Range Switching Device Open-Loop Control for Position Accuracy

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Solution Overview

Problem

In motor-driven range switching devices, the motor may fail to rotate to the target position due to a narrow attractive force range of the detent mechanism, leading to potential overshoot when the stop range is narrowed to accommodate this, compromising rotation position accuracy.

Innovation Solution

Implementing an open-loop control mechanism that continues to sequentially switch the power supply phases of the motor after feedback control ends, allowing the motor to rotate to the target position in small steps until it reaches the desired position, thereby avoiding the need to narrow the stop range and preventing overshoot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the stop range of the motor is narrowed to match the attractive force range of the detent mechanism, then the motor can reliably reach the target rotation position, but the motor becomes susceptible to overshoot past the target position

Engineering Contradiction:

Improverotation position accuracyVSAvoidstable positioning at target

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent divides the control process into two distinct phases: feedback control phase (while motor is moving) and open-loop control phase (near target position). This segmentation allows different control strategies to be applied at different stages, resolving the contradiction between positioning accuracy and stable positioning.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent dynamically switches between feedback control and open-loop control based on the motor's proximity to the target position. The control mode changes from closed-loop to open-loop as the motor approaches the target, allowing the system to adapt to the changing requirements of the detent mechanism's attractive force range.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the stop range is kept wide to prevent overshoot, then the motor positioning is stable, but the motor may fail to rotate into the narrow attractive force range of the detent mechanism

Engineering Contradiction:

Improvestable positioning at targetVSAvoidrotation position accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by using open-loop control to nudge the motor into the attractive force range of the detent mechanism before relying on the detent's natural latching action. This preliminary positioning ensures the motor is within the narrow attractive force range while maintaining a wider stop range for stability.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If feedback control ends immediately when the motor enters the stop range, then the power supply stops promptly, but the motor may not reach the target position if the attractive force range is too narrow

Engineering Contradiction:

Improveswitching speedVSAvoidrotation position accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent maintains continuity of useful action by extending the control action beyond the standard feedback control termination point. The open-loop control continues to operate after feedback control ends, ensuring the motor completes its rotation to the target position even when the attractive force range is narrow, while still maintaining efficient switching speed.

Inventive Principle:

Principle #20Continuity of useful action

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 approach ensures accurate rotation to the target position even with a narrow attractive force range, enhancing position accuracy during shift range switching without risking overshoot.

Implementation Method 1

an encoder sensing a rotation of the motor and outputting a pulse signal in synchronization with the rotation of the motor

Methodology Applied

Scientific EffectEncoder sensing:

Implementation Method 2

a latch within the detent mechanism that is biased to slide downwardly into and engage a bottom of a range detention concave part

Methodology Applied

Scientific EffectSpring force: Spring

Data Source

PatentUS9304506B2Range switching device

Publication Date: 2016.04.05 DENSO CORP

AI summary

A range switching device provides a feedback control for rotating a motor toward a target rotation position. When a target shift range is switched, the range switching device rotates the motor toward a target rotation position by sequentially switching power supply phases of the motor based on an encoder count value. When the motor rotates within a predetermined stop range, the feedback control ends and a power supply to the motor is stopped. However, if the motor has not rotated to the target rotation position after a predetermined time has elapsed from the stopping of the power supply to the motor, an open drive is performed, in which the power supply phase of the motor is sequentially switched by open-loop control and the motor is rotated in small and/or minute steps toward the target rotation position. In such manner, position accuracy of the shift range switching is improved.