Electric Power Steering Control Circuit Battery Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric power steering apparatuses face challenges in meeting the high power demands of large cars, leading to excessive current extraction from batteries, which shortens their lifespan and can cause fuse blowouts, when auxiliary power supplies are connected in series with batteries.
Innovation Solution
An electric power steering apparatus with a charge-discharge circuit that selectively configures output modes based on battery and auxiliary power supply voltages, limiting current through the battery by defining an upper limit of electric power based on efficiency, voltage, and maximum current values, preventing excessive current extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage of the auxiliary power supply is lowered and control is provided to maintain a predetermined electric power by increasing the current, then the electric power supply demand is met, but the battery service life is shortened and fuse may blow
Solution Approach 1:
The patent applies dynamics by making the electric power limit variable rather than fixed. The control circuit dynamically adjusts the electric power limit based on real-time voltage detections from the battery and auxiliary power supply, allowing the system to adapt to changing voltage conditions while preventing excessive current extraction from the battery
Solution Approach 2:
The patent implements feedback by using voltage detectors to continuously monitor the voltage of the battery (VB) and auxiliary power supply (VC), then feeding this information back to the control circuit. The control circuit uses this feedback to calculate and adjust the electric power limit according to the formulas: η·VB·IB when first output mode is selected, or η·(VB+VC)·IB when second output mode is selected, where IB is the upper limit value of battery current
2Power
If the battery and auxiliary power supply are connected in series to meet large power demand, then the required electric power is supplied, but the current through the battery may exceed the maximum value and cause fuse blowout
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the electric power limit parameter based on voltage conditions. The control circuit changes the power limit parameter according to the detected voltages VB and VC, ensuring that the current through the battery never exceeds the predetermined upper limit value IB, thereby preventing fuse blowout while still meeting power demands
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A voltage detector 17 for detecting a voltage VB of a battery 9 as a main power supply and a voltage detector 18 for detecting a voltage Vc of an auxiliary power supply 14 are provided. On the basis of an upper limit value IB previously defined as the maximum value of current through the battery 9, a control circuit 6 defines an upper limit of the electric power supplied to the motor 4 as η·VB·IB (η representing the efficiency of the driving circuit 5) when a first output mode is selected in which the auxiliary power supply 14 is not used or defines the upper limit of the electric power supplied to the motor 4 as η·(VB+VC)·IB when a second output mode is selected in which the auxiliary power supply 14 is used as connected in series with the battery 9.