Manipulator Subspace Control for Safe Human-Robot Contact
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Solution Overview
Problem
Current robots with movable parts, such as manipulators, face challenges in ensuring high functional safety when interacting with humans, particularly in controlling and regulating actuators in response to external forces and torques.
Innovation Solution
A robot system comprising a manipulator driven by actuators, with a unit to determine external forces and torques, and a control unit that regulates the actuators by defining and controlling a sub-space within the working space to enable flexible receding and reverting based on projections of these forces and torques, using predefined control commands and rules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the manipulator is controlled to recede along the projection of external force into sub-space T1, then the safety of human-robot interaction is improved, but the complexity of the control system increases due to sub-space decomposition and classification
Solution Approach 1:
The working space AR is segmented into two complementary sub-spaces: T1 (safe space) and TK1 (complementary space). This segmentation allows the control system to handle different spatial directions differently - allowing free movement in safe directions while restricting movement in potentially harmful directions, thereby improving safety without requiring complete restriction of all movements
Solution Approach 2:
The control approach transitions from scalar force control to vector-based projection control in multi-dimensional space. By projecting external forces onto different sub-spaces (T1 and TK1), the system can independently control manipulator behavior in different spatial dimensions, enabling nuanced safety control that responds differently to forces from different directions
2Measurement precision
If the manipulator is restricted to revert from sub-space T1 into complementary sub-space TK1 based on classified projections, then the safety control precision is improved, but the response time increases due to classification processing
Solution Approach 1:
The working space is pre-decomposed into complementary sub-spaces T1 and TK1 with defined boundaries and characteristics before any external force is applied. Control rules for reverting from T1 to TK1 are pre-established based on the classification of projections. This preliminary setup allows the system to quickly determine the appropriate response without performing complex real-time calculations, thus maintaining high precision while reducing response time
Data Source
AI summary
A robot including a manipulator driven by actuators, and configured to determine external forces and/or external torques acting upon the manipulator, the robot configured to: regulate the actuators for a sub-space T1 of a working space AR such that, upon application of an external force and/or external torque upon the manipulator, the manipulator recedes into T1, wherein following applies: T1⊆AR and T1≠AR, and AR specifies all permitted translations and/or rotations of the manipulator; and determine, for a space TK1 that is complementary to T1, a projection {right arrow over (P)}TK1 of the external force and/or external torque into TK1, wherein following applies: T1∩TK1={0}, TK1⊆AR, and T1∪TK1=AR, classify {right arrow over (P)}TK1 into one of several predefined classes with respect to amount and/or direction and/or time curve of {right arrow over (P)}TK1, store a command and/or rule for each predefined class, and regulate the actuators as a function of classification of {right arrow over (P)}TK1 based on respective command and/or rule.