Motor Drive Bit-Shift PWM Control for Higher Resolution
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Solution Overview
Problem
Brushless DC motors experience instability and inefficiency due to insufficient PWM and rotational speed resolutions, leading to increased power consumption and manufacturing costs when trying to improve resolution by increasing operating frequency.
Innovation Solution
A method that increases PWM or rotational speed resolution by N bits without raising the processing circuit's operating frequency, involving conversion, right-shifting operations, and logical operations to generate PWM signals for the motor driving system, allowing for improved voltage and speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the operating frequency of the processing circuit is increased to improve PWM resolution, then the PWM resolution is improved, but the power consumption and manufacturing cost of the processing circuit increase
Solution Approach 1:
The patent changes the parameter of resolution representation from frequency-based to bit-width-based. By performing bit manipulation operations (right-shifting, logical operations) on the command count value, the system achieves higher PWM resolution (increasing by N bits) without changing the operating frequency of the processing circuit, thus avoiding increased power consumption
Solution Approach 2:
The patent replaces the conventional approach of using higher frequency (temporal dimension) to achieve higher resolution with a data processing approach (bit manipulation). Instead of increasing the speed of the PWM generation mechanism, the system uses logical operations to process the command count value and generate high-resolution PWM signals, substituting a mechanical/frequency-based solution with a computational one
2Measurement precision
If the operating frequency of the processing circuit is increased to improve rotational speed resolution, then the rotational speed resolution is improved, but the power consumption and manufacturing cost of the processing circuit increase
Solution Approach 1:
The patent applies the same parameter change principle for rotational speed resolution as for PWM resolution. By manipulating the bit width of the command count value through right-shifting and logical operations, the system achieves N-bit increase in rotational speed resolution without increasing the processing circuit's operating frequency, thereby maintaining low power consumption
3Ease of manufacture
If the PWM resolution is insufficient, then the manufacturing cost is reduced, but the brushless DC motor runs unsmoothly and becomes unstable
Solution Approach 1:
The patent uses bit manipulation to increase PWM resolution by N bits without requiring higher operating frequency. This approach maintains manufacturing cost effectiveness (avoiding expensive high-frequency processors) while achieving the high PWM resolution needed for smooth and stable motor operation. The bit-wise operations on command count value provide a low-cost path to high reliability
Solution Approach 2:
The patent substitutes the conventional trade-off between cost and performance by using computational bit manipulation instead of hardware frequency increases. This allows the system to achieve high motor stability and smooth operation (requiring high PWM resolution) without incurring the manufacturing costs associated with high-frequency processing circuits
4Device complexity
If the rotational speed resolution is insufficient, then the processing circuit complexity is reduced, but the brushless DC motor cannot run at low rotational speeds and exhibits large rotational speed ripple
Solution Approach 1:
The patent changes the approach to achieving high rotational speed resolution from hardware complexity (high-frequency counters, advanced timers) to software-based bit manipulation. By performing N-bit right-shifting and logical operations on the command count value, the system achieves fine rotational speed control including low speeds without increasing processing circuit complexity
Solution Approach 2:
The patent replaces complex hardware mechanisms needed for high rotational speed resolution with simple bit manipulation operations. This substitution allows the processing circuit to maintain low complexity while achieving the ability to control low rotational speeds accurately and reduce rotational speed ripple through precise PWM generation
Data Source
AI summary
A method for increasing a resolution by N bits performed by a processing circuit of a motor driving system, where N is a positive integer, and the method includes: performing a conversion upon an analog command, to generate a command count value; performing a first N-bit right-shifting operation upon the command count value, to generate an initial output value; performing a logical operation upon the command count value, to generate a low bit value; generating an overflow value according to the low bit value; and determining a final output value according to the initial output value and the overflow value.