Shift-by-wire controller position detection after power cut

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Solution Overview

Problem

Conventional shift-by-wire systems using switched reluctance motors struggle to determine the rotational position of the motor when the initial position is not learned, particularly after a momentary power cut, leading to potential failure in switching the shift range.

Innovation Solution

A shift-by-wire controller that includes a position sensor, encoder, and control unit to detect the shift range and determine the motor's rotational position by acquiring switching edges, allowing the system to switch the shift range even if the motor is not initially positioned correctly, using a combination of hardware and software components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the initial position of the SR motor is learned at a specific shift range (P-range) when power is turned on, then the controller can drive the SR motor to switch shift ranges, but the system fails when the SR motor is not positioned at the P-range due to momentary power cut

Engineering Contradiction:

Improvereliability of shift range switchingVSAvoidadaptability to different initial positions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system performs preliminary detection of the current shift range position before attempting to learn or use the initial position. The position sensor detects the current shift range, and the controller acquires switching edges from this detection, allowing the system to adapt to any initial position rather than requiring pre-positioning at a specific range.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical/physical positioning requirement (motor must be at P-range) with an electronic detection and calculation system. The controller uses position sensor signals and encoder data to electronically determine motor position and calculate switching edges, eliminating the need for physical pre-positioning.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If the system requires the SR motor to be positioned at the P-range for initial position learning, then the learning process is simple, but the system cannot determine rotational position when the motor is at other positions

Engineering Contradiction:

Improvesimplicity of initial position learningVSAvoidprecision of rotational position determination

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The position sensor acts as an intermediary between the motor position and the controller. It provides signal edges that indicate shift range positions, allowing the controller to determine rotational position without requiring the motor to be at a specific physical location. The encoder serves as another intermediary providing precise rotational position data.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system is designed to handle multiple initial positions universally. The position determination portion can acquire switching edges and determine rotational position regardless of where the motor starts, making the system adaptable to any initial condition rather than requiring a specific starting position.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If the controller drives the SR motor based on learned initial position at P-range, then shift range switching works normally, but the controller cannot operate after momentary power cut leaving motor at other positions

Engineering Contradiction:

Improvenormal operation of shift range switchingVSAvoidoperational reliability after power interruption

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system continuously monitors the current shift range position using the position sensor and encoder feedback. By acquiring switching edges from real-time position sensor signals, the controller can determine the current rotational position and adjust its control strategy accordingly, ensuring reliable operation after power interruptions regardless of motor position.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9416868B2Shift-by-wire controller

Publication Date: 2016.08.16 DENSO CORP

AI summary

A shift-by-wire controller is applied to a shift-by-wire system which switches a shift range of an automatic transmission by a driving force of a motor, and drives the motor according to an input signal. The shift-by-wire controller includes a position sensor, a position acquirement portion acquiring a switching edge corresponding to a position where the shift range is switched from the position sensor, an encoder detecting a rotational position of the motor, a determining portion determining whether the rotational position can be acquired as a present-position from the encoder, and a position determination portion. When the determining portion determines that the present-position cannot be acquired, the position determination portion drives the motor to switch the shift range, and determines a position of the motor based on the switching edge.