Robotic Arm Joint Control Near Singularities and Collision Constraints
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Solution Overview
Problem
Conventional robotic manipulator control systems face challenges in solving the inverse kinematics problem, particularly when encountering singular configurations and potential collisions, leading to undesirable arm movements and collisions with objects or personnel.
Innovation Solution
A control system that utilizes joint sensors and a control unit to detect constraint criteria, adjusting joint movements to avoid undesirable configurations by applying adjustment signals based on threshold ranges and gain factors, optimizing arm movement to prevent collisions and singularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inverse kinematics control is used to position the end effector, then the end effector can reach desired positions, but the robot arm may encounter singular configurations or collide with objects/personnel
Solution Approach 1:
The control system performs preliminary detection of constraint criteria (singularities and collision risks) before executing the positioning command. By evaluating joint states against predefined constraint thresholds in advance, the system identifies unsafe configurations beforehand and adjusts the motion plan to avoid them, ensuring reliable operation while maintaining positioning accuracy
Solution Approach 2:
The system continuously monitors joint states through joint sensors and provides feedback to the control unit. This real-time feedback enables dynamic adjustment of motion commands based on detected constraint criteria, allowing the robot to adapt its trajectory to avoid singularities and collisions while achieving the desired end effector position
2Productivity
If the robot arm moves quickly to reach target positions, then productivity increases, but the risk of encountering singularities and collisions increases
Solution Approach 1:
Before executing high-speed movement commands, the control system preliminarily evaluates the proposed trajectory against constraint criteria including singularity detection and collision risk assessment. This preliminary check ensures that fast movements are only executed when safe, maintaining productivity while preventing harmful collisions
Solution Approach 2:
The system dynamically adjusts motion parameters based on real-time detection of joint states and constraint criteria. When approaching constrained regions, the system automatically modifies velocity and acceleration profiles to safely navigate around singularities and potential collision zones, optimizing the balance between speed and safety
3Reliability
If the control system adds constraint detection and adjustment mechanisms, then collision avoidance improves, but device complexity increases
Solution Approach 1:
The control unit performs multiple functions including position control, constraint detection, and motion adjustment using a unified control architecture. By integrating these functions into a single control system rather than adding separate dedicated systems, the patent improves safety while minimizing the increase in device complexity
Solution Approach 2:
The control system uses the existing joint sensors and control infrastructure to detect constraint criteria and automatically adjust motions without requiring additional external monitoring systems. The system serves itself by utilizing its own sensing capabilities for safety monitoring, avoiding the need for complex external safety systems
Data Source
AI summary
A system comprising: a robot comprising an arm having an attachment and, for each of n joints, a driver and a joint sensor; and a control unit configured to: obtain a desired position of the attachment; for each of k<n joints, obtain a sensed joint state; compare the states to a set of criteria indicative of the arm moving from a first to a second configuration; the states matching the set of criteria, determine a magnitude of an adjustment signal configured to slow, halt or reverse movement of the arm towards the second configuration; using the desired position of the attachment and the states, determine a direction of the adjustment signal; for each of the n joints, obtain a sensed joint state; using the desired position of the attachment, the obtained n states and the adjustment signal, determine signals for controlling the drivers; and drive the joints using the signals.