Steering Assist Voltage Control for Stationary Torque
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Solution Overview
Problem
There is a contradiction between achieving a desired steering assist force with a small electric motor in electric power steering systems and minimizing alternator voltage to improve fuel economy and reduce CO2 emissions, as the former requires higher battery voltage while the latter aims for lower voltage levels.
Innovation Solution
A steering assist apparatus with a voltage control unit that detects vehicle speed and steering state to increase alternator output voltage when a great steering torque is expected, ensuring adequate assist force without constant high voltage, which maintains fuel economy by keeping alternator voltage at a minimum required level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the alternator output voltage is kept high to ensure adequate steering assist force from a small electric motor, then the steering assist performance is improved, but the fuel economy deteriorates and CO2 emissions increase due to increased alternator load
Solution Approach 1:
The alternator output voltage is dynamically adjusted based on real-time detection of steering torque and vehicle speed. The voltage control unit increases voltage only when stationary steering is detected (high steering torque at low vehicle speed), and maintains low voltage during normal driving, resolving the contradiction between ensuring assist force when needed and minimizing energy consumption during normal operation
Solution Approach 2:
The system changes the electrical parameter (alternator output voltage) based on detected operating conditions. By monitoring steering torque and vehicle speed, the system switches between high voltage mode (for stationary steering) and low voltage mode (for normal driving), optimizing both steering performance and fuel economy
2Use of energy by moving object
If the alternator output voltage is lowered to minimize alternator load and improve fuel economy, then CO2 emissions are reduced, but the steering assist force becomes insufficient especially during stationary steering
Solution Approach 1:
The system performs preliminary detection of steering torque and vehicle speed before the actual steering action occurs. When stationary steering conditions are detected (high torque at low speed), the voltage is increased in advance to ensure adequate assist force is available when the driver turns the steering wheel, preventing power insufficiency
Solution Approach 2:
The alternator operates in periodic cycles of high voltage and low voltage modes based on detected steering conditions. During stationary steering periods, high voltage is supplied; during normal driving periods, low voltage is maintained, creating a periodic operation pattern that balances power availability with energy efficiency
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
The solution effectively prevents insufficient steering assist force at the start of steering while maintaining low alternator voltage, improving fuel economy and reducing CO2 emissions by dynamically adjusting the alternator output voltage based on vehicle speed and steering state.
Implementation Method 1
an alternator (2) for charging the vehicle-mounted battery (3)
Implementation Method 2
an electric motor (11) for assisting the steering force of the steering wheel (5)
Data Source
Figure 1
Figure 2(a)~2(e)
AI summary
When the vehicle speed of a vehicle falls to a predetermined vehicle speed or lower and a steering wheel 5 is steered with a predetermined steering torque or more, it is deemed highly likely for the steering wheel 5 to be steered while the vehicle is stopping, namely, to fall into a state of so-called stationary steering. In this case, control for increasing the output voltage of an alternator 2 is authorized.