Multi-Motor Actuator for Joint Extension
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Solution Overview
Problem
Conventional Continuously Variable Transmissions (CVTs) in actuator systems are inefficient and mechanically complex, limiting their ability to provide larger forces at slower speeds and smaller forces at higher speeds, while also requiring additional components and complexity.
Innovation Solution
A multi-motor assembly with two brushless electric motors and transmissions that define different gear ratios, allowing the system to supply larger forces at slower speeds and smaller forces at higher speeds, along with a rotary-to-linear mechanism and a controller that operates in various modes to optimize force and speed profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor is used to provide motion for each output direction, then the device complexity is reduced, but the speed/torque range is limited
Solution Approach 1:
The system divides the motor function into two separate brushless electric motors, each responsible for different speed/torque ranges. The first motor subsystem handles high-speed/low-torque operations while the second motor subsystem handles low-speed/high-torque operations, eliminating the need for complex gear systems while expanding the overall speed/torque range
Solution Approach 2:
Both motor subsystems connect to the same drive shaft and can operate independently or together, allowing the system to universally handle various operational requirements across different speed and torque conditions without requiring separate mechanisms for each function
2Adaptability or versatility
If conventional CVTs are used to change gear ratios, then the speed/torque range is improved, but the mechanical complexity and efficiency deteriorate
Solution Approach 1:
The patent replaces the conventional mechanical CVT system with two electric motor subsystems that electronically control speed and torque. This substitution eliminates complex mechanical components like variable diameter gears, conical pulleys, and belts, while achieving the same speed/torque variability through electronic motor control
Solution Approach 2:
Instead of physically changing gear ratios through mechanical means, the system changes operational parameters by selectively activating different motor subsystems based on the required speed and torque conditions, achieving continuous variability through parameter selection rather than mechanical transformation
3Adaptability or versatility
If conventional CVTs are used to change gear ratios, then the speed/torque range is improved, but the efficiency deteriorates
Solution Approach 1:
By replacing the mechanical CVT with electric motor subsystems, the system eliminates energy losses associated with mechanical friction, belt slippage, and gear meshing. Electric motors directly convert electrical energy to mechanical motion with higher efficiency across the entire speed/torque range
4Device complexity
If a single motor is used, then the device complexity is reduced, but the ability to supply larger forces at slower speeds deteriorates
Solution Approach 1:
The system segments the force delivery function by assigning the second motor subsystem specifically for high-force, low-speed operations. This motor can be optimized with higher torque characteristics and direct connection to the drive shaft, eliminating the need for complex gear reduction systems while delivering superior force at slower speeds
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 system effectively provides a wide range of forces and speeds without the need for complex gear systems, enhancing efficiency and reducing mechanical complexity, while allowing for free movement of joints in applications like robotics and orthotics.
Implementation Method 1
two brushless electric motors and transmissions that define different gear ratios
Data Source
AI summary
An actuator system for assisting extension of a biological joint is provided with a motor assembly, a rotary-to-linear mechanism, and an extension stop. The rotary-to-linear mechanism includes a screw that accepts rotational output of the motor assembly, and a nut that cooperates with the screw to convert rotational movement of the screw to linear movement of the nut. The extension stop is driven by linear movement of the nut in an extension direction to cause extension of the biological joint. The motor assembly, the rotary-to-linear mechanism and the extension stop cooperate to allow unpowered flexion of the joint. The system is configured without a flexion stop, and is configured such that the nut cannot drive the joint in a flexion direction. Methods of use are also disclosed.