Robot Arm Force Control for Safe Object Transport
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Solution Overview
Problem
Existing robot systems face challenges in safely transporting objects with unknown or changing weights, particularly when another object is located below, as they tend to press objects together, causing damage and excessive load on the robot arm.
Innovation Solution
A robot system equipped with a robot arm, hand, driving unit, force detection unit, angle detection unit, and control unit that adjusts the hand angle and exerts a predetermined force in the vertical direction based on detected force and angle information, allowing cooperative transport with a person without pressing objects together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the robot arm is shifted upward and downward to horizontally maintain an object regardless of force exerted, then the object can be transported in any horizontal state, but the robot arm presses objects onto each other causing damage and excessive load
Solution Approach 1:
The robot arm transitions from rigid positional control to dynamic force control, allowing it to adapt its behavior based on real-time force feedback. The control unit switches between position control mode (for general movement) and force control mode (for delicate operations near other objects), enabling the system to be both versatile and safe.
Solution Approach 2:
A force sensor is integrated into the robot arm to detect forces exerted during object transport. The control unit continuously monitors this force feedback and adjusts the robot arm's movement accordingly, preventing excessive force application that could damage objects or cause excessive load.
2Ease of operation
If the robot arm maintains horizontal object position regardless of force, then cooperative transport is achieved, but safety is compromised when another object is located below
Solution Approach 1:
The force sensor provides real-time feedback about contact forces during cooperative transport. When the robot arm approaches another object or detects excessive force, the control unit receives this feedback and adjusts the control strategy to prevent safety issues, maintaining both ease of operation and reliability.
Solution Approach 2:
The system proactively prevents safety issues by monitoring force levels before damage occurs. The control unit detects approaching unsafe force levels through the force sensor and takes corrective action by adjusting the robot arm's movement, preventing the harmful effect rather than responding after damage occurs.
3Adaptability or versatility
If the robot arm transports objects with unknown or changing weights, then versatile transport is achieved, but excessive load and object damage occur
Solution Approach 1:
The force sensor continuously measures the actual force required to transport the object, providing real-time feedback to the control unit. This feedback mechanism allows the robot arm to automatically adapt to unknown or changing weights, applying only the necessary force and preventing excessive load on the robot arm while maintaining versatile transport capability.
Data Source
AI summary
Based upon a force in a vertical direction exerted between an object and a hand and an angle made by the hand relative to a horizontal face, a transporting force estimation unit estimates a transporting force applied in the vertical direction by a person, and based upon the estimated force, a force controlling operation is carried out so as to set a force in the vertical direction of the robot arm of a robot system to a predetermined force.