Myoelectric Interface Multi-Directional Impedance Control
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Solution Overview
Problem
Conventional myoelectric interfaces struggle to provide reliable simultaneous control of motion, limiting their ability to extend beyond a single degree-of-freedom and failing to replicate the multi-directional impedance control necessary for natural human-robot interaction in uncertain environments.
Innovation Solution
A novel multi-directional impedance control scheme that uses surface electromyography (sEMG) inputs from upper limb muscles to simultaneously control the stiffness and set-point of 3-DOF systems, allowing users to stabilize movement in the presence of external forces, with an algorithm that maps sEMG signals to directional and non-directional stiffness outputs, enabling intuitive control without retraining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional myoelectric interfaces are used for single-DOF control, then reliability is maintained, but the system cannot provide simultaneous multi-directional control of motion and impedance
Solution Approach 1:
The patent segments the control task by separating position control and impedance control into distinct control loops. Position control manages the mean position of the robotic device, while impedance control manages the stiffness and damping characteristics. This segmentation allows each controller to operate independently with its own sEMG input processing, preventing signal conflicts and maintaining reliability while enabling multi-DOF simultaneous control.
Solution Approach 2:
The patent extends control from single-DOF to multi-DOF by adding dimensional capacity. Multiple sEMG channels are mapped to multiple degrees of freedom, with each DOF having its own position and impedance control parameters. This dimensional expansion allows simultaneous control of position and stiffness across multiple joints without interfering with each other, resolving the contradiction between versatility and reliability.
2Ease of operation
If sEMG signals are used for impedance control, then natural human-robot interaction is achieved, but transient changes in sEMG make simultaneous motion control unreliable
Solution Approach 1:
The patent segments sEMG signal processing by creating separate processing pipelines for position control and impedance control. Each pipeline applies appropriate filtering and thresholding strategies tailored to its specific control objectives. Position control uses sEMG signals to determine movement direction and speed, while impedance control uses separate processed signals to determine stiffness levels. This segmentation maintains intuitive control while improving reliability by preventing signal transient issues from affecting both control dimensions simultaneously.
Solution Approach 2:
The patent introduces intermediary processing layers between raw sEMG signals and control outputs. These intermediaries include signal filtering, rectification, and threshold detection circuits that condition the sEMG signals before they reach the position and impedance controllers. This intermediary processing stabilizes the signals and removes transient artifacts, enabling reliable simultaneous control while preserving the natural intuitive mapping between muscle activity and device behavior.
3Adaptability or versatility
If multi-directional impedance control is implemented, then natural interaction in unstable environments is achieved, but device complexity increases
Solution Approach 1:
The patent implements a universal control architecture where the same basic controller structure serves multiple functions. Each degree of freedom uses identical position and impedance control modules that can be activated independently. This modular universal design allows the system to adapt to different environmental requirements and task demands without requiring fundamentally different control mechanisms, managing complexity through reuse of proven control algorithms across multiple axes and control dimensions.
Solution Approach 2:
The patent makes the control system dynamically adjustable by allowing real-time modification of impedance parameters (stiffness and damping) and position setpoints based on task requirements and environmental conditions. The system can transition between different operational modes by adjusting control parameters while maintaining the same underlying control architecture. This dynamic adaptability provides environmental versatility without requiring complex hardware changes, as the same system reconfigures itself through parameter adjustment.
Data Source
AI summary
Systems and methods for simultaneous position and impedance control for myoelectric interfaces are disclosed herein. Properties such as control refinement, retention, generalization, and transfer allow users to learn simultaneous and proportional motion simply by interacting with a myoelectric interface, regardless of its initial intuitiveness. The presently disclosed technology expands on these motor learning approaches by implementing a multidirectional impedance controller in this framework. Using sEMG inputs from upper limb muscles, users simultaneously control both the stiffness and set-point of 3-DOFs. Users stabilize control in the presence of external forces in an analogous way to natural limb movements. Despite having no haptic feedback, subjects learn to tune the stiffness of the object being controlled to stabilize movement along desired paths.