LRA Controller Switching to Open-Loop When BEMF Unreadable

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Solution Overview

Problem

Linear resonant actuators (LRA) face challenges in maintaining efficient control, particularly at low temperatures or high noise conditions where the back electromotive force (BEMF) signal becomes undetectable, leading to failure in closed-loop control.

Innovation Solution

A system and method that utilize a primary loop module for closed-loop control when the BEMF signal is detectable and an alternate cycle module for open-loop control when it is not, with the alternate cycle module delivering energy excitation pulses at a predetermined frequency to unfreeze the LRA and enable movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If closed-loop control is used to improve efficiency and performance, then power consumption is reduced and acceleration is improved, but the system fails when BEMF signal is undetectable at low temperatures or high noise conditions

Engineering Contradiction:

Improvecontrol reliabilityVSAvoidoperational adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The controller dynamically switches between closed-loop and open-loop control modes based on BEMF signal detectability. The system adapts its control strategy in real-time, using closed-loop control when BEMF is detectable and open-loop control when it is not, ensuring continuous operation across varying environmental conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the control parameter from BEMF-based closed-loop control to predetermined frequency open-loop control based on temperature and noise conditions. When temperature drops below a threshold or noise exceeds a threshold, the controller transitions to open-loop mode with predetermined excitation frequencies to maintain LRA operation

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If open-loop control is used to ensure operation under all conditions, then the system remains operational at low temperatures, but efficiency and performance are reduced

Engineering Contradiction:

Improveoperational adaptabilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The controller dynamically adjusts control mode based on environmental conditions. During normal operating conditions, closed-loop control is used for efficiency. When temperature drops below threshold or noise exceeds threshold, the system transitions to open-loop control to maintain operation, optimizing the balance between efficiency and reliability

Inventive Principle:

Principle #15Dynamics

3Speed

If closed-loop control is used to provide higher acceleration and performance, then startup and braking time is reduced, but the control system fails when BEMF signal is undetectable

Engineering Contradiction:

ImproveaccelerationVSAvoidcontrol reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system changes control parameters based on detectable conditions. When BEMF is detectable, closed-loop control provides high acceleration and performance. When BEMF becomes undetectable due to temperature or noise thresholds, the system switches to open-loop control with predetermined frequencies to maintain basic operation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system prepares for potential BEMF signal loss by having open-loop control mode ready as a backup. When closed-loop control becomes unreliable due to low temperature or high noise, the pre-programmed open-loop control takes over to ensure continuous operation, cushioning against control failure

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

Enables seamless switching between closed-loop and open-loop control, ensuring continuous operation of LRA even under extreme conditions by unfreezing the actuator and allowing motor action to occur, thereby maintaining performance and efficiency.

Implementation Method 1

a back electromotive force (BEMF) signal from the LRA representing the movement of the LRA

Methodology Applied

Scientific EffectBack electromotive force (BEMF): Electromagnetic Induction

Implementation Method 2

an alternate cycle module to control the LRA in open loop mode when the BEMF signal is undetectable... delivering energy excitation pulses at a predetermined frequency to unfreeze the LRA

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9800191B2Adaptive linear resonance actuator controller

Publication Date: 2017.10.24 TEXAS INSTRUMENTS INC

AI summary

A system includes a controller to control movement of a linear resonant actuator (LRA). The system includes a monitor in the controller to monitor a back electromotive force (BEMF) signal from the LRA representing the movement of the LRA. The monitor generates an indicator that indicates whether or not movement of the LRA has occurred. A primary loop module in the controller controls acceleration and braking of the LRA based on the monitored BEMF signal if the indicator from the monitor indicates that LRA movement has occurred. An alternate cycle module in the controller pushes the LRA at a predetermined frequency if the indicator from the monitor indicates that LRA movement has not occurred. The push is employed to move the LRA when the BEMF signal is undetectable by the monitor with respect to a predetermined threshold.