Shift Range Control Using Three-Phase Encoder Fault Tolerance
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Solution Overview
Problem
In a motor control system, temporary chipping or noise in the signals from a two-phase encoder system can lead to loss of synchronization between the encoder count value and the rotational position of the rotor, causing the motor to stop, especially when a fault occurs in the rotation angle sensor.
Innovation Solution
A shift range control apparatus that uses a three-phase encoder system to acquire rotation angle signals, allowing the drive control unit to change the energization pattern when a fault is detected, ensuring continuous motor operation by utilizing inertia and maintaining synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-phase encoder system is used for motor control, then the device complexity is reduced, but the reliability deteriorates due to signal chipping or noise causing loss of synchronization
Solution Approach 1:
The encoder system is segmented into three independent phases (A-phase, B-phase, C-phase) instead of using a two-phase system. This segmentation allows the system to tolerate faults in individual phases while maintaining overall functionality through the remaining phases, thereby improving reliability without significantly increasing complexity.
Solution Approach 2:
The patent applies local quality by making each phase of the encoder system have differentiated characteristics and functions. The three-phase configuration allows specific phases to be activated or deactivated based on local fault conditions, enabling the system to maintain operation by utilizing healthy phases while isolating faulty ones.
2Reliability
If open loop control is used when fault is detected, then the reliability is improved by avoiding feedback issues, but the productivity deteriorates due to loss of precise position control
Solution Approach 1:
The control system dynamically adapts its operation mode based on fault detection. When a rotation angle signal fault is detected, the system transitions from feedback control to open loop control, and further to inertia-based operation if necessary. This dynamic adaptation allows the system to maintain reliability while minimizing the impact on productivity by using the most appropriate control mode for the current fault condition.
Solution Approach 2:
The patent changes the control parameters from closed-loop feedback control to open-loop control with predetermined energization patterns. By changing the control mode parameter and using pre-stored energization patterns corresponding to different fault conditions, the system maintains reliable operation while preserving some level of productivity through optimized predetermined sequences.
3Reliability
If the motor stops when synchronization is lost, then the reliability is improved by preventing faulty operation, but the productivity deteriorates due to interruption of shift range switching
Solution Approach 1:
The system performs preliminary actions by storing multiple energization patterns in advance for different fault conditions. When a fault occurs, the control unit quickly switches to the appropriate predetermined energization pattern without requiring complex real-time calculations or synchronization, allowing the motor to continue operating and completing the shift range switching operation.
Solution Approach 2:
The patent converts the harmful effect of signal faults into a beneficial outcome by using the fault detection as a trigger to switch to predetermined energization patterns. These patterns are designed to maintain motor operation and complete the shift range switching despite the fault, thereby converting what would be a stopping condition into a condition for continued operation.
Data Source
AI summary
A shift range control apparatus controls switching of a shift range by controlling driving of a motor, and includes a signal acquisition unit and a drive control unit. The signal acquisition unit acquires rotation angle signals output from a rotation angle sensor. The rotation angle signals respectively represents three or more phases different from each other. The drive control unit controls the driving of the motor to cause a rotational position of the motor to reach a target rotational position corresponding to a target shift range. The drive control unit changes from an energization pattern in a normal state to an energization pattern and continues the driving of the motor, in response to detecting a fault of the rotation angle signal during the switching of the shift range.