Robotic Joint Flow-Field Control for Safe Human Guidance
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Solution Overview
Problem
Conventional robotic systems used in cooperative physical interactions with humans store energy as potential energy due to discrepancies in motion, leading to sudden movements that can be harmful to the human collaborator, as they return to a desired position or configuration without proper control.
Innovation Solution
A control method that simulates a viscous fluid flow field to influence limb movement, avoiding potential energy storage by using a flow controller that applies a total control vector based on error velocity vectors and drag coefficients, ensuring the robotic system provides movement assistance and guidance without storing energy related to positional errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional robotic systems use restoring control action to return to desired position, then positioning accuracy is improved, but potential energy is stored and released suddenly causing harmful movements
Solution Approach 1:
The patent replaces the conventional mechanical spring-like restoring force with a viscous fluid damping mechanism. Instead of storing and releasing potential energy through elastic elements, the system uses a flow controller that generates control forces proportional to velocity error, mimicking viscous damping. This substitution eliminates the hazardous energy storage while maintaining positioning capability through continuous dissipation of kinetic energy.
Solution Approach 2:
The patent changes the fundamental parameter of the control force from position-dependent (conventional spring force) to velocity-dependent (viscous drag force). By defining the control force as proportional to the velocity error rather than position error, the system achieves positioning accuracy without storing potential energy, thereby preventing sudden harmful movements during position corrections.
2Speed
If conventional systems store potential energy for position correction, then control responsiveness is improved, but safety is worsened due to energy release to human collaborator
Solution Approach 1:
The patent substitutes the energy storage mechanism with an energy dissipation mechanism. Instead of using springs or elastic elements that store potential energy for rapid release, the system employs a flow controller that continuously dissipates energy through viscous damping. This ensures that no hazardous energy is stored in the control system, making it safe for human collaboration while maintaining responsiveness through velocity-based feedback.
Solution Approach 2:
The patent converts the potentially harmful effect of energy storage into a beneficial continuous energy dissipation process. By using velocity-proportional control forces, the system naturally dissipates kinetic energy during motion corrections rather than storing it, transforming what would be a hazard (sudden energy release) into a safety feature (continuous energy dissipation).
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
This approach reduces the risk of sudden movements by providing a more forgiving control mechanism that allows for precise human agency over movement, offering assistance and guidance while allowing deviations from the predetermined path, thus enhancing safety and usability in robotic interactions.
Implementation Method 1
The total control vector is determined based on a product of the drag coefficient and the error velocity vector
Data Source
AI summary
An exemplary robotic system includes a plurality of controllable joints and a controller. An exemplary control method provides for controlling the controllable joints by the controller. The control method provides for determining a configuration space for the robotic system and determining a reference movement path within the configuration space. The control method then provides for assigning a plurality of streamlines in the configuration space to yield a flow field based on the reference movement path. The control method then provides for measuring actual velocity vectors of the robotic system in the configuration space. The control method then provides for determining an error velocity vector based on a difference between the actual velocity vector and the desired velocity vector given by the flow field corresponding to the current robot configuration. The control method then provides for applying a total control vector at the plurality of controllable joints, by the controller, based on the error velocity vector.