Pointing Device Lifting Detection Using MEMS Accelerometers
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Solution Overview
Problem
Pointing devices, especially those using inertial sensors, face challenges in accurately determining when they are lifted off a surface, leading to unwanted cursor movement and limited maneuvering space, as they continue to detect motion even when not in contact with the surface.
Innovation Solution
A pointing device equipped with a combination of two-axes and single-axis MEMS accelerometers, connected to a microcontroller, which automatically detects the lifting state and switches between 2D and 3D operation modes, inhibiting cursor movement when lifted, using a control stage to process acceleration signals and determine if the device is in contact with a surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inertial sensors are used to enable the mouse to operate without contact with the sliding surface, then the mouse can continue to detect motion when lifted, but unwanted cursor movement occurs and maneuvering space is limited
Solution Approach 1:
The system dynamically switches between 2D mode (when mouse is on surface) and 3D mode (when mouse is lifted) based on real-time detection of the mouse state. This dynamic adaptation allows the system to optimize cursor control behavior according to the current operational context, preventing unwanted cursor movement during lifting while maintaining full functionality when in contact with the surface.
Solution Approach 2:
The system changes the operational parameters of the inertial sensor based on the detected mouse state. When the mouse is lifted, the system modifies how acceleration data is processed and interpreted, switching from 2D plane-based processing to 3D space-based processing. This parameter change ensures accurate cursor control in both contact and non-contact states.
2Area of stationary object
If the mouse is lifted to recover maneuvering space, then more space becomes available, but the cursor continues to move unintentionally
Solution Approach 1:
The system continuously monitors the mouse state through inertial sensors and provides feedback to determine whether the mouse is in contact with the surface or lifted. Based on this feedback, the system automatically adjusts its operation mode, enabling the user to lift the mouse to recover space without causing unwanted cursor movement, as the system will detect the lifted state and switch to appropriate control behavior.
3Measurement precision
If optical or electromechanical transducers are used, then contact with the sliding surface is required for accurate operation, but they can still detect motion when separated from the surface
Solution Approach 1:
The system replaces optical or electromechanical transducers with inertial sensors that use micro-electro-mechanical systems (MEMS) technology. This substitution enables the mouse to accurately detect motion in three-dimensional space without requiring contact with the sliding surface, while the control stage processes the inertial data to provide accurate cursor control in both contact and non-contact states.
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 automatic detection of lifting, preventing unwanted cursor displacement and allowing the device to function both as a 2D and 3D pointing peripheral, enhancing user interaction by maintaining accurate cursor control and expanding maneuvering space.
Implementation Method 1
an inertial sensor (5) connected to the board (3) so as to be fixed with respect to the shell (2) and comprising a first, two-axes, accelerometer (5a) and a second, single-axis, accelerometer (5b), both of micro-electro-mechanical type
Implementation Method 2
the control stage (15) detects a non-zero acceleration along the third detection axis Z using the third acceleration signal AZ
Data Source
AI summary
A pointing device for a computer system includes: a first movement sensor for detecting movements of the device along a first axis and a second axis; a second movement sensor, for detecting movements of the device along a third axis not coplanar with the first and second axes; and a processing unit associated to the movement sensors for producing a plurality of movement signals indicating the movement of the device along the first, second, and third axes. The processing unit includes a control stage, for controlling the production of the movement signals on the basis of a response of the second movement sensor.