Force-Controlled Robot Saturation Limit for Safe Workspace Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dexterous robots operating in unstructured workspaces with human operators or unpredictable objects face challenges in controlling forces to prevent unintended contact and ensuring safe operation, as existing systems lack effective methods to manage unexpected interactions without compromising task execution.
Innovation Solution
Implementing a control strategy that automatically imposes a saturation limit on static forces applied by robotic manipulators, combined with a dynamic reflex phase to manage inertial impacts, using proprioceptive and exteroceptive sensing to detect and respond to contact forces, ensuring safe operation without requiring continuous contact detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the robotic manipulator operates with high speed and momentum to improve productivity, then task execution efficiency is improved, but the risk of harmful impact increases when unexpected contact occurs
Solution Approach 1:
The control system preemptively applies a saturation limit to the static force component of the manipulator, creating a safety buffer before contact occurs. This ensures that even at high speeds, the static force cannot exceed a safe threshold, cushioning against potential harmful impacts while maintaining dynamic performance for task execution
Solution Approach 2:
The system dynamically adjusts the force control by distinguishing between static and dynamic components. The saturation limit applies only to static force, allowing dynamic forces from momentum to remain high for productivity while static forces are bounded for safety. This dynamic differentiation resolves the contradiction between speed and safety
2Adaptability or versatility
If the robotic manipulator uses force- or impedance-based control to improve adaptability in unstructured workspaces, then versatility in handling unpredictable objects is improved, but the ability to ensure safe operation deteriorates due to lack of continuous contact detection
Solution Approach 1:
The control system uses proprioceptive sensing from the manipulator's own actuators and sensors to self-monitor its static force output. The saturation limit mechanism automatically activates when force thresholds are approached, enabling the system to ensure its own safety without requiring external contact detection systems or continuous monitoring of the environment
Solution Approach 2:
The saturation limit acts as an intermediary control layer between the high-level task planning and the low-level force control. It mediates between the need for adaptability in unstructured environments and the requirement for safe operation by automatically bounding forces based on proprioceptive feedback, without requiring direct contact detection
3Object-affected harmful factors
If the robotic manipulator reduces mass and top speed to reduce inertial impact, then safety during unexpected contact is improved, but task execution capability and productivity deteriorate
Solution Approach 1:
The system changes the control parameter from physical mass reduction to virtual force limiting through saturation. Instead of reducing the manipulator's mass and speed (which would harm productivity), the control system adjusts the force parameter by applying a saturation limit to static force, achieving safety without compromising the physical capabilities needed for task execution
Data Source
AI summary
A method of controlling a robotic manipulator of a force- or impedance-controlled robot within an unstructured workspace includes imposing a saturation limit on a static force applied by the manipulator to its surrounding environment, and may include determining a contact force between the manipulator and an object in the unstructured workspace, and executing a dynamic reflex when the contact force exceeds a threshold to thereby alleviate an inertial impulse not addressed by the saturation limited static force. The method may include calculating a required reflex torque to be imparted by a joint actuator to a robotic joint. A robotic system includes a robotic manipulator having an unstructured workspace and a controller that is electrically connected to the manipulator, and which controls the manipulator using force- or impedance-based commands. The controller, which is also disclosed herein, automatically imposes the saturation limit and may execute the dynamic reflex noted above.