Servomotor Control via Voltage Space Vector Characteristic Diagrams
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Solution Overview
Problem
Electronically commutated DC motors in actuator applications face inefficiencies and torque reductions due to inaccuracies in rotor position detection and current measurement, leading to potential emergency shutdowns from exceeding current limits, especially in throttle valve actuators where precise control is critical.
Innovation Solution
A method and device for operating an electronically commutated servomotor using a voltage space vector generated based on a commutation pattern, with a control range that ensures only permissible voltage space vectors are used, and a characteristic diagram that specifies voltage space vectors as a function of torque and rotor position, allowing for robust control and preventing excessive motor currents even with inaccuracies in rotor position detection and parameter deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rotor position is detected indirectly via gear reduction, then cost is reduced and device complexity is lowered, but measurement precision deteriorates with uncertainties exceeding 10 degrees
Solution Approach 1:
The patent changes the control parameters by using predefined characteristic diagrams that map torque and rotor position to optimal voltage space vectors. This approach compensates for the imprecise rotor position detection by providing pre-calculated control parameters that maintain reliable operation despite measurement uncertainties exceeding 10 degrees.
Solution Approach 2:
The patent applies preliminary action by pre-defining characteristic diagrams that specify the optimal voltage space vectors for various combinations of torque and rotor position. These pre-calculated control parameters are stored and directly applied during operation, eliminating the need for real-time optimization calculations and current sensor feedback.
2Device complexity
If current sensor system is removed to reduce cost, then device complexity and cost are reduced, but reliability deteriorates due to inability to regulate motor current
Solution Approach 1:
The patent implements self-service by designing a control system that does not require external current sensors to regulate motor current. The predefined characteristic diagrams inherently limit the voltage space vectors to those that will not cause current exceeds, making the system self-regulating regarding current limits without needing additional sensing hardware.
Solution Approach 2:
The control ranges in the predefined characteristic diagrams are pre-calculated to ensure that only voltage space vectors leading to acceptable motor currents are included. This preliminary configuration of safe operating parameters eliminates the need for real-time current measurement while maintaining reliability.
3Productivity
If commutation is controlled based on detected rotor position, then productivity and response speed are improved, but reliability worsens due to current limit violations from position uncertainties
Solution Approach 1:
The patent uses predefined characteristic diagrams that are pre-calculated offline to determine the optimal voltage space vectors for various operating conditions. During real-time operation, the controller simply looks up the appropriate control parameters from these pre-defined diagrams based on the detected rotor position and torque demand, achieving fast response without risking current limit violations.
Solution Approach 2:
The control ranges in the characteristic diagrams are designed with safety margins to cushion against rotor position detection uncertainties. By pre-defining these conservative control ranges, the system ensures that even with position measurement errors exceeding 10 degrees, the motor current will not exceed safe limits, preventing emergency shutdowns.
Data Source
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AI summary
The invention relates to a method for operating an electronically commutated servo motor (2), wherein the servo motor (2) is activated by a voltage space vector generated in accordance with a commutation pattern on the basis of a predefined torque and a rotor position (L) of a rotor of the servo motor (2) in accordance with an optimization target, wherein an activation range which indicates a range of permissible voltage space vectors is predefined, wherein the servo motor (2) is activated in such a way that only voltage space vectors within the activation range are used.