Steering Control Apparatus End Abutment Detection via Induced Voltage
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Solution Overview
Problem
The existing steering control apparatuses face challenges in accurately detecting the end abutment state of the steering mechanism, leading to potential excessive stress due to inaccurate detection of the control steering angle, especially during sensorless control or when the detected electrical angle deviates from the actual angle.
Innovation Solution
Incorporating an induced voltage value calculation circuit and an end abutment determination circuit that determines the end abutment state by analyzing the significant decrease in induced voltage within a predetermined time when the steering torque exceeds a certain threshold, allowing for compensation control to reduce the assist force and prevent excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless control is executed using estimated electrical angle calculated from induced voltage, then the system can operate during sensor failure, but the control steering angle cannot be detected accurately leading to excessive stress on steering mechanism
Solution Approach 1:
The patent introduces an intermediary detection method using induced voltage monitoring to detect end abutment state. Instead of relying solely on inaccurate estimated electrical angle during sensorless control, the system uses induced voltage as an intermediary parameter to indirectly detect when the rack end abuts against the rack housing, thereby preventing excessive stress without requiring accurate control steering angle detection.
Solution Approach 2:
The patent replaces the mechanical angle detection system (rotation angle sensor) with an electrical detection method (induced voltage calculation). By calculating induced voltage based on motor current and electrical angle, the system substitutes the failed mechanical sensing mechanism with an electrical field-based detection method that can infer end abutment state without directly measuring the mechanical angle.
2Productivity
If the detected electrical angle deviates from the actual electrical angle, then normal control can continue, but the control steering angle becomes inaccurate causing excessive stress on the steering mechanism
Solution Approach 1:
The patent implements feedback by continuously monitoring the induced voltage and comparing it against expected values. When the rack end abuts against the rack housing, the induced voltage changes characteristically, providing feedback signal that triggers compensation control. This feedback mechanism allows the system to detect angle detection errors and correct them by reducing assist force, maintaining continuous operation while preventing excessive stress.
Solution Approach 2:
The patent performs preliminary detection of end abutment state by monitoring induced voltage before excessive stress can occur. By detecting the abutment condition in advance through induced voltage changes, the system can proactively reduce assist force and prevent damage, rather than reacting after damage has occurred.
3Strength
If compensation control is executed to reduce assist force near rack end, then excessive stress is suppressed, but the system requires accurate detection of end abutment state which is difficult during sensorless control
Solution Approach 1:
The patent replaces difficult mechanical state detection (rack end position) with electrical parameter measurement (induced voltage). By calculating induced voltage from motor current and electrical angle, the system substitutes direct mechanical measurement with electrical field measurement, making end abutment detection feasible during sensorless control when mechanical angle sensors are unavailable or inaccurate.
Solution Approach 2:
The patent uses induced voltage as an intermediary parameter to detect end abutment state. Instead of directly measuring the mechanical position of the rack end, the system measures the electrical parameter (induced voltage) that changes when the rack end abuts against the housing, providing an indirect but reliable detection method that works during sensorless control.
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 configuration enables accurate detection of the end abutment state even when the control steering angle cannot be detected accurately, thereby suppressing excessive stress on the steering mechanism by reducing the assist force during end abutment conditions.
Implementation Method 1
an induced voltage value calculation circuit configured to calculate an induced voltage value generated in the motor
Data Source
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AI summary
Provided is a steering control apparatus in which an end abutment state can be detected when a control steering angle cannot be detected accurately. A current command value calculation circuit (70) includes an end abutment determination circuit (95) and a guard processing circuit (96). When a decrease amount of an induced voltage value (E) within a predetermined time is equal to or larger than a predetermined decrease amount in a state in which a steering torque (Trq) is equal to or larger than a predetermined torque, the end abutment determination circuit (95) determines that the end abutment state occurs. When a determination signal (Sd) indicating that the end abutment state does not occur is input, the guard processing circuit (96) outputs an elemental current command value (Ib*) directly as a q-axis current command value (Iq*). When a determination signal (Sd) indicating that the end abutment state occurs is input, the guard processing circuit (96) outputs, as the q-axis current command value (Iq*), a value obtained by limiting the elemental current command value (Ib*) so that its absolute value is equal to or lower than a predetermined limit current value.