Magnetorheological Haptic Brake Layout for High Torque in Compact Knobs
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Solution Overview
Problem
Existing haptic operator control devices for vehicles face challenges in achieving a high braking moment with small diameters and structural volumes while maintaining cost-effectiveness and precision, as the magnetic field saturation in small shafts limits the achievable braking moment.
Innovation Solution
A haptic operator control device with a magnetorheological brake system featuring a rotatable operator control part, utilizing a magnetorheological medium and a magnetic field source, where the electrical coil is wound transversely to the axial direction, allowing for a larger core diameter and increased magnetic flux, and the inner brake component can be made of lightweight materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the diameter of the shaft is reduced to achieve a compact structure, then the structural volume is reduced, but the magnetic field saturation occurs more quickly, limiting the achievable braking moment
Solution Approach 1:
The patent transitions from a conventional axial magnetic field configuration to a radial magnetic field configuration. The coil is arranged radially around the shaft, generating magnetic flux that flows radially through the brake components rather than axially. This dimensional change in field orientation allows the magnetic circuit to utilize the radial space more effectively, avoiding saturation in the limited axial path through the small-diameter shaft.
Solution Approach 2:
The patent employs localized magnetic field generation through radially arranged coil segments that can be independently controlled. Different radial zones of the brake components can have different magnetic field strengths applied locally, optimizing the braking moment distribution across the contact surfaces while preventing saturation in any single region of the compact shaft structure.
2Force
If longer rolling elements are used to increase braking moment, then the magnetic field acts over a longer distance, but the magnetic field strength per unit area decreases due to distribution over larger area
Solution Approach 1:
The radial arrangement of the coil and magnetic field generation creates concentrated magnetic flux paths that pass through the rolling elements in the radial direction. This radial field configuration maintains high field strength at each contact point between the rolling elements and brake components, even when the elements are long, because the field does not get distributed along the axial length but rather concentrates through the radial thickness of each element.
3Force
If the coil is wound axially around the shaft, then the magnetic field flows axially, but the core diameter must be limited which restricts the magnetic flux and braking moment
Solution Approach 1:
The patent replaces the axial coil winding configuration with a radial coil arrangement where the coil windings extend in the radial direction rather than axially. This allows the magnetic field to flow radially through the brake components, utilizing the available radial space in the compact structure. The radial configuration eliminates the constraint of axial core diameter limitation, as the magnetic path now follows the radial dimension which is more readily available in compact designs.
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 solution enables the generation of higher braking moments with reduced structural space and cost, while allowing for scalable design adaptations, enhancing haptic feedback and operational precision.
Implementation Method 1
Magnetorheological fluids have, for example, ultrafine ferromagnetic particles, for example carbonyl iron powder, distributed in an oil. In magnetorheological liquids, use is made of spherical particles which have a diameter of 1 to 10 μm owing to a production process, wherein the particle size and shape are not uniform. If a magnetic field is applied to such a magnetorheological fluid, the carbonyl iron particles of the magnetorheological fluid interlink along the magnetic field lines, such that the rheological characteristics of the magnetorheological fluid (MRF) are influenced considerably (transmissible shear stresses) in a manner dependent on the form and strength of the magnetic field.
Implementation Method 2
The magnetorheological brake device comprises at least two brake components which are rotatable or at least pivotable relative to one another and of which one is coupled to the rotatable operator control part. The second brake component, as outer brake component, surrounds the first brake component, as inner brake component, at least in certain portions.
Data Source
AI summary
A haptic operating device for vehicles. The device has a rotatable operating part, a magnetic field source, and a magnetorheological braking device for braking a rotational movement of the operating part. The magnetorheological braking device has two braking components which can be rotated relative to one another and one of which is coupled to the rotatable operating part. The second brake component, acting as an outer brake component, surrounds the first brake component that acts as an inner brake component. A closed magnetorheological brake chamber is provided with a magnetorheological medium and is formed between the two brake components and has a peripheral braking gap.