Motor Drive Control Phase Adjustment for Torque Accuracy
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Solution Overview
Problem
Existing motor drive control systems using square wave voltage for AC motors face challenges in achieving maximum torque output due to lower control accuracy and potential energy inefficiencies, particularly in conditions where feedback control for phase adjustment is insufficient.
Innovation Solution
A motor drive control apparatus and method that includes an inverter, rotational position detector, error acquisition module, limit phase setting module, and target voltage phase setting module to correct and set the phase of square wave voltage, ensuring the AC motor outputs a target torque by accounting for detection errors and adjusting the phase range to maximize output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If square wave voltage control is applied to the AC motor, then energy efficiency is improved and copper loss is reduced, but control accuracy deteriorates and torque output cannot reach maximum expected value
Solution Approach 1:
The patent changes the control parameter from simple square wave voltage application to phase-adjusted square wave voltage. By dynamically adjusting the voltage phase based on detected torque differences, the system maintains the energy efficiency benefits of square wave control while achieving higher control accuracy and maximum torque output.
Solution Approach 2:
The patent implements feedback control by detecting the actual torque output of the motor and comparing it with the commanded torque. The detected torque difference is used to adjust the phase of the square wave voltage, creating a closed-loop control system that ensures maximum torque output while maintaining energy efficiency.
2Reliability
If feedback control is used to adjust the phase of square wave voltage, then torque control is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical torque measurement systems with electrical detection methods. By calculating torque based on motor current and rotational position measurements, the system achieves reliable torque control without adding mechanical complexity to the physical system.
Solution Approach 2:
The patent makes the existing rotational position sensor serve multiple functions: it provides both position information for basic control and torque estimation for feedback control. This multi-functional use reduces the need for additional sensors or measurement devices, thereby limiting the increase in system complexity.
3Productivity
If rotational position detection is used for square wave control, then switching timing is improved, but detection errors cause phase inaccuracies
Solution Approach 1:
The patent performs preliminary torque estimation based on rotational position detection before applying the square wave voltage. By pre-calculating the expected torque and comparing it with the commanded torque, the system can anticipate and compensate for detection errors, maintaining accurate switching timing despite measurement imperfections.
Solution Approach 2:
The patent changes the control approach from relying solely on precise rotational position detection to using torque difference-based phase adjustment. This parameter change allows the system to tolerate detection errors by continuously adapting the voltage phase based on actual torque feedback rather than relying on perfect position measurement.
Data Source
AI summary
In application of a square wave voltage to a motor MG2 to make the motor MG2 output a torque equivalent to a torque command Tm2*, the procedure of square wave control corrects reference phases ψb and −ψb as phases for maximizing an absolute value of the output torque of the motor MG2 with a rotational position detection error θerr and sets the results of the correction to an upper limit phase ψul and a lower limit phase ψll of the square wave voltage (step S110). A target voltage phase ψ* is set within a phase range defined by the upper limit phase ψul and the lower limit phase ψll, in order to reduce a torque difference between the torque command Tm2* and a torque estimate Tm2est (steps S120 and S130). An inverter 42 is controlled based on the target voltage phase ψ* and a rotational angle θ of the motor MG2.