Motor Driving Apparatus Torque Ripple Reduction
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Solution Overview
Problem
Existing motor driving apparatuses face challenges in reliably starting motors under high driving loads due to torque ripple issues, which require either reducing the load or increasing the motor output, limiting design flexibility and increasing power consumption.
Innovation Solution
A motor driving apparatus with a rotor having a cylindrical magnet and alternately multi-polarized magnetic poles, using a control circuit to switch the energization of coils based on position detection sensors, allowing direct current energization to position the rotor effectively for starting, thereby minimizing torque ripple and enabling reliable start-up under high loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If advance angle is set to change rotational characteristics, then motor speed can be adjusted, but torque ripple increases and reliable starting under high load becomes difficult
Solution Approach 1:
The control circuit performs preliminary DC energization of the coils before starting motor rotation. This preliminary action positions the rotor at a specific angular position where the magnetic pole portions are optimally aligned, ensuring that the motor can reliably overcome high driving loads during startup. After this preliminary positioning, normal AC energization with advance angle control begins, combining the benefits of both approaches.
2Reliability
If motor output is increased to overcome torque ripple and enable reliable starting, then starting reliability improves, but power consumption increases
Solution Approach 1:
Instead of continuously operating at high power output, the system performs a brief preliminary DC energization phase only when startup is required. This temporary high-power action positions the rotor optimally, after which normal lower-power operation with advance angle control begins. This approach achieves reliable starting without the penalty of continuously high power consumption.
3Reliability
If driving load is reduced to match lowest output torque, then starting reliability improves, but design flexibility is limited
Solution Approach 1:
The preliminary DC energization phase actively positions the rotor to overcome varying driving loads regardless of their magnitude. This means the motor can handle both light and heavy loads without requiring design compromises, maintaining full design flexibility while ensuring reliable starting across all operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for reliable motor start-up with reduced torque ripple, even under high driving loads, by strategically positioning the rotor using direct current energization, thus enhancing design flexibility and reducing power consumption.
Implementation Method 1
a first coil that is energized to thereby excite the first magnetic pole portions, a second coil that is energized to thereby excite the second magnetic pole portions
Implementation Method 2
a rotor having a magnet that has a cylindrical shape and an outer peripheral surface which is divided in a circumferential direction and is alternately multi-polar magnetized to different poles
Data Source
AI summary
A motor driving apparatus includes a motor and a control circuit that controls driving of the motor. The motor includes a rotor having a cylindrical magnet having an outer peripheral surface circumferentially divided and alternately multi-polar magnetized to different poles, a first and second yokes having first and second magnetic pole portions arranged opposed to the outer peripheral surface, a first and second coils energized to excite the first and second magnetic pole portions, respectively. Directions of energizing the first and second coils are switched based on outputs from magnetic sensors that detect a rotational position of the rotor to change excited poles of the first and second magnetic pole portions. The rotor is started from a stopped state, after performing direct current energization to move the rotor to a position dependent on the direct current energization.