Variable Stiffness Robot Joint via Electromagnetic Actuation
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Solution Overview
Problem
Existing robot manipulator joint stiffness solutions, such as mechanical springs and force sensors, face limitations in variability and efficiency, with mechanical systems requiring additional mechanisms for stiffness control and electrical systems being prone to breakdowns.
Innovation Solution
A stiffness generating device using magnetic forces, comprising a rotating shaft, a rotor with magnetic elements, and a stator connected to a drive motor, with electromagnets or permanent magnets arranged to provide variable stiffness through current regulation, allowing for rapid control of stiffness without additional mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical spring is used to provide stiffness, then the joint has determined spring constant and functions like rotation springs, but the stiffness cannot be controlled or varied according to operation
Solution Approach 1:
The patent replaces the mechanical spring system with an electromagnetic system. Electromagnets are used to generate magnetic forces that provide stiffness to the robot joint, eliminating the need for physical springs while enabling variable stiffness control through electrical current regulation.
Solution Approach 2:
The patent changes the stiffness parameter dynamically by adjusting the current applied to the electromagnets. By varying the electrical parameter (current), the magnetic force and consequently the stiffness of the joint can be continuously adjusted according to operational requirements.
2Adaptability or versatility
If a separate drive mechanism is used to adjust plate spring length, then variable stiffness is possible according to each state, but additional mechanism must be driven for its operation
Solution Approach 1:
The patent eliminates the separate mechanical drive mechanism by using electromagnets directly mounted on the stator. The electromagnetic field replaces the mechanical adjustment mechanism, allowing stiffness variation without additional moving parts or separate drive systems.
Solution Approach 2:
The patent merges the stiffness control function with the existing motor structure by integrating electromagnets into the stator. This combination eliminates the need for separate stiffness adjustment mechanisms while maintaining variable stiffness capability.
3Device complexity
If force sensors and controllers are used to show virtual spring effect, then stiffness is controlled without separate mechanism, but efficiency and performance are low since position control and force control are carried out by a single controller
Solution Approach 1:
The patent replaces the software-based virtual spring control with a physical electromagnetic stiffness generation system. This hardware-based approach provides more direct and efficient control compared to computational methods, improving response time and control efficiency.
4Device complexity
If virtual spring control is implemented through software, then no separate mechanism is needed, but there is no measure or remedy in case of electrical breakdown
Solution Approach 1:
The patent implements a hybrid approach where electromagnets provide physical stiffness support rather than relying solely on software control. This physical electromagnetic mechanism provides redundancy and reliability, ensuring the system maintains stiffness even during electrical or software failures.
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 device generates stiffness with a simpler constitution than prior art, enabling variable stiffness control through magnetic forces, enhancing efficiency and safety in robot manipulator operations by providing adjustable stiffness for both low-speed safety and high-speed operations.
Implementation Method 1
a plurality of electromagnets fixed to an inner periphery of the stator so as to be apart from the arms by a predetermined gap and to be opposed to each other about the rotating shaft, wherein each electromagnet has a core radially oriented with respect to the rotating shaft and a coil wound around the core
Implementation Method 2
a rotor fixed to the rotating shaft and having arms comprising a magnetic element
Data Source
AI summary
A device for generating and varying stiffness, which may be applied to a joint of a robot manipulator, the stiffness generating device having a rotating shaft connected to a driven member; a rotor fixed to the rotating shaft and having arms comprising a magnetic element; a stator disposed to surround the rotor outside the arms and being connected to a drive motor; electromagnets fixed to an inner periphery of the stator and being opposed to each other about the rotating shaft, each having a core and a coil wound around the core; and means for applying current to the coils. One half of the electromagnets has N-poles at their inward ends and the other half of the electromagnets has S-poles at their inward ends. Current regulating means regulates the current being applied to the coils.