Shift-by-Wire Control Apparatus Current Limiting Circuit
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Solution Overview
Problem
Conventional shift-by-wire systems face accuracy issues in learning a reference position due to variations in temperature and time-based changes in motor winding resistance, leading to torque variations and potential malfunctions.
Innovation Solution
A control apparatus with a current detection circuit, current limiting circuit, and anomaly detection controller is used to restrict electric currents within a predetermined range, ensuring accurate learning of the reference position and detecting anomalies in the current limiting circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage-based control is used for reference position learning, then the control system is simple, but the current value changes due to winding resistance variations causing torque variations and deteriorating learning accuracy
Solution Approach 1:
The patent changes the control parameter from voltage to current. By controlling the motor based on current values rather than voltage, the system compensates for winding resistance variations that occur with temperature and time. The control unit adjusts the current to a target value, ensuring consistent torque and accurate reference position learning regardless of resistance changes.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the actual current value and comparing it with the target current value. The control unit uses this feedback to adjust the motor drive, maintaining the current at the desired level despite external variations. This closed-loop control ensures stable torque and accurate position learning.
2Reliability
If physical circuits are used to detect or restrict electric currents, then current control is achieved, but the circuits may break down disabling accurate learning
Solution Approach 1:
The patent replaces physical current detection and restriction circuits with software-based control. The control unit performs current monitoring and regulation through computational algorithms rather than dedicated hardware circuits. This substitution reduces the number of physical components that could fail while maintaining current control capability.
Solution Approach 2:
The control unit serves multiple functions: it controls motor drive, monitors current values, restricts current when necessary, detects anomalies, and performs reference position learning. By consolidating these functions into a single microcontroller, the patent eliminates the need for separate dedicated circuits for each function, reducing overall system complexity and potential failure points.
3Measurement precision
If current limiting is performed to suppress current value variations, then learning accuracy improves, but anomaly detection capability is reduced without proper monitoring
Solution Approach 1:
The control unit continuously monitors the actual current value and compares it with the target current value during reference position learning. This feedback mechanism enables the system to detect anomalies by identifying deviations beyond expected variations, while simultaneously maintaining accurate current control for precise position learning.
Solution Approach 2:
The patent uses software-based anomaly detection within the control unit rather than separate hardware monitoring circuits. The control unit analyzes current patterns and detects anomalies through computational methods, maintaining reliability while integrating the detection function into the existing control architecture.
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 enhances the accuracy of reference position learning and prevents malfunctions by stabilizing current values and torque, regardless of temperature and time-based variations, while detecting anomalies in the current limiting circuit.
Implementation Method 1
a current detection circuit that detects a current value of electric currents flowing through the windings and the switching devices
Implementation Method 2
a current limiting circuit that restricts the electric currents flowing through the windings and the switching devices so that an average of the current value detected by the current detection circuit is within a predetermined value span
Implementation Method 3
The motor rotates on electric power from a power source to rotate and drive a driving target
Data Source
AI summary
A current limiting circuit restricts electric currents flowing through windings and MOSs such that an average of a current value of the electric currents detected by a current detection circuit is within a predetermined value span. An MPU functions as a reference position learning controller that performs a reference position learning control to restrict the electric currents that flow through the windings and the MOSs using the current limiting circuit while rotating a motor until a detent plate stops at a limit position of a working span, to thereby learn the reference position of the motor. An anomaly detection section of the MPU functions as an anomaly detection controller to detect an anomaly in the current limiting circuit based on the current value detected by the current detection circuit during the reference position learning control.