Shared-Leg VSI Topology for Compact Multi-Motor High-Speed Drive
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Solution Overview
Problem
Existing voltage source inverter (VSI) circuits for electric motors are bulky and costly, particularly in miniaturized robotics applications, and sharing a single VSI leg among multiple motors limits their maximum speed due to cumulative back-EMF effects.
Innovation Solution
A system with a voltage source inverter circuit that includes multiple inverter legs, where some legs are shared to drive phases of multiple motors, using a commutation control circuit to transform and modulate voltage signals, ensuring positive phase voltages and reducing the number of required VSI legs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single VSI leg is shared among multiple motors to reduce circuit size, then the physical size and cost of the VSI circuit is reduced, but the maximum speed of the motors is limited due to cumulative back-EMF effects
Solution Approach 1:
The patent segments the VSI legs into shared and dedicated portions, where the shared leg serves multiple motors but dedicated legs are allocated to specific motor groups. This segmentation allows the system to achieve size reduction through sharing while maintaining sufficient voltage headroom through dedicated resources, thereby resolving the contradiction between compact size and speed performance.
Solution Approach 2:
The shared VSI leg is designed to serve multiple motors simultaneously, making it a multi-functional component. This universality reduces the total number of VSI legs required, shrinking circuit size while the control algorithm manages the distribution of voltage resources to maintain motor speed performance across different operating conditions.
2Speed
If multiple VSI legs are used to drive multiple motors, then motor speed performance is maintained, but the physical size and cost of the VSI circuit increases
Solution Approach 1:
The system segments motors into groups, each served by dedicated VSI legs, while implementing shared legs for common phases. This segmentation strategy maintains voltage headroom for high-speed operation in critical motor groups while reducing overall circuit size through shared infrastructure, balancing performance and compactness.
Solution Approach 2:
Different motors or motor groups are assigned different VSI leg configurations based on their specific performance requirements. Motors requiring high speed are connected to dedicated legs with sufficient voltage headroom, while less critical motors share legs, creating local quality variations that optimize the overall system for both performance and size.
3Volume of moving object
If VSI legs are shared among motors, then cost and size are reduced, but the complexity of voltage modulation and commutation control increases
Solution Approach 1:
The control algorithm acts as an intermediary that manages the complex voltage distribution among shared and dedicated legs. It transforms the complexity of coordinating multiple shared connections into a manageable computation task, resolving the contradiction by moving the complexity from the hardware level to the software/control level.
Solution Approach 2:
The system dynamically adjusts voltage modulation parameters based on the operational state of shared motors. By changing parameters such as duty cycle, switching frequency, and voltage distribution ratios in real-time, the control algorithm manages the complexity of shared leg coordination while maintaining efficient motor operation and reducing the need for overly complex fixed hardware designs.
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 provides a compact VSI circuit that maintains motor performance without the speed limitations of traditional shared-leg systems, optimizing size and cost in applications like miniaturized robotics.
Implementation Method 1
Most commonly, this output voltage is achieved via sinusoidal pulse-width modulation, although space-vector modulation is also common.
Implementation Method 2
A motor spins due to the interaction of the electromagnetic field of the rotor and the field created by current flowing through the stator windings.
Implementation Method 3
Rotor position usually is determined using either hall-effect sensors or a position sensor such as a digital encoder.
Implementation Method 4
In more cost sensitive applications, rotor position may be estimated by sensing a voltage due to back-electro-motive force (back-EMF).
Data Source
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AI summary
A system is provided that includes multiple motors, each respective motor comprising three phases; a voltage source inverter circuit comprising multiple respective inverter legs; each respective inverter leg coupled to drive at least one phase of at least one of the respective of the respective motors; wherein a first shared inverter leg is coupled to drive a first phase of a first motor and drive third phase of a second motor; and wherein a second shared inverter leg is coupled to drive a third phase of the second motor and a first phase of a third motor.