Handwheel Force Feedback Actuator With Variable Spring Preload
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Solution Overview
Problem
Steer-by-wire steering systems lack adequate force feedback to the driver, limiting the ability to replicate the mechanical steering system's tactile experience, and existing solutions are costly and inefficient.
Innovation Solution
A spring-driven handwheel actuator with actively controlled variable spring rate, integrating an electric motor and spring arrangement in series, allows for variable force feedback by adjusting the torsional load through a controlled spring seat, which is rotated by an electric motor and worm gear mechanism, with a damper and mechanical end stop for safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motor is used to provide force feedback in steer-by-wire steering systems, then force feedback can be provided to the driver, but the system becomes costly and complex
Solution Approach 1:
The patent replaces complex active mechanical feedback systems with a passive spring-based mechanical feedback system. The spring arrangement (including torsion springs and leaf springs) provides force feedback through pure mechanical means, eliminating the need for complex motors and sensors traditionally required for steer-by-wire force feedback, thereby reducing system cost and complexity while maintaining reliability
Solution Approach 2:
The spring arrangement serves itself by automatically providing force feedback through its inherent elastic properties. The system uses the vehicle's steering wheel and spring mechanics to generate feedback without requiring external power sources or active control systems, making the force feedback self-sufficient and reducing overall system complexity
2Device complexity
If a traditional linear spring arrangement is used with fixed spring rate, then the structure is simple, but the force feedback to the driver is inadequate and cannot be customized
Solution Approach 1:
The patent transitions from a static fixed spring rate system to a dynamic variable spring rate system. The spring arrangement can change its effective spring rate based on operating conditions, allowing the force feedback characteristics to be adjusted and customized for different driving scenarios while maintaining a relatively simple mechanical structure
Solution Approach 2:
The patent changes the spring rate parameter from a fixed value to a variable parameter. By using a combination of springs and mechanical linkages, the system achieves variable spring rate characteristics that can be adjusted to provide different force feedback levels, enabling customization without significantly increasing structural 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 system provides customizable force feedback to the driver, reduces system cost by downsizing the motor, and ensures safety with a mechanical end stop, while maintaining operational reliability in case of motor or control failure.
Implementation Method 1
a first spring for biasing the steering shaft in a first rotational direction, the first spring coupled to the steering shaft by a first static spring seat, a second spring for biasing the steering shaft in a second rotational direction opposite the first rotation direction
Implementation Method 2
The first and second springs can include torsion springs supported coaxially with the steering shaft
Implementation Method 3
Rotation of the controlled spring seat changes a torsional load applied to the steering shaft via at least one of the first spring or the second spring
Implementation Method 4
An electric motor can be configured to rotate the controlled spring seat. The electric motor can be coupled to a worm that drives a worm gear to rotate the controlled spring seat
Implementation Method 5
The electric motor can be coupled to a worm that drives a worm gear to rotate the controlled spring seat
Implementation Method 6
The handwheel actuator can include a damper for resisting rotation of the steering shaft
Data Source
AI summary
A handwheel actuator for a steering system includes a housing, a steering shaft supported by the housing and configured to be coupled to a handwheel for receiving driver input from a driver and transmitting feedback to the driver, a first spring for biasing the steering shaft in a first rotational direction, the first spring coupled to the steering shaft by a first static spring seat, a second spring for biasing the steering shaft in a second rotational direction opposite the first rotation direction, the second spring coupled to the steering shaft by a second static spring seat, a controlled spring seat coupled to the first spring and the second spring and rotatable to change a pre-load of at least one of the first or second springs. Rotation of the controlled spring seat changes a torsional load applied to the steering shaft via at least one of the first spring or the second spring.