Pitman Arm Drive Control Torque Distribution
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Solution Overview
Problem
Conventional electric power steering systems with redundant configurations face challenges in achieving accurate position control of the pitman arm due to inconsistencies in drive motor control, particularly in bi-wire type EPS, where independent current control can lead to calculation inconsistencies and difficulties in verifying adequate drive torque, especially with sensor failures and unintended control commands.
Innovation Solution
A drive control device with multiple drive instruction systems, each comprising a communication unit, angle detection unit, calculation unit, distribution unit, and drive control unit, that performs torque distribution based on a predetermined ratio and switches modes to maintain synchronization and accuracy, including master and slave modes, abnormality detection, and torque reduction mechanisms to handle failures and inconsistencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If independent current control is used for each line in redundant configuration, then control flexibility is improved, but inconsistency in drive motor control occurs
Solution Approach 1:
The patent introduces a torque distribution unit as an intermediary component that receives the total drive torque command and distributes it to multiple drive instruction systems according to predetermined ratios. This mediator ensures that all lines receive coordinated torque commands, preventing inconsistency while maintaining the ability to adjust distribution ratios for different operating conditions.
Solution Approach 2:
The patent segments the drive control into multiple independent drive instruction systems, each capable of controlling a separate drive motor. By dividing the control function while maintaining centralized torque distribution, the system achieves both flexibility through independent line control and consistency through unified torque management.
2Measurement precision
If torque adjustment is performed using total drive command and state variables, then control precision is improved, but calculation complexity increases
Solution Approach 1:
The patent performs preliminary distribution of the total drive torque command into allocated torque values for each drive instruction system before detailed control calculations. This preliminary action simplifies subsequent calculations by providing pre-determined torque targets, reducing the computational burden while maintaining precision through the use of state variables like measured currents in the final control stage.
3Reliability
If multiple drive instruction systems operate independently, then system redundancy is improved, but position control accuracy deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where each drive instruction system uses its measured current (state variable) to adjust its control output. This feedback ensures that each redundant line maintains accurate position control by continuously comparing actual performance with commanded performance and making real-time corrections, thereby preserving high position control accuracy despite system redundancy.
Data Source
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AI summary
A drive control device (240) includes a plurality of drive instruction systems (300). Each drive instruction system includes a communication unit (400), angle detection unit (315), calculation unit (401), distribution unit (402), and drive control unit (403). The communication unit (400) receives an instruction about a position of a pitman arm (330) from a higher-level device. The angle detection unit (315) detects the angle of the pitman arm (330). The calculation unit (401) calculates a drive torque for the pitman arm (330) based on the instruction and the angle of the pitman arm (330). The distribution unit (402) distributes the drive torque according to a predetermined ratio. The drive control unit (403) controls the drive unit (320). One of the drive instruction systems (300) performs a torque distribution process including a calculation process by the calculation unit (401) and a distribution process by the distribution unit (402). The drive control unit (403) in each drive instruction system synchronously controls the drive unit (320) with a torque distributed by the torque distribution process.