Electronic Power Steering Torque Rise Reduction
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Solution Overview
Problem
EPS devices experience increased steering force requirements in low-temperature conditions due to frictional forces, leading to a less efficient steering experience compared to room temperature.
Innovation Solution
An EPS device calculates compensation currents for viscous and Coulomb frictional forces using temperature and steering data to reduce torque rise, applying these currents to the motor to maintain a consistent steering feel across temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EPS device operates in low-temperature conditions, then the frictional force increases, but the steering force required increases excessively
Solution Approach 1:
The system changes the motor current parameter dynamically based on temperature conditions. When low temperature is detected, the control unit calculates and applies a compensation current to the motor, adjusting the electrical parameter to counteract the increased frictional force and maintain appropriate steering assist performance.
Solution Approach 2:
The system uses temperature sensor feedback to detect low-temperature conditions and steers angular velocity feedback to determine steering state. Based on this feedback information, the control unit dynamically adjusts the motor current to compensate for frictional force variations, creating a closed-loop control system that maintains consistent steering characteristics across temperature conditions.
2Reliability
If compensation current is increased to counteract friction, then steering assist performance improves, but energy consumption increases
Solution Approach 1:
The system applies compensation current selectively rather than continuously. The control unit calculates the compensation current only when low-temperature conditions are detected and steering operation is required. The compensation is applied partially - only to the extent needed to counteract the frictional force increase - avoiding excessive energy consumption while maintaining steering assist performance.
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 effectively reduces torque rise in low-temperature conditions, ensuring the driver experiences similar steering ease as at room temperature by compensating for increased frictional forces.
Implementation Method 1
the motor supplies steering assist power in proportion to the generated steering torque
Implementation Method 2
a viscous friction compensation current calculation unit configured to determine a viscous gain on the basis of a temperature sensed by a temperature sensor and to calculate a first compensation current using the determined viscous gain and a steering angular velocity
Implementation Method 3
a Coulomb friction compensation current calculation unit configured to determine a temperature gain on the basis of the sensed temperature, to determine a steering angle gain on the basis of an amount of accumulated steering angles, and to calculate a second compensation current using the temperature gain and the steering angle gain
Data Source
AI summary
The present embodiments relate to an electronic power steering device, and relates to a technology for reducing a torque rise resulting from an increase in frictional force in a low-temperature situation of the electronic power steering device. According to the present embodiments, a viscous friction compensation current is calculated using a viscous gain, which has been determined according to a damping coefficient estimated from a temperature sensed in a low-temperature situation of the electronic power steering device, and a steering angular velocity, a Coulomb friction compensation current is calculated using the sensed temperature and the mount of accumulated steering angles, and the calculated viscous friction compensation current and the Coulomb friction compensation current are added to the motor driving current and then supplied such that the driver can have the same feeling of driving, even in the low-temperature situation, as that in the room-temperature situation.