Capstan Brake Haptic Controller for Compliance and Grasp Force
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Solution Overview
Problem
Current VR haptic controllers struggle to render realistic human-scale forces and compliance feedback, often requiring large, power-hungry actuators or binary brake mechanisms that are not robust or cost-effective for simulating natural interactions with both rigid and compliant virtual objects.
Innovation Solution
The development of energy-storing resistive haptic controllers (ESR haptic controllers) that utilize capstan-based brakes and clutched springs to provide variable resistive forces and energy storage, allowing for human-scale force rendering without the need for large actuators, and offering a safer, more efficient, and cost-effective solution for simulating both rigid and elastic virtual objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If an active mechanism with a strong servo motor is used to produce strong grasping feedback, then the haptic feedback capability is improved, but the device becomes heavy, expensive, non-robust, and power-hungry
Solution Approach 1:
Instead of using an active servo motor to push the user's finger, the invention uses a passive brake mechanism that resists the user's own finger movement. The brake converts the kinetic energy of finger motion into resistive force through friction, eliminating the need for heavy active actuators while providing comparable haptic feedback.
Solution Approach 2:
The invention replaces the electro-mechanical servo motor system with a purely mechanical brake system. The brake uses friction between a brake pad and a drum (or disc) to generate resistive force, substituting complex electrical control systems with simple mechanical friction-based resistance.
2Force
If an active mechanism with a strong servo motor is used to produce strong grasping feedback, then the haptic feedback capability is improved, but the device becomes expensive
Solution Approach 1:
The brake mechanism uses inexpensive friction materials (brake pads) that can be easily replaced if worn. The simple mechanical design with no complex electronics or precision gears makes the device much cheaper to manufacture compared to servo motor-based systems.
3Force
If a brake mechanism is used to resist user applied force, then high forces can be sustained, but the grasp is locked at a certain point and requires manual release
Solution Approach 1:
The brake mechanism is designed to be dynamically controllable through electrical signals. By varying the brake torque in real-time based on sensor feedback, the system can smoothly transition between grasping and releasing states, eliminating the need for manual release while maintaining high sustained forces during grasping.
Solution Approach 2:
The system uses sensors to detect finger position and force, and this feedback is used to dynamically adjust the brake torque. This closed-loop control enables automatic release when appropriate, replacing manual release operation while maintaining the ability to sustain high forces during grasping.
4Force
If conventional haptic controllers are used, then they can provide basic force feedback, but they cannot render realistic human-scale forces and compliance feedback
Solution Approach 1:
The brake mechanism only applies resistance when the user's finger is moving, converting kinetic energy during motion into resistive force. During static holding, minimal power is consumed to maintain brake position, enabling human-scale force rendering with low overall power consumption compared to continuously operating servo motors.
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 ESR haptic controllers enable realistic haptic feedback by providing stable, safe, and efficient rendering of human-scale forces with low power consumption, supporting fine-grained dexterity and compliance simulations, thus enhancing the immersion and realism of VR interactions.
Implementation Method 1
an energy storage mechanism connected between the first and second capstans
Implementation Method 2
capstan-based brakes...provide variable resistive forces
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present concepts relate to haptic controllers. In one example the haptic controller can include first and second capstans rotationally secured to a base and an energy storage mechanism connected between the first and second capstans. The example haptic controller can also include a user engagement assembly secured to the first capstan and a controller configured to control rotational forces imparted on the user engagement assembly by controlling rotational friction experienced by the first and second capstans.