Motor Control Device Speed-Based Q-Axis Voltage Generation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional motor control devices face challenges in achieving precise rotation control at lower speeds and lower torques, particularly in no-load conditions, where current detection precision is compromised, leading to increased power consumption and efficiency losses.
Innovation Solution
A motor control device and method that generate a q-axis voltage instruction based on speed deviation, rather than q-axis current, to maintain precise control without relying on minute q-axis currents, thereby stabilizing rotation control in no-load, lower speed conditions and minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional vector control is used in lower torque, lower speed condition, then the motor control system can operate at low speeds, but current detection precision deteriorates leading to increased power consumption
Solution Approach 1:
The invention changes the control parameter from current-based to speed-based for generating q-axis voltage instruction. Instead of using q-axis current (which becomes undetectable at low speeds), the system uses speed deviation from a speed instruction value to generate the voltage instruction through PI computation, thereby maintaining control precision across all speed ranges
Solution Approach 2:
The invention substitutes the electrical measurement system (current detection) with a mechanical/kinematic measurement system (speed detection). By using speed deviation as the basis for control instead of current detection, the system avoids the fundamental limitation of current sensor precision at low torque conditions
2Measurement precision
If offset angle adjustment is applied to improve current detection precision, then measurement precision improves, but device complexity increases
Solution Approach 1:
The invention extracts the speed control function from the current control framework. By separating the q-axis voltage generation into an independent speed-based control loop, the system eliminates the need for complex offset angle adjustments and current signal processing, simplifying the overall control architecture
Solution Approach 2:
Instead of adjusting the current detection system to work at low speeds (offset angle adjustment), the invention inverts the approach by using speed information to generate voltage instructions directly. This reverse engineering approach simplifies the control system by avoiding complex signal processing
3Manufacturing precision
If q-axis current is used for voltage instruction generation, then control precision is maintained at normal load, but control stability deteriorates in no-load conditions
Solution Approach 1:
The invention introduces dynamic adaptability by using speed deviation as the control input. The system automatically adjusts the voltage instruction based on the difference between actual and target speed, maintaining stable control across varying load conditions without requiring manual intervention or complex switching logic
Data Source
AI summary
In a motor control device, a two-phase/three-phase converter is configured to convert a d-axis voltage instruction and a q-axis voltage instruction into voltage instructions in UVW phases. A PWM circuit is configured to generate drive pulse signals having undergone power width modulation, in accordance with the voltage instructions. An inverter is configured to generate drive voltages for driving coils based on the drive pulse signals. A position detector is configured to detect a rotational position. A rotational speed calculator is configured to calculate a rotational speed. A current detector is configured to detect drive currents flowing into the coils. A three-phase/two-phase converter is configured to convert detected drive current values into a d-axis current value and a q-axis current value. A d-axis voltage instruction generation unit is configured to acquire a difference between the d-axis current value and a d-axis current instruction having a predetermined value, and to generate the d-axis voltage instruction based on PI computation performed on the difference. A q-axis voltage instruction generation unit is configured to acquire a difference between a speed instruction and the rotational speed calculated by a rotational speed calculation unit, and to generate the q-axis voltage instruction based on PI computation performed on the difference.