Motor Duty Limit Control Across Driving Modes and Speed
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Solution Overview
Problem
Conventional motor control devices impose excessive restrictions on motor output performance due to a common duty limit value set for different driving modes, leading to insufficient output in certain conditions.
Innovation Solution
A motor control device that switches between non-free and rectangular wave driving modes, with an upper limit value setting part that adjusts duty ratio limits based on rotational speed and mode, using different slope information for each mode to prevent overcurrent and maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common duty limit value is set for all driving modes to protect the motor, then motor protection is ensured, but output performance is insufficient in high-speed regions
Solution Approach 1:
The patent applies dynamics by making the duty ratio upper limit value changeable based on operating conditions. Specifically, the system transitions from a fixed common limit to a dynamic limit that varies with rotational speed and driving mode. In high-speed regions, the limit increases to allow higher output, while in low-speed regions it maintains protection levels, thus resolving the contradiction between protection and performance.
Solution Approach 2:
The patent changes the parameter of duty ratio upper limit value based on rotational speed and driving mode. By introducing speed-dependent limit values (higher limits for high-speed rectangular wave mode, lower limits for low-speed non-free mode), the system optimizes output performance while maintaining motor protection across different operating conditions.
2Productivity
If a high duty ratio limit is set to maximize output performance, then output performance is improved, but overcurrent risk increases
Solution Approach 1:
The patent applies local quality by setting different duty ratio limits for different operating regions. High duty ratio limits are applied locally in high-speed regions where overcurrent risk is lower, while low duty ratio limits are applied locally in low-speed regions where overcurrent risk is higher. This spatially differentiated approach allows maximum output performance while maintaining safety.
Solution Approach 2:
The system changes the duty ratio limit parameter based on rotational speed and driving mode characteristics. By increasing the limit in high-speed regions and maintaining lower limits in low-speed regions, the system enables high output performance when safe, while preventing overcurrent in vulnerable operating conditions.
3Productivity
If different duty limit values are set for different driving modes, then output performance is optimized, but control complexity increases
Solution Approach 1:
The patent makes the duty ratio upper limit value dynamic based on rotational speed and driving mode detection. The control unit automatically selects appropriate limit values based on current operating conditions, providing optimized performance without requiring complex manual intervention or multiple independent control systems.
Solution Approach 2:
The control unit serves multiple functions: it detects driving mode, determines rotational speed, selects appropriate duty ratio limits, and controls motor output. This multi-functional approach consolidates control logic into a single unit, managing complexity while enabling mode-specific optimization.
Data Source
AI summary
A motor control device includes a driving control part and an upper limit value setting part. The driving control part controls motor driving by switching between a first driving mode and a second driving mode, and controls an output duty ratio so as not to exceed a duty ratio upper limit value. The upper limit value setting part sets, as the duty ratio upper limit value, a low rotation duty ratio upper limit value, a maximum duty ratio upper limit value corresponding to a maximum output value, and an upper limit value of a transition period from the low rotation duty ratio upper limit value to the maximum duty ratio upper limit value, and changes slope information indicating a change amount in the upper limit value of the transition period according to the driving mode when switching between the first driving mode and the second driving mode.