Nested Electric Motor System for Compact High Power Density Propulsion
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Solution Overview
Problem
Existing propulsion systems with multiple independent shafts face challenges in reducing dimensions while maintaining high power density, particularly in compact spaces, as they often require bulky motor arrangements and complex drive mechanisms, limiting their installation in small spaces and increasing weight and consumption.
Innovation Solution
A compact electric propulsion system with two electric motors, one featuring an internal stator and external rotor, and the other with an external stator and internal rotor, locked by a flange fixing system, allowing independent control and reduced volume occupation, thereby enhancing power density and reducing weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If two or more independent electric motors with external stators are arranged one next to the other, then each shaft can be controlled independently, but the propulsion system occupies a large space and has low power density
Solution Approach 1:
The patent applies nesting by placing one motor inside another motor. Specifically, a first motor with an external rotor and internal stator houses a second motor with an internal rotor and external stator within its hollow space. This nested configuration allows two independent motors to occupy the volume of a single motor, dramatically reducing the overall space occupied by the propulsion system while maintaining independent control of multiple shafts
Solution Approach 2:
The patent transitions from a planar arrangement where motors are placed side-by-side to a three-dimensional nested arrangement. By utilizing the hollow space within the first motor to accommodate the second motor, the design exploits the third dimension (radial depth) rather than only lateral spacing, thereby reducing the footprint and overall volume of the propulsion system
2Volume of moving object
If the space occupied by each motor is reduced, then the propulsion system becomes more compact, but the power delivered by each motor decreases
Solution Approach 1:
The nested motor configuration allows two motors to share the same external envelope volume. The first motor provides power through its external rotor, while the second motor provides additional power through its internal rotor. The combined power output of both motors exceeds what a single motor of the same external dimensions could deliver, thereby increasing power density (power per unit volume) of the propulsion system
Solution Approach 2:
The patent merges two independent motor units into a single integrated propulsion system. The hollow space of the first motor is utilized to accommodate the second motor, effectively combining their volume efficiencies. This merging allows the propulsion system to deliver the sum of both motors' power within the volume of approximately one motor, thereby increasing overall power density
3Volume of moving object
If motors are arranged compactly, then the propulsion system fits in small spaces, but the fixing system becomes more complex
Solution Approach 1:
The nested arrangement inherently simplifies the fixing system compared to alternative compact configurations. The inner motor is positioned within the hollow space of the outer motor, and both are secured using a straightforward flange-based fixing system. This eliminates the need for complex multi-point mounting arrangements that would be required if motors were packed closely in traditional side-by-side or stacked configurations
Solution Approach 2:
The flange fixing system serves multiple functions: it secures the inner motor within the outer motor's hollow space, provides structural support for both motors, and enables easy assembly and disassembly. This multi-functional fixing approach reduces overall system complexity compared to specialized mounting solutions that would be needed for non-nested compact arrangements
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 enables a high power density propulsion system with reduced dimensions, facilitating independent control of multiple shafts, reduced weight, and simplified installation, suitable for applications like robotics where space is limited, while maintaining high drive power and efficiency.
Implementation Method 1
each one comprising a stator (S1, S2) and a rotor (R1, R2)... two or more independent motors are provided, preferably a motor for each shaft
Data Source
AI summary
Electric propulsion system with at least two shafts, comprising at least two electric motors, of which at least one first motor 3 and at least one second motor 4, each one comprising a stator "S" and a rotor "R". Said propulsion system comprises, furthermore, a fixing system 5, adapted to lock the stators "S" of said motors to one another. Said first motor 3 is a motor in which the stator "S" is arranged in an inner position with respect to the rotor "R", which is arranged on the outside of said stator "SH, and the second motor 4 is a motor in which the stator "S" is arranged in an outer position with respect to the rotor "R", which is arranged on the inside of said stator "S".