Power-Assist Robot Joint Restriction for Safe Operator Extraction
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Solution Overview
Problem
Existing power-assist robots lack the capability to ensure operator safety when they become jammed between the robot arm and an external structure, as they often cannot effectively move the operator out of a jammed state without compromising the external structure, due to limited movement ranges and restricted control strategies.
Innovation Solution
A power-assist robot system that includes a position information obtaining unit, a force detector, a jam determination unit, an area classification unit, and a restriction period setting unit, which allows the robot to restrict movement of its joints based on the location and duration of a jam, enabling safe operator extraction while minimizing impact on external structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the robot arm restricts movement of all joints during a jam, then the external structure is protected from damage, but the operator cannot be extracted from the jammed state
Solution Approach 1:
The control system segments the robot arm's joints into two categories: restricted joints (those that could cause damage to external structures) and unrestricted joints (those safe to move). During a jammed state, only the restricted joints are stopped while unrestricted joints continue to move, enabling operator extraction without compromising structural safety.
Solution Approach 2:
Different movement restriction policies are applied to different parts of the robot arm based on their local characteristics and potential impact. Joints closer to the end effector that could damage external structures are restricted, while base joints or those with sufficient clearance are allowed to move freely during operator extraction.
2Ease of operation
If the robot arm allows continuous movement during a jam, then the operator can be extracted quickly, but the external structure may be damaged
Solution Approach 1:
The control system divides joints into restricted and unrestricted groups, allowing unrestricted joints to move continuously during jammed states for rapid operator extraction, while restricted joints remain stopped to prevent structural damage.
Solution Approach 2:
The movement restriction policy dynamically adapts based on the operational context. During normal operation, all joints are controlled within safety limits. During detected jammed states, the system transitions to a selective restriction mode where only necessary joints are constrained, optimizing both safety and extraction efficiency.
3Reliability
If the robot imposes movement restriction on all joints during a jam, then safety is improved, but the productivity decreases due to extended restriction period
Solution Approach 1:
By segmenting joints into restricted and unrestricted categories, the system maintains operator safety through selective restriction rather than complete immobilization. This allows partial operation continuity during jammed states, reducing productivity loss while ensuring safety.
Solution Approach 2:
Instead of applying full movement restriction to all joints, the system applies partial restriction only to necessary joints. This excessive safety measure is calibrated to be just sufficient for protection, avoiding unnecessary complete shutdown and minimizing productivity impact.
4Productivity
If the robot removes movement restriction immediately after jam detection, then productivity is improved, but operator safety is compromised
Solution Approach 1:
The control system establishes predetermined restriction periods before fully removing restrictions. During this preliminary phase, restricted joints gradually resume movement while monitoring for recurring jams, ensuring operator safety is maintained during the transition back to full operation.
Solution Approach 2:
The system continuously monitors the jammed state and operator position during the restriction period. Based on feedback from sensors detecting operator movement and jam conditions, the control system intelligently adjusts the restriction duration and intensity, removing restrictions only when safety conditions are confirmed.
Data Source
AI summary
A robot determines whether or not an operator or an object is jammed between a robot arm and an external structure, classifies an area in which an end portion of the robot arm moves into a restricted area and an unrestricted area, and sets a restriction period. If a period after detection of the jam is in the restriction period and the end portion is in the restricted area, restriction on movement is imposed on one or more joints of the robot arm. The restriction on movement is a stoppage of movement of one or more joints. If the period after detection of the jam is after the restriction period, the restriction on movement is removed. If the period after detection of the jam is in the restriction period and the end portion is in the unrestricted area, the restriction on movement is not imposed on the joints.