Motor Control Circuit Speed Curve Flexibility via Inflection Points
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Solution Overview
Problem
Conventional motor control circuits have limited flexibility in setting speed curves for motor rotational speeds due to memory capacity constraints and processing speed limitations, allowing only simple linear connections between a few points.
Innovation Solution
A motor control circuit with a speed command analyzing unit, storage unit, and target rotational speed determining unit that sets inflection points for the duty cycle range, calculates rotational speeds based on parameter information including resolution and inflection points, and generates drive control signals to achieve a high degree of flexibility in speed curve settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional driver IC uses non-volatile memory to store speed curve parameters, then the function can be changed according to application, but the settable speed curve is restricted due to memory capacity limitations
Solution Approach 1:
The speed curve is segmented into multiple sections with inflection points dividing the duty cycle range. Each section can be independently configured with its own start and end duty cycles and rotational speeds. This segmentation allows complex speed curves to be constructed from simpler segments, increasing flexibility without requiring large memory capacity to store complete curve data.
Solution Approach 2:
The system uses parameter information including resolution information (indicating duty cycle resolution) and rotational speed information (indicating rotational speed at inflection points) to dynamically generate speed curves. By changing these parameters, different speed curves can be created without storing multiple complete curve datasets, thus reducing memory requirements while maintaining adaptability.
2Adaptability or versatility
If more inflection points are added to increase speed curve flexibility, then the degree of flexibility increases, but the processing load and computation complexity increase
Solution Approach 1:
The speed curve is divided into multiple sections with inflection points as boundaries. Each section represents a simpler linear or polynomial relationship between duty cycle and rotational speed. This segmentation reduces the complexity of calculating any single section while allowing flexible combination of multiple sections to achieve overall curve flexibility.
Solution Approach 2:
The system pre-calculates and stores parameter information for inflection points and resolution in non-volatile memory during manufacturing or initialization. This preliminary action allows the runtime processing to simply retrieve and apply these parameters without performing complex calculations, thus reducing real-time processing load while maintaining the ability to represent complex speed curves.
3Measurement precision
If high-resolution duty cycle measurement is implemented to improve speed control precision, then the rotational speed determination becomes more accurate, but the processing load increases
Solution Approach 1:
The system uses resolution information as a parameter to define the measurement precision required for duty cycle. By adjusting this parameter, the system can adapt the measurement resolution to match the actual control requirements. This allows high precision measurement only when necessary, balancing measurement accuracy with processing efficiency.
Solution Approach 2:
The system implements duty cycle measurement with sufficient resolution to cover the full range of possible speed commands, but only processes and applies the precision level that is actually needed for the current operating conditions. This partial action approach avoids the excessive processing load that would result from always using maximum resolution, while still maintaining the capability for high precision when required.
Data Source
AI summary
The degree of flexibility of a speed curve for a target rotational speed of a motor is to be increased. A motor control circuit 11 measures a duty cycle of an input speed command signal Sc indicating a target rotational speed of a motor 50 to be driven, sets an inflection point In for each duty cycle obtained by equally dividing a possible duty cycle range assumed by the speed command signal Sc based on resolution information 301 indicating a resolution of the duty cycle of the speed command signal Sc, calculates a rotational speed corresponding to the measured duty cycle of the speed command signal Sc based on rotational speed information 302 indicating rotational speeds at the inflection points In on a speed curve and the set inflection points In, and determines the calculated rotational speed as the target rotational speed.