Motor Control Device for Reducing Torque Pulsation
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Solution Overview
Problem
Existing motor control systems face challenges in smoothly controlling motor rotation with complex configurations and high computational demands, particularly in reducing torque pulsation and output voltage calculations for three-phase brushless motors.
Innovation Solution
A control device that generates a control signal to alternately switch the upper and lower side switches in an AC voltage waveform, creating a third energization cycle that continuously changes the output voltage, allowing for smooth motor rotation with a simple configuration by varying the phase of the first and second energization cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a square wave AC voltage waveform is used for motor control, then the output voltage calculation is simple and hardware requirements are reduced, but torque pulsation occurs due to significant current direction changes
Solution Approach 1:
The AC voltage waveform is segmented into three distinct energization cycles (first, second, and third cycles) within each phase period. The first and second cycles use simple square wave patterns with upper and lower switch alternation, while the third cycle introduces continuous output voltage variation. This segmentation allows the system to maintain simplicity in most cycles while introducing smoothing only where necessary to reduce torque pulsation.
Solution Approach 2:
The patent applies periodic action by repeating the three-cycle pattern across all phases and time periods. The inverter alternates between different energization patterns in a periodic manner, switching between the first, second, and third energization cycles according to a predetermined sequence. This periodic structure maintains computational simplicity while progressively reducing torque pulsation through the third cycle's continuous voltage variation.
2Object-generated harmful factors
If a sine wave AC voltage waveform is used for motor control, then torque pulsation is reduced due to gradual current direction changes, but the amount of calculation increases significantly requiring high-performance hardware
Solution Approach 1:
Instead of using expensive high-performance computers and memory required for full sine wave calculation, the patent employs a simpler control approach that achieves similar torque smoothing effects with basic calculation capabilities. The third energization cycle provides continuous voltage variation without requiring complex real-time sine wave computations, effectively replacing high-performance hardware with a more economical solution.
Solution Approach 2:
The patent changes the control parameter from full sine wave voltage calculation to a hybrid approach where only specific portions (the third energization cycle) require continuous voltage variation. This parameter change reduces the computational burden significantly while maintaining the torque pulsation reduction benefit, as the continuous voltage change is applied selectively rather than across the entire waveform.
3Ease of operation
If sine wave control is implemented with continuous output voltage calculation for all phases, then smooth motor rotation is achieved, but calculation time and processing load increase
Solution Approach 1:
The patent extracts the continuous voltage variation requirement from the entire AC waveform and applies it only to the third energization cycle. By taking out this specific function from the global control strategy and localizing it to a particular cycle segment, the system achieves smooth motor rotation without requiring continuous calculation for all phases and time periods, significantly reducing processing time and computational load.
Data Source
AI summary
A signal generator generates a control signal that causes an inverter to supply a drive current in an AC voltage waveform to each phase of a motor. The signal generator alternately repeats a first energization cycle in which only a switch on an upper side of an arm is set to an ON state and a second energization cycle in which only a switch on a lower side of the arm is set to the ON state in the AC voltage waveform having a third energization cycle therebetween, changes the switches on the upper side and the lower side of the arm to the ON state and an OFF state in order in the third energization cycle, continuously changes an output voltage of the switch that has been further changed to the ON state, and generates a control signal to cause waveforms of the preceding and succeeding first energization cycle and second energization cycle to be continuous with the third energization cycle by varying a phase of the first to the third energization cycles in each phase.