Robot Joint Assembly With Strain Wave Gearing and Rotor Brake
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Solution Overview
Problem
Existing robotic joint assemblies face challenges in minimizing dynamic forces, which can lead to hazardous situations when robots interact with humans, particularly due to increased torque and precision issues when handling loads close to the arm's fixation point, and there is a need for a compact and reliable design that reduces the risk of accidents.
Innovation Solution
A joint assembly featuring a strain wave gearing system with a wave generator, flexspline, and circular spline, integrated with a rotor brake and sensors to measure position, along with a compact design that shields magnetic fields and reduces inertia, and an output brake system for safe operation, including a planetary gear for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the joint assembly is made compact to minimize dynamic forces, then the dynamic forces acting on the robotic system are reduced, but the device complexity increases due to integration of multiple components
Solution Approach 1:
The patent integrates the rotor brake, sensors, strain wave gearing system, and motor into a single compact joint assembly housing. Multiple functional components that could be separate are merged into one integrated unit, reducing the overall footprint and minimizing dynamic forces while maintaining all necessary functions.
Solution Approach 2:
The design places the motor and strain wave gearing system concentrically around the rotor shaft, with components nested within each other. The flexspline envelops the motor, and the wave generator is positioned centrally, creating a nested configuration that maximizes space utilization and compactness.
2Force
If the joint assembly is made lighter to reduce dynamic forces, then the inertial effects are minimized, but the strength and reliability may be compromised
Solution Approach 1:
The patent employs a rotor brake comprising a non-ferromagnetic pusher part and a ferromagnetic brake ring, utilizing different material properties for optimal performance. The strain wave gearing system uses specialized materials for the flexspline and circular spline to achieve both light weight and high strength.
Solution Approach 2:
The strain wave gearing system uses curved, flexible splines (flexspline and circular spline) instead of rigid straight gears. This curved geometry allows for compact design while distributing stresses more evenly, maintaining strength and reliability in a lighter configuration.
3Measurement precision
If sensors are added to measure rotor shaft position for enhanced precision, then the position measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The strain wave gearing system serves multiple functions: it provides mechanical advantage for torque multiplication, enables compact design, and simultaneously serves as the measurement interface for the sensors. The same structural components that transmit motion also provide the geometric relationship needed for precise position measurement, eliminating the need for separate measurement mechanisms.
4Productivity
If the robot operates at higher speeds for increased productivity, then the production output is improved, but the dynamic forces and safety risks increase
Solution Approach 1:
The rotor brake is configured to automatically engage and stop the rotor shaft in case of power failure or emergency situations. This preliminary safety mechanism is built into the design to counteract the increased dynamic forces that occur during high-speed operation, providing automatic protection without requiring external intervention.
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 compact, light, and reliable joint assembly that minimizes dynamic forces, enhances precision, and ensures safety by reducing torque and inertia, allowing robots to interact safely with humans while maintaining high-speed operation.
Implementation Method 1
a rotor brake configured to stop/prevent relative movement between the rotor shaft and the flexspline
Implementation Method 2
a strain wave gearing system comprising: a wave generator, a flexspline, and a circular spline connected to the output part, wherein the wave generator is rotated by a rotor shaft
Implementation Method 3
the rotor shaft being driven by an electric motor comprising a stator and a rotor magnet, the rotor magnet being affixed to the rotor shaft
Implementation Method 4
sensors arranged to measure the position of the rotor shaft in relation to the output part
Data Source
AI summary
A joint assembly for a robot, comprising a housing connected with an output part. The housing comprising a housing wall and a strain wave gearing system. The strain wave gearing system comprising a wave generator, a flexspline, and a circular spline connected to the output part. The wave generator is rotated by a rotor shaft. The rotor shaft is driven by an electric motor comprising a rotor magnet and a stator. The rotor magnet being affixed to the rotor shaft. The joint assembly further comprises one or more sensors comprising one or more magnetic field sensors and one or more pole rings arranged to measure a position of the output part in relation to the housing.