Motor-Driven Power Steering Inverter Two-Phase Operation Control
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Solution Overview
Problem
In motor-driven power steering (MDPS) systems, when an error occurs in one phase of the inverter circuit, the sudden switch to manual mode can disrupt assist power, leading to uneven steering feelings and potential safety hazards, and requires additional components like relays and capacitors, increasing costs.
Innovation Solution
A method where the inverter operating unit generates a two-phase operation command by projecting a Q-axis command onto a two-phase operation axis, performs proportional integral (PI) control, and applies the resulting two-phase operation voltage to maintain assist power using the other two phases, converting it into a pulse width modulation (PWM) signal to operate the motor, thereby preventing sudden power disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MDPS switches to manual mode when an error occurs in one phase of the inverter circuit, then the reliability of the system is improved by blocking the error phase, but the assist power is suddenly stopped causing steering feeling disruption and safety hazards
Solution Approach 1:
The patent extracts and blocks only the faulty phase from the inverter circuit while maintaining operation of the other two healthy phases. This allows the system to continue providing assist power through the remaining phases rather than completely shutting down, thus maintaining steering assistance while isolating the error source.
Solution Approach 2:
The control unit detects phase errors in advance and automatically switches to two-phase operation mode before complete system failure occurs. This preliminary detection and switching action prevents sudden assist power loss and maintains steering assistance continuity.
2Reliability
If relays and capacitors are used to block the error phase, then the reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical relay-based phase blocking with an electronic control solution. The control unit uses software/logic to detect phase errors and automatically adjusts the inverter output to operate in two-phase mode, eliminating the need for physical relays and capacitors that would otherwise be required to block faulty phases.
Solution Approach 2:
The inverter circuit is designed to automatically adapt to phase failures through control unit logic. When a phase error is detected, the system self-adjusts by redistributing the inverter output across the remaining healthy phases, making the system self-healing without requiring external components or manual intervention.
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
This method ensures a consistent assist power is maintained, enhancing driving safety by preventing abrupt steering feel changes and reducing costs by eliminating the need for additional components like relays and capacitors, while allowing for more precise control through PWM.
Implementation Method 1
calculating, by the inverter operating unit, a two-phase operation voltage by performing proportional integral (PI) control on the two-phase operation command converted into the actual operation axis
Implementation Method 2
the inverter operating unit may convert the two-phase operation voltage into a pulse width modulation (PWM) signal, and apply the converted PWM signal
Implementation Method 3
an assist power generated by the rotation of the motor
Data Source
AI summary
A method for operating a motor of a motor-driven power steering (MDPS) includes: generating, by an inverter operating unit, a two-phase operation command by projecting a Q-axis command onto a two-phase operation axis, when an error occurs in any one of three phases; converting, by the inverter operating unit, coordinates of the two-phase operation command into an actual operation axis; calculating, by the inverter operating unit, a two-phase operation voltage by performing proportional integral (PI) control on the two-phase operation command converted into the actual operation axis; and operating, by the inverter diving unit, a motor by applying the two-phase operation voltage to an inverter unit.