Haptic Driver Slew Control for Accurate Load Sensing
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Solution Overview
Problem
Existing methods for sensing displacement in haptic transducers, such as Hall sensors, are costly and inefficient, and the resonance frequency of haptic transducers varies due to sample-to-sample variations, assembly differences, and user interactions, making precise control challenging.
Innovation Solution
A system that includes an electromagnetic load driven by a driver with a first slew rate during haptic mode and a second slew rate during load sensing mode, using a current-sensing circuit with a sense resistor to accurately measure current and inductance, allowing for precise displacement measurement and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensors are used to measure displacement, then displacement measurement can be achieved, but cost increases and efficiency decreases
Solution Approach 1:
The patent replaces the mechanical Hall sensor-based displacement measurement system with an electrical measurement system. By measuring the inductance of the coil (an electrical parameter) and converting it to displacement information, the system eliminates the need for physical Hall sensors, thereby reducing cost and improving efficiency while maintaining measurement capability
Solution Approach 2:
The patent introduces inductance as an intermediary parameter to bridge the gap between electrical measurements and mechanical displacement. Instead of directly measuring displacement with complex sensors, the system measures coil inductance (which changes with displacement) and uses this as a proxy to infer position information
2Productivity
If high slew rate is used during haptic mode, then drive efficiency is improved, but measurement accuracy during sensing mode deteriorates
Solution Approach 1:
The patent implements dynamic slew rate adjustment based on operational mode. The slew rate is set to a first value (higher) during haptic drive mode to maximize drive efficiency, and switched to a second value (lower) during load sensing mode to optimize measurement accuracy. This dynamic adaptation resolves the contradiction by allowing each mode to have optimal parameters
Solution Approach 2:
The system periodically alternates between haptic drive mode and load sensing mode. During drive phases, high slew rate enables efficient haptic actuation; during sensing phases, low slew rate enables accurate current and inductance measurement. This periodic switching between contrasting operational states allows both high productivity and high measurement precision at different times
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 reduces the cost and inefficiencies of displacement sensing, enabling precise control of haptic transducers and optimizing displacement protection algorithms, while maintaining efficient drive levels.
Implementation Method 1
an electromagnetic load, a driver configured to drive the electromagnetic load with a driving signal
Implementation Method 2
a current-sensing circuit having a sense resistor coupled between the first terminal and an electrical node
Data Source
AI summary
A system may include an electromagnetic load, a driver configured to drive the electromagnetic load with a driving signal, and a processing system communicatively coupled to the electromagnetic load and configured to, during a haptic mode of the system couple a first terminal of the electromagnetic load to a ground voltage and cause the driving signal to have a first slew rate, and during a load sensing mode of the system for sensing a current associated with the electromagnetic load, couple the first terminal to a current-sensing circuit having a sense resistor coupled between the first terminal and an electrical node driven to a common-mode voltage and cause the driving signal to have a second slew rate lower than the first slew rate.