Electric Power Steering Torque Differential Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electric power steering systems face challenges in maintaining the reliability of the compensation system when the detected steering torque value is held constant, leading to inappropriate compensation due to a zero torque differential value.
Innovation Solution
The system computes and holds the torque differential value before the detected steering torque value is held, allowing for continuous compensation even during periods of constant steering torque, and alternately outputs malfunction diagnosis signals to ensure motor drive control reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the detected steering torque value is held constant during a predetermined period, then the system can maintain stable control output, but the torque differential value becomes zero and the compensation system reliability deteriorates
Solution Approach 1:
The controller performs preliminary computation of the torque differential value before the detected steering torque value is held constant. By computing and storing the torque differential value in advance (during the period when torque values are still varying), the system ensures that valid differential data is available even when the torque value is subsequently held constant, preventing the compensation system from failing due to zero differential values.
2Speed
If the torque differential value is computed continuously, then the compensation can be updated in real-time, but during periods of constant torque the differential value becomes zero and loses compensatory effectiveness
Solution Approach 1:
The controller computes the torque differential value in advance during periods when the steering torque is changing, before entering a period where torque is held constant. This preliminary computation ensures that meaningful differential values are captured and stored for use during the constant torque period, maintaining compensation effectiveness without requiring continuous real-time computation during unchanging conditions.
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 prevents abnormal torque differential values and ensures reliable compensation by maintaining the torque differential value close to its actual value, enhancing the overall reliability of the electric power steering system.
Implementation Method 1
a magnetic field generator that periodically applies a magnetic field to the torque sensor
Implementation Method 2
The torque sensor includes a Hall IC and a magnetic circuit that applies magnetic flux corresponding to steering torque applied by a driver to the Hall IC
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided an electric power steering system that is able to ensure the reliability of a compensation system based on a torque differential value, even during a period in which a detected steering torque value is held at a constant value. The electric power steering system includes a torque sensor (6) that outputs a detection signal (Sτ) corresponding to a steering torque, and a controller (5). The controller (5) computes a detected steering torque value (τ) based on the detection signal (Sτ), and a torque differential value (dτ), which is a first-order time differential value of the detected steering torque value (τ). The controller (5) computes a current command value (I*) by providing compensation to a basic current command value (I1*) based on the detected steering torque value (τ) with the use of a compensation value (I2*) based on the torque differential value (dτ). When the detected steering torque value (τ) is held for a predetermined period, the controller (5) holds the torque differential value (dτ) at a value computed before the detected steering torque value (τ) is held, during the period in which the detected steering torque value (τ) is held.