Multi-Wire Surgical Motor Coil Assembly for Higher Torque Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hand-held surgical instruments face challenges in achieving increased power output and torque while minimizing weight, size, current loss, and heat generation, due to the interrelated parameters of power, size, and heat production in traditional motor designs.
Innovation Solution
The development of a brushless sensorless DC motor with multiple phase sets and a high fill factor coil assembly, featuring multiple coils per phase set and a specific wire configuration that maximizes conductive material within a given volume, reduces Eddy current losses and coil resistances, and eliminates the need for central and distal support members, thereby enhancing power and torque output without increasing motor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power output of a motor is increased, then the power and torque output are improved, but the heat generated by the motor increases
Solution Approach 1:
The patent changes the electrical parameters of the motor by increasing the number of wires per phase set from the conventional three to five or more wires. This parameter change allows for reduced current per wire while maintaining or increasing total power output, thereby reducing I²R losses and heat generation. The modified coil assembly with increased wire count fundamentally alters the electrical characteristics to achieve higher efficiency
Solution Approach 2:
The patent employs a composite coil assembly structure combining multiple wires of different gauges or materials within each phase set. This composite approach allows optimization of current distribution and resistance characteristics, enabling higher power output with reduced thermal losses through synergistic material properties
2Volume of moving object
If the size of a motor is decreased, then the compactness is improved, but the power output of the motor typically decreases
Solution Approach 1:
The patent implements a nested configuration where multiple wires are bundled and positioned within the available coil space in a hierarchical manner. The five-or-more-wire phase sets are nested within the stator cavity, with wires of different diameters arranged concentrically or in tight bundles, maximizing the use of available volume to pack more conductive material without increasing external dimensions
Solution Approach 2:
The patent transitions from a conventional two-dimensional coil winding approach to a multi-dimensional wire arrangement within the phase set. By utilizing spatial optimization in three dimensions and arranging wires in complex patterns (including radial, axial, and circumferential orientations), the design packs more conductive material into the same volume, increasing power density without expanding motor size
3Quantity of substance
If the number of wires per phase set is increased, then the fill factor is improved, but the device complexity increases
Solution Approach 1:
The patent segments the coil assembly into distinct phase sets, with each phase set containing five or more individually positioned wires. This segmentation allows for modular manufacturing and assembly, where each wire can be independently positioned and connected, simplifying the overall construction process despite the increased number of components. The segmentation also facilitates heat dissipation by creating thermal pathways between individual wires
Solution Approach 2:
The patent introduces intermediary structures such as wire formers, positioning fixtures, and automated winding mechanisms that facilitate the precise arrangement of multiple wires per phase set. These intermediary tools and fixtures mediate between the raw wire material and the final coil configuration, enabling complex multi-wire arrangements to be manufactured efficiently with standard equipment, thereby reducing the practical complexity despite increased fill factor
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 results in a motor with increased power and torque output, reduced current losses, and minimized heat generation, while maintaining a compact size, thus addressing the limitations of traditional surgical instrument motors.
Implementation Method 1
Electrical current is supplied to the coils, which causes the rotor to rotate relative to the stator due to interactions between (i) magnetic fields generated by the coils and (ii) a magnetic field produced by the magnetic structure of the rotor
Implementation Method 2
PWM losses are attributable to Eddy currents in a magnetic structure caused by the current supply. Eddy currents are a phenomena caused by a variation of a magnetic field through an electrically conductive medium
Data Source
AI summary
A motor for a surgical instrument includes a rotor and a stator. The rotor includes a shaft and a magnet. The stator includes (i) a cavity in which the rotor is disposed, and (ii) a coil assembly. The coil assembly includes multiple phase sets. The phase sets include multiple sets of wires. Each of the phase sets includes multiple coils and corresponds to a respective one of the sets of wires. The coils in each of the phase sets are at respective positions about the rotor. One of the sets of wires includes at least three wires. The stator causes the rotor to axially rotate a surgical tool of the surgical instrument based on current received at the sets of wires.