The duty cycle value is then output to a power driver to provide a control signal to the magneto-rheological power steering coupling. Also provided is control system and apparatus operable to perform the functions described hereinabove.