Stepper Motor Torque Monitoring for Sensorless Pump Malfunction Detection
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Solution Overview
Problem
Existing displacement pumps using stepper motors face challenges in detecting malfunctions without additional sensors, leading to potential dosing accuracy issues and increased complexity and cost due to the need for additional sensors to monitor load and pressure.
Innovation Solution
A method to determine the engine torque provided by the stepper motor and output a warning signal when it meets a predetermined criterion, allowing for sensorless detection of overload conditions and potential malfunctions, without the use of additional sensors inside the pump or dosing head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional sensors are installed to monitor load and pressure for malfunction detection, then measurement precision and reliability improve, but device complexity and cost increase
Solution Approach 1:
The stepper motor's own electrical parameters (current, voltage, phase shift) are utilized to detect malfunctions. The motor serves itself by providing the measurement signals needed for monitoring, eliminating the need for external sensors. The control unit calculates torque and detects overloads by evaluating the motor's inherent electrical characteristics during operation.
Solution Approach 2:
The patent replaces mechanical/electrical sensors with an electrical field-based measurement approach. Instead of using physical sensors to detect torque and pressure, the system uses electrical parameter analysis (current, voltage, phase shift calculations) to infer mechanical load conditions and detect malfunctions non-contactually.
2Measurement precision
If additional sensors are installed inside the pump or dosing head to monitor operational status, then measurement precision improves, but ease of manufacture deteriorates due to increased complexity and cost
Solution Approach 1:
The monitoring function is extracted from the mechanical pump structure and relocated to the electrical control domain. Instead of embedding sensors within the pump or dosing head, the system extracts operational information through electrical parameter measurement of the stepper motor, simplifying mechanical assembly while maintaining monitoring capability.
Solution Approach 2:
The control unit acts as an intermediary that translates electrical parameters (current, voltage, phase shift) into operational status information. This intermediary approach allows indirect monitoring of mechanical conditions through electrical measurements, avoiding the need for direct mechanical sensing within the pump structure.
3Productivity
If the stepper motor operates under high load to maintain dosing performance, then productivity is maintained, but reliability decreases due to potential step loss and motor standstill
Solution Approach 1:
The system implements continuous feedback monitoring of the stepper motor's electrical parameters during operation. By calculating torque from current and voltage measurements and monitoring phase shifts, the system detects approaching overload conditions in real-time, allowing preventive action before step loss occurs, thus maintaining both productivity and reliability.
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
Enables precise monitoring of the pump's operational status, including detection of malfunctions and potential leaks, without additional sensors, thereby maintaining dosing accuracy and reducing system complexity and cost.
Implementation Method 1
The rotor can be rotated through a minimum angle or step or multiples thereof by a controlled, stepwise rotating electromagnetic field of a plurality of stator coils
Implementation Method 2
stepping motors in the form of linear motors are also known in which a gradual translational movement of a movable motor part between two extreme positions is directly generated by means of electromagnetic force generation
Implementation Method 3
The movement of the rotor in the electromagnetic field of the stator coils causes a counter-induced voltage, the so-called back EMF, in these coils
Implementation Method 4
This rotational movement is translated into a translational movement by means of a push rod or connecting rod or the like for the alternating back and forth movement of the displacement element
Data Source
Figure 1
AI summary
The present invention relates to a method for the sensorless detection of malfunctions of a positive displacement pump (1), wherein the positive displacement pump (1) has a movable displacement element (5) with an interface (AG) which defines a metering chamber (3), wherein the metering chamber (3) is connected via valves (8, 9) to a suction and pressure line (6, 7), so that by an oscillating movement of the displacement element (5) conveying fluid (F) can be alternately drawn into the metering chamber (3) via the suction line (6) and pushed out of the metering chamber (3) via the pressure line (7), and wherein a stepper motor (13) is provided as a drive for the oscillating movement of the displacement element (5).To provide a method for detecting malfunctions of a positive displacement pump without requiring additional sensors, it is proposed according to the invention that a motor torque (MM) provided by the stepper motor (13) is determined and, if the determined motor torque (MM) meets a first predetermined criterion, a warning signal is issued.