Motor Control Device Reducing Torque Ripple via Parameter Sharing
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Solution Overview
Problem
In electric power steering systems, differences in sensor readings between redundant control systems can lead to inconsistent motor current command values, resulting in torque ripples and noise and vibration (NV) issues when a parameter output circuit malfunctions.
Innovation Solution
A motor control device with two control systems that share parameters from a functioning system to calculate assist command values, ensuring consistent motor control and reducing NV by averaging sensor inputs and sharing parameters in case of malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two independent control systems are used for redundant motor control, then system reliability is improved, but differences in sensor readings cause inconsistent command values leading to torque ripples and noise
Solution Approach 1:
The patent merges the parameter processing of two independent control systems by having both control calculation circuits share a single parameter output unit. This combining approach ensures both systems use identical sensor readings and calculation results, eliminating command value differences while preserving redundant control capability for reliability.
Solution Approach 2:
The patent introduces a shared parameter output unit as an intermediary between the two control systems. This mediator provides unified sensor parameter output to both control calculation circuits, ensuring consistency in command values while allowing the control systems to operate independently for reliability.
2Adaptability or versatility
If separate parameter output units are used for each control system, then system independence is improved, but parameter differences cause inconsistent assist command values
Solution Approach 1:
The patent merges the parameter output function into a single shared unit that serves both control systems. This ensures both independent control systems receive identical parameter data, maintaining measurement precision and parameter consistency while preserving system independence for control calculations.
Solution Approach 2:
The shared parameter output unit performs a universal function by providing parameter output to multiple control systems simultaneously. This multi-functional approach ensures parameter consistency across systems while allowing each control system to maintain its independent operation capability.
3Measurement precision
If a single control system is used, then parameter consistency is improved, but system reliability decreases when the parameter output unit malfunctions
Solution Approach 1:
The patent segments the control function into two independent control calculation circuits that share a common parameter output unit. This segmentation allows the system to maintain parameter consistency through the shared unit while providing redundancy through separate control circuits, improving reliability against parameter output failures.
Solution Approach 2:
The patent prepares for potential parameter output unit failures by having two independent control calculation circuits ready to take over. This beforehand cushioning approach ensures that if the shared parameter output unit fails, the redundant control circuits can maintain system operation, preserving reliability.
Data Source
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AI summary
There is provided a motor control device capable of preventing occurrence of a difference in command value between control systems and improving the performance of reducing torque ripples and noise and vibration (NV) of a motor, unlike in a case where a motor is controlled by control systems that are independent from each other. In a motor control device (4), at least one of parameters for a first control system is shared by both of the systems, and a first control calculation circuit (31) and a second control calculation circuit (41) calculate the assist command values based on the parameter. Thus, motor drive circuits of the control systems drive motor coils (15u, 15v, 15w, 16u, 16v, 16w) based on the assist command values. Namely, when the steering torques and the vehicle speeds for the control systems (30, 40) are all normal, assist control circuits (33, 43) of the control systems (30, 40) calculate the assist command values based on the steering torque (Th1) and the vehicle speed (S1).