Stepping Motor Drive Device for Laboratory Liquid Handling
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Solution Overview
Problem
Conventional liquid handling devices face issues with temperature-related waste heat generation and bubble formation in the system liquid, leading to reduced accuracy and lifespan due to high holding currents in motorized diluters.
Innovation Solution
A drive device utilizing a two-phase AC-operated stepping motor with a motor controller that dynamically regulates speed and acceleration, featuring phase terminals for current measurement and transformation modules to decompose motor currents into slip and torque components, minimizing holding currents and optimizing motor operation for reduced heat generation and improved dynamic response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high holding currents are used in motorized diluters to ensure precise positioning, then positioning accuracy is improved, but temperature-related waste heat generation increases
Solution Approach 1:
The motor controller applies periodic pulsed currents instead of continuous holding currents. The motor is activated only during movement phases and deactivated during stationary phases, eliminating continuous heat generation while maintaining positioning accuracy through precise timing and periodic reactivation when needed.
Solution Approach 2:
The system dynamically changes current parameters by switching between active movement modes and idle states. During idle periods, holding currents are reduced to zero, and during movement, current magnitude and duration are optimized for the specific task, reducing overall heat generation while maintaining precision when active.
2Measurement precision
If high holding currents are maintained to ensure precise positioning, then positioning accuracy is improved, but motor lifespan is reduced
Solution Approach 1:
The motor controller implements periodic activation where the motor runs only during necessary movement operations and remains deactivated during idle periods. This reduces cumulative operating hours and thermal stress on motor components, extending lifespan while maintaining positioning accuracy during active use.
Solution Approach 2:
The system converts the potential harm of continuous operation into benefit by using idle periods for cooling and rest. The motor benefits from periodic rest intervals that allow temperature reduction and stress relief, extending component life while maintaining precision performance when activated.
3Measurement precision
If the motor operates continuously with high holding currents, then positioning accuracy is maintained, but heat generation leads to bubble formation in system liquid
Solution Approach 1:
The motor controller uses periodic activation patterns that keep the motor deactivated during idle periods, preventing continuous heat generation that would outgas the system liquid. The motor is only activated when positioning changes are required, maintaining precision while avoiding bubble formation through reduced thermal stress on the liquid system.
4Speed
If high power is consumed to ensure dynamic response, then speed control is improved, but power consumption increases
Solution Approach 1:
The motor controller dynamically adjusts power delivery based on real-time positioning requirements. During movement phases, high power is applied for rapid positioning, but during idle phases, power is reduced to zero. This dynamic adaptation maintains excellent speed control and response when needed while minimizing overall power consumption during stationary periods.
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
The solution achieves precise control and reduced power consumption, enabling efficient, contact-free dispensing of small liquid volumes with enhanced accuracy and extended motor lifespan, while minimizing heat-related issues and bubble formation.
Implementation Method 1
A drive device is proposed which comprises an AC-operated motor, preferably a two-phase AC-operated stepping motor, having rotor and stator
Implementation Method 2
The motor controller comprises a transformation module, in order to decompose the currently flowing motor phase currents into a slip component and a torque component using a transformation method
Implementation Method 3
Water, preferably deionized water, in the pipette tip, line, and syringe, is used in liquid handling devices as a rigid movement mediator of the movement of the syringe piston to the pipette tip
Implementation Method 4
However, if gas bubbles occur in the system liquid, e.g., due to the outgassing of air, every gas bubble acts as a small spring
Implementation Method 5
Temperatures of greater than 50° C. have been measured on freestanding diluters. If multiple such diluters are installed adjacent to one another in a liquid handling device, still higher temperatures can even occur
Data Source
AI summary
The invention relates to a drive device (100) for use in a laboratory device, having a stepping motor (10) having rotor and stator, and having a motor controller (20), which is designed for the purpose of activating the stepping motor (10). In one embodiment, the drive device (100) comprises an encoder (11), which supplies a respective current encoder signal (e(t)) in operation (ia, ib), which reflects the current rotor position of the rotor, and phase terminals (14, 27), to tap the currently flowing motor phase currents (ia, ib). The motor controller (20) comprises a transformation module (13), in order to decompose the currently flowing motor phase currents (ia, ib) using a transformation method into a slip component (ix) and a torque component (iy). Furthermore, it comprises a slip regulation module (15), to which the slip component (ix) and a first target value (ix*) are supplied as input variables, and a torque regulation module (16), to which the torque component (iy) and a second target value (iy*) are supplied as input variables. The slip regulation module (15) and the torque regulation module (16) predefine the rotor phase currents (ia, ib) so that the difference between the slip component (ix) and the first target value (ix*) and the difference between the torque component (iy) and the second target value (iy*) are minimal.