Motor Control Apparatus Open Loop Transition Without Shaft Sensor
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Solution Overview
Problem
The elimination of the output shaft sensor in motor drive systems prevents the setting of a reference position for open loop control operations, rendering the system unable to execute open loop control.
Innovation Solution
A motor control apparatus that includes an encoder, an encoder counter, an exciting phase change counter, a feedback controlling unit, a failure monitoring unit, and a fail-safe unit, which allows for the correction of the open loop target count value based on an exciting phase deviation correction value to set the reference position for open loop control operations when feedback control fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the output shaft sensor is eliminated to reduce component quantity and cost, then the device complexity and cost are reduced, but the ability to set reference position for open loop control is lost
Solution Approach 1:
The patent extracts the reference position setting function from the output shaft sensor and implements it through software processing of encoder signals. The control unit determines reference positions by processing encoder pulse signals during specific operational phases, eliminating the need for the output shaft sensor while maintaining open loop control capability.
Solution Approach 2:
The patent replaces the mechanical sensor-based reference position detection system with an electronic/software-based system. The control unit uses software algorithms to process encoder signals and determine reference positions, substituting the mechanical output shaft sensor with an electronic control approach.
2Device complexity
If the output shaft sensor is eliminated, then component quantity and cost are reduced, but the reliability of open loop control operation becomes compromised
Solution Approach 1:
The patent performs preliminary action by setting reference positions during specific operational phases (such as during feedback control operation or initial positioning) before open loop control is needed. The control unit stores these reference positions and uses them when transitioning to open loop control, ensuring reliability without requiring the output shaft sensor.
Solution Approach 2:
The patent uses feedback from encoder signals during the reference position setting phase to ensure accurate determination of reference positions. The control unit processes encoder pulse signals and uses this feedback information to accurately establish reference positions that can be reliably used during subsequent open loop control operations.
3Measurement precision
If feedback control operation is used, then rotor positioning accuracy is maintained, but the system cannot operate when feedback control system fails
Solution Approach 1:
The patent implements a dynamic control system that can switch between feedback control and open loop control modes. The control unit determines whether to operate in feedback mode (using encoder feedback for high precision) or open loop mode (using pre-set reference positions and exciting phase change counting), allowing the system to adapt its operation based on operational conditions and failure states.
Solution Approach 2:
The patent changes the control parameter mode from feedback-based (encoder count value) to open-loop-based (exciting phase change count value) when feedback control fails. The control unit switches between using encoder feedback information and using purely open-loop exciting phase change counting, maintaining operability under different conditions.
Data Source
AI summary
When a failure of a feedback control operation of an electric motor is sensed, a control unit changes the feedback control operation to an open loop control operation. At the time of executing the open loop control operation, the control unit sequentially changes the exciting phase of the motor without executing feedback of information of the count value of the encoder counter and rotates a rotor of the motor until a count value of an exciting phase change counter reaches an open loop target count value, which corresponds to a target rotational position of the rotor. When the control unit changes the feedback control operation to the open loop control operation, the control unit sets the open loop target count value by correcting a feedback target count value based on an exciting phase deviation correction value for the count value of the encoder counter.