Steering Control Apparatus Low Induced Voltage Response
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Solution Overview
Problem
In electric power steering systems, rotation angle sensor-less control faces challenges in securing calculation accuracy and response to driver steering due to noise influence, especially when induced voltage is low, affecting steering assistance.
Innovation Solution
A steering control apparatus that calculates a current command value based on steering torque and estimates an electrical angle using induced voltage, with a selection circuit choosing between two addition angles based on threshold voltage, and integrates them to improve response, incorporating phase compensation and use ratios from steering condition maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rotation angle sensor-less control is executed using induced voltage to calculate estimated electrical angle, then the system can operate without rotation angle sensor, but calculation accuracy deteriorates when induced voltage is low due to noise influence
Solution Approach 1:
The patent dynamically switches between two different addition angle calculation methods based on the magnitude of induced voltage. When induced voltage is high, it uses the induced voltage-based calculation; when induced voltage is low, it switches to the steering torque-based calculation. This dynamic adaptation resolves the contradiction by maintaining measurement precision across varying operating conditions while preserving the ability to operate without a rotation angle sensor.
Solution Approach 2:
The patent changes the calculation parameter (addition angle) based on the induced voltage level. By monitoring the induced voltage magnitude and switching between different calculation approaches (induced voltage-based vs. steering torque-based), the system maintains accurate electrical angle estimation across different operating conditions, thereby resolving the accuracy issue at low induced voltage while keeping the sensor-less operation capability.
2Productivity
If induced voltage-based addition angle calculation is used, then the calculation can be performed, but response of steering assistance to driver's steering deteriorates due to phase lag
Solution Approach 1:
The patent applies phase compensation to the steering torque-based addition angle by using the derivative of steering torque. This preliminary action anticipates the future state of the steering input, effectively advancing the phase of the calculated electrical angle. By doing so, the system compensates for the inherent phase lag in induced voltage-based calculations and improves the response speed of steering assistance while maintaining calculation capability.
3Device complexity
If single addition angle calculation method is used, then the calculation process is simple, but calculation accuracy deteriorates at low induced voltage due to noise
Solution Approach 1:
The patent implements a dynamic selection mechanism that chooses between two addition angle calculation methods based on induced voltage magnitude. This dynamic approach maintains relative simplicity by using clear switching criteria (induced voltage threshold) while significantly improving accuracy at low induced voltage conditions. The system remains computationally efficient by selecting the most appropriate calculation method for current operating conditions rather than using a single complex method.
Solution Approach 2:
The patent introduces an intermediary switching mechanism that selects between two calculation methods based on induced voltage level. This intermediary (the selection logic) mediates between the simplicity of a single calculation method and the accuracy requirements at different operating conditions. By using the induced voltage magnitude as the switching criterion, the system maintains computational simplicity while achieving high accuracy across all 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
Enhances the response of steering assistance by accurately calculating the estimated electrical angle, even at low induced voltage, reducing noise influence and ensuring continuous motor control during sensor abnormalities.
Implementation Method 1
an estimated electrical angle that is estimated based on an induced voltage (counter-electromotive voltage) generated in the motor
Data Source
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AI summary
Provided is a steering control apparatus in which the response of steering assistance to driver's steering can be improved during execution of rotation angle sensor-less control. When the rotation angle sensor-less control is executed and when an induced voltage value (E) is equal to or lower than a threshold voltage, driving of a motor is controlled based on a second addition angle (Δθm2). The second addition angle (Δθm2) is calculated such that values obtained by multiplying a first pre-addition angle (β1) calculated based on a steering torque (Trq) and a second pre-addition angle (β2) calculated based on an induced voltage derivative (dE) by respective predetermined use ratios that are based on the induced voltage value (E) are added together. By using the second addition angle, a more appropriate estimated electrical angle is calculated in response to a driver's steering situation.