Brushless Drive Rotor Positioning via Voltage Pulse Inductance
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Solution Overview
Problem
Existing brushless electric drives face challenges in reliably determining the position of the rotor, especially at low speeds and when stationary, due to the cost and susceptibility of Hall sensors and the unreliability of electromotive force (EMF) methods, which can be interfered with by pulse width modulated signals and result in torque ripples.
Innovation Solution
A method involving the application of voltage pulses between terminals of phase windings to determine the voltage division ratio, which is used to infer the relative position of the rotor based on the ratio of variable inductances, allowing for precise position determination even at low speeds with minimal interference and low design complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Hall sensors are used to determine rotor position, then position determination reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical Hall sensors with an electrical measurement method that uses voltage pulses and current measurements in the phase windings to determine rotor position. This substitution eliminates the need for additional mechanical sensing components while maintaining position determination capability through electrical measurements of the existing motor windings.
Solution Approach 2:
The patent utilizes the motor's own phase windings and electrical characteristics to determine rotor position, rather than requiring separate sensing components. By measuring voltage division ratios and current characteristics in the existing motor structure, the system makes the motor self-diagnostic for position sensing, reducing external component requirements.
2Device complexity
If electromotive force (EMF) methods are used for position determination, then device complexity is reduced, but measurement precision deteriorates at low speeds
Solution Approach 1:
The patent employs periodic voltage pulse applications to the phase windings at controlled intervals. By applying measurement voltage pulses periodically and measuring the resulting current responses, the system achieves reliable position determination even at low speeds where continuous EMF signals are insufficient. The periodic measurement approach ensures adequate signal strength for accurate detection.
Solution Approach 2:
The patent changes the measurement parameter from continuous voltage monitoring to discrete voltage pulse application with current measurement. By applying controlled voltage pulses and measuring the resulting current characteristics and voltage division ratios, the system achieves improved measurement precision across all speed ranges, particularly at low speeds where traditional EMF methods fail.
3Measurement precision
If measurement pulses are used to determine current-induced voltage, then position determination is achieved, but torque ripples increase due to interference
Solution Approach 1:
The patent applies voltage pulses of controlled duration and amplitude to the phase windings for measurement purposes. By using partial action (intermittent pulses rather than continuous signals) and carefully controlling the pulse characteristics, the system achieves sufficient measurement data while minimizing the disturbance to the motor's normal operation and reducing torque ripple generation.
Solution Approach 2:
The patent performs position measurements at strategically chosen moments in the motor operation cycle, before critical torque production phases. By timing the voltage pulse applications and current measurements to occur during periods of lower torque demand or predictable motor states, the system minimizes interference with the motor's primary function and reduces harmful torque ripples.
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 enables reliable position determination with high sensitivity and spatial resolution, minimizing torque ripples and avoiding the limitations of existing methods, particularly at low speeds and standstill conditions.
Implementation Method 1
A voltage pulse is applied between a first terminal of the first phase winding and a second terminal of the second phase winding. The voltage prevailing at the connecting point or at a third phase winding connected thereto is detected and based on this, the voltage division ratio between the first phase winding and the second phase winding is determined
Data Source
AI summary
A method for determining the position of an at least two-phase, in particular three-phase bmshless electric drive comprising at least two phase windings, each of which has a first and a second terminal, a second terminal of a first phase winding being electrically connected to the first terminal of a second phase winding at a common connecting terminal. In order to be able to reliably determine the position of the electric drive even at low speeds, a voltage pulse is applied between the first terminal of the first phase winding and the second terminal of the second phase winding, the resulting voltage at the connecting terminal or at a third phase winding connected thereto is detected and the voltage ratio between the first phase winding and the second phase winding is determined therefrom, and the ratio between the variable inductances is determined from said voltage ratio.