Motor Stator Lamination Coating for Fail-Safe Handwheel Drag Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Steer-by-wire systems in vehicles lack a reliable mechanism for providing resistance to the handwheel during power failures or faults, which can lead to uncontrolled rotation and potential steering instability.
Innovation Solution
A handwheel actuator assembly with a stator comprising a stack of laminations coated with an electrically conductive material, allowing for increased eddy currents and hysteresis losses to generate significant drag torque, even without electrical power, ensuring the handwheel does not rotate freely and providing a safe and stable steering experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the stator uses electrically insulating coating between laminations to prevent axial current flow, then energy losses are reduced and torque generation is improved, but drag torque is severely restricted and the handwheel can rotate freely during power failures
Solution Approach 1:
The patent applies electrically conductive coating specifically at the axial contact surfaces between laminations, while maintaining insulating properties in other areas. This localized conductive treatment creates controlled eddy current paths that generate drag torque during power failures, while preserving the motor's normal operating efficiency by preventing unwanted axial current flow in non-contact regions.
Solution Approach 2:
The patent converts the typically harmful eddy currents (which cause energy losses) into a beneficial safety mechanism. By allowing controlled eddy current flow through conductive coating between laminations, the system generates drag torque that prevents free rotation during power failures, transforming what was previously a source of energy loss into a fail-safe protection mechanism.
2Reliability
If the stator uses electrically conductive coating between laminations to generate drag torque, then steering stability is improved during power failures, but energy losses increase due to eddy currents
Solution Approach 1:
The conductive coating is applied selectively only at the axial contact surfaces between laminations where it is needed for safety, rather than throughout the entire lamination structure. This localized application minimizes the overall eddy current paths and associated energy losses while still providing sufficient drag torque for steering stability during power failures.
3Reliability
If braking torque is used to provide resistance to handwheel rotation, then steering stability is improved, but active control of motor drive circuit is required which consumes additional energy and increases system complexity
Solution Approach 1:
The patent enables the motor stator to automatically generate drag torque through controlled eddy currents in the conductive coating, without requiring active control circuit intervention. The system self-regulates by allowing natural eddy current formation during power failures, eliminating the need for complex braking control logic while maintaining steering stability.
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 assembly achieves a drag torque of at least 50% of the resistance to rotation, ensuring the handwheel requires a minimum of 2 Nm to maintain constant speed, enhancing steering stability and safety by managing heat losses within the motor, reducing the risk of electronic circuit damage.
Implementation Method 1
allowing for increased eddy currents and hysteresis losses to generate significant drag torque
Implementation Method 2
allowing for increased eddy currents and hysteresis losses to generate significant drag torque
Data Source
AI summary
A mechanical assembly is disclosed. The assembly comprises: a housing, a shaft rotatably mounted with respect to the housing, one or more motors each having a stator and a rotor, the stator carrying a plurality of phase windings and the rotor carrying a plurality of magnet poles and being connected to the shaft, a control circuit adapted to control the current flowing into or out of the or each motor to cause a net torque to be applied to the shaft during normal operation, and in which the stator of at least one of the motors comprises a stack of laminations which each comprise a steel plate and an electrically conductive coating at least on the faces of the steel plate that contact adjacent laminations.