Linear Motor Coil Drive Using Shared Half-Bridges for Bipolar Voltage Control
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Solution Overview
Problem
Conventional linear motor drive devices face limitations in the number of switches required, restricted voltage application, and low freedom in controlling movable elements due to the use of full-bridge or half-bridge inverter configurations, which restrict the flexibility and efficiency of voltage application.
Innovation Solution
A linear motor drive device with a configuration of half-bridges connected in series to coils, utilizing a switching controller and half-bridge output voltage calculator to apply AC voltages with positive and negative polarities, reducing the number of switches and enhancing control freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If full-bridge or half-bridge single-phase inverters are connected to the respective coils, then individual control of currents for the respective coils is realized, but the number of switches increases and the maximum voltage capable of being applied to the coil is restricted
Solution Approach 1:
Multiple half-bridge circuits are merged into a single three-phase inverter structure, where the six switches collectively control three coils. This merging reduces the total number of switches from 6-12 (in separate half-bridge configurations) to just 6 switches, while maintaining the capability to independently control current in each coil through appropriate switching sequences.
Solution Approach 2:
The three-phase inverter structure serves multiple functions simultaneously: it provides individual current control for each coil, generates both positive and negative voltage polarities, and reduces switch count. The six switches in the inverter can be configured to produce various voltage patterns across the three coils, making the system universally applicable for different control requirements.
2Device complexity
If half-bridge circuits are used with switches connected in series, then the number of switches is reduced, but the maximum value of the voltage capable of being applied to the coil is restricted to half the voltage of the DC power supply
Solution Approach 1:
The three-phase inverter dynamically switches between different configurations to overcome the voltage limitation. By selectively turning on specific switches in different time intervals, the system can apply the full DC power supply voltage (not just half) to the coils. The dynamic switching allows the output voltage to vary between +Vdc and -Vdc, effectively doubling the usable voltage range compared to a static half-bridge configuration.
3Adaptability or versatility
If DC power supply voltage is applied to the coil with positive and negative polarities, then control freedom is improved, but four switches are necessary for one coil as in a full-bridge, doubling the number of switches
Solution Approach 1:
The three-phase inverter merges the functionality of multiple full-bridge circuits into a single unified structure. Instead of requiring four switches per coil (which would total 12 switches for three coils), the inverter uses six switches shared across all three coils. The merging allows each coil to receive bipolar voltage control while reducing the total switch count by 50%.
4Extent of automation
If conventional half-bridge drive type is used substituting brush conduction, then switching control is achieved, but arbitrarily-determined voltages cannot be applied to the respective coils and degree of freedom in controlling movement is very low
Solution Approach 1:
The three-phase inverter introduces dynamic control capability that enables arbitrary voltage application to each coil. By dynamically adjusting the switching states of the six switches, the system can independently determine the voltage magnitude and polarity for each coil at any given time. This dynamic control provides high degree of freedom in controlling movable element movement, far exceeding the capabilities of conventional half-bridge drive types.
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 allows for a linear motor drive device with reduced switch count, high voltage waveform flexibility, and enhanced control over movable elements, achieving equivalent functionality with a smaller and less costly drive circuit.
Implementation Method 1
a switching controller including a half-bridge output voltage calculator... the switching controller obtains switching signals for controlling the switches of the half-bridges... and controls drive of the switches of all the half-bridges
Implementation Method 2
A linear motor is composed of: a stator on which a plurality of coils are arrayed; and movable elements disposed with gaps between the stator and the movable elements and each implemented by a permanent magnet that is moved in a direction in which the coils of the stator are arrayed
Data Source
AI summary
This linear motor drive device includes: a stator on which a plurality of coils connected in series are disposed to be arrayed; a plurality of half-bridges; and a switching controller including a half-bridge output voltage calculator. Both ends of a series unit of the coils and connection points between the coils are each connected to an output point of a different one of the half-bridges. AC voltages are applied to the respective coils. The half-bridge output voltage calculator obtains, through calculation, output voltage references for the respective half-bridges on the basis of application voltage references for voltages to be applied to the respective coils. The switching controller obtains switching signals for controlling switches of the half-bridges by using the respective half-bridge output voltage references having been obtained.