Force Feedback Handle With Dynamic Constraint for Stiffness Rendering
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Solution Overview
Problem
Conventional impedance and admittance force feedback devices face instability issues in simulating large stiffness and free space environments, respectively, due to their mechanical design features.
Innovation Solution
A force feedback handle device with a degree-of-freedom, comprising a driving part, a link part, and a frame part, where the driving part includes a motor, reducer, and dynamic physical constraint, and the link part features a force sensor and encoder, allowing for measurement of user-applied forces and positions to provide realistic feedback of both small friction and small inertia in free space and large stiffness in constraint environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an impedance force feedback device uses low inertia and low friction mechanical features to achieve good free space simulation, then the device can provide sufficient back-drivability, but it has instability problems during large stiffness rendering
Solution Approach 1:
The patent applies dynamics by making the mechanical constraint adjustable rather than fixed. The dynamic physical constraint can switch between constrained and unconstrained states, allowing the system to adapt its mechanical properties in real-time. This resolves the contradiction by providing low friction/inertia when unconstrained (for back-drivability) and high stiffness when constrained (for stability during large stiffness rendering).
Solution Approach 2:
The patent changes the mechanical parameters of the system dynamically. By adjusting the constraint state between locked and unlocked positions, the system transitions between different stiffness and friction regimes. This allows the same mechanical system to exhibit both low inertia/low friction characteristics and high stiffness characteristics as needed, resolving the stability issue during large stiffness rendering while maintaining good back-drivability.
2Reliability
If an admittance force feedback device uses large stiffness mechanical features to achieve good large stiffness environment simulation, then the device can provide stable large stiffness rendering, but it has instability problems for free space and small stiffness rendering
Solution Approach 1:
The patent makes the mechanical constraint dynamic rather than static. The constraint can be engaged or disengaged based on operational needs, allowing the system to switch between high stiffness mode (for stable large stiffness rendering) and low constraint mode (for free space back-drivability). This resolves the contradiction by providing both characteristics at different times through dynamic adjustment.
Solution Approach 2:
The system dynamically changes its mechanical parameters by adjusting the constraint position. When the constraint is engaged, the system exhibits large stiffness for stable rendering. When disengaged, it provides low constraint for free space operation with good back-drivability. This parameter switching resolves the instability issue in free space while maintaining stability during large stiffness rendering.
3Strength
If a force feedback device uses a reducer with large gear ratio to increase mechanical stiffness, then the device can simulate large stiffness environment, but the device complexity increases
Solution Approach 1:
The patent extracts the stiffness enhancement function from the traditional reducer mechanism. Instead of relying on a complex large gear ratio reducer, the system achieves mechanical stiffness through a simple constraint mechanism that locks the link at specific positions. This eliminates the need for complex reduction gearing while maintaining large stiffness capability, thus reducing device complexity.
Solution Approach 2:
The patent introduces a dynamic physical constraint as an intermediary mechanism between the motor and the output link. This constraint acts as a mediator that provides mechanical stiffness when engaged without requiring complex gear reduction. The constraint serves as a simpler alternative to traditional reducers, achieving the same stiffness effect with reduced complexity.
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
The device enhances stiffness performance, maintains low inertia, and provides a realistic feeling of hard surfaces, improving interaction by decoupling actuation and link mechanics and using incremental encoder measurements to reduce costs.
Implementation Method 1
a first encoder (4), a motor (5), a reducer (6), and a dynamic physical constraint (8); wherein the dynamic physical constraint (8) is connected to an output shaft of the reducer (6), the motor (5) is connected to an end of the reducer (6), the first encoder (4) is connected to an end of the motor (5)
Data Source
AI summary
A force feedback handle device with a degree-of-freedom includes: a driving part (1), a link part (2) and a frame part (3); wherein the driving part (1) and the link part (2) are both installed on a top board (9), and a rotation axis of the link part (2) coincides with a rotation axis of the driving part (1); the driving part (1), the link part (2) and the frame part (3) are fixed and connected by bolts. A working method of the force feedback handle device includes four steps. The force feedback device of the invention has low inertia and high stiffness performance, which improves overall interaction performance of the force feedback device. The structure is simple and a manufacturing cost is low.