ECM Constant Torque Control via Bus Current Feedback
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Solution Overview
Problem
The existing constant torque control mode for electronically commutated motors (ECM) is complex, requiring high arithmetic capability and resulting in high costs and poor control accuracy due to multiple variables involved in vector control.
Innovation Solution
A method for acquiring constant torque in ECM using a microprocessor-controlled PWM signal to regulate coil winding, with a simplified mathematical model and closed-loop control, allowing for low CPU demand and high control accuracy by calculating and comparing target and real-time bus current values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vector control mode is used for constant torque control of ECM, then control capability is improved, but device complexity and production cost increase due to complex mathematical models and high CPU arithmetic requirements
Solution Approach 1:
The patent extracts and eliminates the complex mathematical models and multiple variables from the vector control system, replacing them with a simplified control approach that uses only bus current and rotational speed parameters. This extraction of unnecessary complexity resolves the contradiction by maintaining control capability while removing the burden of complex calculations and high CPU requirements.
Solution Approach 2:
The patent replaces expensive high-performance CPUs required for complex vector control calculations with a simpler, lower-cost microprocessor that can handle the simplified control algorithm. This substitution achieves the same control function using more economical components, directly addressing the production cost issue.
2Reliability
If vector control mode is used for constant torque control of ECM, then control capability is improved, but manufacturing cost increases due to high CPU arithmetic capability requirements
Solution Approach 1:
The patent substitutes expensive high-performance CPUs with affordable microprocessors by eliminating the need for complex mathematical computations. The simplified algorithm requiring only basic arithmetic operations on bus current and rotational speed data enables the use of low-cost hardware, directly reducing manufacturing costs while preserving essential control functionality.
Solution Approach 2:
The patent removes the computationally intensive mathematical models from the control system, extracting only the essential control parameters (bus current and rotational speed). This elimination of complex calculation requirements allows the use of budget-friendly microprocessors, thereby reducing production costs.
3Adaptability or versatility
If multiple variables are used in vector control mode, then control flexibility is improved, but control accuracy deteriorates due to increased complexity and computational errors
Solution Approach 1:
The patent extracts and removes the multiple variables from the vector control system, retaining only the two most critical parameters: bus current and rotational speed. This reduction in variable count minimizes computational errors and measurement uncertainties, thereby improving control accuracy while preserving the necessary control flexibility through the established functional relationship between these parameters.
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
This approach simplifies the mathematical model, reduces production costs, and enhances control accuracy by using a microprocessor to adjust PWM signals based on target and real-time bus current comparisons, ensuring accurate constant torque control with minimal variables.
Implementation Method 1
calculating a corresponding target bus current value Itad by the microprocessor using a function of a DC bus current Itad=F(T, rpm) according to the target torque T0 and acquired rotational speed rpm
Implementation Method 2
comparing the target bus current Itad with a real-time bus current Ibus by the microprocessor in a closed-loop control according to the detected real-time bus current Ibus
Implementation Method 3
The microprocessor outputs a pulse width modulation (PWM) signal having a certain duty ratio to control the inverter circuit
Implementation Method 4
The inverter circuit controls operation of coil winding in each phase of the stator assembly
Data Source
AI summary
A method for acquiring a constant torque of an ECM, the method including: A) acquiring a target torque value T0 input from external; B) when the motor is in a non-use state, operating the motor and acquiring an initial rotational speed rpm by the microprocessor; and when the motor is in an operating state, acquiring a current rotational speed rpm by the microprocessor; C) calculating a corresponding target bus current value Itad by the microprocessor using the function of a DC bus current Itad=F(T, rpm) according to the target torque T0 and acquired rotational speed rpm, in which T represents a torque value output by the motor; and D) comparing the target bus current Itad with a real-time bus current Ibus by the microprocessor in a closed-loop control according to the detected real-time bus current Ibus.